Author(s) ID,Title,Year,DOI,Link,Abstract
"6701379896;7003922138;7006199823;7101632204;9939102400;7005213997;7102665209;7102620639;7101823091;7004343004;12809675900;6603275645;57208462871;6701385171;7401477391;6603715895;6506103893;7401595141;7005808242;6701618837;7103206141;7402064802;7003554208;7006735547;57081464900;57054407300;57208455668;57111001300;7005884486;7006003831;56744278700;7404210007;35514163500;8733579000;6508004743;6701631872;7103366892;7003802133;6602864692;8733579800;54382704000;55570248000;","GFDL's CM2 global coupled climate models. Part I: Formulation and simulation characteristics",2006,"10.1175/JCLI3629.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33645219567&doi=10.1175%2fJCLI3629.1&partnerID=40&md5=e8eec3e3bd20e2a10e8d4e8fbba41979","The formulation and simulation characteristics of two new global coupled climate models developed at NOAA's Geophysical Fluid Dynamics Laboratory (GFDL) are described. The models were designed to simulate atmospheric and oceanic climate and variability from the diurnal time scale through multicentury climate change, given our computational constraints. In particular, an important goal was to use the same model for both experimental seasonal to interannual forecasting and the study of multicentury global climate change, and this goal has been achieved. Tw o versions of the coupled model are described, called CM2.0 and CM2.1. The versions differ primarily in the dynamical core used in the atmospheric component, along with the cloud tuning and some details of the land and ocean components. For both coupled models, the resolution of the land and atmospheric components is 2° latitude × 2.5° longitude; the atmospheric model has 24 vertical levels. The ocean resolution is 1° in latitude and longitude, with meridional resolution equatorward of 30° becoming progressively finer, such that the meridional resolution is 1/3° at the equator. There are 50 vertical levels in the ocean, with 22 evenly spaced levels within the top 220 m. The ocean component has poles over North America and Eurasia to avoid polar filtering. Neither coupled model employs flux adjustments. The co ntrol simulations have stable, realistic climates when integrated over multiple centuries. Both models have simulations of ENSO that are substantially improved relative to previous GFDL coupled models. The CM2.0 model has been further evaluated as an ENSO forecast model and has good skill (CM2.1 has not been evaluated as an ENSO forecast model). Generally reduced temperature and salinity biases exist in CM2.1 relative to CM2.0. These reductions are associated with 1) improved simulations of surface wind stress in CM2.1 and associated changes in oceanic gyre circulations; 2) changes in cloud tuning and the land model, both of which act to increase the net surface shortwave radiation in CM2.1, thereby reducing an overall cold bias present in CM2.0; and 3) a reduction of ocean lateral viscosity in the extratropics in CM2.1, which reduces sea ice biases in the North Atlantic. Both models have be en used to conduct a suite of climate change simulations for the 2007 Intergovernmental Panel on Climate Change (IPCC) assessment report and are able to simulate the main features of the observed warming of the twentieth century. The climate sensitivities of the CM2.0 and CM2.1 models are 2.9 and 3.4 K, respectively. These sensitivities are defined by coupling the atmospheric components of CM2.0 and CM2.1 to a slab ocean model and allowing the model to come into equilibrium with a doubling of atmospheric CO2. The output from a suite of integrations conducted with these models is freely available online (see http://nomads.gfdl.noaa.gov/). © 2006 American Meteorological Society."
"6602678829;7202670513;","A sequential ensemble Kalman filter for atmospheric data assimilation",2001,"10.1175/1520-0493(2001)129<0123:ASEKFF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035129828&doi=10.1175%2f1520-0493%282001%29129%3c0123%3aASEKFF%3e2.0.CO%3b2&partnerID=40&md5=2498d0e762ea573894d8bf2dcf49de3c","An ensemble Kalman filter may be considered for the 4D assimilation of atmospheric data. In this paper, an efficient implementation of the analysis step of the filter is proposed. It employs a Schur (elementwise) product of the covariances of the background error calculated from the ensemble and a correlation function having local support to filter the small (and noisy) background-error covariances associated with remote observations. To solve the Kalman filter equations, the observations are organized into batches that are assimilated sequentially. For each batch, a Cholesky decomposition method is used to solve the system of linear equations. The ensemble of background fields is updated at each step of the sequential algorithm and, as more and more batches of observations are assimilated, evolves to eventually become the ensemble of analysis fields. A prototype sequential filter has been developed. Experiments are performed with a simulated observational network consisting of 542 radiosonde and 615 satellite-thickness profiles. Experimental results indicate that the quality of the analysis is almost independent of the number of batches (except when the ensemble is very small). This supports the use of a sequential algorithm. A parallel version of the algorithm is described and used to assimilate over 100 000 observations into a pair of 50-member ensembles. Its operation count is proportional to the number of observations, the number of analysis grid points, and the number of ensemble members. In view of the flexibility of the sequential filter and its encouraging performance on a NEC SX-4 computer, an application with a primitive equations model can now be envisioned."
"35298445100;7409752891;7006920349;","An unstructured grid, finite-volume, three-dimensional, primitive equations ocean model: Application to coastal ocean and estuaries",2003,"10.1175/1520-0426(2003)020<0159:AUGFVT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042654349&doi=10.1175%2f1520-0426%282003%29020%3c0159%3aAUGFVT%3e2.0.CO%3b2&partnerID=40&md5=b5f48be5019d6f4e917431eb2084ee6c","An unstructured grid, finite-volume, three-dimensional (3D) primitive equation ocean model has been developed for the study of coastal oceanic and estuarine circulation. The model consists of momentum, continuity, temperature, salinity, and density equations and is closed physically and mathematically using the Mellor and Yamada level-2.5 turbulent closure submodel. The irregular bottom slope is represented using a σ-coordinate transformation, and the horizontal grids comprise unstructured triangular cells. The finite-volume method (FVM) used in this model combines the advantages of a finite-element method (FEM) for geometric flexibility and a finite-difference method (FDM) for simple discrete computation. Currents, temperature, and salinity in the model are computed in the integral form of the equations, which provides a better representation of the conservative laws for mass, momentum, and heat in the coastal region with complex geometry. The model was applied to the Bohai Sea, a semienclosed coastal ocean, and the Satilla River, a Georgia estuary characterized by numerous tidal creeks and inlets. Compared with the results obtained from the finite-difference model (ECOM-si), the new model produces a better simulation of tidal elevations and residual currents, especially around islands and tidal creeks. Given the same initial distribution of temperature in the Bohai Sea, the FVCOM and ECOM-si models show similar distributions of temperature and stratified tidal rectified flow in the interior region away from the coast and islands, but FVCOM appears to provide a better simulation of temperature and currents around the islands, barriers, and inlets with complex topography."
"26643588800;7201439545;24531084900;6506041382;7004069241;7404187480;57193921169;","A new dynamical core of the Met Office's global and regional modelling of the atmosphere",2005,"10.1256/qj.04.101","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24344490871&doi=10.1256%2fqj.04.101&partnerID=40&md5=87e80ef0a52c9b29484f4c50f9b1e64a","A computational scheme suitable for numerical weather prediction and climate modelling over a wide range of length scales is described. Its formulation is non-hydrostatic and fully compressible, and shallow atmosphere approximations are not made. Semi-implicit, semi-Lagrangian time-integration methods are used. The scheme forms the dynamical core of the unified model used at the Met Office for all its operational numerical weather prediction and in its climate studies. © Crown copyright, 2005."
"55885528600;25227989500;15828193000;10339477400;26031912400;7005806315;6602240885;6603853280;55597087360;36159440000;7003332823;22134074500;7004468723;54885459100;57194045072;6507118937;53865439800;6701840054;23012746800;15726660300;12242312400;23987220000;6507121903;7201571151;6506049562;7005501673;","The CNRM-CM5.1 global climate model: Description and basic evaluation",2013,"10.1007/s00382-011-1259-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876829330&doi=10.1007%2fs00382-011-1259-y&partnerID=40&md5=16c946322bafe32bcc1d6e8ae4b1a02e","A new version of the general circulation model CNRM-CM has been developed jointly by CNRM-GAME (Centre National de Recherches Météorologiques-Groupe d'études de l'Atmosphère Météorologique) and Cerfacs (Centre Européen de Recherche et de Formation Avancée) in order to contribute to phase 5 of the Coupled Model Intercomparison Project (CMIP5). The purpose of the study is to describe its main features and to provide a preliminary assessment of its mean climatology. CNRM-CM5. 1 includes the atmospheric model ARPEGE-Climat (v5. 2), the ocean model NEMO (v3. 2), the land surface scheme ISBA and the sea ice model GELATO (v5) coupled through the OASIS (v3) system. The main improvements since CMIP3 are the following. Horizontal resolution has been increased both in the atmosphere (from 2. 8° to 1. 4°) and in the ocean (from 2° to 1°). The dynamical core of the atmospheric component has been revised. A new radiation scheme has been introduced and the treatments of tropospheric and stratospheric aerosols have been improved. Particular care has been devoted to ensure mass/water conservation in the atmospheric component. The land surface scheme ISBA has been externalised from the atmospheric model through the SURFEX platform and includes new developments such as a parameterization of sub-grid hydrology, a new freezing scheme and a new bulk parameterisation for ocean surface fluxes. The ocean model is based on the state-of-the-art version of NEMO, which has greatly progressed since the OPA8. 0 version used in the CMIP3 version of CNRM-CM. Finally, the coupling between the different components through OASIS has also received a particular attention to avoid energy loss and spurious drifts. These developments generally lead to a more realistic representation of the mean recent climate and to a reduction of drifts in a preindustrial integration. The large-scale dynamics is generally improved both in the atmosphere and in the ocean, and the bias in mean surface temperature is clearly reduced. However, some flaws remain such as significant precipitation and radiative biases in many regions, or a pronounced drift in three dimensional salinity. © 2012 The Author(s)."
"7103271625;8733579800;6701618837;7103206141;7006306835;55286185400;6701752471;57208462871;57208455668;35514163500;7402093416;42961002600;7102665209;6701379896;6603396333;7401477391;6603715895;7005808242;6508244744;7402064802;7003554208;57081464900;57054407300;25823927100;6603779823;7005884486;7006003831;56244473600;7103033590;57205867148;6603173671;56744278700;6603171355;8733579000;6508004743;7103366892;7101632204;57199296506;7003802133;6602864692;54382704000;","The dynamical core, physical parameterizations, and basic simulation characteristics of the atmospheric component AM3 of the GFDL global coupled model CM3",2011,"10.1175/2011JCLI3955.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955044421&doi=10.1175%2f2011JCLI3955.1&partnerID=40&md5=67c12e311444a23337eabd4464ea18ec","The Geophysical Fluid Dynamics Laboratory (GFDL) has developed a coupled general circulation model (CM3) for the atmosphere, oceans, land, and sea ice. The goal of CM3 is to address emerging issues in climate change, including aerosol-cloud interactions, chemistry-climate interactions, and coupling between the troposphere and stratosphere. The model is also designed to serve as the physical system component of earth system models and models for decadal prediction in the near-term future-for example, through improved simulations in tropical land precipitation relative to earlier-generation GFDL models. This paper describes the dynamical core, physical parameterizations, and basic simulation characteristics of the atmospheric component (AM3) of this model. Relative to GFDL AM2, AM3 includes new treatments of deep and shallow cumulus convection, cloud droplet activation by aerosols, subgrid variability of stratiform vertical velocities for droplet activation, and atmospheric chemistry driven by emissions with advective, convective, and turbulent transport. AM3 employs a cubed-sphere implementation of a finite-volume dynamical core and is coupled to LM3, a new land model with ecosystem dynamics and hydrology. Its horizontal resolution is approximately 200 km, and its vertical resolution ranges approximately from 70 m near the earth's surface to 1 to 1.5 km near the tropopause and 3 to 4 km in much of the stratosphere. Most basic circulation features in AM3 are simulated as realistically, or more so, as in AM2. In particular, dry biases have been reduced over South America. In coupled mode, the simulation of Arctic sea ice concentration has improved. AM3 aerosol optical depths, scattering properties, and surface clear-sky downward shortwave radiation are more realistic than in AM2. The simulation of marine stratocumulus decks remains problematic, as in AM2. The most intense 0.2% of precipitation rates occur less frequently in AM3 than observed. The last two decades of the twentieth century warm in CM3 by 0.328C relative to 1881-1920. The Climate Research Unit (CRU) and Goddard Institute for Space Studies analyses of observations show warming of 0.568 and 0.528C, respectively, over this period. CM3 includes anthropogenic cooling by aerosol-cloud interactions, and its warming by the late twentieth century is somewhat less realistic than in CM2.1, which warmed 0.668C but did not include aerosol-cloud interactions. The improved simulation of the direct aerosol effect (apparent in surface clear-sky downward radiation) in CM3 evidently acts in concert with its simulation of cloud-aerosol interactions to limit greenhouse gas warming. © 2011 American Meteorological Society."
"7004258980;23099743300;6603183022;7005132811;8728999700;","The Max-Planck-Institute global ocean/sea ice model with orthogonal curvilinear coordinates",2002,"10.1016/S1463-5003(02)00015-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037064630&doi=10.1016%2fS1463-5003%2802%2900015-X&partnerID=40&md5=5289417a4b04f409c5d8d327b00f71fe","The Hamburg Ocean Primitive Equation model has undergone significant development in recent years. Most notable is the treatment of horizontal discretisation which has undergone transition from a staggered E-grid to an orthogonal curvilinear C-grid. The treatment of subgridscale mixing has been improved by the inclusion of a new formulation of bottom boundary layer (BBL) slope convection, an isopycnal diffusion scheme, and a Gent and McWilliams style eddy-induced mixing parameterisation. The model setup described here has a north pole over Greenland and a south pole on the coast of the Weddell Sea. This gives relatively high resolution in the sinking regions associated with the thermohaline circulation. Results are presented from a 450 year climatologically forced integration. The forcing is a product of the German Ocean Model Intercomparison Project and is derived from the European Centre for Medium Range Weather Forecasting reanalysis. The main emphasis is on the model's representation of key quantities that are easily associated with the ocean's role in the global climate system. The global and Atlantic northward poleward heat transports have peaks of 1.43 and 0.84 PW, at and N respectively. The Atlantic meridional overturning streamfunction has a peak of 15.7 Sv in the North Atlantic and an outflow of 11.9 Sv at S. Comparison with a simulation excluding BBL shows that the scheme is responsible for up to a 25% increase in North Atlantic heat transport, with significant improvement of the depths of convection in the Greenland, Labrador and Irminger Seas. Despite the improvements, comparison with observations shows the heat transport still to be too weak. Other outstanding problems include an incorrect Gulf Stream pathway, a too strong Antarctic Circumpolar Current, and a too weak renewal of Antarctic Intermediate Water. Nevertheless, the model has been coupled to the atmospheric GCM ECHAM5 and run successfully for over 250 years without any surface flux corrections. © 2002 Elsevier Science Ltd. All rights reserved."
"7005808242;35497573900;","A proposal for the intercomparison of the dynamical cores of atmospheric general circulation models",1994,"10.1175/1520-0477(1994)075<1825:APFTIO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028669607&doi=10.1175%2f1520-0477%281994%29075%3c1825%3aAPFTIO%3e2.0.CO%3b2&partnerID=40&md5=d4abb420617d33370711ce87cde91144","A benchmark calculation is proposed for evaluating the dynamical cores of atmospheric general circulation models independently of the physical parameterizations. The test focuses on the long-term statistical properties of a fully developed general circulation; thus, it is particularly appropriate for intercomparing the dynamics used in climate models. To illustrate the use of this benchmark, two very different atmospheric dynamical cores - one spectral, one finite difference - are compared. It is found that the long-term statistics produced by the two models are very similar. Selected results from these calculations are presented to initiate the intercomparison. -Authors"
"57218978870;9939102400;7003922138;7102665209;6701379896;7102620639;7103271625;7004343004;6603396333;7103242280;6506103893;7401477391;7005808242;6701618837;7103206141;7402064802;7003554208;7006735547;16637634600;7005350396;8733578200;7005884486;7006003831;7103033590;6603173671;56744278700;35514163500;8733579000;6508004743;7003543851;7103366892;55419119900;57199296506;6602864692;8733579800;","The new GFDL global atmosphere and land model AM2-LM2: Evaluation with prescribed SST simulations",2004,"10.1175/JCLI-3223.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-19944434306&doi=10.1175%2fJCLI-3223.1&partnerID=40&md5=bec7e20dbfff91e14f99f8c8e19974fd","The configuration and performance of a new global atmosphere and land model for climate research developed at the Geophysical Fluid Dynamics Laboratory (GFDL) are presented. The atmosphere model, known as AM2, includes a new gridpoint dynamical core, a prognostic cloud scheme, and a multispecies aerosol climatology, as well as components from previous models used at GFDL. The land model, known as LM2, includes soil sensible and latent heat storage, groundwater storage, and stomatal resistance. The performance of the coupled model AM2-LM2 is evaluated with a series of prescribed sea surface temperature (SST) simulations. Particular focus is given to the model's climatology and the characteristics of interannual variability related to El Niño-Southern Oscillation (ENSO). One AM2-LM2 integration was perfor med according to the prescriptions of the second Atmospheric Model Intercomparison Project (AMIP II) and data were submitted to the Program for Climate Model Diagnosis and Intercomparison (PCMDI). Particular strengths of AM2-LM2, as judged by comparison to other models participating in AMIP II, include its circulation and distributions of precipitation. Prominent problems of AM2-LM2 include a cold bias to surface and tropospheric temperatures, weak tropical cyclone activity, and weak tropical intraseasonal activity associated with the Madden-Julian oscillation. An ensemble of 10 AM2-LM 2 integrations with observed SSTs for the second half of the twentieth century permits a statistically reliable assessment of the model's response to ENSO. In general, AM2-LM2 produces a realistic simulation of the anomalies in tropical precipitation and extratropical circulation that are associated with ENSO. © 2004 American Meteorological Society."
"35566896300;55924208000;","The singular-vector structure of the atmospheric global circulation",1995,"10.1175/1520-0469(1995)052<1434:TSVSOT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029412335&doi=10.1175%2f1520-0469%281995%29052%3c1434%3aTSVSOT%3e2.0.CO%3b2&partnerID=40&md5=914c7eda0e4bf5b55058e3940d7cabea","The local phase-space instability of the atmospheric global circulation is characterized by its (nonmodal) singular vectors. The formulation of singular vector analysis is described. The relations between singular vectors, normal modes, adjoint modes, Lyapunov vectors, perturbations produced by the so-called breeding method, and wave psuedomomentum are outlined. Techniques to estimate the dominant part of the singular spectrum using large-dimensional primitive equation models are discussed. Results are described, based first on statistics of routine calculations made between December 1992 and August 1993, and second on three specific case studies. -from Authors"
"35974590700;7101630970;","Subtropical anticyclones and summer monsoons",2001,"10.1175/1520-0442(2001)014<3192:SAASM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035428678&doi=10.1175%2f1520-0442%282001%29014%3c3192%3aSAASM%3e2.0.CO%3b2&partnerID=40&md5=f4652e35e4c70523ba06293aeadcd66a","The summer subtropical circulation in the lower troposphere is characterized by continental monsoon rains and anticyclones over the oceans. In winter, the subtropical circulation is more strongly dominated by the zonally averaged flow and its interactions with orography. Here, the mechanics of the summer and winter lower-tropospheric subtropical circulation are explored through the use of a primitive equation model and comparison with observations. By prescribing in the model the heatings associated with several of the world's monsoons, it is confirmed that the equator ward portion of each subtropical anticyclone may be viewed as the Kelvin wave response to the monsoon heating over the continent to the west. A poleward-flowing low-level jet into a monsoon (such as the Great Plains jet) is required for Sverdrup vorticity balance. This jet effectively closes off the subtropical anticyclone to the east and also transports moisture into the monsoon region. The low-level jet into North America induced by its monsoon heating is augmented by a remote response to the Asian monsoon heating. The Rossby wave response to the west of subtropical monsoon heating, interacting with the midlatitude westerlies, produces a region of adiabatic descent. It is demonstrated here that a local ""diabatic enhancement"" can lead to a strengthening of the descent. Longitudinal mountain chains act to block the westerly flow and also tend to produce descent in this region. Below the descent. Sverdrup vorticity balance implies equatorward flow that closes off the subtropical anticyclone to the west and induces cool upwelling in the ocean through Ekman transport. Feedbacks, involving, for example, sea surface temperatures, may further enhance the descent in these regions. The conclusion is that the Mediterranean-type climates of regions such as California and Chile may be induced remotely by the monsoon to the east. Hence it can be argued that the subtropical circulation in summer comprises a set of weakly interacting monsoon systems, each involving monsoon rains, a low-level poleward jet, a subtropical anticyclone to the east, and descent and equatorward flow to the west. In winter, it is demonstrated how the nonlinear interaction between the strong zonal-mean circulation, associated with the winter ""Hadley cell,"" and the mountains can define many of the large-scale features of the subtropical circulation. The blocking effect of the longitudinal mountain chains is shown to be very important. Subsequent diabatic effects, such as a local diabatic enhancement, would appear to be essential for producing the observed amplitude of these features."
"7003561280;35497573900;","Vacillations in a coupled ocean-atmosphere model",1988,"10.1175/1520-0469(1988)045<0549:VIACOM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024223797&doi=10.1175%2f1520-0469%281988%29045%3c0549%3aVIACOM%3e2.0.CO%3b2&partnerID=40&md5=cdeba6bd85d06091c5b496ff56c7ad59","Both ocean and atmosphere are two-level, nonlinear primitive equations models. The global atmospheric model is forced by a steady, zonally symmetric Newtonian heating. The ocean model is solved in a rectangular tropical basin. Heat fluxes between ocean and atmosphere are linear in air-sea temperature differences, and the interfacial stress is proportional to lower-level atmospheric winds. The coupled models produce ENSO-like variability on time scales of 3 to 5 years. Since there is no external time-dependent forcing, these are self-sustained vacillations on the nonlinear system. It is argued that the energetics of the vacillations is that of unstable coupled modes and that the time scale is crucially dependent on the effects of ocean waves propagating in a closed basin. -from Authors"
"7102696626;12761052200;55717244800;13406399300;57202891769;7006705919;55745955800;","The Mean Climate of the Community Atmosphere Model (CAM4) in Forced SST and Fully Coupled Experiments",2013,"10.1175/JCLI-D-12-00236.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874797242&doi=10.1175%2fJCLI-D-12-00236.1&partnerID=40&md5=b7c08680526e9b5d4dce6828cb0f00ed","The Community Atmosphere Model, version 4 (CAM4), was released as part of the Community Climate System Model, version 4 (CCSM4). The finite volume (FV) dynamical core is now the default because of its superior transport and conservation properties. Deep convection parameterization changes include a dilute plume calculation of convective available potential energy (CAPE) and the introduction of convective momentum transport (CMT). An additional cloud fraction calculation is now performed following macrophysical state updates to provide improved thermodynamic consistency. A freeze-drying modification is further made to the cloud fraction calculation in very dry environments (e.g., the Arctic), where cloud fraction and cloud water values were often inconsistent in CAM3. In CAM4 the FV dynamical core further degrades the excessive trade-wind simulation, but reduces zonal stress errors at higher latitudes. Plume dilution alleviates much of the midtropospheric tropical dry biases and reduces the persistent monsoon precipitation biases over the Arabian Peninsula and the southern Indian Ocean. CMT reduces much of the excessive tradewind biases in eastern ocean basins. CAM4 shows a global reduction in cloud fraction compared to CAM3, primarily as a result of the freeze-drying and improved cloud fraction equilibrium modifications. Regional climate feature improvements include the propagation of stationary waves from the Pacific into midlatitudes and the seasonal frequency of Northern Hemisphere blocking events. A 18 versus 28 horizontal resolution of the FV dynamical core exhibits superior improvements in regional climate features of precipitation and surface stress. Improvements in the fully coupled mean climate between CAM3 and CAM4 are also more substantial than in forced sea surface temperature (SST) simulations.©2013 American Meteorological Society."
"8623918800;7102101132;7404361000;","The role of ""vortical"" hot towers in the formation of tropical cyclone Diana (1984)",2004,"10.1175/1520-0469(2004)061<1209:TROVHT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042778358&doi=10.1175%2f1520-0469%282004%29061%3c1209%3aTROVHT%3e2.0.CO%3b2&partnerID=40&md5=3c52edebf3724d6dc2595484877816f4","A high-resolution (3-km horizontal grid spacing) near-cloud-resolving numerical simulation of the formation of Hurricane Diana (1984) is used to examine the contribution of deep convective processes to tropical cyclone formation. This study is focused on the 3-km horizontal grid spacing simulation because this simulation was previously found to furnish an accurate forecast of the later stages of the observed storm life cycle. The numerical simulation reveals the presence of vortical hot towers, or cores of deep cumulonimbus convection possessing strong vertical vorticity, that arise from buoyancy-induced stretching of local absolute vertical vorticity in a vorticity-rich prehurricane environment. At near-cloud-resolving scales, these vortical hot towers are the preferred mode of convection. They are demonstrated to be the most important influence to the formation of the tropical storm via a two-stage evolutionary process: (i) preconditioning of the local environment via diabatic production of multiple small-scale lower-tropospheric cyclonic potential vorticity (PV) anomalies, and (ii) multiple mergers and axisymmetrization of these low-level PV anomalies. The local warm-core formation and tangential momentum spinup are shown to be dominated by the organizational process of the diabatically generated PV anomalies; the former process being accomplished by the strong vertical vorticity in the hot tower cores, which effectively traps the latent heat from moist convection. In addition to the organizational process of the PV anomalies, the cyclogenesis is enhanced by the aggregate diabatic heating associated with the vortical hot towers, which produces a net influx of low-level mean angular momentum throughout the genesis. Simpler models are examined to elucidate the underlying dynamics of tropical cyclogenesis in this case study. Using the Sawyer-Eliassen balanced vortex model to diagnose the macroscale evolution, the cyclogenesis of Diana is demonstrated to proceed in approximate gradient and hydrostatic balance at many instances, where local radial and vertical accelerations are small. Using a shallow water primitive equation model, a characteristic ""moist"" (diabatic) vortex merger in the cloud-resolving numerical simulation is captured in a large part by the barotropic model. Since a moist merger results in a stronger vortex and occurs twice as fast as a dry merger, it is inferred (consistent with related work) that a net low-level convergence can accelerate and intensify the merger process in the real atmosphere. Although the findings reported herein are based on a sole case study and thus cannot yet be generalized, it is believed the results are sufficiently interesting to warrant further idealized simulations of this nature. © 2004 American Meteorological Society."
"7103248807;6507355747;35986800300;7404029779;56232430600;7006766881;7004764167;7404142321;7407104838;6602131529;56363371300;7004169476;6602665711;7103373205;35570389600;7103180783;7201921725;55451545500;57203049177;7006261583;6506592395;25030776200;13402835300;14623255000;13403080600;","The new Hadley Centre Climate Model (HadGEM1): Evaluation of coupled simulations",2006,"10.1175/JCLI3712.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646381345&doi=10.1175%2fJCLI3712.1&partnerID=40&md5=d8a7be02058c63ac6f2dd95da9dd3d67","A new coupled general circulation climate model developed at the Met Office's Hadley Centre is presented, and aspects of its performance in climate simulations run for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) documented with reference to previous models. The Hadley Centre Global Environmental Model version 1 (HadGEM1) is built around a new atmospheric dynamical core; uses higher resolution than the previous Hadley Centre model, HadCM3; and contains several improvements in its formulation including interactive atmospheric aerosols (sulphate, black carbon, biomass burning, and sea salt) plus their direct and indirect effects. The ocean component also has higher resolution and incorporates a sea ice component more advanced than HadCM3 in terms of both dynamics and thermodynamics. HadGEM1 thus permits experiments including some interactive processes not feasible with HadCM3. The simulation of present-day mean climate in HadGEM1 is significantly better overall in comparison to HadCM3, although some deficiencies exist in the simulation of tropical climate and El Niño variability. We quantify the overall improvement using a quasi-objective climate index encompassing a range of atmospheric, oceanic, and sea ice variables. It arises partly from higher resolution but also from greater fidelity in modeling dynamical and physical processes, for example, in the representation of clouds and sea ice. HadGEM1 has a similar effective climate sensitivity (2.8 K) to a CO2 doubling as HadCM3 (3.1 K), although there are significant regional differences in their response patterns, especially in the Tropics. HadGEM1 is anticipated to be used as the basis both for higher-resolution and higher-complexity Earth System studies in the near future."
"6603858877;7003727319;6603627827;7401551148;","Recent changes in deep water formation and spreading in the Eastern Mediterranean Sea: A review",1999,"10.1016/S0079-6611(99)00019-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032712365&doi=10.1016%2fS0079-6611%2899%2900019-1&partnerID=40&md5=64998991de6d0228eb35756e99916540","Observations of the last decade testify that the characteristics of the deep thermohaline circulation in the Eastern Mediterranean Sea have changed thoroughly. The source of the most dense waters of the basin has moved from the Adriatic to the Aegean Sea. This new source has proved to be very efficient since the estimated formation rate for the period 1989-95 was more than 1 Sv, about three times more than the dense water formation rate of the Adriatic Sea. These new waters with hydrological characteristics, that are warmer and more saline, have replaced almost 20% of the older deep waters of the basin, and have uplifted the deep isopycnals by about 500 m. This major event can be attributed to important meteorological anomalies in the Eastern Mediterranean and to changes of circulation patterns. The extended dry period of 1988-93 and the exceptionally cold winters of 1987 and 1992-93 created favorable conditions for increased formation of dense water in the Aegean. Furthermore, changes in the circulation patterns in the intermediate water range (Levantine Intermediate Water LIW and Cretan Intermediate Water), themselves possibly linked to meteorological anomalies, appear to have played an important role in the redistribution of salt. As a result of an interruption to exchanges between the Ionian and Levantine Basin, the salinities in the latter started to rise, high salinity waters were diverted into the Aegean [Malanotte-Rizzoli, P., Manca, B. B., Ribera dAcala, M., and Theocharis, A. (1998). The Eastern Mediterranean in the 80s and in the 90s: the big transition emerged from the POEM-BC observational evidence. Rapport du Commission International de la Mer Medittanee, 35, 174-175] and the westward transport of LIW was reduced. An additional effect of the deep water discharge from the Aegean and the resulting uplifting of mid-depth waters was to lower salinities in the LIW layer. This effect is most strongly felt in the Ionian Sea. A 3-D primitive equation numerical model for the Eastern Mediterranean with a 20 km grid size is used to simulate the observed changes and understand the basic mechanisms which caused them. Under appropriate atmospheric forcing the model successfully reproduces the main characteristics of the transient. These results indicate that the observed changes can be, at least partially, explained as a response of the Eastern Mediterranean, and more specifically of the Aegean, to atmospheric forcing variability."
"7409554002;7101630970;","The direct response to tropical heating in a baroclinic atmosphere",1995,"10.1175/1520-0469(1995)052<0307:tdrtth>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028883057&doi=10.1175%2f1520-0469%281995%29052%3c0307%3atdrtth%3e2.0.co%3b2&partnerID=40&md5=0ccab179e1ed5f2ebe09bbeda99112a3","The global response to tropical heating is studied by performing a time integration of a 15-level primitive equation model, starting with a basic flow maintained by a constant forcing. The Gill-type response is seen in the lower troposphere in all cases. In the upper troposphere, depending on the basic conditions, the simple tropical quadrupole response of the Gill model shows considerable modification. The anticyclonic pair can be centered over the heating and can vary substantially in magnitude and vertical extent. The Rossby wave source and the upper-tropospheric divergence above the heating region is always found, but the existence and relative magnitudes of local Hadley and Walker cells as measured by upper-tropospheric convergence are strong functions of the flow. -from Authors"
"6603715895;7004473824;","Biharmonic friction with a Smagorinsky-like viscosity for use in large-scale eddy-permitting ocean models",2000,"10.1175/1520-0493(2000)128<2935:bfwasl>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033787691&doi=10.1175%2f1520-0493%282000%29128%3c2935%3abfwasl%3e2.0.co%3b2&partnerID=40&md5=4f5f2be16fcbe6e20062ac41c4e5cb1b","This paper discusses a numerical closure, motivated from the ideas of Smagorinsky, for use with a biharmonic operator. The result is a highly scale-selective, state-dependent friction operator for use in eddy-permitting geophysical fluid models. This friction should prove most useful for large-scale ocean models in which there are multiple regimes of geostrophic turbulence. Examples are provided from primitive equation geopotential and isopycnal-coordinate ocean models."
"35894581100;","Atmospheric simulations using a GCM with simplified physical parametrizations. I: Model climatology and variability in multi-decadal experiments",2003,"10.1007/s00382-002-0268-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037273134&doi=10.1007%2fs00382-002-0268-2&partnerID=40&md5=41309f6f22069828d8ec71ee18b3b4d2","This work describes the formulation and climatology of an atmospheric general circulation model (GCM) of intermediate complexity, based on a spectral primitive-equation dynamical core and a set of simplified physical parametrization schemes. The parametrization package has been specially designed to work in models with just a few vertical levels, and is based on the same physical principles adopted in the schemes of state-of-the art GCMs. The parametrized processes include large-scale condensation, convection, clouds, short-wave and long-wave radiation, surface fluxes and vertical diffusion. In the current configuration, the model (nicknamed SPEEDY, from Simplified Parametrizations, primitivE-Equation DYnamics"") has five vertical levels and a spectral truncation at total wave number 30 (T30L5). The top vertical level (crudely) represents the stratosphere, the bottom one the planetary boundary layer. Computationally, SPEEDY requires (at least) one order of magnitude less CPU time than a state-of-the-art GCM at the same horizontal resolution, and is therefore suitable for studies of inter-decadal or inter-centennial variability. Statistics of the model mean state and variability are computed from an ensemble of 41-year simulations forced by observed sea-surface temperatures in the period 1952-1992. The model mean state is closer to the observed climatology during the (boreal) winter than during summer. In winter (i.e. December to February, DJF), the model underestimates the amplitude of the Northern Hemisphere stationary wave pattern, particularly in the European-Atlantic sector. Some aspects of the systematic error of SPEEDY are in fact typical of many GCMs, although the error amplitude is stronger than in state-of-the-art models. On the other hand, the global distribution of precipitation in DJF is quite realistic, and compares well with that of more complex GCMs. In summer (June to August), a strong negative bias in the mid-tropospheric temperature generates a Northern Hemisphere circulation with some springtime characteristics. In particular, the position of the Tropical Convergence Zone in the Indian Ocean remains too far south, leading to a deficient simulation of the monsoon circulation over South Asia. The simulated variability during the northern winter is reasonably realistic as far as the spatial distribution is concerned, although some underestimation in the intensity can be found, particularly in the low-frequency range and in the Atlantic sector. The atmospheric response to ENSO events is also weaker than observed, although the spatial patterns of the rainfall and geopotential response in the Pacific sector are in phase with their observed counterparts. In the Atlantic/Eurasian region, the spatial patterns associated with the interdecadal trends in the simulated and observed large-scale circulation show a clear positive correlation, consistent with the hypothesis of a positive ocean-atmosphere feedback on decadal time scales."
"57204253860;7006432091;8861633300;","The tropical dynamical response to latent heating estimates derived from the TRMM precipitation radar",2004,"10.1175/1520-0469(2004)061<1341:TTDRTL>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242688106&doi=10.1175%2f1520-0469%282004%29061%3c1341%3aTTDRTL%3e2.0.CO%3b2&partnerID=40&md5=bc1ce2c7c5b0f0bef8cec7ee3e157656","A 3-yr (1998-2000) climatology of near-surface rainfall and stratiform rain fraction observed by the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) was used to calculate the four-dimensional distribution of tropical latent heating on seasonal-to-annual time scales. The TRMM-derived latent heating was then used to force an idealized primitive equation model using an initial value approach in order to obtain the quasi-steady-state, nonlinear, zonally asymmetric atmospheric response to precipitating tropical cloud systems. In agreement with previous studies, an increase in stratiform rain fraction elevates circulation centers and strengthens the upper-level response. Furthermore, horizontal variations in the vertical heating profile implied by the PR stratiform rain fraction pattern lead to circulation anomalies of varying height and vertical extent that are not present when the model is forced with a vertically uniform heating field. During El Niño, the trans-Pacific gradient in stratiform rain fraction that is normally present becomes more pronounced and the model response becomes even more sensitive to the horizontal variability of the latent heating vertical structure. When the heating field is modified to take into account the effects of nonprecipitating cumulus and cloud radiative forcing within the regions of tropical precipitating cloud systems, the overall pattern of the model response to the TRMM-derived latent heating is reinforced, as is the model's sensitivity to the variability in the latent heating vertical structure. © 2004 American Meteorological Society."
"7202670513;6602678829;6505881635;","Ensemble size, balance, and model-error representation in an ensemble Kalman filter",2002,"10.1175/1520-0493(2002)130<2791:ESBAME>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036853557&doi=10.1175%2f1520-0493%282002%29130%3c2791%3aESBAME%3e2.0.CO%3b2&partnerID=40&md5=2606b027bc47892bd46f8f715968ac9c","The ensemble Kalman filter (EnKF) has been proposed for operational atmospheric data assimilation. Some outstanding issues relate to the required ensemble size, the impact of localization methods on balance, and the representation of model error. To investigate these issues, a sequential EnKF has been used to assimilate simulated radiosonde, satellite thickness, and aircraft reports into a dry, global, primitive-equation model. The model uses the simple forcing and dissipation proposed by Held and Suarez. It has 21 levels in the vertical, includes topography, and uses a 144 × 72 horizontal grid. In total, about 80 000 observations are assimilated per day. It is found that the use of severe localization in the EnKF causes substantial imbalance in the analyses. As the distance of imposed zero correlation increases to about 3000 km. the amount of imbalance becomes acceptably small. A series of 14-day data assimilation cycles are performed with different configurations of the EnKF. Included is an experiment in which the model is assumed to be perfect and experiments in which model error is simulated by the addition of an ensemble of approximately balanced perturbations with a specified statistical structure. The results indicate that the EnKF, with 64 ensemble members, performs well in the present context. The growth rate of small perturbations in the model is examined and found to be slow compared with the corresponding growth rate in an operational forecast model. This is partly due to a lack of horizontal resolution and partly due to a lack of realistic parameterizations. The growth rates in both models are found to be smaller than the growth rate of differences between forecasts with the operational model and verifying analyses. It is concluded that model-error simulation would be important, if either of these models were to be used with the EnKF for the assimilation of real observations."
"7004060399;7006735547;","Tropospheric response to stratospheric perturbations in a relatively simple general circulation model",2002,"10.1029/2001GL014284","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036555118&doi=10.1029%2f2001GL014284&partnerID=40&md5=d319300924fadf3ce41ad59f1ca1af30","The sensitivity of the tropospheric extratropical circulation to thermal perturbations of the polar stratosphere is examined in a dry primitive equation general circulation model with zonally symmetric forcing and boundary conditions. For sufficiently strong cooling of the polar winter stratosphere, the winter-hemisphere tropospheric jet shifts polewards and strengthens markedly at the surface; this is accompanied by a drop in surface pressure at high latitudes in the same hemisphere. In addition, this extratropical tropospheric response is found to be very similar to the model's leading pattern of internal variability. These results are tested for robustness at several horizontal and vertical resolutions, and the same tropospheric response is observed at all but the lowest resolution tested. The behavior of this relatively simple model is broadly consistent with recent observational and modeling studies of trends in extratropical atmospheric variability."
"8884425800;35514012200;","Interannual variability of the dynamics and thermodynamics of the tropical Indian Ocean",1999,"10.1175/1520-0442(1999)012<2300:ivotda>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033172631&doi=10.1175%2f1520-0442%281999%29012%3c2300%3aivotda%3e2.0.co%3b2&partnerID=40&md5=38634d7ed297d2f7f5331a4acb84f002","Interannual variability of the tropical Indian Ocean is studied with a reduced gravity, primitive equation, ocean general circulation model (OGCM). The OGCM is coupled to an atmospheric mixed layer model for surface heat flux computation. The seasonal simulation of sea surface temperatures (SST), current, and thermocline structures are in good agreement with observations and other models. The seasonal cycle of SST along the equator exhibits an eastward propagation with larger variability in the west. The interannual simulations are carried out over 1980-95 with interannual wind stresses and wind speeds but climatological data for solar radiation and cloudiness. The SST anomalies are smaller than 1°C over most of the basin and the leading EOF shows an ENSO-related warming. However, the correlation between the Southern Oscillation index and the time series of the leading EOF is only -0.51 and SST anomalies of similar magnitudes as an El Nino year appear in other years too. ENSO-related equatorial winds determine the SST anomalies along the coast of Sumatra and this anomaly in the eastern southern tropical Indian Ocean (STIO) is typically opposite in sign to the anomaly in the western STIO. The western STIO has some of the largest SSTA because of a shallow thermocline and the entrainment effects associated with wind stress curl anomalies in the region. The quasi-biennial oscillation in the thermocline and the SST gradient in the STIO is correlated with the Somali jet, which in turn is correlated with the Indian summer monsoon. An experiment with climatological wind stresses but interannual wind speeds demonstrates that the wind-driven variations in SST are larger than previously estimated with relaxation type heat fluxes. A parallel experiment with climatological wind speeds but interannual wind stresses shows that there are regions where heat fluxes contribute significantly to SST variability. Another simulation with interannual data for radiation and cloudiness shows that model simulation is affected significantly in some regions by the use of climatological data for solar radiation and cloudiness. A model experiment with an open eastern boundary provides a simplistic illustration of the effects of the Indonesian Throughflow (ITF). The main influence of the ITF is to warm the Indian Ocean and reduce the effect of upwelling on SST."
"35894581100;55924208000;","Predictability and finite‐time instability of the northern winter circulation",1993,"10.1002/qj.49711951004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027388691&doi=10.1002%2fqj.49711951004&partnerID=40&md5=ac9b33479539ecf3a8634a6fdf797dc8","The finite‐time instability and associated predictability of atmospheric of atmospheric circulations are defined in terms of the largest singular values, and associated singular vectors, of the linear evolution operator determined form given equations of motion. These quantities are calculated in both a barotropic and a three‐level quasi‐geostrophic model, using as basic states realistic large‐scale northern wintertime flows that represent the climatological state, regime composites, and specific realizations of these regimes. for time‐invariant basic states, the singular vectors are compared with the corresponding normal‐mode solutions; it is shown that the perturbations defined (at the initial time) by the singular vectors have much larger growth rates than the normal modes, and possess a more localized spatial structure. The regimes studied have opposite values of the Pacific/North American (PNA) index, and growth rates for the barotropic basis states appear to confirm earlier studies that the barotropic instability of the negative PNA states may be larger than the corresponding positive PNA states. The evolution of the singular‐vector perturbations, with emphasis on the vertical structure, is compared for time‐evolving and time‐invariant baroclinic basis states; the effects of nonlinearity are also discusses. It is shown that, in the baroclinic model, interactions between synoptic‐scale eddies in the time‐evolving basic state and in the perturbation field are fundamental for studying the predictability of transitions in the large‐scale circulation. Consequently results obtained from linear calculations using very smooth basic states cannot properly account for such predictability. These results form the basis of a technique used to initialize ensembles of forecasts made with a primitive‐equation model, and are described in the companion paper (Mureau et al. 1993). Copyright © 1993 Royal Meteorological Society"
"7201972249;7004048039;7201835429;","Numerical simulations of tropical cyclone-ocean interaction with a high-resolution coupled model",1993,"10.1029/93jd02370","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0342442956&doi=10.1029%2f93jd02370&partnerID=40&md5=d92ea21afbb2f4399db1da519ea6dfa1","The model design consisted of the NOAA tropical cyclone prediction model which was coupled with a multilayer primitive equation ocean model. Coupling between the hurricane and the ocean models was carried out by passing into the ocean model the wind stress, heat, and moisture fluxes computed in the hurricane model. The new sea surface temperature (SST) calculated by the ocean model was then used in the tropical cyclone model. The experiments indicated that the cooling of the sea surface induced by the tropical cyclone resulted in a significant impact on the ultimate storm intensity due to the reduction of total heat flux directed into the tropical cyclone above the regions of decreased SST. The sea surface cooling produced by the tropical cyclones was found to be larger when the storms moved slower. In the experiments run without an initial basic flow, the maximum SST anomaly was about -5.6°C with a resulting difference in the minimum sea level pressure and maximum surface winds of 16.4 hPa and -7 m s-1, respectively. In contrast, in the experiments run with the 7.5 m s-1 basic flow, the maximum SST anomalies ranged from about 2.6° to 3.0°C with a difference in the minimum sea level pressure and maximum surface winds of about 7.3 hPa and -2.7 m s-1. The tropical cyclone-ocean coupling significantly influenced the storm track only for the case with no basic flow and the 2.5 m s-1 easterly flow. -from Authors"
"7004014731;7403263977;","Transient response to localized episodic heating in the tropics. Part I: excitation and short-time near-field behavior.",1987,"10.1175/1520-0469(1987)044<0458:TRTLEH>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023480093&doi=10.1175%2f1520-0469%281987%29044%3c0458%3aTRTLEH%3e2.0.CO%3b2&partnerID=40&md5=11f774b39fa4c7358e0adb86f5aedcb0","The dynamical response to localized, unsteady tropical heating is studied in a stochastic framework. Spectral statistics of the random wave response are derived from those of tropical convection using the primitive equations for a spherical baroclinic atmosphere. For short-term heating fluctuations, typical of tropical convection, the response at tropopause level is in accord with classical observations of the Wallace and Kousky Kelvin wave. The fast and ultra-fast Kelvin waves are secondary ingredients of the initial wave spectrum. In the case of slow transitional heating, eg the seasonal drift in monsoon activity between hemispheres, the Kelvin response assumes the form of a damped transient Walker circulation. This E migrating cell captures the salient characteristics of Madden and Julian's composite of the 40-day wave in the tropical Pacific Ocean. -from Authors"
"7404815507;7401436524;56447276100;22137065500;55724055400;35222779200;35221633000;8284622100;24511929800;","The Beijing Climate Center atmospheric general circulation model: Description and its performance for the present-day climate",2010,"10.1007/s00382-008-0487-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72049105844&doi=10.1007%2fs00382-008-0487-2&partnerID=40&md5=ce0b5a77781f3ee988c1587fb54f6988","The Beijing Climate Center atmospheric general circulation model version 2.0.1 (BCC-AGCM2.0.1) is described and its performance in simulating the present-day climate is assessed. BCC-AGCM2.0.1 originates from the community atmospheric model version 3 (CAM3) developed by the National Center for Atmospheric Research (NCAR). The dynamics in BCC-AGCM2.0.1 is, however, substantially different from the Eulerian spectral formulation of the dynamical equations in CAM3, and several new physical parameterizations have replaced the corresponding original ones. The major modification of the model physics in BCC-AGCM2.0.1 includes a new convection scheme, a dry adiabatic adjustment scheme in which potential temperature is conserved, a modified scheme to calculate the sensible heat and moisture fluxes over the open ocean which takes into account the effect of ocean waves on the latent and sensible heat fluxes, and an empirical equation to compute the snow cover fraction. Specially, the new convection scheme in BCC-AGCM2.0.1, which is generated from the Zhang and McFarlane's scheme but modified, is tested to have significant improvement in tropical maximum but also the subtropical minimum precipitation, and the modified scheme for turbulent fluxes are validated using EPIC2001 in situ observations and show a large improvement than its original scheme in CAM3. BCC-AGCM2.0.1 is forced by observed monthly varying sea surface temperatures and sea ice concentrations during 1949-2000. The model climatology is compiled for the period 1971-2000 and compared with the ERA-40 reanalysis products. The model performance is evaluated in terms of energy budgets, precipitation, sea level pressure, air temperature, geopotential height, and atmospheric circulation, as well as their seasonal variations. Results show that BCC-AGCM2.0.1 reproduces fairly well the present-day climate. The combined effect of the new dynamical core and the updated physical parameterizations in BCC-AGCM2.0.1 leads to an overall improvement, compared to the original CAM3."
"6602558284;57202754759;7202367208;7003876681;","Simulating the ice-thickness distribution in a coupled climate model",2001,"10.1029/1999jc000113","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035080465&doi=10.1029%2f1999jc000113&partnerID=40&md5=f799276b21723c6f814fdc415ff2aed0","Climate simulations in a global coupled model are investigated using a dynamic-thermodynamic sea ice and snow model with sophisticated thermodynamics and a subgrid scale parameterization for multiple ice thicknesses. In addition to the sea ice component, the model includes a full primitive-equation ocean and a simple energy-moisture balance atmosphere. We introduce a formulation of the ice thickness distribution that is Lagrangian in thickness-space. The method is designed to use fewer thickness categories because it adjusts to place resolution where it is needed most and it is free of diffusive effects that tend to smooth Eulerian distributions. Experiments demonstrate that the model does reasonably well in simulating the mean Arctic climate. We find the climate of the Arctic and northern North Atlantic is sensitive to resolving the ice-thickness distribution when comparing the model results to a simulation with a two-level sea ice model. The ice-thickness distribution causes ice export through Fram Strait to be more variable and more strongly linked to meridional overturning in the North Atlantic Ocean. The Lagrangian formulation of the ice-thickness distribution allows for the inclusion of a vertical temperature profile with relative ease compared to an Eulerian method. We find ice growth rates and ocean surface salinity differ in our model with a well-resolved vertical temperature profile in the ice and snow and an explicit brine-pocket parameterization compared to a simulation with Semtner zero-layer thermodynamics. Although these differences are important for the climate of the Arctic, the effects of an ice thickness distribution are more dramatic and extend into the northern North Atlantic. Sensitivity experiments indicate that five ice-thickness categories with ∼50-cm vertical temperature resolution capture the effects of the ice-thickness distribution on the heat and freshwater exchange across the surface in the presence of sea ice in these simulations. Copyright 2001 by the American Geophysical Union."
"24077600000;23484340400;8946494600;55394412800;7006263720;6603871013;11939722900;7404142321;57193921169;7401969705;7004539332;16177522400;16312624300;57193920163;7403744370;23485410200;36623546300;6506511319;22134875500;23028130200;26659116700;7404678955;8982748700;6603463248;14045744500;57193916194;7404029779;55241394500;56804725600;7005167347;55628584418;7005561827;7006176909;6602887222;18635820300;20435098200;6507112497;16445293700;","The Met Office Unified Model Global Atmosphere 6.0/6.1 and JULES Global Land 6.0/6.1 configurations",2017,"10.5194/gmd-10-1487-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015889548&doi=10.5194%2fgmd-10-1487-2017&partnerID=40&md5=5c8d0b00ab4a7def05a0e46dac9b9686","We describe Global Atmosphere 6.0 and Global Land 6.0 (GA6.0/GL6.0): The latest science configurations of the Met Office Unified Model and JULES (Joint UK Land Environment Simulator) land surface model developed for use across all timescales. Global Atmosphere 6.0 includes the ENDGame (Even Newer Dynamics for General atmospheric modelling of the environment) dynamical core, which significantly increases mid-latitude variability improving a known model bias. Alongside developments of the model's physical parametrisations, ENDGame also increases variability in the tropics, which leads to an improved representation of tropical cyclones and other tropical phenomena. Further developments of the atmospheric and land surface parametrisations improve other aspects of model performance, including the forecasting of surface weather phenomena. <br><br> We also describe GA6.1/GL6.1, which includes a small number of long-standing differences from our main trunk configurations that we continue to require for operational global weather prediction. <br><br> Since July 2014, GA6.1/GL6.1 has been used by the Met Office for operational global numerical weather prediction, whilst GA6.0/GL6.0 was implemented in its remaining global prediction systems over the following year. © Author(s) 2017."
"35576886500;7102620639;35588602200;","Simulations of radiocarbon in a coarse-resolution world ocean model. 1. Steady state prebomb distributions",1989,"10.1029/JC094iC06p08217","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024319349&doi=10.1029%2fJC094iC06p08217&partnerID=40&md5=bf50133741e67f371ada1514b451f59d","This paper presents the results of five numerical simulations of the radiocarbon distribution in the ocean using the Geophysical Fluid Dynamics Laboratory primitive equation world ocean general circulation model. The model has a 4.5° latitude by 3.75° longitude grid, 12 vertical levels, and realistic continental boundaries and bottom topography. The model is forced at the surface by observed, annually averaged temperatures, salinities, and wind stresses. There are no chemical transformations or transport of 14C by biological processes in the model. Each simulation in this paper has been run out the equivalent of several thousand years to simulate the natural, steady state distribution of 14C in the ocean. In a companion paper the final state of these simulations is used as the starting point for simulations of the ocean's transient uptake of bomb-produced 14C. The model reproduces the mid-depth 14C minimum observed in the North Pacific and the strong front near 45°S between old, deep Pacific waters and younger circumpolar waters. In the Atlantic, the model's deep 14C distribution is much too strongly layered with relatively old water from the Antarctic penetrating into the northern reaches of the North Atlantic basin. Two thirds of the decay of 14C between 35°S and 35°N is balanced by local 14C input from the atmosphere and downward transport by vertical mixing (both diffusion and advective stirring). Only one third is balanced by transport of 14C from high latitudes. A moderately small mixing coefficient of 0.3 cm2 s-1 adequately parameterizes vertical diffusion in the upper kilometer. Spatial variation in gas exchange rates is found to have a negligible effect on the deepwater radiocarbon values. Ventilation of the circumpolar region is organized in the model as a deep overturning cell which penetrates as much as 3500 m below the surface. While allowing the circumpolar deep water to be relatively well ventilated, the overturning cell restricts the ventilation of the deep Pacific and Indian basins to the north. This study utilizes three different realizations of the ocean circulation. One is generated by a purely prognostic model, in which only surface temperatures and salinities are restored to observed values. Two are generated by a semidiagnostic model, in which interior temperatures and salinities are restored toward observed values with a 1/50 year-1 time constant. The prognostic version is found to produce a clearly superior deep circulation in spite of producing interior temperatures and salinities which deviate very noticeably from observed values. The weak restoring terms in the diagnostic model suppress convection and other vertical motions, causing major disruptions in the diagnostic model's deep sea ventilation."
"7202611735;7101630970;7006105125;","The global response to tropical heating in the Madden-Julian oscillation during the northern winter",2004,"10.1256/qj.02.123","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4844231277&doi=10.1256%2fqj.02.123&partnerID=40&md5=d4c4d6f278113b261bdd2c88f923b86a","A life cycle of the Madden-Julian oscillation (MJO) was constructed, based on 21 years of outgoing long-wave radiation data. Regression maps of NCEP-NCAR reanalysis data for the northern winter show statistically significant upper-tropospheric equatorial wave patterns linked to the tropical convection anomalies, and extratropical wave patterns over the North Pacific, North America, the Atlantic, the Southern Ocean and South America. To assess the cause of the circulation anomalies, a global primitive-equation model was initialized with the observed three-dimensional (3D) winter climatological mean flow and forced with a time-dependent heat source derived from the observed MJO anomalies. A model MJO cycle was constructed from the global response to the heating, and both the tropical and extratropical circulation anomalies generally matched the observations well. The equatorial wave patterns are established in a few days, while it takes approximately two weeks for the extratropical patterns to appear. The model response is robust and insensitive to realistic changes in damping and basic state. The model tropical anomalies are consistent with a forced equatorial Rossby-Kelvin wave response to the tropical MJO heating, although it is shifted westward by approximately 20° longitude relative to observations. This may be due to a lack of damping processes (cumulus friction) in the regions of convective heating. Once this shift is accounted for, the extratropical response is consistent with theories of Rossby wave forcing and dispersion on the climatological flow, and the pattern correlation between the observed and modelled extratropical flow is up to 0.85. The observed tropical and extratropical wave patterns account for a significant fraction of the intraseasonal circulation variance, and this reproducibility as a response to tropical MJO convection has implications for global medium-range weather prediction. © Royal Meteorological Society, 2004."
"7101630970;35974590700;","A model of the Asian summer monsoon. Part I: the global scale",1995,"10.1175/1520-0469(1995)052<1329:AMOTAS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029526180&doi=10.1175%2f1520-0469%281995%29052%3c1329%3aAMOTAS%3e2.0.CO%3b2&partnerID=40&md5=04a764a26178c1643c8b1de2797eadc9","A time-dependent primitive equation model with specified zonal flow, mountains, and diabatic heating is described. The model is used to investigate the effects of mountains, diabatic heating, and the nonlinear interactions of their responses in the June-August large-scale global circulation. Particular emphasis is placed on the Asian summer monsoon, a dominant feature of the global circulation at this time. The prescribed heating is calculated as a residual in the time-mean thermodynamic equation from ECMWF data, and the model employs a linear surface drag that is enhanced over the land. The integration is initiated with an observed June-August zonal-mean flow that is maintained throughout the integration. A smoothed earth topography is raised from days 0 to 5 with hydrostatic adjustments made to temperature and surface pressure. -from Authors"
"7102389805;","Mechanisms determining the atmospheric response to sea surface temperature anomalies.",1981,"10.1175/1520-0469(1981)038<0554:MDTART>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019663622&doi=10.1175%2f1520-0469%281981%29038%3c0554%3aMDTART%3e2.0.CO%3b2&partnerID=40&md5=b2297c0a78df5dde6a0c052b94ffdf4f","A simple model is used to study the mechanisms which control the local and remote (teleconnection) response of the atmosphere to the thermal forcing resulting from sea surface temperature (SST) anomalies located at various latitudes. The model chosen is a linear baroclinic spherical primitive equation model containing a zonally symmetric basic state with horizontal and vertical shear. An iterative procedure is developed in which the total diabatic heating resulting from the initial heating by the SST anomaly is calculated via feedbacks between the heating and the dynamic response of the system. -from Author"
"9239355400;55716319700;7005561589;","Is the North Atlantic Oscillation a breaking wave?",2004,"10.1175/1520-0469(2004)061<0145:ITNAOA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342308722&doi=10.1175%2f1520-0469%282004%29061%3c0145%3aITNAOA%3e2.0.CO%3b2&partnerID=40&md5=652b7cce2988c28ffafba18c5b784147","Given the recent observational evidence that the positive (negative) phase of the North Atlantic Oscillation (NAO) is the remnant of anticyclonic (cyclonic) wave breaking, this study uses a multilevel primitive equation model to investigate important dynamical attributes of the above wave breaking behavior. For this purpose, a hierarchy of different basic states (two- and three-dimensional) and initial perturbations are used. With the three-dimensional climatological flow as the basic state, it is found that initial perturbations located equatorward (poleward) and upstream of the climatological Atlantic jet lead to wave breaking similar to that of the positive (negative) NAO phase. Consistently, analysis of observational data indeed shows that the Pacific storm track is displaced equatorward (poleward) prior the onset of the positive (negative) NAO phase. This result suggests that the latitudinal position of the Pacific storm track plays an important role for determining the phase of the NAO. Sensitivity experiments show that individual life cycles resemble each other only within the NAO region, but have large case-to-case variability outside of the NAO region. Calculations with zonally symmetric basic states fail to produce wave breaking of the correct spatial and temporal scale, underscoring the dynamical significance of the three-dimensional climatological flow. © 2004 American Meteorological Society."
"8884425800;36785148100;7102016414;7404188013;35514012200;","Effects of penetrative radiation of the upper tropical ocean circulation",2002,"10.1175/1520-0442(2002)015<0470:EOPROT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036501334&doi=10.1175%2f1520-0442%282002%29015%3c0470%3aEOPROT%3e2.0.CO%3b2&partnerID=40&md5=a18238e69ce674901595abb2d2de27da","The effects of penetrative radiation on the upper tropical ocean circulation have been investigated with an ocean general circulation model (OGCM) with attenuation depths derived from remotely sensed ocean color data. The OGCM is a reduced gravity, primitive equation, sigma coordinate model coupled to an advective atmospheric mixed layer model. These simulations use a single exponential profile for radiation attenuations in the water column, which is quite accurate for OGCMs with fairly coarse vertical resolution. The control runs use an attenuation depth of 17 m while the simulations use spatially variable attenuation depths. When a variable depth oceanic mixed layer is explicitly represented with interactive surface heat fluxes, the results can be counterintuitive. In the eastern equatorial Pacific, a tropical ocean region with one of the strongest biological activity, the realistic attenuation depths result in increased loss of radiation to the subsurface, but result in increased sea surface temperatures (SSTs) compared to the control run. Enhanced subsurface heating leads to weaker stratification, deeper mixed layers, reduced surface divergence, and hence less upwelling and entrainment. Thus, some of the systematic deficiencies in the present-day climate models, such as the colder than observed cold tongue in the equatorial Pacific may simply be related to inaccurate representation of the penetrative radiation and can be improved by the formulation presented here. The differences in ecosystems in each of the tropical oceans are clearly manifested in the manner in which biological heat trapping affects the upper ocean. While the tropical Atlantic has many similarities to the Pacific, the Amazon, Congo, and Niger Rivers' discharges dominate the attenuation of radiation. In the Indian Ocean, elevated biological activity and heat trapping are away from the equator in the Arabian Sea and the southern Tropics. For climate models, in view of their sensitivity to the zonal distribution of SST, using a basin mean of the ocean color-derived attenuation depth reduces the SST errors significantly in the Pacific although they occur in regions of high mean SST and may have potential feedbacks in coupled climate models. On the other hand, the spatial variations of attenuation depths in the Atlantic are crucial since using the basin mean produces significant errors. Thus the simplest and the most economic formulation is to simply employ the annual mean spatially variable attenuation depths derived from ocean color."
"7004098470;6602085180;7102808449;7103139129;7006501583;","Dynamics of the Kuroshio/Oyashio current system using eddy-resolving models of the North Pacific Ocean",1996,"10.1029/95JC01674","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029773182&doi=10.1029%2f95JC01674&partnerID=40&md5=7d96aa04396639ddfe9019569a1acaa3","A set of numerical simulations is used to investigate the Pacific Ocean circulation north of 20°S, with emphasis on the Kuroshio/Oyashio current system. The primitive equation models used for these simulations have a free surface and realistic geometry that includes the deep marginal seas such as the Sea of Japan. Most of the simulations have 1/8° resolution for each variable but range from 1/2°, 1.5-layer reduced gravity to 1/16°, six layer with realistic bottom topography. These are used to investigate the dynamics of the Kuroshio/Oyashio current system and to identify the processes that contribute most to the realism of the simulations. This is done by model-data comparisons, by using the modularity of layered ocean models to include/exclude certain dynamical processes, by varying the model geometry and bottom topography, and by varying model parameters such as horizontal grid resolution, layer structure, and eddy viscosity. In comparison with observational data the simulations show that the barotropic mode, at least one internal mode, nonlinearity, high ""horizontal"" resolution (1/8° or finer), the regional bottom topography, and the wind forcing are critical for realistic simulations. The first four are important for baroclinic instability (eddy-mean energetics actually show mixed barotropic-baroclinic instability), the wind curl pattern for the formation and basic placement of the current system, and the bottom topography for the distribution of the instability and for influences on the pathways of the mean flow. Both the Hellerman and Rosenstein (1983) (HR) monthly wind stress climatology and 1000-mbar winds from the European Centre for Medium-Range Weather Forecasts (ECMWF) have been used to drive the model. East of about 150°E, they give a mean latitude for the Kuroshio Extension that differs by about 3°, approximately 34°N for HR, 37°N for ECMWF, and 35°N observed. The subarctic front is the northern boundary of the subtropical gyre. It is associated with the annual and April-September mean zero wind stress curl lines (which are similar), while the Kuroshio Extension is associated with wintertime zero wind stress curl. This means that part of the flow from the Kuroshio must pass north of the Kuroshio Extension and connect with the Oyashio and subarctic front. Realistic routes for this connection are flow through the Sea of Japan, a nonlinear route separated from the east coast of Japan, and bifurcation of the Kuroshio at the Shatsky Rise. In addition, the six-layer simulations show a 3-Sv meridional overturning cell with southward surface flow and northward return flow centered near 400 m depth. Baroclinic instability plays a critical role in coupling the shallow and abyssal layer circulations and in allowing the bottom topography to strongly influence the shallow circulation. By this means the Izu Ridge and Trench and seamounts upstream and downstream of these have profound influence on (1) the mean path of the Kuroshio and its mean meanders south and east of Japan and (2) on separating the northward flow connecting the Kuroshio and the Oyashio/subarctic front from the east coast of Japan. Without the topographic influence the models show an unrealistic northward current along the east coast of Japan. In essence, the topography regulates the location and strength of the baroclinic instability. The baroclinic instability gives eddy-driven deep mean flows that follow the f/h contours (where f is the Coriolis parameter and h is the depth of the water column) of the bottom topography. These abyssal currents then strongly influence the pathway for subtropical gyre flow north of the Kuroshio Extension and steer the mean meanders in the Kuroshio south and east of Japan. This is corroborated by current meter data from the Kuroshio Extension Regional Experiment (World Ocean Circulation Experiment line PCM 7). The meander path south of Japan depends on the occurrence of baroclinic instability west of the Izu Ridge; otherwise, a straight path occurs. The pathway shows little sensitivity to the Tokara Strait transport over the range simulated (36-72 Sv in yearly means). However, interannual increases in wind forcing or Tokara Strait transport give rise to a predominant meander path, while decreases yield a predominant straight path. Resolution of 1/8° in an ocean model is comparable to the 2.5° resolution used in atmospheric forecast models in the early 1980s based on the first internal mode Rossby radius of deformation. Model comparisons at 1/8° and 1/16° resolution and comparisons with current meter data and Geosat altimeter data show that 1/16° resolution is needed for adequate eastward penetration of the high eddy kinetic energy associated with the Kuroshio Extension. Copyright 1996 by the American Geophysical Union."
"55716319700;55739579300;","The dynamical relationship between subtropical and eddy-driven jets",2003,"10.1175/1520-0469(2003)060<1490:TDRBSA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038080907&doi=10.1175%2f1520-0469%282003%29060%3c1490%3aTDRBSA%3e2.0.CO%3b2&partnerID=40&md5=a3cf07e7029e0203e099a215796b2830","This study examines the impact of a subtropical jet on the development at baroclinic waves and polar-front jets with an idealized multilevel primitive equation model. Linear stability analysis and initial-value approaches suggest that baroclinic wave growth is most favored along the subtropical jet only when this jet is sufficiently strong. For a subtropical jet of modest strength, the most favorable region for baroclinic wave growth often lies 20° to 30° poleward of the subtropical jet. establishing an eddy-driven jet that is latitudinally well separated from the subtropical jet."
"7005814217;7202741460;","Nonlinear response of atmospheric vortices to heating by organized cumulus convection.",1986,"10.1175/1520-0469(1986)043<1559:NROAVT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022823260&doi=10.1175%2f1520-0469%281986%29043%3c1559%3aNROAVT%3e2.0.CO%3b2&partnerID=40&md5=6c2e89da1992b59db3120d7e7f6ecb8a","Using an axisymmetric primitive-equation tropical cyclone model, we first illustrate the way in which nonlinear processes contribute to the development of an atmospheric vortex. These numerical experiments show that nonlinearities allow a given diabatic heat source to induce larger tangential wind (and kinetic energy) changes as the vortex develops and the inertial stability becomes large. In an attempt to gain a deeper theoretical understanding of this process, we consider the energy cycle in the balanced vortex equations of Eliassen. The temporal behavior of the total potential energy P is governed by dP/dt = H - C, where H is the rate of generation of total potential energy by diabatic heating, and C is the rate of conversion to kinetic energy. We define a time- dependent system efficiency parameter as eta(t) = C/H. Then, using the dynamical simplifications of balanced vortex theory, we express eta(t) as a weighted average of a dynamic efficiency factor eta(r, z, t). The dynamic efficiency factor is a measure of the efficacy of diabatic heating at any point in generating kinetic energy and can be determined by solving a second-order partial differential equation whose coefficients and right-hand side depend only on the instantaneous vortex structure. The diagnostic quantities eta(t) and eta(r, z, t) are utilized in the analysis of several balanced numerical experiments with different vertical and radial distributions of a diabatic heat source. -Authors"
"6701339411;7201852968;7004279859;","A semi-implicit semi-Lagrangian fully compressible regional forecast model",1990,"10.1175/1520-0493(1990)118<1970:ASISLF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025659039&doi=10.1175%2f1520-0493%281990%29118%3c1970%3aASISLF%3e2.0.CO%3b2&partnerID=40&md5=83175632830bdc95dcf07f87777cd878","The semi-implicit algorithm, originally developed by Robert for an economical integration of the primitive equations in large-scale models of the atmosphere, is here generalized in order to integrate the fully compressible, nonhydrostatic equations. We show that there is little computational overhead associated with the integration of the full, and hence presumably more correct, set of equations that do not invoke the hydrostatic assumption to exclude the high frequency, vertically propagating acoustic modes. -Authors"
"7003843648;7003674085;7403589770;","The transient atmospheric circulation response to North Atlantic SST and sea ice anomalies",2007,"10.1175/JCLI4278.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547860757&doi=10.1175%2fJCLI4278.1&partnerID=40&md5=7a3934923b47b55be4a7548a3e35f8ba","The objective of this study is to investigate the transient evolution of the wintertime atmospheric circulation response to imposed patterns of SST and sea ice extent anomalies in the North Atlantic sector using a large ensemble of experiments with the NCAR Community Climate Model version 3 (CCM3). The initial adjustment of the atmospheric circulation is characterized by an out-of-phase relationship between geopotential height anomalies in the lower and upper troposphere localized to the vicinity of the forcing. This initial baroclinic response reaches a maximum amplitude in ∼5-10 days, and persists for 2-3 weeks. Diagnostic results with a linear primitive equation model indicate that this initial response is forced by diabatic heating anomalies in the lower troposphere associated with surface heat flux anomalies generated by the imposed thermal forcing. Following the initial baroclinic stage of adjustment, the response becomes progressively more barotropic and increases in both spatial extent and magnitude. The equilibrium stage of adjustment is reached in 2-2.5 months, and is characterized by an equivalent barotropic structure that resembles the hemispheric North Atlantic Oscillation-Northern Annular Mode (NAO-NAM) pattern, the model's leading internal mode of circulation variability over the Northern Hemisphere, The maximum amplitude of the equilibrium response is approximately 2-3 times larger than that of the initial response. The equilibrium response is primarily maintained by nonlinear transient eddy fluxes of vorticity (and, to a lesser extent, heat), with diabatic heating making a limited contribution in the vicinity of the forcing. © 2007 American Meteorological Society."
"7601492669;","An explicit simulation of tropical cyclones with a triply nested movable mesh primitive equation model: TCM3. Part I: Model description and control experiment",2001,"10.1175/1520-0493(2001)129<1370:AESOTC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035359933&doi=10.1175%2f1520-0493%282001%29129%3c1370%3aAESOTC%3e2.0.CO%3b2&partnerID=40&md5=671271cb9838e7467267e64300b8cb92","Results from an explicit simulation of tropical cyclones are presented in this study. The numerical model used in the study is the triply nested movable mesh primitive equation model newly developed by the author. It uses the hydrostatic primitive equations with explicit treatment of cloud microphysics. The integration domain is triply nested by a two-way nesting strategy with the two interior meshes being movable following the model tropical cyclone. The model physics are chosen based on the up-to-date developments, including an E-∈ closure scheme for subgrid-scale vertical turbulent mixing [with E being the turbulent kinetic energy (TKE), and ∈ the TKE dissipation rate]; a modified Monin-Obukhov scheme for the surface flux calculation, with an option to include the effect of sea spray evaporation: an explicit treatment of mixed-ice phase cloud microphysics; and dissipative heating, which has been found to be important in tropical cyclones. New developments include a new iteration scheme to solve the nonlinear balance equation in σ coordinates in the nested-mesh grids, which is used for model initialization: an initialization scheme for both TKE and its dissipation rate fields based on a level-2 turbulence closure scheme deduced from the TKE and its dissipation rate equations; and a modified formula for the timescale that determines the rate at which cloud ice converts to snow via the Bergeron process. The success of the multiply nested movable mesh approach and the conservative property of the numerical model is first tested with an experiment in which the model was initialized with an axisymmetric cyclonic vortex embedded in a uniform easterly flow of 5 ms-1 on an f plane, but with no model physics. Results from a control experiment with the full model physics are then discussed in detail to demonstrate the capability of the model in simulating many aspects of the tropical cyclone, especially the inner core structure and both the inner and outer spiral rainbands in the cyclone circulation. The vortex Rossby waves in the simulated tropical cyclone core region are also identified and analyzed. Sensitivity of the model results to various model physics and major physical parameters will be given in a companion paper."
"57103407500;7005242066;","Modeling the lateral circulation in straight, stratified estuaries",2004,"10.1175/1520-0485(2004)034<1410:MTLCIS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242696207&doi=10.1175%2f1520-0485%282004%29034%3c1410%3aMTLCIS%3e2.0.CO%3b2&partnerID=40&md5=831e3eae440b4db1050639ad2d62c2e5","The dynamics of lateral circulation in an idealized, straight estuary under varying stratification conditions is investigated using a three-dimensional, hydrostatic, primitive equation model in order to determine the importance of lateral circulation to the momentum budget within the estuary. For all model runs, lateral circulation is about 4 times as strong during flood tides as during ebbs. This flood-ebb asymmetry is due to a feedback between the lateral circulation and the along-channel tidal currents, as well as to fime-varying stratification over a tidal cycle. As the stratification is increased, the lateral circulation is significantly reduced because of the adverse pressure gradient set up by isopycnals being tilted by the lateral flow itself. When rotation is included, a time-dependent, cross-channel Ekman circulation is driven, and the tidally averaged, bottom lateral circulation is enhanced toward the right bank (when looking toward the ocean in the Northern Hemisphere). This asymmetry in the tidally averaged bottom lateral circulation may lead to asymmetric sediment transport, leading to asymmetric channel profiles in straight estuaries. For the weakly stratified model run, advection due to lateral currents is a dominant term in both the along-channel and cross-channel momentum equations over a tidal cycle and for the tidally averaged momentum equations. In the tidally averaged, along-channel momentum equation, lateral advection acts as a driving term for the estuarine exchange flow and can be larger than the along-channel pressure gradient. Therefore, it should not be ignored when estimating momentum budgets in estuaries. © 2004 American Meteorological Society."
"7006735547;7004060399;","Stratosphere-trotosphere coupling in a relatively simple AGCM: The role of eddies",2004,"10.1175/1520-0442(2004)017<0629:SCIARS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642403079&doi=10.1175%2f1520-0442%282004%29017%3c0629%3aSCIARS%3e2.0.CO%3b2&partnerID=40&md5=8b2743847f0503c19068481508c7c2ca","The extratropical circulation response to cooling of the polar winter stratosphere in a simple AGCM is investigated. The AGCM is a dry hydrostatic primitive equation model with zonally symmetric boundary conditions and analytically specified physics. It is found that, as the polar-winter stratosphere is cooled, the tropospheric jet shifts poleward. This response projects almost entirely and positively (by convention) onto the AGCM's annular mode. At the same time, the vertical flux of wave activity from the troposphere to the stratosphere is reduced and the meridional flux of wave activity from high to low latitudes is increased. Thus, as the stratosphere is cooled, the stratospheric wave drag is reduced. In order to understand this response, the transient adjustment of the stratosphere-troposphere system is investigated using an ensemble of ""switch on"" stratospheric cooling runs of the AGCM. The response to the switch-on stratospheric cooling descends from the upper stratosphere into the troposphere on a time scale that matches simple downward-control theory estimates. The downward-control analysis is pursued with a zonally symmetric model that uses as input the thermal and eddy-driving terms from the eddying AGCM. With this model, the contributions to the response from the thermal and eddy-driving perturbations can be investigated separately, in the absence of eddy feedbacks. It is found that the stratospheric thermal perturbation, in the absence of such feedbacks, induces a response that is confined to the stratosphere. The stratospheric eddy-driving perturbation, on the other hand, induces a response that penetrates into the midtroposphere but does not account, in the zonally symmetric model, for the tropospheric jet shift. Furthermore, the tropospheric eddy-driving perturbation, in the zonally symmetric model, induces a strong upward response in the stratospheric winds. From these experiments and from additional experiments with the eddying AGCM, it is concluded that the stratospheric eddy-driving response induces a tropospheric response, but that the full circulation response results from a two-way coupling between the stratosphere and the troposphere. © 2004 American Meteorological Society."
"15765007300;7402435469;","A baroclinic instability test case for atmospheric model dynamical cores",2006,"10.1256/qj.06.12","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45549097950&doi=10.1256%2fqj.06.12&partnerID=40&md5=833ff05a1190b9d40e97b83b0f6ffee4","A deterministic initial-value test case for dry dynamical cores of atmospheric general-circulation models is presented that assesses the evolution of an idealized baroclinic wave in the northern hemisphere. The initial zonal state is quasi-realistic and completely defined by analytic expressions which are a steady-state solution of the adiabatic inviscid primitive equations with pressure-based vertical coordinates. A two-component test strategy first evaluates the ability of the discrete approximations to maintain the steady-state solution. Then an overlaid perturbation is introduced which triggers the growth of a baroclinic disturbance over the course of several days. The test is applied to four very different dynamical cores at varying horizontal and vertical resolutions. In particular, the NASA/NCAR Finite Volume dynamics package, the National Center for Atmospheric Research spectral transform Eulerian and the semi-Lagrangian dynamical cores of the Community Atmosphere Model CAM3 are evaluated. In addition, the icosahedral finite-difference model GME of the German Weather Service is tested. These hydrostatic dynamical cores represent a broad range of numerical approaches and, at very high resolutions, provide independent reference solutions. The paper discusses the convergence-with-resolution characteristics of the schemes and evaluates the uncertainty of the high resolution reference solutions. © Royal Meteorological Society, 2006."
"20433515900;26643566500;16025236700;7102861155;7201600456;","Balance and ensemble Kalman filter localization techniques",2011,"10.1175/2010MWR3328.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953216060&doi=10.1175%2f2010MWR3328.1&partnerID=40&md5=eb7e42630b0ef6f9d12b57bca3da32c8","In ensemble Kalman filter (EnKF) data assimilation, localization modifies the error covariance matrices to suppress the influence of distant observations, removing spurious long-distance correlations. In addition to allowing efficient parallel implementation, this takes advantage of the atmosphere's lower dimensionality in local regions. There are two primary methods for localization. In B localization, the background error covariance matrix elements are reduced by a Schur product so that correlations between grid points that are far apart are removed. In R localization, the observation error covariance matrix is multiplied by a distancedependent function, so that far away observations are considered to have infinite error. Successful numerical weather prediction depends upon well-balanced initial conditions to avoid spurious propagation of inertialgravity waves. Previous studies note that B localization can disrupt the relationship between the height gradient and the wind speed of the analysis increments, resulting in an analysis that can be significantly ageostrophic. This study begins with a comparison of the accuracy and geostrophic balance of EnKF analyses using no localization, B localization, and R localization with simple one-dimensional balanced waves derived from the shallow-water equations, indicating that the optimal length scale for R localization is shorter than for B localization, and that for the same length scale R localization is more balanced. The comparison of localization techniques is then expanded to the Simplified Parameterizations, Primitive Equation Dynamics (SPEEDY) global atmospheric model. Here, natural imbalance of the slow manifold must be contrasted with undesired imbalance introduced by data assimilation. Performance of the two techniques is comparable, also with a shorter optimal localization distance for R localization than for B localization. © 2011 American Meteorological Society."
"7004208552;35552766800;","Features of dominant mesoscale variability, circulation patterns and dynamics in the strait of sicily",2001,"10.1016/S0967-0637(00)00114-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034957569&doi=10.1016%2fS0967-0637%2800%2900114-X&partnerID=40&md5=b94d79d3d26a97b90b8d43ce8d18707a","Combining an intensive hydrographic data survey with a numerical primitive equation model by data assimilation, the main features of dominant mesoscale to subbasin-scale variability in the Strait of Sicily (Mediterranean Sea) during the summer of 1996 are estimated, revealed and described, and several hydrographic and dynamical properties of the flow and variabilities discussed. The feature identification is based on two independent real-time analyses of the variability. One analysis ""subjectively"" evaluates and studies physical field forecasts and their variations. The other more ""objectively"" estimates and forecasts the principal components of the variability. The two independent analyses are found to be in agreement and complementary. The dominant dynamical variations are revealed to be associated with five features: the Adventure Bank Vortex, Maltese Channel Crest, Ionian Shelfbreak Vortex, Messina Rise Vortex, and temperature and salinity fronts of the Ionian slope. These features and their variations are found to have links with the meanders of the Atlantic Ionian Stream. For each feature, the characteristic physical scales, and their deviations, are quantified. The predominant circulation patterns, pathways and transformations of the modified Atlantic water, Ionian water and modified Levantine intermediate water, are then identified and discussed. For each of these water masses, the ranges of temperature, salinity, depth, velocity and residence times, and the regional variations of these ranges, are computed. Based on the estimated fields and variability principal components, several properties of the dynamics in the Strait are discussed. These include: general characteristics of the mesoscale anomalies; bifurcations of the Atlantic Ionian Stream; respective roles of topography, atmospheric forcings and internal dynamics; factors controlling (strengthening or weakening) the vortices identified; interactions of the Messina Rise and Ionian Shelfbreak vortices; and, mesoscale dynamics and relatively complex features along the Ionian slope. For evaluation and validation of the results obtained, in situ data, satellite sea surface temperature images and trajectories of surface drifters are employed, as well as comparisons with previous studies. © 2001 Elsevier Science Ltd."
"7401837691;6701513498;","On the dynamics of a storm track",1993,"10.1175/1520-0469(1993)050<0999:OTDOAS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027789653&doi=10.1175%2f1520-0469%281993%29050%3c0999%3aOTDOAS%3e2.0.CO%3b2&partnerID=40&md5=9367d877a12e618b737da926d2872d5f","An idealized primitive equation model is used to show that localized regions of enhanced baroclinicity do not necessarily lead to localization of eddy activity. By studying the energetics of the storm track, it is shown that while baroclinic conversion does indeed correlate with the region of maximum baroclinicity, it is the downstream radiation of energy through the ageostrophic geopotential fluxes which acts as a trigger for the development and maintenance of eddy activity over less baroclinic regions. Examples of eddy life cycles are given that show that convergence and divergence of ageostrophic fluxes can dominate baroclinic and barotropic conversion, especially in regions with weak baroclinicity. Factors that may limit the zonal extent of a storm track are discussed. -from Authors"
"36442085000;7004266190;","The Boreal Forests and Climate",1992,"10.1002/qj.49711850505","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027098272&doi=10.1002%2fqj.49711850505&partnerID=40&md5=cdca0001b5c64693f9eb543e622f8b24","The sensitivity of modelled northern hemisphere climate to modification of the snow‐covered surface albedo is investigated using the United Kingdom Meteorological Office (UKMO) general circulation model (GCM). the UKMO GCM is a global, primitive‐equation model with 11 layers in the atmosphere. Surface processes in the model are highly parametrized, with bulk aerodynamic formulation of the surface fluxes and a ‘bucket’ soil‐moisture accounting method. the experiment represents in a highly simplified fashion the role of the boreal forests in reducing the surface albedo under snow‐covered conditions. A parametrization of snow‐covered land was developed which allows the maximum albedo attainable with a snow cover to be prescribed as a function of vegetation type. In the standard version of the model the maximum snow‐covered surface albedo attainable is 0.60, which exceeds observed values for the forested areas of the northern hemisphere. the model was integrated twice, with different albedos representing forested and deforested conditions. the sensitivity of the heat and hydrologic budgets for the northern hemisphere and deforested areas is discussed. A detailed analysis of the deforested regions reveals systematic reductions in temperature of up to 2.8 K. Precipitation shows a systematic decrease in the affected regions. the largest decreases occur generally in the months with largest evaporation changes. For the case of no masking by forest vegetation (equivalent to boreal deforestation) the model produces a significant change in the pattern of snow‐melt. the removal of forest affects both the magnitude and the timing of spring snow‐melt, and consequently also the runoff. There are delays in snow‐melt‐induced runoff peaks by a month and increases in the magnitudes by on average 32%. the role of large‐scale advection is investigated by comparison with the results from a single‐column‐model experiment. A realistic representation of the snow‐covered surface albedo is evidently a requirement for simulations of the northern hemisphere climate. Copyright © 1992 Royal Meteorological Society"
"57203054708;35497573900;","Vertical differencing of the primitive equations in sigma coordinates.",1983,"10.1175/1520-0493(1983)111<0034:VDOTPE>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021092415&doi=10.1175%2f1520-0493%281983%29111%3c0034%3aVDOTPE%3e2.0.CO%3b2&partnerID=40&md5=3c6056fc1e2019f506c23bd1a020cfaa","A vertical finite-difference scheme for the primitive equations in sigma coordinates is obtained by requiring that the discrete equations retain some important properties of the continuous equations. A family of schemes is derived whose members conserve total energy, maintain an integral constraint on the vertically integrated pressure gradient force, have a local differencing of the hydrostatic equation, and give exact forms of the hydrostatic equation and the pressure gradient force for particular atmospheres. The proposed scheme is a member of this family that in addition conserves the global mass integral of the potential temperature under adiabatic processes. -Authors"
"6602075440;57201972361;55951683800;7102087968;","Global eddy-resolving ocean simulations driven by 1985-1995 atmospheric winds",1998,"10.1029/1998jc900013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032534929&doi=10.1029%2f1998jc900013&partnerID=40&md5=a20a6eedee75cea7ca87de3d0a2ce7d6","Results are presented from a high-resolution global ocean model that is driven through three decadal cycles of increasingly realistic prescribed atmospheric forcing from the period 1985-1995. The model used (the Parallel Ocean Program) is a z level primitive equation model with active thermohaline dynamics based on the formulation of Bryan [1969] rewritten for massively parallel computers. Improvements to the model include an implicit free-surface formulation of the barotropic mode [Dukowicz and Smith, 1994] and the use of pressure averaging for increasing the numerical time step. This study extends earlier 0.5° simulations of Semtner and Chervin [1992] to higher horizontal resolution with improved treatments of ocean geometry and surface forcing. The computational grid is a Mercator projection covering the global ocean from 77°N to 77°S and has 20 vertical levels. Three successive simulations have been performed on the CM-5 Connection Machine system at Los Alamos using forcing fields from the European Centre for Medium-Range Weather Forecasts (ECMWF). The first run uses monthly wind stresses for 1985-1995 and restoring of surface temperature and salinity to the Levitus [1982] seasonal climatology. The second run is the same but with 3 day-averaged rather than monthly averaged wind stress fields, and the third is the same as the second but uses the monthly climatological ECMWF heat fluxes of Barnier et al. [1995] instead of restoring to climatological sea surface temperatures. Many features of the wind-driven circulation are well represented in the model solutions, such as the overall current patterns, the numerous regions of hydrodynamic instability which correspond to those observed by satellite altimetry, and the filamented structure of the Antarctic Circumpolar Current. However, some features such as the separation points of the Gulf Stream and Kuroshio and the transport through narrow passages such as the Florida Straits are clearly inaccurate and indicate that still higher resolution may be required to correct these deficiencies. Water mass properties and some aspects of the thermohaline circulation are also not always well reproduced, which is partly due to the relatively short length of the integrations. The use of the ECMWF heat fluxes, rather than restoring to climatological surface temperatures, leads to stronger and more realistic surface and deep western boundary currents (primarily in the Atlantic) as well as more realistic meridional heat transport; this is primarily because the equilibrium meridional heat transport implied by the ECMWF surface fluxes is quite large. The ECMWF heat fluxes also produce improved seasonal cycles of sea surface temperature and height in both the northern and southern hemispheres. The 3-day wind forcing gives rise to modes of model variability that are clearly seen in synoptic observations, such as the large-scale 20-100-day oscillations seen in the TOPEX/POSEIDON data, which are barotropic oscillations induced by the high-frequency wind forcing. Additional studies on other aspects of the simulations described here are being conducted by a variety of investigators, and some of these are briefly described."
"24490844700;23966960500;","Uncertainties due to transport-parameter sensitivity in an efficient 3-D ocean-climate model",2005,"10.1007/s00382-004-0508-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16344377940&doi=10.1007%2fs00382-004-0508-8&partnerID=40&md5=3fe1029636a296f5426fdf03c5c8b77e","A simplified climate model is presented which includes a fully 3-D, frictional geostrophic (FG) ocean component but retains an integration efficiency considerably greater than extant climate models with 3-D, primitive-equation ocean representations (20 kyears of integration can be completed in about a day on a PC). The model also includes an Energy and Moisture Balance atmosphere and a dynamic and thermodynamic sea-ice model. Using a semi-random ensemble of 1,000 simulations, we address both the inverse problem of parameter estimation, and the direct problem of quantifying the uncertainty due to mixing and transport parameters. Our results represent a first attempt at tuning a 3-D climate model by a strictly defined procedure, which nevertheless considers the whole of the appropriate parameter space. Model estimates of meridional overturning and Atlantic heat transport are well reproduced, while errors are reduced only moderately by a doubling of resolution. Model parameters are only weakly constrained by data, while strong correlations between mean error and parameter values are mostly found to be an artefact of single-parameter studies, not indicative of global model behaviour. Single-parameter sensitivity studies can therefore be misleading. Given a single, illustrative scenario of CO2 increase and fixing the polynomial coefficients governing the extremely simple radiation parameterisation, the spread of model predictions for global mean warming due solely to the transport parameters is around one degree after 100 years forcing, although in a typical 4,000-year ensemble-member simulation, the peak rate of warming in the deep Pacific occurs 400 years after the onset of the forcing. The corresponding uncertainty in Atlantic overturning after 100 years is around 5 Sv, with a small, but non-negligible, probability of a collapse in the long term. © Springer-Verlag 2005."
"6602197441;6507628238;","Revisiting open boundary conditions from the point of view of characteristic variables",2005,"10.1016/j.ocemod.2004.07.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-11144263230&doi=10.1016%2fj.ocemod.2004.07.001&partnerID=40&md5=38b5d46d20e99db3f525aa0331a5f93e","This paper emphasizes the peculiar role of characteristic variables in the design of open boundary conditions (OBCs). It is shown that local OBCs leading to positive results in previous comparative studies do fulfil two requirements: They make use of incoming characteristic variables (i.e. privilege the hyperbolic aspect of the equations), and satisfy a consistency relationship between the model solution and some external data. The classical OBCs used in atmosphere and ocean modeling are revisited from this point of view. It is shown that several usual boundary conditions should be avoided, while conditions satisfying the two preceding criteria are pointed out. Finally, the application of these criteria to the design of OBCs for primitive equations is discussed. © 2004 Elsevier Ltd. All rights reserved."
"6603948841;57150799100;7401812602;","Nature of global large-scale sea level variability in relation to atmospheric forcing: A modeling study",1998,"10.1029/97jc02907","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031780835&doi=10.1029%2f97jc02907&partnerID=40&md5=01dccc9f8d1b37241966625f350c9ae9","The relation between large-scale sea level variability and ocean circulation is studied using a numerical model. A global primitive equation model of the ocean is forced by daily winds and climatological heat fluxes corresponding to the period from January 1992 to January 1994. The physical nature of sea level's temporal variability from periods of days to a year is examined on the basis of spectral analyses of model results and comparisons with satellite altimetry and tide gauge measurements. The study elucidates and diagnoses the inhomogeneous physics of sea level change in space and frequency domain. At midlatitudes, large-scale sea level variability is primarily due to steric changes associated with the seasonal heating and cooling cycle of the surface layer. In comparison, changes in the tropics and high latitudes are mainly wind driven. Wind-driven variability exhibits a strong latitudinal dependence in itself. Wind-driven changes are largely baroclinic in the tropics but barotropic at higher latitudes. Baroclinic changes are dominated by the annual harmonic of the first baroclinic mode and is largest off the equator; variabilities associated with equatorial waves are smaller in comparison. Wind-driven barotropic changes exhibit a notable enhancement over several abyssal plains in the Southern Ocean, which is likely due to resonant planetary wave modes in basins semienclosed by discontinuities in potential vorticity. Otherwise, barotropic sea level changes are typically dominated by high frequencies with as much as half the total variance in periods shorter than 20 days, reflecting the frequency spectra of wind stress curl. Implications of the findings with regards to analyzing observations and data assimilation are discussed."
"7004914771;7403406440;","Hurricane storm surge simulations for Tampa Bay",2006,"10.1007/BF02798649","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250776969&doi=10.1007%2fBF02798649&partnerID=40&md5=d6b9ed7df763d6ba2c8dbe630a744a94","Using a high resolution, three-dimensional, primitive equation, finite volume coastal ocean model with flooding and drying capabilities, supported by a merged bathymetric-topographic data set and driven by prototypical hurricane winds and atmospheric pressure fields, we investigated the storm surge responses for the Tampa Bay, Florida, vicinity and their sensitivities to point of landfall, direction and speed of approach, and intensity. All of these factors were found to be important. Flooding potential by wind stress and atmospheric pressure induced surge is significant for a category 2 hurricane and catastrophic for a category 4 hurricane. Tide, river, and wave effects are additive, making the potential for flood-induced damage even greater. Since storm surge sets up as a slope to the sea surface, the highest surge tends to occur over the upper reaches of the bay, Old Tampa Bay and Hillsborough Bay in particular. For point of landfall sensitivity, the worst case is when the hurricane center is positioned north of the bay mouth such that the maximum winds associated with the eye wall are at the bay mouth. Northerly (southerly) approaching storms yield larger (smaller) surges since the winds initially set up (set down) water level. As a hybrid between the landfall and direction sensitivity experiments, a storm transiting up the bay axis from southwest to northeast yields the smallest surge, debunking a misconception that this is the worst Tampa Bay flooding case. Hurricanes with slow (fast) translation speeds yield larger (smaller) surges within Tampa Bay due to the time required to redistribute mass. © 2006 Estuarine Research Federation."
"7004978125;7404358451;","Systematic multiscale models for the tropics",2003,"10.1175/1520-0469(2003)060<0393:SMMFTT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141689563&doi=10.1175%2f1520-0469%282003%29060%3c0393%3aSMMFTT%3e2.0.CO%3b2&partnerID=40&md5=fb17b916781bc2ef5a75560c1717634c","Systematic multiscale perturbation theory is utilized to develop self-consistent simplified model equations for the interaction across multiple spatial and/or temporal scales in the Tropics. One of these models involves simplified equations for intraseasonal planetary equatorial synoptic-scale dynamics (IPESD). This model includes the self-consistent quasi-linear interaction of synoptic-scale generalized steady Matsuno-Webster-Gill models with planetary-scale dynamics of equatorial long waves. These new models have the potential for providing self-consistent prognostic and diagnostic models for the intraseasonal tropical oscillation. Other applications of the systematic approach reveal three different balanced weak temperature gradient (WTG) approximations for the Tropics with different regimes of validity in space and time: a synoptic equatorial-scale WTG (SEWTG); a mesoscale equatorial WTG (MEWTG), which reduces to the classical models treated by others; and a new seasonal planetary equatorial WTG (SPEWTG). Both the SPEWTG and MEWTG model equations have solutions with general vertical structure, yet have the linearized dispersion relation of barotropic Rossby waves; thus, these models can play an important role in theories for midlatitude connections with the Tropics. The models are derived both from the equatorial shallow water equations in a simplified context and also as distinguished limits from the compressible primitive equations in general."
"7102389501;56033330500;6601992858;7202484739;56303877000;6506004027;7402331557;7003684235;6603261861;7201670036;7202404301;26431637400;20433821100;6602859094;55732595700;56304422800;7405606991;","The navy global environmental model",2014,"10.5670/oceanog.2014.73","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905244638&doi=10.5670%2foceanog.2014.73&partnerID=40&md5=b8c1d037a9c9fe0a96a11c0a45923b6a","On February 13, 2013, the US Navy's weather forecast system reached a milestone when the NAVy Global Environmental Model (NAVGEM) replaced the Navy Operational Global Atmospheric Prediction System (NOGAPS) for operational global weather prediction. The new operational system NAVGEM 1.1 combines a semi-Lagrangian/semi-implicit dynamical core together with advanced parameterizations of subgrid-scale moist processes, convection, ozone, and radiation. The NAVGEM dynamical core allows for much higher spatial resolutions without the need for the small time steps that would be necessary in NOGAPS. The increased computational efficiency is expected to enable significant increases in resolution in future NAVGEM releases. Model physics improvements in the NAVGEM 1.1 transition include representations of cloud liquid water, cloud ice water, and ozone as fully predicted constituents. Following successful testing of a new mass flux scheme, a second transition to NAVGEM 1.2 occurred on November 6, 2013. Addition of this mass flux parameterization to the eddy diffusion vertical mixing parameterization resulted in a reduction of the cold temperature bias of the lower troposphere over ocean and further increased the forecast skill of NAVGEM. © 2014 by The Oceanography Society. All rights reserved."
"23989037500;7003538187;6508195621;","Atmospheric circulation of tidally locked exoplanets: A suite of benchmark tests for dynamical solvers",2011,"10.1111/j.1365-2966.2011.18315.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79956206680&doi=10.1111%2fj.1365-2966.2011.18315.x&partnerID=40&md5=f53e62ccf4ac8d003de037aab9279b41","The rapid pace of extrasolar planet discovery and characterization is legitimizing the study of their atmospheres via three-dimensional numerical simulations. The complexity of atmospheric modelling and its inherent non-linearity, together with the limited amount of data available, motivate model intercomparisons and benchmark tests. In the geophysical community, the Held-Suarez test is a standard benchmark for comparing dynamical core simulations of the Earth's atmosphere with different solvers, based on statistically averaged flow quantities. In the present study, we perform analogues of the Held-Suarez test for tidally locked exoplanets with the Geophysical Fluid Dynamics Laboratory (GFDL) Princeton Flexible Modelling System (fms) by subjecting both the spectral and finite difference dynamical cores to a suite of tests, including the standard benchmark for the Earth, a hypothetical tidally locked Earth, a 'shallow' hot Jupiter model and a 'deep' model of HD 209458b. We find qualitative and quantitative agreement between the solvers for the Earth, tidally locked Earth and shallow hot Jupiter benchmarks, but the agreement is less than satisfactory for the deep model of HD 209458b. Further investigation reveals that closer agreement may be attained by arbitrarily adjusting the values of the horizontal dissipation parameters in the two solvers, but it remains the case that the magnitude of the horizontal dissipation is not easily specified from first principles. Irrespective of radiative transfer or chemical composition considerations, our study points to limitations in our ability to accurately model hot Jupiter atmospheres with meteorological solvers at the level of 10 per cent for the temperature field and several tens of per cent for the velocity field. Direct wind measurements should thus be particularly constraining for the models. Our suite of benchmark tests also provides a reference point for researchers wishing to adapt their codes to study the atmospheric circulation regimes of tidally locked Earths/Neptunes/Jupiters. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS."
"8884425800;35514012200;","Salinity effects in a tropical ocean model",1998,"10.1029/97jc02438","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032519261&doi=10.1029%2f97jc02438&partnerID=40&md5=7d797418cba2f553c4cb5e3763dfbc2f","A reduced gravity, primitive equation, ocean general circulation model (GCM) with a variable depth mixed layer and a natural boundary condition for freshwater fluxes is employed to investigate the role of salinity in tropical ocean dynamics and thermodynamics. Surface heat fluxes are computed without any feedback to observations by an advective atmospheric mixed layer (AML) model which is coupled to the ocean GCM. We analyze the differences in the tropical Atlantic, Pacific, and the Indo-Pacific basins between control runs (simulations with complete hydrology) and simulations where (1) precipitation (P) is neglected, (2) salinity effects are neglected, or (3) salinity is held constant in each layer. Salinity contributes to pressure gradient forces, mixed layer processes, and vertical stability/mixing. Setting P = 0 in the tropical Atlantic produces larger sea surface temperature (SST) changes than previously estimated due to the realistic oceanic mixed layer model and surface flux formulation. Neglecting salinity effects leads to a different choice of mixing parameters, which feeds back into model dynamics and thermodynamics. Salinity anomalies produce an asymmetric response across the equator in the Atlantic due to differences in the air-sea interactions. Including salinity effects in the tropical Pacific leads to an improved cold tongue simulation. The result is a reduced SST gradient at the equator which will have significant feedback in a coupled system. The same experiment with a restoring surface heat flux leads to an increased SST gradient, indicating that the surface flux parameterization is crucial for interpreting the role of salinity. The Indonesian throughflow (ITF) is reduced when salinity is neglected or held constant. The NINO3 and NINO4 SST indices are almost identical for the control run and the simulations when climatological P is used. However, associated subsurface temperature differences are larger, and they may play a role on decadal timescales. It is thus shown with a comprehensive set of experiments that even in the tropics, salinity plays an important role in the model dynamics and thermodynamics. Copyright 1998 by the American Geophysical Union."
"8884425800;7003531755;35514012200;","Simulation of the tropical oceans with an ocean GCM coupled to an atmospheric mixed-layer model",1996,"10.1175/1520-0442(1996)009<1795:SOTTOW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030485662&doi=10.1175%2f1520-0442%281996%29009%3c1795%3aSOTTOW%3e2.0.CO%3b2&partnerID=40&md5=cba3d420493d750b7bc2aca57398f62c","A reduced gravity, primitive equation, ocean general circulation model (GCM) is coupled to an advective atmospheric mixed-layer (AML) model to demonstrate the importance of a nonlocal atmospheric mixed-layer parameterization for a proper simulation of surface heat fluxes and sea surface temperatures (SST). Seasonal variability of the model SSTs and the circulation are generally in good agreement with the observations in each of the tropical oceans. These results are compared to other simulations that use a local equilibrium mixed-layer model. Inclusion of the advective AML model is demonstrated to lead to a significant improvement in the SST simulation in all three oceans. Advection and diffusion of the air humidity play significant roles in determining SSTs even in the tropical Pacific where the local equilibrium assumption was previously deemed quite accurate. The main, and serious, model flaw is an inadequate representation of the seasonal cycle in the upwelling regions of the eastern Atlantic and Pacific Oceans. The results indicate that the feedback between mixed-layer depths and SSTs can amplify SST errors, implying that increased realism in the modeling of the ocean mixed layer increases the demand for realism in the representation of the surface heat fluxes. The performance of the GCM with a local-equilibrium mixed-layer model in the Atlantic is as poor as previous simple ocean model simulations of the Atlantic. The conclusion of earlier studies that the simple ocean model was at fault may, in fact, not be correct. Instead the local-equilibrium heat flux parameterization appears to have been the major source of error. Accurate SST predictions may, hence, be feasible by coupling the AML model to computationally efficient simple ocean models."
"7006550762;6603364959;7004238859;7006399110;7401548835;","The GISS global climate-middle atmosphere model. Part I: model structure and climatology",1988,"10.1175/1520-0469(1988)045<0329:TGGCMA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024224196&doi=10.1175%2f1520-0469%281988%29045%3c0329%3aTGGCMA%3e2.0.CO%3b2&partnerID=40&md5=de2e97c4ba4072b8482d40fa0bbccee6","The GISS global climate model has been extended to include the middle atmosphere up to an altitude of approximately 85 km. The model has the full array of processes used for climate research, ie numerical solutions of the primitive equations, calculation of radiative and surface fluxes, a complete hydrologic cycle with convective and cloud cover parameterizations etc. In addition, a parameterized gravity wave drag formulation has been incorporated, in which gravity-wave momentum fluxes due to flow over topography, wind shear and convection are calculated at each grid box, using theoretical relationships between the grid-scale variables and expected source strengths. The model produces generally realistic fields of temperature and wind throughout the atmosphere up to approximately 75 km. Important aspects of the current simulation include a proper break between the tropospheric and stratospheric jets, realistic closing off of the wintertime jet in the mesosphere, the observed warm winter/cold summer mesosphere, and a semiannual wind oscillation near the stratopause. The most obvious deficiences are that the long-wave energy itself is somewhat too small in the low and midstratosphere, temperatures are too cold near the model top and are too warm in the polar Southern Hemisphere lower stratosphere during winter. Also, the model generates an inertial oscillation near the equatorial stratopause which may be excessive. -from Authors"
"56929860700;7402024747;7003749554;7006661268;","A coupled atmosphere-fire model: Convective feedback on fire-Line dynamics",1996,"10.1175/1520-0450(1996)035<0875:ACAMCF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030430429&doi=10.1175%2f1520-0450%281996%29035%3c0875%3aACAMCF%3e2.0.CO%3b2&partnerID=40&md5=2cf5de9bad2a7ec7812efac92dee873a","The object of this paper is to describe and demonstrate the necessity and utility of a coupled atmosphere-fire model: a three-dimensional, time-dependent wildfire simulation model, based on the primitive equations of motion and thermodynamics, that can represent the finescale dynamics of convective processes and capture ambient meteorological conditions. In constructing this coupled model, model resolution for both the atmosphere and the fuel was found to be important in avoiding solutions that are physically unrealistic, and this aspect is discussed. The anelastic approximation is made in the equations of motion, and whether this dynamical framework is appropriate in its usual form for simulating wildfire behavior is also considered. Two simple experiments-the first two in a series of numerical simulations using the coupled atmospherefire model - are presented here, showing the effect of wind speed on fire-line evolution in idealized and controlled conditions. The first experiment considers a 420-m-long fire line, and the second considers a 1500-m-long fire line, where wind speeds normal to the initial fire lines vary from 1 to 5 m s-1. In agreement with some general observations, the short fire line remains stable and eventually develops a single conical shape, providing the wind speed is greater than about 1-2 m s-1, while under similar conditions, the longer fire line breaks up into multiple conical shapes. In both cases, the conical shapes are attributed to a feedback between the hot convective plumes and the near-surface convergence at the fire front. The experimental results reveal a dynamical explanation for fire-line breakup and geometry, demonstrating that the model is a valuable tool with which to investigate fire dynamics, and eventually it may be able to provide a credible scientific basis for policy decisions made by the meteorological and fire-management communities."
"7402435469;","The evolution of dynamical cores for global atmospheric models",2007,"10.2151/jmsj.85B.241","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34848828535&doi=10.2151%2fjmsj.85B.241&partnerID=40&md5=7eb659e6707b81f87d56a793b4fe09a1","The evolution of global atmospheric model dynamical cores from the first developments in the early 1960s to present day is reviewed. Numerical methods for atmospheric models are not straightforward because of the so-called pole problem. The early approaches include methods based on composite meshes, on quasi-homogeneous grids such as spherical geodesic and cubed sphere, on reduced grids, and on a latitude-longitude grid with short time steps near the pole, none of which were entirely successful. This resulted in the dominance of the spectral transform method after it was introduced. Semi-Lagrangian semi-implicit methods were developed which yielded significant computational savings and became dominant in Numerical Weather Prediction. The need for improved physical properties in climate modeling led to developments in shape preserving and conservative methods. Today the numerical methods development community is extremely active with emphasis placed on methods with desirable physical properties, especially conservation and shape preservation, while retaining the accuracy and efficiency gained in the past. Much of the development is based on quasi-uniform grids. Although the need for better physical properties is emphasized in this paper, another driving force is the need to develop schemes which are capable of running efficiently on computers with thousands of processors and distributed memory. Test cases for dynamical core evaluation are also briefly reviewed. These range from well defined deterministic tests to longer term statistical tests with both idealized forcing and complete parameterization packages but simple geometries. Finally some aspects of coupling dynamical cores to parameterization suites are discussed. © 2007, Meteorological Society of Japan."
"7005500582;7006263720;","The processes governing horizontal resolution sensitivity in a climate model",2002,"10.1007/s00382-001-0222-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036333512&doi=10.1007%2fs00382-001-0222-8&partnerID=40&md5=316a6d6f9669195c624b729461ace14b","One of the questions that climate modellers should address is whether their models have sufficient spatial resolution to resolve the physical processes affecting climate. This study addresses this question using the Hadley Centre climate model, HadAM3 (Hadley Centre Atmospheric climate Model version 3, the climate version of the Met Office's Unified Model). The model is run in AMIP2 (Atmospheric Model Intercomparison Project number 2) mode at four resolutions ranging from N48 (2.5° × 3.75°) to N144 (0.833° × 1.25°). The convergence of the model on increasing resolution is evaluated, and the processes leading to resolution sensitivity are investigated in some detail. A parallel set of four dynamical core integrations give an indication of the sensitivity of the dynamics with simple physical parametrization feedback. Increments from individual parametrization schemes during short 'spin-up' integrations with full physics are used to diagnose the sensitivity of individual schemes. The dependency of the results on particular details of the model are also investigated to see how general the results are. Model biases are reduced when resolution is increased. In particular, the troposphere warms, the jets shift polewards, mean sea level pressure over the poles falls, and transient vertical velocity and eddy kinetic energy increase. Some features of the model converge while a number of significant features do not. Non-linearity in both the hydrological cycle and the dynamics play an important role in the lack of convergence."
"7202623257;7401651825;55495120400;","El nino modulation of the South China Sea circulation",1996,"10.1016/S0079-6611(96)00010-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030436125&doi=10.1016%2fS0079-6611%2896%2900010-9&partnerID=40&md5=013d3826546fb6283b75be9a73dbeadc","The South China Sea circulation during the 1982 1983 ENSO (El Nino and Southern Oscillation) event was examined through a combined effort of data analysis and numerical modelling. Monthly wind stress and sea surface temperature fields derived from COADS (Comprehensive Ocean-Atmosphere Data Set) were used to drive a three-dimensional primitive equation ocean model with a free surface. The mean and anomalous circulation fields during 1981-1984 were derived from the model and climatological data. The 1982-1983 El Nino event in the South China Sea began with increased evaporative cooling in late 1982, followed by a weak northeast monsoon in the winter of 1982-1983 and a weak southwest monsoon in the following summer. The surface waters showed persistently higher-than-normal heat content from late 1982 to late 1983. The increased heat content could not be explained by a decrease in latent heat flux. Instead, the surface circulation, which was weaker than normal, played a major role in the increase in sea surface temperature. During maximum warming in October-November 1982, the strengths of both upwelling in the central basin and downwelling around the perimeter of the South China Sea were reduced, resulting in weaker vertical advection of heat and warming of surface waters. Cessation of the year long warming began with the late arrival of the northeast monsoon in October 1983. The record-strength northeast monsoon in November produced anomalous upwelling in the central basin and anomalous downwelling around the perimeter of the marginal sea below the mixed layer. The abnormal vertical motions accelerated vertical advection of heat and returned the circulation and heat flux to normal conditions by December. A similar sequence of events appeared during 1986-1987 with minor variations, suggesting that the scenario may be typical for most ENSO occurrences."
"7404187480;7005245166;","Dynamically consistent, quasi‐hydrostatic equations for global models with a complete representation of the Coriolis force",1995,"10.1002/qj.49712152208","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028973721&doi=10.1002%2fqj.49712152208&partnerID=40&md5=a45d4059a138e51f6d926edeaaa1806e","The spherical polar components of the Coriolis force consist of terms in sin ϕ and terms in cos ϕ, where ϕ is latitude (referred to the frame‐rotation vector as polar axis). The cos ϕ Coriolis terms are not retained in the usual hydrostatic primitive equations of numerical weather prediction and climate simulation, their neglect being consistent with the shallow‐atmosphere approximation and the simultaneous exclusion of various small metric terms. Scale analysis for diabatically driven, synoptic‐scale motion in the tropics, and for planetary‐scale motion, suggests that the cos ϕ Coriolis terms may attain magnitudes of order 10% of those of key terms in the hydrostatic primitive equations. It is argued that the cos ϕ Coriolis terms should be included in global simulation models. A global, quasi‐hydrostatic model having a complete representation of the Coriolis force is proposed. Conservation of axial angular momentum and potential vorticity, as well as energy, is achieved by a formulation in which all metric terms are retained and the shallow‐atmosphere approximation is relaxed. Distance from the centre of the earth is replaced by a pseudo‐radius which is a function of pressure only. This model is put forward as a more accurate alternative to the traditional hydrostatic primitive equations; it preserves the desired conservation laws and may be integrated by broadly similar grid‐point methods. Copyright © 1995 Royal Meteorological Society"
"8948405600;","Seasonal dynamics of the surface circulation in the Southern California Current System",2003,"10.1016/S0967-0645(03)00125-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141677796&doi=10.1016%2fS0967-0645%2803%2900125-5&partnerID=40&md5=4033520d11f1b9d778e866d931657813","The seasonal dynamics of the Southern California Current (SCC) is investigated using a primitive equation ocean model with real coastlines and topography. The model is tested with different wind forcing, and the resulting flow fields are compared to the mean and seasonal circulation inferred from long-term in situ observations (California Cooperative Oceanic Fisheries Investigation (CalCOFI)). The model integration forced with the output winds of a regional atmospheric model (RSM) best captures the statistics of the observed circulation, with a 0.9 correlation coefficient for the streamlines and 0.5 for the velocity fields. The model integrations reveal a pronounced linear response of the flow field to changes in winds on the shelf region. A dynamical feature inferred from CalCOFI hydrography, also suggested in TOPEX/ERS maps, is an annually recurrent westward propagation of SSH anomalies originated in the Southern California Bight (SCB) during the upwelling season. The RSM integration is the only one to capture the correct timing and spatial evolution of this process. We therefore use this model integration for guidance in constructing a dynamical framework to interpret the observed circulation and its variability. During the upwelling season in spring, there is an upward tilt of the isopycnals along the coast directly forced by the winds in the Bight. As the spring transitions to the summer the upwelling winds relax in the Bight but are still strong in the region offshore, approximately in correspondence of the continental slope (positive wind-stress curl condition). Anomalous denser waters in the location of the Southern California Eddy are maintained and reinforced by the combined interaction of the coastal/islands geometry and the wind-stress curl (through Ekman dynamics). The adjustment process to the denser water initiates a westward propagation of ocean density anomaly through Rossby waves, and reinforces the cyclonic gyre-like circulation of the SCE (increasing positive vorticity). Surface poleward flow, maintained by the positive wind-stress curl, is also reinforced in proximity of Point Conception as a consequence of the adjustment. During the summer the cyclonic gyre becomes increasingly unstable as the core of the ocean anomalies crosses the continental slope. Instability processes within the cyclonic region, characterized by a sharp increase in EKE, shed eddies that leave the region either drifting to the west or interacting with existing eddies in the region offshore. The EKE reaches a seasonal maximum at the end the summer in the cyclonic region, and in late fall further offshore where the eddies are fully developed. The shedding of eddies cannot be directly seen in the CalCOFI observations because of the sampling aliasing. For this point we rely on the strong suggestion of the model, which we assume is able to capture the leading order dynamics. Additional integrations with a linearized version of the model are also presented to reinforce our interpretation of the westward propagation of the isopycnal anomalous displacement associated with Rossby wave dynamics. © 2003 Elsevier Ltd. All rights reserved."
"7201839229;9244992800;","The global atmospheric circulation response to tropical diabatic heating associated with the Madden-Julian oscillation during northern winter",2012,"10.1175/2011JAS3686.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855810996&doi=10.1175%2f2011JAS3686.1&partnerID=40&md5=cdaa44136ff65c1976e288c645feb8e7","The detailed dynamical mechanisms of the upper-tropospheric circulation response to the Madden-Julian oscillation (MJO) convection are examined by integrating a primitive equation model. A series of initial-value calculations with the climatological boreal winter background flow forced by the MJO-like thermal forcing successfully capture the key aspects of the observed circulation response to the MJO convection. This suggests that a large fraction of MJO-related circulation anomalies are direct responses to tropical heating in both the tropics and extratropics and can be largely explained by linear dynamics. It is found that MJO-like dipole heatings not only intensify tropical upper-tropospheric anomalies but also weaken them at certain regions because of the interaction between equatorial Kelvin and Rossby waves. The Rossby wave train primarily excited by horizontal divergence of upper-level perturbation flow propagates northeastward and then heads back to the equator. In this way, Rossby wave activity once generated over the subtropical Indian Ocean tends to enhance the equatorial upper-tropospheric anomalies over the tropical Atlantic and West Africa that have already been created by the zonally propagating equatorial Rossby and Kelvin waves. A ray path tracing reveals that a successive downstream development of Rossby wave train mostly results fromthe large-scale waves with zonal waven umbers 2-3 in the Northern Hemisphere and 3-5 in the Southern Hemisphere. The sensitivity tests show that the overall results are quite robust. It is found, however, that the detailed circulation response to the MJO-like forcing is somewhat sensitive to the background flow. This suggests that MJO-related circulation anomalies may have nonnegligible long-term variability and change as background flow varies. © 2012 American Meteorological Society."
"55928817500;26531118000;6603439625;8080847900;16177084000;7006005916;35551194300;35182446000;6602559573;36705143500;55403720400;57205638870;7203013252;","Atmospheric dust modeling from meso to global scales with the online NMMB/BSC-Dust model &ndash; Part 1: Model description, annual simulations and evaluation",2011,"10.5194/acp-11-13001-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80855156446&doi=10.5194%2facp-11-13001-2011&partnerID=40&md5=da3db650afb1010678593dd98aca135b","We describe and evaluate the NMMB/BSC-Dust, a new dust aerosol cycle model embedded online within the NCEP Non-hydrostatic Multiscale Model (NMMB). NMMB is a further evolution of the operational Non-hydrostatic Mesoscale Model (WRF-NMM), which together with other upgrades has been extended from meso to global scales. Its unified non-hydrostatic dynamical core is prepared for regional and global simulation domains. The new NMMB/BSC-Dust is intended to provide short to medium-range weather and dust forecasts from regional to global scales and represents a first step towards the development of a unified chemical-weather model. This paper describes the parameterizations used in the model to simulate the dust cycle including sources, transport, deposition and interaction with radiation. We evaluate monthly and annual means of the global configuration of the model against the AEROCOM dust benchmark dataset for year 2000 including surface concentration, deposition and aerosol optical depth (AOD), and we evaluate the daily AOD variability in a regional domain at high resolution covering Northern Africa, Middle East and Europe against AERONET AOD for year 2006. The NMMB/BSC-Dust provides a good description of the horizontal distribution and temporal variability of the dust. Daily AOD correlations at the regional scale are around 0.6-0.7 on average without dust data assimilation. At the global scale the model lies within the top range of AEROCOM dust models in terms of performance statistics for surface concentration, deposition and AOD. This paper discusses the current strengths and limitations of the modeling system and points towards future improvements. © 2011 Author(s)."
"57089222900;7102101132;","Vortex Rossby waves and hurricane intensification in a barotropic model",1999,"10.1175/1520-0469(1999)056<1674:VRWAHI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344642456&doi=10.1175%2f1520-0469%281999%29056%3c1674%3aVRWAHI%3e2.0.CO%3b2&partnerID=40&md5=de75e3420e1dcee6e90ce37df0bb1352","In this study the balanced evolution of small but finite as well as large-amplitude asymmetries in a rapidly rotating hurricane-like vortex is investigated. In particular, the wave kinematics and wave-mean flow interaction of vortex Rossby waves in a barotropic nonlinear asymmetric balance (AB) model are examined. By diagnosing the evolution of different asymmetric initial potential vorticity (PV) disturbances and their effect on the symmetric vortex, recent linear and quasi-linear predictions are verified and the proposed AB model is shown to be a viable balance model for azimuthal wavenumbers >1. For disturbance amplitudes that are 40% of the basic-state PV at the radius of maximum wind, a discrete normal mode propagating cyclonically around the vortex is excited as a by-product of the process by which energy is transferred from the asymmetries into the basic state (axisymmetrization). In addition we are able to show that even a strong disturbance axisymmetrizes in a circular flow and is able to intensify the basic state. Side-by-side comparison with some experiments from a primitive equation model show good agreement for both weak and strong asymmetric disturbances. The results raise intriguing questions about the dynamical role of discrete and continuous spectrum vortex Rossby waves in the moist convective dynamics of the hurricane. The application of the results to hurricane intensification will be addressed.In this study the balanced evolution of small but finite as well as large-amplitude asymmetries in a rapidly rotating hurricane-like vortex is investigated. In particular, the wave kinematics and wave-mean flow interaction of vortex Rossby waves in a barotropic nonlinear asymmetric balance (AB) model are examined. By diagnosing the evolution of different asymmetric initial potential vorticity (PV) disturbances and their effect on the symmetric vortex, recent linear and quasi-linear predictions are verified and the proposed AB model is shown to be a viable balance model for azimuthal wavenumbers >1. For disturbance amplitudes that are 40% of the basic-state PV at the radius of maximum wind, a discrete normal mode propagating cyclonically around the vortex is excited as a by-product of the process by which energy is transferred from the asymmetries into the basic state (axisymmetrization). In addition we are able to show that even a strong disturbance axisymmetrizes in a circular flow and is able to intensify the basic state. Side-by-side comparison with some experiments from a primitive equation model show good agreement for both weak and strong asymmetric disturbances. The results raise intriguing questions about the dynamical role of discrete and continuous spectrum vortex Rossby waves in the moist convective dynamics of the hurricane. The application of the results to hurricane intensification will be addressed."
"6506100945;35894581100;55924208000;","Ensemble prediction using dynamically conditioned perturbations",1993,"10.1002/qj.49711951005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027430506&doi=10.1002%2fqj.49711951005&partnerID=40&md5=6bdb4a3e5462b902b0a4a9cec0734fb8","We apply the technique developed in the companion paper by Molteni and Palmer (1993) as a means of providing dynamically conditioned perturbations for ensemble forecasting with a primitive‐equation model. Four wintertime initial states are chosen—three at random and one because of substantial development in the large‐scale flow within four days, which the control forecast completely missed. A set of singular vectors are created using a quasi‐geostrophic model linearized about basic states taken from data close to the chosen initial dates. These are interpolated onto the primitive‐equation‐model grid, and used as perturbations to the initial state. An ensemble forecast is made form the perturbed initial states. The dispersion of this ensemble is compared, for each date, with that from a second ensemble with initial perturbations constructed from 6‐hour‐forecast errors. Throughout the forecast period, it is found that the amplitude of the perturbations is noticeably larger using the singular vectors. The dispersion of the ensembles using the forecast‐error perturbations did not indicate that the control forecast form the case with substantial development was likely to be poor. By contrast, the (envelope) dispersion of the ensemble using the singular vectors was notably larger for this case than the other three. A number of members of this ensemble were particularly skilful in predicting weather‐related elements of the flow, such as low‐level temperature change. It is found that the evolution of perturbations which are initially localized over the western Pacific, or western Atlantic, can develop blocking‐like structures several days later over the eastern oceans. With the initial amplitudes used in this paper, the development of these structures is in part nonlinear. The growth of the singular‐vector perturbations was not as large in the primitive‐model as in the quasi‐geostrophic model, probably due to interpolation problems exacerbated by inconsistent orographic representation. Further work to overcome these, and other, problems is indicated. Copyright © 1993 Royal Meteorological Society"
"7202676587;","FINITE-AMPLITUDE ELIASSEN-PALM THEOREM IN ISENTROPIC COORDINATES.",1983,"10.1175/1520-0469(1983)040<1877:AFAEPT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020797463&doi=10.1175%2f1520-0469%281983%29040%3c1877%3aAFAEPT%3e2.0.CO%3b2&partnerID=40&md5=8d13b088274f4e39e84d13555d8caeff","Isentropic coordinates are used to generalize to finite amplitude the celebrated theorem (1. 1) of A. Eliassen and E. Palm under non-acceleration conditions. This primitive-equation result also generalizes thefinite-amplitude quasi-geostrophic result of H. J. Edmon et al. A simple physical interpretation is provided, and a set of transformed Eulerian-mean equations arises naturally in the course of the analysis. Isentropes which intersect the lower boundary need special attention; the technique developed to handle them is a generalization of an idea due to E. N. Lorenz, and may be of use in other contexts. Mention is also made of a version of the theorem valid for small-amplitude, transient, non-conservative disturbances."
"6603145318;7003408439;","Dynamics of 2-day equatorial waves",2004,"10.1175/JAS3352.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-11144289069&doi=10.1175%2fJAS3352.1&partnerID=40&md5=a9aa1d0dc16fdd6c444b8d7781071be2","The dynamics of the 2-day wave, a type of convectively coupled disturbance that frequents the equatorial western Pacific, is examined using observations and a linear primitive equation model. A statistical composite of the wave's kinematic and thermodynamic structure is presented. It is shown that 1) the wave's wind and temperature perturbations can be modeled as linear responses to convective heating and cooling, and 2) the bulk of the wave's dynamical and convective structure can be represented with two vertical modes. The observations and model results suggest that the 2-day wave is an n = 1 westward-propagating inertio-gravity wave with a shallow equivalent depth (14 m) that results from the partial cancelation of adiabatic temperature changes due to vertical motion by convective heating and cooling. © 2004 American Meteorological Society."
"8884425800;35514012200;36785148100;","Seasonal-to-interannual effects of the Indonesian throughflow on the tropical Indo-Pacific Basin",1998,"10.1029/98JC02063","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032531405&doi=10.1029%2f98JC02063&partnerID=40&md5=d4c0cdaa2e2f20b74ec5bc120fcef46f","The effects of the Indonesian throughflow (ITF) are studied in a reduced gravity, primitive equation, sigma coordinate model. The model domain includes the flow south of Australia. Unlike previous studies, this model includes a completely interactive upper ocean hydrology and the surface heat fluxes are provided by coupling the ocean general circulation model (GCM) to an advective atmospheric mixed layer model. It is shown that model simulation of the ITF on seasonal and interannual (1980-1995) timescales is in very good agreement with available estimates and other model studies. Effects of increased mixing in the Indonesian seas are also presented. There is an El Niño-Southern Oscillation (ENSO) related signal in the ITF, but the correlation with the Southern Oscillation Index (SOI) is only -0.31. When the winds over the Indian Ocean are held to climatology, this correlation jumps to -0.65 indicating that the non-ENSO signal in the ITF is caused by the downstream winds. On interannual timescales the ITF can be explained in terms of sea level differences between the western Pacific and eastern Indian Oceans when appropriate representative locations are chosen as demonstrated in both model and TOPEX data. It is shown that the main climatological effect of the ITF is to warm the Indian Ocean and to cool the Pacific. Spreading of the thermocline due to ITF in the Indian Ocean leads to reduced cooling of SST due to upwelling along the coasts of Java, western Australia, and Somalia. The seasonal cycle of sea surface temperature (SST) are shifted in the eastern equatorial Pacific and in the Leeuwin Current region and large-scale dynamic effects of the ITF are also seen. Over the period 1980-1995, the effect of the ITF has interannual variability. While the main ENSO indices, NINO3 and NINO4, are almost identical with and without the ITF, the total SSTs show significant ENSO dependence. SSTs in the central Indian Ocean linked previously to rainfall deficit in the western Australian winter may be dependent on the ENSO related variability of the ITF. © Copyright 1998 by the American Geophysical Union."
"25226875800;7402989545;7102696626;57203012011;55738957800;","Performance of the new NCAR CAM3.5 in East Asian summer monsoon simulations: Sensitivity to modifications of the convection scheme",2010,"10.1175/2010JCLI3022.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955476066&doi=10.1175%2f2010JCLI3022.1&partnerID=40&md5=e19e092f341f943dba137c2e7b62af79","The performance of an interim version of the NCAR Community Atmospheric Model (CAM3.5) in simulating the East Asian summer monsoon (EASM) is assessed by comparing model results against observations and reanalyses. Both the climate mean states and seasonal cycle of major EASM components are evaluated. Special attention is paid to the sensitivity of model performance to changes in the convection scheme. This is done by analyzing four CAM3.5 runs with identical dynamical core and physical packages but different modifications to their convection scheme, that is, the original Zhang-McFarlane (ZM) scheme, Neale et al.'s modification (NZM), Wu et al.'s modification (WZM), and Zhang's modification (ZZM). The results show that CAM3.5 can capture the major climate mean states and seasonal features of the EASM circulation system, including reasonable simulations of the Tibetan high in the upper troposphere and the western Pacific subtropical high (WPSH) in the middle and lower troposphere. The main deficiencies are found in monsoon rainfall and the meridional monsoon cell. The weak meridional land-sea thermal contrasts in the model contribute to the weaker monsoon circulation and to insufficient rainfall in both tropical and subtropical regions of EASM. The seasonal migration of rainfall, as well as the northward jump of the WPSH from late spring to summer, is reasonably simulated, except that the northward jump of the monsoon rain belt still needs improvement. Three runs using modified schemes generally improve the model performance in EASM simulation compared to the control run. The monsoon rainfall distribution and its seasonal variation are sensitive to modifications of the ZM convection scheme, which is most likely due to differences in closure assumptions. NZM, which uses a convective available potential energy (CAPE)-based closure assumption, performs better in tropical regions where the rainfall is closely related to CAPE. However, WZM and ZZM, which use quasi-equilibrium (QE) closure, have more realistic subtropical rainfall in the mei-yu/baiu/changma front region, mainly because the rainfall in the subtropics is more sensitive to the rate of destabilization by the large-scale flow. © 2010 American Meteorological Society."
"56178572000;8391190000;7102762686;7102595308;24462032900;15751583500;7103083539;7005262493;7401460696;7403263977;6701511321;7402332362;7406755458;12761052200;56228733900;8706262900;","Thermosphere extension of the Whole Atmosphere Community Climate Model",2010,"10.1029/2010JA015586","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650010377&doi=10.1029%2f2010JA015586&partnerID=40&md5=e741a90d13feedc84869ba12245f297b","In atmospheric and space environment studies it is key to understand and to quantify the coupling of atmospheric regions and the solar impacts on the whole atmosphere system. There is thus a need for a numerical model that encompasses the whole atmosphere and can self-consistently simulate the dynamic, physical, chemical, radiative, and electrodynamic processes that are important for the Sun-Earth system. This is the goal for developing the National Center for Atmospheric Research (NCAR) Whole Atmosphere Community Climate Model (WACCM). In this work, we report the development and preliminary validation of the thermospheric extension of WACCM (WACCM-X), which extends from the Earth's surface to the upper thermosphere. The WACCM-X uses the finite volume dynamical core from the NCAR Community Atmosphere Model and includes an interactive chemistry module resolving most known neutral chemistry and major ion chemistry in the middle and upper atmosphere, and photolysis and photoionization. Upper atmosphere processes, such as nonlocal thermodynamic equilibrium, radiative transfer, auroral processes, ion drag, and molecular diffusion of major and minor species, have been included in the model. We evaluate the model performance by examining the quantities essential for the climate and weather of the upper atmosphere: the mean compositional, thermal, and wind structures from the troposphere to the upper thermosphere and their variability on interannual, seasonal, and daily scales. These quantities are compared with observational and previous model results. Copyright 2010 by the American Geophysical Union."
"7201554561;7003408439;6603795286;","Three-dimensional structure and dynamics of African easterly waves. Part II: Dynamical modes",2006,"10.1175/JAS3742.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749235194&doi=10.1175%2fJAS3742.1&partnerID=40&md5=e483bd8e0e234bba0de4c363665f684a","A primitive equation model is used to study the linear normal modes of the African easterly jet (AEJ). Reanalysis data from the summertime mean (June-September; JJAS) flow is used to provide zonally uniform and wavy basic states. The structure and growth rates of modes that grow over West Africa on these basic states are analyzed. For zonally uniform basic states, the modes resemble African easterly waves (AEWs) as in many previous studies, but they are quite baroclinic and surface intensified. For wavy basic states the modes have a longitudinal structure determined by the AEJ. They have a surface-intensified baroclinic structure upstream and a deep barotropic structure downstream, as confirmed by energy conversion diagnostics. These modes look remarkably similar to the composite easterly wave structures found by the authors in a companion paper. The similarity extends to the phase relationship of vertical velocity with streamfunction, which resembles OLR composites, suggesting a dynamical influence on convection. Without damping, the mode for the wavy basic state has a growth rate of 0.253 day-1. With a reasonable amount of low-level damping this mode is neutralized. It has a period of 5.5 days and a wavelength of about 3500 km. Further results with monthly mean basic states show slight variations, as the wave packet essentially follows displacements of the jet core. Experiments focused on specific active and passive years for easterly waves (1988 and 1990) do not yield significantly different results for the modes. These results, and in particular, the stability of the system, lead to the conclusion that barotropic-baroclinic instability alone cannot explain the initiation and intermittence of AEWs, and a finite-amplitude initial perturbation is required. © 2006 American Meteorological Society."
"7103060756;37071745600;55910202200;","Mesoscale spectrum of atmospheric motions investigated in a very fine resolution global general circulation model",2008,"10.1029/2008JD009785","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56549115142&doi=10.1029%2f2008JD009785&partnerID=40&md5=17f7b07ac81b41f98c50e58b4d5466dd","The horizontal spectrum of wind variance, conventionally referred to as the kinetic energy spectrum, is examined in experiments conducted with the Atmospheric GCM for the Earth Simulator (AFES) global spectral general circulation model. We find that the control version of AFES run at T639 horizontal spectral resolution simulates a kinetic energy spectrum that compares well at large scales with global observational reanalyses and, at smaller scales, with available aircraft observations at near-tropopause levels. Specifically there is a roughly -3 power-law dependence on horizontal wave number for wavelengths between about 5000 and 500 km, transitioning to a shallower mesoscale regime at smaller wavelengths. This is seen for both one-dimensional spectra and for the two-dimensional total wave number spectrum based on a spherical harmonic analysis. The simulated spectrum at midtropospheric levels is similar in that there is a transition to a shallower mesoscale regime, but the spectrum in the mesoscale is clearly steeper at midtroposphere than near the tropopause. There seem to be no extensive observations of horizontal spectra available in the midtroposphere, so it is not known whether the contrast seen in the model between upper and mid tropospheric levels is realistic. The dependence of the model simulated variability on the subgrid-scale moist convection parameterization is examined. The space-time variability of rainfall is shown to depend strongly on the convection scheme employed. The tropospheric kinetic energy spectrum in the mesoscale seems to be correlated with the precipitation behavior, so that in a version with a more variable precipitation field the kinetic energy in the mesoscale is enhanced. This suggests that the mesoscale motions in the model may be directly forced to a significant extent by the variability in the latent heating field. Experiments were also performed with a dry dynamical core version of the model run at both T639 and T1279 resolutions. This version also simulated a shallow mesoscale range, supporting the view that the mesoscale regime in the atmosphere is energized, at least in part, by a predominantly forward (i.e., downscale) nonlinear spectral cascade. Experiments with various formulations of the hyperdiffusion horizontal mixing parameterization show that the kinetic energy spectrum over about the last half of the resolved wave number range is under strong control by the parameterized mixing. However, the T1279 model simulates almost a decade of the shallow mesoscale regime (i.e., for horizontal wavelengths from about 80 to 500 km) that appears to be fairly independent of the diffusion employed. Finally, experiments are conducted in the dry version to see the effects on the kinetic energy spectrum of changing the thermal Rossby number for the simulations. Copyright 2008 by the American Geophysical Union."
"7202048299;7004014731;","Equatorial wave activity derived from fluctuations in observed convection",1994,"10.1175/1520-0469(1994)051<3791:EWADFF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028667658&doi=10.1175%2f1520-0469%281994%29051%3c3791%3aEWADFF%3e2.0.CO%3b2&partnerID=40&md5=0562444ac6556f5151f987539e2e9e86","The spectrum of equatorial wave activity propagating vertically into the stratosphere is calculated from high-resolution imagery of the global convection pattern. Synoptic Global Cloud Imagery (GCI), constructed from six satellites simultaneously observing the earth, is used to diabatically force the linearized primitive equations. The dynamic response above the heating is evaluated globally in terms of a space-time spectrum of Hough modes, one which includes planetary-scale Kelvin waves, Rossby waves, and gravity waves down to the resolution of the GCL. The geopotential response, which is indicative of temperature fluctuations observed by satellite, is very red in frequency. Therefore, planetary-scale waves with periods longer than two days dominate the spectrum of geopotential, while high-frequency gravity waves make a comparatively small contribution. -from Authors"
"6603638928;7004274115;6602682911;","Singular-vector perturbation growth in a primitive equation model with moist physics",1999,"10.1175/1520-0469(1999)056<1627:SVPGIA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033150077&doi=10.1175%2f1520-0469%281999%29056%3c1627%3aSVPGIA%3e2.0.CO%3b2&partnerID=40&md5=58bf287ddb3fae25240056df529cd6cd","Finite-time growth of perturbations in the presence of moist physics (specifically, precipitation) is investigated using singular vectors (SVs) in the context of a primitive equation regional model. Two difficulties appear in the explicit consideration of the effect of moist physics when studying such optimal growth. First, the tangent-linear description of moist physics may not be as straightforward and accurate as for dry-adiabatic processes; second, because of the consideration of moisture, the design of an appropriate measure of growth (i.e., norm) is subject to even more ambiguity than in the dry situation. In this study both of these problems are addressed in the context of the moist version of the National Center for Atmospheric Research Mesoscale Adjoint Modeling System, version 2, with emphasis on the second problem. Leading SVs are computed in an iterative fashion, using a Lanczos algorithm, for three norms over an optimization interval of 24 h; these norms are based on an expression related to (total) perturbation energy. The properties of these SVs are studied for a case of explosive cyclogenesis and a case of summer convection. The consideration of moisture leads to faster growth of perturbations than in the dry situation, as well as to the appearance of new growing structures. Apparently, moist processes provide for new mechanisms of error growth and do not simply lead to a modulation of SVs obtained with the dry version of the model. Consequently, consideration of the linearized moist processes is essential for revealing all structures that might potentially grow in a moist primitive equation model. In the context of this investigation growth rates depend more on the choice of the basic state and linearized model (moist vs dry) than on the choice of the norm (moist vs dry total energy norm). A reference is cited that supports the validity of the moist tangent-linear SV perturbation growth studied here in the nonlinear regime.Finite-time growth of perturbations in the presence of moist physics (specifically, precipitation) is investigated using singular vectors (SVs) in the context of a primitive equation regional model. Two difficulties appear in the explicit consideration of the effect of moist physics when studying such optimal growth. First, the tangent-linear description of moist physics may not be as straightforward and accurate as for dry-adiabatic processes; second, because of the consideration of moisture, the design of an appropriate measure of growth (i.e., norm) is subject to even more ambiguity than in the dry situation. In this study both of these problems are addressed in the context of the moist version of the National Center for Atmospheric Research Mesoscale Adjoint Modeling System, version 2, with emphasis on the second problem. Leading SVs are computed in an iterative fashion, using a Lanczos algorithm, for three norms over an optimization interval of 24 h; these norms are based on an expression related to (total) perturbation energy. The properties of these SVs are studied for a case of explosive cyclogenesis and a case of summer convection. The consideration of moisture leads to faster growth of perturbations than in the dry situation, as well as to the appearance of new growing structures. Apparently, moist processes provide for new mechanisms of error growth and do not simply lead to a modulation of SVs obtained with the dry version of the model. Consequently, consideration of the linearized moist processes is essential for revealing all structures that might potentially grow in a moist primitive equation model. In the context of this investigation growth rates depend more on the choice of the basic state and linearized model (moist vs dry) than on the choice of the norm (moist vs dry total energy norm). A reference is cited that supports the validity of the moist tangent-linear SV perturbation growth studied here in the nonlinear regime."
"7404187480;7101630970;6603399237;7004069241;","Consistent approximate models of the global atmosphere: Shallow, deep, hydrostatic, quasi-hydrostatic and non-hydrostatic",2005,"10.1256/qj.04.49","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27644541433&doi=10.1256%2fqj.04.49&partnerID=40&md5=580e4305af3263462ae61da900407962","We study global atmosphere models that are at least as accurate as the hydrostatic primitive equations (HPEs), reviewing known results and reporting some new ones. The HPEs make spherical geopotential and shallow atmosphere approximations in addition to the hydrostatic approximation. As is well known, a consistent application of the shallow atmosphere approximation requires omission of those Coriolis terms that vary as the cosine of latitude and of certain other terms in the components of the momentum equation. An approximate model is here regarded as consistent if it formally preserves conservation principles for axial angular momentum, energy and potential vorticity, and (following R. Müller) if its momentum component equations have Lagrange's form. Within these criteria, four consistent approximate global models, including the HPEs themselves, are identified in a height-coordinate framework. The four models, each of which includes the spherical geopotential approximation, correspond to whether the shallow atmosphere and hydrostatic (or quasi-hydrostatic) approximations are individually made or not made. Restrictions on representing the spatial variation of apparent gravity occur. Solution methods and the situation in a pressure-coordinate framework are discussed. © Crown copyright, 2005."
"6603425400;","A theoretical investigation of the sea breeze",1961,"10.1002/qj.49708737203","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0010944168&doi=10.1002%2fqj.49708737203&partnerID=40&md5=793e7713723b2fa9b821faad09f51bea","A primitive equation model is formulated and integrated numerically to study the sea breeze. The formulation is an extension of an atmospheric boundary‐layer model previously developed for a homogeneous terrain. External gravity‐wave type solutions are suppressed by a modelling assumption involving the equation of continuity. The results of an integration showing the evolution of the sea breeze under conditions of no large‐scale synoptic motion are presented. Copyright © 1961 Royal Meteorological Society"
"6603795286;7201554561;7003408439;","Three-dimensional structure and dynamics of African easterly waves. Part III: Genesis",2008,"10.1175/2008JAS2575.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049118029&doi=10.1175%2f2008JAS2575.1&partnerID=40&md5=27213c17d0d356125c8ebfcf72c2f6f9","This paper promotes the view that African easterly waves (AEWs) are triggered by localized forcing, most likely associated with latent heating upstream of the region of observed AEW growth. A primitive equation model is used to show that AEWs can be triggered by finite-amplitude transient and localized latent heating on a zonally varying basic state that is linearly stable. Heating close to the entrance region of the African easterly jet (AEJ) is shown to initiate AEWs downstream. The heating leads to an initial trough that reaches the West African coast about 5-7 days later, depending on the nature of the heating profile. After this, a structure that projects strongly onto the leading linear normal mode of the basic state becomes established, characterized by a number of westward-propagating disturbances that strongly resemble AEWs. The sensitivity of the forced AEWs to the nature and location of the heating profile is examined. AEWs are most efficiently triggered by heating profiles that establish lower tropospheric circulations close to the entrance region of the AEJ. In the present study, this was best achieved by lower tropospheric heating from shallow convection or upper-level heating and lower-level cooling from a stratiform precipitation profile. Both profiles have significant heating gradients in the vertical in the mid-to-lower troposphere. This triggering paradigm for the genesis of AEWs has consequences for the variability and predictability of AEWs at weather and climate time scales. In addition to the nature of the AEJ, often emphasized, it is crucial to consider the nature and variability of upstream heating triggers. © 2008 American Meteorological Society."
"56649979200;56962915800;8930075400;14050692300;55976016100;6701344406;","Centennial variations of the global monsoon precipitation in the last millennium: Results from ECHO-G model",2009,"10.1175/2008JCLI2353.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66849122037&doi=10.1175%2f2008JCLI2353.1&partnerID=40&md5=fa5ee1fe1664abbead59a3c38b1e7d19","The authors investigate how the global monsoon (GM) precipitation responds to the external and anthropogenic forcing in the last millennium by analyzing a pair of control and forced millennium simulations with the ECHAM and the global Hamburg Ocean Primitive Equation (ECHO-G) coupled ocean-atmosphere model. The forced run, which includes the solar, volcanic, and greenhouse gas forcing, captures the major modes of precipitation climatology comparably well when contrasted with those captured by the NCEP reanalysis. The strength of the modeled GM precipitation in the forced run exhibits a significant quasibicentennial oscillation. Over the past 1000 yr, the simulated GM precipitation was weak during the Little Ice Age (1450-1850) with the three weakest periods occurring around 1460, 1685, and 1800, which fell in, respectively, the Spörer Minimum, Maunder Minimum, and Dalton Minimum periods of solar activity. Conversely, strong GM was simulated during the model Medieval Warm Period (ca. 1030-1240). Before the industrial period, the natural variations in the total amount of effective solar radiative forcing reinforce the thermal contrasts both between the ocean and continent and between the Northern and Southern Hemispheres resulting in the millennium-scale variation and the quasi-bicentennial oscillation in the GM index. The prominent upward trend in the GM precipitation occurring in the last century and the notable strengthening of the global monsoon in the last 30 yr (1961-90) appear unprecedented and are due possibly in part to the increase of atmospheric carbon dioxide concentration, though the authors' simulations of the effects from recent warming may be overestimated without considering the negative feedbacks from aerosols. The simulated change of GM in the last 30 yr has a spatial pattern that differs from that during the Medieval Warm Period, suggesting that global warming that arises from the increases of greenhouse gases and the input solar forcing may have different effects on the characteristics of GM precipitation. It is further noted that GM strength has good relational coherence with the temperature difference between the Northern and Southern Hemispheres, and that on centennial time scales the GM strength responds more directly to the effective solar forcing than the concurrent forced response in global-mean surface temperature. © 2009 American Meteorological Society."
"7402761465;56962915800;","Low-frequency equatorial waves in vertically sheared zonal flow. Part II: Unstable waves",1996,"10.1175/1520-0469(1996)053<3589:LFEWIV>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030324395&doi=10.1175%2f1520-0469%281996%29053%3c3589%3aLFEWIV%3e2.0.CO%3b2&partnerID=40&md5=742a137b034f1f77ed471cc188f4fc95","The stability of equatorial Rossby waves in the presence of mean flow vertical shear and moisture convergence-induced heating is investigated with a primitive equation model on an equatorial β plane. A vertical shear alone can destabilize equatorial Rossby waves by feeding mean flow available potential energy to the waves. This energy transfer necessitates unstable waves' constant phase lines tilt both horizontally (eastward with latitude) and vertically (against the shear). The preferred most unstable wavelength increases with increasing vertical shear and with decreasing heating intensity, ranging typically from 3000 to 5000 km. The instability strongly depends on meridional variation of the vertical shear. A broader meridional extent of the shear allows a faster growth and a less-trapped meridional structure. When the shear is asymmetric relative to the equator, the unstable Rossby wave is constrained to the hemisphere where the shear is prominent. Without boundary layer friction the Rossby wave instability does not depend on the sign of the vertical shear, whereas in the presence of the boundary layer, the moist Rossby wave instability is remarkably enhanced (suppressed) by easterly ( westerly ) vertical shears. This results from the fact that an easterly shear confines the wave to the lower level, generating a stronger Ekman-pumping-induced heating and an enhanced meridional heat flux, both of which reinforce the instability. The moist baroclinic instability is a mechanism by which westward propagating rotational waves (Rossby and Yanai waves) can be destabilized, whereas Kelvin waves cannot. This is because the transfer of mean potential energy to eddy requires significant magnitude of barotropic motion. The latter is a modified Rossby wave and can be resonantly excited only by the westward propagating rotational waves. The common features and differences of the equatorial Rossby wave instability and midlatitude baroclinic instability, as well as the implications of the results are discussed."
"7101772062;6603187267;","A numerical model of the zonal mean circulation of the middle atmosphere",1980,"10.1007/BF01586455","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000928498&doi=10.1007%2fBF01586455&partnerID=40&md5=86f2dc62f62ab503b451913b07ac21fb","The annual cycle of the zonally averaged circulation in the middle atmosphere (16-96 km) is simulated using a numerical model based on the primitive equations in log pressure coordinates. The circulation is driven radiatively by heating due to solar ultraviolet absorption by ozone and infrared cooling due to carbon dioxide and ozone (parameterized as a Newtonian cooling). Since eddy fluxes due to planetary waves are neglected in the model, the computed mean meridional circulation must be interpreted as the diabatic circulation, not as the total eulerian mean. Rayleigh friction with a short (2-4 day) time constant above 70 km is included to simulate the strong mechanical dissipation which is hypothesized to exist in the vicinity of the mesopause due to turbulence associated with gravity waves and tides near the mesopause. Computed mean winds and temperatures are in general agreement with observations for both equinox and solstice conditions. In particular, the strong mechanical damping specified near the mesopause makes it possible to simulate the cold summer and warm winter mesopause temperatures without generating excessive mean zonal winds. In addition, the model exhibits a strong semiannual cycle in the mean zonal wind at the equator, with both amplitude and vertical structure in agreement with the easterly phase of the observed equatorial semiannual oscillation. © 1980 Birkhäuser Verlag."
"7004922359;57204410953;","A model simulation of circulation in the northeast Atlantic shelves and seas",1992,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027044683&partnerID=40&md5=4517b480de4bd5107fedcd54982e196b","A three-dimensional, primitive-equation simulation of the circulation in the northeast Atlantic shelves and seas, defined by 51°-76°N latitudes and 20°W-22°E longitudes, has been conducted for the period February-March 1988. The simulation was initialized from a 585-day quasi-equilibrium calculation and included realistic meteorological forcing, inflows/outflows across the open boundaries, tides, coastal and Baltic discharges, and relaxation to wintertime climatology for model depths >500 m. The calculation is the first part of an overall effort to nest a high-resolution region for simulation of eddies and fronts in the Norwegian Coastal Current. This paper presents detailed simulation strategies and discusses results from the coarse-grid region to study the larger-scale model response induced by atmospheric forcing. -from Authors"
"8285351400;7004890337;","Intermediate models of planetary circulations in the atmosphere and ocean.",1980,"10.1175/1520-0469(1980)037<1657:IMOPCI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019193761&doi=10.1175%2f1520-0469%281980%29037%3c1657%3aIMOPCI%3e2.0.CO%3b2&partnerID=40&md5=ee2ab3fdf202772e94879058a40379ad","An extensive discussion is made of models intermediate between the quasi-geostrophic and primitive ones, some of which have been previously proposed and some of which are derived here. Further progress in the search for intermediate models requires obtaining an extensive set of solutions for these models for comparison with quasi-geostrophic and primitive equation solutions. -from Authors"
"7406671641;","Forced planetary wave response in a thermocline gyre",1999,"10.1175/1520-0485(1999)029<1036:FPWRIA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032750724&doi=10.1175%2f1520-0485%281999%29029%3c1036%3aFPWRIA%3e2.0.CO%3b2&partnerID=40&md5=6c08f25ee9ef34fb10fb3d7c33963f95","The response of a thermocline gyre to anomalies in surface wind stress forcing and surface buoyancy forcing is investigated in light of planetary wave dynamics, both analytically and numerically. The author's theory suggests that anomalous Ekman pumping most efficiently generates the non-Doppler-shift mode, which resembles the first baroclinic mode and has the clearest signal in the sea surface height field and the lower thermocline temperature field. The non-Doppler-shift mode propagates westward rapidly regardless of the mean circulation. In contrast, anomalous surface buoyancy forcing, which can be simulated by an entrainment velocity, produces the strongest response in the advective mode, which resembles the second baroclinic mode and has the largest signature in the upper thermocline temperature field. The advective mode tends to propagate in the direction of the subsurface flow, but its propagation speed may differ substantially from that of the mean flow. The theory is further substantiated by numerical experiments in three ocean models: a 3-layer eddy-resolving quasigeostrophic model, a 2.5-layer primitive equation model, and an oceanic general circulation model. Finally, relevance of the theory to recent observations of decadal variability in the upper ocean and the climate system is also discussed."
"7202364010;","On the dynamical basis for the Asian summer monsoon rainfall-El Nino relationship",1994,"10.1175/1520-0442(1994)007<1750:OTDBFT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028604837&doi=10.1175%2f1520-0442%281994%29007%3c1750%3aOTDBFT%3e2.0.CO%3b2&partnerID=40&md5=28a3c712475bc2383b3f76515066983a","The contrasting monsoon circulation during recent El Nino (1987) and La Nina (1988) years is first simulated using orography and the residually diagnosed heating (from the thermodynamic equation and the uninitialized, but mass-balanced, ECMWF analyses) as forcings, and then analyzed to provide insight into the importance of various regional forcings, such as the El Nino-related heating anomalies over the tropical Indian and Pacific Oceans. The dynamical diagnostic analysis of the anomalous circulation during 1987 and 1988 March-May and June-August periods shows the orographically forced circulation anomaly (due to changes in the zonally averaged basic-state flow) to be quite dominant in modulating the low-level moisture-flux convergence and hence monsoon rainfall over Indochina. The El Nino-related persistent (spring-to-summer) heating anomalies over the tropical Pacific and Indian Ocean basins, on the other hand, mostly regulate the low-level westerly monsoon flow intensity over equatorial Africa and the northern Indian Ocean and, thereby, the large-scale moisture flux into Sahel and Indochina. -from Author"
"10638998700;7006673063;7202583613;","Model-predicted distribution of wind-induced internal wave energy in the world's oceans",2008,"10.1029/2008JC004768","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57049119116&doi=10.1029%2f2008JC004768&partnerID=40&md5=1dc0884c9dd5f0d5813241582956fdad","The distribution of wind-induced internal wave energy in the world's oceans is investigated using a full three-dimensional primitive equation model. Special attention is directed to the global energy input to the surface near-inertial motions and the subsequent downward energy propagation into the deep ocean. We find that the model results for near-inertial energy in the oceanic mixed layer, depth-integrated horizontal energy fluxes, and vertical structures of WKB-scaled kinetic energy are all consistent with the available observations in the regions of significant wind energy input and that the annual mean of the global wind energy input becomes ∼0.4 TW. It is also found that most of the wind-induced energy resides in high vertical modes, 75-85% of which is dissipated in the surface 150 m. The present study therefore predicts that the total wind-induced near-inertial energy available for deep-ocean mixing is limited to, at most, 0.1 TW, which is an order of magnitude smaller than previously estimated. Adding the energy flux from tide-topography interactions of ∼0.9 TW, we can conclude that the total energy available for deep-ocean mixing is ∼1.0 TW, obviously falling short of the required power to sustain the global overturning circulation. This might suggest the existence of other important energy sources, such as the one through geostrophic adjustment processes, and/ or additional mechanisms sustaining the global overturning circulation, such as effects of Ekman upwellig in the Southern Ocean. Another possibility is that previous estimates of the volume transport of the global overturning circulation might be too large. Copyright 2008 by the American Geophysical Union."
"35576886500;7102620639;35588602200;","Simulations of radiocarbon in a coarse-resolution world ocean model. 2. Distributions of bomb-produced carbon 14",1989,"10.1029/JC094iC06p08243","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024371020&doi=10.1029%2fJC094iC06p08243&partnerID=40&md5=a7f30b995c11a2390da6355568c473da","Part 1 of this study examined the ability of the Geophysical Fluid Dynamics Laboratory (GFDL) primitive equation ocean general circulation model to simulate the steady state distribution of naturally produced 14C in the ocean prior to the nuclear bomb tests of the 1950s and early 1960s. In part 2 we begin with the steady state distributions of part 1 and subject the model to the pulse of elevated atmospheric 14C concentrations observed since the 1950s. This study focuses on the processes and time scales which govern the transient distributions of bomb 14C in the upper kilometer of the ocean. Model projections through 1990 are compared with observations compiled by the Geographical Ocean Sections Study (GEOSECS) in 1972, 1974, and 1978; the Transient Tracers in the Ocean (TTO) expedition in 1981, and the French INDIGO expeditions in 1985-1987. In their analysis of the GEOSECS 14C observations, Broecker et al. (1985) noted that much of the bomb 14C which entered the ocean's equatorial belts prior to GEOSECS accumulated the adjacent subtropical zones. Broecker et al. argued that this displacement of bomb 14C inventories was caused by the wind-driven upwelling and surface divergence in the tropics combined with convergent flow and downwelling in the subtropics. Similar displacements were invoked to shift bomb 14C from the Antarctic circumpolar region into the southern temperate zone. The GFDL model successfully reproduces the observed GEOSECS inventories, but then predicts a significantly different pattern of bomb 14C uptake in the decade following GEOSECS. The post-GEOSECS buildup of bomb 14C inventories is largely confined to the subthermocline layers of the North Atlantic, the lower thermocline of the southern hemisphere, and down to 2000 m in the circumpolar region. A great deal of attention is devoted to detailed comparisons between the model and the available radiocarbon data. A number of flaws in the model are highlighted by this analysis. The Subantarctic Mode Waters forming along the northern edge of the circumpolar current are identified as a very important process for carrying bomb 14C into the thermoclines of the southern hemisphere. The model concentrates its mode water formation in a single sector of the circumpolar region and consequently fails to form its mode waters with the correct T-S properties. The model also moves bomb 14C into the deep North Atlantic and deep circumpolar region much too slowly."
"35510247100;7402598368;7007058398;","Oceanic restratification forced by surface frontogenesis",2006,"10.1175/JPO2923.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749684094&doi=10.1175%2fJPO2923.1&partnerID=40&md5=13c6acdd43db68c1f13288832761adef","Potential vorticity (PV) conservation implies a strong constraint on the time evolution of the mean density at a given depth. The authors show that, on an f plane and in the absence of sources and sinks of PV, it only depends on two terms, namely, the time evolution of the product between density anomaly and relative vorticity and the vertical PV flux. This primitive equation result, which applies at any depth, suggests that the ageostrophic dynamics induced by baroclinic eddies strongly affect the mean oceanic stratification profile. This result is illustrated for two simple initial-value simulations of a baroclinic, balanced jet. For initial situations propitious to surface frontogenesis, the simulations show a restratification over the whole water column characterized by the amplification in time of the Brunt-Väisälä frequency in the upper oceanic layers. In the absence of surface frontogenesis, such as when the jet is initialized at the middepth of the water column, the restratification is much weaker and slower. Because both simulations have similar kinetic energy and growth rate of baroclinic instability, the results clearly reveal that the restratification is driven by surface frontogenesis in the first case and by vertical PV flux in the interior in the second case. The authors also point out that the dynamics of the interior PV is tightly related to the surface dynamics because of total mass conservation. © 2006 American Meteorological Society."
"7101739466;7102625188;","Potential vorticity inversion on a hemisphere",2000,"10.1175/1520-0469(2000)057<1214:PVIOAH>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034039453&doi=10.1175%2f1520-0469%282000%29057%3c1214%3aPVIOAH%3e2.0.CO%3b2&partnerID=40&md5=208eea97949511750d49cc2782a7c3e8","Several different kinds of accurate potential vorticity (PV) inversion operators, and the associated balanced models, are tested for the shallow water equations on a hemisphere in an attempt to approach the ultimate limitations of the balance, inversion, and slow-manifold concepts. The accuracies achieved are far higher than for standard balanced models accurate to one or two orders in Rossby number R or Froude number F (where F = |u|/c; |u| = flow speed: and c = gravity wave speed). Numerical inversions, and corresponding balanced-model integrations testing cumulative accuracy, are carried out for cases that include substantial PV anomalies in the Tropics. The balanced models in question are constructed so as to be exactly PV conserving and to have unique velocity fields (implying, incidentally, that they cannot be Hamiltonian). Mean layer depths of 1 and 2 km are tested. The results show that, in the cases studied, the dynamical information contained in PV distributions is remarkably close to being complete even though R = ∞ at the equator and even though local maximum Froude numbers, Fmax, approach unity in some cases. For example, in a 10-day integration of the balanced model corresponding to one of the most accurate inversion operators, `third-order normal mode inversion,' the mean depth was 1 km, the minimum depth less than 0.5 km, and Fmax &amp;APEQ 0.7, hardly small in comparison with unity. At the end of 10 days of integration, the cumulative rms error in the layer depth was less than 15 m, that is, less than 5% of the typical rms spatial variation of 310 m. At the end of the first day of integration the rms error was 5 m, that is, less than 2%. Here `error' refers to a comparison between the results of a balanced integration and those of a corresponding primitive equation integration initialized to have low gravity wave activity on day 0. Contour maps of the PV distributions remained almost indistinguishable by eye over the 10-day period. This remarkable cumulative accuracy, far beyond anything that could have been expected from standard scale analysis, is probably related to the weakness of the spontaneous-adjustment emission or `Lighthill radiation' studied in the companion paper by Ford et al.Several different kinds of accurate potential vorticity (PV) inversion operators, and the associated balanced models, are tested for the shallow water equations on a hemisphere in an attempt to approach the ultimate limitations of the balance, inversion, and slow-manifold concepts. The accuracies achieved are far higher than for standard balanced models accurate to one or two orders in Rossby number R or Froude number F (where F = |u|/c; |u| = flow speed; and c = gravity wave speed). Numerical inversions, and corresponding balanced-model integrations testing cumulative accuracy, are carried out for cases that include substantial PV anomalies in the Tropics. The balanced models in question are constructed so as to be exactly PV conserving and to have unique velocity fields (implying, incidentally, that they cannot be Hamiltonian). Mean layer depths of 1 and 2 km are tested. The results show that, in the cases studied, the dynamical information contained in PV distributions is remarkably close to being complete even though R = ∞ at the equator and even though local maximum Froude numbers, F(max), approach unity in some cases. For example, in a 10-day integration of the balanced model corresponding to one of the most accurate inversion operators, 'third-order normal mode inversion,' the mean depth was 1 km, the minimum depth less than 0.5 km, and F(max) ~ 0.7, hardly small in comparison with unity. At the end of 10 days of integration, the cumulative rms error in the layer depth was less than 15 m, that is, less than 5% of the typical rms spatial variation of 310 m. At the end of the first day of integration the rms error was 5 m, that is, less than 2%. Here 'error' refers to a comparison between the results of a balanced integration and those of a corresponding primitive equation integration initialized to have low gravity wave activity on day 0. Contour maps of the PV distributions remained almost indistinguishable by eye over the 10-day period. This remarkable cumulative accuracy, far beyond anything that could have been expected from standard scale analysis, is probably related to the weakness of the spontaneous-adjustment emission or 'Lighthill radiation' studied in the companion paper by Ford et al."
"57203174793;7006001675;7801340314;35493743100;7005137442;8698322600;55165863400;","Atmospheric pCO2 sensitivity to the biological pump in the ocean",2000,"10.1029/1999GB001216","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034456040&doi=10.1029%2f1999GB001216&partnerID=40&md5=35861f15420720e5cf2f0fa7c2f61026","In models of the global carbon cycle, the pCO2 of the atmosphere is more sensitive to the chemistry of the high-latitude surface ocean than the tropical ocean. Because sea-surface nutrient concentrations are generally high in the high latitudes, pCO2 sensitivity to high-latitude forcing also determines pCO2 sensitivity to the biological pump globally. We diagnose high-latitude sensitivity of a range of ocean models using atmospheric pCO2 above an abiotic ocean; cold high-latitude waters pull abiotic pCO2 to low values. Box models are very high-latitude sensitive, while most global circulation models are considerably less so, including a two-dimensional overturning model, two primitive equation models, the Hamburg class of large scale geostrophic (LSG) general circulation models (GCMs), and the MICOM isopycnic GCM. High-latitude forcing becomes more important in a depth-coordinate GCM when lateral diffusion is oriented along isopycnal surfaces, rather than horizontally, following Redi [1982]. In two different GCMs (a primitive equation model and LSG), addition of the Gent and McWilliams [1990] isopycnal thickness diffusion scheme had only minor impact on high-latitude sensitivity. Using a simplified box model, we show that high-latitude sensitivity depends on a high-latitude monopoly on deep water formation. In an attempt to bridge the gap between box models and GCMs, we constructed a simple slab overturning model with an imposed stream function which can be discretized at arbitrary resolution from box model to GCM scale. High-latitude sensitivity is independent of model resolution but very sensitive to vertical diffusion. Diffusion acts to break the high-latitude monopoly, decreasing high-latitude sensitivity. In the isopycnal GCM MICOM, however, high-latitude sensitivity is relatively insensitive to diapycnal diffusion of tracers such as CO2. This would imply that flow pathways in MICOM take the place of vertical diffusion in the slab model. The two nominally most sophisticated ocean models in the comparison are the isopycnal model MICOM and the depth-coordinate GCM with Redi [1982] and Gent and McWilliams [1990] mixing. Unfortunately, these two models disagree in their abiotic CO2 behavior; the depth-coordinate isopycnal mixing GCM is high-latitude sensitive, in accord with box models, while MICOM is less so. The rest of the GCMs, which have historically seen the most used in geochemical studies, are even less high-latitude sensitive than MICOM. This discrepancy needs to be resolved. In the meantime, the implication of the MICOM/traditional GCM result would be that box models overestimate high-latitude sensitivity of the real ocean. This would eliminate iron dust fertilization of the ocean as an explanation for the glacial pCO2 range of 180-200 uatm [Archer et al., 2000]."
"7201785152;37019381400;55686667100;","Dynamics of synoptic eddy and low-frequency flow interaction. Part I: A linear closure",2006,"10.1175/JAS3715.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746912651&doi=10.1175%2fJAS3715.1&partnerID=40&md5=70fe1f39ca15c3d1c9e42c06adf3837f","The interaction between synoptic eddy and low-frequency flow (SELF) has been recognized for decades to play an important role in the dynamics of the low-frequency variability of the atmospheric circulation. In this three-part study a linear framework with a stochastic basic flow capturing both the climatological mean flow and climatological measures of the synoptic eddy flow is proposed. Based on this linear framework, a set of linear dynamic equations is derived for the ensemble-mean eddy forcing that is generated by anomalous time-mean flows. By assuming that such dynamically determined eddy-forcing anomalies approximately represent the time-mean anomalies of the synoptic eddy forcing and by using a quasi-equilibrium approximation, an analytical nonlocal dynamical closure is obtained for the two-way SELF feedback. This linear closure, directly relating time-mean anomalies of the synoptic eddy forcing to the anomalous time-mean flow, becomes an internal part of a new linear dynamic system for anomalous time-mean flow that is referred to as the low-frequency variability of the atmospheric circulation in this paper. In Part I, the basic approach for the SELF closure is illustrated using a barotropic model. The SELF closure is tested through the comparison of the observed eddy-forcing patterns associated with the leading low-frequency modes with those derived using the SELF feedback closure. Examples are also given to illustrate an important role played by the SELF feedback in regulating the atmospheric responses to remote forcing. Further applications of the closure for understanding the dynamics of low-frequency modes as well as the extension of the closure to a multilevel primitive equation model will be given in Parts II and III, respectively. © 2006 American Meteorological Society."
"6602858513;6602230359;7202208382;","Modeling the atmospheric general circulation using a spherical geodesic grid: A new class of dynamical cores",2000,"10.1175/1520-0493(2000)128<2471:mtagcu>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033832359&doi=10.1175%2f1520-0493%282000%29128%3c2471%3amtagcu%3e2.0.co%3b2&partnerID=40&md5=b67e4ddf48de6bec97a8336a5ceede50","This paper documents the development and testing of a new type of atmospheric dynamical core. The model solves the vorticity and divergence equations in place of the momentum equation. The model is discretized in the horizontal using a geodesic grid that is nearly uniform over the entire globe. The geodesic grid is formed by recursively bisecting the triangular faces of a regular icosahedron and projecting those new vertices onto the surface of the sphere. All of the analytic horizontal operators are reduced to line integrals, Which are numerically evaluated with second-order accuracy. In the vertical direction the model can use a variety of coordinate systems, including a generalized sigma coordinate that is attached to the top of the boundary layer. Terms related to gravity wave propagation are isolated and an efficient semi-implicit time-stepping scheme is implemented. Since this model combines many of the positive attributes of both spectral models and conventional finite-difference models into a single dynamical core, it represents a distinctively new apporach to modeling the atmosphere's general circulation. The model is tested using the idenlized forcing proposed by Held and Suarez. Results are presented for simulations using 2562 polygons (approximately 4.5° × 4.5°) and using 10 242 polygons (approximately 2.25° × 2.25°). The results are compared to those obtained with spectral model simulation truncated at T30 and T63. In terms of first and second moments of state variables such as the zonal wind, and temperature, In terms of first and second moments of state variables such as the zonal wind, meridional wind, and temperature, the geodesic grid model results using 2562 polygons are comparable to those of a spectral model truncated at slightly less than T30, while a simulation with 10 242 polygons is comparable to a spectral model simulation truncated at slightly less than T63. In order to further demonstrate the viability of this modeling approach, preliminary results obtained from a full-physics general circulation model that uses this dynamical core are presented. The dominant features of the DJF climate are captured in the full-physics simulation. In terms of computational efficiency, the geodesic grid model is somewhat slower than the spectral model used for comparison. Model timings completed on an SGI Origin 2000 indicate that the geodesic grid model with 10 242 polygons is 20% slower than the spectral model truncated at T63. The geodesic grid model is more competitive at higher resolution than at lower resolution, so further optimization and future trends toward higher resolution should benefit the geodesic grid model."
"35566896300;","Sensitivity of optimal unstable structures",1994,"10.1002/qj.49712051609","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028582474&doi=10.1002%2fqj.49712051609&partnerID=40&md5=6528dbe09216dd31cbc0d13175c8b6cd","Optimal unstable perturbations, i.e. structures that grow fastest over a finite time interval, can be used in numerical weather prediction to construct the initial conditions of an ensemble of integrations. Optimal perturbations superimposed on a basic state provide a representation of the uncertainty of the initial state of the atmospheric flow. The computation of the fastest‐growing perturbations over a finite time interval can be achieved in the linear approximation by using the forward and adjoint tangent version of a full nonlinear model. Previous results, obtained using a version of a primitive‐equation model with a reasonable horizontal and vertical resolution, showed that the lack of parametrization of turbulent processes can lead to fast‐growing perturbations characterized by ‘non‐meteorological’ structures. The first part of this paper focuses on this problem. Numerical experiments have been performed to study the impact of a simple surface‐drag and vertical‐diffusion scheme on the most unstable perturbations. It is shown how the very simple parametrization of the turbulent processes implemented inhibits the growth of non‐meteorological structures close to the surface. A second very important problem to face when constructing the initial conditions of an ensemble of forecasts, using optimal perturbations, is the definition of the optimization time interval over which the growth of these unstable structures is maximized. This problem will be investigated in the second part of this work, where the impact of the optimization time interval on the definition of the unstable sub‐space is studied for time periods up to three days. Results from different cases seem to indicate that unstable sub‐spaces computed with an optimization time interval longer than 36 hours are very similar. Copyright © 1994 Royal Meteorological Society"
"7102315560;7004010406;","Interdecadal changes in southern hemisphere winter storm track modes",2007,"10.1111/j.1600-0870.2007.00264.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548718204&doi=10.1111%2fj.1600-0870.2007.00264.x&partnerID=40&md5=4e87a9e47b8a3dd99f55ae5226711ccc","The interdecadal changes in southern hemisphere (SH) winter cyclogenesis have been studied using a global two-level primitive equation instability-model with reanalysed observed July three-dimensional basic states for the periods 1949-1968 and 1975-1994. The early to mid-1970s were a time of quite dramatic reduction in the winter rainfall in the southwest of western Australia (SWWA). We find that the rainfall reduction is associated with a decrease in the vertical mean meridional temperature gradient and in the peak upper tropospheric jet-stream zonal winds near 30° south throughout most of the SH. These changes are reflected in the properties of the leading SH cyclogenesis modes: for 1975-1994 both the fastest growing mode, and on average the 10 leading SH cyclogenesis modes that cross Australia, have growth rates which are around 30% smaller than for the corresponding modes for 1949-1968. The sensitivity of our results, to the strengths of physical parametrizations and to the choice of basic states based on different data sets, is examined. Our results suggest that a primary cause of the rainfall reduction over SWWA in the period after 1975 is the reduction of the intensity of cyclogenesis and the southward deflection of some storms. © 2007 The Authors Journal compilation © 2007 Blackwell Munksgaard."
"7006614214;56409049800;7004534048;7202784101;57207596869;36783204100;","The Explicit Planetary Isentropic-Coordinate (EPIC) Atmospheric Model",1998,"10.1006/icar.1998.5917","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000309522&doi=10.1006%2ficar.1998.5917&partnerID=40&md5=51254abc1fe06e0202e38f777616bb98","We describe a new general circulation model (GCM) designed for planetary atmospheric studies called the EPIC model. This is a finite-difference model based on the isentropic-coordinate scheme of Hsu and Arakawa (1990.Mon. Wea. Rev.118, 1933-1959). We report on previously undocumented modifications, additions, and key practical issues that experience running the model has revealed to be important. The model integrates the hydrostatic primitive equations, which are valid for large-scale atmospheric dynamics and include gravity waves (buoyancy waves), planetary waves (Rossby waves), and horizontally propagating sound waves (Lamb waves), but not vertically propagating sound waves because of the hydrostatic approximation. The vertical coordinate is entropy in the form of potential temperature, which coincides with material surfaces for adiabatic motion. This means that there is no vertical velocity except where there is heating, which improves accuracy and helps the model maintain conservation properties over long integrations. An isentropic vertical coordinate is natural for the atmospheres of Jupiter, Saturn, Uranus, and Neptune, which are believed to have essentially adiabatic interiors that match up with the bottom of the model and is also excellent for middle-atmosphere studies on any planet. Radiative processes are parameterized by Newtonian cooling, and the latent heat of ortho-para hydrogen conversion is included when appropriate, with a suitably defined mean potential temperature. The model is written with general map factors that make it easy to configure in oblate spherical, cylindrical, or Cartesian coordinates. The code includes optional Message Passing Interface (MPI) library calls and hence runs on any Unix-based parallel computer or network cluster. An optional graphical user interface to commercial visualization software facilitates control of the model and analysis of output. Memory is allocated dynamically such that the user does not recompile to change horizontal or vertical resolution or range. Applications to date include comet impact forecasts and hindcasts for Jupiter, meridional circulation studies of Uranus and Neptune, and the accompanying paper on three-dimensional simulations of Neptune's Great Dark Spot (1998.Icarus132, 239-265). © 1998 Academic Press."
"15743213500;7004678994;6602856965;","Seasonal variability of the South Equatorial Current bifurcation in the Atlantic Ocean: A numerical study",2007,"10.1175/JPO2983.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846996017&doi=10.1175%2fJPO2983.1&partnerID=40&md5=71eed35ec6f391880438c264b1131de5","In this study, a reduced-gravity, primitive equation OGCM is used to investigate the seasonal variability of the bifurcation of the South Equatorial Current (SEC) into the Brazil Current (BC) to the south and the North Brazil Undercurrent/Current (NBUC/NBC) system to the north. Annual mean meridional velocity averaged within a 2° longitude band off the South American coast shows that the SEC bifurcation occurs at about 10°-14°S near the surface, shifting poleward with increasing depth, reaching 27°S at 1000 m, in both observations and model. The bifurcation latitude reaches its southernmost position in July (∼17°S in the top 200 m) and its northernmost position in November (∼13°S in the top 200 m). The model results show that most of the seasonal variability of the bifurcation latitude in the upper thermocline is associated with changes in the local wind stress curl due to the annual north-south excursion of the marine ITCZ complex. As the SEC bifurcation latitude moves south (north) the NBUC transport increases (decreases) and the BC transport decreases (increases). The remote forcing (i.e., westward propagation of anomalies) appears to have a smaller impact on the seasonal variability of the bifurcation in the upper thermocline. © 2007 American Meteorological Society."
"8152726300;","A shallow CISK, deep equilibrium mechanism for the interaction between large-scale convection and large-scale circulations in the tropics",2003,"10.1175/1520-0469(2003)060<0377:ASCDEM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042643568&doi=10.1175%2f1520-0469%282003%29060%3c0377%3aASCDEM%3e2.0.CO%3b2&partnerID=40&md5=e602ba69042d549d8910aadc92d88d61","In this paper, the circulations driven by deep heating and shallow heating are investigated through analytically solving a set of linear equations and examining circulations simulated by a dry primitive equation model. Special emphasis is placed on the low-level mass (moisture) convergence associated with the forced circulation and the maintenance of the shallow and deep heat sources. It is found that the forced circulation driven by shallow heating is more likely to be trapped horizontally near the heating area but relatively extended in the vertical. As a consequence, diabatic heating cannot balance adiabatic cooling due to upward motion. At the levels slightly above the top of the heating, a negative vertical gradient of temperature perturbation appears. For the atmosphere driven by deep heating, however, the temperature perturbation cannot accumulate because the heating signals propagate away very fast, allowing an approximate equilibrium between the convective diabatic heating and adiabatic cooling due to upward motion. The converged moisture associated with circulation driven by shallow heating exceeds the amount needed to maintain the heat source. However, the circulation driven by deep heating does not feed back effectively to the moisture convergence, and thus cannot be self-sustaining. Based on these results, a new mechanism is proposed for the interaction between the large-scale convection and large-scale circulation. The new mechanism states that shallow heating drives a strong low-level moisture convergence so that the system of shallow heating and the forced large-scale circulation is unstable. When the unstable system reaches a certain amplitude, the stable cap layer immediately above the shallow heating erodes, and deep convection arises, which consumes most of the converged moisture at low levels without much feedback to the low-level convergence of moisture. The whole heating circulation system develops and dies; the estimated lifetime of such a system, based on the timescale of adjustment of tropical atmosphere to forcing, is on an intraseasonal timescale. Related observational and modeling evidence that support the new mechanism is discussed."
"55686667100;7201785152;","A moist linear baroclinic model: Coupled dynamical-convective response to El Niño",2003,"10.1175/1520-0442(2003)16<1121:AMLBMC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141676306&doi=10.1175%2f1520-0442%282003%2916%3c1121%3aAMLBMC%3e2.0.CO%3b2&partnerID=40&md5=4f373430e02c19149d1b193bfeddf5a9","A newly developed, linear baroclinic model (LBM) and its application to the tropical ENSO teleconnection is described. The model, based on primitive equations linearized about the observed, zonally varying basic state in northern winter, involves linear schemes for the cumulus convection, and surface sensible and latent heat fluxes, referred to as the moist LBM. This enables us to solve a steady-state response of the coupled dynamical-convective system to a given SST anomaly, which is fairly different from the conventional dry LBM. Linear representation of the convection is acceptable for a realistic range of SST anomalies, reproducing well the Rossby wave train computed in the conventional LBM forced by a tropical heating. The moist LBM is used to examine the formation mechanisms of an anomalous low-level anticyclone near the Philippines that links El Niño with the Asian winter monsoon. Given that the conventional LBM simulates the Philippine Sea anticyclone as a Rossby response to the anomalous diabatic cooling associated with the weakened convection over the Maritime Continent, causes of the convective suppression are examined. Moist LBM experiments forced by observed El Niño SST anomalies indicate that a basinwide warming of the Indian Ocean, in addition to SST anomalies in the Pacific, has a considerable impact in weakening the convection over the Maritime Continent through a modulation of the Walker circulation. Observational analysis supports this idea and further suggests that the lagged Indian Ocean response to El Niño contributes to determining when the Philippine Sea anticyclone is developed. The moist LBM identified a positive wind-evaporation feedback at work between the Philippine anticyclone and the western Pacific SST anomaly, which might also contribute."
"7004390586;7202155374;7403247998;","Climatic impact of Amazon deforestation - A mechanistic model study",1996,"10.1175/1520-0442(1996)009<0859:CIOADM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030456149&doi=10.1175%2f1520-0442%281996%29009%3c0859%3aCIOADM%3e2.0.CO%3b2&partnerID=40&md5=3155d646364a5a88870541e863567598","Recent general circulation model (GCM) experiments suggest a drastic change in the regional climate, especially the hydrological cycle, after hypothesized Amazon basinwide deforestation. To facilitate the theoretical understanding of such a change, we develop an intermediate-level model for tropical climatology, including atmosphere-land-ocean interaction. The model consists of linearized steady-state primitive equations with simplified thermodynamics. A simple hydrological cycle is also included. Special attention has been paid to land-surface processes. In comparison with previous simple modeling work on tropical climatology or anomalies, the present model is more sophisticated in predicting, with little input, most of the important meteorological variables; nevertheless, it is computationally simple. It generally better simulates tropical climatology and the ENSO anomaly than do many of the previous simple models. The climatic impact of Amazon deforestation is studied in the context of this model. Model results show a much weakened Atlantic Walker-Hadley circulation as a result of the existence of a strong positive feedback loop in the atmospheric circulation system and the hydrological cycle. The regional climate is highly sensitive to albedo change and sensitive to evapotranspiration change. The pure dynamical effect of surface roughness length on convergence is small, but the surface flow anomaly displays intriguing features. Analysis of the thermodynamic equation reveals that the balance between convective heating, adiabatic cooling, and radiation largely determines the deforestation response. Studies of the consequences of hypothetical continuous deforestation suggest that the replacement of forest by desert may be able to sustain a dry climate. Scaling analysis motivated by our modeling efforts also helps to interpret the common results of many GCM simulations. When a simple mixed-layer ocean model is coupled with the atmospheric model, the results suggest a 1°C decrease in SST gradient across the equatorial Atlantic Ocean in response to Amazon deforestation. The magnitude depends on the coupling strength."
"6602888227;53867814800;7005527701;34979885900;","Titan global climate model: A new 3-dimensional version of the IPSL Titan GCM",2012,"10.1016/j.icarus.2011.11.032","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857626896&doi=10.1016%2fj.icarus.2011.11.032&partnerID=40&md5=921f23d3c2dcdeef9111c39a88a72e82","We have developed a new 3-dimensional climate model for Titan's atmosphere, using the physics of the IPSL Titan 2-dimensional climate model with the current version of the LMDZ General Circulation Model dynamical core. Microphysics and photochemistry are still computed as zonal averages. This GCM covers altitudes from surface to 500. km altitude, with barotropic waves now being resolved and the diurnal cycle included. The boundary layer scheme has been changed, yielding a strong improvement in the tropospheric zonal wind profile modeled at Huygens descent position and season. The potential temperature profile is fairly consistent with Huygens observations in the lowest 10. km. The latitudinal profile of the near-surface temperature is close to observed values. The minimum of zonal wind observed by the Huygens probe just above the tropopause is also present in these simulations, and its origin is discussed by comparing solar heating and dynamical transport of energy. The stratospheric temperature and wind fields are consistent with our previous works. Compared to observations, the zonal wind peak is too weak (around 120. m/s) and too low (around 200. km). The temperature structures appear to be compressed in altitude, and depart strongly from observations in the upper stratosphere. These discrepancies are correlated, and most probably related to the altitude of the haze production. The model produces a detached haze layer located more than 150. km lower than observed by the Cassini instruments. This low production altitude is due to the current position of the GCM upper boundary. However, the temporal behaviour of the detached haze layer in the model may explain the seasonal differences observed between Cassini and Voyager 1. The waves present in the GCM are analyzed, together with their respective roles in the angular momentum budget. Though the role of the mean meridional circulation in momentum transport is similar to previous work, and the transport by barotropic waves is clearly seen in the stratosphere, a significant part of the transport at high latitudes is done all year long through low-frequency tropospheric waves that may be baroclinic waves. © 2011 Elsevier Inc."
"7005520511;","The use of TVD limiters for forward-in-time upstream-biased advection schemes in ocean modeling",1998,"10.1175/1520-0493(1998)126<0812:TUOTLF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032028004&doi=10.1175%2f1520-0493%281998%29126%3c0812%3aTUOTLF%3e2.0.CO%3b2&partnerID=40&md5=3a4a29497872b4833a0e138acb941404","This paper explores the use of the constant grid flux form forward-in-time upstream-biased advection schemes for the advection of temperature and salinity in ocean modeling. The constant grid flux form schemes are shown to be an improvement over the traditional central differencing commonly used in ocean models. In addition, nonoscillatory versions of the scheme, which employ flux limiters, are explored. The limiters are based on total variation diminishing concepts and are applied to higher-order (in space) versions of the constant grid flux form scheme. The constant grid flux form schemes arc Crowley-type upstream-biased Eulerian advection schemes. They are mass conserving and possess small amplitude and phase errors. The flux limiters prevent the under-and overshooting associated with the numerical dispersion of the unlimited schemes. The limited schemes are easy to implement, efficient, and nonoscillatory. Of these schemes the third-order and fifth-order versions employing the PDM limiter are shown to give optimal results for the advection of scalars under a number of test cases. There is a trade-off between the greater accuracy of the fifth-order scheme and the requirement of a larger grid stencil associated with a greater computational cost. Higher-order nonoscillatory schemes can easily he developed for three-dimensional primitive equation modeling. A multidimensional version is presented that employs a modified time-splitting technique. It is shown to be suitable for three-dimensional primitive equation modeling."
"56744297600;8285351400;","Stochasticity and spatial resonance in interdecadal climate fluctuations",1997,"10.1175/1520-0442(1997)010<2299:SASRII>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001453545&doi=10.1175%2f1520-0442%281997%29010%3c2299%3aSASRII%3e2.0.CO%3b2&partnerID=40&md5=0f2fa5995344de3ee50ca3c7a61a225d","Ocean-atmosphere interaction plays a key role in climate fluctuations on interdecadal timescales. In this study, different aspects of this interaction are investigated using an idealized ocean-atmosphere model, and a hierarchy of uncoupled and stochastic models derived from it. The atmospheric component is an eddy-resolving two-level global primitive equation model with simplified physical parameterizations. The oceanic component is a zonally averaged sector model of the thermohaline circulation. The coupled model exhibits spontaneous oscillations of the thermohaline circulation on interdecadal timescales. The interdecadal oscillation has qualitatively realistic features, such as dipolar sea surface temperature anomalies in the extratropics. Atmospheric forcing of the ocean plays a dominant role in exciting this oscillation. Although the coupled model is in itself deterministic, it is convenient to conceptualize the atmospheric forcing arising from weather excitation as having stochastic time dependence. Spatial correlations inherent in the atmospheric low-frequency variability play a crucial role in determining the oceanic interdecadal variability, through a form of spatial resonance. Local feedback from the ocean affects the amplitude of the interdecadal variability. The spatial patterns of correlations between the atmospheric flow and the oceanic variability fall into two categories: (i) upstream forcing patterns, and (ii) downstream response patterns. Both categories of patterns are expressible as linear combinations of the dominant modes of variability associated with the uncoupled atmosphere."
"7005744599;6701335949;7202613485;","An analysis of frontogenesis in numerical simulations of baroclinic waves",1994,"10.1175/1520-0469(1994)051<3373:AAOFIN>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028670036&doi=10.1175%2f1520-0469%281994%29051%3c3373%3aAAOFIN%3e2.0.CO%3b2&partnerID=40&md5=5bdad929d89d096cf57c7978813df2ca","Using a primitive equation (PE) model, we revisit two canonical flows that were previously studied using a semigeostrophic equation (SG) model. In a previous paper, the authors showed that the PE and the SG models can have significantly different versions of the large-scale dyamics - here they report on the implications of this difference for frontogenesis. The program for the study of frontogenesis developed by B.J. Hoskins and collaborators is followed to show how, in the PE version of the canonical cases, the surface warm front develops before the cold front, and why the upper-level front is a long, nearly continuous feature going from ridge to trough. -from Authors"
"7003298801;","A preliminary model study of the large-scale seasonal cycle in bottom pressure over the global ocean",1999,"10.1029/1998jc900028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033556630&doi=10.1029%2f1998jc900028&partnerID=40&md5=b9de0d10667c0b4054ab3841c08583b6","Atmospheric and Environmental Research, Inc., Cambridge, Massachusetts Output from the primitive equation model of Semtner and Chervin [1992] is used to examine the seasonal cycle in bottom pressure pb over the global ocean. Effects of the volume-conserving formulation of the model on the calculation of pb are considered. The estimated seasonal, large-scale pb signals have amplitudes ranging from less than 1 cm over most of the deep ocean to several centimeters over shallow, boundary regions. Variability generally increases toward the western sides . of the basins and is also larger in some Southern Ocean regions. An oscillation between subtropical and higher latitudes in the North Pacific is clear. Comparison with barotropic simulations indicates that, on basin scales, seasonal pb variability is related to barotropic dynamics and the seasonal cycle in Ekman pumping and results from a small, net residual in mass divergence from the balance between Ekman and Sverdrup flows. Copyright 1999 by the American Geophysical Union."
"6603665315;7201835429;","A numerical simulation of the landfall of tropical cyclones.",1978,"10.1175/1520-0469(1978)035<0242:ansotl>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0017863504&doi=10.1175%2f1520-0469%281978%29035%3c0242%3aansotl%3e2.0.co%3b2&partnerID=40&md5=056cf278fb199e7e2c8ac58616eb0d85","A GFDL tropical cyclone model was applied to simulate storm landfall. The numerical model is a three-dimensional, primitive equation model and has 11 vertical levels with four in the planetary boundary layer. The horizontal grid spacing is variable with finest solution being 20 km near the centre. This model was used successfully in the past to investigate the development of tropical cyclones over the ocean. In the present experiments, a simple situation is assumed where a mature tropical cyclone drifts onto flat land. In such a case, the landfall can be simulated by changing the position of the coastline in the computational domain rather than by moving the storm. As the coastline moves with a specified speed, the surface boundary conditions are altered at the shore from those for the ocean to those for the land by increasing the surface roughness length and also by suppressing the evaporation. Supplementary experiments indicate that the suppression of evaporation is the most important factor in the decay of a storm upon landfall. When the evaporation is suppressed, the storm eventually weakens whether the surface roughness is increased or not. An increased surface roughness, which causes increased inflow in the boundary layer, has little immediate negative impact on the storm intensity. (based on Authors' abstract)"
"9244992800;55716319700;","The response of westerly jets to thermal driving in a primitive equation model",2005,"10.1175/JAS3571.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344445636&doi=10.1175%2fJAS3571.1&partnerID=40&md5=7258f2b2e071ebcc82421964b06b589d","The structure of westerly jets in a statistically steady state is investigated with both dry and moist models on the sphere. The dry model is forced with an idealized radiative equilibrium temperature profile that consists of a global-scale base profile plus both localized tropical heating and high-latitude cooling. The tropical heating controls the intensity of the subtropical jet, while the high-latitude cooling modulates the meridional width of the extratropical baroclinic zone. The jet structure is analyzed with a large number of dry model ru ns in which the tropical heating and high-latitude cooling rates are systematically varied. This parameter study shows that, in a regime with weak tropical heating and strong high-latitude cooling, the polar-front jet separates itself from the subtropical jet, forming a double-jet state. In contrast, if the tropical heating rate is greater than a certain value, a strong single jet emerges, indicating that the presence of one or two jets in a statistically steady state is dependent upon the relative values of both the tropical heating and the baroclinic zone width. A set of moist model runs is examined in which the moisture cont ent is systematically varied. For a relatively small moisture content, the circulation prefers a double-jet state. However, for a moisture content that is greater than a certain threshold value, the two jets collapse into a single jet. With the aid of the aforementioned dry model results, an explanation for this nonlinear response exhibited by the moist model is provided. Based on the results of the dry and moist model calculations, this paper discusses various physical interpretations of the circulation responses to global warming presented in the literature. © 2005 American Meteorological Society."
"7202447177;7003888687;6602814114;6602351024;57192158845;7102001327;8067250600;36762751600;6602132012;7801332133;7005862536;6701553081;6701339411;7003557662;6701776280;","Staggered vertical discretization of the canadian environmental multiscale (GEM) model using a coordinate of the log-hydrostatic-pressure type",2014,"10.1175/MWR-D-13-00255.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896747844&doi=10.1175%2fMWR-D-13-00255.1&partnerID=40&md5=e820e454bf82f7883ad81156e52f07c3","The Global Environmental Multiscale (GEM) model is the Canadian atmospheric model used for meteorological forecasting at all scales. A limited-area version now also exists. It is a gridpoint model with an implicit semi-Lagrangian iterative space-time integration scheme. In the ""horizontal,"" the equations are written in spherical coordinates with the traditional shallow atmosphere approximations and are discretized on an Arakawa C grid. In the ""vertical,"" the equations were originally defined using a hydrostatic-pressure coordinate and discretized on a regular (unstaggered) grid, a configuration found to be particularly susceptible to noise. Among the possible alternatives, the Charney-Phillips grid, with its unique characteristics, and, as the vertical coordinate, log-hydrostatic pressure are adopted. In this paper, an attempt is made to justify these two choices on theoretical grounds. The resulting equations and their vertical discretization are described and the solution method of what is forming the new dynamical core of GEMis presented, focusing on these two aspects."
"7004014731;7103342287;","Seasonal amplification of the 2-day wave: Relationship between normal mode and instability",2001,"10.1175/1520-0469(2001)058<1858:SAOTDW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035878215&doi=10.1175%2f1520-0469%282001%29058%3c1858%3aSAOTDW%3e2.0.CO%3b2&partnerID=40&md5=0e00684a39b3142f9468bd6b28ca1a56","The 2-day wave is a prominent feature of the middle and upper atmosphere, amplifying twice-yearly around solstice. Its period, structure, and reproducibility have led to its association with the gravest planetary normal mode of zonal wavenumber 3, the so-called Rossby-gravity mode. On the other hand, its amplification around solstice has also led to its association with baroclinic instability of summer easterlies. To explore the relationship between the Rossby-gravity mode and instability, calculations are performed with the linearized primitive equations that have been generalized to account for that mode's interaction with a generally unstable mean flow. ū. The mode's eigenfrequency is then complex, the imaginary component representing amplification and decay. For mean states representative of solstice and equinox, the normal mode is calculated and then compared to observed behavior in terms of its period, structure, and amplification. The behavior recovered, including structural differences between solstice and equinox, is consistent with major features of the 2-day wave. Under solstitial conditions, the Rossby-gravity mode amplifies by extracting energy from the mean flow, with e-folding times as short as 5 days. Even though its eigenfrequency is then complex, the mode's period remains close to the theoretical value, consistently lying at westward periods of 2.0-2.2 days. Equally robust is its eigenstructure, which extends into both hemispheres. It mirrors the modal structure isolated earlier in the response over real frequency. In contrast, the mode's amplification depends sensitively upon details of the zonal-mean state. Changes of ū that are modest, in some instances subtle, are sufficient to remove instability. Those changes of mean flow sharply alter the mode's growth rate, but have little effect on its eigenperiod and structure."
"7102367341;7402641028;","Spatial Structure of Ultra‐Low‐Frequency Variability of the Flow In A Simple Atmospheric Circulation Model",1992,"10.1002/qj.49711850810","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027072607&doi=10.1002%2fqj.49711850810&partnerID=40&md5=d44ac0f950b31b6043673c3281d1be2a","The internally generated variability of the global circulation on time‐scales in excess of one year is investigated using a multilevel baroclinic primitive‐equation model with moderate resolution of dynamical processes. the model includes idealized heating and friction. Maximum variability is found on time‐scales of around a decade. Empirical orthogonal‐function analysis reveals that the principal component of this variability is an alternate splitting and coalescence of the subtropical and mid‐latitude jets. Associated changes in the strength and distribution of eddy activity are found. the character of the ultra‐low‐frequency variability is completely changed for very low resolutions, but seems relatively insensitive to details of model formulation at higher resolution. the possibilities of deriving a low‐order model which includes ultra‐low‐frequency variability are considered. Copyright © 1992 Royal Meteorological Society"
"6701718698;7004643321;","A numerical study of the variability and the separation of the Gulf Stream, induced by surface atmospheric forcing and lateral boundary flows",1992,"10.1175/1520-0485(1992)022<0660:ANSOTV>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026796678&doi=10.1175%2f1520-0485%281992%29022%3c0660%3aANSOTV%3e2.0.CO%3b2&partnerID=40&md5=4a5d64577ea919a72146d1a9529d1f0c","A primitive equation model is used to study the effects of surface and lateral forcing on the variability and the climatology of the Gulf Stream system. The model is an eddy-resolving, coastal ocean model that includes thermohaline dynamics and a second-order turbulence closure scheme to provide vertical mixing. The surface forcing consists of wind stress and heat fluxes obtained from the Comprehensive Ocean-Atmosphere Data Set (COADS). Sensitivity studies are performed by driving the model with different forcing (e.g., annual versus zero surface forcing or monthly versus annual forcing). The model climatology, obtained from a five-year simulation of each case, is then compared to observed climatologies obtained from satellite-derived SST and hydrocast data. The experiments in which surface heat flux and wind stress were neglected show less realistic Gulf Stream separation and variability, compared with experiments in which annual or seasonal forcing are used. A similar unrealistic Gulf Stream separation is also obtained when the slope-water inflow at the northeast boundary is neglected. The experiments suggest that maintaining the density structure and the concomitant geostrophic flow in the northern recirculation gyre plays an important role in the separation of the Gulf Stream. The maintenance of the recirculation gyre is affected by heat transfer, wind stress, and slope-water inflow. The heat transfer involves several processes; lateral eddy transfer, surface heat flux, and vertical mixing. Further improvement of the Gulf Stream separation and climatology are obtained when seasonal changes in the lateral temperature and salinity boundary conditions are included. The seasonal climatology of the model calculations compare reasonably well with the observed climatology. Although total transports on open boundaries are maintained at climatological values, there are, nevertheless, large seasonal and spatial variations of Gulf Stream transport between Cape Hatteras and 62 degreesW. These changes are accompanied by transport changes in the northern recirculation gyre. (A)"
"7201520140;57210350827;6602688130;7005930509;7005513582;7004126618;55717244800;","The low-resolution CCSM4",2012,"10.1175/JCLI-D-11-00260.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858177920&doi=10.1175%2fJCLI-D-11-00260.1&partnerID=40&md5=29d6ff9975796b3b0781c053a22b1152","The low-resolution version of the Community Climate System Model, version 4 (CCSM4) is a computationally efficient alternative to the intermediate and standard resolution versions of this fully coupled climate system model. It employs an atmospheric horizontal grid of 3.75 × 3.75 and 26 levels in the vertical with a spectral dynamical core (T31) and an oceanic horizontal grid that consists of a nominal 3 resolution with 60 levels in the vertical. This low-resolution version (T31x3) can be used for a variety of applications including long equilibrium simulations, development work, and sensitivity studies. The T31x3 model is validated for modern conditions by comparing to available observations. Significant problems exist for Northern Hemisphere Arctic locales where sea ice extent and thickness are excessive. This is partially due to low heat transport in T31x3, which translates into a globally averaged sea surface temperature (SST) bias of -1.54 C compared to observational estimates from the 1870-99 historical record and a bias of 21.26 C compared to observations from the 1986-2005 historical record. Maximum zonal wind stress magnitude in the Southern Hemisphere matches observational estimates over the ocean, although its placement is incorrectly displaced equatorward. Aspects of climate variability in T31x3 compare to observed variability, especially so for ENSO where the amplitude and period approximate observations. T31x3 surface temperature anomaly trends for the twentieth century also follow observations. An examination of the T31x3 model relative to the intermediate CCSM4 resolution (finite volume dynamical core 1.9 × 2.5) for preindustrial conditions shows the T31x3 model approximates this solution for climate state and variability metrics examined here. © 2012 American Meteorological Society."
"57203183923;7004074265;7006248174;","Relative roles of elevated heating and surface temperature gradients in driving anomalous surface winds over tropical oceans",2001,"10.1175/1520-0469(2001)058<1371:RROEHA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035359728&doi=10.1175%2f1520-0469%282001%29058%3c1371%3aRROEHA%3e2.0.CO%3b2&partnerID=40&md5=f7595a4b0a16beb9aa9817496b8e5694","Elevated heating by cumulus convection and sea surface temperature gradients are both thought to contribute to surface winds over tropical oceans. The relative strength and role of each mechanism is examined by imposing forcing derived from data on a linear primitive equation model with idealized parameterizations for the two forcings, and comparing the response with observed surface winds. Two test cases are studied: one related to the El Niño-Southern Oscillation, and the other related to the ""dipole"" mode in the tropical Atlantic. It is found that in both cases, elevated heating dominates the surface zonel wind response, and contributes significantly to the meridional wind response, especially in the subtropics and the South Pacific and South Atlantic convergence zone regions. Surface temperature gradients dominate the meridional wind forcing in regions near the equator with strong meridional temperature gradients."
"57203406068;","Low-frequency patterns induced by stationary waves",1990,"10.1175/1520-0469(1990)047<0629:lfpibs>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025657106&doi=10.1175%2f1520-0469%281990%29047%3c0629%3alfpibs%3e2.0.co%3b2&partnerID=40&md5=558b5dd9325741f070ca33e958b12b42","A linear nine-level primitive equation model is used to determine whether the nonuniform geographical distribution of low-frequency variability and the underlying structure of low-frequency patterns can be attributed to inhomogeneities in the time-mean state of the atmosphere. The linear model's behaviour is compared with the low-frequency behaviour of a long simulation that has been performed with a general circulation model (GCM) whose numerical formulation matches that of the linear model. The variance of upper tropospheric streamfunction among 1000 steady linear responses to random distributions of thermal forcing is shown to be maximized in the same locations (particularly the North Pacific) as the low-frequency variance in the GCM. The principal low-frequency linear patterns primary source of energy is the conversion of basic state kinetic energy to perturbation kinetic energy. -from Author"
"35330117400;7005705115;","Spectral representation of three-dimensional global data by expansion in normal mode functions.",1981,"10.1175/1520-0493(1981)109<0037:SROTDG>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019657318&doi=10.1175%2f1520-0493%281981%29109%3c0037%3aSROTDG%3e2.0.CO%3b2&partnerID=40&md5=1c2a635f2973612ffe4eb6e1b58c9876","To represent atmospheric data spectrally in 3 indices (zonal wavenumber, and meridional and vertical modal indices), we propose to use 3-dimensional normal mode functions (NMF's) to express the wind and mass fields simultaneously. The NMF's are constructed from the eigensolutions of a global primitive equation model and they are orthogonal functions. -from Authors"
"7004471232;56160100900;7203009620;8884425800;35514012200;","An extended Kalman filter to assimilate satellite altimeter data into a nonlinear numerical model of the tropical Pacific Ocean: Method and validation",1999,"10.1029/1998jc900079","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033559539&doi=10.1029%2f1998jc900079&partnerID=40&md5=2006b4634dd796ea84277aac5451df3a","A new implementation of the extended Kalman filter scheme is developed for the purpose of assimilating observations into a high-resolution nonlinear numerical model of the tropical Pacific Ocean. It is characterized by two successive stages: (1) approximation of the error covariance matrix by a singular low-rank matrix which leads to making corrections only in those directions for which the error is not naturally attenuated by the system (in this respect it is quite similar to the approach adopted by Cane et al. [1996]), and (2) modification of these directions over time according to the model dynamics, thus reflecting the evolutive nature of the filter. The filter is initialized by a method based on the empirical orthogonal functions obtained from free runs of the model. The reduction of the error covariance matrix avoids the overwhelming burden of computing the temporal evolution of the prediction error with all the degrees of freedom of the full state vector. This assimilation scheme is implemented in the Gent and Cane [1989] primitive equation reduced gravity model. This model has the advantage of using a σ coordinate in the vertical which allows a geographical refinement of the vertical resolution for thermocline gradients. It is forced by the Florida State University database winds, and the Chen et al. [1994] hybrid scheme parametrization is assumed for the mixed layer. The domain of application is the tropical Pacific Ocean basin between 120° E and 80° W longitude and 30° S and 30° N latitude. The resolution is finest at the equator and steadily increases away from the equator. In a first application, validation twin experiments are conducted in which observations are assumed to be synthetic altimeter data sampled according to the TOPEX/POSEIDON mission features. The method is shown to be efficient under various conditions and, in particular, to be capable of transferring information in the vertical from the surface-only altimeter data to the deepest ocean layers and therefore of adequately constraining the thermal and the velocity profiles within the 300 or 400 m upper ocean. In a second application, real TOPEX/POSEIDON data are used and the results evaluated against independent in situ data, namely, Tropical Ocean - Global Atmosphere (TOGA)/TAO mooring observations. Improvements in the model behavior are clear in terms of the time variability of the tropical ocean. It therefore seems that the reduced state Kalman filter with empirical orthogonal function (EOF) initialization can be applied with success to such a primitive equation model of the Pacific for the assimilation of altimeter data. However, at this stage the evolutivity of the filter seems to have a limited impact on the performances, which was not the case for tests in the strongly nonlinear midlatitudes [Pham et al., 1998a]. Copyright 1999 by the American Geophysical Union."
"14319188300;","Effect of latitudinal variations in low-level baroclinicity on eddy life cycles and upper-tropospheric wave-breaking processes",2009,"10.1175/2008JAS2919.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69849087683&doi=10.1175%2f2008JAS2919.1&partnerID=40&md5=6a31e9ed35a5b7420b59df266ef810b9","An analysis of the potential vorticity gradient and the refractive index in quasigeostrophic (QG) flows on the sphere reveals that the absolute vorticity and the stretching parts have two contradictory effects on the horizontal shape of the baroclinic waves when the full variations of the Coriolis parameter are taken into account in each term. The absolute vorticity effect favors the anticyclonic (southwest - northeast) tilt and anticyclonic wave breaking (AWB) and is stronger in the upper troposphere. In contrast, the stretching effect promotes the cyclonic (northwest - southeast) tilt and cyclonic wave breaking (CWB) and is more efficient at lower levels. A positive eddy feedback acting on the latitudinal variations of the zonal winds is deduced. 2Because the absolute vorticity and the stretching effects are respectively more and less efficient with increasing latitude, a more northward (southward) jet renders AWB more (less) probable and CWB less (more) probable; the jet is pushed or maintained more northward (southward) by the eddy feedback. Idealized numerical experiments using two aquaplanet models on the sphere, a three-level QG model, and a 10-level primitive equation (PE) model, confirm our analysis. Two strategies are employed: first, a normal-mode approach for jets centered at different latitudes; second, an analysis of long-term integrations of the models where the temperature is relaxed toward zonally as well as nonzonally uniform restoration-temperature profiles located at different latitudes. The positive eddy feedback is much less visible in the QG model and CWB is very rare because it does not contain the stretching effect (because of the constant Coriolis parameter in the stretching term). © 2009 American Meteorological Society."
"7003420726;8068419200;35580303100;56033135100;","Parameter estimation in an atmospheric GCM using the Ensemble Kalman Filter",2005,"10.5194/npg-12-363-2005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17144401880&doi=10.5194%2fnpg-12-363-2005&partnerID=40&md5=e96a777061134dde52fba553dcb28f90","We demonstrate the application of an efficient multivariate probabilistic parameter estimation method to a spectral primitive equation atmospheric GCM. The method, which is based on the Ensemble Kalman Filter, is effective at tuning the surface air temperature climatology of the model to both identical twin data and reanalysis data. When 5 parameters were simultaneously tuned to fit the model to re-analysis data, the model errors were reduced by around 35% compared to those given by the default parameter values. However, the precipitation field proved to be insensitive to these parameters and remains rather poor. The model is computationally cheap but chaotic and otherwise realistic, and the success of these experiments suggests that this method should be capable of tuning more sophisticated models, in particular for the purposes of climate hindcasting and prediction. Furthermore, the method is shown to be useful in determining structural deficiencies in the model which can not be improved by tuning, and so can be a useful tool to guide model development. The work presented here is for a limited set of parameters and data, but the scalability of the method is such that it could easily be extended to a more comprehensive parameter set given sufficient observational data to constrain them. © 2005 Author(s). This work is licensed under a Creative Commons License."
"36077992900;","Global extratropical response to diabatic heating variability of the Asian summer monsoon",2009,"10.1175/2009JAS3008.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549097104&doi=10.1175%2f2009JAS3008.1&partnerID=40&md5=ea4cc0d0f98bda95dbfe40e3138792e7","Global teleconnections associated with the Asian summer monsoon convective activities are investigated based on monthly data of 29 Northern Hemisphere summers defined as June-September (JJAS). Two distinct teleconnection patterns are identified that are associated respectively with variabilities of the Indian summer monsoon and the western North Pacific summer monsoon. The Indian summer monsoon convective activity is associated with a global pattern that has a far-reaching connection in both hemispheres, whereas the western North Pacific summer monsoon convective activity is connected to a Southern Hemisphere wave train that influences the high-latitude South Pacific and South America. A global primitive equation model is utilized to assess the cause of the global circulation anomalies. The model responses to anomalous heatings of both monsoon systems match the general features of the observed circulation anomalies well, and they are mainly controlled by linear processes. The response patterns are largely determined by the summertime large-scale background mean flow and the location of the heating anomaly relative to the upper easterly jet in the monsoon region. © 2009 American Meteorological Society."
"7003991093;8558370300;","Local and hemispheric dynamics of the North Atlantic Oscillation, annular patterns and the zonal index",2008,"10.1016/j.dynatmoce.2007.04.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-41049086120&doi=10.1016%2fj.dynatmoce.2007.04.003&partnerID=40&md5=191544617f6665576f2bbfbbe2931f9a","In this paper we discuss the atmospheric dynamics of the North Atlantic Oscillation (NAO), the zonal index, and annular patterns of variability (also known as annular modes). Our goal is to give a unified treatment of these related phenomena, to make explicit how they are connected and how they differ, and to illustrate their dynamics with the aid of an idealized primitive equation model. Our focus is on tropospheric dynamics. We first show that the structure of the empirical orthogonal functions (EOFs) of the NAO and annular modes follows, at least in part, from the structure of the baroclinic zone. Given a single baroclinic zone, and concomitantly a single eddy-driven jet, the meridional structure of the EOFs follows from the nature of the jet variability, and if the jet variability is constrained to conserve zonal momentum then the observed structure of the EOF can be explained with a simple model. In the zonal direction, if the baroclinic zone is statistically uniform then so is the first EOF, even though there may be little correlation of any dynamical fields in that direction. If the baroclinic activity is zonally concentrated, then so is the first EOF. Thus, at the simplest order of description, the NAO is a consequence of the presence of an Atlantic storm track; the strong statement of this would be that the NAO is the variability of the Atlantic storm track. The positive phase of the NAO corresponds to eddy momentum fluxes (themselves a consequence of wave breaking) that push the eddy-driven jet polewards, separating it distinctly from the subtropical jet. The negative phase of the NAO is characterized by an equatorial shift and, sometimes, a weakening of the eddy fluxes and no separation between sub-tropical and eddy-driven jets. Variations in the zonal index (a measure of the zonally averaged zonal flow) also occur as a consequence of such activity, although the changes occurring are not necessarily synchronous at different longitudes, and the presence of annular modes (i.e., the associated patterns of variability) does not necessarily indicate zonally symmetric dynamics. The NAO, is not, however, a consequence of purely local dynamics, for the storm tracks depend for their existence on patterns of topographic and thermal forcing of near hemispheric extent. The Atlantic storm track in particular is a consequence of the presence of the Rocky mountains, the temperature contrast between the cold continent and warm ocean, and the lingering presence of the Pacific storm track. The precise relationship between the NAO and the storm tracks remains to be determined, as do a number of aspects of storm track dynamics, including their precise relation to the stationary eddies and to the regions of largest baroclinicity. Similarly, the influences of the stratosphere and of sea-surface temperature anomalies, and the causes and predictability of the inter-annual variability of the NAO remain open problems. © 2008 Elsevier B.V. All rights reserved."
"7401993654;57202522439;6701357023;","The Spectral Element Atmosphere Model (SEAM): High-resolution parallel computation and localized resolution of regional dynamics",2004,"10.1175/1520-0493(2004)132<0726:TSEAMS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842735938&doi=10.1175%2f1520-0493%282004%29132%3c0726%3aTSEAMS%3e2.0.CO%3b2&partnerID=40&md5=51bfc61d87bf6b1498741d2f17fb3a75","Fast, accurate computation of geophysical fluid dynamics is often very challenging. This is due to the complexity of the PDEs themselves and their initial and boundary conditions. There are several practical advantages to using a relatively new numerical method, the spectral-element method (SEM), over standard methods. SEM combines spectral-method high accuracy with the geometric flexibility and computational efficiency of finite-element methods. This paper is intended to augment the few descriptions of SEM that aim at audiences besides numerical-methods specialists. Advantages of SEM with regard to flexibility, accuracy, and efficient parallel performance are explained, including sufficient details that readers may estimate the benefit of applying SEM to their own computations. The spectral element atmosphere model (SEAM) is an application of SEM to solving the spherical shallow-water or primitive equations. SEAM simulated decaying Jovian atmospheric shallow-water turbulence up to resolution T1067, producing jets and vortices consistent with Rhines theory. SEAM validates the Held-Suarez primitive equations test case and exhibits excellent parallel performance. At T171L20, SEAM scales up to 292 million floating-point operations per second (Mflops) per processor (29% of supercomputer peak) on 32 Compaq ES40 processors (93% efficiency over using 1 processor), allocating 49 spectral elements/processor. At T533L20, SEAM scales up to 130 billion floating-point operations per second (Gflops) (8% of peak) and 9 wall clock minutes per model day on 1024 IBM POWER3 processors (48% efficiency over 16 processors), allocating 17 spectral elements per processor. Local element-mesh refinement with 300% stretching enables conformally embedding T480 within T53 resolution, inside a region containing 73% of the forcing but 6% of the area. Thereby the authors virtually reproduced a uniform-mesh T363 shallow-water computation, at 94% lower cost. © 2004 American Meteorological Society."
"8558370300;57213993305;7004060399;","Testing the annular mode autocorrelation time scale in simple atmospheric general circulation models",2008,"10.1175/2007MWR2211.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45749146723&doi=10.1175%2f2007MWR2211.1&partnerID=40&md5=bdfb0aa9fd76fd7a8877193e70a1fc3b","A new diagnostic for measuring the ability of atmospheric models to reproduce realistic low-frequency variability is introduced in the context of Held and Suarez's 1994 proposal for comparing the dynamics of different general circulation models. A simple procedure to compute τ, the e-folding time scale of the annular mode autocorrelation function, is presented. This quantity concisely quantifies the strength of low-frequency variability in a model and is easy to compute in practice. The sensitivity of τ to model numerics is then studied for two dry primitive equation models driven with the Held-Suarez forcings: one pseudospectral and the other finite volume. For both models, τ is found to be unrealistically large when the horizontal resolutions are low, such as those that are often used in studies in which long integrations are needed to analyze model variability on low frequencies. More surprising is that it is found that, for the pseudospectral model, τ is particularly sensitive to vertical resolution, especially with a triangular truncation at wavenumber 42 (a very common resolution choice). At sufficiently high resolution, the annular mode autocorrelation time scale τ in both models appears to converge around values of 20-25 days, suggesting the existence of an intrinsic time scale at which the extratropical jet vacillates in the Held and Suarez system. The importance of τ for computing the correct response of a model to climate change is explicitly demonstrated by perturbing the pseudospectral model with simple torques. The amplitude of the model's response to external forcing increases as τ increases, as suggested by the fluctuation-dissipation theorem. © 2008 American Meteorological Society."
"7004429544;6603106251;","A scalable spectral element Eulerian atmospheric model (SEE-AM) for NWP: Dynamical core tests",2004,"10.1175/1520-0493(2004)132<0133:ASSEEA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842587745&doi=10.1175%2f1520-0493%282004%29132%3c0133%3aASSEEA%3e2.0.CO%3b2&partnerID=40&md5=8c76a4a8175373d78958d0705d18b227","A new dynamical core for numerical weather prediction (NWP) based on the spectral element method is presented. This paper represents a departure from previously published work on solving the atmospheric primitive equations in that the horizontal operators are all written, discretized, and solved in 3D Cartesian space. The advantages of using Cartesian space are that the pole singularity that plagues the equations in spherical coordinates disappears; any grid can be used, including latitude-longitude, icosahedral, hexahedral, and adaptive unstructured grids; and the conversion to a semi-Lagrangian formulation is easily achieved. The main advantage of using the spectral element method is that the horizontal operators can be approximated by local high-order elements while scaling efficiently on distributed-memory computers. In order to validate the 3D global atmospheric spectral element model, results are presented for seven test cases: three barotropic tests that confirm the exponential accuracy of the horizontal operators and four baroclinic test cases that validate the full 3D primitive hydrostatic equations. These four baroclinic test cases are the Rossby-Haurwitz wavenumber 4, the Held-Suarez test, and the Jablonowski-Williamson balanced initial state and baroclinic instability tests. Comparisons with four operational NWP and climate models demonstrate that the spectral element model is at least as accurate as spectral transform models while scaling linearly on distributed-memory computers."
"6603432771;7004247643;","Finite difference of adjoint or adjoint of finite difference?",1997,"10.1175/1520-0493(1997)125<3373:FDOAOA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001143222&doi=10.1175%2f1520-0493%281997%29125%3c3373%3aFDOAOA%3e2.0.CO%3b2&partnerID=40&md5=87be4be1954cceee388619c1c931b4a5","Adjoint models are used for atmospheric and oceanic sensitivity studies in order to efficiently evaluate the sensitivity of a cost function (e.g., the temperature or pressure at some target time tf, averaged over some region of interest) with respect to the three-dimensional model initial conditions. The time-dependent sensitivity, that is the sensitivity to initial conditions as function of the initial time tf, may be obtained directly and most efficiently from the adjoint model solution. There are two approaches to formulating an adjoint of a given model. In the first (""finite difference of adjoint""), one derives the continuous adjoint equations from the linearized continuous forward model equations and then formulates the finite-difference implementation of the continuous adjoint equations. In the second (""adjoint of finite difference""), one derives the finite-difference adjoint equations directly from the finite difference of the forward model. It is shown here that the time-dependent sensitivity obtained by using the second approach may result in a very strong nonphysical behavior such as a large-amplitude two-time-step leapfrog computational mode, which may prevent the solution from being used for time-dependent sensitivity studies. This is an especially relevant problem now, as this second approach is the one used by automatic adjoint compilers that are becoming widely used. The two approaches are analyzed in detail using both a simple model and the adjoint of a primitive equations ocean general circulation model. It is emphasized that both approaches are valid as long as they are used for obtaining the gradient or sensitivity at a single time, as needed in data assimilation, for example. Criteria are presented for the choice of the appropriate adjoint formulation for a given problem."
"57206313116;","Linear response of a stratified tropical atmosphere to convective forcing.",1985,"10.1175/1520-0469(1985)042<1944:LROAST>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022264251&doi=10.1175%2f1520-0469%281985%29042%3c1944%3aLROAST%3e2.0.CO%3b2&partnerID=40&md5=3285f1c397718af691129bfecde083d3","The three-dimensional response of the tropical atmosphere to an isolated heat source is investigated using a primitive equation model linearized about a resting basic state on an equatorial Beta-plane. The model results with steady forcing are compared with the average circulation over tropical South America for a 19-day period in the Southern Hemisphere summer of 1979, and it is shown that the model reproduces many aspects of the observed circulation. The model results with transient forcing are compared with the results from a single equivalent depth version of the mode, and it is shown that the horizontal structure is quite similar, but there are significant differences in the vertical structure of the response. The transient response is also compared with the steady state response. -from Author"
"7004044484;7003374464;7201554561;23485958100;7003540690;7003408439;","Dynamics of the West African monsoon. Part IV: Analysis of 25-90-day variability of convection and the role of the Indian monsoon",2009,"10.1175/2008JCLI2314.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-64049113433&doi=10.1175%2f2008JCLI2314.1&partnerID=40&md5=b2c0be37cf6cce857dbce139430f041c","This paper is part of a series of studies addressing the dynamics of the West African summer monsoon at intraseasonal time scales between 10 and 90 days. The dominant mode of 25-90-day convective variability in the African monsoon was investigated, starting from previous results involving the excitation of dry equatorial Kelvin and Rossby waves by a negative diabatic heat source located over the warm pool. This evolution is consistent with a significant contribution by a convectively coupled equatorial Rossby wave and the MJO. On the other hand, convectively coupled Kelvin waves as well as the dry Kelvin wave signal have a very weak impact. However, there is more to the global control of the African summer monsoon than convectively coupled wave dynamics. The active/break cycle of the Indian monsoon, controlled by a northward-moving dipole of diabatic heating in the Indian sector, can also influence the African monsoon through atmospheric teleconnections. Simulations performed with a dry primitive equation model show that this influence may be transferred through the northern Indian heat source, which excites a Rossby cyclonic circulation propagating westward over North Africa that is cut off by the northward arrival of the equatorial Indian heat source and the associated intrusion of an anticyclonic ridge. Low-level westerly winds and moisture advection within the ITCZ consequently increase over Africa. The mean time lag between an active phase over India and over Africa is about 15-20 days. © 2009 American Meteorological Society."
"12808716500;26643566500;16025236700;","Estimating and correcting global weather model error",2007,"10.1175/MWR3289.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847379878&doi=10.1175%2fMWR3289.1&partnerID=40&md5=6824298db48f63d70eb010638c2666dd","The purpose of the present study is to explore the feasibility of estimating and correcting systematic model errors using a simple and efficient procedure, inspired by papers by Leith as well as DelSole and Hou, that could be applied operationally, and to compare the impact of correcting the model integration with statistical corrections performed a posteriori. An elementary data assimilation scheme (Newtonian relaxation) is used to compare two simple but realistic global models, one quasigeostrophic and one based on the primitive equations, to the NCEP reanalysis (approximating the real atmosphere). The 6-h analysis corrections are separated into the model bias (obtained by time averaging the errors over several years), the periodic (seasonal and diurnal) component of the errors, and the nonperiodic errors. An estimate of the systematic component of the nonperiodic errors linearly dependent on the anomalous state is generated. Forecasts corrected during model integration with a seasonally dependent estimate of the bias remain useful longer than forecasts corrected a posteriori. The diurnal correction (based on the leading EOFs of the analysis corrections) is also successful. State-dependent corrections using the full-dimensional Leith scheme and several years of training actually make the forecasts worse due to sampling errors in the estimation of the covariance. A sparse approximation of the Leith covariance is derived using univariate and spatially localized covariances. The sparse Leith covariance results in small regional improvements, but is still computationally prohibitive. Finally, singular value decomposition is used to obtain the coupled components of the correction and forecast anomalies during the training period. The corresponding heterogeneous correlation maps are used to estimate and correct by regression the state-dependent errors during the model integration. Although the global impact of this computationally efficient method is small, it succeeds in reducing state-dependent model systematic errors in regions where they are large. The method requires only a time series of analysis corrections to estimate the error covariance and uses negligible additional computation during a forecast. As a result, it should be suitable for operational use at relatively small computational expense. © 2007 American Meteorological Society."
"7102625188;","Tropical wave driving of the annual cycle in tropical tropopause temperatures. Part II: Model results",2006,"10.1175/JAS3698.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744477363&doi=10.1175%2fJAS3698.1&partnerID=40&md5=89f332b02b15f3bcf96f47720100958b","The atmospheric response to a localized distribution of tropical heating is examined in terms of the stationary waves excited and how these impact the mean flow near the tropical tropopause. This is done by examining nonlinear simulations of the Gill model with a primitive equation model that extends from the surface up into the stratosphere. The model produces strong cooling of zonal mean temperatures near the tropical tropopause when the heating is on the equator but weaker cooling with the heating at 15°N. The model shows that equatorial Rossby waves that penetrate the lower stratosphere and changes in EP flux divergence that correspond to the observed changes between December and August. It is suggested that ascent in the upper tropical troposphere is driven by vorticity advection or equivalently potential vorticity fluxes due to these equatorial Rossby waves, particularly when the heating is close to the equator. The model results provide support to the hypothesis that the annual cycle in tropical tropopause temperatures is a result of the annual variation in latitude of tropical heating and that equatorial Rossby waves are key in producing the response in the upper troposphere and lower stratosphere. © 2006 American Meteorological Society."
"7101630970;9636904200;","The equatorial response to higher-latitude forcing",2000,"10.1175/1520-0469(2000)057<1197:TERTHL>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034088578&doi=10.1175%2f1520-0469%282000%29057%3c1197%3aTERTHL%3e2.0.CO%3b2&partnerID=40&md5=9cba43afdbd07effac40160e21336317","The classic view, following Charney and Webster and Holton, is that significant midlatitude forcing of the Tropics can be expected only in regions with westerly winds in the upper troposphere because it is only in these regions that stationary Rossby waves will be able to propagate toward the equator. Here it is shown that higher-latitude forcing can project directly onto equatorial waves and give a significant tropical response in both easterly and westerly tropical flow. The equatorial response to higher-latitude forcing is considered in the context of a dry atmosphere and a localized higher-latitude forcing with eastward or westward phase speed. Previous ideas of the Doppler shifting of equatorial waves by zonal flows are extended to include consideration of a forcing involving a range of zonal wavenumbers. A Gill-type model suggests that there can be significant forcing of equatorial waves by either vorticity forcing or heating in higher latitudes. In agreement with the theory, the Kelvin wave response to eastward forcing is peaked at high frequencies/short periods but reduces only slowly with decreasing frequency. Primitive-equation experiments confirm the strong equatorial response associated with a deep Kelvin wave for forcing in midlatitudes. The response is strongest in the Eastern Hemisphere with its equatorial, upper-tropospheric easterlies. The possible importance of this equatorial response in the organization of large-scale, deep tropical convection and the initiation of the Madden-Julian oscillation is discussed. The ability of westward forcing in higher latitudes to trigger Rossby-gravity and Rossby waves is found in the primitive-equation model to be significant but rather less robust. These wave signatures are clearest in the lower troposphere. For shorter periods the Rossby-gravity wave dominates, and for upper-tropospheric forcing, downward and eastward wave activity propagation is seen. Upper-tropospheric westerlies are found to enhance the response.The classic view, following Charney and Webster and Holton, is that significant midlatitude forcing of the Tropics can be expected only in regions with westerly winds in the upper troposphere because it is only in these regions that stationary Rossby waves will be able to propagate toward the equator. Here it is shown that higher-latitude forcing can project directly onto equatorial waves and give a significant tropical response in both easterly and westerly tropical flow. The equatorial response to higher-latitude forcing is considered in the context of a dry atmosphere and a localized higher-latitude forcing with eastward or westward phase speed. Previous ideas of the Doppler shifting of equatorial waves by zonal flows are extended to include consideration of a forcing involving a range of zonal wavenumbers. A Gill-type model suggests that there can be significant forcing of equatorial waves by either vorticity forcing or heating in higher latitudes. In agreement with the theory, the Kelvin wave response to eastward forcing is peaked at high frequencies/short periods but reduces only slowly with decreasing frequency. Primitive-equation experiments confirm the strong equatorial response associated with a deep Kelvin wave for forcing in midlatitudes. The response is strongest in the Eastern Hemisphere with its equatorial, upper-tropospheric easterlies. The possible importance of this equatorial response in the organization of large-scale, deep tropical convection and the initiation of the Madden-Julian oscillation is discussed. The ability of westward forcing in higher latitudes to trigger Rossby-gravity and Rossby waves is found in the primitive-equation model to be significant but rather less robust. These wave signatures are clearest in the lower troposphere. For shorter periods the Rossby-gravity wave dominates, and for upper-tropospheric forcing, downward and eastward wave activity propagation is seen. Upper-tropospheric westerlies are found to enhance the response."
"7003718864;7202613485;6602329329;","A new surface model for cyclone-anticyclone asymmetry",2002,"10.1175/1520-0469(2002)059<2405:ANSMFC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037104081&doi=10.1175%2f1520-0469%282002%29059%3c2405%3aANSMFC%3e2.0.CO%3b2&partnerID=40&md5=000566fae47845ef03bf7c80a41afd20","Cyclonic vortices on the tropopause are characterized by compact structure and larger pressure, wind, and temperature perturbations when compared to broader and weaker anticyclones. Neither the origin of these vortices nor the reasons for the preferred asymmetries are completely understood: quasigeostrophic dynamics, in particular, have cyclone-anticyclone symmetry. In order to explore these and related problems, a novel small Rossby number approximation is introduced to the primitive equations applied to a simple model of the tropopause in continuously stratified fluid. This model resolves dynamics that give rise to vortical asymmetries, while retaining both the conceptual simplicity of quasigeostrophic dynamics and the computational economy of two-dimensional flows. The model contains no depth-independent (barotropic) flow, and thus may provide a useful comparison to two-dimensional flows dominated by this flow component. Solutions for random initial conditions (i.e., freely decaying turbulence) exhibit vortical asymmetries typical of tropopause observations, with strong localized cyclones, and weaker diffuse anticyclones. Cyclones cluster around a distinct length scale at a given time, whereas anticyclones do not. These results differ significantly from previous studies of cyclone-anticyclone asymmetry in the shallow-water primitive equations and the periodic balance equations. An important source of asymmetry in the present solutions is divergent flow associated with frontogenesis and the forward cascade of tropopause potential temperature variance. This thermally direct flow changes the mean potential temperature of the tropopause, selectively maintains anticyclonic filaments relative to cyclonic filaments, and appears to promote the merger of anticyclones relative to cyclones."
"8219958200;7201504886;55614754800;35932420900;53980793000;6603247427;36917877800;","Large eddy simulation using the general circulation model ICON",2015,"10.1002/2015MS000431","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945482763&doi=10.1002%2f2015MS000431&partnerID=40&md5=ae6e9001357bb44b804ce4f82d3f12b8","ICON (ICOsahedral Nonhydrostatic) is a unified modeling system for global numerical weather prediction (NWP) and climate studies. Validation of its dynamical core against a test suite for numerical weather forecasting has been recently published by Zängl et al. (2014). In the present work, an extension of ICON is presented that enables it to perform as a large eddy simulation (LES) model. The details of the implementation of the LES turbulence scheme in ICON are explained and test cases are performed to validate it against two standard LES models. Despite the limitations that ICON inherits from being a unified modeling system, it performs well in capturing the mean flow characteristics and the turbulent statistics of two simulated flow configurations - one being a dry convective boundary layer and the other a cumulus-topped planetary boundary layer. © 2015. The Authors."
"36077992900;7005720566;36624095600;","Impact of the Madden-Julian oscillation on wintertime precipitation in Canada",2010,"10.1175/2010MWR3363.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957715208&doi=10.1175%2f2010MWR3363.1&partnerID=40&md5=e66b3bee96a1f5f6339fdf02ee233ecd","Based on the adjusted daily total precipitation data at Canadian stations and the Climate Prediction Center Merged Analysis of Precipitation (CMAP) data during the most recent 30 Northern Hemisphere winters, the connection between the tropical convection of the Madden-Julian oscillation (MJO) and the intraseasonal variability of precipitation in Canada is investigated. The dominant convection patterns associated with the MJO are represented by the two leading modes of the empirical orthogonal function (EOF) analysis that is applied to the pentad outgoing longwave radiation (OLR) in the equatorial Indian Ocean and western Pacific. The first EOF mode is characterized by a single convection center near the Maritime Continent, whereas the second EOF has an east-west dipole structure with enhanced precipitation over the Indian Ocean and reduced convective activity over the tropical western Pacific. Lagged regression analysis reveals significant precipitation anomalies in Canada associated with the tropical convection of the MJO. Above-normal precipitation starts to occur in the west coast of Canada one pentad after a positive EOF2 phase. In the next two pentads, positive precipitation anomalies extend to a large area of south Canada. At the same time, the northeast region experiences reduced precipitation. For strong MJO events when the principal component of EOF2 exceeds its standard deviation, the precipitation anomaly in the west coast of Canada can reach about 20%-30% of its standard deviation of pentad-to-pentad variability. A linearized global primitive equation model is utilized to assess the cause of the intraseasonal variability in the Northern Hemisphere extratropics and its influence on North American weather associated with the tropical heating of the MJO."
"6507400558;57203397766;7004978125;6701357023;","The MJO and convectively coupled waves in a coarse-resolution GCM with a simple multicloud parameterization",2011,"10.1175/2010JAS3443.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953193476&doi=10.1175%2f2010JAS3443.1&partnerID=40&md5=66c8bcf06811f59f20e52434214d3135","The adequate representation of the dominant intraseasonal and synoptic-scale variability in the tropics, characterized by the Madden-Julian oscillation (MJO) and convectively coupled waves, is still problematic in current operational general circulation models (GCMs). Here results are presented using the next-generation NCAR GCM-the High-Order Methods Modeling Environment (HOMME)-as a dry dynamical core at a coarse resolution of about 167 km, coupled to a simple multicloud parameterization. The coupling is performed through a judicious choice of heating vertical profiles for the three cloud types-congestus, deep, and stratiform-that characterize organized tropical convection. Important control parameters that affect the types of waves that emerge are the background vertical gradient of the moisture and the stratiform fraction in the multicloud parameterization, which set the strength of largescale moisture convergence and unsaturated downdrafts in the wake of deep convection, respectively. Three numerical simulations using different moisture gradients and different stratiform fractions are considered. The first experiment uses a large moisture gradient and a small stratiform fraction and provides an MJO-like example. It results in an intraseasonal oscillation of zonal wavenumber 2, moving eastward at a constant speed of roughly 5 m s-1. The second uses a weaker background moisture gradient and a large stratiform fraction and yields convectively coupled Rossby, Kelvin, and two-day waves, embedded in and interacting with each other; and the third experiment combines the small stratiformfraction and the weak backgroundmoisture gradient to yield a planetary-scale (wavenumber 1) second baroclinic Kelvin wave. While the first two experiments provide two benchmark examples that reproduce several key features of the observational record, the third is more of a demonstration of a bad MJO model solution that exhibits very unrealistic features. © 2011 American Meteorological Society."
"7202784462;7004332887;55471266900;","Improving the utility of ocean circulation models through adjustment of the momentum balance",2001,"10.1029/2000jc000680","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034833617&doi=10.1029%2f2000jc000680&partnerID=40&md5=86fd1e017e9b3469d4a4830d7195b52e","We propose a new method to improve the utility of three-dimensional ocean circulation models. The method uses climatological temperature and salinity data to adjust the momentum balance of the model, while leaving the tracer equations fully prognostic and unconstrained. The adjustment is accomplished by replacing density in the hydrostatic equation by a linear combination of model-computed and climatological density. The procedure is equivalent to adding a forcing term to the horizontal momentum equation through a modification of the model's horizontal pressure gradient term. The forcing term modifies the model-computed velocity field, which, in turn, affects the model-computed temperature and salinity fields through the advection term (there is no adjustment of the tracer equations carried by the model). Assuming the linear combination coefficient to be invariant in time and space, we suggest a statistical approach to estimating its optimal value. We apply this ""semiprognostic"" method to the northwest Atlantic. A primitive equation circulation model is initialized with January climatological temperature and salinity and is forced by monthly mean Comprehensive Ocean-Atmosphere Data Set surface wind stress and heat flux, by restoration of the surface salinity to monthly mean climatology, and by flows through the open boundaries. Both the model-computed tracer and velocity fields produced using the semiprognostic method show significant improvement over those produced by a purely prognostic calculation; drift of the tracer and velocity fields away from climatology is greatly reduced. Further, convective mixing is explicitly represented, thus improving the utility of results over those obtained from pure diagnostic calculations. The velocity fields obtained with the new approach are somewhat more realistic than those obtained from pure diagnostic calculations. The method reproduces many well-known circulation features in the region, including the Labrador Current, the Gulf Stream, and the North Atlantic Current. More significantly, the method reproduces reasonably well the seasonal evolution of temperature and salinity in the region despite the fact that the model's tracer fields are not constrained directly by the new method. This result suggests that the semiprognostic approach will be useful for examining the evolution of tracers that are not easily determined by observations. Copyright 2001 by the American Geophysical Union."
"7202611735;7003408439;","Interactions between ENSO, transient circulation, and tropical convection over the Pacific",1999,"10.1175/1520-0442(1999)012<3062:IBETCA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033208163&doi=10.1175%2f1520-0442%281999%29012%3c3062%3aIBETCA%3e2.0.CO%3b2&partnerID=40&md5=6019deb47efe69230beb2680e7c8b8b4","The interannual variability of transient waves and convection over the central and eastern Pacific is examined using 30 northern winters of NCEP-NCAR reanalyses (1968/69-1997/98) and satellite outgoing longwave radiation data starting in 1974. There is a clear signal associated with the El Nino-Southern Oscillation, such the differences in the seasonal-mean basic state lead to statistically significant changes in the behavior of the transients and convection (with periods less than 30 days), which then feed back onto the basic state. During a warm event (El Nino phase), the Northern Hemisphere subtropical jet is strengthened over the central Pacific; the region of upper-tropospheric mean easterlies over the tropical western Pacific expands eastward past the date line, and the upper-tropospheric mean 'westerly duct' over the eastern Pacific is weakened. The transients tend to propagate along the almost continuous waveguide of the subtropical jet; equatorward propagation into the westerly duct is reduced. The transient convective events over the ITCZ typically observed to be associated with these equatorward-propagating waves are subsequently reduced both in number and magnitude, leading to a seasonal-mean net negative diabatic heating anomaly over the central Pacific from 10° to 20°N, which then feeds back onto the basic state. During a cold event (La Nina phase), the situation is reversed. The different propagation characteristics of the transients in El Nino and La Nina basic states are well simulated in initial value experiments with a primitive equation model.The interannual variability of transient waves and convection over the central and eastern Pacific is examined using 30 northern winters of NCEP-NCAR reanalyses (1968/69-1997/98) and satellite outgoing longwave radiation data starting in 1974. There is a clear signal associated with the El Nino-Southern Oscillation, such that differences in the seasonal-mean basic state lead to statistically significant changes in the behavior of the transients and convection (with periods less than 30 days), which then feed back onto the basic state. During a warm event (El Nino phase), the Northern Hemisphere subtropical jet is strengthened over the central Pacific; the region of upper-tropospheric mean easterlies over the tropical western Pacific expands eastward past the date line, and the upper-tropospheric mean 'westerly duct' over the tropical eastern Pacific is weakened. The transients tend to propagate along the almost continuous waveguide of the subtropical jet; equatorward propagation into the westerly duct is reduced. The transient convective events over the ITCZ typically observed to be associated with these equatorward-propagating waves are subsequently reduced both in number and magnitude, leading to a seasonal-mean net negative diabatic heating anomaly over the central Pacific from 10°to 20°N, which then feeds back onto the basic state. During a cold event (La Nina phase), the situation is reversed. The different propagation characteristics of the transients in El Nino and La Nina basic states are well simulated in initial value experiments with a primitive equation model."
"6603703438;6701413579;35497573900;7103211168;","A finite-difference GCM dynamical core with a variable-resolution stretched grid",1997,"10.1175/1520-0493(1997)125<2943:AFDGDC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001675920&doi=10.1175%2f1520-0493%281997%29125%3c2943%3aAFDGDC%3e2.0.CO%3b2&partnerID=40&md5=c3168da8d9bf228bff087e82a019ead7","A finite-difference atmospheric model dynamics, or dynamical core using variable resolution. or stretched grids, is developed and usaed for regional-global medium-term and long-term integrations. The goal of the study is to verify whether using a variable-resolution dynamical core allows us to represent adequately the regional scales over the area of interest (and its vicinity). In other words, it is shown that a significant downscaling is taking place over the area of interest, due to better-resolved regional fields and boundary forcings. It is true not only for short-term intergrations, but also for medium-term and, most importantly. long-term integrations. Numerical experiments are performed with a stretched grid version of the dynamical core of the Goddard Earth Observing System (GEOS) general circulation model (GCM). The dynamical core includes the discrete (finite difference) model dynamics and a Newtonian-type rhs zonal forcing, which is symmetric for both hemispheres about the equator. A flexible, portable global stretched grid design allows one to allocate the area of interest with uniform fine-horizontal (latitude by longitude) resolution over any part of the globe, such as the U. S. territory used in these experiments. Outside the region, grid intervals increase, or stretch, with latitude and longitude. The grids with moderate to large (global) stretching factors or ratios of maximum to minimum grid intervals on the sphere are considered. Dynamical core versions with the total stretching factors ranging from 4 to 32 are used. The model numerical scheme. with all its desirable conservation and other properties, is kept unchanged when using stretched grids. Two model basic horizontal filtering techniques, the polar or high-latitude Fourier filter and the Shapiro filter, are applied to stretched grid fields. Two filtering approaches based on the projection of a stretched grid onto a uniform one are tested. One of them does not provide the necessary computational noise control globally. Another approach provides a workable monotonic global solution. The latter is used within the developed stretched grid version of the GEOS GCM dynamical core that can be run in both the middle-range and long-term modes. This filtering approach allows one to use even large stretching factors. The successful experiments were performed with the dynamical core for several stretched grid versions with moderate to large total stretching factors ranging from 4 to 32. For these versions, the fine resolutions (in degrees) used over the area of interest are 2 × 2.5, 1 × 1.25, 0.5 × 0.625, and 0.25 × 0.3125. Outside the area of interest, grid intervals are stretching to 4 × 5 or 8 × 10. The medium-range 10-day integrations with summer climate initial conditions show a pronounced similarity of synoptic patterns over the area of interest and its vicinity when using a stretched grid or a control global uniform fine-resolution grid. For a long-term benchmark integration performed with the first aforementioned grid, the annual mean circulation characteristics obtained with the stretched grid dynamical core appeared to be profoundly similar to those of the control run with the global uniform fine-resolution grid over the area of interest, or the United States. The similarity is also evident over the best resolved within the used stretched grid northwestern quadrant, whereas it does not take place over the least-resolved southeastern quadrant. In the better-resolved Northern Hemisphere, the the and Hadley cell are close to those of the control run. which does not take place for the Southern Hemisphere with coarser variable resolution. The stretched grid dynamical core integrations have shown no negative computational effects accumulating in time. The major result of the study is that a stretched grid approach allows one to take advantage of enhanced resolution over the region of interest. It provides a better representation of regional fields for both medium-term and long-term integrations."
"12767422800;57203199846;8884425800;7201785152;","Biophysical feedbacks in the tropical Pacific",2005,"10.1175/JCLI3261.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-13844253595&doi=10.1175%2fJCLI3261.1&partnerID=40&md5=6a12f30dd7e64058298d4ddedb586040","This study explores the influence of phytoplankton on the tropical Pacific heat budget. A hybrid coupled model for the tropical Pacific that is based on a primitive equation reduced-gravity multilayer ocean model, a dynamic ocean mixed layer, an atmospheric mixed layer, and a statistical atmosphere is used. The statistical atmosphere relates deviations of the sea surface temperature from its mean to wind stress anomalies and allows for the rectification of the annual cycle and the El Niño-Southern Oscillation (ENSO) phenomenon through the positive Bjerknes feedback. Furthermore, a nine-component ecosystem model is coupled to the physical variables of the ocean. The simulated chlorophyll concentrations can feed back onto the ocean heat budget by their optical properties, which modify solar light absorption in the surface layers. It is shown that both the surface layer concentration as well as the vertical profile of chlorophyll have a significant effect on the simulated mean state, the tropical annual cycle, and ENSO. This study supports a previously suggested hypothesis (Timmermann and Jin) that predicts an influence of phytoplankton concentration of the tropical Pacific climate mean state and its variability. The bioclimate feedback diagnosed here works as follows: Maxima in the subsurface chlorophyll concentrations lead to an enhanced subsurface warming due to the absorption of photosynthetically available shortwave radiation. This warming triggers a deepening of the mixed layer in the eastern equatorial Pacific and eventually a reduction of the surface ocean currents (Murtugudde et al.). The weakened south-equatorial current generates an eastern Pacific surface warming, which is strongly enhanced by the Bjerknes feedback. Because of the deepening of the mixed layer, the strength of the simulated annual cycle is also diminished. This in turn leads to an increase in ENSO variability. © 2005 American Meteorological Society."
"16022263500;55967916100;6507393330;55628584418;7102968207;33367455100;57193921169;7004093651;34770453800;","The unified model, a fully-compressible, non-hydrostatic, deep atmosphere global circulation model, applied to hot Jupiters",2014,"10.1051/0004-6361/201322174","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890525374&doi=10.1051%2f0004-6361%2f201322174&partnerID=40&md5=fd712f5b3c845d18974507e55da62575","We are adapting the global circulation model (GCM) of the UK Met Office, the so-called unified model (UM), for the study of hot Jupiters. In this work we demonstrate the successful adaptation of the most sophisticated dynamical core, the component of the GCM which solves the equations of motion for the atmosphere, available within the UM, ENDGame (Even Newer Dynamics for General atmospheric modelling of the environment). Within the same numerical scheme ENDGame supports solution to the dynamical equations under varying degrees of simplification. We present results from a simple, shallow (in atmospheric domain) hot Jupiter model (SHJ), and a more realistic (with a deeper atmosphere) HD 209458b test case. For both test cases we find that the large-scale, time-averaged (over the 1200 days prescribed test period), dynamical state of the atmosphere is relatively insensitive to the level of simplification of the dynamical equations. However, problems exist when attempting to reproduce the results for these test cases derived from other models. For the SHJ case the lower (and upper) boundary intersects the dominant dynamical features of the atmosphere meaning the results are heavily dependent on the boundary conditions. For the HD 209458b test case, when using the more complete dynamical models, the atmosphere is still clearly evolving after 1200 days, and in a transient state. Solving the complete (deep atmosphere and non-hydrostatic) dynamical equations allows exchange between the vertical and horizontal momentum of the atmosphere, via Coriolis and metric terms. Subsequently, interaction between the upper atmosphere and the deeper more slowly evolving (radiatively inactive) atmosphere significantly alters the results, and acts over timescales longer than 1200 days. © ESO, 2013."
"56692038700;7401682225;7005601718;","Modelling the seasonal thermal stratification and baroclinic circulation in the Bohai Sea",1999,"10.1016/S0278-4343(99)00026-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0345298280&doi=10.1016%2fS0278-4343%2899%2900026-6&partnerID=40&md5=ce220dc0bbafcc4e0199e68446c136b8","The seasonal thermal stratification and baroclinic circulation in the Bohai Sea are investigated with a three-dimensional baroclinic primitive equation model. The seasonal evolution of temperature is well simulated. Stratification appears early in April, intensifies with synoptic and neap-spring fluctuations through summer, and reaches its maximum in the middle of July. It is eventually destroyed at the end of September. There are cold water belts between well-mixed and stratified regions separated by a tidal front and coinciding with the isolines for a temperature difference of 1-2°C between surface and bottom. They are maintained by the entrainment of cold water from the stratified side of the frontal zone and through the mixing by tides and winds. The sea surface temperature (SST) distribution shows a local maximum at the head of three bays and in the area off Qinhuangdao. The latter SST maximum is due to the particularly reduced mixing as both winds and tidal currents are weak in this region. Atmospheric forcing and tides play an essential part for the synoptic and neap-spring variations of SST, stratification and tidal fronts. The circulation in the Bohai Sea results from the combined effects of tides, winds and baroclinic forces. Water transport between the Bohai and Yellow Seas is also controlled by the combination of all these forces. Inflow is strong and mainly confined to a narrow passage in the northern Bohai Strait. Outflow is broad and weak in the rest of the strait."
"55494077000;35618283200;7402590526;55335220500;","A coupled regional climate model for the Lake Victoria Basin of East Africa",2004,"10.1002/joc.983","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1142293891&doi=10.1002%2fjoc.983&partnerID=40&md5=eebcdf2b48e21e8269a7e96c3b072ee6","A nested coupled model has been developed to investigate the two-way interactions between the regional climate of eastern Africa and Lake Victoria. The atmospheric component of the model is the North Carolina State University (NCSU) version of the National Center for Atmospheric Research (NCAR) regional climate model (NCSU-RegCM2). The lake component of the model is based on the Princeton ocean model (POM). Three simulations, each 4 months long, have been performed for the short rains of eastern Africa of September through to December. The control experiment is based on the standard NCSU-RegCM2 model coupled to a one-dimensional model of Lake Victoria. The second experiment was based on the stand-alone three-dimensional primitive equation POM-Lake Victoria model forced by output from the atmospheric component of the control run. The third experiment is based on the integration of the coupled system of the NCSU-RegCM2 model where the one-dimensional lake model in the control run has been replaced by the three-dimensional POM hydrodynamical model for Lake Victoria. The results confirm that adopting the traditional modelling approach, in which the lake hydrodynamics are neglected and the formulation is based entirely on thermodynamics alone, is not entirely satisfactory for the Lake Victoria basin. Such a strategy precludes the transport of heat realistically within the lake, from the heat surplus regions to the cooler regions, and thereby results in a degraded simulation of the climate downstream over the rest of the lake and the surrounding land regions. The numerical simulations show that the southwestern region of the lake is an important source of warm water because it is relatively shallower and the water column is heated up much more quickly during the day than the rest of the lake. The result is that the surface temperature anomaly field from the all-lake area average consists of a gradient pattern with warmer water over the shallow region of the lake over the southeastern sector and a colder pool of water over the northeastern region, where the lake is relatively deeper. This pattern is also reproduced by the one-dimensional lake model. Some of the excess heat over the southeastern region is transported to the colder and deeper region over the northeastern put of the lake by prevailing surface wind flow. Through the lake atmosphere coupling, the resulting asymmetric lake-surface temperature distribution modifies the overlying wind circulation, which in turn reduces the cloud cover and rainfall. This secondary feature in the surface temperature structure cannot be generated by the traditional nested climate models, such as the standard version of the NCAR-RegCM2 model, since the simple static lake model formulation is not capable of supporting horizontal mixing of water. Comparisons show that this feature is weaker in the RegCM2-POM coupled model than the corresponding pattern that we obtained in our previous study based on the 'stand-alone' POM lake model. In contrast, from the simple classical text-book theoretical model of the lake-land breeze phenomena, the simulated surface wind circulation and rainfall distribution are highly asymmetric across the lake. © 2004 Royal Meteorological Society."
"7501723174;7006417494;7004390586;","Maintenance of tropical intraseasonal variability: Impact of evaporation-wind feedback and midlatitude storms",2000,"10.1175/1520-0469(2000)057<2793:MOTIVI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034276857&doi=10.1175%2f1520-0469%282000%29057%3c2793%3aMOTIVI%3e2.0.CO%3b2&partnerID=40&md5=9c944d2d67ba903db0eb4eb89b4705bd","An intraseasonal tropical oscillation with a period of 20-80 days is simulated in the Neelin-Zeng Quasi-Equilibrium Tropical Circulation Model. This model is an intermediate-level atmospheric model that includes primitive equation nonlinearity, radiative-convective feedbacks, a simple land model with soil moisture, and a Betts-Miller-type moist convective adjustment parameterization. Vertical temperature and moisture structures in the model are based on quasi-equilibrium profiles taken from deep convective regions. The tropical intraseasonal variability is reasonably broadband. The eastward propagating 20-80-day variability is dominated by zonal wavenumber 1, shows features similar to an irregular Madden-Julian oscillation (MJO), and exhibits amplitude and phase speeds that vary both seasonally and between events. At higher wavenumbers, the model has a distinction between the low-frequency MJO-like band and the moist Kelvin wave band, similar to that found in observations. In the model, it is conjectured that this arises by interaction of the wavenumber-1 moist Kelvin wave with the zonally asymmetric basic state. Experiments using climatological sea surface temperature forcing are conducted using this model to examine the effects of evaporation-wind feedback and extratropical excitation on the maintenance of intraseasonal variability, with particular attention paid to the low wavenumber mode in the 20-80-day band. These experiments indicate that evaporation-wind feedback partially organizes this intraseasonal variability by reducing damping, but it is not by itself sufficient to sustain this oscillation for the most realistic parameters. Excitation by extratropical variability is a major source of energy for the intraseasonal variability in this model. When midlatitude storms are suppressed, tropical intraseasonal variability is nearly eliminated. However, the eastward propagating intraseasonal signal appears most clearly when midlatitude excitation is aided by the evaporation-wind feedback.An intraseasonal tropical oscillation with a period of 20-80 days is simulated in the Neelin-Zeng Quasi-Equilibrium Tropical Circulation Model. This model is an intermediate-level atmospheric model that includes primitive equation nonlinearity, radiative-convective feedbacks, a simple land model with soil moisture, and a Betts-Miller-type moist convective adjustment parameterization. Vertical temperature and moisture structures in the model are based on quasi-equilibrium profiles taken from deep convective regions. The tropical intraseasonal variability is reasonably broadband. The eastward propagating 20-80-day variability is dominated by zonal wavenumber 1, shows features similar to an irregular Madden-Julian oscillation (MJO), and exhibits amplitude and phase speeds that vary both seasonally and between events. At higher wavenumbers, the model has a distinction between the low-frequency MJO-like band and the moist Kelvin wave band, similar to that found in observations. In the model, it is conjectured that this arises by interaction of the wavenumber-1 moist Kelvin wave with the zonally asymmetric basic state. Experiments using climatological sea surface temperature forcing are conducted using this model to examine the effects of evaporation-wind feedback and extratropical excitation on the maintenance of intraseasonal variability, with particular attention paid to the low wavenumber mode in the 20-80-day band. These experiments indicate that evaporation-wind feedback partially organizes this intraseasonal variability by reducing damping, but it is not by itself sufficient to sustain this oscillation for the most realistic parameters. Excitation by extratropical variability is a major source of energy for the intraseasonal variability in this model. When midlatitude storms are suppressed, tropical intraseasonal variability is nearly eliminated. However, the eastward propagating intraseasonal signal appears most clearly when midlatitude excitation is aided by the evaporation-wind feedback."
"56744297600;","Equatorial superrotation and maintenance of the general circulation in two-level models",1993,"10.1175/1520-0469(1993)050<1211:ESAMOT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027789416&doi=10.1175%2f1520-0469%281993%29050%3c1211%3aESAMOT%3e2.0.CO%3b2&partnerID=40&md5=b70118c2e76f4e8a0387256755e12d47","Suarez and Duffy have noted an interesting bifurcation in a two-level gridpoint general circulation model when strong tropical heating is imposed. This bifurcation results in a model climatology with strong upper-level westerlies in the tropics. In this paper, it is argued that this bifurcation is essentially due to the dominant role played by extratropical baroclinic transients in the tropical angular momentum budget. A series of numerical experiments is analyzed with a global two-level primitive equation model, using spectral truncation in the horizontal. It is concluded that the conventional climatology is stable to weak perturbations, with the ""restoring' force being provided primarily by extratropical baroclinic eddies. Strong perturbations completely change the propagation characteristics of these eddies, leading to a bifurcation of the general circulation. -from Author"
"35298445100;55704630400;7007098523;7403568332;6506556036;56169742200;","Prognostic modeling studies of the Keweenaw Current in Lake Superior. Part I: Formation and evolution",2001,"10.1175/1520-0485(2001)031<0379:PMSOTK>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035245874&doi=10.1175%2f1520-0485%282001%29031%3c0379%3aPMSOTK%3e2.0.CO%3b2&partnerID=40&md5=e2fcacc96641bb5d327b78e41ed41156","The formation and evolution of the Keweenaw Current in Lake Superior were examined using a nonorthogonal-coordinate primitive equation numerical model. The model was initialized by the monthly averaged temperature field observed in June and September 1973 and run prognostically under different forcing conditions with and without winds. As a Rossby adjustment problem, the model predicted the formation of a well-defined coastal current jet within an inertial period of 16.4 h after the current field adjusted to the initial temperature field. The magnitude and direction of this current jet varied with the cross-shelf temperature gradient and wind velocity. It tended to intensify during northeastward (downwelling favorable) winds, and to lessen, or even reverse, during southwestward to northwestward (upwelling favorable) or southeastward (downwelling favorable) winds. In a case with strong stratification and without external atmospheric forcings, a well-defined clockwise warm-core eddy formed near the northeastern coast of the Keweenaw Peninsula as a result of baroclinic instability. A warm-core eddy was detected recently from satellite surface temperature images, the shape and location of which were very similar to those of the model-predicted eddy. The energy budget analysis suggested that the eddy kinetic energy grew exponentially over a timescale of 7 days. Growth was due to a rapid energy transfer from available eddy potential energy. The subsequent decline of the eddy kinetic energy was the result of turbulent diffusion, transfer from the eddy kinetic energy to mean kinetic energy, and outward net energy flux."
"7201554561;","A simple GCM based on dry dynamics and constant forcing",2000,"10.1175/1520-0469(2000)057<1557:ASGBOD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034192933&doi=10.1175%2f1520-0469%282000%29057%3c1557%3aASGBOD%3e2.0.CO%3b2&partnerID=40&md5=ff52246a37d8c6e024fafc491c210052","A dry spectral primitive equation model is used to simulate the global atmospheric circulation during northern winter. The resolution is T21 in the horizontal, with five equally spaced sigma layers. The only additional terms in the equations are those describing linear damping, linear scale-selective diffusion, and time-independent forcing. The damping and diffusion act on temperature and momentum. The forcing acts on all prognostic variables. It is calculated objectively from the tendencies produced when the model is initialized with a long time series of observational analyses, and separated into components to ease comparison with time-dependent perturbation models. The simulated climate reproduces observed features of the circulation, both time-mean fields and transient-eddy covariances, with remarkable success. The accurate simulation of tropical divergent flow is a particularly useful result. The main deficiencies are an underestimation of transient-eddy kinetic energy and a lack of transient activity in the Southern Hemisphere. In an attempt to reduce the forcing of divergent flow, a modified vertical scheme and modified forcing functions based on a calculation of balanced flow are introduced. The former still has significant divergence forcing and makes little difference to the final result. The latter tends to give solutions that are unrealistic in the Tropics. The model's sensitivity to variations in forcing functions and damping parameters is further explored. The Southern Hemisphere transient behavior can be improved by boosting the local forcing of baroclinicity by up to a factor of 2, and a simulation of the Southern Hemisphere winter is relatively successful. The applications and limitations of such a simple fast-running climate model with a relatively realistic simulated climate are discussed.A dry spectral primitive equation model is used to simulate the global atmospheric circulation during northern winter. The resolution is T21 in the horizontal, with five equally spaced sigma layers. The only additional terms in the equations are those describing linear damping, linear scale-selective diffusion, and time-independent forcing. The damping and diffusion act on temperature and momentum. The forcing acts on all prognostic variables. It is calculated objectively from the tendencies produced when the model is initialized with a long time series of observational analyses, and separated into components to ease comparison with time-dependent perturbation models. The simulated climate reproduces observed features of the circulation, both time-mean fields and transient-eddy covariances, with remarkable success. The accurate simulation of tropical divergent flow is a particularly useful result. The main deficiencies are an underestimation of transient-eddy kinetic energy and a lack of transient activity in the Southern Hemisphere. In an attempt to reduce the forcing of divergent flow, a modified vertical scheme and modified forcing functions based on a calculation of balanced flow are introduced. The former still has significant divergence forcing and makes little difference to the final result. The latter tends to give solutions that are unrealistic in the Tropics. The model's sensitivity to variations in forcing functions and damping parameters is further explored. The Southern Hemisphere transient behavior can be improved by boosting the local forcing of baroclinicity by up to a factor of 2, and a simulation of the Southern Hemisphere winter is relatively successful. The applications and limitations of such a simple fast-running climate model with a relatively realistic simulated climate are discussed."
"7202263311;7004177660;24443645900;","Techniques of Lagrangian trajectory analysis in isentropic coordinates.",1986,"10.1175/1520-0493(1986)114<0571:TOLTAI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022842501&doi=10.1175%2f1520-0493%281986%29114%3c0571%3aTOLTAI%3e2.0.CO%3b2&partnerID=40&md5=52a122fce4850ae9fd76cf8215d68532","The first trajectory technique is kinematic, using only the wind information, while the other two, the explicit method of Petersen and Uccellini and an automated version of Danielsen's implicit technique, are dynamic (use both mass and velocity fields). A primitive equation channel model in pressure coordinates was used to generate the basic flow fields. We compared the techniques for data intervals ranging from 12 min to 12 h. The overall level of agreement, even for a 12-h data interval, is very good, particularly for the dynamic techniques. This result implies that, given a spatially and temporally coherent data set, accurate trajectory calculations in the free atmosphere can be performed using these techniques even when data are available only twice daily, as is the case for routine aerological observations. -from Authors"
"7202676587;7004696542;7202759852;","Eliassen-Palm diagnostics of wave-mean flow interaction in the GFDL 'SKYHI' general circulation model.",1983,"10.1175/1520-0469(1983)040<2768:ETWATM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020968325&doi=10.1175%2f1520-0469%281983%29040%3c2768%3aETWATM%3e2.0.CO%3b2&partnerID=40&md5=2729a1f2079506cbad0ea8fbf1bd5f4d","The Eliassen-Palm flux is important in analytical studies of small-amplitude waves where it provides a powerful and elegant tool for the description of wave propagation in mean zonal shear flows, as well as for analysis of the effective mean zonal force induced by the waves. Furthermore, it has recently been used as a diagnostic in a number of studies of atmospheric data and numerical models of specific dynamical phenomena. In this paper, we apply it to the GFDL 'SKYHI' global general circulation model of the troposphere-stratosphere-mesosphere and describe computations of the primitive equations, isobaric co-ordinate form of the Eliassen-Palm flux and its divergence under conditions of annual-mean insolation.-from Authors"
"7004004339;8884425800;","Effects of river inputs into the Bay of Bengal",2001,"10.1029/2000jc000656","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034776006&doi=10.1029%2f2000jc000656&partnerID=40&md5=cf3267bbfb9db21d52c769fce24614d2","The effect of river runoff in the Bay of Bengal is examined using a reduced gravity primitive equation ocean model coupled to an atmospheric boundary layer model. Model simulations are carried out by including river discharges as surface freshwater forcing at the mouths of the rivers. To assess the effect of river inputs on the dynamics and thermodynamics of the tropical Indian Ocean, parallel simulations are carried out by neglecting the river inputs. Additionally, another set of parallel runs without penetrative radiation loss through the mixed layer is carried out. The freshwater flux due to rivers results in lower salinities and shallower mixed layers, as expected. However, the influence of this additional freshwater flux into the bay is rather counterintuitive. With the inclusion of river discharges more heat is absorbed by the ocean, but sea surface temperatures are slightly cooler in the bay because of enhanced entrainment cooling of the shallower mixed layer, enhanced penetrative radiation, and an enhanced effect of latent heat loss on the temperature tendency. This is despite the greater latent heat loss when river input is neglected. Conversley, neglect of penetrative radiation results in a shallower but slightly warmer mixed layer with river input. River input and penetrative radiation each affect the mixed layer depths, the salinity and temperature structure, and currents in the Bay of Bengal, but they have a small effect on SST. Annual SST, averaged over the Bay of Bengal, is only 0.1°C colder with river input. Neglecting penetrative radiation in the river run results in an increase of only 0.2°C for the annual SST. The lack of persistence of a barrier layer in the bay helps regulate SST even in the presence of enhanced buoyancy forcing due to river input. Averaged over the bay, a barrier layer forms as mixed layer detrainment occurs, and the thermocline deepens just after the southwest monsoon and the northeast monsoon. The barrier layer is short-lived in each case it is eroded by mixing. The effect of riverine input in the bay is not confined to the surface waters. A pool of cold anomaly (-1°C) and fresher waters is centered near 100 m depth in the bay with riverine input. This cold pool beneath the mixed layer allows entrainment cooling of the mixed layer to be more effective, even though mass entrainment is lower relative to the case neglecting river input. The more diffuse thermocline in the bay is consistent with enhanced vertical mixing despite the large positive buoyancy forcing. Copyright 2001 by the American Geophysical Union."
"57203054708;6603218374;","Vertical differencing of the primitive equations based on the Charney-Phillips grid in hybrid σ-p vertical coordinates",1996,"10.1175/1520-0493(1996)124<0511:VDOTPE>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000224952&doi=10.1175%2f1520-0493%281996%29124%3c0511%3aVDOTPE%3e2.0.CO%3b2&partnerID=40&md5=ddb270e02eb558be02b4ba228a314089","Two types of vertical grids are used for atmospheric models: the Lorenz grid (L grid) and the Charney-Phillips grid (CP grid). Although the CP grid is the standard grid for quasigeostrophic models, it is not widely used in the primitive equation models because it is easier with the L grid to maintain some of the integral properties of the continuous system. In this paper, problems with the L grid are pointed out that are due to the existence of an extra degree of freedom in the vertical distribution of the temperature (and the potential temperature). Then a vertical differencing of the primitive equations based on the CP grid is presented, while most of the advantages of the L grid in a hybrid σ-p vertical coordinate are maintained. The discrete hydrostatic equation is constructed in such a way that it is free from the vertical computational mode in the thermal field. Also, the vertical advection of the potential temperature in the discrete thermodynamic equation is constructed in such a way that it reduces to the standard (and most straightforward) vertical differencing of the quasigeostrophic equations based on the CP grid. Simulations of standing oscillations superposed on a resting atmosphere are presented using two vertically discrete models, one based on the L grid and the other on the CP grid The comparison of the simulations shows that with the L grid a stationary vertically zigzag pattern dominates in the thermal field, while with the CP grid no such pattern is evident. Simulations of the growth of an extratropical cyclone in a cyclic channel on a β plane are also presented using two different σ-coordinate models, again one with the L grid and the other with the CP grid, starting from random disturbances. The L grid simulation is dominated by short waves, while there is no evidence of short-wave growth in the CP grid simulation."
"23056339400;7102622066;23055378800;","A general circulation model of the atmosphere suitable for long period integrations",1972,"10.1002/qj.49709841808","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000955509&doi=10.1002%2fqj.49709841808&partnerID=40&md5=384ac3dcd7f4f729b90e9d669f53689c","The design of a general circulation model using the primitive equations in spherical form is described, including a statement of the finite difference forms used to integrate the system and explanations of the motives for unusual aspects of the finite difference scheme. The model incorporates the hydrological cycle, topography, a simple scheme for the radiative exchanges and arrangements for the simulation of deep free convection (sub grid‐scale) and for the representation of exchanges of momentum, sensible and latent heat with the underlying surface. An experiment performed with the model forms the subject of a separate paper. Copyright © 1972 Royal Meteorological Society"
"6701845806;55787994000;7403577184;6602371262;56122626400;7402566411;6603552777;7202772927;7102517130;7006957668;7103347548;55742914900;7409322518;7402933297;8617816400;36988140900;7006423931;57206456336;7201884355;6507498114;6506823865;7409376438;6603431141;","Integrated modeling of aerosol, cloud, precipitation and land processes at satellite-resolved scales",2015,"10.1016/j.envsoft.2015.01.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923003570&doi=10.1016%2fj.envsoft.2015.01.007&partnerID=40&md5=91c11e9d9e48edf941dda9cc489a2759","With support from NASA's Modeling and Analysis Program, we have recently developed the NASA Unified-Weather Research and Forecasting model (NU-WRF). NU-WRF is an observation-driven integrated modeling system that represents aerosol, cloud, precipitation and land processes at satellite-resolved scales. ""Satellite-resolved"" scales (roughly 1-25km), bridge the continuum between local (microscale), regional (mesoscale) and global (synoptic) processes. NU-WRF is a superset of the National Center for Atmospheric Research (NCAR) Advanced Research WRF (ARW) dynamical core model, achieved by fully integrating the GSFC Land Information System (LIS, already coupled to WRF), the WRF/Chem enabled version of the GOddard Chemistry Aerosols Radiation Transport (GOCART) model, the Goddard Satellite Data Simulation Unit (G-SDSU), and custom boundary/initial condition preprocessors into a single software release, with source code available by agreement with NASA/GSFC. Full coupling between aerosol, cloud, precipitation and land processes is critical for predicting local and regional water and energy cycles. © 2015."
"7005189183;57193916375;55358014400;7004859022;6603962966;6701760130;6602255123;7003343155;7402247113;57206492539;7005705115;7202834884;7202682036;7404193419;","The Australian air quality forecasting system. Part I: Project description and early outcomes",2004,"10.1175/2093.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042813193&doi=10.1175%2f2093.1&partnerID=40&md5=755190c190e9023de8ca4c2105844827","The Australian Air Quality Forecasting System (AAQFS) is the culmination ot a 3-yr project to develop a numerical primitive equation system for generating high-resolution (1-5 km) short-term (24-36h forecasts for the Australian coastal cities of Melbourne and Sydney. Forecasts are generated 2 times per day for a range of primary and secondary air pollutants, including ozone, nitrogen dioxide, carbon monoxide, sulfur dioxide, and particles that are less than 10 μm in diameter (PM10). A preliminary assessment of system performance has been undertaken using forecasts generated overa 3-month demonstration period. For the priority pollutant ozone it was found that AAQFS achieved a coefficient of determination of 0.65 and 0.57 for forecasts of peak daily 1-h concentration in Melbourne and Sydney, respectively. The probability of detection and false-alarm rate were 0.71 and 0.55, respectively, for a 60-ppb forecast threshold in Melbourne. A similar level of skill was achieved for Sydney. System performance is also promising for the primary gaseous pollutants. Further development is required before the system can be used to forecast PM10 confidently, with a systematic overprediction of 24-h PM10 concentration occurring during the winter months. © 2004 American Meteorological Society."
"7801370642;6508101255;57213211484;","Forced waves on a zonally aligned jet stream",2004,"10.1175/1520-0469(2004)061<0073:FWOAZA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0442297202&doi=10.1175%2f1520-0469%282004%29061%3c0073%3aFWOAZA%3e2.0.CO%3b2&partnerID=40&md5=e3d08c40aa9fd7c147ffc7d254cd6084","The potential vorticity (PV) pattern in the vicinity of the jet stream takes the form of a narrow tube of enhanced PV gradient on the in situ isentropic surfaces. It is asserted that this distinctive structure can serve as a waveguide and a seat for trapped Rossby waves and that a neighboring vortexlike anomaly can trigger such waves and/or interact strongly with the jet. These conjectures are examined theoretically in an idealized setting comprising a finite-scale vortex forcing of a zonally aligned PV discontinuity. The quintessential dynamics of the vortex's influence upon the PV interface are first elucidated in the linear barotropic β-plane limit, and thereafter other aspects of the jet-vortex interaction are examined in a hemispheric primitive equation setting using a nonlinear numerical model. It is shown that for the selected setting the interface can sustain trapped waves, a strong response is favored by larger-scale forcing, and a quasi-resonant response can prevail for some ambient flow settings, provided the vortex advects zonally at approximately the Doppler-shifted velocity of a trapped Rossby wave. It is also deduced that (i) a mesoscale perturbing vortex can retain its coherency despite the deforming effect of the ambient flow; (ii) the enhanced PV gradient can indeed serve as an effective waveguide; and (iii) the backreaction of the interface perturbations upon a weak mesoscale vortex need not be appreciable, and conversely for a stronger synoptic-scale vortex the interaction can lead to significant deformation of both vortex and interface with a tendency for a pairing of the vortex with an oppositely signed anomaly on the distorted interface. Comments are made on the relationship of the results to observed phenomena."
"6506730133;8661012100;7003683808;7004908853;7202607188;7102011023;","The SOCOL version 3.0 chemistry-climate model: Description, evaluation, and implications from an advanced transport algorithm",2013,"10.5194/gmd-6-1407-2013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884136287&doi=10.5194%2fgmd-6-1407-2013&partnerID=40&md5=95b2b738fecc249381b1b445d9fe9b53","We present the third generation of the coupled chemistry-climate model (CCM) SOCOL (modeling tools for studies of SOlar Climate Ozone Links). The most notable modifications compared to the previous model version are (1) the dynamical core has been updated with the fifth generation of the middle-atmosphere general circulation model MA-ECHAM (European Centre/HAMburg climate model), and (2) the advection of the chemical species is now calculated by a mass-conserving and shape-preserving flux-form transport scheme instead of the previously used hybrid advection scheme. The whole chemistry code has been rewritten according to the ECHAM5 infrastructure and transferred to Fortran95. In contrast to its predecessors, SOCOLvs3 is now fully parallelized. The performance of the new SOCOL version is evaluated on the basis of transient model simulations (1975-2004) with different horizontal (T31 and T42) resolutions, following the approach of the CCMVal-1 model validation activity. The advanced advection scheme significantly reduces the artificial loss and accumulation of tracer mass in regions with strong gradients that was observed in previous model versions. Compared to its predecessors, SOCOLvs3 generally shows more realistic distributions of chemical trace species, especially of total inorganic chlorine, in terms of the mean state, but also of the annual and interannual variability. Advancements with respect to model dynamics are for example a better representation of the stratospheric mean state in spring, especially in the Southern Hemisphere, and a slowdown of the upward propagation in the tropical lower stratosphere. Despite a large number of improvements model deficiencies still remain. Examples include a too-fast vertical ascent and/or horizontal mixing in the tropical stratosphere, the cold temperature bias in the lowermost polar stratosphere, and the overestimation of polar total ozone loss during Antarctic springtime. © Author(s) 2013."
"6701588197;","A Kuroshio Extension system model study: Decadal chaotic self-Sustained oscillations",2006,"10.1175/JPO2931.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749670673&doi=10.1175%2fJPO2931.1&partnerID=40&md5=c139d2caf12530fe41a3fc689d1c8371","A model study of the Kuroshio Extension system, in which forcing is provided by a time-independent climatological wind, yields a mean meandering path and a decadal variability of the jet in significant agreement with in situ and altimetric measurements. A reduced-gravity primitive equation ocean model is implemented in a box spanning the whole North Pacific, including a schematic coastline at the western side, and an analytical wind forcing is determined according to the ECMWF and Comprehensive Ocean-Atmosphere Data Set (COADS) climatologies. The modeled time-averaged Kuroshio Extension shows meanders, northern and southern recirculation regions, and a jet penetration that are in good agreement with the corresponding observed climatological features. This result suggests that intrinsic nonlinear mechanisms are likely to play a major role in determining the meander pattern of the mean flow. The internal low-frequency variability is found to be a chaotic bimodal self-sustained oscillation between an energetic meandering state and a much weaker state with a reduced zonal penetration of the jet. These high and low energy states are found to be very similar to the ""elongated"" and ""contracted"" modes of the Kuroshio Extension detected through altimetric measurements; moreover, the characteristic period (of around 10 yr), flow patterns, and transition details of a typical bimodal cycle are found to be in significant agreement with altimeter observations for the period 1992-2004. A complex dynamical mechanism supporting this internal oscillation, and involving the bimodal behavior of the Kuroshio south of Japan, is proposed and discussed. On the basis of these modeling results and of their validation with altimeter data, it is hypothesized that the observed bimodal decadal variability of the Kuroshio Extension is basically due to a self-sustained internal oscillation related to the instability of the Kuroshio south of Japan without any crucial intervention of wind-driven Sverdrup transport fluctuations and of topographic interactions, although such effects certainly play an important role in shaping the finer structure of Kuroshio Extension changes. Finally, in a preliminary analysis of the variability in the framework of nonlinear dynamical systems theory it is suggested that the strange attractor corresponding to the modeled low-frequency variability is associated with a homoclinic orbit produced by a global bifurcation; moreover, transitions between oscillations of different character found for slightly different values of the lateral eddy viscosity and forcing amplitude are conjectured to be due to heteroclinic connections. © 2006 American Meteorological Society."
"55739579300;55716319700;","Hadley cell dynamics in a primitive equation model. Part II: Nonaxisymmetric flow",2001,"10.1175/1520-0469(2001)058<2859:HCDIAP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035482948&doi=10.1175%2f1520-0469%282001%29058%3c2859%3aHCDIAP%3e2.0.CO%3b2&partnerID=40&md5=240ef1a129d8149476c3b0fe0d858b7e","This paper investigates the effect of baroclinic eddies on the structure of the Hadley cell. Self-consistent calculations of both axisymmetric and nonaxisymmetric circulations allow an unambiguous estimate of baroclinic eddy effects on the structure of the Hadley cell. Furthermore, a diagnostic analysis allows us to partition the influence of baroclinic eddies into ""direct"" and ""indirect"" responses. The former refers to the meridional circulation attributable to the explicit eddy fluxes while the latters refers to the meridional circulation attributable to part of other processes, such as surface friction and diabatic heating changes, which are in fact induced by the baroclinic eddies. For a realistic parameter range, it is found that these indirect responses are comparable to the direct response. While the direct response of the eddies is always found to be a strengthening of the Hadley cell, the indirect response can either strengthen or dampen the Hadley cell. When the thermal driving of the atmosphere is moderate, baroclinic eddies always amplify and broaden the Hadley cells. On the other hand, if the thermal driving over the Tropics and subtropics becomes sufficiently strong, the net effect of baroclinic eddies is to dampen (strengthen) the Hadley cell above (below) the height level of maximum diabatic heating. An explanation for this behavior is given in terms of competition between the Hadley cell driving by the eddy fluxes (both direct and indirect) and damping of the Hadley cell by potential temperature mixing."
"7201882869;35614191800;","The Late Cretaceous: Simulation with a coupled atmosphere-ocean general circulation model",1997,"10.1029/97PA00721","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031438535&doi=10.1029%2f97PA00721&partnerID=40&md5=7c940afbd2967810f2b0dcaefba0346a","Results are presented for the climate of the late Cretaceous period (∼75-65 Ma) as simulated by a global climate model that is interactively coupled to a primitive equation global ocean model. Increased values of atmospheric CO2 and altered land surface albedos are invoked to produce the warm Cretaceous temperatures that have been proposed from biogeographic reconstructions. For comparison, a control simulation of the present climate is performed. The globally averaged atmospheric temperature in the Cretaceous simulation stabilizes after 20 years of integration at a value that is 4°C greater than that of the present day. The lower troposphere in high latitudes contributes a majority of the globally averaged warming as a result of the elimination of the Antarctic and Greenland ice sheets. Nevertheless, equatorial surface temperatures are raised by ∼5°C above those of the control simulation and offset somewhat the reduction in near-surface baroclinicity caused by the absence of the high-latitude ice sheets. In the Cretaceous simulation, global precipitation is approximately 10% greater than in the present day, with the only region of reduced precipitation occurring beneath the south Eurasian monsoon. Additionally, the amplitude of the seasonal cycle in near-surface temperatures is smaller in the Cretaceous and, in conjunction with increased mean annual temperatures, precludes the presence of any year-round snow or ice in the simulation. In high latitudes, however, there are regions that seasonally drop below freezing. The temperatures in these regions are warmer than have been previously observed in atmosphere-only simulations as a result of poleward heat transport by the ocean's surface currents. © Copyright 1997 by the American Geophysical Union."
"7005454026;6602920335;","A two-dimensional primitive equation model of frontogenesis forced by confluence and horizontal shear.",1985,"10.1175/1520-0469(1985)042<1259:ATDPEM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022264222&doi=10.1175%2f1520-0469%281985%29042%3c1259%3aATDPEM%3e2.0.CO%3b2&partnerID=40&md5=29fbf3e971c6bd40cd7f4a5755b911ee","A two-dimensional primitive equation model of frontogenesis forced by a combination of conlfuence and horizontal shear is formulated for dry, nearly adiabatic and inviscid conditions. The frontogenetical forcing mechanisms are included by respectively specifying the cross-front and vertical variation of the cross- front geostrophic wind component. The results of three numerical integrations containing confluent forcing are analyzed and discussed in detail. -from Authors"
"57189804341;7005874614;","THERMAL TIDES IN THE ATMOSPHERE OF VENUS: COMPARISON OF MODEL RESULTS WITH OBSERVATIONS.",1984,"10.1175/1520-0469(1984)041<3290:ttitao>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021519596&doi=10.1175%2f1520-0469%281984%29041%3c3290%3attitao%3e2.0.co%3b2&partnerID=40&md5=e16bc387118192ec2d3e335d4f398274","A linearized primitive equation (LPE) model is developed to study thermal tides in the atmosphere of Venus. The LPE model describes diurnal and semidiurnal oscillations of a cyclostrophically balanced atmosphere in which zonal velocity varies with altitude and latitude. The numerical algorithm follows Staniforth and Daley. The solar thermal forcing is increased algebraically in time to separate the forced tidal response from free atmospheric oscillations. Parameters of the basic state and forcing agree with Pioneer Venus observations. Results of the model are compared with the solar-fixed component of brightness temperature variations measured by F. W. Taylor et al. and L. S. Elson."
"12767129100;55764106200;36342537900;6506286471;55795523200;7103030382;6701915334;56298802300;8204115900;36504013400;6507733066;25641111100;56206644300;55764588400;56238118600;57189312722;6507684871;57218083682;","Towards multi-resolution global climate modeling with ECHAM6–FESOM. Part I: model formulation and mean climate",2014,"10.1007/s00382-014-2290-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027926341&doi=10.1007%2fs00382-014-2290-6&partnerID=40&md5=8d55cfb7b82c22b71797da8cf6774842","A new climate model has been developed that employs a multi-resolution dynamical core for the sea ice-ocean component. In principle, the multi-resolution approach allows one to use enhanced horizontal resolution in dynamically active regions while keeping a coarse-resolution setup otherwise. The coupled model consists of the atmospheric model ECHAM6 and the finite element sea ice-ocean model (FESOM). In this study only moderate refinement of the unstructured ocean grid is applied and the resolution varies from about 25 km in the northern North Atlantic and in the tropics to about 150 km in parts of the open ocean; the results serve as a benchmark upon which future versions that exploit the potential of variable resolution can be built. Details of the formulation of the model are given and its performance in simulating observed aspects of the mean climate is described. Overall, it is found that ECHAM6–FESOM realistically simulates many aspects of the observed climate. More specifically it is found that ECHAM6–FESOM performs at least as well as some of the most sophisticated climate models participating in the fifth phase of the Coupled Model Intercomparison Project. ECHAM6–FESOM shares substantial shortcomings with other climate models when it comes to simulating the North Atlantic circulation. © 2014, The Author(s)."
"55469187200;","Jovian dynamics. Part III: Multiple, migrating, and equatorial jets",2003,"10.1175/1520-0469(2003)60<1270:JDPIMM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038170294&doi=10.1175%2f1520-0469%282003%2960%3c1270%3aJDPIMM%3e2.0.CO%3b2&partnerID=40&md5=b628115157ae1367efe06c77ee5b4302","Studies of the dynamical response of thin atmospheric layers overlying thick envelopes are extended to examine how multiple jets, such as those seen on Jupiter and Saturn, can be generated and maintained. The jets are produced by baroclinic instabilities and are examined numerically using a primitive equation model subject to simple heating functions. The motions are confined to a thin upper layer by a heating that produces a flow with either an exponential vertical structure or one that is linear aloft while vanishing below. The motions are driven by latitudinal heating distributions with a variety of global and local components. The calculations show that jets roughly resembling the main Jovian ones in amplitude, scale, and form can be generated and maintained in a steady configuration when the flow has the confined linear structure. When the flow has the exponential structure, however, the jets migrate slowly but continuously equatorward while being regenerated in higher latitudes. For both structures, the flow is sensitive to the heating distribution in low latitudes where jets form only if a significant baroclinicity exists in that region; such jets can also be barotropically unstable and can generate a superrotating current at the equator. In midlatitudes, except for being confined to an upper layer, the baroclinic instabilities resemble the standard forms seen in terrestrial models with high rotation rates. Additional calculations show that superrotating equatorial currents can also be generated for deep layers or for Earth's atmosphere if the initial instabilities are developed in low latitudes. Broad easterly currents such as Neptune's can also be generated by elementary heating distributions, provided that the heated layer becomes progressively thicker with latitude. Finally, the hexagonal shape that high-latitude jets sometimes assume on Saturn when viewed in a polar projection can be attributed to nonlinear waves associated with baroclinic instabilities."
"7004208552;","Evolving the subspace of the three-dimensional multiscale ocean variability: Massachusetts Bay",2001,"10.1016/S0924-7963(01)00025-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034962623&doi=10.1016%2fS0924-7963%2801%2900025-2&partnerID=40&md5=11ce804085cbc39156366f0f6a851e22","A data and dynamics driven approach to estimate, decompose, organize and analyze the evolving three-dimensional variability of ocean fields is outlined. Variability refers here to the statistics of the differences between ocean states and a reference state. In general, these statistics evolve in time and space. For a first endeavor, the variability subspace defined by the dominant eigendecomposition of a normalized form of the variability covariance is evolved. A multiscale methodology for its initialization and forecast is outlined. It combines data and primitive equation dynamics within a Monte-Carlo approach. The methodology is applied to part of a multidisciplinary experiment that occurred in Massachusetts Bay in late summer and early fall of 1998. For a 4-day time period, the three-dimensional and multivariate properties of the variability standard deviations and dominant eigenvectors are studied. Two variability patterns are discussed in detail. One relates to a displacement of the Gulf of Maine coastal current offshore from Cape Ann, with the creation of adjacent mesoscale recirculation cells. The other relates to a Bay-wide coastal upwelling mode from Barnstable Harbor to Gloucester in response to strong southerly winds. Snapshots and tendencies of physical fields and trajectories of simulated Lagrangian drifters are employed to diagnose and illustrate the use of the dominant variability covariance. The variability subspace is shown to guide the dynamical analysis of the physical fields. For the stratified conditions, it is found that strong wind events can alter the structures of the buoyancy flow and that circulation features are more variable than previously described, on multiple scales. In several locations, the factors estimated to be important include some or all of the atmospheric and surface pressure forcings, and associated Ekman transports and downwelling/upwelling processes, the Coriolis force, the pressure force, inertia and mixing. © 2001 Elsevier Science B.V."
"11939929300;57208455668;","A two-way nested global-regional dynamical core on the cubed-sphere grid",2013,"10.1175/MWR-D-11-00201.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874839917&doi=10.1175%2fMWR-D-11-00201.1&partnerID=40&md5=9c3f089abc25b2c349f5e7763ab08690","A nested-grid model is constructed using the Geophysical Fluid Dynamics Laboratory finite-volume dynamical core on the cubed sphere. The use of a global grid avoids the need for externally imposed lateral boundary conditions, and the use of the same governing equations and discretization on the global and regional domains prevents inconsistencies that may arise when these differ between grids. Asimple interpolated nested-grid boundary condition is used, and two-way updates use a finite-volume averaging method. Mass conservation is achieved in two-way nesting by simply not updating the mass field. Despite the simplicity of the nesting methodology, the distortion of the large-scale flow by the nested grid is such that the increase in global error norms is a factor of 2 or less in shallow-water test cases. The effect of a nested grid in the tropics on the zonal means and eddy statistics of an idealized Held-Suarez climate integration is minor, and artifacts due to the nested grid are comparable to those at the edges of the cubedsphere grid and decrease with increasing resolution. The baroclinic wave train in a Jablonowski-Williamson test case was preserved in a nested-grid simulation while finescale features were represented with greater detail in the nested-grid region. The authors also found that lee vortices could propagate out of the nested region and onto a coarse grid, which by itself could not produce vortices. Finally, the authors discuss how concurrent integration of the nested and coarse grids can be significantly more efficient than when integrating the two grids sequentially."
"7004258980;7401804956;","On the sensitivity of Southern Ocean sea ice to the surface freshwater flux: A model study",2001,"10.1029/2000jc900086","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035088032&doi=10.1029%2f2000jc900086&partnerID=40&md5=a3f9ae1e3abe140db9083b9921d4104d","The Hamburg Ocean Primitive Equation model is used to study the response of the Southern Ocean's vertical stability and sea ice cover to variations in the prescribed surface freshwater flux (SFWF). The model is used to investigate the response of the coupled ocean-sea ice system to a number of SFWF climatologies and to changes in the mean surface air temperature of the Southern Hemisphere. The modeled sea ice cover is very sensitive to the SFWF. In particular, a large-scale open ocean polynya develops in the Weddell Sea when the SFWF in that region falls below a critical value of ∼35 cm yr-1. In terms of the oceanic heat flux (OHF) to the base of the sea ice, decreasing the SFWF by 10 cm yr-1 has roughly the same effect as an increase of 2°C in the surface air temperature, with both of these changes acting to increase the Southern Ocean's mean annual OHF of ∼23 W m-2 by ∼10%. Coupled ocean-atmosphere models of transient climate change due to greenhouse warming predict an increase in both surface air temperature and SFWF over the Southern Ocean sea ice zone. Because the sensitivity of the sea ice extent and volume, and of the OHF, to increasing surface air temperature is opposite to that of increasing SFWF, these effects can be expected, at least partially, to offset each other. Copyright 2001 by the American Geophysical Union."
"7202484739;55031058100;57200779562;","A numerical study on tropical cyclone intensification. Part I: Beta effect and mean flow effect",1999,"10.1175/1520-0469(1999)056<1404:ansotc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033562316&doi=10.1175%2f1520-0469%281999%29056%3c1404%3aansotc%3e2.0.co%3b2&partnerID=40&md5=d841e77b2f1aa792ef6165c6af3258ca","The effect of planetary vorticity gradient (beta) and the presence of a uniform mean flow on the intensification of tropical cyclones are studied using a limited-area primitive equation model. The most intense storm evolves on a constant-f plane with zero-mean flow and its structure is symmetric with respect to the vortex center. The presence of an environmental flow induces an asymmetry in a vortex due to surface friction. When f varies the vortex is distorted by the beta gyres. Fourier analysis of the wind field shows that a deepening cyclone is associated with a small asymmetry in the low-level wavenumber-one wind field. A small degree of asymmetry in the wind field allows a more symmetric distribution of the surface fluxes and low-level moisture convergence. On the other hand, a weakening or nonintensifying cyclone is associated with a larger asymmetry in its wave-number-one wind field. This flow pattern generates asymmetric moisture convergence and surface fluxes and a phase shift may exist between their maxima. The separation of the surface flux maximum and the lateral moisture convergence reduces precipitation and inhibits the development of the tropical cyclone. Since the orientation of the asymmetric circulation induced by beta is in the southeast to northwest direction, the asymmetry induced by a westerly flow partially cancels the beta effect asymmetry while that of an easterly flow enhances it. Therefore, in a variable-f environment, westerly flows are more favorable for tropical cyclone intensification than easterly flows of the same speed.The effect of planetary vorticity gradient (beta) and the presence of a uniform mean flow on the intensification of tropical cyclones are studied using a limited-area primitive equation model. The most intense storm evolves on a constant-f plane with zero-mean flow and its structure is symmetric with respect to the vortex center. The presence of an environmental flow induces an asymmetry in a vortex due to surface friction. When f varies the vortex is distorted by the beta gyres. Fourier analysis of the wind field shows that a deepening cyclone is associated with a small asymmetry in the low-level wavenumber-one wind field. A small degree of asymmetry in the wind field allows a more symmetric distribution of the surface fluxes and low-level moisture convergence. On the other hand, a weakening or nonintensifying cyclone is associated with a larger asymmetry in its wave-number-one wind field. This flow pattern generates asymmetric moisture convergence and surface fluxes and a phase shift may exist between their maxima. The separation of the surface flux maximum and the lateral moisture convergence reduces precipitation and inhibits the development of the tropical cyclone. Since the orientation of the asymmetric circulation induced by beta is in the southeast to northwest direction, the asymmetry induced by a westerly flow partially cancels the beta effect asymmetry while that of an easterly flow enhances it. Therefore, in a variable-f environment, westerly flows are more favorable for tropical cyclone intensification than easterly flows of the same speed."
"36179077700;55687302500;15765007300;8339569900;7406243250;31067496800;","Aquaplanet experiments using CAM's variable-resolution dynamical core",2014,"10.1175/JCLI-D-14-00004.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904479646&doi=10.1175%2fJCLI-D-14-00004.1&partnerID=40&md5=626df4106645d2372b197700a59f8061","A variable-resolution option has been added within the spectral element (SE) dynamical core of the U.S. Department of Energy (DOE)-NCAR Community Atmosphere Model (CAM). CAM-SE allows for static refinement via conforming quadrilateral meshes on the cubed sphere. This paper investigates the effect of mesh refinement in a climate model by running variable-resolution (var-res) simulations on an aquaplanet. The variable-resolution grid is a 2° (∼222 km) grid with a refined patch of 0.25° (∼28 km) resolution centered at the equator. Climatology statistics from these simulations are compared to globally uniform runs of 2° and 0.25°. A significant resolution dependence exists when using the CAM version 4 (CAM4) subgrid physical parameterization package across scales. Global cloud fraction decreases and equatorial precipitation increases with finer horizontal resolution, resulting in drastically different climates between the uniform grid runs and a physics-induced grid imprinting in the var-res simulation. Using CAM version 5 (CAM5) physics significantly improves cloud scaling at different grid resolutions. Additional precipitation at the equator in the highresolution mesh results in collocated zonally anomalous divergence in both var-res simulations, although this feature is much weaker in CAM5 than CAM4. The equilibriumsolution at each grid spacing within the var-res simulations captures the majority of the resolution signal of the corresponding globally uniform grids. The var-res simulation exhibits good performance with respect to wave propagation, including equatorial regions where waves pass through grid transitions. In addition, the increased frequency of high-precipitation events in the refined 0.258 area within the var-res simulations matches that observed in the global 0.25° simulations. © 2014 American Meteorological Society."
"6507944208;6603785669;6603814675;7003790105;","Wind-driven variability of the large-scale recirculating flow in the Nordic Seas and Arctic Ocean",2003,"10.1175/1520-0485(2003)033<2534:WVOTLR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042600040&doi=10.1175%2f1520-0485%282003%29033%3c2534%3aWVOTLR%3e2.0.CO%3b2&partnerID=40&md5=ae853e8b6b4af52d09508d5ae65fb257","The varying depth-integrated currents in the Nordic seas and Arctic Ocean are modeled using an integral equation derived from the shallow-water equations. This equation assumes that mass divergence in the surface Ekman layer is balanced by convergence in the bottom Ekman layer. The primary flow component follows contours of f/H. The model employs observed winds and realistic bottom topography and has one free parameter, the coefficient of the (linear) bottom drag. The data used for comparison are derived from in situ current meters, satellite altimetry, and a primitive equation model. The current-meter data come from a 4-yr record at 75°N in the Greenland Sea. The currents here are primarily barotropic, and the model does well at simulating the variability. The ""best"" bottom friction parameter corresponds to a spindown time of 30-60 days. A further comparison with bottom currents from a mooring on the Norwegian continental slope, deployed over one winter period, also shows reasonable correspondence. The principal empirical orthogonal function obtained from satellite altimetry data in the Nordic seas has a spatial structure that closely resembles f/H. A direct comparison of this mode's fluctuations with those predicted by the theoretical model yields linear correlation coefficients in the range 0.75-0.85. The primitive equation model is a coupled ocean-ice version of the Princeton Ocean Model for the North Atlantic and Arctic. Monthly mean depth-averaged velocities are calculated from a 42-yr integration and then compared with velocities predicted from an idealized model driven by the same reanalyzed atmospheric winds. In the largely ice-free Norwegian Sea, the coherences between the primitive equation and idealized model velocities are as high as 0.9 on timescales of a few months to a few years. They are lower in the remaining partially or fully ice-covered basins of the Greenland Sea and the Arctic Ocean, presumably because ice alters the momentum transferred to the ocean by the wind. The coherence in the Canadian Basin of the Arctic can be increased substantially by forcing the idealized model with ice velocities rather than the wind. Estimates of the depth-integrated vorticity budget in the primitive equation model suggest that bottom friction is important but that lateral diffusion is of equal or greater importance in compensating surface Ekman pumping."
"55439368000;57111001300;7004332887;","Evidence of nonlinear dynamics in the eastward shift of the NAO",2003,"10.1029/2002GL015585","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038266425&doi=10.1029%2f2002GL015585&partnerID=40&md5=b626b5bcfe8834bfd4fbeb4a670411cd","Hilmer and Jung [2000] have identified an eastward shift in the sea level pressure (SLP) pattern associated with interannual variability of the North Atlantic Oscillation (NAO) that took place around 1980. We investigate the nature of the eastward shift using a primitive equation, dry atmospheric model driven by diabatic forcing diagnosed from observations. The model results reveal the nonlinear dependence of the spatial pattern of the NAO on the NAO index, the pattern being shifted to the east (west) for high (low) NAO index. General agreement is found between the model and observations. We suggest that the eastward shift noted by Hilmer and Jung [2000] is a consequence of the trend towards higher NAO index during the last several decades of the 20th century."
"6603561402;7006629146;","Dynamical forcing of stratospheric planetary waves by tropospheric baroclinic eddies",1998,"10.1175/1520-0469(1998)055<2361:DFOSPW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032221933&doi=10.1175%2f1520-0469%281998%29055%3c2361%3aDFOSPW%3e2.0.CO%3b2&partnerID=40&md5=f1065a4324d0f553bf5acfa71b9b15af","The forcing of planetary wave variability in the stratosphere by synoptic-scale baroclinic eddies in the troposphere is considered. Simple forced-dissipative numerical experiments are performed in a primitive equation model using a deep hemispheric model domain. The flow is thermally relaxed toward zonally symmetric notional wintertime conditions. No zonally asymmetric thermal or topographic forcing is applied. All planetary-scale zonal asymmetry arises solely through the nonlinear wave-wave interaction of the baroclinic eddies in the troposphere. The numerical experiments indicate that realistic stratospheric planetary wave amplitudes and variability, comparable to those observed in the Southern Hemisphere, can be forced through this mechanism. No evidence is found in these simulations for planetary-scale disturbances arising through in situ instability in the stratosphere. The nonlinear tropospheric forcing mechanism in the numerical simulations is further investigated by reproducing the stratospheric planetary wave response with a linear model that is forced by the nonlinear eddy forcing that acted in the troposphere of the nonlinear simulation. The forced linear model experiments indicate that (i) as anticipated, both the eddy vorticity forcing and the eddy temperature forcing are required to account for the planetary wave response, (ii) only the low-frequency component of the nonlinear forcing is important, (iii) the vertical structure of the eddy forcing is equivalent to a compact source near tropopause level, and (iv) the variability of the planetary wave response in the stratosphere arises primarily from the variability of the nonlinear eddy forcing in the troposphere, rather than from the variability of the wave propagation characteristics associated with the basic-state zonally averaged flow. The eddy vorticity and eddy temperature forcing fields are combined into a single expression by introducing a transformation of the equations that govern the Fourier decomposition of deviations away from the zonally averaged flow, referred to as the transformed Fourier decomposition (TFD). The TFD transformation is essentially a generalization of that used in the transformed Eulerian mean formalism. The spatial and temporal characteristics of the total eddy forcing are then analyzed. The baroclinic eddies in the troposphere of the full simulation show strong organization into wave packets with a dominant wave-2 structure in amplitude. There is a strong, high-frequency, nonlinear wave-2 forcing associated with these packets. However, the propagation characteristics of the background flow in the simulation do not allow upward propagation of wave-2 disturbances with the corresponding frequency and there is little associated signal in the stratosphere. Experiments with a linear model, applying the same nonlinear forcing, show that there are background zonal flows, with plausibly realistic velocity fields, that allow upward propagation of such disturbances. It is therefore suggested that baroclinic wave packets may be an important mechanism for forcing higher-frequency wave-2 disturbances observed in the real Southern Hemisphere stratosphere. The low-frequency stratospheric disturbances obtained in the nonlinear simulations appear to be associated with more subtle aspects of the baroclinic wave packets such as their spatial and temporal variability."
"6507430391;7006334009;6602080118;7004471232;","Assimilation of sea-surface temperature and altimetric observations during 1992-1993 into an eddy permitting primitive equation model of the North Atlantic Ocean",2003,"10.1016/S0924-7963(03)00022-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037547173&doi=10.1016%2fS0924-7963%2803%2900022-8&partnerID=40&md5=d21e9d45f74988af1894f85584ff3f80","Sea-surface temperature (SST) and sea-surface height (SSH) observations collected from space between October 1992 and December 1993 have been assimilated into a realistic primitive equation model of the North Atlantic Ocean circulation at eddy permitting resolution. The assimilated SST data originate from AVHRR observations gathered and processed within the NASA Pathfinder project; the altimetric data consist of SSH maps computed as the sum of a time-invariant dynamic topography and gridded sea-level anomalies obtained by combining Topex/Poseidon and ERS altimeter data. The assimilation scheme is a reduced-rank Kalman filter derived from the Singular Evolutive Extended Kalman (SEEK) methodology [J. Mar. Syst. 16 (1998) 323], in which the error statistics is represented in a subspace of small dimension. The error subspace is initialized with a truncated series of Empirical Orthogonal Functions (EOFs) of the system variability. The analysis algorithm includes a mechanism to update the forecast error statistics adaptively using all pertinent informations from the innovation vector. Hindcast experiments have been conducted with a 1/3° model of the North Atlantic basin forced with ECMWF atmospheric reanalyses. The impact of the data assimilated during 1993 is assessed by examining how observed (SSH and SST) and nonobserved variables (such as velocity and thermohaline properties in the interior of the ocean) are modified by the assimilation scheme. Finally, the validation of the hindcast experiments with independent XBT measurements is performed in order to evaluate the objective skill of the procedure. The various diagnostics demonstrate the positive impact of the satellite data to hindcast the upper ocean circulation at eddy permitting resolution and the capacity of the scheme to estimate the geographic distribution of the forecast error. © 2003 Elsevier Science B.V. All rights reserved."
"7403968239;","A possible effect of an increase in the warm-pool SST on the magnitude of El Niño warming",2003,"10.1175/1520-0442(2003)016<0185:APEOAI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0041619708&doi=10.1175%2f1520-0442%282003%29016%3c0185%3aAPEOAI%3e2.0.CO%3b2&partnerID=40&md5=ec1f0d8186edd5ae7cf925de2490a020","El Niño warming corresponds to an eastward extension of the western Pacific warm pool: one thus naturally wonders whether an increase in the warm pool SST will result in stronger El Niños. This question, though elementary, has not drawn much attention. The observation that the two strongest El Niños in the instrumental record occurred during the last two decades, when the warm pool SST was anomalously high, however, has added some urgency to answering this question. Here observational and numerical results that support a positive answer to this question are shown. The observational results come from an analysis of the heat balance of the tropical Pacific over the period 1980-99. The analysis confirms that El Niño acts as a major mechanism by which the tropical Pacific transports heat poleward-the poleward heat transport is achieved episodically, and those episodes correspond well with the occurrence of El Niños. Moreover, the analysis shows that El Niño is a regulator of the heat content in the western Pacific: the higher the heat content, the stronger the subsequent El Niño warming, which transports more heat poleward, and results in a larger drop in the heat content in the western Pacific. These empirical results suggest that a higher warm-pool SST may result in stronger El Niño events. Specifically, raising the tropical maximum SST through an increase in the radiative heating across the equatorial Pacific initially increases the zonal SST contrast. A stronger zonal SST contrast then strengthens the surface winds and helps to store more heat in the subsurface ocean. Because of the stronger winds and the resulting steeper tilt of the equatorial thermocline, the coupled system is potentially unstable and is poised to release its energy through a stronger El Niño warming. A stronger El Niño then pushes the accumulated heat poleward and prevents heat buildup in the western Pacific, and thereby stabilizes the coupled system. Numerical experiments with a coupled model in which the ocean component is a primitive equation model (the NCAR Pacific basin model), and therefore explicitly calculates the heat budget of the entire equatorial upper ocean, support this suggestion. The numerical experiments further suggest that in the presence of El Niños, the time-mean zonal SST contrast may not be sensitive to increases in the surface heating because the resulting stronger El Niños cool the western Pacific and warm the eastern Pacific."
"7003465848;7103060756;","Middle atmospheric traveling waves forced by latent and convective heating",1993,"10.1175/1520-0469(1993)050<2180:MATWFB>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027846215&doi=10.1175%2f1520-0469%281993%29050%3c2180%3aMATWFB%3e2.0.CO%3b2&partnerID=40&md5=7b4e8281f5a0277cf5ddd7ff2e5b6801","The excitation and propagation of equatorial planetary waves and inertia-gravity waves were studied by comparing simulations from the comprehensive GFDL troposphere-stratosphere-mesosphere SKYHI general circulation model (GCM) and from a linear primitive equation model with the same domain and numerical resolution. The wavelength and frequency characteristics of the prominent vertically propagating equatorial Kelvin and Rossby-gravity waves are remarkably similar in the linear model and in SKYHI. At low latitudes the linear model reproduces the flux of upward-propagating inertia-gravity waves seen in the full model. A significant fraction of the inertia-gravity wave activity found in the midlatitude mesosphere of the SKYHI model can be accounted for by tropical convective heating. The global-scale Rossby normal modes seen in observations were also identified in the analyses of westward-propagating planetary waves in both models. They are of realistic amplitude in the SKYHI simulation but are much weaker in the linear model. Thus, it appears that latent and convective heating is not the main source of excitation for the Rossby normal modes. -from Authors"
"6603413642;6602858513;6701335949;6701537033;","Exploring a global multiresolution modeling approach using aquaplanet simulations*",2013,"10.1175/JCLI-D-12-00154.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877800284&doi=10.1175%2fJCLI-D-12-00154.1&partnerID=40&md5=19f43e8804b05839ca68f881c071c4d8","Results from aquaplanet experiments performed using the Model for Prediction across Scales (MPAS) hydrostatic dynamical core implemented within the Department of Energy (DOE)-NCAR Community Atmosphere Model (CAM) are presented. MPAS is an unstructured-grid approach to climate system modeling that supports both quasi-uniform and variable-resolution meshing of the sphere based on conforming grids. Using quasi-uniform simulations at resolutions of 30, 60, 120, and 240 km, the authors evaluate the performance of CAM-MPAS via its kinetic energy spectra, general circulation, and precipitation characteristics. By analyzing an additional variable-resolution simulation with grid spacing that varies from 30 km in a spherical, continental-sized equatorial region to 240 km elsewhere, the CAM-MPAS's potential for use as a regional climate simulation tool is explored. Similar to other quasi-uniform aquaplanet simulations, tropical precipitation increases with resolution, indicating the resolution sensitivity of the physical parameterizations. Comparison with the finite volume (FV) dynamical core suggests a weaker tropical circulation in the CAM-MPAS simulations, which is evident in reduced tropical precipitation and a weaker Hadley circulation. In the variable-resolution simulation, the kinetic energy spectrum within the high-resolution region closely resembles the quasi-uniform 30-km simulation, indicating a robust simulation of the fluid dynamics. As suggested by the quasi-uniform simulations, the CAM4 physics behave differently in the high and low resolution regions. A positive precipitation anomaly occurs on the western edge of the high-resolution region, exciting a Gill-type response; this zonal asymmetry represents the errors incurred in a variable resolution setting. When paired with a multiresolution mesh, the aquaplanet test case offers an exceptional opportunity to examine the response of physical parameterizations to grid resolution. © 2013 American Meteorological Society."
"55469523400;15124698700;","Upward shift of the atmospheric general circulation under global warming: Theory and simulations",2012,"10.1175/JCLI-D-11-00699.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871744327&doi=10.1175%2fJCLI-D-11-00699.1&partnerID=40&md5=939df7ad2f3b354a72730223fd328a51","Many features of the general circulation of the atmosphere shift upward in response to warming in simulations of climate change with both general circulation models (GCMs) and cloud-system-resolving models. The importance of the upward shift is well known, but its physical basis and the extent to which it occurs coherently across variables are not well understood. A transformation is derived here that shows how an upward shift of a solution to the moist primitive equations gives a new approximate solution with higher tropospheric temperatures. According to the transformation, all variables shift upward with warming but with an additional modification to the temperature and a general weakening of the pressure velocity. The applicabilityof the vertical-shift transformation is explored using a hierarchy of models from adiabatic parcel ascents to comprehensive GCMs. The transformation is found to capture many features of the response to climate change in simulationswith an idealized GCM, including the mid- and upper-tropospheric changes in lapse rate, relative humidity, and meridional wind. The transformation is less accurate when applied to simulations with more realistic GCMs, but it nonetheless captures some important features. Deviations fromthe simulated response are primarily due to the surface boundary conditions, which do not necessarily conform to the transformation, especially in thecase of the zonal winds. The results allow for a physical interpretation of the upward shift in terms of the governing equations and suggest that it may be thought of asa coherent response of the general circulation of the mid- and upper troposphere. © 2012 American Meteorological Society."
"6602333928;7006085538;6603178923;","Sigma model of global ocean circulation and its sensitivity to variations in wind stress",2002,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036631417&partnerID=40&md5=bc0d24149f66090b024c065b94bbb2c3","The ocean general circulation model developed at the Institute of Numerical Mathematics, Russian Academy of Sciences, is briefly described. The model is based on a complete system of nonlinear (primitive) equations describing ocean hydro- and thermodynamics in the Boussinesq approximation and written in a spherical σ-coordinate system. The main feature of the model is that its numerical implementation makes use of splitting with respect to physical processes and spatial coordinates. This allows the use of efficient implicit algorithms. The annual mean regime produced in a 121-year model run with a realistic climatic annual cycle of atmospheric forcing specified from the NCEP reanalyses is analyzed and compared with observations. The simulated ocean circulation patterns and thermohaline fields are shown to accord, on the whole, with observations and to agree well with results of other models. The sensitivity of the global thermohaline circulation to variations in wind stress is examined. To this end, two experiments with different wind stresses specified from NCEP and ECMWF reanalyses are compared. The response of the thermohaline structure and ocean circulation to this wind variation is analyzed. In turn, this response leads to noticeable variations in meridional heat and freshwater transport, which is important in climate formation."
"6506900387;7003871651;","Hierarchies of balance conditions for the f-plane shallow-water equations",2001,"10.1175/1520-0469(2001)058<2411:HOBCFT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035880384&doi=10.1175%2f1520-0469%282001%29058%3c2411%3aHOBCFT%3e2.0.CO%3b2&partnerID=40&md5=a8015c23bdcf480b1adc7b541195e458","For the f-plane shallow-water primitive equations (PEs), hierarchies of balance conditions relating the gravity manifold (divergence δ and ageostrophic vorticity γ = ∫ζ - g▽2h) to the Rossby manifold (linearized potential vorticity 41 = ζ - fh/H) are introduced. These hierarchies are ∂N δ/∂tN = ∂N+1δ/∂tN+1 = 0 (δ balance), ∂N δ/∂tN = ∂Nγ/∂tN = 0 (δ-γ balance), and ∂Nγ/∂tN = ∂N+1γ/∂tN+1 = 0 (γ balance), for N = 0. 1..... How well these balance conditions represent the balance accessible to a given PE flow is explored. Detailed numerical experiments are carried out on an idealized potential vorticity distribution for which the domain maximum Rossby and Froude numbers are Romax = 0.73 and Frmax = 0.28. The numerical results reveal that all these hierarchies are asymptotic: as N increases, imbalance first decreases and then increases, as measured for instance by a linearized available energy. The minimum imbalance, over all the balance conditions considered, is attained by γ balance at N = 2. The most accurate balance conditions (e.g., γ and δ balances at N = 2) all exhibit slightly different energy spectra for the imbalance at medium to largest scales. Further, the greatest improvement shown by these accurate balance conditions over the less accurate conditions like quasigeostrophy occurs at large scales."
"6602329329;7202613485;7005744599;","The next-order corrections to quasigeostrophic theory",1999,"10.1175/1520-0469(1999)056<1547:TNOCTQ>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033150092&doi=10.1175%2f1520-0469%281999%29056%3c1547%3aTNOCTQ%3e2.0.CO%3b2&partnerID=40&md5=69b0453f799061b8d5e361e3d5e1c1ce","Quasigeostrophic theory is an approximation of the primitive equations in which the dynamics of geostrophically balanced motions are described by the advection of potential vorticity. Quasigeostrophy also represents a leading-order theory in the sense that it is derivable from the full primitive equations in the asymptotic limit of zero Rossby number. Building upon quasigeostrophy, and the centrality of potential vorticity, a systematic asymptotic framework is developed from which balanced, next-order corrections in Rossby number are obtained. The simplicity of the approach is illustrated by explicit construction of the next-order corrections to a finite-amplitude Eady edge wave.Quasigeostrophic theory is an approximation of the primitive equations in which the dynamics of geostrophically balanced motions are described by the advection of potential vorticity. Quasigeostrophy also represents a leading-order theory in the sense that it is derivable from the full primitive equations in the asymptotic limit of zero Rossby number. Building upon quasigeostrophy, and the centrality of potential vorticity, a systematic asymptotic framework is developed from which balanced, next-order corrections in Rossby number are obtained. The simplicity of the approach is illustrated by explicit construction of the next-order corrections to a finite-amplitude Eady edge wave."
"56178572000;7102595308;56479980800;13406399300;7406243250;21743443000;","Gravity waves simulated by high-resolution Whole Atmosphere Community Climate Model",2014,"10.1002/2014GL062468","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921844948&doi=10.1002%2f2014GL062468&partnerID=40&md5=f6c1f260367988e9b5c22c77fbe9bd57","For the first time a mesoscale-resolving whole atmosphere general circulation model has been developed, using the National Center for Atmospheric Research Whole Atmosphere Community Climate Model with ∼0.25° horizontal resolution and 0.1 scale height vertical resolution above the middle stratosphere (higher resolution below). This is made possible by the high accuracy and high scalability of the spectral element dynamical core from the High-Order Method Modeling Environment. For the simulated January-February period, the latitude-height structure and the magnitudes of the temperature variance compare well with those deduced from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) observations. The simulation reveals the increasing dominance of gravity waves (GWs) at higher altitudes through both the height dependence of the kinetic energy spectra, which display a steeper slope (∼-3) in the stratosphere and an increasingly shallower slope above, and the increasing spatial extent of GWs (including a planetary-scale extent of a concentric GW excited by a tropical cyclone) at higher altitudes. GW impacts on the large-scale flow are evaluated in terms of zonal mean zonal wind and tides: with no GW drag parameterized in the simulations, forcing by resolved GWs does reverse the summer mesospheric wind, albeit at an altitude higher than climatology, and only slows down the winter mesospheric wind without closing it. The hemispheric structures and magnitudes of diurnal and semidiurnal migrating tides compare favorably with observations. Key PointsFirst mesoscale-resolving whole atmosphere general circulation modelSimulation reveals the growing dominance of gravity waves with altitudeGravity waves and their large-scale impacts evaluated ©2014. American Geophysical Union. All Rights Reserved."
"7005050851;6603060770;","Deep jets on gas-giant planets",2008,"10.1016/j.icarus.2007.10.014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849137854&doi=10.1016%2fj.icarus.2007.10.014&partnerID=40&md5=e200cf4cd3fa339218b4f24d2e651452","Three-dimensional numerical simulations of the atmospheric flow on giant planets using the primitive equations show that shallow thermal forcing confined to pressures near the cloud tops can produce deep zonal winds from the tropopause all the way down to the bottom of the atmosphere. These deep winds can attain speeds comparable to the zonal jet speeds within the shallow, forced layer; they are pumped by Coriolis acceleration acting on a deep meridional circulation driven by the shallow-layer eddies. In the forced layer, the flow reaches an approximate steady state where east-west eddy accelerations balance Coriolis accelerations acting on the meridional flow. Under Jupiter-like conditions, our simulations produce 25 to 30 zonal jets, similar to the number of jets observed on Jupiter and Saturn. The simulated jet widths correspond to the Rhines scale; this suggests that, despite the three-dimensional nature of the dynamics, the baroclinic eddies energize a quasi-two-dimensional inverse cascade modified by the β effect (where β is the gradient of the Coriolis parameter). In agreement with Jupiter, the jets can violate the barotropic and Charney-Stern stability criteria, achieving curvatures ∂2 u / ∂ y2 of the zonal wind u with northward distance y up to 2β. The simulations exhibit a tendency toward neutral stability with respect to Arnol'd's second stability theorem in the upper troposphere, as has been suggested for Jupiter, although deviations from neutrality exist. When the temperature varies strongly with latitude near the equator, our simulations can also reproduce the stable equatorial superrotation with wind speeds greater than 100 m s-1. Diagnostics show that barotropic eddies at low latitudes drive the equatorial superrotation. The simulations also broadly explain the distribution of jet-pumping eddies observed on Jupiter and Saturn. While idealized, these simulations therefore capture many aspects of the cloud-level flows on Jupiter and Saturn."
"7004978125;","New multiscale models and self-similarity in tropical convection",2007,"10.1175/JAS3880.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247608253&doi=10.1175%2fJAS3880.1&partnerID=40&md5=8de537233cc0112fc900d0f0ccbb2a50","One of the unexplained striking features of tropical convection is the observed statistical self-similarity in clusters, superclusters, and intraseasonal oscillations through complex multiscale processes ranging from the mesoscales to the equatorial synoptic scales to the intraseasonal/planetary scales. Here new multispatialscale, multitime-scale, simplified asymptotic models are derived systematically from the equatorial primitive equations on the range of scales from mesoscale to equatorial synoptic to planetary/intraseasonal, which provide a useful analytic framework for addressing these issues. New mesoscale equatorial synoptic dynamical (MESD) models and balanced MESD (BMESD) models are developed for the multitime, multispace interaction from mesoscales to equatorial synoptic scales; new multitime versions of the intraseasonal planetary equatorial synoptic dynamics (IPESD) models are developed for multiple spatiotemporal interactions on equatorial synoptic scales and planetary scales. The mathematical character derived below for all these simplified models explicitly demonstrates that the main nonlinear interactions across scales are quasi-linear where eddy flux divergences of momentum and temperature from nonlinear advection from the smaller-scale spatiotemporal flows as well as mean source effects accumulate in time and drive the waves on the successively larger spatiotemporal scales. Furthermore, these processes that transfer energy to the next larger, longer, spatiotemporal scales are self-similar in a suitable sense established here. On the other hand, the larger scales set the environment for this transport through processes such as mean advection of the smaller scales. © 2007 American Meteorological Society."
"50461782300;57210198577;7404210007;","GCM simulations of Titan's middle and lower atmosphere and comparison to observations",2015,"10.1016/j.icarus.2014.12.030","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921477068&doi=10.1016%2fj.icarus.2014.12.030&partnerID=40&md5=75aaf35d09d28ef76ba911952fee34e4","Simulation results are presented from a new general circulation model (GCM) of Titan, the Titan Atmospheric Model (TAM), which couples the Flexible Modeling System (FMS) spectral dynamical core to a suite of external/sub-grid-scale physics. These include a new non-gray radiative transfer module that takes advantage of recent data from Cassini-Huygens, large-scale condensation and quasi-equilibrium moist convection schemes, a surface model with ""bucket"" hydrology, and boundary layer turbulent diffusion. The model produces a realistic temperature structure from the surface to the lower mesosphere, including a stratopause, as well as satisfactory superrotation. The latter is shown to depend on the dynamical core's ability to build up angular momentum from surface torques. Simulated latitudinal temperature contrasts are adequate, compared to observations, and polar temperature anomalies agree with observations. In the lower atmosphere, the insolation distribution is shown to strongly impact turbulent fluxes, and surface heating is maximum at mid-latitudes. Surface liquids are unstable at mid- and low-latitudes, and quickly migrate poleward. The simulated humidity profile and distribution of surface temperatures, compared to observations, corroborate the prevalence of dry conditions at low latitudes. Polar cloud activity is well represented, though the observed mid-latitude clouds remain somewhat puzzling, and some formation alternatives are suggested. © 2014 Elsevier Inc.."
"6603858877;6603627827;","A high-resolution three-dimensional numerical study of intermediate water formation in the Levantine Sea",1998,"10.1029/98JC01196","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032529814&doi=10.1029%2f98JC01196&partnerID=40&md5=b2de4b243bac2cab2205b981bf9bd7de","We use a three-dimensional primitive equation ocean model to study the formation of Levantine Intermediate Water (LIW), the characteristic intermediate water mass of the Mediterranean Sea. The model is forced by atmospheric monthly climatological values and incorporates a realistic air-sea interaction scheme. The cyclonic Rhodes gyre, a permanent general circulation feature of the Levantine basin, is found to be the unique formation site under these mean climatological conditions. The convection event has a duration of 2 months (February-March), and the estimated annual mean formation rate is 1.2 Sv. Using two different horizontal resolutions, an eddy-resolving (5.5 km) and a non-eddy-resolving (11 km) grid, we are able to make comparative experiments on the influence of eddy dynamics on the convection process. The results indicate that baroclinic eddies formed at the periphery of the cyclonic convection area control the formation process through horizontal advection of buoyant water from the periphery toward the center of the gyre. This mechanism reduces the extent and duration of the LIW formation event. The large number of small-scale and mesoscale baroclinic eddies that dominate the flow field at intermediate depths, together with the Asia Minor Current, are responsible for the spreading of the newly formed LIW, mainly in zonal direction."
"7202364010;","The annual warm to cold phase transition in the eastern equatorial pacific: Diagnosis of the role of stratus cloud-top cooling",1997,"10.1175/1520-0442(1997)010<2447:TAWTCP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031410057&doi=10.1175%2f1520-0442%281997%29010%3c2447%3aTAWTCP%3e2.0.CO%3b2&partnerID=40&md5=5753e6be5b4e656068822a3ce238047f","The forcing of the March to May southerly surface-wind tendency along the equatorial South American coast, which leads to the annual transition of the eastern tropical Pacific basin's climate from its peak warm phase in April, is explored through diagnostic modeling. Modeling experiments with a high-resolution (18 σ-levels, Δθ = 2.5°, 30 zonal waves) steady-state global linear primitive equation model that produces a striking simulation of most aspects of the March to May change in the lower tropospheric circulation over the eastern tropical Pacific, including the notable southerly surface-wind tendency, have provided unique insight into the role of various physical processes. The model is forced by the 3D distribution of the residually diagnosed diabatic heating and the submonthly momentum and thermal transients, all obtained from the twice-daily 2.5° × 2.5° European Centre for Medium-Range Weather Forecasts uninitialized analyses for 1985-95. The principal findings are the following: • The initial southerly surface-wind tendency along the equatorial South American coast in April is forced by the March to May abatement in deep heating (p ≲ 900 mb) over the Amazon due to the northward migration of continental convection, and by the elevated Andean cooling. • The increased Northern Hemisphere deep heating due to the developing Central American monsoons and the eastern Pacific ITCZ also contributes to the generation of the initial coastal southerly wind tendency, but not more strongly than the March to May cooling over South America. • The March to May cooling of the lower troposphere (600-900 mb) over the southeastern tropical Pacific, which likely results from the longwave radiative cooling from the developing stratocumulus cloud tops, generates relatively strong southerly surface-wind tendencies over the eastern Pacific, particularly at the equatorial South American coast. Based on the last finding, a new feedback mechanism can be envisioned for the rapid development of the coastal southerly surface-wind tendency and stratocumulus clouds - in which the lower tropospheric cooling over the southeastern tropical Pacific, due to longwave radiative cooling from the stratocumulus cloud tops, generates southerly surface winds, which in turn foster stratocumulus growth from the increased meridional cold advection and latent heat flux. With respect to the role of stratus clouds in the coupled annual cycle evolution, the new feedback, based on the dynamic response of cloud-top longwave cooling, should proceed more rapidly than the feedback based on the thermodynamic impact of stratus shading on SST."
"6701680928;57206422780;","Operational hindcasting of the tropical Pacific",1989,"10.1016/0377-0265(89)90050-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024821723&doi=10.1016%2f0377-0265%2889%2990050-X&partnerID=40&md5=fe666979d8e17204e9f1263f8d0dff9a","Procedures have been implemented at the Climate Analysis Center of the National Meteorological Center (CAC/NMC) to provide montly hindcasts of oceanographic conditions in the tropical Pacific. A central component of this system is a primitive equation ocean general circulation model that was developed at the Geophysical Fluid Dynamics Laboratory (GFDL). This is forced with monthly mean fields for wind stress and net heat flux. Until recently the former were derived from ship reports available on the Global Telecommunication System (GTS). The heat fluxes are slightly modified climatological fluxes from Esbensen and Kushnir. To correct for errors in the simulations, thermal data in the upper 450 and surface-temperature data are assimilated montly. Numerical experiments were run to examine the sensitivity of the simulations to small changes in the stress fields. Variations of the drag coefficient by 15% result in differences in sea-surface temperature (SST) and subsurface thermal structure in the eastern Pacific that are comparable with the observed annual and interannual variability. Comparisons with simulations in which the wind stresses were derived from operational atmospheric analyses show sensitivities of the same magnitude. Comparisons of simulations forced either with these of ship-recorded winds to a run with data assimilation show that significant errors are found in both, especially in the off-equatorial regions. Consequently, until forcing fields are improved, accurate simulations will require the use of data assimilation. © 1989."
"23034148100;7202145115;","The influence of the quasi-biennial oscillation on the troposphere in winter in a hierarchy of models. Part I: Simplified dry gcms",2011,"10.1175/2011JAS3665.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959630528&doi=10.1175%2f2011JAS3665.1&partnerID=40&md5=6371d1b7f1e5c8c3a3a28b841c12d693","A dry primitive equation model is used to explain how the quasi-biennial oscillation (QBO) of the tropical stratosphere can influence the troposphere, even in the absence of tropical convection anomalies and a variable stratospheric polar vortex. QBO momentum anomalies induce a meridional circulation to maintain thermal wind balance. This circulation includes zonal wind anomalies that extend from the equatorial stratosphere into the subtropical troposphere. In the presence of extratropical eddies, the zonalwind anomalies are intensified and extend downward to the surface. The tropospheric response differs qualitatively between integrations in which the subtropical jet is strong and integrations in which the subtropical jet is weak. While fluctuation- dissipation theory provides a guide to predicting the response in some cases, significant nonlinearity in others, particularly those designed to model the midwinter subtropical jet of the North Pacific, prevents its universal application. When the extratropical circulation is made zonally asymmetric, the response to the QBO is greatest in the exit region of the subtropical jet. The dry model is able to simulate much of the Northern Hemisphere wintertime tropospheric response to the QBO observed in reanalysis datasets and in long time integrations of the Whole Atmosphere Community Climate Model (WACCM). © 2011 American Meteorological Society."
"55469187200;","Circulation sensitivity to tropopause height",2006,"10.1175/JAS3762.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744479742&doi=10.1175%2fJAS3762.1&partnerID=40&md5=affca9f3a07f6e1fd61d8fff3cf800ea","The possibility that the tropopause could be lower during an ice-age cooling leads to an examination of the general sensitivity of global circulations to the tropopause height by altering a constant stratospheric temperature Ts in calculations with a dry, global, multilevel, spectral, primitive equation model subject to a simple Newtonian heating function. In general, lowering the tropopause by increasing the stratospheric temperature causes the jet stream to move to lower latitudes and the eddies to become smaller. Near the standard state with Ts = 200 K, the jets relocate themselves equatorward by 2° in latitude for every 5 K increase in the stratospheric temperature. A double-jet system, with centers at 30° and 60° latitude, occurs when the equatorial tropopause drops to 500 mb (for Ts = 250 K), with the high-latitude component extending throughout the stratosphere. The eddy momentum flux mainly traverses poleward across the standard jet at 40°, in keeping with the predominantly equatorward propagation of the planetary waves. But when the jet lies at 30° (for Ts = 225 K) the flux converges on the jet in keeping with planetary waves that propagate both equatorward and poleward. Two sets of such wave propagation occur in the double-jet system. As the troposphere becomes even shallower, the flux reverts to being primarily poleward across the jet (for Ts = 260 K) but then becomes uniquely primarily equatorward across the jet (for Ts = 275 K) before the circulation approaches extinction. Thus the existence of a predominantly poleward flux in the standard state appears to be parametrically fortuitous."
"6603806442;6602469258;55535579800;","Indian Ocean Dipole mode events and austral surface air temperature anomalies",2005,"10.1016/j.dynatmoce.2004.10.015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17544373059&doi=10.1016%2fj.dynatmoce.2004.10.015&partnerID=40&md5=3c802a89bf019d73d55ea80c864ddc5c","The impact of Indian Ocean Dipole (IOD) mode events on austral surface air temperature (SAT) variability was studied both by statistical analysis of observed/assimilated data and experiments with a mechanistic baroclinic atmospheric model. During the period of analysis (January 1958-December 1999), IOD events had the strongest impact on SAT anomalies during austral spring and hence, the analysis was focussed on this season. IOD events induced large scale, intercontinental correlations of SAT anomalies amongst Australia, Africa and South America. Surface temperature consistently rose (fell) abnormally and coherently in the subtropical regions of these continents during positive (negative) IOD events. Variability during non-IOD years was considerably weaker than during IOD years over these regions. Analysis of stream function anomalies at the 200 hPa level (source: NCEP/NCAR reanalysis) revealed a Rossby-wave train extending from the eastern Indian Ocean into the subtropical regions of the Pacific and Atlantic oceans. Further, the diagnosed Rossby-wave activity flux emanated from the eastern Indian Ocean and propagated along the subtropical and subpolar jet streams qualitatively in agreement with linear wave dynamics. Experiments with idealized forcing in a primitive equation mechanistic atmospheric model suggested that tropical convective anomalies in the Indian Ocean during IOD events likely affects the austral subtropics through stationary Rossby-wave propagation. © 2004 Elsevier B.V. All rights reserved."
"6602085180;55939078000;7004098470;6701448055;","The NRL Layered Global Ocean Model (NLOM) with an embedded mixed layer submodel: Formulation and tuning",2003,"10.1175/1520-0426(2003)020<1601:TNLGOM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346602696&doi=10.1175%2f1520-0426%282003%29020%3c1601%3aTNLGOM%3e2.0.CO%3b2&partnerID=40&md5=0fd7b73b7f5120c36330eca6327388d9","A bulk-type (modified Kraus-Turner) mixed layer model that is embedded within the Naval Research Laboratory (NRL) Layered Ocean Model (NLOM) is introduced. It is an independent submodel loosely coupled to NLOM's dynamical core, requiring only near-surface currents, the temperature just below the mixed layer, and an estimate of the stable mixed layer depth. Coupling is achieved by explicitly distributing atmospheric forcing across the mixed layer (which can span multiple dynamic layers), and by making the heat flux and thermal expansion of seawater dependent upon the mixed layer model's sea surface temperature (SST). An advantage of this approach is that the relative independence of the dynamical solution from the mixed layer allows the initial state for simulations with the mixed layer to be defined from existing near-global model simulations spun up from rest without a mixed layer (requiring many hundreds of model years). The goal is to use the mixed layer model in near-global multidecadal simulations with realistic 6-hourly atmospheric forcing from operational weather center archives. A minimum requirement therefore is that there be no drift in yearly average SST over time. The dynamical layer densities are relaxed to climatology as a standard part of the NLOM model design, and this ensures that the temperature just below the mixed layer provided to the mixed layer submodel does not drift. The density relaxation below the mixed layer does not significantly dampen anomalies even on interannual timescales because the anomalies are largely defined by layer thickness variations. When combined with calculating the latent and sensible heat flux using model SST, this is sufficient to keep SST on track without any explicit relaxation to the SST climatology. The sensitivity of the global ocean model to the choice of free Kraus-Turner parameters in the bulk mixed layer model is investigated by undertaking a tuning exercise to find a single set of parameters that provides a realistic SST from realistic atmospheric forcing over as much of the global ocean as possible. This is done by comparing the monthly Comprehensive Ocean Atmosphere Data Set (COADS) SST climatology to monthly averages from the model using a set of statistical metrics. A single set of mixed layer parameters is reported that gives excellent agreement with the SST climatology over most of the global ocean. The actual parameter values are probably specific to this coupled system, but the same methodology can be used to tune any mixed layer model with free parameters."
"7005022800;","On the assimilation of uncertain physical knowledge bases: Bayesian and non-Bayesian techniques",2002,"10.1016/S0309-1708(02)00064-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036704530&doi=10.1016%2fS0309-1708%2802%2900064-7&partnerID=40&md5=97fdf69605e70fda821f0df6ec6fabd7","We study the assimilation of uncertain physical knowledge across space and time, and we discuss the resulting issues of environmental inference and prediction. The term ""assimilation"" refers to a general framework that includes physical knowledge integration and processing activities in a variety of scientific disciplines (atmospheric data analysis and weather forecasting, environmental pollution mapping, exposure assessment, etc.). The choice of an adequate assimilation approach is primarily a conceptual modelling affair that is supported by the physical and logical features of the environmental situation under consideration, rather than merely relying on pure inductive schemes and statistical arguments. In many cases, the assimilation approach involves conditionalization techniques which enable it to merge various forms of site-specific data with modelling frameworks. We distinguish between interpretive conditionalization (which refers to the physical and epistemic characteristics of assimilation modelling) and formal conditionalization (which is a purely mathematical construction), and emphasize the importance of an adequate choice of the latter to represent the former. We point out the considerable improvements of the operational Bayesian conditionalization approach over the standard Bayesian rule. Statistical learning techniques are useful at the descriptive/correlation level of scientific inquiry, whereas the level of explanation/prediction is the domain of advanced operational techniques. An operational approach is based on an epistemic view in which the relevant natural processes are represented in terms of spatiotemporal random fields and the probability laws are expressed in terms of physically meaningful operators. The spirit of this view is to keep the field solutions consistent with the site-specific information (hard data, uncertain observations, etc.) while exactly satisfying the constraints arising from general knowledge sources (physical laws, primitive equations, scientific theories, etc.). Natural field probabilities in space and time are derived for non-Bayesian operational conditionals based on deductively sound inference, which are valid for a wide variety of knowledge bases. Analytical and numerical comparisons are made between Bayesian and non-Bayesian conditionals, and insight is gained in terms of examples and applications which cut across various earth science disciplines. Operational Bayesian conditionalization is a powerful and versatile component of assimilation modelling with many applications in environmental sciences, although in certain cases a non-Bayesian conditional (based on deductive logic and the characterization of physical connection) may provide a meaningful description of the data assimilation framework suggested by the laws of nature. © 2002 Elsevier Science Ltd. All rights reserved."
"55547140563;","A numerical study of loop current eddy interaction with topography in the Western Gulf of Mexico",1986,"10.1175/1520-0485(1986)016<1260:ANSOLC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001481998&doi=10.1175%2f1520-0485%281986%29016%3c1260%3aANSOLC%3e2.0.CO%3b2&partnerID=40&md5=a27d3ae322272e027972dbfe457f03c2","Anticyclones originating from the Loop Current are known to propagate into the western Gulf of Mexico. Their frequency of generation, their long lifetimes, and satellite data suggest that at any one time one or more eddies may occupy the Gulf. Given the eddy sizes (100-200 km) and geometric confinement of the Gulf, it would appear that there may be significant interactions of individual eddies and/or interactions of the eddies with bottom topography. These possibilities are explored through the use of a two-layer primitive equation model. Variable parameters in this model study are eddy strength, vertical structure, lateral friction, and initial location relative to topography. Results indicate that eddy motion is governed by two dynamical regimes depending on its lower layer rotational strength. Anticyclones with significant lower layer anticyclonic structure develop offshore directed self advective tendencies associated with topographic dispersion which induces asymmetry in the eddy. Eddies with weaker lower layer flow rapidly evolve through topographic dispersion to upper layer features and propagate independently of topography, interacting with the coastal boundary. The boundary can also include eddy asymmetry with resulting alongshore self advection tendencies leading to northward motion for anticyclones along the western boundary. © 1986 American Meteorological Society."
"56322979700;7004060399;","Stratospheric control of upward wave flux near the tropopause",2004,"10.1029/2003GL017965","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18144438541&doi=10.1029%2f2003GL017965&partnerID=40&md5=0226d3821caba32b3c6c0ea4f7824b15","Using an idealized, global primitive equation model of the stratosphere-troposphere system in which all tropospheric variability is surpressed, we demonstrate the existence of internal modes of stratospheric variability. The variability in our model is similar to that observed in the winter stratosphere, consisting of sudden-warming like, wave-driven decelerations of the polar vortex followed by a more gradual re-establishment of the vortex by the radiative forcing. Using a common index of the strength of the stratospheric vortex, we find patterns of downward propagation resembling those found in recent observations. In addition, our model exhibits considerable variability in the upward flux of wave activity into the stratosphere; this variability strongly anti-correlates with the index of the mid-upper stratospheric vortex, again in agreement with recent observations. Copyright 2004 by the American Geophysical Union."
"6701581833;6602864563;55885258700;","Space-time structure and dynamics of the forecast error in a coastal circulation model of the Gulf of Lions",2003,"10.1016/S0377-0265(02)00068-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037293807&doi=10.1016%2fS0377-0265%2802%2900068-4&partnerID=40&md5=6f89d16e03a2684e8d91c59112452a6b","The probability density function (pdf) of forecast errors due to several possible error sources is investigated in a coastal ocean model driven by the atmosphere and a larger-scale ocean solution using an Ensemble (Monte Carlo) technique. An original method to generate dynamically adjusted perturbation of the slope current is proposed. The model is a high-resolution 3D primitive equation model resolving topographic interactions, river runoff and wind forcing. The Monte Carlo approach deals with model and observation errors in a natural way. It is particularly well-adapted to coastal non-linear studies. Indeed higher-order moments are implicitly retained in the covariance equation. Statistical assumptions are made on the uncertainties related to the various forcings (wind stress, open boundary conditions, etc.), to the initial state and to other model parameters, and randomly perturbed forecasts are carried out in accordance with the a priori error pdf. The evolution of these errors is then traced in space and time and the a posteriori error pdf can be explored. Third- and fourth-order moments of the pdf are computed to evaluate the normal or Gaussian behaviour of the distribution. The calculation of Central Empirical Orthogonal Functions (Ceofs) of the forecast Ensemble covariances eventually leads to a physical description of the model forecast error subspace in model state space. The time evolution of the projection of the Reference forecast onto the first Ceofs clearly shows the existence of specific model regimes associated to particular forcing conditions. The Ceofs basis is also an interesting candidate to define the Reduced Control Subspace for assimilation and in particular to explore transitions in model state space. We applied the above methodology to study the penetration of the Liguro-Provençal Catalan Current over the shelf of the Gulf of Lions in north-western Mediterranean together with the discharge of the Rhône river. This region is indeed well-known for its intense topographic and atmospheric forcings. © 2003 Elsevier Science B.V. All rights reserved."
"7004060399;56744297600;","The three-dimensional structure of breaking Rossby waves in the polar wintertime stratosphere",2000,"10.1175/1520-0469(2000)057<3663:TTDSOB>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034319059&doi=10.1175%2f1520-0469%282000%29057%3c3663%3aTTDSOB%3e2.0.CO%3b2&partnerID=40&md5=acb452cb882534c5679d2746ba92a4ff","The three-dimensional nature of breaking Rossby waves in the polar wintertime stratosphere is studied using an idealized global primitive equation model. The model is initialized with a well-formed polar vortex, characterized by a latitudinal band of steep potential vorticity (PV) gradients. Planetary-scale Rossby waves are generated by varying the topography of the bottom boundary, corresponding to undulations of the tropopause. Such topographically forced Rossby waves then propagate up the edge of the vortex, and their amplification with height leads to irreversible wave breaking. These numerical experiments highlight several nonlinear aspects of stratospheric dynamics that are beyond the reach of both isentropic two-dimensional models and fully realistic GCM simulations. They also show that the polar vortex is contorted by the breaking Rossby waves in a surprisingly wide range of shapes. With zonal wavenumber-1 forcing, wave breaking usually initiates as a deep helical tongue of PV that is extruded from the polar vortex. This tongue is often observed to roll up into deep isolated columns, which, in turn, may be stretched and tilted by horizontal and vertical shears. The wave amplitude directly controls the depth of the wave breaking region and the amount of vortex erosion. At large forcing amplitudes, the wave breaking in the middle/lower portions of the vortex destroys the PV gradients essential for vertical propagation, thus shielding the top of the vortex from further wave breaking. The initial vertical structure of the polar vortex is shown to play an important role in determining the characteristics of the wave breaking. Perhaps surprisingly, initially steeper PV gradients allow for stronger vertical wave propagation and thus lead to stronger erosion. Vertical wind shear has the notable effect of tilting and stretching PV structures, and thus dramatically accelerating the downscale stirring. An initial decrease in vortex area with increasing height (i.e., a conical shape) leads to focusing of wave activity, which amplifies the wave breaking. This effect provides a geometric interpretation of the ""preconditioning"" that often precedes a stratospheric sudden warming event. The implications for stratospheric dynamics of these and other three-dimensional vortex properties are discussed.The three-dimensional nature of breaking Rossby waves in the polar wintertime stratosphere is studied using an idealized global primitive equation model. The model is initialized with a well-formed polar vortex, characterized by a latitudinal band of steep potential vorticity (PV) gradients. Planetary-scale Rossby waves are generated by varying the topography of the bottom boundary, corresponding to undulations of the tropopause. Such topographically forced Rossby waves then propagate up the edge of the vortex, and their amplification with height leads to irreversible wave breaking. These numerical experiments highlight several nonlinear aspects of stratospheric dynamics that are beyond the reach of both isentropic two-dimensional models and fully realistic GCM simulations. They also show that the polar vortex is contorted by the breaking Rossby waves in a surprisingly wide range of shapes. With zonal wavenumber-1 forcing, wave breaking usually initiates as a deep helical tongue of PV that is extruded from the polar vortex. This tongue is often observed to roll up into deep isolated columns, which, in turn, may be stretched and tilted by horizontal and vertical shears. The wave amplitude directly controls the depth of the wave breaking region and the amount of vortex erosion. At large forcing amplitudes, the wave breaking in the middle/lower portions of the vortex destroys the PV gradients essential for vertical propagation, thus shielding the top of the vortex from further wave breaking. The initial vertical structure of the polar vortex is shown to play an important role in determining the characteristics of the wave breaking. Perhaps surprisingly, initially steeper PV gradients allow for stronger vertical wave propagation and thus lead to stronger erosion. Vertical wind shear has the notable effect of tilting and stretching PV structures, and thus dramatically accelerating the downscale stirring. An initial decrease in vortex area with increasing height (i.e., a conical shape) leads to focusing of wave activity, which amplifies the wave breaking. This effect provides a geometric interpretation of the 'preconditioning' that often precedes a stratospheric sudden warming event. The implications for stratospheric dynamics of these and other three-dimensional vortex properties are discussed."
"6701395093;35548133700;","Seasonal differences in the stationary response of a linearized primitive equation model: prospects for long-range weather forecasting?",1980,"10.1175/1520-0469(1980)037<2169:SDITSR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019117263&doi=10.1175%2f1520-0469%281980%29037%3c2169%3aSDITSR%3e2.0.CO%3b2&partnerID=40&md5=a3a4ee47fefe8bba41a12dd4582c05d0","A linear steady-state primitive equation model has been developed for the computation of stationary atmospheric waves that are forced by anomalies in surface conditions. The response of the model indicates that a heating in the tropics can have a substantial influence on the middle and high latitudes, provided that part of the heating is in the westerlies.-from Authors"
"7203088716;","Dynamical control of the middle atmosphere",2012,"10.1007/s11214-011-9841-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863586096&doi=10.1007%2fs11214-011-9841-5&partnerID=40&md5=ff6335f5b1485b49030f534b303ce911","This review recapitulates the concept of the wave-driven residual circulation in the stratosphere and mesosphere. The residual circulation is defined as the conventional mean meridional circulation corrected by the quasi-linear Stokes drift due to atmospheric waves. Only when the zonal-mean primitive equations are transformed using the residual circulation, they reflect the causality arising from the Eliassen-Palm (EP) theorem. The EP theorem states that the proper wave-mean flow interaction, defined as the EP flux divergence, vanishes for waves that are linear, conservative, and steady. In the real atmosphere, this theorem is violated mainly due to wave breaking and turbulence. The resulting EP flux divergence then drives a residual circulation which causes the observed substantial deviations from some hypothetical radiatively determined state. With regard to this dynamical control we discuss the different contributions of Rossby waves and gravity waves. Recapitulation of Lindzen's theory of gravity-wave saturation allows us to interpret various phenomena in the upper mesosphere such as interhemispheric coupling or modulations of the gravity-wave driven branch of the residual circulation by solar proton effects and thermal tides. In addition we discuss the relative importance of changes in radiative transfer and tropospheric gravity-wave sources on the long-term temperature trends in the summer mesosphere. © 2011 Springer Science+Business Media B.V."
"7004157687;7004177863;","A case study of lee waves over the Lake District in northern England",1993,"10.1002/qj.49711951102","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027789654&doi=10.1002%2fqj.49711951102&partnerID=40&md5=ecde54d46c95063994f512587dad9839","The structure and intensity of stationary, orographically‐forced over the Lake District and northern Pennines on he afternoon of 26 November 1991 is determined through a combination of field observations and high‐resolution numerical modelling. Observations were provided by the Meteorological Office's C130 aircraft at four different levels and by five radisondes (of differing ascent rates) released in rapid succession from an observing station located on the Cumbrian coast. Vertical velocity was inferred from both of these data sources and, with the help of satellite imagery, it was possible to build up a comprehensive picture of the lee wave structure. In addition, a non‐hydrostatic primitive equation model was run with a 2‐km grid, covering a 180‐km square region of the northern Pennines, in an attempt to simulate the gravity wave motion observed. The model was initialized with an upstream profile formed by merging a descent profile obtained from the aircraft with one from the sondes. The model orography was defined using a terrain height data‐set with 500‐m resolution and with some smoothing to the model grid. After about four hours of integration the model achieves a quasi‐steady state with strong lower‐tropospheric lee waves. Verification on the model response was sought by comparing the vertical velocity in the model along the paths of the aircraft and sondes with that actually deduced from the observations. The overall agreement of the simulated amplitude and phase of the lee waves with that observed is very encouraging—as found in a different case study (Shutts 1992). The success of the model in predicting lee wave motion gives strong support for the use of these models for the development of gravity‐wave‐drag parametrization schemes. The domain‐averaged surface frictional stress was found to be much larger than the wave drag, and consistent with the high roughness lengths likely in the case of mountainous terrain. Copyright © 1993 Royal Meteorological Society"
"7103413199;7402435469;55712683400;55910202200;37071745600;55712772000;55910010100;6701782816;17341093800;6504089753;55910431900;7201841885;7003554893;8255473900;7202954964;7401945370;55286185400;7005808242;35497573900;56224155200;55686667100;7102857642;24468389200;22137065500;6603371044;8539422800;57211224269;7006263720;","The aqua-planet experiment (APE): CONTROL SST simulation",2013,"10.2151/jmsj.2013-A02","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886797645&doi=10.2151%2fjmsj.2013-A02&partnerID=40&md5=5391c468dca1a27b4c52b8a38b8e8e32","Climate simulations by 16 atmospheric general circulation models (AGCMs) are compared on an aqua-planet, a water-covered Earth with prescribed sea surface temperature varying only in latitude. The idealised configuration is designed to expose differences in the circulation simulated by different models. Basic features of the aqua-planet climate are characterised by comparison with Earth. The models display a wide range of behaviour. The balanced component of the tropospheric mean flow, and mid-latitude eddy covariances subject to budget constraints, vary relatively little among the models. In contrast, differences in damping in the dynamical core strongly influence transient eddy amplitudes. Historical uncertainty in modelled lower stratospheric temperatures persists in APE. Aspects of the circulation generated more directly by interactions between the resolved fluid dynamics and parameterized moist processes vary greatly. The tropical Hadley circulation forms either a single or double inter-tropical convergence zone (ITCZ) at the equator, with large variations in mean precipitation. The equatorial wave spectrum shows a wide range of precipitation intensity and propagation characteristics. Kelvin mode-like eastward propagation with remarkably constant phase speed dominates in most models. Westward propagation, less dispersive than the equatorial Rossby modes, dominates in a few models or occurs within an eastward propagating envelope in others. The mean structure of the ITCZ is related to precipitation variability, consistent with previous studies. The aqua-planet global energy balance is unknown but the models produce a surprisingly large range of top of atmosphere global net flux, dominated by differences in shortwave reflection by clouds. A number of newly developed models, not optimised for Earth climate, contribute to this. Possible reasons for differences in the optimised models are discussed. The aqua-planet configuration is intended as one component of an experimental hierarchy used to evaluate AGCMs. This comparison does suggest that the range of model behaviour could be better understood and reduced in conjunction with Earth climate simulations. Controlled experimentation is required to explore individual model behaviour and investigate convergence of the aqua-planet climate with increasing resolution. © 2013, Meteorological Society of Japan."
"8687063000;35497573900;","Cloud-system resolving simulations with the NASA Goddard Earth Observing System global atmospheric model (GEOS-5)",2011,"10.1029/2011GL048438","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052235743&doi=10.1029%2f2011GL048438&partnerID=40&md5=c9a8ed3caff1f18d65bf8a705ba6e3f0","The NASA Global Modeling and Assimilation Office (GMAO) has developed a global non-hydrostatic cloud-system resolving capability within the NASA Goddard Earth Observing System global atmospheric model version 5 (GEOS-5). Using a non-hydrostatic finite-volume dynamical core coupled with advances in the moist physics and convective parameterization the model has been used to perform cloud-system resolving experiments at resolutions as fine as 3.5-to 14-km globally. An overview of preliminary results highlights the development of mid-latitude cyclones, the overall representation of global tropical convection, intense convective activity within the eye wall and outer rain bands of the 2009 Atlantic hurricane Bill validated by satellite observations, and the seasonal predictability of global tropical cyclone activity with realistic intensities. These preliminary results provide motivation for the use of GEOS-5 to simulate multi-scale convective systems within a global model at cloud resolving resolutions. Copyright 2011 by the American Geophysical Union."
"6602249313;35514012200;8884425800;","A wind comparison study using an ocean general circulation model for the 1997-1998 El Niño",2001,"10.1029/1999jc000055","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035086790&doi=10.1029%2f1999jc000055&partnerID=40&md5=d15299c4d8e3385c860e7878344d9d7c","Predictions of the 1997-1998 El Niño exhibited a wide range of forecast skill that were dependent, in part, on the wind-driven initial conditions for the ocean. In this study the results of a reduced gravity, primitive equation, sigma coordinate ocean general circulation model are compared and contrasted when forced by several different wind products for the 1997-1998 El Niño/La Niña. The different wind products include atmospheric model winds, satellite wind products, and a subjective analysis of ship and in situ winds. The model results are verified against fields of observed sea level anomalies from TOPEX/Poseidon data, sea surface temperature analyses, and subsurface temperature from the Tropical Atmosphere-Ocean buoy array. Depending on which validation data type one chooses, different wind products provide the best forcing fields for simulating the observed signal. In general, the model results forced by satellite winds provide the best simulations of the spatial and temporal signal of the observed sea level. This is due to the accuracy of the meridional gradient of the zonal wind stress component that these products provide. Differences in wind forcing also affect subsurface dynamics and thermodynamics. For example, the wind products with the weakest magnitude best reproduce the sea surface temperature (SST) signal in the eastern Pacific. For these products the mixed layer is shallower, and the thermocline is closer to the surface. For such simulations the subsurface thermocline variability influences the variation in SST more than in reality. The products with the greatest wind magnitude have a strong cold bias of >1.5°C in the eastern Pacific because of increased mixing. The satellite winds along with the analysis winds correctly reproduce the depth of the thermocline and the general subsurface temperature structure. Copyright 2001 by the American Geophysical Union."
"7005965757;6604083733;7006518289;7402349817;7202860540;","A general circulation experiment with a coupled atmosphere, ocean and sea ice model.",1980,"10.1175/1520-0485(1980)010<1887:agcewa>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0018936146&doi=10.1175%2f1520-0485%281980%29010%3c1887%3aagcewa%3e2.0.co%3b2&partnerID=40&md5=98e6b0af29b30f149cf3a574e78ce77c","This paper describes the construction and results of a comprehensive, three-dimensional general circulation model (GCM) of the earth's climate. The model, developed at the National Centre for Atmospheric Research (NCAR) , links separate existing models of the atmosphere, ocean and sea ice. The atmospheric model is a version of the third-generation NCAR GCM which has a relatively complete treatment of physical processes. It uses a generalized vertical coordinate with eight layers (3 km thick) and 5SUP horizontal grid spacing over the entire globe. The ocean model, using the primitive equations and the hydrostatic and Boussinesq approximations , was changed to the world domain from an earlier model developed by Bryan (1969) and reprogrammed by Semtner (1974). The model has four unequally spaced vertical layers and 5SUP horizontal grid structure. The sea ice model is a simple thermodynamic model using simplified calculation of heat flux through sea ice. (from authors abstract)"
"6603612894;16536179700;","Surface exchanges of sensible and latent heat in a 10‐level model atmosphere",1970,"10.1002/qj.49709640812","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84984005721&doi=10.1002%2fqj.49709640812&partnerID=40&md5=5830dcb6b5f3208af3c433e88b630cd7","This paper describes a representation of the distribution of sensible and latent heat from the surface through the atmospheric boundary layer which has been formulated for use in a 10‐level primitive equation model atmosphere. The transfer process is represented in two parts : (i) the transfer of energy across the Earth's surface into the lowermost 100 mb layer of the model atmosphere; and (ii) the subsequent redistribution of this energy through two or more such layers by small‐scale convection. The fluxes of energy across the surface are calculated using empirical ‘bulk aerodynamic’ relationships. In land regions consideration of the energy balance at the surface is also necessary, and diurnal variations of radiation are taken into account. The redistribution of energy by small‐scale convection is represented by convective adjustments which ensure that a certain neutral lapse rate of temperature is never exceeded. Some results of the incorporation of these effects into the 10‐level model are described. Copyright © 1970 Royal Meteorological Society"
"7402033627;8285351400;7005342702;","Large-eddy simulation of marine atmospheric boundary layers above a spectrum of moving waves",2014,"10.1175/JAS-D-14-0095.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910143584&doi=10.1175%2fJAS-D-14-0095.1&partnerID=40&md5=2e157ed6c874fe48e87612aec1a4bc3a","Momentum and scalar transport in the marine atmospheric boundary layer (MABL) is driven by a turbulent mix of winds, buoyancy, and surface gravity waves. To investigate the interaction between these processes, a large-eddy simulation (LES) model is developed with the capability to impose a broadband spectrum of time-varying finite-amplitude surface waves at its lower boundary. The LES model adopts a Boussinesq flow model and integrates the governing equations on a time-varying, surface-fitted, nonorthogonal mesh using cell-centered variables with special attention paid to the solution of the pressure Poisson equation near the wavy boundary. Weakly unstable MABLs are simulated with geostrophic winds increasing from 5 to 25ms-1 and wave age varying from swell-dominated to wind-wave equilibrium. The simulations illustrate cross-scale coupling as wave-impacted near-surface turbulence transitions into shear-convective rolls with increasing distance from the water. In a regime with swell, low winds, and weak heating, wave-induced vertical velocity and pressure signals are readily observed well above the standard reference height ζa = 10 m. At wind-wave equilibrium, the small-scale wave-induced signals are detectable only near the water surface. Below ζa, a nearly-constant-flux layer is observed where the momentum flux carried by turbulence, form stress, and subgrid-scale motions shifts with varying wave age and distance above the water. The spectral content of the surface form stress is wave-age dependent, especially at low wavenumbers. The LES wind profiles deviate from Monin-Obukhov similarity theory in nonequilibrium wind-wave conditions, and entrainment is greatly enhanced by shear-induced engulfment events. © 2014 American Meteorological Society."
"15836555700;","A global hexagonal C-grid non-hydrostatic dynamical core (ICON-IAP) designed for energetic consistency",2013,"10.1002/qj.1960","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873302432&doi=10.1002%2fqj.1960&partnerID=40&md5=31102ac497a0d03a518d2f270c9f2e59","This study describes a new global non-hydrostatic dynamical core (ICON-IAP: Icosahedral Nonhydrostatic model at the Institute for Atmospheric Physics) on a hexagonal C-grid which is designed to conserve mass and energy. Energy conservation is achieved by discretizing the antisymmetric Poisson bracket which mimics correct energy conversions between the different kinds of energy (kinetic, potential, internal). Because of the bracket structure this is even possible in a complicated numerical environment with (i) the occurrence of terrain-following coordinates with all the metric terms in it, (ii) the horizontal C-grid staggering on the Voronoi mesh and the complications induced by the need for an acceptable stationary geostrophic mode, and (iii) the necessity for avoiding Hollingsworth instability. The model is equipped with a Smagorinsky-type nonlinear horizontal diffusion. The associated dissipative heating is accounted for by the application of the discrete product rule for derivatives. The time integration scheme is explicit in the horizontal and implicit in the vertical. In order to ensure energy conservation, the Exner pressure has to be off-centred in the vertical velocity equation and extrapolated in the horizontal velocity equation. Test simulations are performed for small-scale and global-scale flows. A test simulation of linear non-hydrostatic flow over a rough mountain range shows the theoretically expected gravity wave propagation. The baroclinic wave test is extended to 40 days in order to check the Lorenz energy cycle. The model exhibits excellent energy conservation properties even in this strongly nonlinear and dissipative case. The Held-Suarez test confirms the reliability of the model over even longer time-scales. © 2012 Royal Meteorological Society."
"12645508600;8656775300;6602134946;7103102923;6701616786;6701628532;6602262969;","Modeling the primary and secondary productions of the southern Benguela upwelling system: A comparative study through two biogeochemical models",2005,"10.1029/2004GB002427","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33244478143&doi=10.1029%2f2004GB002427&partnerID=40&md5=50dcbfb4e04da9b53ea401b4d4c3acad","A three-dimensional primitive equation model, the regional ocean modelling Systems (ROMS), coupled to two biogeochemical configurations (NPZD and N2p2Z2D2) was used to study the dynamics of the first trophic levels of the pelagic food web in the southern Benguela upwelling system. The domain extends from the Agulhas Bank bordered by the Agulhas Current to 27°S on the west coast of South Africa. The circulation is driven by monthly climatologies of atmospheric forcing fields. The NPZD ecosystem model consists of four state variables: nutrient (nitrate), phytoplankton, zooplankton and detritus. In the N2P2Z2D2 model, ammonium has been added and the three other variables have been divided into small and large organism or detritus. Both models are able to reproduce the spatio-temporal phytoplankton distribution. Along the west coast, chlorophyll concentrations maxima are associated to surface waters. Westward dominating winds generate the lowest chlorophyll concentrations encountered in winter. The small phytoplankton organisms simulated by the N2P2Z2D2 model are responsible for a weaker chlorophyll inshore/offshore gradient, in closer agreement with observations. Transitions from a regime dominated by new production (high f ratio) to one dominated by regenerated production (low f ratio) happen to be abrupt, underlying the constant competition between small and large organisms with regard to upwelling induced nutrient inputs. On the Agulhas Bank, the summer enrichment is associated with subsurface maxima, while in winter, mixing by storms results in a homogeneous phytoplankton distribution in the water column. Regenerated production plays an important role in maintaining the total phytoplankton growth. Zooplankton biomass reflects the overall patterns of chlorophyll a concentrations with diffences between the west coast and the Agulhas Bank, consistent with data, and its distribution exhibits an clear seasonal contrast. The seasonality of small and large zooplankton in the N2P2Z2D2 model is quite distinct, which allows, from the Agulhas Bank to St. Helen Bay, a food continuum for fish larvae. This was not achieved with the smaller NPZD model, emphasizing the importance of representing the appropriate level of complexity to characterize food availability for higher trophic levels. Copyright 2005 by the American Geophysical Union."
"56292334100;6701313416;7006550959;7102367341;","Storm-track organization and variability in a simplified atmospheric global circulation model",1998,"10.1256/smsqj.54801","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031682348&doi=10.1256%2fsmsqj.54801&partnerID=40&md5=d0367b5090d28fedf7ff8b6e007c9b18","A storm track is simulated in a coarse-resolution multilevel primitive-equation model with linear surface friction and heating terms. A restoration temperature distribution consisting of a dipole embedded in a zonally symmetric profile forces the model to simulate the surface heating. Three simulations, each with a different dipole orientation, are performed to test the sensitivity of storm-track organization to the external forcing field. The climatological time-mean circulation and the transient disturbances of the reference simulation agree well with observations of northern hemisphere wintertime storm tracks. Local energetics show that baroclinic instability is responsible for the enhanced eddy kinetic energy downstream of the jet, and the downstream end of the storm track results from the barotropic conversions of eddy kinetic energy to the time-mean flow. Low-frequency fluctuations with a period of about 50 days associated with a retrograding large-scale wave pattern are identified by a complex empirical-orthogonal-function analysis of the vertically averaged stream function. A composite life cycle of the low-frequency variability reveals the growth and decay of a blocking anticyclone downstream of the storm track. A cyclogenesis initiated by an eastward-propagating wave train is observed a few days before the amplitude of the low-frequency anomaly attains its peak. The net forcing of the high-frequency eddies contributes to the growth and decay of the blocking anticyclone. The results suggest that the occurrence of the blocking-like event is part of the storm-track dynamics."
"7004955047;7102440510;7202546211;12645213000;","An oceanographic nowcast/forecast system for the Red Sea",1997,"10.1029/97JC01919","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031400215&doi=10.1029%2f97JC01919&partnerID=40&md5=ec7c87e11f77e9188727828fa365f109","We describe the application of a nowcast/forecast system for three- dimensional currents, temperature, and salinity to the Red Sea. The modeling system is constructed around a high-resolution (6 × 7 km) primitive-equation numerical circulation model with complete thermodynamics and an imbedded turbulence closure submodel. It is coupled to near-real-time databases containing meteorological forecasts and remotely sensed and in situ temperature and salinity data. The temperature and salinity data are ingested into the model daily using a nudged objective analysis technique. Because the Red Sea is a relatively narrow basin bounded by typically high and complex orography, a single-layer atmospheric boundary layer submodel has been used to increase the effective resolution of the original 40-km resolution meteorological fields by taking into account orographic steering of the low-level winds. In order to validate the modeling system, two very complete hydrographic surveys of the Red Sea were undertaken, and their results are described. Both the surveys and the modeling system nowcasts demonstrate that the circulation pattern of the Red Sea is variable and often composed of a series of eddies or subgyres, mainly anticyclones. Immediately before one survey, the winds tended to be along axis, while just before the second, they tended to be cross axis. The Red Sea circulation was much more eddy-like when the winds were cross-axis. By forcing the modeling system with and without orographically steered winds we were able to establish that the complex eddy structure is a response to a wind field which can be highly structured and vorticity rich because of interaction with the high and variable adjacent orography. When the winds are more along axis, there is less interaction with the adjacent orography, and consequently, there are fewer eddies in the Red Sea. Copyright 1997 by the American Geophysical Union."
"7402311929;57200530823;","Numerical prediction of precipitation and river flow over the Russian river Watershed during the January 1995 California storms",1996,"10.1175/1520-0477(1996)077<0101:NPOPAR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029656563&doi=10.1175%2f1520-0477%281996%29077%3c0101%3aNPOPAR%3e2.0.CO%3b2&partnerID=40&md5=62de9badb6a6eea3f13832e270ce7273","Precipitation and river flow during a January 1995 flood event over the Russian River watershed in the northern Coastal Range of California were simulated using the University of California Lawrence Livermore National Laboratory's Coupled Atmosphere-River Flow Simulation (CARS) System. The CARS System unidirectionally links a primitive equation atmospheric mesoscale model to a physically based, fully distributed hydrologic model by employing an automated land analysis system. Using twice-daily National Meteorological Center eta model initial data to provide the large-scale forcing to the mesoscale model, the CARS System has closely simulated the observed river flow during the flooding stage, where the simulated river flow was within 10% of the observed river flow at the Hopland gauge station on the Russian River."
"6506340624;7006306835;","The general circulation model precipitation bias over the southwestern equatorial Indian Ocean and its implications for simulating the South Asian monsoon",2013,"10.1007/s00382-012-1347-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874946750&doi=10.1007%2fs00382-012-1347-7&partnerID=40&md5=a9c86e2f2b89209fc72fbee0cdca7ec0","Most of current general circulation models (GCMs) show a remarkable positive precipitation bias over the southwestern equatorial Indian Ocean (SWEIO), which can be thought of as a westward expansion of the simulated IO convergence zone toward the coast of Africa. The bias is common to both coupled and uncoupled models, suggesting that its origin does not stem from the way boundary conditions are specified. The spatio-temporal evolution of the precipitation and associated three-dimensional atmospheric circulation biases is comprehensively characterized by comparing the GFDL AM3 atmospheric model to observations. It is shown that the oceanic bias, which develops in spring and reduces during the monsoon season, is associated to a consistent precipitation and circulation anomalous pattern over the whole Indian region. In the vertical, the areas are linked by an anomalous Hadley-type meridional circulation, whose northern branch subsides over northeastern India significantly affecting the monsoon evolution (e. g., delaying its onset). This study makes the case that the precipitation bias over the SWEIO is forced by the model excess response to the local meridional sea surface temperature (SST) gradient through enhanced near-surface meridional wind convergence. This is suggested by observational evidence and supported by AM3 sensitivity experiments. The latter show that relaxing the magnitude of the meridional SST gradient in the SWEIO can lead to a significant reduction of both local and large-scale precipitation and circulation biases. The ability of local anomalies over the SWEIO to force a large-scale remote response to the north is further supported by numerical experiments with the GFDL spectral dry dynamical core model. By imposing a realistic anomalous heating source over the SWEIO the model is able to reproduce the main dynamical features of the AM3 bias. These results indicate that improved GCM simulations of the South Asian summer monsoon could be achieved by reducing the springtime model bias over the SWEIO. Deficiencies in the atmospheric model, and in particular in the convective parameterization, are suggested to play a key role. Finally, the important mechanism controlling the simulated precipitation distribution over South Asia found here should be considered in the interpretation and attribution of regional precipitation variation under climate change. © 2012 Springer-Verlag."
"7403326970;13609115600;7402523567;6507506899;55724460500;55895104800;51663392900;57201410408;9245000500;6603230487;7202386372;7005131869;11940132500;6603871013;7202152636;","An intercomparison of T-REX mountain-wave simulations and implications for mesoscale predictability",2011,"10.1175/MWR-D-10-05042.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958706155&doi=10.1175%2fMWR-D-10-05042.1&partnerID=40&md5=e735288e64fe73e74b02ac07b4f5a255","Numerical simulations of flow over steep terrain using 11 different nonhydrostatic numerical models are compared and analyzed. A basic benchmark and five other test cases are simulated in a two-dimensional framework using the same initial state, which is based on conditions during Intensive Observation Period (IOP) 6 of the Terrain-Induced Rotor Experiment (T-REX), in which intense mountain-wave activity was observed. All of the models use an identical horizontal resolution of 1 km and the same vertical resolution. The six simulated test cases use various terrain heights: a 100-m bell-shaped hill, a 1000-m idealized ridge that is steeper on the lee slope, a 2500-m ridge with the same terrain shape, and a cross-Sierra terrain profile. The models are tested with both free-slip and no-slip lower boundary conditions. The results indicate a surprisingly diverse spectrum of simulated mountain-wave characteristics including lee waves, hydraulic-like jump features, and gravity wave breaking. The vertical velocity standard deviation is twice as large in the free-slip experiments relative to the no-slip simulations. Nevertheless, the no-slip simulations also exhibit considerable variations in the wave characteristics. The results imply relatively low predictability of key characteristics of topographically forced flows such as the strength of downslope winds and stratospheric wave breaking. The vertical flux of horizontal momentum, which is a domain-integrated quantity, exhibits considerable spread among the models, particularly for the experiments with the 2500-m ridge and Sierra terrain. The differences among the various model simulations, all initialized with identical initial states, suggest that model dynamical cores may be an important component of diversity for the design of mesoscale ensemble systems for topographically forced flows. The intermodel differences are significantly larger than sensitivity experiments within a single modeling system. © 2011 American Meteorological Society."
"7203088716;","Sensitivity of the upper mesosphere to the Lorenz energy cycle of the troposphere",2009,"10.1175/2008JAS2735.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66949111552&doi=10.1175%2f2008JAS2735.1&partnerID=40&md5=366fc5b4fe88bc1df9fb940f44631fdf","The concept of a mechanistic general circulation model that explicitly simulates the gravity wave drag in the extratropical upper mesosphere in a self-consistent fashion is proposed. The methodology consists of 1) a standard spectral dynamical core with high resolution, 2) idealized formulations of radiative and latent heating, and 3) a hydrodynamically consistent turbulent diffusion scheme with the diffusion coefficients based on Smagorinsky's generalized mixing-length formulation and scaled by the Richardson criterion. The model reproduces various mean and variable features of the wave-driven general circulation from the boundary layer to the mesopause region during January. The dissipation of mesoscale kinetic energy (defined as the frictional heating due to the mesoscale flow) in the extratropical troposphere is found to indicate the tropospheric gravity wave sources relevant for the mesosphere/lower thermosphere. This motivates a sensitivity experiment in which the large-scale differential heating is perturbed such that the Lorenz energy cycle as measured by the globally integrated frictional heating becomes stronger. As a result, both the resolved gravity wave activity and the dissipation of mesoscale kinetic energy in the extratropical troposphere are amplified. These changes have strong remote effects in the summer mesopause region, where the gravity wave drag, the residual meridional wind, and the frictional heating shift to lower altitudes. Furthermore, temperatures decrease below the summer mesopause and increase farther up, which is accompanied by an anomalous eastward wind component around the mesopause. © 2009 American Meteorological Society."
"6603061884;6701465412;55986838800;","Advanced insights into sources of vertical velocity in the ocean",2006,"10.1007/s10236-005-0050-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845959782&doi=10.1007%2fs10236-005-0050-1&partnerID=40&md5=0448d5b9185e18f9479289d106514784","Estimating vertical velocity in the oceanic upper layers is a key issue for understanding ocean dynamics and the transport of biogeochemical elements. This paper aims to identify the physical sources of vertical velocity associated with sub-mesoscale dynamics (fronts, eddies) and mixed-layer depth (MLD) structures, using (a) an ocean adaptation of the generalized Q-vector form of the ω-equation deduced from a primitive equation system which takes into account the turbulent buoyancy and momentum fluxes and (b) an application of this diagnostic method for an ocean simulation of the Programme Océan Multidisciplinaire Méso Echelle (POMME) field experiment in the North-Eastern Atlantic. The approach indicates that w-sources can play a significant role in the ocean dynamics and strongly depend on the dynamical structure (anticyclonic eddy, front, MLD, etc.). Our results stress the important contribution of the ageostrophic forcing, even under quasi-geostrophic conditions. The turbulent w-forcing was split into two components associated with the spatial variability of (a) the buoyancy and momentum (Ekman pumping) surface fluxes and (b) the MLD. Process (b) represents the trapping of the buoyancy and momentum surface energy into the MLD structure and is identified as an atmosphere/oceanic mixed-layer coupling. The momentum-trapping process is 10 to 100 times stronger than the Ekman pumping and is at least 1,000 times stronger than the buoyancy w-sources. When this decomposition is applied to a filamentary mixed-layer structure simulated during the POMME experiment, we find that the associated vertical velocity is created by trapping the surface wind-stress energy into this structure and not by Ekman pumping. © Springer-Verlag 2006."
"35425197200;6603405653;7401580735;57208455668;7101801476;8687063000;57198752297;7201437448;6701552501;6507988742;","Hurricane forecasting with the high-resolution NASA finite volume general circulation model",2005,"10.1029/2004GL021513","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20244363793&doi=10.1029%2f2004GL021513&partnerID=40&md5=79bcb71563b141010cca6d657aa74353","A high-resolution finite volume general circulation model (fvGCM), resulting from a development effort of more than ten years, is now being run operationally at the NASA Goddard Space Flight Center and Ames Research Center. The model is based on a finite volume dynamical core with terrain-following Lagrangian control volume discretization and performs efficiently on massive parallel architectures. The computational efficiency allows simulations at a resolution of a quarter of a degree, which is double the resolution currently adopted by most global models in operational weather centers. Such fine global resolution brings us closer to overcoming a fundamental barrier in global atmospheric modeling for both weather and climate, because tropical cyclones can be more realistically represented. In this work, preliminary results are shown. Fifteen simulations of four Atlantic tropical cyclones in 2002 and 2004, chosen because of varied difficulties presented to numerical weather forecasting, are performed. The fvGCM produces very good forecasts of these tropical systems, adequately resolving problems like erratic track, abrupt recurvature, intense extratropical transition, multiple landfall and reintensification, and interaction among vortices. Copyright 2005 by the American Geophysical Union."
"7101959827;55716319700;","The implications of tropical Rossby waves for tropical tropopause cirrus formation and for the equatorial upwelling of the brewer-dobson circulation",2003,"10.1175/1520-0469(2003)060<0247:TIOTRW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242338683&doi=10.1175%2f1520-0469%282003%29060%3c0247%3aTIOTRW%3e2.0.CO%3b2&partnerID=40&md5=7b5406bd0dbc6289ea7523e083eb996a","This study puts forward a mechanism for the observed upwelling in the tropical upper troposphere and lower stratosphere. In this hypothesis, the tropical upwelling is driven by momentum transport by Rossby waves that are generated by tropical convection. To test this hypothesis, model runs are conducted using an axisymmetric, global, primitive equation model. In these runs, the effect of Rossby waves is included by driving the model with observed fields of large-scale eddy momentum flux convergence. The resulting overturning circulation includes both meridional flow from the intertropical convergence zone (ITCZ) to the equator and rising motion in the tropical tropopause transition layer (TTL). This circulation therefore helps to explain the transport of moisture from the lower portion of the TTL in the ITCZ to the equatorial cold-point tropopause, where tropopause cirrus layers frequently occur."
"6602737813;6701618837;7004696542;9274531600;7103211168;","Sensitivity of age-of-air calculations to the choice of advection scheme",2000,"10.1175/1520-0469(2000)057<3185:SOAOAC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034300479&doi=10.1175%2f1520-0469%282000%29057%3c3185%3aSOAOAC%3e2.0.CO%3b2&partnerID=40&md5=4bf22dafbc85113dab5b1fd8ffa6693e","The age of air has recently emerged as a diagnostic of atmospheric transport unaffected by chemical parameterizations, and the features in the age distributions computed in models have been interpreted in terms of the models' large-scale circulation field. This study shows, however, that in addition to the simulated large-scale circulation, three-dimensional age calculations can also be affected by the choice of advection scheme employed in solving the tracer continuity equation. Specifically, using the 3.0°latitude X 3.6°longitude and 40 vertical level version of the Geophysical Fluid Dynamics Laboratory SKYHI GCM and six online transport schemes ranging from Eulerian through semi-Lagrangian to fully Lagrangian, it will be demonstrated that the oldest ages are obtained using the nondiffusive centered-difference schemes while the youngest ages are computed with a semi-Lagrangian transport (SLT) scheme. The centered-difference schemes are capable of producing ages older than 10 years in the mesosphere, thus eliminating the 'young bias' found in previous age-of-air calculations. At this stage, only limited intuitive explanations can be advanced for this sensitivity of age-of-air calculations to the choice of advection scheme. In particular, age distributions computed online with the National Center for Atmospheric Research Community Climate Model (MACCM3) using different varieties of the SLT scheme are substantially older than the SKYHI SLT distribution. The different varieties, including a noninterpolating-in-the-vertical version (which is essentially centered-difference in the vertical), also produce a narrower range of age distributions than the suite of advection schemes employed in the SKYHI model. While additional MACCM3 experiments with a wider range of schemes would be necessary to provide more definitive insights, the older and less variable MACCM3 age distributions can plausibly be interpreted as being due to the semi-implicit semi-Lagrangian dynamics employed in the MACCM3. This type of dynamical core (employed with a 60-min time step) is likely to reduce SLT's interpolation errors that are compounded by the short-term variability characteristic of the explicit centered-difference dynamics employed in the SKYHI model (time step of 3 min). In the extreme case of a very slowly varying circulation, the choice of advection scheme has no effect on two-dimensional (latitude-height) age-of-air calculations, owing to the smooth nature of the transport circulation in 2D models. These results suggest that nondiffusive schemes may be the preferred choice for multiyear simulations of tracers not overly sensitive to the requirement of monotonicity (this category includes many greenhouse gases). At the same time, age-of-air calculations offer a simple quantitative diagnostic of a scheme's long-term diffusive properties and may help in the evaluation of dynamical cores in multiyear integrations. On the other hand, the sensitivity of the computed ages to the model numerics calls for caution in using age of air as a diagnostic of a GCM's large-scale circulation field.The age of air has recently emerged as a diagnostic of atmospheric transport unaffected by chemical parameterizations, and the features in the age distributions computed in models have been interpreted in terms of the models' large-scale circulation field. This study shows, however, that in addition to the simulated large-scale circulation, three-dimensional age calculations can also be affected by the choice of advection scheme employed in solving the tracer continuity equation. Specifically, using the 3.0° latitude × 3.6° longitude and 40 vertical level version of the Geophysical Fluid Dynamics Laboratory SKYHI GCM and six online transport schemes ranging from Eulerian through semi-Lagrangian to fully Lagrangian, it will be demonstrated that the oldest ages are obtained using the nondiffusive centered-difference schemes while the youngest ages are computed with a semi-Lagrangian transport (SLT) scheme. The centered-difference schemes are capable of producing ages older than 10 years in the mesosphere, thus eliminating the 'young bias' found in previous age-of-air calculations. At this stage, only limited intuitive explanations can be advanced for this sensitivity of age-of-air calculations to the choice of advection scheme. In particular, age distributions computed online with the National Center for Atmospheric Research Community Climate Model (MACCM3) using different varieties of the SLT scheme are substantially older than the SKYHI SLT distribution. The different varieties, including a noninterpolating-in-the-vertical version (which is essentially centered-difference in the vertical), also produce a narrower range of age distributions than the suite of advection schemes employed in the SKYHI model. While additional MACCM3 experiments with a wider range of schemes would be necessary to provide more definitive insights, the older and less variable MACCM3 age distributions can plausibly be interpreted as being due to the semi-implicit semi-Lagrangian dynamics employed in the MACCM3. This type of dynamical core (employed with a 60-min time step) is likely to reduce SLT's interpolation errors that are compounded by the short-term variability characteristic of the explicit centered-difference dynamics employed in the SKYHI model (time step of 3 min)."
"56322979700;","Internal interannual variability of the extratropical stratospheric circulation: the low-latitude flywheel",1998,"10.1256/smsqj.55015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032428241&doi=10.1256%2fsmsqj.55015&partnerID=40&md5=19ac0c3164546a6f17eba055e19a861e","A new mechanism for internal interannual variability of the extratropical stratospheric circulation is described. The variability is internal in the sense that it arises in a stratosphere-only model without any interannual variability being imposed externally. In particular the wave forcing in the model, representing the effect of the tropospheric circulation, is kept constant from year-to-year and there is no imposed quasi-biennial variability in the equatorial winds. It is argued that the internal variability arises because of the longer 'memory' of the stratospheric flow at low latitudes. The smaller Coriolis parameter at low latitudes means that a given wind signal has associated with it a smaller temperature signal and is therefore less affected by radiative damping that a corresponding signal in the extratropics. The circulation at low latitudes can therefore act as a large flywheel, retaining memory of zonal mean quantities on an annual time-scale or longer. The mechanism for the variability is studied using a 'mechanistic' primitive-equation model of the stratosphere. Waves are forced by a constant wavenumber one perturbation to the geopotential height field at the lower boundary and a seasonal cycle is prescribed through Newtonian cooling towards a time-dependent temperature field. Interannual variability is found within a certain range of forcing amplitude. The variability typically takes the form of a biennial oscillation, but more complex behaviour is also found under some circumstances. Diagnostics suggest that zonal flow anomalies in the subtropics persisting from the end of one winter to the beginning of the next are responsible for the interannual variability. Further experiments, in which the zonal form at low altitudes is constrained in a particularly configuration, provide further evidence that the role of the subtropical flow is crucial since constraining the subtropical flow reduces or eliminates the forcing range for which interannual variability is obtained. The importance of the contrast between high latitudes and low latitudes for such internal modes of variability is consistent with their absence in stratospheric models such as the Holton-Mass model with a single degree of freedom for representing latitudinal structure. To illustrate the mechanism for the interannual variability further, an extended version of the Holton-Mass model is formulated that differentiates between high- and low-latitude regions. As in the case with full latitudinal resolution, interannual variability is obtained when the amplitude of the wave forcing lies within a certain range."
"7003991093;","Potential vorticity inversion and balanced equations of motion for rotating and stratified flows",1996,"10.1256/smsqj.52911","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029656718&doi=10.1256%2fsmsqj.52911&partnerID=40&md5=d4d15e0c4c0caf135f66914cfeb567e2","Balanced equations of motion based on potential vorticity evolution and inversion for the shallow water and stratified primitive equations are derived and, in some shallow-water cases, numerically tested. The schemes are based on asymptotic expansions in Rossby or Froude number, or rational scaling-based truncations of the equations of motion, assuming that the dynamics are determined by the advection of potential vorticity. Thus, regimes of validity are rapidly rotating and/or highly stratified flow. Both new and familiar results are straightforwardly obtained, in a unified framework in both height and isentropic coordinates. For both shallow-water and stratified equations, Rossby number expansions schemes give quasi-geostrophy at lowest order. Both gradient-wind balance and the nonlinear terms in the potential vorticity enter at next order. A low Froude number expansion for non-rotating flow gives two-dimensional flow, uncoupled in the vertical at lowest order. A single consistent inversion scheme can be derived that is valid at lowest order in Froude number for all Rossby numbers, for both shallow-water and the stratified equations. It may be a particularly appropriate model for the atmospheric mesoscale and oceanic submesoscale, where rotation and stratification can both be important in defining balanced motion. A model is also proposed that is valid at both planetary and synoptic scales, combining the familiar planetary geostrophic and quasi-geostrophic equations. Most of the models derived require the solution only of linear or near linear elliptic equations, possibly with varying coefficients. Numerical experiments indicate that a higher-order inversion can be quantitatively better than quasi-geostrophy, if Rossby number and divergence are sufficiently small. In some other cases, no noticeable improvement over quasi-geostrophy is found, even when the Rossby number is quite small. However, the balanced model valid for both planetary and synoptic scales shows a significant qualitative and quantitative improvement over both planetary geostrophy and quasi-geostrophy for large-scale flows, and its evolution is in good agreement with a primitive equation model."
"36992744000;15765007300;","Idealized tropical cyclone simulations of intermediate complexity: A test case for AGCMs",2012,"10.1029/2011MS000099","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867703870&doi=10.1029%2f2011MS000099&partnerID=40&md5=9a0b0bee162221f139650f3c2bb9636a","The paper introduces a moist, deterministic test case of intermediate complexity for Atmospheric General Circulation Models (AGCMs). We suggest pairing an AGCM dynamical core with simple physical parameterizations to test the evolution of a single, idealized, initially weak vortex into a tropical cyclone. The initial conditions are based on an initial vortex seed that is in gradient-wind and hydrostatic balance. The suggested ""simple-physics"" package consists of parameterizations of bulk aerodynamic surface fluxes for moisture, sensible heat and momentum, boundary layer diffusion, and large-scale condensation. Such a configuration includes the important driving mechanisms for tropical cyclones, and leads to a rapid intensification of the initial vortex over a forecast period of ten days. The simplephysics test paradigm is not limited to tropical cyclones, and can be universally applied to other flow fields. The physical parameterizations are described in detail to foster model intercomparisons. The characteristics of the intermediate-complexity test case are demonstrated with the help of four hydrostatic dynamical cores that are part of the Community Atmosphere Model version 5 (CAM 5) developed at the National Center for Atmospheric Research (NCAR). In particular, these are the Finite- Volume, Spectral Element, and spectral transform Eulerian and semi-Lagrangian dynamical cores that are coupled to the simple-physics suite. The simulations show that despite the simplicity of the physics forcings the models develop the tropical cyclone at horizontal grid spacings of about 55 km and finer. The simple-physics simulations reveal essential differences in the storm's structure and strength due to the choice of the dynamical core. Similar differences are also seen in complex full-physics aqua-planet experiments with CAM 5 which serve as a motivator for this work. The results suggest that differences in complex full-physics simulations can be, at least partly, replicated in simplified model setups. The simplified experiments might therefore provide easier access to an improved physical understanding of how the dynamical core and moist physical parameterizations interact. It is concluded that the simple-physics test case has the potential to close the gap between dry dynamical core assessments and full-physics aqua-planet experiments, and can shed light on the role of the dynamical core in the presence of moisture processes. Copyright © 2012 by the American Geophysical Union."
"6602387822;7004169486;6602494843;7003327598;","Seasonal variability of the Caspian Sea three-dimensional circulation, sea level and air-sea interaction",2010,"10.5194/os-6-311-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77749283218&doi=10.5194%2fos-6-311-2010&partnerID=40&md5=c58a76d609d30c857818ba470863e3a0","A three-dimensional primitive equation model including sea ice thermodynamics and air-sea interaction is used to study seasonal circulation and water mass variability in the Caspian Sea under the influence of realistic mass, momentum and heat fluxes. River discharges, precipitation, radiation and wind stress are seasonally specified in the model, based on available data sets. The evaporation rate, sensible and latent heat fluxes at the sea surface are computed interactively through an atmospheric boundary layer sub-model, using the ECMWF-ERA15 re-analysis atmospheric data and model generated sea surface temperature. The model successfully simulates sea-level changes and baroclinic circulation/mixing features with forcing specified for a selected year. The results suggest that the seasonal cycle of wind stress is crucial in producing basin circulation. Seasonal cycle of sea surface currents presents three types: cyclonic gyres in December-January; Eckman south-, south-westward drift in February-July embedded by western and eastern southward coastal currents and transition type in August-November. Western and eastern northward sub-surface coastal currents being a result of coastal local dynamics at the same time play an important role in meridional redistribution of water masses. An important part of the work is the simulation of sea surface topography, yielding verifiable results in terms of sea level. The model successfully reproduces sea level variability for four coastal points, where the observed data are available. Analyses of heat and water budgets confirm climatologic estimates of heat and moisture fluxes at the sea surface. Experiments performed with variations in external forcing suggest a sensitive response of the circulation and the water budget to atmospheric and river forcing."
"7003670680;6701704311;55700766400;16745193600;8946647600;7410021427;6603393679;6507941719;6603336161;7007039835;8636990400;7006026391;","Impact of terrestrial weather on the upper atmosphere",2008,"10.1029/2007GL032911","https://www.scopus.com/inward/record.uri?eid=2-s2.0-48549093860&doi=10.1029%2f2007GL032911&partnerID=40&md5=76fcc0dc0d402dd55fb842a0e9a57ab1","A whole atmosphere model has been developed to demonstrate the impact of terrestrial weather on the upper atmosphere. The dynamical core is based on the NWS Global Forecast System model, which has been extended to cover altitudes from the ground to 600 km. The model includes the physical processes responsible for the stochastic nature of the lower atmosphere, which is a source of variability for the upper atmosphere. The upper levels include diffusive separation, wind induced transport of major species, and uses specific enthalpy as the dependent variable, to accommodate composition dependent gas constants and specific heats. A one-year model simulation reveals planetary waves explicitly up to 100 km altitude. At higher altitude, multi-day periodicities in the dynamics appear as a modulation of tidal amplitudes, particularly the migrating semi-diurnal tide in the lower thermosphere dynamo region. The penetration of planetary wave periodicities from tropospheric weather into the upper atmosphere can explain terrestrial weather sources of variability in the thermospheric and ionospheric. Copyright 2008 by the American Geophysical Union."
"7102541338;7004360355;57203109046;7006575272;7202620125;","Variability of mesospheric diurnal tides and tropospheric diurnal heating during 1997-1998",2007,"10.1029/2007JD008578","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37349006117&doi=10.1029%2f2007JD008578&partnerID=40&md5=4ce58185ddff5243bfd84a77a7fe0345","This study focuses on interannual variations of diurnal tropospheric heating and the response in the mesosphere observed by radars and predicted by a model. The work is prompted by reports of interannual variability in amplitudes of tidal variables at low latitudes. Diurnal tides observed at Hawaii and Christmas Island exhibit a pronounced ""spike"" in amplitude from late 1997 to early 1998. It has been speculated that this variability may be linked to the El Niño-Southern Oscillation phenomenon. We examine diurnal solar heating due to water vapor absorption, and diurnal latent heat release due to deep convection between 1988 and 2005. Both of these heating drives exhibit anomalously higher amplitudes in the tropical central and eastern Pacific during 1997-1998. The altered heating patterns result in a stronger forcing of the migrating diurnal tide by water vapor heating, and excitation of several weaker nonmigrating modes by latent heating. A primitive equation model is used to evaluate how these drives contribute to diurnal winds in the mesosphere. Anomalous water vapor heating results in about 15% increases in model meridional wind amplitudes over climatological values at subtropical latitudes between 300°E and the Greenwich meridian. While the timing of the model amplitude enhancements is consistent with observations at Hawaii, the observed increases are significantly stronger. Our study indicates that water vapor heating is the larger contributor to tidal enhancement observed during 1997-1998. Copyright 2007 by the American Geophysical Union."
"7004060399;56322979700;57203508649;","Numerically converged solutions of the global primitive equations for testing the dynamical core of atmospheric GCMs",2004,"10.1175/MWR2788.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-8744240583&doi=10.1175%2fMWR2788.1&partnerID=40&md5=e63c50c435e2bd3af14f5fa79e969fbd","Solutions of the dry, adiabatic, primitive equations are computed, for the first time, to numerical convergence. These solutions consist of the short-time evolution of a slightly perturbed, baroclinically unstable, midlatitude jet, initially similar to the archetypal LC1 case of Thorncroft et al. The solutions are computed with two distinct numerical schemes to demonstrate that they are not dependent on the method used to obtain them. These solutions are used to propose a new test case for dynamical cores of atmospheric general circulation models. Instantaneous horizontal and vertical cross sections of vorticity and vertical velocity after 12 days, together with tables of key diagnostic quantities derived from the new solutions, are offered as reproducible benchmarks. Unlike the Held and Suarez benchmark, the partial differential equations and the initial conditions are here completely specified, and the new test case requires only 12 days of integration, involves no spatial or temporal averaging, and does not call for physical parameterizations to be added to the dynamical core itself. © 2004 American Meteorological Society."
"8152726300;6603585706;7003971889;","Vertical structure of convective heating and the three-dimensional structure of the forced circulation on an equatorial beta plane",2000,"10.1175/1520-0469(2000)057<2169:VSOCHA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034233723&doi=10.1175%2f1520-0469%282000%29057%3c2169%3aVSOCHA%3e2.0.CO%3b2&partnerID=40&md5=df67bf1c6c0bd863662571f7819916ed","In this paper, the three-dimensional structure of the thermally forced atmosphere on an equatorial β plane is investigated. Special emphasis is placed on the relations between the vertical structure of heating and the horizontal structure of the forced response. By solving the vertical eigenvalue-eigenfunction problem in a vertically semi-infinite domain, the authors obtain a complete set of vertical eigenfunctions that includes a single barotropic (external) mode and a continuous spectrum of baroclinic (internal) modes. These eigenfunctions are used to decompose vertical heating profiles for two types of tropical heating: 1) deep heating representing the convective plume (CP) heating and 2) shallow heating representing mature cloud (MC) cluster heating. By examining the spectral energy density of the heating profile, the contributions of each vertical mode (spectral interval) to the overall structure are explored for each case, and the difference between the responses to these two profiles of heating is discussed. A dry spectral primitive equation model of the atmosphere is employed to verify the analytical results. The results from both the analytical approach and the numerical simulations are consistent in showing that the vertical structure of the heating is fundamental to the structure of the forced response. The CP is deep relative to the MC. Thus, the CP projects onto the vertical eigenfunctions of relatively larger equivalent depth more so than does the MC. As a result, the CP-forced signals propagate away from the heat source much faster than those forced by the MC. Hence, when the atmosphere is subjected to the same linear dampings (Rayleigh friction and Newtonian cooling), the spatial (mainly in the horizontal) decay rate of the CP-forced signals is significantly smaller than that of the MC-forced signals, and the CP-forced signals extend farther. To what extent a shallow-water system of a specified vertical mode (e.g., the Gill model) can approximate the three-dimensional response is also examined. Results show that the effective gravity wave speed of the multimode system varies greatly with location. Hence, it is extremely difficult to select a globally suitable equivalent depth so that a one-mode shallow-water system can approximate the spatially three-dimensional structure of the response to a given heating.In this paper, the three-dimensional structure of the thermally forced atmosphere on an equatorial β plane is investigated. Special emphasis is placed on the relations between the vertical structure of heating and the horizontal structure of the forced response. By solving the vertical eigenvalue-eigenfunction problem in a vertically semi-infinite domain, the authors obtain a complete set of vertical eigenfunctions that includes a single barotropic (external) mode and a continuous spectrum of baroclinic (internal) modes. These eigenfunctions are used to decompose vertical heating profiles for two types of tropical heating: 1) deep heating representing the convective plume (CP) heating and 2) shallow heating representing mature cloud (MC) cluster heating. By examining the spectral energy density of the heating profile, the contributions of each vertical mode (spectral interval) to the overall structure are explored for each case, and the difference between the responses to these two profiles of heating is discussed. A dry spectral primitive equation model of the atmosphere is employed to verify the analytical results. The results from both the analytical approach and the numerical simulations are consistent in showing that the vertical structure of the heating is fundamental to the structure of the forced response. The CP is deep relative to the MC. Thus, the CP projects onto the vertical eigenfunctions of relatively larger equivalent depth more so than does the MC. As a result, the CP-forced signals propagate away from the heat source much faster than those forced by the MC. Hence, when the atmosphere is subjected to the same linear dampings (Rayleigh friction and Newtonain cooling), the spatial (mainly in the horizontal) decay rate of the CP-forced signals is significantly smaller than that of the MC-forced signals, and the CP-forced signals extend farther. To what extent a shallow-water system of a specified vertical mode (e.g., the Gill model) can approximate the three-dimensional response is also examined. Results show that the effective gravity wave speed of the multimode system varies greatly with location. Hence, it is extremely difficult to select a globally suitable equivalent depth so that a one-mode shallow-water system can approximate the spatially three-dimensional structure of the response to a given heating."
"7201654861;7402872647;","Numerical simulation of the development of mean monsoon circulation in July.",1983,"10.1175/1520-0493(1982)110<1879:nsotdo>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020947405&doi=10.1175%2f1520-0493%281982%29110%3c1879%3ansotdo%3e2.0.co%3b2&partnerID=40&md5=78c7a73953d5718775b1ef1dfeb2810a","Eight different experiments have been performed, ranging from 8 to 20 days, with a primitive equation model consisting of five atmospheric layers and one oceanic layer to investigate the relative importance of radiative heating and deep cumulus condensation, orography and initial conditions for the development of the mean monsoon circulation from June to July in the 0-180oE, 25oS-55oN region. The mean sea level pressure distribution and low-level flow pattern produced by these simulations are found to be mainly determined by the diabatic heating distribution and influenced somewhat by orography, but are almost independent of the initial state. -from Authors"
"36179077700;15765007300;7406243250;","Using variable-resolution meshes to model tropical cyclones in the community atmosphere model",2014,"10.1175/MWR-D-13-00179.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896756109&doi=10.1175%2fMWR-D-13-00179.1&partnerID=40&md5=37b26950f5ff9ba322935a9f6040ad53","A statically nested, variable-mesh option has recently been introduced into the Community Atmosphere Model's (CAM's) Spectral Element (SE) dynamical core that has become the default in CAM version 5.3. This paper presents a series of tests of increasing complexity that highlight the use of variable-resolution grids in CAM-SE to improve tropical cyclone representation by dynamically resolving storms without requiring the computational demand of a global high-resolution grid. As a simplified initial test, a dry vortex is advected through grid transition regions in variable-resolution meshes on an irrotational planet with the CAM subgrid parameterization package turned off. Vortex structure and intensity is only affected by grid resolution and no spurious artifacts are observed. CAM-SE model simulations using an idealized tropical cyclone test case on an aquaplanet show no numerical distortion or wave reflection when the cyclone interacts with an abrupt transition region. Using the same test case, the authors demonstrate that a regionally refined mesh with significantly fewer degrees of freedom can produce the same local results as a globally uniform grid. Additionally, the authors discuss a more complex aquaplanet experiment with meridionally varying sea surface temperatures that reproduces a quasi-realistic global climate. Tropical cyclogenesis is facilitated without the need for vortex bogusing in a high-resolution patch embedded within a global grid that is otherwise too coarse to resolve realistic tropical cyclones in CAM. © 2014 American Meteorological Society."
"15044268700;13406399300;7402725328;7102696626;7406243250;6701357023;","AMIP simulation with the CAM4 spectral element dynamical core",2013,"10.1175/JCLI-D-11-00448.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874816692&doi=10.1175%2fJCLI-D-11-00448.1&partnerID=40&md5=f89c09f268bcdb2dd51e2931a86b0bc1","The authors evaluate the climate produced by the Community Climate SystemModel, version 4, runningwith the new spectral element atmospheric dynamical core option. The spectral element method is configured to use a cubed-sphere grid, providing quasi-uniform resolution over the sphere and increased parallel scalability and removing the need for polar filters. It uses a fourth-order accurate spatial discretization that locally conserves mass and total energy. Using the Atmosphere Model Intercomparison Project protocol, the results from the spectral element dynamical core are compared with those produced by the default finite-volume dynamical core and with observations. Even though the two dynamical cores are quite different, their simulated climates are remarkably similar. When compared with observations, both models have strengths and weaknesses but have nearly identical root-mean-square errors and the largest biases show little sensitivity to the dynamical core. The spectral element core does an excellent job reproducing the atmospheric kinetic energy spectra, including fully capturing the observed Nastrom-Gage transition when running at 0.125° resolution. © 2013 American Meteorological Society."
"8725564400;7004060399;56322979700;25647168900;","Stratospheric influence on baroclinic lifecylces and its connection to the Arctic Oscillation",2004,"10.1029/2004GL020503","https://www.scopus.com/inward/record.uri?eid=2-s2.0-7044260954&doi=10.1029%2f2004GL020503&partnerID=40&md5=d78a5ca05db04a07b0f7988e44e785b1","Using an idealized primitive equation model, we investigate how stratospheric conditions alter the development of baroclinic instability in the troposphere. Starting from the lifecycle paradigm of Thorncroft et al., we consider the evolution of baroclinic lifecycles resulting from the addition of a stratospheric jet to the LCI initial condition. We find that the addition of the stratospheric jet yields a net surface geopotential height anomaly that strongly resembles the Arctic Oscillation. With the additional modification of the tropospheric winds to resemble the high-AO climatology, the surface response is amplified by a factor 10 and, though dominated by the tropospheric changes, shows similar sensitivity to the stratospheric conditions. Copyright 2004 by the American Geophysical Union."
"6602080118;7003354633;","Abrupt cooling of the mediterranean levantine intermediate water at the beginning of the 1980s: Observational evidence and model simulations",2001,"10.1175/1520-0485(2001)031<2307:acotml>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035415534&doi=10.1175%2f1520-0485%282001%29031%3c2307%3aacotml%3e2.0.co%3b2&partnerID=40&md5=770b3fb74f37c541992807ad22abef80","The Levantine Intermediate Water (LIW) is an important water mass for the overall hydrology of the Mediterranean Sea and there are open questions connected with the possible long-term variability of its physical characteristics. This paper is dedicated to the analysis and the interpretation of the LIW long-term variations over the last 50 years. It is based on data analysis and model simulations. On the one hand, new temperature and salinity gridded data of interannual and decadal anomalies have been produced from existing historical datasets. On the other hand, a long-term primitive equation model simulation has been generated, to be compared to the observational reconstructions. Results indicate that the major feature of both datasets (observations and model) is an intense cooling of the LIW (0.24°-0.28°C at 200-m depth) at the beginning of the 1980s (winters 1981 and 1983). Around the Aegean Sea and the Cretan Arc, the amplitude of the cooling is as large as 0.4°C. The model simulations, forced by the Comprehensive Ocean-Atmosphere Data Set atmospheric fluxes, reproduce the cooling event quite faithfully. The possible processes at the origin of these interannual/decadal variations are discussed. Hypotheses are proposed and tested against observations. In particular it is shown that over the period of interest, the major part of the LIW interannual/decadal variability has been directly forced by anomalies in the surface heat budget of the Eastern Mediterranean."
"7102201685;7003496841;","Scaling and computation of smooth atmospheric motions.",1986,"10.3402/tellusa.v38i4.11720","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022841262&doi=10.3402%2ftellusa.v38i4.11720&partnerID=40&md5=1575414a0581d22583d9ad68ac14b8ef","We introduce a general scaling of the inviscid Eulerian equations which is satisfied by all members of the set of adiabatic smooth stratified atmospheric motions. Then we categorize the members into mutually exclusive subsets. Be applying the bounded derivative principle to each of the subsets, we determine the specific scaling satisfied by that subset. One subset is midlatitude motion which is hydrostatic and has equal horizontal length scales. Traditionally, the primitive equations have been used to describe these motions. However it is well known that the use of the primitive equations for a limited area forecast of these motions leads to an ill-posed initial-boundary value problem. We introduce an alternate system which accurately describes this type of motion and can be used to form a well-posed initial-boundary value problem. We prove that the new system can also be used for any adiabatic or diabatic smooth stratified flow. Finally, we present supporting numerical results.-Authors"
"6506328135;7202048112;57188966058;55476830600;57111001300;","Resolution and dynamical core dependence of atmospheric river frequency in global model simulations",2015,"10.1175/JCLI-D-14-00567.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939286117&doi=10.1175%2fJCLI-D-14-00567.1&partnerID=40&md5=7991971598d4ab9da6ef6be0da3364a6","This study examines the sensitivity of atmospheric river (AR) frequency simulated by a global model with different grid resolutions and dynamical cores. Analysis is performed on aquaplanet simulations using version 4 of the Community Atmosphere Model (CAM4) at 240-, 120-, 60-, and 30-km model resolutions, each with the Model for Prediction Across Scales (MPAS) and High-Order Methods Modeling Environment (HOMME) dynamical cores. The frequency of AR events decreases with model resolution and the HOMME dynamical core produces more AR events than MPAS. Comparing the frequencies determined using absolute and percentile thresholds of large-scale conditions used to define an AR, model sensitivity is found to be related to the overall sensitivity of subtropical westerlies, atmospheric precipitable water content and profile, and to a lesser extent extratropical Rossby wave activity to model resolution and dynamical core. Real-world simulations using MPAS at 120- and 30-km grid resolutions also exhibit a decrease of AR frequency with increasing resolution over the southern east Pacific, but the difference is smaller over the northern east Pacific. This interhemispheric difference is related to the enhancement of convection in the tropics with increased resolution. This anomalous convection sets off Rossby wave patterns that weaken the subtropical westerlies over the southern east Pacific but has relatively little effect on those over the northern east Pacific. In comparison to the NCEP-2 reanalysis, MPAS real-world simulations are found to underestimate AR frequencies at both resolutions likely because of their climatologically drier subtropics and poleward-shifted jets. This study highlights the important links between model climatology of large-scale conditions and extremes. © 2015 American Meteorological Society."
"55853569200;6603239704;7003531755;7201498373;6508003688;","Megadroughts in southwestern North America in ECHO-G millennial simulations and their comparison to proxy drought reconstructions",2013,"10.1175/JCLI-D-12-00603.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884928015&doi=10.1175%2fJCLI-D-12-00603.1&partnerID=40&md5=25a3fa9151250d90cc5477794b8ae98a","Simulated hydroclimate variability in millennium-length forced transient and control simulations from the ECHAM and the global Hamburg Ocean Primitive Equation (ECHO-G) coupled atmosphere-ocean general circulation model (AOGCM) is analyzed and compared to 1000 years of reconstructed Palmer drought severity index (PDSI) variability from the North American Drought Atlas (NADA). The ability of the model to simulate megadroughts in the North American southwest is evaluated. (NASW: 25°-42.57°N, 125°-105°W). Megadroughts in the ECHO-G AOGCM are found to be similar in duration and magnitude to those estimated from the NADA. The droughts in the forced simulation are not, however, temporally synchronous with those in the paleoclimate record, nor are there significant differences between the drought features simulated in the forced and control runs. These results indicate that model-simulated megadroughts can result frominternal variability of the modeled climate systemrather than as a response to changes in exogenous forcings. Although the ECHO-G AOGCM is capable of simulating megadroughts through persistent La Ni~na-like conditions in the tropical Pacific, other mechanisms can produce similarly extreme NASW moisture anomalies in the model. In particular, the lack of low-frequency coherence between NASW soil moisture and simulated modes of climate variability like the El Ni~no-Southern Oscillation, Pacific decadal oscillation, and Atlantic multidecadal oscillation during identified drought periods suggests that stochastic atmospheric variability can contribute significantly to the occurrence of simulated megadroughts in the NASW. These findings indicate that either an expanded paradigm is needed to understand multidecadal hydroclimate variability in the NASW or AOGCMs may incorrectly simulate the strength and/or dynamics of the connection between NASW hydroclimate variability and the tropical Pacific."
"8255473900;7004279605;","A framework for testing global non-hydrostatic models",2009,"10.1002/qj.377","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649442690&doi=10.1002%2fqj.377&partnerID=40&md5=4a33e40509d9de413734d823491e2b2f","With the emergence of non-hydrostatic global dynamical cores, an alternative testing strategy is proposed, where the planetary radius is suitably reduced to capture non-hydrostatic phenomena without incurring the computational cost of actual simulations of weather and climate at non-hydrostatic resolution. The procedure is simple and tests various aspects of the discretized hydrostatic and non-hydrostatic equations in the same setting on a sphere. Furthermore, it facilitates verification against Cartesian-domain analytic solutions and against large-eddy simulation (LES) benchmarks available, for limited-area models. The proposed framework is illustrated with examples of inertia - gravity wave dynamics in linear and nonlinear regimes, including flows past idealized mountains, stratified shear flows and critical layers. Finally, an intercomparison of the Held-Suarez climate variability for reduced-size planets is presented, which provides a path for future investigations on the dynamics of convective boundary layers on a sphere. This assesses the ability to adequately capture interactions of large-scale dynamics with intermittent turbulent structures, an important aspect of future weather and climate predictions. Copyright © 2009 Royal Meteorological Society."
"36077992900;7005720566;7005874502;","Intraseasonal variability in a dry atmospheric model",2007,"10.1175/JAS3955.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34547730163&doi=10.1175%2fJAS3955.1&partnerID=40&md5=5a42eb23971ea4cebf5f1a9c438794af","A long integration of a primitive equation dry atmospheric model with time-independent forcing under boreal winter conditions is analyzed. A variety of techniques such as time filtering, space-time spectral analysis, and lag regressions are used to identify tropical waves. It is evident that oscillations with intraseasonal time scales and a Kelvin wave structure exist in the model tropical atmosphere. Coherent eastward propagations in the 250-hPa velocity potential and zonal wind are found, with a speed of about 15 m s-1. The oscillation is stronger in the Eastern Hemisphere than in the Western Hemisphere. Interactions between the tropical and extratropical flows are found to be responsible for the simulated intraseasonal variability. Wave activity flux analysis reveals that a tropical influence occurs in the North Pacific region where a northeastward wave activity flux is found associated with the tropical divergent flow in the western and central Pacific. In the North Atlantic sector, on the other hand, a strong extratropical influence is observed with a southward wave activity flux into the Tropics. The extratropical low-frequency variability develops by extracting kinetic energy from the basic mean flow and through interactions with synoptic-scale transient eddies. Linear experiments show that the tropical atmospheric response to the extratropical forcing in the North Atlantic leads to an eastward-propagating wave in the tropical easterly mean flow of the Eastern Hemisphere. © 2007 American Meteorological Society."
"7102185013;55665411300;7201568549;7003876983;57213561342;","A simple-physics global circulation model for Venus: Sensitivity assessments of atmospheric superrotation",2007,"10.1029/2006GL028567","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249877917&doi=10.1029%2f2006GL028567&partnerID=40&md5=7b80c22c069a9727e43bc57e56c6e961","A 3D global circulation model is adapted to the atmosphere of Venus to explore the nature of the planet's atmospheric superrotation. The model employs the full meteorological primitive equations and simplified forms for diabatic and other nonconservative forcings. It is therefore economical for performing very long simulations. To assess circulation equilibration and the occurrence of atmospheric superrotation, the climate model is run for 10,000-20,000 day integrations at 4° × 5° latitude-longitude horizontal resolution, and 56 vertical levels (denoted L56). The sensitivity of these simulations to imposed Venus-like diabatic heating rates, momentum dissipation rates, and various other key parameters (e.g., near-surface momentum drag), in addition to model configuration (e.g., low versus high vertical domain and number of atmospheric levels), is examined. We find equatorial superrotation in several of our numerical experiments, but the magnitude of superrotation is often less than observed. Further, the meridional structure of the mean zonal overturning (i.e., Hadley circulation) can consist of numerous cells which are symmetric about the equator and whose depth scale appears sensitive to the number of vertical layers imposed in the model atmosphere. We find that when realistic diabatic heating is imposed in the lowest several scales heights, only extremely weak atmospheric superrotation results. Copyright 2007 by the American Geophysical Union."
"7006705919;14013545600;6603711967;7402435469;57208455668;7003684963;57213743966;","Characteristics of atmospheric transport using three numerical formulations for atmospheric dynamics in a single GCM framework",2006,"10.1175/JCLI3763.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745075251&doi=10.1175%2fJCLI3763.1&partnerID=40&md5=85b1fa0ff4d2a73c7272a3620bec9512","This study examines the sensitivity of a number of important archetypical tracer problems to the numerical method used to solve the equations of tracer transport and atmospheric dynamics. The tracers' scenarios were constructed to exercise the model for a variety of problems relevant to understanding and modeling the physical, dynamical, and chemical aspects of the climate system. The use of spectral, semi-Lagrangian, and finite volume (FV) numerical methods for the equations is explored. All subgrid-scale physical parameterizations were the same in all model simulations. The model behavior with a few short simulations with passive tracers is explored, and with much longer simulations of radon, SF6, ozone, a tracer designed to mimic some aspects of a biospheric source/sink of CO2, and a suite of tracers designed around the conservation laws for thermodynamics and mass in the model. Large differences were seen near the tropopause in the model, where the FV core shows a much reduced level of vertical and meridional mixing. There was also evidence that the subtropical subsidence regions are more isolated from Tropics and midlatitudes in the FV core than seen in the other model simulations. There are also big differences in the stratosphere, particularly for age of air in the stratosphere and ozone. A comparison with estimated age of air from CO2 and SF6 measurements in the stratosphere suggest that the FV core is behaving most realistically. A neutral biosphere (NB) test case is used to explore issues of diurnal and seasonal rectification of a tracer with sources and sinks at the surface. The sources and sinks have a zero annual average, and the rectification is associated with temporal correlations between the sources and sinks, and transport. The test suggests that the rectification is strongly influenced by the resolved-scale dynamics (i.e., the dynamical core) and that the numerical formulation for dynamics and transport still plays a critical role in the distribution of NB-like species. Since the distribution of species driven by these processes have a strong influence on the interpretation of the ""missing sink"" for CO2 and the interpretation of climate change associated with anthropogenic forcing herein, these issues should not be neglected. The spectral core showed the largest departures from the predicted nonlinear relationship required by the equations for thermodynamics and mass conservations. The FV and semi-Lagrangian dynamics (SLD) models both produced errors a factor of 2 lower. The SLD model shows a small but systematic bias in its ability to maintain this relationship that was not present in the FV simulation. The results of the study indicate that for virtually all of these problems, the model numerics still have a large role in influencing the model solutions. It was frequently the case that the differences in solutions resulting from varying the numerics still exceed the differences in the simulations resulting from significant physical perturbations (like changes in greenhouse gas forcing). This does not mean that the response of the system to physical changes is not correct. When results are consistent using different numerical formulations for dynamics and transport it lends confidence to one's conclusions, but it does indicate that some caution is required in interpreting the results. The results from this study favor use of the FV core for tracer transport and model dynamics. The FV core is, unlike the others, conservative, less diffusive (e.g., maintains strong gradients better), and maintains the nonlinear relationships among variables required by thermodynamic and mass conservation constraints more accurately. © 2006 American Meteorological Society."
"55939078000;6602085180;7004098470;","A new solar radiation penetration scheme for use in ocean mixed layer studies: An application to the Black Sea using a fine-resolution Hybrid Coordinate Ocean Model (HYCOM)",2005,"10.1175/JPO2677.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14644388508&doi=10.1175%2fJPO2677.1&partnerID=40&md5=20047bc2700b7e99e6200843028e21be","A 1/25° × 1/25° cos(lat) (longitude × latitude) (≈3.2-km resolution) eddy-resolving Hybrid Coordinate Ocean Model (HYCOM) is introduced for the Black Sea and used to examine the effects of ocean turbidity on upper-ocean circulation features including sea surface height and mixed layer depth (MLD) on annual mean climatological time scales. The model is a primitive equation model with a K-profile parameterization (KPP) mixed layer submodel. It uses a hybrid vertical coordinate that combines the advantages of isopycnal, σ, and z-level coordinates in optimally simulating coastal and open-ocean circulation features. This model approach is applied to the Black Sea for the first time. HYCOM uses a newly developed time-varying solar penetration scheme that treats attenuation as a continuous quantity. This scheme includes two bands of solar radiation penetration, one that is needed in the top 10 m of the water column and another that penetrates to greater depths depending on the turbidity. Thus, it is suitable for any ocean general circulation model that has fine vertical resolution near the surface. With this scheme, the optical depth-dependent attenuation of subsurface heating in HYCOM is given by monthly mean fields for the attenuation of photosynthetically active radiation (kPAR) during 1997-2001. These satellite-based climatological kPAR fields are derived from Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) data for the spectral diffuse attenuation coefficient at 490 nm (k490) and have been processed to have the smoothly varying and continuous coverage necessary for use in the Black Sea model applications. HYCOM simulations are driven by two sets of high-frequency climatological forcing, but no assimilation of ocean data is then used to demonstrate the importance of including spatial and temporal varying attenuation depths for the annual mean prediction of upper-ocean quantities in the Black Sea, which is very turbid (kPAR &gt; 0.15 m-1, in general). Results are reported from three model simulations driven by each atmospheric forcing set using different values for the kPAR. A constant solar-attenuation optical depth of ≈17 m (clear water assumption), as opposed to using spatially and temporally varying attenuation depths, changes the surface circulation, especially in the eastern Black Sea. Unrealistic sub-mixed layer heating in the former results in weaker stratification at the base of the mixed layer and a deeper MLD than observed. As a result, the deep MLD off Sinop (at around 42.5°N, 35.5°E) weakens the surface currents regardless of the atmospheric forcing used in the model simulations. Using the SeaWiFS-based monthly turbidity climatology gives a shallower MLD with much stronger stratification at the base and much better agreement with observations. Because of the high Black Sea turbidity, the simulation with all solar radiation absorbed at the surface case gives results similar to the simulations using turbidity from SeaWiFS in the annual means, the aspect of the results investigated in this paper."
"6603183022;7202945895;7005929337;","Cyclogenesis in the Denmark strait overflow plume",2001,"10.1175/1520-0485(2001)031<3214:CITDSO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035509474&doi=10.1175%2f1520-0485%282001%29031%3c3214%3aCITDSO%3e2.0.CO%3b2&partnerID=40&md5=7439bca8372951f172468dc4bea7587c","A densely spaced hydrographic survey of the northern Irminger Basin together with satellite-tracked near-surface drifters confirm the intense mesoscale variability within and above the Denmark Strait overflow. In particular, the drifters show distinct cyclonic vortices over the downslope edge of the outflow plume. Growing perturbations such as these can be attributed to the baroclinic instability of a density current. A primitive equation model with periodic boundaries is used to simulate the destabilization of an idealized dense filament on a continental slope that resembles the northeastern Irminger Basin. Unstable waves evolve rapidly if the initial temperature profile is perturbed with a sinusoidal anomaly that exceeds a certain cutoff wavelength. As the waves grow to large amplitudes isolated eddies of both signs develop. Anticyclones form initially within the dense filament and are rich in overflow water. In contrast, cyclones form initially with their center in the ambient water but wrap outflow water around their center, thus containing a mixture of both water types. The nonlinear advection of waters that were originally located within the front between both water masses contributes most significantly to the stronger intensification of the cyclones in comparison with anticyclones. The frontal waters carry positive relative vorticity into the center of the cyclone. The process bears therefore some resemblance to atmospheric frontal cyclogenesis. After saturation there is a bottom jet of overflow water that is confined by counterrotating eddies: anticyclones upslope and cyclones downslope of the overflow core. The parameter dependence of the maximum growth rate is studied, and the implications of eddy-induced mixing for the water mass modification is discussed."
"55046667600;7102202012;","Time-dependent nonlinear Hadley circulation",1999,"10.1175/1520-0469(1999)056<1797:TDNHC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032716732&doi=10.1175%2f1520-0469%281999%29056%3c1797%3aTDNHC%3e2.0.CO%3b2&partnerID=40&md5=3b4bae9b158fe9240678b1240094cd91","The time-dependent Hadley circulation is studied numerically in a nonlinear, nearly inviscid, axially symmetric primitive equation model, with the heating varying periodically on an annual cycle. The annual average of the Hadley circulation strength in this model with time-dependent heating is about a factor of 2 stronger than the steady-state response to the annual mean heating and is closer to the observed strength in the real atmosphere. This is caused by the fact that heating centered off-equator tends to produce stronger meridional circulation in the winter hemisphere than in the case when the heating maximum is located at the equator, as pointed out previously by Lindzen and Hou. However, unlike the steady-state solutions, there is no abrupt change as the heating center is moved off the equator. The temperature response in this time-dependent model is simple to understand. In the tropical region, where there is a variable, but persistent, Hadley circulation, the temperature is homogenized latitudinally. In the high-latitude region, where there is no meridional circulation (in the absence of the eddies), the temperature response goes through an annual cycle with a phase lag relative to the phase of the heating. This response is as predicted by the simple time-dependent temperature equation in the absence of meridional circulation.The time-dependent Hadley circulation is studied numerically in a nonlinear, nearly inviscid, axially symmetric primitive equation model, with the heating varying periodically on an annual cycle. The annual average of the Hadley circulation strength in this model with time-dependent heating is about a factor of 2 stronger than the steady-state response to the annual mean heating and is closer to the observed strength in the real atmosphere. This is caused by the fact that heating centered off-equator tends to produce stronger meridional circulation in the winter hemisphere than in the case when the heating maximum is located at the equator, as pointed out previously by Lindzen and Hou. However, unlike the steady-state solutions, there is no abrupt change as the heating center is moved off the equator. The temperature response in this time-dependent model is simple to understand. In the tropical region, where there is a variable, but persistent, Hadley circulation, the temperature is homogenized latitudinally. In the high-latitude region, where there is no meridional circulation (in the absence of the eddies), the temperature response goes through an annual cycle with a phase lag relative to the phase of the heating. This response is as predicted by the simple time-dependent temperature equation in the absence of meridional circulation."
"7006629146;7103294731;","The importance of surface pressure changes in the response of the atmosphere to zonally‐symmetric thermal and mechanical forcing",1989,"10.1002/qj.49711549002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024874481&doi=10.1002%2fqj.49711549002&partnerID=40&md5=31d9d9c2bee9ffc94ea3d3a218348690","The classical problem of the response of a balanced, axisymmetric vortex to thermal and mechanical forcing is re‐examined, paying special attention to the lower boundary condition. The correct condition is DΦ/Dt = 0, where Φ is the geopotential and D/Dt the material derivative, which explicitly accounts for a mass redistribution as part of the mean‐flow response. This redistribution is neglected when using the boundary condition Dp/Dt = 0, which has conventionally been applied in this problem. It is shown that applying the incorrect boundary condition, and thereby ignoring the surface pressure change, leads to a zonal wind acceleration δū/δt that is too strong, especially near the surface. The effect is significant for planetary‐scale forcing even when applied at tropopause level. A comparison is made between the mean‐flow evolution in a baroclinic life‐cycle, as simulated in a fully nonlinear, primitive‐equation model, and that predicted by using the simulated eddy fluxes in the zonally‐symmetric response problem. Use of the correct lower boundary condition is shown to lead to improved agreement. Copyright © 1989 Royal Meteorological Society"
"16025531300;56550089500;56219282100;6603718837;6507815511;6602972127;6507791659;36601773500;36623022500;","Assessing 20th century climate-vegetation feedbacks of land-use change and natural vegetation dynamics in a fully coupled vegetation-climate model",2010,"10.1002/joc.2132","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958545011&doi=10.1002%2fjoc.2132&partnerID=40&md5=0df9c5b84c08d718214d391c5692d6d0","This study describes the coupling of the dynamic global vegetation model (DGVM), Lund-Potsdam-Jena Model for managed land (LPJmL), with the general circulation model (GCM), Simplified Parameterizations primitivE Equation DYnamics model (SPEEDY), to study the feedbacks between land-use change and natural vegetation dynamics and climate during the 20th century. We show that anthropogenic land-use change had a stronger effect on climate than the natural vegetation's response to climate change (e.g. boreal greening). Changes in surface albedo are an important driver of the climate's response; but, especially in the (sub)tropics, changes in evapotranspiration and the corresponding changes in latent heat flux and cloud formation can be of equal importance in the opposite direction. Our study emphasizes that implementing dynamic vegetation into climate models is essential, especially at regional scales: the dynamic response of natural vegetation significantly alters the climate change that is driven by increased atmospheric greenhouse gas concentrations and anthropogenic land-use change. Copyright © 2010 Royal Meteorological Society."
"7003514003;7004696243;","Zonal flow vacillation and bimodality of baroclinic eddy life cycles in a simple global circulation model",1997,"10.1175/1520-0469(1997)054<2349:ZFVABO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031251724&doi=10.1175%2f1520-0469%281997%29054%3c2349%3aZFVABO%3e2.0.CO%3b2&partnerID=40&md5=a45b372546f24961413dce5075b8aa1c","A global primitive-equation model of the atmosphere is used to study the relationship between the temporal variations of the zonal mean zonal flow and baroclinic eddies. Nonperiodic low-frequency vacillation of the mean zonal flow is found in longtime integrations of the model under a perpetual condition; the zonal-mean jet in the extratropics changes its position nearly barotropically. A potential vorticity-potential temperature (PV-θ) analysis is performed for two extreme periods of the zonal flow vacillation. Anticyclonic breakings of upper troughs are dominant in the period of a high-latitude jet, while cyclonic breakings are dominant in the period of a low-latitude jet. A statistically significant relationship between the zonal flow vacillation and the morphology of life cycles of baroclinic eddies is obtained for the entire period analyzed. An index of the life cycles, which is introduced in this study, shows clear bimodality in its frequency distribution function. The relationship is also confirmed by two experimental runs with a different intensity of the surface drag. For the low-drag run, the zonal-mean jet is located in high latitudes through the integration period and life cycles of baroclinic eddies are basically characterized by the anticyclonic breaking. For the high-drag run, on the other hand, the zonal-mean jet is located in low latitudes and life cycles of baroclinic eddies are characterized by the cyclonic breaking. Although these two types of breaking pattern are similar to the two paradigms of baroclinic wave life cycles obtained in some idealized one-shot experiments, there are some differences from the one-shot experiments in the deformation field on an isentropic surface and in the relative location between the zonal-mean jet and the latitude of maximum eddy kinetic energy."
"7003440089;","Air-sea interactions over Terra Nova Bay during winter: Simulation with a coupled atmosphere-polynya model",1997,"10.1029/96JD03098","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031417714&doi=10.1029%2f96JD03098&partnerID=40&md5=650457fb72b034ebf4ae6f402272d13a","A preliminary simulation of the Terra Nova Bay polynya has been performed with a coupled atmosphere-polynya model. The atmospheric model is a hydrostatic primitive equations model that has been validated previously by a simulation of the strong katabatic winds observed in that area. The polynya model includes a representation of the free drift of frazil ice and simple sea-ice dynamics and thermodynamics. Two and three-dimensional experiments have been performed under polar night conditions. Two-dimensional experiments show that an open (warm) water area influences significantly the atmospheric circulation in the antarctic coastal zone: an additional ice-breeze effect is simulated and is responsible for the strenghthening of the katabatic winds near the coast. Because of the important temperature difference between the continental air and the ice-free ocean (up to 40°C), strong surface heat fluxes are simulated over the polynya. Finally, a three-dimensional experiment has been performed. The integration domain includes Terra Nova Bay. The polynya observed in that region is well simulated. It is found that heat losses from the polynya surface are stronger than previously thought but are probably constrained by the idealized representation of frazil ice, which is assumed to be uniform in each grid box. This stresses the need for having a better knowledge of frazil ice evolution in large polynyas. Copyright 1997 by the American Geophysical Union."
"35566896300;","Optimal perturbation time evolution and sensitivity of ensemble prediction to perturbation amplitude",1995,"10.1002/qj.49712152710","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029520273&doi=10.1002%2fqj.49712152710&partnerID=40&md5=838dc75ca2f72ae82e07f3d8daf5f675","Certain characteristics of the perturbations which grow most rapidly over a finite time interval in a primitiveequation atmospheric model are discussed. They are the singular vectors of a linear approximation of the European Centre for Medium‐Range Weather Forecasts primitive‐equation model. They are computed using the adjoint technique at horizontal spectral truncation T21 with 19 vertical levels. Linear combinations of singular vectors, named optimal perturbations, can be used in ensemble prediction to generate the initial conditions of perturbed integrations. Firstly, having specified the initial amplitude to be comparable with the amplitude of analysis‐error estimates, the nonlinear time evolution of optimal perturbations when added to the control initial conditions are studied. In particular, estimates are made of the time limit, TNL, after which nonlinear processes cannot be neglected. Considering optimal perturbations generated using singular vectors with maximum growth over a 36‐hour time interval, and characterized by amplitudes comparable with analysis‐error estimates, two different methods estimate TNL ≈ 2‐2.5 days. Secondly, the sensitivity of ensemble predictions to the optimal perturbation amplitude is analysed. This sensitivity study suggests that an increase of the root‐mean‐square amplitude of the initial perturbation can give a more realistic ensemble spread. Lastly, an estimate of the possible impact of the reduction of the amplitude of analysis errors on the skill of numerical weather prediction is deduced from the comparison of ensemble experiments run with T21 initial perturbations characterized by different amplitudes. Results indicate that a reduction of the root‐mean‐square amplitude of the analysis error by a factor √2 may lead to an improvement of medium‐range predictability up to 1 day, and that a reduction by a factor 2√2 may reduce the errors of the 7‐day forecast to values shown, at present, at forecast‐day 5. Copyright © 1995 Royal Meteorological Society"
"7004960372;","Normal mode initialization",1981,"10.1029/RG019i003p00450","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019727253&doi=10.1029%2fRG019i003p00450&partnerID=40&md5=e16ff2c02e401fecb0731006c2c43017","The baroclinic primitive equation models used for short‐ and medium‐range weather forecasting admit undesirable high‐frequency gravity waves. The gravity waves are excited by initial imbalances between the observed wind and mass fields and by inconsistencies between model and atmosphere. Over the years, many initialization techniques have been devised to balance the initial state, but without notable success. The recent introduction of normal mode initialization techniques has, to a large degree, solved the problem. The present review will discuss the development of the technique from first principles, introduce the slow manifold concept, and discuss successful applications and remaining problems. Copyright © 1981 by the American Geophysical Union."
"36127611800;7005439821;7006566972;7201360093;","Coastal trapped waves, alongshore pressure gradients, and the California undercurrent",2014,"10.1175/JPO-D-13-095.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892639246&doi=10.1175%2fJPO-D-13-095.1&partnerID=40&md5=31c25bf4d9c6842f570ca2af848a8113","The California Undercurrent (CUC), a poleward-flowing feature over the continental slope, is a key transport pathway along the west coast of North America and an important component of regional upwelling dynamics. This study examines the poleward undercurrent and alongshore pressure gradients in the northern California Current System (CCS), where local wind stress forcing is relatively weak. The dynamics of the undercurrent are compared in the primitive equation Navy Coastal Ocean Model and a linear coastal trapped wave model. Both models are validated using hydrographic data and current-meter observations in the core of the undercurrent in the northern CCS. In the linear model, variability in the predominantly equatorward wind stress along the U.S. West Coast produces episodic reversals to poleward flow over the northern CCS slope during summer. However, reproducing the persistence of the undercurrent during late summer requires additional incoming energy from sea level variability applied south of the region of the strongest wind forcing. The relative importance of the barotropic and baroclinic components of the modeled alongshore pressure gradient changes with latitude. In contrast to the southern and central portions of the CCS, the baroclinic component of the alongshore pressure gradient provides the primary poleward force at CUC depths over the northern CCS slope. At time scales from weeks to months, the alongshore pressure gradient force is primarily balanced by the Coriolis force associated with onshore flow. © 2014 American Meteorological Society."
"6602911746;56248292900;","Distribution and interannual variability of dense water production from coastal polynyas on the Chukchi Shelf",2002,"10.1029/2001jc000984","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037101720&doi=10.1029%2f2001jc000984&partnerID=40&md5=4d52abb884a3e2feb316acabdd8ee0c4","Dense water formation from coastal polynyas on the Chukchi Shelf is examined using a primitive-equation ocean model forced by surface bouyancy fluxes from a time-dependent polynya model for the winters of the 1978-1998 period. The model is forced by either meteorological observations or National Center for Environmental Prediction (NCEP) reanalysis data. During the 21-year period the surface forcing and the dense water production vary by a factor of 2. Using meteorological observations, most winters produce substantial amounts of water with a density anomaly of at least 1.2 kg m-3 (salinity increase of 1.5 psu), while using NCEP forcing, density anomalies typically reach 0.8 kg m-3 (1.0 psu) but are rarely as large as 1.2 kg m-3. With meteorological forcing, the production of dense water is fairly uniform throughout the entire period, whereas with NCEP forcing, nearly all of the water with density anomaly greater than 1.2 kg m-3 is formed during the early part of the modeled period (1978-1984), with the density anomaly rarely reaching 1 kg m-3 in the later part (1987 and onwards). Interannual variability is high with large differences between successive winters in both ice production and dense water production. Most of the observed variability can be explained by varying wind fields, with offshore winds creating polynyas between 30 and 75% of the time during November to April. Using a climatologically based mean initial salinity of 31.6 psu, we show that maximum salinities produced rarely exceed 33.5 psu. Furthermore, on the basis of moored observations in Bering Strait, we conclude that the interannual variability of the initial salinity is of the same magnitude as the interannual variability in dense water formation, and thus both are equally important in determining whether or not winter water is dense enough to contribute to the cold halocline layer of the Arctic Ocean. Winters with high fractions of offshore winds can produce anomalies up to 1.8 kg m-3 (2.2 psu). This, together with the varying initial salinity (density) fields, can achieve waters with maximum salinities up to 35.4 psu. Finally, we find that the derived ice volumes and dense water productions are highly sensitive to the forcing (meteorological vs. NCEP), and comparison with in situ observations is highly recommended."
"7201554561;7005874502;36077992900;","The extratropical signal generated by a midlatitude SST anomaly. Part I: Sensitivity at equilibrium",2001,"10.1175/1520-0442(2001)014<2035:TESGBA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035324985&doi=10.1175%2f1520-0442%282001%29014%3c2035%3aTESGBA%3e2.0.CO%3b2&partnerID=40&md5=276e5cd16657198b94f6ed90301b1737","A simple GCM (SGCM) is constructed by adding empirically derived time-independent forcing terms to a dry primitive equation model. This yields a model with realistic time-mean jets and storm tracks. The SGCM is then used to study the equilibrium response to an imposed heating anomaly in the midlatitude Pacific, meant to represent an anomaly in the sea surface temperature. Using the SGCM's own climatology as a basic state, the same model is then used to find the time-independent linear response to the same heating anomaly. The difference between the two responses is clearly attributed to the forcing due to anomalous transient eddies. The sensitivity of the response to the strength and vertical profile of the heating, and to the presence of the wind speed in the surface flux parameterization, is explored. It is found that for a reasonable range of heating amplitude the transient eddy forcing is proportional to the heating and the responses to heating and cooling are almost antisymmetric. The antisymmetry breaks down at large amplitude. The vertical profile of heating has a small but systematic effect on the response: deeper heating leads to stronger equivalent barotropic features. The inclusion of wind speed in the surface flux parameterization alters the response mainly by virtue of altering the basic model climatology, rather than by any local effect on the heating. The position of the heating anomaly is varied in both latitude and longitude to gain insight into the possible effects of systematic errors in GCMs. The time-independent linear response tends to move with the heating, but the eddy-driven nonlinear part remains relatively fixed and varies only in amplitude. The heating perturbation slightly modifies the first empirical orthogonal function of the model's internal low frequency variability. The response projects strongly onto this pattern and the probability distribution function of the projection is significantly skewed."
"13403627400;7003875148;55897144500;","Idealized simulations of atmospheric coastal flow along the central coast of California",1998,"10.1175/1520-0450(1998)037<1332:isoacf>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001766103&doi=10.1175%2f1520-0450%281998%29037%3c1332%3aisoacf%3e2.0.co%3b2&partnerID=40&md5=5f6ef4f1435aa86938a1eaa0ec802207","A fully nonlinear, primitive equation hydrostatic numerical model is utilized to study coastal flow along central California, combining a realistic atmospheric model, with a higher-order turbulence closure, with highly simplified background flow. Local terrain and surface forcing of the model are treated realistically, while the synoptic-scale forcing is constant in time and space. Several different simulations with different background wind directions were performed. The motivation is to isolate the main properties of the local flow dependent on the coastal mesoscale influence only and to facilitate a study of the structure of the coastal atmospheric boundary layer, the mean momentum budget, and the atmospheric forcing on the coastal ocean for simplified quasi-stationary but still typical conditions. The model results feature the expected summertime flow phenomena, even with this simplified forcing. A coastal jet occurs in all simulations, and its diurnal variability is realistically simulated. The coastal topography serves as a barrier, and the low-level coastal flow is essentially coast parallel. Among the conclusions are the following. (i) The boundary layer for a northerly jet is more shallow and more variable than that for a southerly jet. One reason is an interaction between waves generated by the coastal mountains and the boundary layer. A realistic inclusion of the Sierra Nevada is important, even for the near-surface coastal atmosphere. (ii) The transition from southerly to northerly flow, when changing the background flow direction, is abrupt for a change in the latter from west to northwest and more gradual for a change east to south. (iii) The low-level flow is in general semigeostrophic. The across-coast momentum balance is geostrophic, while the along-coast momentum balance is dominated by vertical stress divergence and the pressure gradient. Local acceleration and spatial variability close to the coast arise as a consequence of the balance among the remaining terms. For southeasterly background flow, the across-coast momentum balance is dominated by the background synoptic-scale and the mesoscale pressure gradients, sometimes canceling the forcing, thus making this case transitional. (iv) Smaller-scale flow transitions arise for some background flow directions, including an early morning jet reversal north of Monterey, California, and a morning-to-noon low-level eddy formation in the Southern Californian Bight. (v) The model turbulence parameterization provides realistic patterns of the atmospheric forcing on the coastal ocean. (vi) Characteristic signals measured in propagating wind reversals related to boundary layer depth and inversion structure here are seen to correspond to different quasi-stationary conditions."
"7102315560;7004010406;","Monsoon disturbances, intraseasonal oscillations, teleconnection patterns, blocking, and storm tracks of the global atmosphere during January 1979: linear theory",1993,"10.1175/1520-0469(1993)050<1349:MDIOTP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027797265&doi=10.1175%2f1520-0469%281993%29050%3c1349%3aMDIOTP%3e2.0.CO%3b2&partnerID=40&md5=bd7f31030b9bdeb9fc6c4447e591a966","The results of a study are presented that indicate that a wide variety of atmospheric disturbances, including those associated with storm tracks and blocking in both hemispheres, quasi-stationary global teleconnection patterns, and localized monsoon disturbances, as well as intraseasonal oscillations, may be generated through the instability of the three-dimensional global basic state for January 1979 including a wave-CISK cumulus heating parameterization. The analysis has been conducted with a two-level primitive equation eigenvalue model, and the growing disturbances for various specifications of the strengths of the cumulus heating have been analyzed. -from Authors"
"35739529800;56655654500;","Response of Northern Hemisphere midlatitude circulation to arctic amplification in a simple atmospheric general circulation model",2016,"10.1175/JCLI-D-15-0602.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962223541&doi=10.1175%2fJCLI-D-15-0602.1&partnerID=40&md5=31418c505b2edb1137662deb867796bf","This study examines the Northern Hemisphere midlatitude circulation response to Arctic amplification (AA) in a simple atmospheric general circulation model. It is found that, in response to AA, the tropospheric jet shifts equatorward and the stratospheric polar vortex weakens, robustly for various AA forcing strengths. Despite this, no statistically significant change in the frequency of sudden stratospheric warming events is identified. In addition, in order to quantitatively assess the role of stratosphere-troposphere coupling, the tropospheric pathway is isolated by nudging the stratospheric zonal mean state toward the reference state. When the nudging is applied, rendering the stratosphere inactive, the tropospheric jet still shifts equatorward but by approximately half the magnitude compared to that of an active stratosphere. The difference represents the stratospheric pathway and the downward influence of the stratosphere on the troposphere. This suggests that stratosphere-troposphere coupling plays a nonnegligible role in establishing the midlatitude circulation response to AA. © 2016 American Meteorological Society."
"6603718837;7102998314;7003467276;6507815511;6603590004;35894581100;","Dominant modes of variability in the South Atlantic: A study with a hierarchy of ocean-atmosphere models",2005,"10.1175/JCLI3370.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22944466051&doi=10.1175%2fJCLI3370.1&partnerID=40&md5=f0a98d205c8356596ae666164883e8ae","Using an atmosphere model of intermediate complexity and a hierarchy of ocean models, the dominant modes of interannual and decadal variability in the South Atlantic Ocean are studied. The atmosphere Simplified Parameterizations Primitive Equation Dynamics (SPEEDY) model has T30L7 resolution. The physical package consists of a set of simplified physical parameterization schemes, based on the same principles adopted in the schemes of state-of-the-art AGCMs. It is at least an order of magnitude faster, whereas the quality of the simulated climate compares well with those models. The hierarchy of ocean models consists of simple mixed layer models with an increasing number of physical processes involved such as Ekman transport, wind-induced mixing, and wind-driven barotropic transport. Finally, the atmosphere model is coupled to a regional version of the Miami Isopycnal Coordinate Ocean Model (MICOM) covering the South Atlantic with a horizontal resolution of 1° and 16 vertical layers. The coupled modes of mean sea level pressure and sea surface temperature simulated by SPEEDY-MICOM strongly resemble the modes as analyzed from the NCEP-NCAR reanalysis, indicating that this model configuration possesses the required physical mechanisms for generating these modes of variability. Using the ocean model hierarchy the authors were able to show that turbulent heat fluxes, Ekman transport, and wind-induced mixing contribute to the generation of the dominant modes of coupled SST variability. The different roles of these terms in generating these modes are analyzed. Variations in the wind-driven barotropic transport mainly seem to affect the SST variability in the Brazil-Malvinas confluence zone. The spectra of the mixed layer models appeared to be too red in comparison with the fully coupled SPEEDY-MICOM model due to the too strong coupling between SST and surface air temperatures (SATs), resulting from the inability to advect and subduct SST anomalies by the mixed layer models. In SPEEDY-MICOM anomalies in the southeastern corner of the South Atlantic are subducted and advected toward the north Brazilian coast on a time scale of about 6 yr. © 2005 American Meteorological Society."
"6603431141;6507948826;6603767711;6506197137;7004547261;","CIRA/CSU four-dimensional variational data assimilation system",2005,"10.1175/MWR2891.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-11844289219&doi=10.1175%2fMWR2891.1&partnerID=40&md5=d558b4d3e3804f58e4cfdcae70e535bd","A new four-dimensional variational data assimilation (4DVAR) system is developed at the Cooperative Institute for Research in the Atmosphere (CIRA)/Colorado State University (CSU). The system is also called the Regional Atmospheric Modeling Data Assimilation System (RAMDAS). In its present form, the 4DVAR system is employing the CSU/Regional Atmospheric Modeling System (RAMS) nonhydrostatic primitive equation model. The Weather Research and Forecasting (WRF) observation operator is used to access the observations, adopted from the WRF three-dimensional variational data assimilation (3DVAR) algorithm. In addition to the initial conditions adjustment, the RAMDAS includes the adjustment of model error (bias) and lateral boundary conditions through an augmented control variable definition. Also, the control variable is defined in terms of the velocity potential and streamfunction instead of the horizontal winds. The RAMDAS is developed after the National Centers for Environmental Prediction (NCEP) Eta 4DVAR system, however with added improvements addressing its use in a research environment. Preliminary results with RAMDAS are presented, focusing on the minimization performance and the impact of vertical correlations in error covariance modeling. A three-dimensional formulation of the background error correlation is introduced and evaluated. The Hessian preconditioning is revisited, and an alternate algebraic formulation is presented. The results indicate a robust minimization performance. © 2005 American Meteorological Society."
"35608102200;8204579300;7102338395;","Offshore propagation of eddy kinetic energy in the California Current",2001,"10.1029/2000jc000433","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034905531&doi=10.1029%2f2000jc000433&partnerID=40&md5=e0b9b3e764f3ae32145d6c88f35fd794","Low-pass-filtered velocities obtained from surface drifters and surface geostrophic velocities estimated from TOPEX/Poseidon altimeter data have recently revealed a clear and robust seasonal cycle in the surface eddy kinetic energy (EKE) in the California Current (CC) [Kelly et al., 1998; Strub and James, 2000]. The seasonal cycle begins in spring when a surface-intensified baroclinic equatorward jet develops next to the coast in response to strong upwelling favorable winds. This jet, and a developing eddy field, then moves offshore during summer and fall. The EKE maximum associated with the jet progresses only as far as 127°W, beyond which it decreases rapidly. This is a robust characteristic of the seasonal cycle that has been previously attributed only to an unspecified dissipation process. To investigate this aspect of the surface EKE, a multiyear simulation of the CC is carried out using the Dietrich/Center for Air-Sea Technology primitive equation regional ocean model [Dietrich, 1997]. The simulation accurately reproduces many aspects of the observed annual cycle, including the offshore propagation of the EKE at the surface. The model results indicate that the decrease of surface EKE west of 127°W in the simulation is not due to dissipation but rather is caused by the vertical redistribution of EKE to the deep ocean. This redistribution occurs through the transformation of kinetic energy from the vertical shear flow to the vertical mean flow. The transformation is a nonlinear process inherently associated with the life cycle of baroclinically unstable waves, and in the CC, it effectively energizes the deeper ocean at the expense of the upper ocean. The process is also known to be important in the atmosphere [Wiin-Nielsen, 1962]. Taken together, the recent California Current observations and the new model results strongly suggest that the CC regularly supplies EKE to the deep waters of the eastern North Pacific. Copyright 2001 by the American Geophysical Union."
"7004889197;55194361500;","Representation of eddies in primitive equation models by a PV flux",2000,"10.1175/1520-0485(2000)030<2481:ROEIPE>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033652444&doi=10.1175%2f1520-0485%282000%29030%3c2481%3aROEIPE%3e2.0.CO%3b2&partnerID=40&md5=6dbf735abe7c926994ec313296765ec3","The parametric representation of buoyancy and momentum transport by baroclinic eddies in a primitive equation 'β plane' channel is studied through a transformation of the governing equations. Adoption of the 'transformed Eulerian mean' and the assumption that the eddies (but not the mean flow) are quasigeostrophic in nature leads to 1) the eddies being represented symbolically by one term, an eddy potential vorticity flux, rendering a representation that incorporates both eddy momentum and eddy buoyancy fluxes, and 2) the advecting velocities being those of the residual mean circulation. A closure is employed for the eddy potential vorticity flux that directs it down the mean potential vorticity gradient. Care is taken to ensure that the resulting force does not generate any net momentum in the channel but only acts to redistribute it. The approach is investigated by comparing a zonally averaged parameterized model with a three-dimensional eddy-resolving calculation of flow in a stress-driven channel. The stress at the upper surface is communicated down the water column to the bottom by eddy form drag. Moreover, lateral eddy momentum fluxes act to strengthen and sharpen the mean flow, transporting eastward momentum from the flanks to the center of the jet, up its large-scale gradient. Both vertical momentum transfer and lateral, upgradient momentum transfer by eddies, is captured in the parameterized model. Finally, advantages of the parametric approach are demonstrated in two further contexts: 1) the spindown of a baroclinic zone and 2) the maintenance of surface winds by eddy momentum flux in the atmosphere."
"6701738452;7601582165;6701773156;","The impact of Southern Ocean sea ice in a Global Ocean model",1998,"10.1175/1520-0485(1998)028<1999:TIOSOS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033029986&doi=10.1175%2f1520-0485%281998%29028%3c1999%3aTIOSOS%3e2.0.CO%3b2&partnerID=40&md5=8b526e81e538679cf64eee3632be7943","Most of the Southern Ocean (SO) is marginally stably stratified and thus prone to enhanced convection and possibly bottom-water formation whenever the upper ocean is cooled or made more saline by ice formation. Sea ice modifies the heat and freshwater fluxes, which in turn constitute a critical surface condition in this sensitive region of intense vertical exchange. The authors investigate the effect of SO sea ice in modifying these fluxes in a global, coarse-resolution, primitive-equation ocean general circulation model, which has been coupled to a comprehensive dynamic-thermodynamic sea ice model. Specifically, the long-term impact of a series of modifications in the formulation of the sea ice model and its forcing on quantities such as the overturning circulation, the deep ocean water-mass characteristics, the sea ice thickness, the strength of convection, as well as the strength of the major volume transports are investigated. The results indicate that the rate of Antarctic bottom-water formation is strongly coupled to the local sea ice processes in the SO, which in turn vary sensitively depending on their model formulation and their forcing from the atmosphere. The largest impacts arise from the effect of brine release due to sea ice formation and that of employing more variable winds over SO sea ice."
"7004862184;7005163997;7003749832;","A sensitivity study of the general circulation of the Western Mediterranean Sea. Part II: The response to atmospheric forcing",1997,"10.1175/1520-0485(1997)027<2126:ASSOTG>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001109103&doi=10.1175%2f1520-0485%281997%29027%3c2126%3aASSOTG%3e2.0.CO%3b2&partnerID=40&md5=c45d6527cd3d8f5e167168983da43725","This paper investigates the influence of sea surface thermohaline fluxes and wind stress on the circulation of the Western Mediterranean Sea using a high-resolution 3D primitive equation model. An 18-year experiment was forced with the daily output of a fine grid mesh numerical weather prediction model. The major characteristics of the circulation are well reproduced. The basin surface circulation is cyclonic over all of the basin. The two anticyclonic Alboran gyres are present. The instabilities of the Algerian Current generate large anticyclonic eddies that invade the whole Algerian Basin. The Liguro-Provençal-Catalan Current is well marked. Deep water convection down to the bottom only occurs during the first 3 years, then winter intermediate water is produced. The north-south gradient of the atmospheric thermohaline fluxes induces a northward surface transport of water from the Algerian Basin into the Liguro-Provençal Basin. This pattern can be associated with the Balearic front. Sensitivity experiments show that the wind stress curl reinforces the cyclonic circulation of the Liguro-Provençal Basin through a Sverdrup balance mechanism and contributes to deep-water formation. It is also suggested that the variations of the transport in the Corsican Channel are linked to the wind stress action rather than the heat flux gradient between the Tyrrhenian and Ligurian Seas."
"56175660100;7201425334;6602761005;","The mechanical impact of the Tibetan Plateau on the seasonal evolution of the South Asian monsoon",2012,"10.1175/JCLI-D-11-00281.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859340683&doi=10.1175%2fJCLI-D-11-00281.1&partnerID=40&md5=95d9b2add506face6dab6319375fd9e8","The impact of the Tibetan Plateau on the South Asian monsoon is examined using a hierarchy of atmospheric general circulation models. During the premonsoon season and monsoon onset (April-June), when westerly winds over the Southern Tibetan Plateau are still strong, the Tibetan Plateau triggers early monsoon rainfall downstream, particularly over the Bay of Bengal and South China. The downstream moist convection is accompanied by strong monsoonal low-level winds. In experiments where the Tibetan Plateau is removed, monsoon onset occurs about a month later, but the monsoon circulation becomes progressively stronger and reaches comparable strength during the mature phase. During the mature and decaying phase of monsoon (July-September), when westerly winds over the Southern Tibetan Plateau almost disappear, monsoon circulation strength is not much affected by the presence of the Tibetan Plateau. A dry dynamical core with east-west-oriented narrow mountains in the subtropics consistently simulates downstream convergence with background zonal westerlies over the mountain. In a moist atmosphere, the mechanically driven downstream convergence is expected to be associated with significant moisture convergence. The authors speculate that the mechanically driven downstream convergence in the presence of the Tibetan Plateau is responsible for zonally asymmetric monsoon onset, particularly over the Bay of Bengal and South China. © 2012 American Meteorological Society."
"7005131869;11939816400;7005264401;6602529898;7403326970;57201410408;7006060201;7402523567;36100360300;8533912900;6603871013;7005813095;6507002063;53980793000;","Intercomparison of mesoscale model simulations of the daytime valley wind system",2011,"10.1175/2010MWR3523.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958755421&doi=10.1175%2f2010MWR3523.1&partnerID=40&md5=2453a95db0d0f068c87c8c2570675cbf","Three-dimensional simulations of the daytime thermally induced valley wind system for an idealized valley- plain configuration, obtained from nine nonhydrostatic mesoscale models, are compared with special emphasis on the evolution of the along-valley wind. The models use the same initial and lateral boundary conditions, and standard parameterizations for turbulence, radiation, and land surface processes. The evolution of the mean along-valley wind (averaged over the valley cross section) is similar for all models, except for a time shift between individual models of up to 2 h and slight differences in the speed of the evolution. The analysis suggests that these differences are primarily due to differences in the simulated surface energy balance such as the dependence of the sensible heat flux on surface wind speed. Additional sensitivity experiments indicate that the evolution of the mean along-valley flow is largely independent of the choice of the dynamical core and of the turbulence parameterization scheme. The latter does, however, have a significant influence on the vertical structureof the boundary layer and of the along-valley wind. Thus, this ideal case may be useful for testing and evaluation of mesoscale numerical models with respect to land surface-atmosphere interactions and turbulence parameterizations. © 2011 American Meteorological Society."
"15026371500;","Convectively coupled Kelvin waves in an idealized moist general circulation model",2007,"10.1175/JAS3945.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250805490&doi=10.1175%2fJAS3945.1&partnerID=40&md5=cd625fe4c83528832108c02ef1e106bc","The dynamics of convectively coupled Kelvin waves and their dependence on convection scheme parameters are studied within a simplified moist general circulation model. The model consists of the primitive equations on the sphere over zonally symmetric aquaplanet, slab mixed layer ocean boundary conditions, and idealized physical parameterizations including gray radiative transfer and a simplified Betts-Miller convection scheme. This framework allows the authors to study the dependence of Kelvin waves on quantities such as the gross moist stability in a clean manner. A control simulation with the model produces convectively coupled Kelvin waves that are remarkably persistent and dominate the variability within the Tropics. These waves propagate with an equivalent depth of ≈40 m. Linear regression analysis with respect to a Kelvin-filtered time series shows that the waves are driven by evaporation-wind feedback and have structures broadly consistent with theoretical predictions for Kelvin waves. Next, the determination of the speed and structure of the Kelvin waves is studied by examining the response of the waves to changes in convection scheme parameters. When the convective relaxation time is lengthened, the waves are damped and eventually are completely eliminated. The propagation speed additionally increases with longer relaxation time. Then changes to a convection scheme parameter that essentially controls the fraction of convective versus large-scale precipitation are examined. When some large-scale precipitation occurs, the waves increase in strength, propagate more slowly, and move to larger scales. However, when mostly large-scale precipitation occurs, the Kelvin wave disappears, and the Tropics are dominated by tropical storm-like variability. The decrease in speed is related here to the gross moist stability of the atmosphere, which is reduced with increased large-scale precipitation. © 2007 American Meteorological Society."
"7003494572;6701815637;6603718837;6701395093;","Decadal variability in high northern latitudes as simulated by an intermediate-complexity climate model",2001,"10.3189/172756401781818482","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035657774&doi=10.3189%2f172756401781818482&partnerID=40&md5=68bc5fdf8fca48c5e4c8bf420c5cb682","A 2500 year integration has been performed with a global coupled atmospheric-sea-ice-ocean model of intermediate complexity, with the main objective of studying the climate variability in polar regions on decadal time-scales and longer. The atmospheric component is the ECBILT model, a spectral T21 three-level quasi-geostrophic model that includes a representation of horizontal and vertical heat transfers as well as of the hydrological cycle. ECBILT is coupled to the CLIO model, which consists of a primitive-equation free-surface ocean general circulation model and a dynamic-thermodynamic sea-ice model. Comparison of model results with observations shows that the ECBILT-CLIO model is able to reproduce reasonably well the climate of the high northern latitudes. The dominant mode of coupled variability between the atmospheric circulation and sea-ice cover in the simulation consists of an annular mode for geopotential height at 800 hPa and of a dipole between the Barents and Labrador Seas for the sea-ice concentration which are similar to observed patterns of variability. In addition, the simulation displays strong decadal variability in the sea-ice volume, with a significant peak at about 18 years. Positive volume anomalies are caused by (1) a decrease in ice export through Fram Strait associated with more anticyclonic winds at high latitudes, (2) modifications in the freezing/melting rates in the Arctic due to lower air temperature and higher surface albedo, and (3) a weaker heat flux at the ice base in the Barents and Kara Seas caused by a lower inflow of warm Atlantic water. Opposite anomalies occur during the volume-decrease phase of the oscillation."
"7006245928;7103291058;7403370369;7404985678;","Impact of altimeter, thermistor, and expendable bathythermograph data on retrospective analyses of the tropical Pacific Ocean",1996,"10.1029/96jc00631","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029812222&doi=10.1029%2f96jc00631&partnerID=40&md5=51b98b33807eacf26487d2d3881314b6","This study explores the relative impact of three major components of the tropical Pacific Ocean observing system on data assimilation analyses. The extensive observing components that are available during the 2-year period from October 1992 through September 1994 include sea level derived from TOPEX/POSEIDON altimetry, thermistor data from the Tropical Ocean/Global Atmosphere Tropical Atmosphere-Ocean (TOGA TAO) mooring array, and expendable bathythermographs (XBTs) from the Volunteer Observing Ship program. In the first part of this study, methods are introduced to assimilate these data into a primitive equation model using optimal interpolation. The resulting velocity and thermal analyses are then compared with a numerical simulation that has no data assimilation. The most innovative aspect of the assimilation procedure is the development of a statistical model that uses satellite altimetry to update the subsurface thermal field. To determine the impact of individual components of the observing system, three additional experiments are conducted. In each experiment, one component is withheld from the assimilation. The resulting analysis is then compared with the missing data set. Our results show (1) To resolve major features of the seasonal cycle, it is necessary to have either the altimeter or the XBT data. In the absence of XBTs the analysis appears to develop a significant temporal drift in its thermal structure. (2) Intraseasonal variability such as tropical instability waves is best resolved using altimetry because of that data set's superior spatial resolution. (3) Thermistor data from the TOGA TAO mooring array are helpful, but not as crucial, in resolving the seasonal cycle within ±8° latitude as the XBTs. The mooring array is too coarsely spaced to allow this analysis system to resolve tropical instability waves. Copyright 1996 by the American Geophysical Union."
"7202946344;7102836087;","Frontal wave stability during moist deformation frontogenesis. Part I: linear wave dynamics",1994,"10.1175/1520-0469(1994)051<0852:FWSDMD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028561275&doi=10.1175%2f1520-0469%281994%29051%3c0852%3aFWSDMD%3e2.0.CO%3b2&partnerID=40&md5=64b9260aebf4c9234fd99d2c33a78079","It has been shown that lower tropospheric potential vorticity zones formed during moist deformation frontogenesis will support growing waves if at some time the frontogenesis ceases. In this paper, the ways in which these waves are affected by the frontogenetic process are identified. Observations show that fronts in the eastern Atlantic commonly feature saturated ascent regions characterized by zero moist potential vorticity. Furthermore, in many cases the horizontal temperature gradient in the lowest one to two kilometers of the atmosphere is rather weak. These features are incorporated in an analytical archetype. A semianalytical initial value solution for the linear development of waves on the evolving low-level potential vorticity anomaly is obtained. The waves approximately satisfy the inviscid primitive equations whenever the divergent part of the perturbation is negligible relative to the rotational part. The range of nonmodal wave developments supported by the front is summarized using RT phase diagrams. -from Authors"
"7004890337;","The energetically consistent shallow-water equations",1993,"10.1175/1520-0469(1993)050<1323:TECSWE>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027789426&doi=10.1175%2f1520-0469%281993%29050%3c1323%3aTECSWE%3e2.0.CO%3b2&partnerID=40&md5=c6f377795fa4a2b1edf1820a3df496d6","It is shown that the very frequently used form of the viscous, diabatic shallow-water equations are energetically inconsistent compared to the primitive equations. An energetically consistent form of the shallow-water equations is then given and justified in terms of isopycnal coordinates. Examples are given of the energetically inconsistent shallow-water equations used in low-order dynamical systems and simplified coupled models of tropical air-sea interaction and the EL Nino-Southern Oscillation phenomena. -Author"
"7201431739;55640299900;15119874600;57205291254;","Dynamical core of an atmospheric general circulation model on a Yin-Yang grid",2010,"10.1175/2010MWR3375.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958485258&doi=10.1175%2f2010MWR3375.1&partnerID=40&md5=a7fb7eb9de05ab97d342729ee711a33b","The three-dimensional dynamical core of an atmospheric general circulation model employing Yin-Yang grid is developed and examined. Benchmark test cases based on the shallow-water model configuration are first performed to examine the validity of two-dimensional calculations. The experiments show that the model simulates reasonable flow fields with second-order accuracy. The model validation is then extended to threedimensional features where the capability of the dynamical core on the Yin-Yang grid has not been tested before: the global mountain gravity wave, long-term integration, and life cycle experiments. The simulated flow fields are in good agreement with the results of original experiments in all three experiments. The sensitivity of the model flow field to the overset region is also tested. The experiments reveal that the presence of the overset region does not significantly affect the dynamics on both long and short time scales, if the number of overset grids is fixed to three and the high-order interpolation method is applied for data interpolation between the Yin-Yang grids. © 2010 American Meteorological Society."
"36077992900;7005874502;","Nonlinearity of the extratropical response to tropical forcing",2004,"10.1175/1520-0442(2004)017<2597:NOTERT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3843051446&doi=10.1175%2f1520-0442%282004%29017%3c2597%3aNOTERT%3e2.0.CO%3b2&partnerID=40&md5=90d608cc8e5f6931fd546a68998eef5a","A primitive equations dry atmospheric model is used to investigate the atmospheric response to a tropical diabatic forcing pattern and explore how the atmospheric response changes as a function of the amplitude of the forcing. The forcing anomaly represents a linear fit of the model forcing to a tropical SST pattern of an El Niño/La Niña type. The time-averaged 500-hPa geopotential height anomaly responses of two long integrations, with forcing anomalies of equal amplitudes but opposite signs, show an asymmetric feature that is similar to observations and to previous modeling results related to El Niño and La Niña. Ensemble experiments with 61 different amplitudes of this forcing pattern are conducted. An EOF analysis of the ensemble mean of the 90-day-averaged 500-hPa height for different amplitudes of forcings shows that the leading mode of the forced variability resembles the Pacific-North American (PNA) pattern, while the second mode is a wave train across the North Atlantic to Eurasia. The relationship between the amplitude of the PNA mode-and the amplitude of the forcing is linear, while the amplitude of the Atlantic/Eurasian mode has a nearly parabolic relationship with the amplitude of the forcing. A set of linear experiments with forcing perturbations and eddy flux anomalies associated with the positive and negative amplitudes of forcing conditions indicates that the nonlinearity of the extratropical response primarily results from the modification of the ""basic state"" caused by the large-amplitude forcing and the subsequent sensitivity of the response to that modified basic flow. A La Niña-type basic state yields a stronger response in the North Atlantic to the tropical Pacific forcing than does an El Niño-type basic state. © 2004 American Meteorological Society."
"7402435469;57212416832;","Dependence of aqua-planet simulations on time step",2003,"10.1256/qj.02.62","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037670504&doi=10.1256%2fqj.02.62&partnerID=40&md5=f070106855eb46b367d68365875751da","Aqua-planet simulations with Eulerian and semi-Lagrangian dynamical cores coupled to the NCAR CCM3 parametrization suite produce very different zonal average precipitation patterns. The model with the Eulerian core forms a narrow single precipitation peak centred on the sea surface temperature (SST) maximum. The one with the semi-Lagrangian core forms a broad structure often with a double peak straddling the SST maximum with a precipitation minimum centred on the SST maximum. The different structure is shown to be caused primarily by the different time step adopted by each core and its effect on the parametrizations rather than by different truncation errors introduced by the dynamical cores themselves. With a longer discrete time step, the surface exchange parametrization deposits more moisture in the atmosphere in a single time step, resulting in convection being initiated farther from the equator, closer to the maximum source. Different diffusive smoothing associated with different spectral resolutions is a secondary effect influencing the strength of the double structure. When the semi-Lagrangian core is configured to match the Eulerian with the same time step, a three-time-level formulation and same spectral truncation it produces precipitation fields similar to those from the Eulerian. It is argued that the broad and double structure forms in this model with the longer time step because more water is put into the atmosphere over a longer discrete time step, the evaporation rate being the same. The additional water vapour in the region of equatorial moisture convergence results in more convective available potential energy farther from the equator which allows convection to initiate farther from the equator. The resulting heating drives upward vertical motion and low-level convergence away from the equator, resulting in much weaker upward motion at the equator. The feedback between the convective heating and dynamics reduces the instability at the equator and decreases the convection there. The behaviour of the parametrizations depends on the amount of water inserted into the troposphere during a discrete time step. This is as important as the rate of insertion. Experiments are described that support this explanation."
"23989828200;6701369456;7005857465;","On the transport, variability and origin of dense water masses crossing the South Scotia Ridge",2002,"10.1016/S0967-0645(02)00160-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036406581&doi=10.1016%2fS0967-0645%2802%2900160-1&partnerID=40&md5=fe606a19b9ec1deb742300f45a9e73f2","The deep Scotia Sea is filled with ventilated Weddell Sea Deep Water. This in turn is an essential contributor to the ventilation of the World Ocean abyss. Depending on the formation process and/or its location along the Weddell Sea periphery, deep and bottom water masses follow different routes to cross the South Scotia Ridge. A primitive equation, hydrostatic, terrain-following coordinate ocean general circulation model (BRIOS-1) is used to investigate the water mass export from the Weddell Sea. The model is circumpolar focusing on the Weddell Sea, with particularly high resolution (∼20 km) in the DOVETAIL area. Eastward Weddell Sea Deep Water transport of 24 × 106m3s-1 is found in the northern limb of the Weddell Gyre across 44°W. Export rates of Weddell Sea Deep Water through gaps in the South Scotia Ridge are estimated to be 6.4 × 106m3s-1 with a semi-annual cycle of ±0.6 × 106m3s-1, which can be correlated to atmospheric cyclone activity and Weddell Gyre strength. Sensitivity studies considering extreme sea-ice conditions in the Weddell Sea show higher (lower) exports in years of minimum (maximum) winter sea-ice extent. Lagrangian particle trajectories illustrate the pathways of water masses from the inner Weddell Sea into the Scotia Sea through various gaps in the South Scotia Ridge. They highlight the existing flow divergence on the northwestern continental shelf, with one branch entering Bransfield Strait and the other continuing eastwards subsequently filling the deep Weddell and Scotia seas. Water masses flowing through the major gaps originate from the southwestern and southeastern Weddell Sea continental shelves. However, water masses formed east of the Weddell Sea (e.g., Prydz Bay) also seem to feed the deep Scotia Sea, since a large portion of floats flowing northward through the gaps of the South Scotia Ridge have been in contact with the mixed-layer processes outside the inner Weddell Sea. © 2002 Elsevier Science Ltd. All rights reserved."
"6701521854;13204242000;","An economical second-order advection scheme for numerical weather prediction",1999,"10.1256/smsqj.55815","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032695414&doi=10.1256%2fsmsqj.55815&partnerID=40&md5=0bae4a84b591d7a7d33759421d560de3","A very simple second-order Eulerian scheme for the advection equation, based on a forward (backward) time integration on even (odd) grid points, is studied. The proposed scheme is similar, but not equivalent, to the so-called 'hopscotch method', developed in the 1960s and early 1970s for the advection-diffusion equation, and is stable up to Courant number 2.0. It is shown that, in the case of the advection equation, the proposed scheme has the same advantages yielded by the forward-backward scheme in the case of the shallow-water equations; in particular, it is equivalent to the application of centred time and space differencing on the Eliassen grid. The new scheme, unlike the classical leapfrog scheme, can be coupled to the forward-backward integration of the gravity-wave problem in primitive-equation models. With the aid of the proposed scheme, an explicit version of the atmospheric, Bologna Limited-Area Model (developed in recent years at the FISBAT Institute of the National Council of Research of Italy) is devised, and a comparison with the semi-implicit version of the same model is performed. The explicit version runs with a double time step, achieving the same accuracy with significantly less computer time and storage. It is suggested that the new time scheme is particularly suitable for numerical weather prediction on massively parallel computing machines based on SIMD (Single Instruction Multiple Data) and distributed memory architecture, which strongly penalize non-local algorithms."
"6701387222;7402899368;6701374682;6602644981;","The effect of coastal upwelling on the sea-breeze circulation at Cabo Frio, Brazil: A numerical experiment",1998,"10.1007/s005850050656","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0542373810&doi=10.1007%2fs005850050656&partnerID=40&md5=ad9ace88f114b619dfead732e4107a64","The effect of coastal upwelling on sea-breeze circulation in Cabo Frio (Brazil) and the feedback of sea-breeze on the upwelling signal in this region are investigated. In order to study the effect of coastal upwelling on sea-breeze a non-linear, three-dimensional, primitive equation atmospheric model is employed. The model considers only dry air and employs boundary layer formulation. The surface temperature is determined by a forcing function applied to the Earth's surface. In order to investigate the seasonal variations of the circulation, numerical experiments considering three-month means are conducted: January-February- March (JFM), April-May-June (AMJ), July-August- September (JAS) and October-November-December (OND). The model results show that the sea-breeze is most intense near the coast at all the seasons. The sea- breeze is stronger in OND and JFM, when the upwelling occurs, and weaker in AMJ and JAS, when there is no upwelling. Numerical simulations also show that when the upwelling occurs the sea-breeze develops and attains maximum intensity earlier than when it does not occur. Observations show a similar behavior. In order to verify the effect of the sea-breeze surface wind on the upwelling, a two-layer finite element ocean model is also implemented. The results of simulations using this model, forced by the wind generated in the sea-breeze model, show that the sea-breeze effectively enhances the upwelling signal."
"7201554561;7004188723;","Is the time-mean Northern Hemisphere flow baroclinically unstable?",1998,"10.1175/1520-0469(1998)055<0041:ITTMNH>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031862086&doi=10.1175%2f1520-0469%281998%29055%3c0041%3aITTMNH%3e2.0.CO%3b2&partnerID=40&md5=b0099186275b8d5debf910a64e200378","The dynamical stability of the Northern Hemisphere wintertime mean atmosphere is investigated in a linearized primitive equation model. In the absence of any damping on the perturbation, exponentially growing modes are found for the zonal-mean and zonally varying basic states. Their growth rates are 0.41 and 0.38 days-1, respectively. Both have the form of midlatitude baroclinic wave trains. Three distinct idealized profiles of linear damping are then imposed on the perturbation vorticity and temperature. The damping is strongest below 800 mb and weak or nonexistent in the rest of the troposphere. It is specified to be proportional at all levels to a single parameter, Rs, the strength of damping at the surface. For the zonal-mean basic state, as Rs is increased linearly, the growing modes decrease their growth rates almost linearly, and change their structure only slowly. For an average damping timescale in the boundary layer of about one day (Rs = 2 days-1), the growing baroclinic modes are effectively neutralized. The wavy basic state is also rendered neutral when Rs reaches this value. It is argued that this magnitude of damping is within the range of observable parameters in the atmosphere. However, the precise position of the neutral point is sensitive to the relative magnitudes of temperature and vorticity damping. The latter is more efficient in stabilizing the system. For the wavy basic state, a second mode replaces the undamped mode as the fastest growing just before the neutral point is reached. This mode also resembles a midlatitude baroclinic wave train, but has a longer zonal wavelength. Zonal-mean transient fluxes of eddy temperature and momentum, and eddy kinetic energy calculated for this mode, show an improvement over the undamped and zonal-mean modes when compared with observations. It is argued that this improvement may be meaningful, particularly in an atmosphere that is close to neutral."
"7003545639;7004014731;","Planetary-scale circulations forced by intraseasonal variations of observed convection",1996,"10.1175/1520-0469(1996)053<1751:PSCFBI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030440035&doi=10.1175%2f1520-0469%281996%29053%3c1751%3aPSCFBI%3e2.0.CO%3b2&partnerID=40&md5=e2b695096822efa5ae38cfdf2663d18b","Interhemispheric differences of the Madden-Julian oscillation (MJO) are investigated in a linearized primitive equation model. Heating is prescribed from the observed life cycle of the MJO, in which anomalous convection is concentrated in the Eastern Hemisphere. The dynamical response in the Eastern Hemisphere has the form of a forced disturbance that involves Kelvin and Rossby components. These dynamical components propagate eastward along with the prescribed heating and have zonal wavenumber-2 structure, in accord with observed behavior. The behavior in the Eastern Hemisphere also resembles that emerging from frictional wave-CISK, in which heating follows autonomously from the circulation. When the prescribed heating collapses near the date line, the Rossby component dissipates. The Kelvin component, however, continues to advance across the Western Hemisphere, where it propagates at more than twice the speed of the disturbance in the Eastern Hemisphere. The disturbance in the Western Hemisphere, which likewise is in accord with the observed behavior, can be understood as the radiating response to transient heating confined to the Eastern Hemisphere."
"15768654400;8205917100;7201600456;7102023422;6701652354;6505742223;26643566500;55707756600;55856122800;","Observation bias correction with an ensemble Kalman filter",2009,"10.1111/j.1600-0870.2008.00378.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-61349192672&doi=10.1111%2fj.1600-0870.2008.00378.x&partnerID=40&md5=17f0db38e950c1e09741e53f78f85454","This paper considers the use of an ensemble Kalman filter to correct satellite radiance observations for state dependent biases. Our approach is to use state-space augmentation to estimate satellite biases as part of the ensemble data assimilation procedure. We illustrate our approach by applying it to a particular ensemble scheme - the local ensemble transform Kalman filter (LETKF) - to assimilate simulated biased atmospheric infrared sounder brightness temperature observations from 15 channels on the simplified parameterizations, primitive-equation dynamics (SPEEDY) model. The scheme we present successfully reduces both the observation bias and analysis error in perfect-model simulations. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard."
"6506238357;7006735547;7004060399;","The coupled stratosphere-troposphere response to impulsive forcing from the troposphere",2005,"10.1175/JAS3527.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27544441388&doi=10.1175%2fJAS3527.1&partnerID=40&md5=0284dcd12603492e45cdbfc661748bca","A simple atmospheric general circulation model (GCM) is used to investigate the transient response of the stratosphere-troposphere system to externally imposed pulses of lower-tropospheric planetary wave activity. The atmospheric GCM is a dry, hydrostatic, global primitive-equations model, whose circulation includes an active polar vortex and a tropospheric jet maintained by baroclinic eddies. Planetary wave activity pulses are generated by a perturbation of the solid lower boundary that grow and decay over a period of 10 days. The planetary wave pulses propagate upward and break in the stratosphere. Subsequently, a zonal-mean circulation anomaly propagates downward, often into the troposphere, at lags of 30-100 days. The evolution of the response is found to be dependent on the state of the stratosphere-troposphere system at the time the pulse is generated. In particular, on the basis of a large ensemble of these simulations, it is found that the length of time the signal takes to propagate downward from the stratosphere is controlled by initial anomalies in the zonal-mean circulation and in the zonal-mean wave drag. Criteria based on these anomaly patterns can be used, therefore, to predict the long-term surface response of the stratosphere-troposphere system to a planetary wave pulse up to 90 days after the pulse is generated. In an independent test, it is verified that the initial states that most strongly satisfy these criteria respond in the expected way to the lower-tropospheric wave activity pulse. © 2005 American Meteorological Society."
"6603887794;7102367341;","Response of the stratosphere to interannual variability of tropospheric planetary waves",2000,"10.1002/qj.49712656214","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034032775&doi=10.1002%2fqj.49712656214&partnerID=40&md5=cc1a2f93932cc1b2d0dfe99eae9b3db9","A primitive-equation global model of the middle atmosphere is used to investigate the response of the extratropical stratosphere to different levels of wave forcing from steady perturbations of the geopotential height near the tropopause. The response of the stratosphere is compared to that in quasi-geostrophic beta-plane models used in previous studies. The primitive-equation model exhibits three flow regimes under perpetual-January conditions: strong westerly, steady flow for small wave-amplitude forcing, strong westerly but unsteady flow for moderate wave-amplitude forcing and oscillations between easterly and westerfly flow for large wave-amplitude forcing. The regimes for low and high forcing are analogous to solutions of the simpler Holton-Mass (HM) quasi-geostrophic model. The moderate-forcing regime does not occur in the HM model and it is attributed to instability of the strongly sheared flow generated by planetary waves in the upper stratosphere. We also show how the observed patterns of interannual variability in the winter stratosphere can be explained in terms of these three flow regimes: in the northern hemisphere the flow often enters the high-forcing regime, where variations in conditions in the early-winter flow or quasi-steady upper-tropospheric planetary-wave amplitudes make similar contributions to the interannual variability in the stratospheric circulation. For the southern hemisphere, we suggest that the flow alternates between the low- and moderate-forcing regimes through year-to-year changes in the amplitude of quasi-steady waves near the tropopause. This mechanism produces large enough changes to explain the interannual variability in the southern stratosphere."
"35585811600;6602566390;57194045072;","The onset of the Spring Bloom in the MEDOC area: Mesoscale spatial variability",1999,"10.1016/S0967-0637(98)00105-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033168898&doi=10.1016%2fS0967-0637%2898%2900105-8&partnerID=40&md5=2266c47e509d2f00c6bfe9338010c6e7","In the northwestern Mediterranean Sea, Coastal Zone Color Scanner images suggest that the eddies that participate in the restratification following deep convection interact with the spring phytoplankton bloom. The mechanisms for this interaction are studied using a biogeochemical model embedded in an eddy-resolving primitive equation ocean model. The model is initialized with a patch of dense water surrounded by a stratified ocean, which is characteristic of the winter situation. The atmospheric forcing is artificially held constant, in order to focus solely on the mesoscale variability. After a few days, meanders develop at the periphery of the patch, inducing its sinking and spreading. Mesoscale upward motions are responsible for the shoaling of the mixing layer in the trough of the meanders. As sunlight is the main factor regulating primary production at this time of year, this shoaling increases the mean exposure time of the phytoplankton cells and thus enhances productivity. Consequently, the majority of phytoplankton production is obtained at the edge of the patch, in agreement with in situ data. Through advection, phytoplankton is then subducted from these sources towards the crest of the meanders. Our results suggest that this mesoscale transport is responsible for a decorrelation between phytoplankton biomass and primary production."
"7202386372;36660334400;6602194298;","A numerical study of the effects of differential cloud cover on cold frontal structure and dynamics",1995,"10.1175/1520-0469(1995)052<0937:ANSOTE>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029412298&doi=10.1175%2f1520-0469%281995%29052%3c0937%3aANSOTE%3e2.0.CO%3b2&partnerID=40&md5=85e14ad045d31a6aabe82e112965f4b8","The effects of sensible heating and momentum mixing on the low-level structure and dynamics of a two-dimensional cold front are studied with a hydrostatic primitive equation model. Effects of inhomogeneous heating arising from a contrast in low-level cloud cover across the front are emphasized. A strong, narrow updraft jet forms in the presence of uniform sensible heating across the front. Although the greatest impact on frontogenesis occurs as a response to the reduction in static stability resulting from uniform sensible heating, additional forcing results from the nonlinear interaction between the adiabatic frontal circulation and the thermally forced circulation arising from a cross-front gradient in heating (due to the introduction of an overcast low cloud deck behind the front). These results suggest that differential cloud cover across cold fronts may promote the development of frontal squall lines. -from Authors"
"57216084744;16185051500;","The mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones. Part XV: a numerical modeling study of frontogenesis and cold-frontal rainbands",1988,"10.1175/1520-0469(1988)045<0915:tmamsa>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024258443&doi=10.1175%2f1520-0469%281988%29045%3c0915%3atmamsa%3e2.0.co%3b2&partnerID=40&md5=225997e48f615be21fd9df33b1007dc3","A two-dimensional, hydrostatic, primitive-equation model is used to investigate the dynamics of frontogenesis in a moist atmosphere. The development of a cold front is simulated through shear-deformation associated with the non-linear evolution of an Eady wave. Compared to the dry case, the inclusion of moisture in the model produces a stronger low-level jet ahead of the front and a stronger upper-level jet. Moisture also produces a stronger ageostrophic circulation across the front and a more concentrated updraft just ahead of the surface front. The updraft develops a banded structure above and behind the surface front, with a wavelength of about 70km. Bands form near the back edge of the cloud shield and move toward the surface front with a relative velocity of ~1m s-1. These characteristics agree with observations of wide cold-frontal rainbands. The banded structures form in a convectively stable region. Frictional convergence in the boundary layer forces a narrow cold frontal rainband (NCFR) just above the surface front. The horizontal dimension of this band is greater than that for observed NCFR, presumably because of limited resolution in the model. -from Authors"
"33367455100;16022263500;55967916100;26659116700;35321650700;56942309200;55628584418;6507393330;22134847000;","The UK Met Office global circulation model with a sophisticated radiation scheme applied to the hot Jupiter HD 209458b",2016,"10.1051/0004-6361/201629183","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992730385&doi=10.1051%2f0004-6361%2f201629183&partnerID=40&md5=f576319888224221419c07a9c5c1b181","To study the complexity of hot Jupiter atmospheres revealed by observations of increasing quality, we have adapted the UK Met Office Global Circulation Model (GCM), the Unified Model (UM), to these exoplanets. The UM solves the full 3D Navier-Stokes equations with a height-varying gravity, avoiding the simplifications used in most GCMs currently applied to exoplanets. In this work we present the coupling of the UM dynamical core to an accurate radiation scheme based on the two-stream approximation and correlated-k method with state-of-the-art opacities from ExoMol. Our first application of this model is devoted to the extensively studied hot Jupiter HD 209458b. We have derived synthetic emission spectra and phase curves, and compare them to both previous models also based on state-of-the-art radiative transfer, and to observations. We find a reasonable agreement between observations and both our days side emission and hot spot offset, however, our night side emissions is too large. Overall our results are qualitatively similar to those found by Showman et al. (2009, ApJ, 699, 564) with the SPARC/MITgcm, however, we note several quantitative differences: Our simulations show significant variation in the position of the hottest part of the atmosphere with pressure, as expected from simple timescale arguments, and in contrast to the ""vertical coherency"" found by Showman et al. (2009). We also see significant quantitative differences in calculated synthetic observations. Our comparisons strengthen the need for detailed intercomparisons of dynamical cores, radiation schemes and post-processing tools to understand these differences. This effort is necessary in order to make robust conclusions about these atmospheres based on GCM results. © 2016 ESO."
"55119602800;15830929400;24468389200;7404976222;7501757094;54403961000;55220443400;55656840900;7410069943;","Global energy and water balance: Characteristics from finite-volume atmospheric model of the IAP/LASG (FAMIL1)",2015,"10.1002/2014MS000349","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027956192&doi=10.1002%2f2014MS000349&partnerID=40&md5=a210805c1d914b4397f487617c46f132","This paper documents version 1 of the Finite-volume Atmospheric Model of the IAP/LASG (FAMIL1), which has a flexible horizontal resolution up to a quarter of 1°. The model, currently running on the ""Tianhe 1A"" supercomputer, is the atmospheric component of the third-generation Flexible Global Ocean-Atmosphere-Land climate System model (FGOALS3) which will participate in the Coupled Model Intercomparison Project Phase 6 (CMIP6). In addition to describing the dynamical core and physical parameterizations of FAMIL1, this paper describes the simulated characteristics of energy and water balances and compares them with observational/reanalysis data. The comparisons indicate that the model simulates well the seasonal and geographical distributions of radiative fluxes at the top of the atmosphere and at the surface, as well as the surface latent and sensible heat fluxes. A major weakness in the energy balance is identified in the regions where extensive and persistent marine stratocumulus is present. Analysis of the global water balance also indicates realistic seasonal and geographical distributions with the global annual mean of evaporation minus precipitation being approximately 10-5 mm d-1. We also examine the connections between the global energy and water balance and discuss the possible link between the two within the context of the findings from the reanalysis data. Finally, the model biases as well as possible solutions are discussed. © 2015. The Authors."
"56384704800;57202299549;7601556245;7405919136;","Evaluation of the atmospheric transport in a GCM using radon measurements: Sensitivity to cumulus convection parameterization",2008,"10.5194/acp-8-2811-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44649180492&doi=10.5194%2facp-8-2811-2008&partnerID=40&md5=9df9d57d50728145ed5f63cc9064b21f","The radioactive species radon (222Rn) has long been used as a test tracer for the numerical simulation of large scale transport processes. In this study, radon transport experiments are carried out using an atmospheric GCM with a finite-difference dynamical core, the van Leer type FFSL advection algorithm, and two state-of-the-art cumulus convection parameterization schemes. Measurements of surface concentration and vertical distribution of radon collected from the literature are used as references in model evaluation. The simulated radon concentrations using both convection schemes turn out to be consistent with earlier studies with many other models. Comparison with measurements indicates that at the locations where significant seasonal variations are observed in reality, the model can reproduce both the monthly mean surface radon concentration and the annual cycle quite well. At those sites where the seasonal variation is not large, the model is able to give a correct magnitude of the annual mean. In East Asia, where radon simulations are rarely reported in the literature, detailed analysis shows that our results compare reasonably well with the observations. The most evident changes caused by the use of a different convection scheme are found in the vertical distribution of the tracer. The scheme associated with weaker upward transport gives higher radon concentration up to about 6 km above the surface, and lower values in higher altitudes. In the lower part of the atmosphere results from this scheme does not agree as well with the measurements as the other scheme. Differences from 6 km to the model top are even larger, although we are not yet able to tell which simulation is better due to the lack of observations at such high altitudes."
"55469187200;","Barotropic instability and equatorial superrotation",2003,"10.1175/1520-0469(2003)060<2136:BIAES>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141573103&doi=10.1175%2f1520-0469%282003%29060%3c2136%3aBIAES%3e2.0.CO%3b2&partnerID=40&md5=f9fadc4bf378b0d57e97a3bf0184931c","Baroclinically unstable zones in midlatitudes normally produce medium-scale planetary waves that propagate toward the equator where they generate easterlies while transferring westerly momentum poleward, so that the jet lies in higher latitudes than in the corresponding axisymmetric (eddy-free) state. When the baroclinically unstable zone is moved into low latitudes, however, the equatorward side of the jet can also produce a barotropic instability whose large-scale eddies lead to a strong superrotating westerly current at the equator: the jet remains close to its axisymmetric location. For the earth, the transition between these two regimes occurs when the jet lies close to 30°, according to calculations with a global, multilevel, spectral, primitive equation model that examines superrotating flows for a wide range of rotation rates. The existence of a stable superrotating regime implies that an alternative climate could occur, but only under novel conditions."
"6701358470;6603703438;","Multiscale diagnosis of the North American monsoon system using a variable-resolution GCM",2003,"10.1175/1520-0442(2003)016<1929:MDOTNA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042847370&doi=10.1175%2f1520-0442%282003%29016%3c1929%3aMDOTNA%3e2.0.CO%3b2&partnerID=40&md5=b116820d691343c3893030e1f17d4376","The onset and evolution of the North American monsoon system during the summer of 1993 were examined from regional to large scales using the National Aeronautics and Space Administration (NASA) Goddard Earth Observing System (GEOS) stretched-grid GCM. The model's grid spacing for the dynamical core ranges from 0.4° × 0.5° in latitude-longitude over the United States to about 2.5° × 3.5° at the antipode, and the physical package is solved on an intermediate 1° × 1° uniform grid. A diagnostic analysis of the monsoon's onset reveals the development of a positive potential temperature (χ) anomaly at the surface that favors a lower-level cyclonic circulation, while a negative potential vorticity (PV) anomaly below the tropopause induces an upper-level anticyclonic circulation. Ignoring diabatic effects, this pattern is consistent with the superimposition of idealized PV and χ anomalies as previously discussed in the literature. The inclusion of the smaller-scale features of the core monsoon in the model simulation helps represent the continental out-of-phase relationship between the monsoon and the southern Great Plains precipitation, giving additional support to earlier results that highlight the strong nature of the link. A pattern of increased precipitation over the core monsoon is consistently associated with increases of moisture flux convergence and ascending motions, and the development of upper-level wind divergence. On the other hand, the southern Great Plains have a simultaneous decrease of precipitation associated with a change from convergence to divergence of moisture flux, decreased ascending motions, and a development of upper-level wind convergence. The Gulf of California low-level jet (LLJ) was inspected with a multitaper method spectral analysis, showing significant peaks for both the diurnal cycle and synoptic-scale modes, the latter resulting from the recurrent passage of Gulf surges. Those modes were then separated with a singular spectrum analysis decomposition. Compared with the Great Plains LLJ, the Gulf of California LLJ has a weaker diurnal cycle amplitude and a smaller ratio of diurnal cycle to synoptic-scale amplitudes. Additionally, the 1993 southwestern U.S. monsoon was analyzed by constructing composites of surge and no-surge cases. Given the particular characteristics of 1993 that include the effect of Hurricane Hilary, the extension of these results to other years needs to be assessed. Surges are associated with a strong Gulf of California LLJ and increased moisture flux from the Gulf into Arizona, and they accounted for 80%-100% of the simulated precipitation over Arizona, western New Mexico, and southern Utah. As distance from the Gulf is increased, there is a rapid decay of this percentage so that northern Utah and eastern New Mexico precipitation is almost unrelated to the surges. The results from this research show that the model's regional downscaling results in a realistic representation of the monsoon-related circulations at multiple scales."
"56744297600;6602688130;35498837200;8285351400;","Decadal variability and predictability in the midlatitude ocean-atmosphere system",2000,"10.1175/1520-0442(2000)013<1073:DVAPIT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033923549&doi=10.1175%2f1520-0442%282000%29013%3c1073%3aDVAPIT%3e2.0.CO%3b2&partnerID=40&md5=1f959cc272656c682a72d7ee225701d3","The coupled ocean-atmosphere interaction and predictability associated with the tropical El Nino phenomenon has motivated researchers to seek analogous phenomena in the midlatitudes as well. Are there midlatitude coupled ocean-atmosphere modes? Is there significant predictability in the midlatitudes? The authors address these questions in the broader context of trying to understand the mechanisms behind midlatitude variability, using an idealized model of the ocean-atmosphere system. The atmosphere is represented using a global two-level eddy-resolving primitive equation model with simplified physical parameterizations. The ocean is represented using a state-of-the-art ocean general circulation model, but configured in a simple Atlantic-like sector geometry. In addition to a coupled integration using this model, uncoupled integrations of the component oceanic and atmospheric models are also carried out to elucidate the mechanisms behind midlatitude variability. The sea surface temperature in the coupled equilibrium state exhibits two dominant modes of variability: (i) a passive oceanic red noise response to stochastic atmospheric forcing, and (ii) an active oceanic mode of variability that is partially excited by atmospheric forcing, and is associated with a periodicity of 16-20 yr. True coupled ocean-atmosphere modes do not appear to play any quantitatively significant role in the midlatitudes, due to the fundamentally different nature of atmospheric dynamics in the midlatitudes compared to the Tropics. However, coupling to the atmosphere does play an important role in determining the spatial and temporal characteristics of the oceanic variability. A statistical assessment suggests that midlatitude atmospheric predictability is modest compared to the predictability associated with tropical phenomena such as El Nino. This predictability arises from the atmospheric response to oceanic modes of variability, rather than from coupled modes. There is significant oceanic predictability on interannual timescales but not on decadal timescales.The coupled ocean-atmosphere interaction and predictability associated with the tropical El Nino phenomenon has motivated researchers to seek analogous phenomena in the midlatitudes as well. Are there midlatitude coupled ocean-atmosphere modes? Is there significant predictability in the midlatitudes? The authors address these questions in the broader context of trying to understand the mechanisms behind midlatitude variability, using an idealized model of the ocean-atmosphere system. The atmosphere is represented using a global two-level eddy-resolving primitive equation model with simplified physical parameterizations. The ocean is represented using a state-of-the-art ocean general circulation model, but configured in a simple Atlantic-like sector geometry. In addition to a coupled integration using this model, uncoupled integrations of the component oceanic and atmospheric models are also carried out to elucidate the mechanisms behind midlatitude variability. The sea surface temperature in the coupled equilibrium state exhibits two dominant modes of variability: (i) a passive oceanic red noise response to stochastic atmospheric forcing, and (ii) an active oceanic mode of variability that is partially excited by atmospheric forcing, and is associated with a periodicity of 16-20 yr. True coupled ocean-atmosphere modes do not appear to play any quantitatively significant role in the midlatitudes, due to the fundamentally different nature of atmospheric dynamics in the midlatitudes compared to the Tropics. However, coupling to the atmosphere does play an important role in determining the spatial and temporal characteristics of the oceanic variability. A statistical assessment suggests that midlatitude atmospheric predictability is modest compared to the predictability associated with tropical phenomena such as El Nino. This predictability arises from the atmospheric response to oceanic modes of variability, rather than from coupled modes. There is significant oceanic predictability on interannual timescales but not on decadal timescales."
"7201554561;7005874502;","Transience, nonlinearity, and eddy feedback in the remote response to El Niño",2000,"10.1175/1520-0469(2001)058<3992:TNAEFI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034351752&doi=10.1175%2f1520-0469%282001%29058%3c3992%3aTNAEFI%3e2.0.CO%3b2&partnerID=40&md5=05a156b3f03cf11d3e35ff1df8e81e8a","A dry primitive equation model is used to investigate the remote response to a fixed tropical heat source. The basic forcing for the model takes the form of time-independent terms added to the prognostic equations in two configurations. One produces a perturbation model, in which anomalies grow on a fixed basic state. The other gives a simple GCM, which can be integrated for a long time and delivers a realistic climate simulation with realistic storm tracks. A series of experiments is performed, including 15-day perturbation runs, ensemble experiments, and long equilibrium runs, to isolate different dynamical influences on the fully developed Pacific-North American (PNA) type response to an equatorial heating anomaly centered on the date line. The direct linear response is found to be very sensitive to changes in the basic state of the same order as the atmosphere's natural variability, and to the natural progression of the basic state over the time period required to set up the response. However, interactions with synoptic-scale noise in the ambient flow are found to have very little systematic effect on the linear response. Nonlinear interactions with a fixed basic state lead to changes in the position, but not the amplitude, of the response. Feedback with finite-amplitude transient eddies leads to downstream amplification of the PNA pattern, both within the setup time for the response and in a fully adjusted equilibrium situation. Nonlinearity of the midlatitude dynamics gives rise to considerable asymmetry between the response to tropical heating and the response to an equal and opposite cooling."
"7003968166;6602227892;6701847229;","The effect of barotropic shear on upper-level induced cyclogenesis: Semigeostrophic and primitive equation numerical simulations",1998,"10.1175/1520-0469(1998)055<2080:TEOBSO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031827176&doi=10.1175%2f1520-0469%281998%29055%3c2080%3aTEOBSO%3e2.0.CO%3b2&partnerID=40&md5=7a659cc48e3172140d67fc86c537e98d","Idealized numerical experiments within the frameworks of semigeostrophic and primitive equation dynamics were performed to study the effect of barotropic shear on idealized upper-level induced cyclogenesis. Localized finite-amplitude potential temperature anomalies were used as initial perturbations, and the atmosphere was considered as a dry frictionless fluid of uniform quasigeostrophic potential vorticity on an f-plane. It is demonstrated that the main features of the numerical simulations are in essence unaffected by the choice of the dynamical framework. They comprise, for instance, the development of elongated cold fronts under anticyclonically sheared conditions, a ""T-bone"" shaped frontal palette in the unsheared case (cf. Shapiro and Keyser), and a Bergen-type occlusion process in the simulations with cyclonic shear. This confirms the profound dynamical influence of lateral shear in the background environment upon the resulting surface cyclone and frontal structures (and the accompanying evolutions at upper levels) that has been found in previous normal-mode experiments. This sensitivity is shown to be related to the different orientation of the additional deformation field associated with the background shear. The differences between surface cold and warm fronts are analyzed in more detail using a combined Eulerian and Lagrangian approach. Consideration is also given to the shortcomings of the present approach and to a possible strategy for further idealized model investigations."
"7403346393;","Self-memorization equation in atmospheric motion",1993,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027799627&partnerID=40&md5=d011f282353b2b19480e01df0286a383","In view of the fact that the atmospheric motion is an irreversible process, a memory function which can recall observational data in the past is suggested. In terms of defining an inner product in Hilbert space, a new concept of self-memorization in the atmospheric motion is proposed, thus the traditional atmospheric motion equation is generalized to a self-memorization equation in inclusion of multi-time observations. Self-memorization equations of a barotropic nondivergent model and a barotropic primitive equation model are exemplified. It is proved that some existing difference schemes can be derived from the self-memorization equation by giving particular values to memory function. However, it demonstrates that multi-time numerical prediction models can be unified into a framework of self-memorization equation. If a stochastic method in solving the memory function is taken, the self-memorization equation will be transformed to a sort of dynamic-stochastic prediction model. © 1993."
"6603247427;14622350200;35605362100;6701689939;56324515500;14825002300;11939918300;10241177500;8263759800;7003465848;8696069500;55339081600;24067647600;56154540200;16242524600;24169799700;7404732357;35303197200;56273658200;55437450100;57202299549;53980793000;7201504886;","ICON-A, the Atmosphere Component of the ICON Earth System Model: I. Model Description",2018,"10.1029/2017MS001242","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050490810&doi=10.1029%2f2017MS001242&partnerID=40&md5=db57cd748525a1f6ffebe841ffcf96ef","ICON-A is the new icosahedral nonhydrostatic (ICON) atmospheric general circulation model in a configuration using the Max Planck Institute physics package, which originates from the ECHAM6 general circulation model, and has been adapted to account for the changed dynamical core framework. The coupling scheme between dynamics and physics employs a sequential updating by dynamics and physics, and a fixed sequence of the physical processes similar to ECHAM6. To allow a meaningful initial comparison between ICON-A and the established ECHAM6-LR model, a setup with similar, low resolution in terms of number of grid points and levels is chosen. The ICON-A model is tuned on the base of the Atmospheric Model Intercomparison Project (AMIP) experiment aiming primarily at a well balanced top-of atmosphere energy budget to make the model suitable for coupled climate and Earth system modeling. The tuning addresses first the moisture and cloud distribution to achieve the top-of-atmosphere energy balance, followed by the tuning of the parameterized dynamic drag aiming at reduced wind errors in the troposphere. The resulting version of ICON-A has overall biases, which are comparable to those of ECHAM6. Problematic specific biases remain in the vertical distribution of clouds and in the stratospheric circulation, where the winter vortices are too weak. Biases in precipitable water and tropospheric temperature are, however, reduced compared to the ECHAM6. ICON-A will serve as the basis of further development and as the atmosphere component to the coupled model, ICON-Earth system model (ESM). ©2018. The Authors."
"6507127669;7004048039;57210540117;54388319300;6602178996;6507506899;","Description and analysis of the ocean component of NOAA'S operational hurricane weather research and forecasting model (HWRF)",2015,"10.1175/JTECH-D-14-00063.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84921673992&doi=10.1175%2fJTECH-D-14-00063.1&partnerID=40&md5=972169f55c62d316c68cb35d548248de","The Princeton Ocean Model for Tropical Cyclones (POM-TC), a version of the three-dimensional primitive equation numerical ocean model known as the Princeton Ocean Model, was the ocean component of NOAA's operational Hurricane Weather Research and Forecast Model (HWRF) from 2007 to 2013. The coupled HWRF-POM-TC system facilitates accurate tropical cyclone intensity forecasts through proper simulation of the evolving SST field under simulated tropical cyclones. In this study, the 2013 operational version of HWRF is used to analyze the POM-TC ocean temperature response in retrospective HWRF-POM-TC forecasts of Atlantic Hurricanes Earl (2010), Igor (2010), Irene (2011), Isaac (2012), and Leslie (2012) against remotely sensed and in situ SST and subsurface ocean temperature observations. The model generally underestimates the hurricane-induced upper-ocean cooling, particularly far from the storm track, as well as the upwelling and downwelling oscillation in the cold wake, compared with observations. Nonetheless, the timing of the model SST cooling is generally accurate (after accounting for along-track timing errors), and the ocean model's vertical temperature structure is generally in good agreement with observed temperature profiles from airborne expendable bathythermographs. © 2015 American Meteorological Society."
"6602249313;6602208272;35514012200;7404865693;8884425800;","Impact of sea surface salinity assimilation on coupled forecasts in the tropical Pacific",2011,"10.1029/2010JC006708","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957493251&doi=10.1029%2f2010JC006708&partnerID=40&md5=ebc874c4662077b428b0df882b90f90e","In this paper, we assess the impact of sea surface salinity (SSS) observations on seasonal variability of tropical dynamics as well as on dynamical El Nio-Southern Oscillation (ENSO) forecasts using a hybrid coupled model (HCM). The HCM is composed of a primitive equation ocean model coupled with a singular value decomposition-based statistical atmospheric model. An Ensemble Reduced Order Kalman Filter (EROKF) is used to assimilate observations to constrain tropical Pacific dynamics and thermodynamics for initialization of the HCM. Rather than trying to produce the best possible operational forecasts, point-wise subsurface temperature (sTz) has been assimilated separately and together with gridded observed sea surface salinity (SSS) from optimal interpolation to more efficiently isolate the impact of SSS. Coupled experiments are then initiated from these EROKF initial conditions and run for 12 months for each month, 1993-2007. The results show that adding SSS to sTz assimilation improves coupled forecasts for 6-12 month lead times. The main benefit of SSS assimilation comes from improvement to the spring predictability barrier (SPB) period. SSS assimilation increases correlation for 6-12 month forecasts by 0.2-0.5 and reduces RMS error by 0.3C-0.6C for forecasts initiated between December and March, a period key to long-lead ENSO forecasts. The positive impact of SSS assimilation originates from warm pool and Southern Hemisphere salinity anomalies. Improvements are brought about by fresh anomalies at the equator which increases stability, reduces mixing, and shoals the thermocline which concentrates the wind impact of ENSO coupling. This effect is most pronounced in June-August, helping to explain the improvement in the SPB. In addition, we show that SSS impact on coupled forecasts is more pronounced for the period 1993-2001 than for the period 2002-2007 due to the improved inherent predictability associated with the strong 1997-1998 ENSO. Rather than being the final say for the issue of SSS assimilation, this study should be considered as a necessary first step. Future work is still required to assess issues such as SSS satellite data coverage and the complementary nature of satellite/in situ assimilation. However, these results foreshadow the important positive potential impact that gridded satellite SSS provided by missions such as SMOS and Aquarius/SAC-D will have on coupled model predictions. Copyright 2011 by the American Geophysical Union."
"7005874502;36077992900;7005720566;","Seasonal forecasting with a simple general circulation model: Predictive skill in the AO and PNA",2005,"10.1175/JCLI-3289.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16344387337&doi=10.1175%2fJCLI-3289.1&partnerID=40&md5=090f3fa247966686b53825a4287ce6dd","A primitive equation dry atmospheric model is used to perform ensemble seasonal predictions. The predictions are done for 51 winter seasons [December-January-February (DJF)] from 1948 to 1998. Ensembles of 24 forecasts are produced, with initial conditions of 1 December plus small perturbations. The model uses a forcing field that is calculated empirically from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalyses. The forcing used to forecast a given winter is the sum of its winter climatological forcing plus an anomaly. The anomalous forcing is obtained as that of the month prior to the start of the forecast (November), which is also calculated from NCEP data. The predictions are thus made without using any information about the season to be predicted. The ensemble-mean predictions for the 51 winters are verifie d against the NCEP-NCAR reanalyses. Comparisons are made with the results obtained with a full GCM. It is found that the skill of the simple GCM is comparable in many ways to that of the full GCM. The skill in predicting the amplitude of the main patterns of Northern Hemisphere mean-seasonal variability, the Arctic Oscillation (AO) and the Pacific-North American (PNA) pattern is also discussed. The simple GCM has skill not only in predicting the PNA pattern during winters with strong ENSO forcing, but it also has skill in predicting the AO in winters without appreciable ENSO forcing. © 2005 American Meteorological Society."
"7007098614;25953950400;35453054300;","Numerical simulation of tornadogenesis in a high-precipitation supercell. Part I: Storm evolution and transition into a bow echo",2001,"10.1175/1520-0469(2001)058<1597:NSOTIA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035389744&doi=10.1175%2f1520-0469%282001%29058%3c1597%3aNSOTIA%3e2.0.CO%3b2&partnerID=40&md5=36a7696c3e0ad2138cf761df5936f0a3","A nested grid primitive equation model (RAMS version 3b) was used to simulate a high-precipitation (HP) supercell, which produced two weak tornadoes. Six telescoping nested grids allowed atmospheric flows ranging from the synoptic scale down to the tornadic scale to be represented in the simulation. All convection in the simulation was initiated with resolved vertical motion and subsequent condensation-latent heating from the model microphysics; no warm bubbles or cumulus parameterizations were used. Part I of this study focuses on the simulated storm evolution and its transition into a bow echo. The simulation initially produced a classic supercell that developed at the intersection between a stationary front and an outflow boundary. As the simulation progressed, additional storms developed and interacted with the main storm to produce a single supercell. This storm had many characteristics of an HP supercell and eventually evolved into a bow echo with a rotating comma-head structure. An analysis of the storm's transition into a bow echo revealed that the interaction between convective cells triggered a series of events that played a crucial role in the transition. The simulated storm structure and evolution differed significantly from that of classic supercells produced by idealized simulations. Several vertical vorticity and condensate maxima along the flanking line moved northward and merged into the mesocyclone at the northern end of the convective line during the bow echo transition. Vorticity budget calculations in the mesocyclone showed that vorticity advection from the flanking line into the mesocyclone was the largest positive vorticity tendency term just prior to and during the early phase of the transition in both the low-and midlevel mesocyclone, and remained a significant positive tendency in the midlevel mesocyclone throughout the bow echo transition. This indicates that the flanking line was a source of vertical vorticity for the mesocyclone, and may explain how the mesocyclone was maintained in the HP supercell even though it was completely embedded in heavy precipitation. The simulated supercell also produced two weak tornadoes. The evolution of the simulated tornadoes and an analysis of the tornadogenesis process will be presented in Part II."
"7102969748;7006334009;7006653289;","Circulation of the western Mediterranean: From global to regional scales",1997,"10.1016/S0967-0645(96)00090-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030670558&doi=10.1016%2fS0967-0645%2896%2900090-2&partnerID=40&md5=b0ed8132a225895d3c8006d43b20134d","A free-surface, three-dimensional, primitive equation model has been implemented with a horizontal resolution of 4.6 km to study the ocean circulation in the Gulf of Lions at time scales ranging from weeks to seasons. Numerical experiments have been conducted, in which the regional model is nested into a basin-scale model of the whole western Mediterranean. The global model is operated with a relatively coarse resolution (16 km) and provides boundary conditions at the open-sea boundaries of the regional domain. There is, however, no feedback loop from the regional to the global model. The simulations are consistently driven with atmospheric fluxes computed from the output of the French PERIDOT meteorological forecasting system, between August 1988 and 1989. In addition to the initial conditions, in situ measurements of temperature and salinity are assimilated in the simulation of the general circulation, adopting a simple nudging technique to prevent an excessive drift of the model against climatology. The response of the regional model below and above the thermocline is discussed in the context of the prevailing meteorological situations. Some experiments give indications that a double-gyre system may develop from wind regimes that exhibit a cyclonic/anticyclonic wind stress curl. Advection-diffusion of passive tracers are also examined on the basis of the local hydrodynamic features, because this work has been conceived with the aim of determining the physical conditions in which ecological and biochemical processes develop at the interface between river mouths and the open ocean."
"6602726381;7101811849;","Topographic preconditioning of open-ocean deep convection",1996,"10.1175/1520-0485(1996)026<2196:TPOOOD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030427931&doi=10.1175%2f1520-0485%281996%29026%3c2196%3aTPOOOD%3e2.0.CO%3b2&partnerID=40&md5=d9b602d4c8dd400d17a1f624a2620d09","Evidence for oceanic convection over Maud Rise in the Weddell Sea suggests that bottom topography may select the location and scale of deep convecting oceanic chimneys forced by seasonal large-scale atmospheric cooling. In this paper, the role of bottom topography in open-ocean deep convection is studied using an idealized three-dimensional primitive equation model. A barotropic mean flow impinges on a Gaussian-shaped seamount in a stratified domain generating a Taylor cap (a region of topographically trapped fluid). Uniform surface cooling is applied throughout the domain. When the Taylor cap is tall enough to interact with the surface mixed layer, the local isolation from the advection of heat by the mean flow forms a conduit into the deep water. Convection within this region is significantly enhanced relative to ambient levels away from the seamount and to similar numerical simulations performed without bottom topography. Given uniform background stratification, domed isopycnals are not important in the preconditioning process. However, when a surface intensification in the stratification exists, domed isopycnals associated with the Taylor cap circulation can also play a preconditioning role. In this case, the pycnocline is first ventilated over the seamount, leading to rapid convective deepening into the weakly stratified deep water. An analytic formula for one-dimensional nonpenetrative convection into an exponential stratification profile is derived and compares well with results from the numerical model. Parameter dependencies for these topographic preconditioning mechanisms are discussed. These numerical results suggest that bottom topography can play an important role in selecting the location and horizontal scale of deep convection in the ocean."
"6506144245;56462619700;14018121700;56278375300;15846040700;57191290414;6701847229;57189239011;7003748648;7006033097;57201944742;","Near-global climate simulation at 1km resolution: Establishing a performance baseline on 4888 GPUs with COSMO 5.0",2018,"10.5194/gmd-11-1665-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046540291&doi=10.5194%2fgmd-11-1665-2018&partnerID=40&md5=6033657b91ba66e804d93a3965d1bd4c","The best hope for reducing long-standing global climate model biases is by increasing resolution to the kilometer scale. Here we present results from an ultrahighresolution non-hydrostatic climate model for a near-global setup running on the full Piz Daint supercomputer on 4888 GPUs (graphics processing units). The dynamical core of the model has been completely rewritten using a domainspecific language (DSL) for performance portability across different hardware architectures. Physical parameterizations and diagnostics have been ported using compiler directives. To our knowledge this represents the first complete atmospheric model being run entirely on accelerators on this scale. At a grid spacing of 930m (1.9 km), we achieve a simulation throughput of 0.043 (0.23) simulated years per day and an energy consumption of 596MWh per simulated year. Furthermore, we propose a new memory usage efficiency (MUE) metric that considers how efficiently the memory bandwidth - the dominant bottleneck of climate codes - is being used. © 2018 Copernicus GmbH. All rights reserved."
"54879515900;55924208000;","Benchmark tests for numerical weather forecasts on inexact hardware",2014,"10.1175/MWR-D-14-00110.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907436318&doi=10.1175%2fMWR-D-14-00110.1&partnerID=40&md5=548804c92dc02017921ceb7826b3809f","A reduction of computational cost would allow higher resolution in numerical weather predictions within the same budget for computation. This paper investigates two approaches that promise significant savings in computational cost: the use of reduced precision hardware, which reduces floating point precision beyond the standard double- and single-precision arithmetic, and the use of stochastic processors, which allow hardware faults in a trade-off between reduced precision and savings in power consumption and computing time. Reduced precision is emulated within simulations of a spectral dynamical core of a global atmosphere model and a detailed study of the sensitivity of different parts of the model to inexact hardware is performed. Afterward, benchmark simulations were performed for which as many parts of the model as possible were put onto inexact hardware. Results show that large parts of the model could be integrated with inexact hardware at error rates that are surprisingly high or with reduced precision to only a couple of bits in the significand of floating point numbers. However, the sensitivities to inexact hardware of different parts of the model need to be respected, for example, via scale separation. In the last part of the paper, simulations with a full operational weather forecast model in single precision are presented. It is shown that differences in accuracy between the single- and double-precision forecasts are smaller than differences between ensemble members of the ensemble forecast at the resolution of the standard ensemble forecasting system. The simulations prove that the trade-off between precision and performance is a worthwhile effort, already on existing hardware. © 2014 American Meteorological Society."
"55712426100;36849508000;","Finite-amplitude wave activity and mean flow adjustments in the atmospheric general circulation. Part II: Analysis in the isentropic coordinate",2011,"10.1175/2011JAS3685.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81555201655&doi=10.1175%2f2011JAS3685.1&partnerID=40&md5=06256be9add6ce2844f080300af79d46","The finite-amplitude wave activity diagnostic developed for quasigeostrophic (QG) flows in Part I is extended to the global primitive equation system in the isentropic coordinate. The Rossby wave activity density A is proportional to Kelvin's circulation around the wavy potential vorticity (PV) contour minus that around the zonal circle that encloses the same isentropic mass. A quasi-conservative, eddy-free reference state flow uREF is constructed from the observed Kelvin's circulation by zonalizing the PV contours conservatively while enforcing gradient balance. The departure of the observed zonal-mean flow of the atmosphere from the reference state Δu=u ̄ - uREF is defined as the net adjustment by the eddies. Then Δu is further partitioned into the direct eddy drag -A and the residual impulse ΔuR consistent with the time-integrated transformed Eulerian mean (TEM) zonal-wind equation. The analyzed climatological-mean wave activity in the 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40) is similar to that in Part I. The net adjustment Δu is mainly due to the direct eddy drag (Δu ≈ -A) in the winter polar stratosphere and can reach approximately -60 m s-1 in the Northern Hemisphere. In the extratropical troposphere Du is a small residual (ΔuR ≈ A), yet it clearly reveals a 5-6 m s-1 eddy driving of the Southern Hemisphere jet as well as a 7-8 m s-1 eddy drag in the subtropical upper troposphere of both hemispheres. The local maxima in wave activity in the equatorial upper troposphere and the extratropical lower stratosphere found in Part I are undetected, while negative wave activity is found where the isentropes intersect the ground. As in the QG case, uREF exhibits significantly less transient and interannual variability than ū, implying a better signal-to-noise ratio as a climate variable. © 2011 American Meteorological Society."
"9241987300;7201600456;","Four-dimensional local ensemble transform Kalman filter: Numerical experiments with a global circulation model",2007,"10.1111/j.1600-0870.2007.00255.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548704863&doi=10.1111%2fj.1600-0870.2007.00255.x&partnerID=40&md5=edb6f90f41cb30bfefaa8830e88fc1ac","We present a four-dimensional ensemble Kalman filter (4D-LETKF) that approximately and efficiently solves a variational problem similar to that solved by 4D-VAR, and report numerical results with the Simplified-Parametrized primitive Equation Dynamics model, a simplified global atmospheric model. We discuss the relationship of 4D-LETKF to other ensemble Kalman filters and, in our simulations, compare it with two simpler approaches to assimilating asynchronous observations. We find that 4D-LETKF significantly improves on the approach of treating asynchronous observations as if they occur at the analysis time. For a sufficiently short analysis time interval, the approach of computing innovations from the background state at the observation times and treating those innovations as if they occur at the analysis time is comparable to 4D-LETKF, but for longer analysis intervals, we find that 4D-LETKF is superior to this approach. © 2007 The Authors Journal compilation © 2007 Blackwell Munksgaard."
"55951473800;26642891500;7005961973;","Generalized inversion of a global numerical weather prediction model, II: Analysis and implementation",1997,"10.1007/BF01029698","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031510266&doi=10.1007%2fBF01029698&partnerID=40&md5=893ded282b770397caf3d78d9fe5e12b","This is a sequel to Bennett, Chua and Leslie (1996), concerning weak-constraint, four-dimensional variational assimilation of reprocessed cloud-track wind observations (Velden, 1992) into a global, primitive-equation numerical weather prediction model. The assimilation is performed by solving the Euler-Lagrange equations associated with the variational principle. Bennett et al. (1996) assimilate 2436 scalar wind components into their model over a 24-hour interval, yielding a substantially improved estimate of the state of the atmosphere at the end of the interval. This improvement is still in evidence in forecasts for the next 48 hours. The model and variational equations are nonlinear, but are solved as sequence of linear equations. It is shown here that each linear solution is precisely equivalent to optimal or statistical interpolation using a background error covariance derived from the linearized dynamics, from the forcing error covariance, and from the initial error covariance. Bennett et al. (1996) control small-scale flow divergence using divergence dissipation (Talagrand, 1972). It is shown here that this approach is virtually equivalent to including a penalty, for the gradient of divergence, in the variational principle. The linearized variational equations are solved in terms of the representer functions for the wind observations. Diagonalizing the representer matrix yields rotation vectors. The rotated representers are the ""array modes"" of the entire system of the model, prior covariances and observations. The modes are the ""observable"" degrees of freedom of the atmosphere. Several leading array modes are presented here. Finally, appendices discuss a number of technical implementation issues: time convolutions, convergence in the presence of planetary shear instability, and preconditioning the essential inverse problem."
"7202484739;37860927200;7405606991;57200779562;","Flow over mountains: Coriolis force, transient troughs and three dimensionality",1995,"10.1002/qj.49712152307","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028975178&doi=10.1002%2fqj.49712152307&partnerID=40&md5=cf5896a81546d8d37a42fc03dc2f8125","Some issues, concerning uniform, stratified flow over a three‐dimensional mountain, that have not been fully explored are studied using primitive‐equation models. When the Froude number (Fr) is small (e.g. Fr < 0.5), we find that the Coriolis force cannot be neglected for flow over small‐scale mountains (characteristic length L < 50 km) even though the Rossby number (Ro) is large. When the Coriolis force is neglected, a pair of symmetric vortices is induced on the lee side, irrespective of the scale of the mountain, as long as Fr lies roughly between 0.1 and 0.5. The major effect of the Coriolis force is to modify or diminish the lee vortices due to the leftward deflection on the upstream side of the mountain. The Coriolis deflection also reduces the upstream propagation. When Fr is ≥ 1, most of the flow goes over the mountain and the Coriolis effect is small for the same Ro. Therefore, the importance of the Coriolis effect is determined by both Ro and Fr. As the scale of the mountain increases from small‐scale to mesoscale (100 km < L < 300 km), the upstream flow is deflected more to the left by the Coriolis effect, and a trough develops on the lee side. The length‐scale of the trough depends on the scale of the mountain in the along‐flow direction. For smaller‐scale mountains, small vortices can be generated within the lee‐side trough when Fr is small. When the mountain scale is increased, the lee‐side vortices disappear, and only a lee‐side trough remains. Depending on the mean wind speed and the mountain scale, the lee‐side trough can be advected by the anticyclonic flow over the mountain to the south, and remain attached to the mountain for a long time. A train of troughs is generated on the lee side of an elliptic mountain associated with the lee‐side gravity waves. Simulations of flows over mountains in two‐dimensional and three‐dimensional models with the same cross‐sectional profile are compared. For small‐scale mountains (L < 100km), the two‐dimensional model overestimates the amount of airflow over the mountain and also the lee‐side downslope wind. Copyright © 1995 Royal Meteorological Society"
"6507767109;24789201300;","A numerical world ocean general circulation model",1989,"10.1007/BF02656917","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51249171867&doi=10.1007%2fBF02656917&partnerID=40&md5=96712fa28513bdf9451017066994bd28","This paper describes a numerical model of the world ocean based on the fully primitive equations. A ""Standard"" ocean state is introduced into the equations of the model and the perturbed thermodynamic variables are used in the modle's calculations. Both a free upper surface and a bottom topography are included in the model and a sigma coordinate is used to normalize the model's vertical component. The model has four unevenly-spaced layers and 4 x 5 horizontal resolution based on C-grid system. The finite-difference scheme of the model is designed to conserve the gross available energy in order to avoid fictitious energy generation or decay. The model has been tested in response to the annual mean surface wind stress, sea level air pressure and sea level air temperature as a preliminary step to its further improvement and its coupling with a global atmospheric general circulation model. Some of results, including currents, temperature and sea surface elevation simulated by the model are presented. © 1989 Advances in Atmospheric Sciences."
"7005454026;7402828823;57217587785;","A technique for representing three-dimensional vertical circulations in baroclinic disturbances",1989,"10.1175/1520-0493(1989)117<2463:ATFRTD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024857046&doi=10.1175%2f1520-0493%281989%29117%3c2463%3aATFRTD%3e2.0.CO%3b2&partnerID=40&md5=2407e816e6674dc83d6681c77d763098","The proposed methodology, which builds upon the earlier work of Hoskins and Draghici and of Eliassen, consists of adopting a vector streamfunction that describes the vertical velocity and the horizontal irrotational flow. This generalized streamfunction, referred to as the psi vector, may be determined uniquely from the vertical velocity field over a limited region provided that suitable lateral boundary conditions on the velocity potential for the irrotational part of the horizontal velocity can be specified. A key property of the psi vector is that its projections onto arbitrary orthogonal vertical planes yield two independent vertical circulations. The psi vector methodology is applied to surface and upper-level frontal zones simulated in an f-plane primitive equation channel model of a finite-amplitude baroclinic wave in which all diabatic and frictional influences are neglected except for horizontal diffusion. -from Authors"
"56245470700;","The behavior of winter stationary planetary waves forced by topography and diabatic heating.",1982,"10.1175/1520-0469(1982)039<1206:TBOWSP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020143171&doi=10.1175%2f1520-0469%281982%29039%3c1206%3aTBOWSP%3e2.0.CO%3b2&partnerID=40&md5=a7e959154d49e2abb98e9ade068afcf3","A primitive equation linear wave model is developed to examine the effects of mean zonal wind structure on the vertical propagation of stationary planetary waves and to identify the characteristics of the winter stationary waves forced by realistic topography and diabatic heating. An analytic mean zonal wind model is used to facilitate changing the wind structure parameters for comparative experiments. A more realistic mean wind profile is used to simulate the observed behavior of stationary waves more closely. -from Author"
"6506756436;8255473900;","How does subgrid-scale parametrization influence nonlinear spectral energy fluxes in global NWP models?",2016,"10.1002/2015JD023970","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029382188&doi=10.1002%2f2015JD023970&partnerID=40&md5=aa02efe5eb4696cf716df3f1aadec896","The paper examines horizontal wind variance (kinetic energy spectra) and available potential energy spectra in simulations conducted with a state-of-the-art global numerical weather prediction (NWP) model: the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts. The formulation of the spectral energy budget of the atmosphere by Augier and Lindborg (2013) is used to illustrate how the nonlinear spectral fluxes differ for a hierarchy of reduced models, adiabatic dynamical core, Held-Suarez dry, and idealized moist aquaplanet simulations, compared to NWP simulations with full complexity. The results identify surface drag and momentum vertical mixing as the key processes for influencing the transfer of energy in a stratified atmosphere. Moreover, the circulation generated by topography plays a significant role in these transfers. Given that subgrid-scale vertical mixing is parametrized, and that the treatment of orography filtering varies vastly between NWP models, the magnitude and scale of the nonlinear interactions can differ substantially from model to model, and depends on the choices made for the physical parametrizations. The need to appropriately parametrize the essential influence of subgrid-scale processes in global NWP and climate simulations has the effect that the physical energy cascade is replaced by a parametrized energy transfer. This explains the seeming failure of the IFS to produce a shallower mesoscale energy spectrum. In contrast, neither the horizontal filtering, typically applied in NWP models to avoid a spectral blocking at the smallest scales, nor implicit numerical dissipation significantly constrain, at sufficiently high resolution, the nonlinear interactions or the dominant slope of the energy spectra at synoptic and mesoscales. © 2016. American Geophysical Union."
"15848674200;24492014600;56520921400;57210180554;6602858513;7406243250;6506328135;7202048112;","Observed scaling in clouds and precipitation and scale incognizance in regional to global atmospheric models",2013,"10.1175/JCLI-D-13-00005.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888064298&doi=10.1175%2fJCLI-D-13-00005.1&partnerID=40&md5=267fb0b4675b5eae6c326e7a6c526db2","Observations of robust scaling behavior in clouds and precipitation are used to derive constraints on how partitioning of precipitation should change with model resolution. Analysis indicates that 90%-99% of stratiform precipitation should occur in clouds that are resolvable by contemporary climate models (e.g., with 200-km or finer grid spacing). Furthermore, this resolved fraction of stratiform precipitation should increase sharply with resolution, such that effectively all stratiform precipitation should be resolvable above scales of ~50 km. It is shown that the Community Atmosphere Model (CAM) and the Weather Research and Forecasting model (WRF) also exhibit the robust cloud and precipitation scaling behavior that is present in observations, yet the resolved fraction of stratiform precipitation actually decreases with increasing model resolution. A suite of experiments with multiple dynamical cores provides strong evidence that this ""scale-incognizant"" behavior originates in one of the CAM4 parameterizations. An additional set of sensitivity experiments rules out both convection parameterizations, and by a process of elimination these results implicate the stratiform cloud and precipitation parameterization. Tests with the CAM5 physics package show improvements in the resolution dependence of resolved cloud fraction and resolved stratiform precipitation fraction. © 2013 American Meteorological Society."
"35213726000;57203049177;6603236154;57203479688;","Climate entropy budget of the HadCM3 atmosphere-ocean general circulation model and of FAMOUS, its low-resolution version",2011,"10.1007/s00382-009-0718-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78649516115&doi=10.1007%2fs00382-009-0718-1&partnerID=40&md5=a0dd7424de76ef84855320477f9b3b7a","The entropy budget is calculated of the coupled atmosphere-ocean general circulation model HadCM3. Estimates of the different entropy sources and sinks of the climate system are obtained directly from the diabatic heating terms, and an approximate estimate of the planetary entropy production is also provided. The rate of material entropy production of the climate system is found to be ~50 mW m-2 K-1, a value intermediate in the range 30-70 mW m-2 K-1 previously reported from different models. The largest part of this is due to sensible and latent heat transport (~38 mW m-2 K-1). Another 13 mW m-2 K-1 is due to dissipation of kinetic energy in the atmosphere by friction and Reynolds stresses. Numerical entropy production in the atmosphere dynamical core is found to be about 0.7 mW m-2 K-1. The material entropy production within the ocean due to turbulent mixing is ~1 mW m-2 K-1, a very small contribution to the material entropy production of the climate system. The rate of change of entropy of the model climate system is about 1 mW m-2 K-1 or less, which is comparable with the typical size of the fluctuations of the entropy sources due to interannual variability, and a more accurate closure of the budget than achieved by previous analyses. Results are similar for FAMOUS, which has a lower spatial resolution but similar formulation to HadCM3, while more substantial differences are found with respect to other models, suggesting that the formulation of the model has an important influence on the climate entropy budget. Since this is the first diagnosis of the entropy budget in a climate model of the type and complexity used for projection of twenty-first century climate change, it would be valuable if similar analyses were carried out for other such models. © 2009 Springer-Verlag."
"16432829300;7004418377;8285351400;7003798680;","Dynamics of wind-forced coherent anticyclones in the open ocean",2009,"10.1029/2009JC005388.","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73949095453&doi=10.1029%2f2009JC005388.&partnerID=40&md5=02cf5490c70d1ed376eeec5b85bb9765","[1] We numerically study the dynamics of coherent anticyclonic eddies in the ocean interior. For the hydrostatic, rotating, stably stratified turbulence we use a high-resolution primitive equation model forced by small-scale winds in an idealized configuration. Many properties of the horizontal motions are found to be similar to those of two-dimensional and quasi-geostrophic turbulence. Major differences are a strong cyclone-anticyclone asymmetry linked to the straining field exerted by vortex Rossby waves, which is also found in shallow water flows, and the complex structure of the vertical velocity field, which we analyze in detail. Locally, the motion can become strongly ageostrophic, and vertical velocities associated with vortices can reach magnitudes and levels of spatial complexity akin to those reported for frontal regions. Transport and mixing properties of the flow field are further investigated by analyzing Lagrangian trajectories. Particles released in the pycnocline undergo large vertical excursions because of the vertical velocities associated to the vortices, with potentially important consequences for marine ecosystem dynamics. Copyright 2009 by the American Geophysical Union."
"13404352400;7005500582;7006263720;7404678955;","Representation of Northern Hemisphere winter storm tracks in climate models",2007,"10.1007/s00382-006-0205-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247604918&doi=10.1007%2fs00382-006-0205-x&partnerID=40&md5=83a1814a8014af965204c2d44803caef","Northern Hemisphere winter storm tracks are a key element of the winter weather and climate at mid-latitudes. Before projections of climate change are made for these regions, it is necessary to be sure that climate models are able to reproduce the main features of observed storm tracks. The simulated storm tracks are assessed for a variety of Hadley Centre models and are shown to be well modelled on the whole. The atmosphere-only model with the semi-Lagrangian dynamical core produces generally more realistic storm tracks than the model with the Eulerian dynamical core, provided the horizontal resolution is high enough. The two models respond in different ways to changes in horizontal resolution: the model with the semi-Lagrangian dynamical core has much reduced frequency and strength of cyclonic features at lower resolution due to reduced transient eddy kinetic energy. The model with Eulerian dynamical core displays much smaller changes in frequency and strength of features with changes in horizontal resolution, but the location of the storm tracks as well as secondary development are sensitive to resolution. Coupling the atmosphere-only model (with semi-Lagrangian dynamical core) to an ocean model seems to affect the storm tracks largely via errors in the tropical representation. For instance a cold SST bias in the Pacific and a lack of ENSO variability lead to large changes in the Pacific storm track. Extratropical SST biases appear to have a more localised effect on the storm tracks. © British Crown Copyright 2006."
"8629728200;6701676992;","ITCZ breakdown in three-dimensional flows",2005,"10.1175/JAS3409.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-20444480126&doi=10.1175%2fJAS3409.1&partnerID=40&md5=8c3188de862b21ecb24c40d3c963af88","The intertropical convergence zone (ITCZ) is observed to undulate and at times break down into a series of tropical disturbances in several days. Some of these disturbances may develop into tropical cyclones and move to higher latitudes, while others dissipate, and the ITCZ may reform in the original region. It has been proposed that the ITCZ may break down because of its heating-induced potential vorticity (PV) anomalies. Here this process is examined in three-dimensional simulations using a primitive equation model. A simulation of the ITCZ in a background state of rest is compared to simulations in different background flows. The effect of different vertical structures of the prescribed heating is also examined. Deep heating induces a positive PV anomaly in the lower troposphere, leading to a reversal of the PV gradient on the poleward side of the heating, while the induced PV anomaly at upper levels is negative, leading to a reversal of the PV gradient on the equatorward side of the heating. The response at upper levels leads to a weaker PV gradient change, but the response is greater in areal extent than the lower-tropospheric response. For shallow heating, the lower-tropospheric PV response is greater than that for deep heating, and there is no upper-tropospheric PV response. The ITCZ lasts longer before breaking in this case than in the deep heating case. Effects of the background flow are mainly felt in the deep heating cases. When the background flow enforces the PV-induced wind field, ITCZ breakdown occurs more rapidly, whereas when the background flow is opposite to the PV-induced flow, ITCZ breakdown takes longer and the ITCZ may dissipate before breakdown. © 2005 American Meteorological Society."
"6701726931;7006629146;","Baroclinic wave breaking and the internal variability of the tropospheric circulation",1999,"10.1175/1520-0469(1999)056<4014:BWBATI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033390389&doi=10.1175%2f1520-0469%281999%29056%3c4014%3aBWBATI%3e2.0.CO%3b2&partnerID=40&md5=d4ce2361228a9798987cdc5232dcc15f","A simple model of the tropospheric circulation, based on a 10-level primitive equation model, is forced by linearly relaxing the potential temperature toward an idealized, zonally symmetric equilibrium field. The model equations are integrated in time until a statistically steady state is obtained. The local relationship between the state of the background flow, the direction of wave propagation, and subsequent wave breaking at the tropopause level is then investigated. Maps of potential vorticity (PV) on isentropic surfaces are analyzed and all four different types of wave breaking described recently by Peters and Waugh are shown to occur. It is found that cyclonic wave breaking events are usually initiated by poleward fluxes of wave activity, and anticyclonic events by equatorward fluxes. Composites are then used to show that equatorward fluxes are associated with a jet that is locally broad and weak, with relatively strong isentropic PV gradients to its equatorward flank. By contrast, poleward fluxes are associated with a narrow, strong jet, with very weak or even negative PV gradients on its equatorward side. It is argued that this result is consistent with nonlinear critical-layer theory, as under certain conditions an isolated region of homogenized potential vorticity must remain a perfect reflector of wave activity for all time. The variability exhibited by the zonal flow field is then investigated using a cross-sectional EOF method. The first EOF is found to have similar structure in the latitude-height plane to the baroclinic waves themselves, and describes much of the variability associated with them. The second EOF has structure that corresponds to a sharp, narrow jet in its positive phase and a weak, broad jet in its negative phase. Its phase is shown to be well correlated with the wave activity flux index, with the maximum occurring at a space and time lag, with the phase of the EOF preceding the index. Most of the variability associated with this EOF occurs on the scale of zonal wavenumbers 2-4, suggesting that the direction of meridional propagation of the baroclinic waves is determined locally. Strikingly, the phase of the second EOF propagates in a wavelike manner, with wavenumber and period (≈11-14 days) quite distinct from those of the baroclinic waves. Individual phase maxima of these long waves can persist for up to ≈20-25 days, as they do not decay rapidly due to downstream radiation.A simple model of the tropospheric circulation, based on a 10-level primitive equation model, is forced by linearly relaxing the potential temperature toward an idealized, zonally symmetric equilibrium field. The model equations are integrated in time until a statistically steady state is obtained. The local relationship between the state of the background flow, the direction of wave propagation, and subsequent wave breaking at the tropopause level is then investigated. Maps of potential vorticity (PV) on isentropic surfaces are analyzed and all four different types of wave breaking described recently by Peters and Waugh are shown to occur. It is found that cyclonic wave breaking events are usually initiated by poleward fluxes of wave activity, and anticyclonic events by equatorward fluxes. Composites are then used to show that equatorward fluxes are associated with a jet that is locally broad and weak, with relatively strong isentropic PV gradients to its equatorward flank. By contrast, poleward fluxes are associated with a narrow, strong jet, with very weak or even negative PV gradients on its equatorward side. It is argued that this result is consistent with nonlinear critical-layer theory, as under certain conditions an isolated region of homogenized potential vorticity must remain a perfect reflector of wave activity for all time. The variability exhibited by the zonal flow field is then investigated using a cross-sectional EOF method. The first EOF is found to have similar structure in the latitude-height plane to the baroclinic waves themselves, and describes much of the variability associated with them. The second EOF has structure that corresponds to a sharp, narrow jet in its positive phase and a weak, broad jet in its negative phase. Its phase is shown to be well correlated with the wave activity flux index, with the maximum occurring at a space and time lag, with the phase of the EOF preceding the index. Most of the variability associated with this EOF occurs on the scale of zonal wavenumbers 2-4, suggesting that the direction of meridional propagation of the baroclinic waves is determined locally. Strikingly, the phase of the second EOF propagates in a wavelike manner, with wavenumber and period (~11-14 days) quite distinct from those of the baroclinic waves. Individual phase maxima of these long waves can persist for up to ~20-25 days, as they do not decay rapidly due to downstream radiation."
"55046667600;7102202012;","A simple model of nonlinear hadley circulation with an ITCZ: Analytic and numerical solutions",1996,"10.1175/1520-0469(1996)053<1241:ASMONH>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030452193&doi=10.1175%2f1520-0469%281996%29053%3c1241%3aASMONH%3e2.0.CO%3b2&partnerID=40&md5=d14291873b8d38571fd4ed7f0543cc55","Simple analytic solutions are constructed for an axially symmetric, nonlinear, slightly viscous circulation in a Boussinesq atmosphere in the presence of intense convection at an inlertropical convergence zone. The latitude-height extent of the Hadley circulation is obtained, as well as its streamfunetion. zonal wind, and temperature distribution. Numerical solutions of the viscous primitive equations are also obtained to verily the analytic solutions. The strength of the circulation is stronger than previous results based on dry models and is now close to the observed value. The extent of the Hadley region is also quite realistic."
"7003545639;7202145115;","Stationary waves on a sphere: sensitivity to thermal feedback.",1982,"10.1175/1520-0469(1982)039<1906:SWOASS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020330442&doi=10.1175%2f1520-0469%281982%29039%3c1906%3aSWOASS%3e2.0.CO%3b2&partnerID=40&md5=2a38db7f86387d0f33a99b1c8f4eb189","Thermal forcing feedback is proposed to be an important mechanism in middle and high latitudes in determining the low-frequency variability of the stationary wave structure. The total diabatic heating in the atmosphere is not due solely to the fixed longitudinally varying heat sources but also depends on the flow field itself. As a first approximation to this complex process, a heat flux which is proportional to the low-level temperature of the atmosphere is incorporated into a multi-level, steady-state, linear primitive equation model on a sphere. -from Authors"
"57196195795;7004247643;","More frequent sudden stratospheric warming events due to enhanced MJO forcing expected in a warmer climate",2017,"10.1175/JCLI-D-17-0044.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032199604&doi=10.1175%2fJCLI-D-17-0044.1&partnerID=40&md5=a7c8431f173d124cd56b800657269a79","Sudden stratospheric warming (SSW) events influence the Arctic Oscillation and midlatitude extreme weather. Observations show SSW events to be correlated with certain phases of the Madden-Julian oscillation (MJO), but the effect of the MJO on SSW frequency is unknown, and the teleconnection mechanism, its planetary wave propagation path, and time scale are still not completely understood. The Arctic stratosphere response to increased MJO forcing expected in a warmer climate using two models is studied: the comprehensive Whole Atmosphere Community Climate Model and an idealized dry dynamical core with and without MJO-like forcing. It is shown that the frequency of SSW events increases significantly in response to stronger MJO forcing, also affecting the averaged polar cap temperature. Two teleconnection mechanisms are identified: a direct propagation of MJO-forced transient waves to the Arctic stratosphere and a nonlinear enhancement of stationary waves by the MJO-forced transient waves. The MJO-forced waves propagate poleward in the lower stratosphere and upper troposphere and then upward. The cleaner results of the idealized model allow identifying the propagating signal and suggest a horizontal propagation time scale of 10-20 days, followed by additional time for upward propagation within the Arctic stratosphere, although there are significant uncertainties involved. Given that the MJO is predicted to be stronger in a warmer climate, these results suggest that SSW events may become more frequent, with possible implications on tropospheric high-latitude weather. However, the effect of an actual warming scenario on SSW frequency involves additional effects besides a strengthening of the MJO, requiring further investigation. © 2017 American Meteorological Society."
"15768631100;6701574871;11939306500;57207510696;15769936500;","Flux-conservative thermodynamic equations in a mass-weighted framework",2007,"10.1111/j.1600-0870.2006.00212.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846284122&doi=10.1111%2fj.1600-0870.2006.00212.x&partnerID=40&md5=ff7c17d60987637fb4a89fd98f559628","A set of equations, ready for discretization, is presented for the purely thermodynamic part of atmospheric energetics along a vertical column. Considerations of kinetic energy budgets and detailed turbulence laws are left for further study. The equations are derived in a total mass-based framework, both for the vertical coordinate system and for the conservation laws. This results in the use of the full barycentric velocity as the vector of advection. Under these conditions, the equations are derived from first principles on the basis of an a priori defined set of simplifying hypotheses. The originality of the resulting set of equations is twofold. First, even in the presence of a full prognostic treatment of cloud and precipitation processes, there exists a flux-conservative form for all relevant budgets, including that of the thermodynamic equation. Secondly, the form of the state law that is obtained for the multiphase system allows the flux-conservative form to be kept when going from the hydrostatic primitive equations system to the fully compressible system and projecting then the heat source/sink on both temperature and pressure tendencies. © 2006 The Authors Journal compilation © 2006 Blackwell Munksgaard."
"7004247643;","Proximity of the present-day thermohaline circulation to an instability threshold",2000,"10.1175/1520-0485(2000)030<0090:POTPDT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033994746&doi=10.1175%2f1520-0485%282000%29030%3c0090%3aPOTPDT%3e2.0.CO%3b2&partnerID=40&md5=2ac9dd6fb427723a389a14a90913dae4","The relation between the mean state of the thermohaline circulation (THC) and its stability is examined using a realistic-geometry primitive equation coupled ocean-atmosphere-ice global general circulation model. The main finding is that a thermohaline circulation that is 25% weaker and less dominated by thermal forcing than that of today's ocean is unstable within this coupled GCM. Unstable initial ocean climates lead in the coupled model to an increase of the THC, to strong oscillations, or to a THC collapse. The existence of an unstable range of weak states of the THC provides a natural explanation for large-amplitude THC variability seen in the paleo record prior to the past 10 000 years: A weakening of the THC due to an external forcing (e.g., ice melting and freshening of the North Atlantic) may push it into the unstable regime. Once in this regime, the THC strongly oscillates due to the inherent instability of a weak THC. Hence the strong THC variability in this scenario does not result from switches between two or more quasi-stable steady states."
"7101829066;7101910089;","Indonesian throughflow in a coupled general circulation model",1997,"10.1029/97JC00022","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030683994&doi=10.1029%2f97JC00022&partnerID=40&md5=497c06dab1b8fc90e0c30191525cc20a","The Indonesian throughflow is analyzed in an extended simulation with a coupled ocean-atmosphere model. The model, developed by the Max-Planck-Institut für Meteorologie, Hamburg, Germany, combines an atmospheric general circulation model at T42 resolution (2.8° latitude by 2.8° longitude) and a primitive equation ocean model with zonal resolution of 2.8° and a meridional resolution of 0.5° in the tropics and is coupled without flux correction equatorward of a latitude of 60°. The onset and strength of the monsoon in the Indonesian waters agree well with climatology, and many aspects of the observed temperature fields in the eastern Indian Ocean and Timor Seas are found in simulation. Differences between simulation and observations of temperature occur in mean and seasonal cycles in the far western Pacific. The annual cycles of sea level along the coast of Sumatra and Java are simulated satisfactorily. The simulated throughflow transports on average 13.8 Sv (106m3s-1) from the Pacific to the Indian Ocean. The vertically averaged (barotropic) component of the throughflow has a seasonal range of 13.1 Sv and is weakest in February and strongest in July. In contrast, deviations from the vertical average of the throughflow (baroclinic) are strongest in March and September. The average and seasonal cycle of the barotropic component of the throughflow are forced by winds over the Pacific and along the western coasts of Australia and South America, as described by the island rule. For closed Torres Strait, the contribution of the average bottom pressure torque is small, and friction closes the vorticity balance. For annual timescales, baroclinic flows affect the throughflow transport through the bottom pressure torque. The annual cycle of the baroclinic component of the throughflow is forced predominantly by winds over the Indonesian Seas. The throughflow exports 0.9 PW of heat from the Pacific into the Indian Ocean and is an important heat sink for the western Pacific. The throughflow is a major heat source for the Indian Ocean and is associated witìi reversal of the divergence of the meridional transport of heat south of 10°S that is balanced by heat fluxes from the ocean to the atmosphere. Copyright 1997 by the American Geophysical Union."
"7003266240;7006560435;","The influence of wind stress, temperature, and humidity gradients on evaporation from reservoirs",1997,"10.1029/97WR02405","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030656263&doi=10.1029%2f97WR02405&partnerID=40&md5=d3fa0bd6c1e981c728acf224808ff631","Evaporation from fetch-limited water bodies has been investigated for the first time using a coupled atmospheric boundary layer-water body model. The model incorporates a simplified atmospheric boundary layer in which heat and moisture are advected horizontally and diffused vertically. The wind field evolves over the water body through the formation of an internal boundary layer, which is initiated by the change in roughness from the land to the water surface. The wind also responds to local stability through the inclusion of Monin-Obukhov similarity functions. This system is coupled to a dynamically active water body based on primitive equations with full thermodynamics. This is achieved through continuity of stress and heat flux through the air-water interface. The model results reveal that along-wind gradients in wind stress, humidity, and temperature can all significantly influence evaporation. The most important effects are growing wind stress and increasing humidity as we move downwind across the water body. However, there is a tendency for these effects to cancel, so that the behavior can range from areally averaged evaporation weakly decreasing with fetch for very smooth land surfaces to weakly increasing with fetch for relatively rough land terrain. For most situations of interest, such as typical agricultural settings, evaporation is essentially independent of fetch. All the model results have been summarized in a simple empirical expression for evaporation based exclusively on meteorological data from over the upwind land surface. This is in good agreement with detailed measurements from a small lake in southeastern Australia."
"57203558683;7005052420;7005449794;","A stochastic linear theory of mesoscale circulation induced by the thermal heterogeneity of the land surface",1996,"10.1175/1520-0469(1996)053<3349:ASLTOM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030419571&doi=10.1175%2f1520-0469%281996%29053%3c3349%3aASLTOM%3e2.0.CO%3b2&partnerID=40&md5=f538550cfc3bb2b13bde501ca79a0c8b","This paper presents a three-dimensional stochastic linear model of the mesoscale circulation induced by the variability of turbulent sensible heat flux over land surface. The primitive equations relating wind field, geopotential, and potential temperature are formulated as a system of stochastic partial differential equations and solved analytically. The solution is based on spectral representations of homogeneous random fields. The flow intensity is found to be proportional to the standard deviation of the turbulent sensible heat flux into the atmosphere. Large (small) scales of spatial variability in the surface heating preferably impact circulations at high (low) altitudes. The mesoscale fluxes associated with the atmospheric flow are related to explicit functions of atmospheric stability, variance of turbulent heat flux, and synoptic wind. The authors find that the vertical momentum flux is significant in the presence of synoptic wind and that the flow perpendicular to the direction of the synoptic wind is responsible for this momentum flux. The proposed linear theory identifies the synoptic conditions under which the land-surface heterogeneity may play a role in atmospheric circulations at the mesoscale."
"7003639093;6602662282;6506634774;6602678456;","Sea response to atmospheric variability. Model study for the Black Sea",1995,"10.1016/0924-7963(94)00026-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028792954&doi=10.1016%2f0924-7963%2894%2900026-8&partnerID=40&md5=00a25e1c4d22be77cc85837f61e849f0","A general circulation model for the Black Sea, based on the Bryan and Cox primitive equation model, is used to study the sea's response to atmospheric variability. The forcing is based on well-known bulk-formulas, model simulated sea surface temperatures and on atmospheric analysis data for temperature, relative humidity and winds. The climatology of the forcing and the model response are analyzed in different frequency ranges. Model data give strong indications that interannual variability can be easily traced in the behavior of the modelled averaged characteristics, particularly in the core of the intermediate layer, which is extremely sensitive to convection. Experiments with smoothed and non-smoothed atmospheric data show that short-period atmospheric variability, related to the atmospheric cyclones, is of paramount significance not only for the ocean convection, which has relatively short time scales, but also for some permanent and very important climatic characteristics, such as the water masses. © 1995."
"7003659713;7405924003;7003739244;","Initialization and data assimilation experiments with a primitive equation model",1989,"10.1016/0377-0265(89)90046-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001303532&doi=10.1016%2f0377-0265%2889%2990046-8&partnerID=40&md5=339b05227366cfba92f8275b9e65adc2","The process of combining models of the ocean circulation with large data sets is known in meteorology as model initialization and data assimilation. This process is new to oceanographers, who only now are on the verge of having available world-wide synoptic maps of dynamic variables. In this paper we carry out a series of idealized initialization/assimilation experiments with a primitive equation (PE) model, which constitute a first step in developing a realistic process model and data assimilation techniques for the Gulf Stream system. The PE model is used in a spin-down mode and initialized with an analytic jet profile with geostrophically balanced fields. Two major questions are addressed in the present study. The first concerns the initialization process of a PE model during which internal/inertial gravity wave noise is produced. We ask: are the initialization shocks equally crucial for ocean models as they have been for their atmospheric counterparts? The results of an extensive series of balanced versus unbalanced initializations indicate that, for a PE model with a rigid lid, a brutally unbalanced initialization is required to produce strong internal gravity wave shocks. A geostrophically balanced initialization is sufficient to ensure smooth jet evolutions, with no apparent gravity waves, over long time durations in the spin-down mode. No sophisticated initialization procedures seem, therefore, to be required. The second question addressed is: which component of the flow is the most important in data assimilation to drive the model response towards a baseline reference ocean? We specifically compare the knowledge of the depth-integrated flow only, corresponding to measurements of the total transport, with the knowledge of the density field only, or equivalently the velocity shear. The knowledge of the interior density field is much more effective in decreasing the root-mean-square (r.m.s.) errors relative to the reference ocean. If the baroclinic structure is known, coarse horizontal resolutions of data insertion can be reached before significantly worsening the model estimates. If only the depth-averaged flow is known, a decrease in the horizontal resolution of data assimilation has an immediate effect: the r.m.s. errors sharply increase and the assimilation run diverges from the reference ocean. In the assimilation of the barotropic flow alone, even with dense resolution, the errors in the deep layers always show an increasing trend. The relative effectiveness of baroclinic versus barotropic data insertion can be rationalized in the context of geostrophic adjustment theory. © 1989."
"57190237768;57190238325;","A 10‐level atmospheric model and frontal rain",1967,"10.1002/qj.49709339502","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978574273&doi=10.1002%2fqj.49709339502&partnerID=40&md5=e02348adf3a9b43ad1dbce52ace3c1d1","A 10‐level primitive equation model suitable for studying the dynamics of fronts and frontal rainfall is described. The atmosphere is assumed to be hydrostatic and inviscid and the effects of friction and topography are ignored. Latent heat due to evaporation and condensation is incorporated in the thermodynamic equation. No distinction is made between the ice and water stage and the atmosphere is assumed to be dry above 300 mb. The horizontal grid length is 40 km. The results of one 24‐hr integration are described in detail. Copyright © 1967 Royal Meteorological Society"
"36998033800;8558370300;36102803900;7201746369;","A Rossby wave bridge from the tropical Atlantic to West Antarctica",2015,"10.1175/JCLI-D-14-00450.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84961291446&doi=10.1175%2fJCLI-D-14-00450.1&partnerID=40&md5=24888f8782c2a129a3ade4ab47377723","Tropical Atlantic sea surface temperature changes have recently been linked to circulation anomalies around Antarctica during austral winter. Warming in the tropical Atlantic associated with the Atlantic multidecadal oscillation forces a positive response in the southern annular mode, strengthening the Amundsen- Bellingshausen Sea low in particular. In this study, observational and reanalysis datasets and a hierarchy of atmospheric models are used to assess the seasonality and dynamical mechanism of this teleconnection. Both the reanalyses and models reveal a robust link between tropical Atlantic SSTs and the Amundsen- Bellingshausen Sea low in all seasons except austral summer. A Rossby wave mechanism is then shown to both explain the teleconnection and its seasonality. Themechanisminvolves both changes in the excitation ofRossby wave activitywith season and the formation of aRossbywaveguide across the Pacific,which depends critically on the strength and extension of the subtropical jet over the west Pacific. Strong anticyclonic curvature on the poleward flank of the jet creates a reflecting surface, channeling quasi-stationary Rossby waves from the subtropical Atlantic to the Amundsen-Bellingshausen Sea region. In summer, however, the jet is weaker than in other seasons and no longer able to keep Rossby wave activity trapped in the Southern Hemisphere. The mechanism is supported by integrations with a comprehensive atmospheric model, initial-value calculations with a primitive equation model on the sphere, and Rossby wave ray tracing analysis. © 2015 American Meteorological Society."
"36179077700;15765007300;56900961900;7406243250;","Effects of localized grid refinement on the general circulation and climatology in the community atmosphere model",2015,"10.1175/JCLI-D-14-00599.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944088518&doi=10.1175%2fJCLI-D-14-00599.1&partnerID=40&md5=9c453b2ad6c8787ce41d8d0473a9552d","Using the spectral element (SE) dynamical core within the National Center for Atmospheric Research-Department of Energy Community Atmosphere Model (CAM), a regionally refined nest at 0.25° (~28 km) horizontal resolution located over the North Atlantic is embedded within a global 1° (~111 km) grid. A 23-yr simulation using Atmospheric Model Intercomparison Project (AMIP) protocols and default CAM, version 5, physics is compared to an identically forced run using the global 1° (~111 km) grid without refinement. The addition of a refined patch over the Atlantic basin does not noticeably affect the global circulation. In the area where the refinement is located, large-scale precipitation increases with the higher resolution. This increase is partly offset by a decrease in precipitation resulting from convective parameterizations, although total precipitation is also slightly higher at finer resolutions. Equatorial waves are not significantly impacted when traversing multiple grid spacings. Despite the grid transition region bisecting northern Africa, local zonal jets and African easterly wave activity are highly similar in both simulations. The frequency of extreme precipitation events increases with resolution, although this increase is restricted to the refined patch. Topography is better resolved in the nest as a result of finer grid spacing. The spatial patterns of variables with strong orographic forcing (such as precipitation, cloud, and precipitable water) are improved with local refinement. Additionally, dynamical features, such as wind patterns, associated with steep terrain are improved in the variable-resolution simulation when compared to the uniform coarser run. © 2015 American Meteorological Society."
"36992744000;6701431208;6508089485;55388694300;25921086700;13406399300;7801492228;36876405100;","Impact of the dynamical core on the direct simulation of tropical cyclones in a high-resolution global model",2015,"10.1002/2015GL063974","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84930486393&doi=10.1002%2f2015GL063974&partnerID=40&md5=3f698a19544001dce5278a81776c1704","This paper examines the impact of the dynamical core on the simulation of tropical cyclone (TC) frequency, distribution, and intensity. The dynamical core, the central fluid flow component of any general circulation model (GCM), is often overlooked in the analysis of a model's ability to simulate TCs compared to the impact of more commonly documented components (e.g., physical parameterizations). The Community Atmosphere Model version 5 is configured with multiple dynamics packages. This analysis demonstrates that the dynamical core has a significant impact on storm intensity and frequency, even in the presence of similar large-scale environments. In particular, the spectral element core produces stronger TCs and more hurricanes than the finite-volume core using very similar parameterization packages despite the latter having a slightly more favorable TC environment. The results suggest that more detailed investigations into the impact of the GCM dynamical core on TC climatology are needed to fully understand these uncertainties. Key Points The impact of the GCM dynamical core is often overlooked in TC assessments The CAM5 dynamical core has a significant impact on TC frequency and intensity A larger effort is needed to better understand this uncertainty ©2015. American Geophysical Union. All Rights Reserved."
"7006566972;6603833747;8081071000;6506776792;7403326970;9244665700;20435596200;35408443800;7004018029;6603139735;","Modeling of upwelling/relaxation events with the Navy Coastal Ocean Model",2007,"10.1029/2006JC003946","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548363503&doi=10.1029%2f2006JC003946&partnerID=40&md5=2031821e92d9c902cb2e4c83e3ab80fe","The Navy Coastal Ocean Model (NCOM) is a free-surface, primitive-equation model that is under development at the Naval Research Laboratory (NRL). The NCOM-based model of the Monterey Bay area is evaluated during a series of upwelling and relaxation wind events in August-September of 2000. The model receives open boundary conditions from a regional NCOM implementation of the California Current System and surface fluxes from the Navy Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS™)(COAMPS is a registered trademark of the Naval Research Laboratory). Issues investigated in this study are: NCOM-based model simulations of upwelling and relaxation events, coupling to COAMPS, use of sigma versus hybrid (sigma-z) vertical grids, and coupling with a larger-scale model on the open boundaries. The NCOM simulations were able to reproduce the observed sequence of the upwelling and relaxation events, which can be attributed, in part, to the good agreement between the observed and COAMPS winds. Comparisons with the mooring observations show that COAMPS overestimates shortwave radiation values, which makes the NCOM modeled SSTs too warm in comparison with observations. The NCOM runs forced with different resolution atmospheric forcing (3 versus 9 km) do not show significant differences in the predicted SSTs and mixed-layer depths at the mooring locations. At the same time, during the extended upwelling event, the model runs forced with 3 and 9 km resolution COAMPS fields show differences in the surface circulation patterns, which are the most distinct in the southern portion of the model domain. The model run with 9-km forcing develops a northward flow along the coast, which is not present in the run with 3-km forcing and in observations (for example, HF radar-derived radials). Comparison of the wind patterns of the 3- and 9-km products shows a weakening of the 9-km wind stress along the southern coast of the NCOM model domain, which is responsible for the development of the artificial northward flow in the NCOM run with 9-km forcing. Copyright 2007 by the American Geophysical Union."
"7101626797;35552766800;7005997993;7005284879;7006805293;6701417681;57199729569;","Feature-oriented regional modeling and simulations in the Gulf of Maine and Georges Bank",2003,"10.1016/S0278-4343(02)00151-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037328414&doi=10.1016%2fS0278-4343%2802%2900151-6&partnerID=40&md5=82a988988ae97a2a1240705db07feb43","The multiscale synoptic circulation system in the Gulf of Maine and Georges Bank (GOMGB) region is presented using a feature-oriented approach. Prevalent synoptic circulation structures, or 'features', are identified from previous observational studies. These features include the buoyancy-driven Maine Coastal Current, the Georges Bank anticyclonic frontal circulation system, the basin-scale cyclonic gyres (Jordan, Georges and Wilkinson), the deep inflow through the Northeast Channel (NEC), the shallow outflow via the Great South Channel (GSC), and the shelf-slope front (SSF). Their synoptic water-mass (T-S) structures are characterized and parameterized in a generalized formulation to develop temperature-salinity feature models. A synoptic initialization scheme for feature-oriented regional modeling and simulation (FORMS) of the circulation in the coastal-to-deep region of the GOMGB system is then developed. First, the temperature and salinity feature-model profiles are placed on a regional circulation template and then objectively analyzed with appropriate background climatology in the coastal region. Furthermore, these fields are melded with adjacent deep-ocean regional circulation (Gulf Stream Meander and Ring region) along and across the SSF. These initialization fields are then used for dynamical simulations via the primitive equation model. Simulation results are analyzed to calibrate the multiparameter feature-oriented modeling system. Experimental short-term synoptic simulations are presented for multiple resolutions in different regions with and without atmospheric forcing. The presented 'generic and portable' methodology demonstrates the potential of applying similar FORMS in many other regions of the Global Coastal Ocean. © 2003 Elsevier Science Ltd. All rights reserved."
"7402435469;","Convergence of atmospheric simulations with increasing horizontal resolution and fixed forcing scales",1999,"10.3402/tellusa.v51i5.14485","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033372661&doi=10.3402%2ftellusa.v51i5.14485&partnerID=40&md5=18ec4e488c1808de4ef20e5dcc875800","A series of experiments with the NCAR Community Climate Model, Version 2 (CCM2) is examined in which the grid and scale of the physical parameterizations are held fixed while the horizontal resolution of the dynamical core is increased. The convergence characteristics of these dual-resolution simulations are compared to those of simulations with the standard model in which the resolutions of both the dynamical core and physical parameterizations are increased together, as traditionally done in atmospheric model convergence studies. With the standard model the upward branch of the local Hadley circulation increases in strength with increasing horizontal resolution and does not converge by T170 truncation. As the dynamical resolution is increased, but the parameterization resolution held fixed, the dual-resolution model simulations converge to a state close to that produced by the standard model at the fixed parameterization resolution. The mid-latitude transient aspects do not converge with increasing resolution when the scale of the physics is held fixed. The nonlinear interactions in the dynamics create finer scales, with or without the finer scale forcing. However, the lower resolution T42 scales appear to converge. These convergence characteristics are shared by both the dual-resolution model and the standard model when horizontal resolution is increased."
"55986838800;6701840054;","A three-dimensional ocean mesoscale simulation using data from the SEMAPHORE experiment: Mixed layer heat budget",1998,"10.1029/98JC00452","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032532905&doi=10.1029%2f98JC00452&partnerID=40&md5=f523a57397651cadec079b3d145f8a5d","A primitive equation model is used to simulate the mesoscale circulation associated with a portion of the Azores Front investigated during the intensive observation period (IOP) of the Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites Oceaniques: Recherche Experiméntale (SEMAPHORE) experiment in fall 1993. The model is a mesoscale version of the ocean general circulation model (OGCM) developed at the Laboratoire d'Océanographie Dynamique et de Climatologie (LODYC) in Paris and includes open lateral boundaries, a 1.5-level-order turbulence closure scheme, and fine mesh resolution (0.11° for latitude and 0.09° for longitude). The atmospheric forcing is provided by satellite data for the solar and infrared fluxes and by analyzed (or reanalyzed for the wind) atmospheric data from the European Centre for Medium-Range Weather Forecasts (ECMWF) forecast model. The extended data set collected during the IOP of SEMAPHORE enables a detailed initialization of the model, a coupling with the rest of the basin through time dependent open boundaries, and a model/data comparison for validation. The analysis of model outputs indicates that most features are in good agreement with independent available observations. The surface front evolution is subject to an intense deformation different from that of the deep front system, which evolves only weakly. An estimate of the upper layer heat budget is performed during the 22 days of the integration of the model. Each term of this budget is analyzed according to various atmospheric events that occurred during the experiment, such as the passage of a strong storm. This facilitates extended estimates of mixed layer or relevant surface processes beyond those which are obtainable directly from observations. Surface fluxes represent 54% of the heat loss in the mixed layer and 70% in the top 100-m layer, while vertical transport at the mixed layer bottom accounts for 31% and three-dimensional processes account for 14%. Copyright 1998 by the American Geophysical Union."
"55469187200;","Jovian dynamics. Part I: Vortex stability, structure, and genesis",1996,"10.1175/1520-0469(1996)053<2685:JDPVSS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0001103217&doi=10.1175%2f1520-0469%281996%29053%3c2685%3aJDPVSS%3e2.0.CO%3b2&partnerID=40&md5=58729e4eb3acdd3ff5ded4195ff82435","The vertical structure of Jupiter's atmosphere is probed and isolated by evaluating the stability characteristics of planetary vortices over a wide parameter range. The resulting structures lead to simulating the genesis of single and multiple vortex states in Part I of this paper and the genesis of an equatorial superrotation and midlatitudinal multiple jets in Part II. The stability and genesis of baroclinic Rossby vortices, the vortices associated with long solitary Rossby waves in a stratified fluid, are studied numerically using a primitive equation model with Jovian and oceanic parameters and hypothetical structures. Vortex stability, that is, coherence and persistence, depends primarily upon latitude location and vertical structure and is used to deduce possible stratifications for Jupiter's atmosphere. The solutions suggest that Jupiter's large-scale motions are confined to a layer of depth h and are bounded by an abyss with an impermeable interface at a depth H, such that h/H ≤ 1/20. Consequently, they also extend earlier results derived with the reduced-gravity, shallow-water model, particularly the explanation for the origin, uniqueness, and longevity of the Great Red Spot (GRS). Beginning at the equator, stable anticyclones are seen to exist only when they have the Hermitian latitudinal form, the Korteweg-deVries longitudinal form, the confined exponential vertical structure exp(Nz/H), and the amplitude range as prescribed by the analytical theory of Marshall and Boyd for N = 8. Soliton interactions occur between equatorial vortices of similar horizontal and vertical form. In middle and low latitudes, shallow anticyclones with an exponential structure of N = 20 exist quasi-stably for a variety of sizes. Such vortices remain coherent but tend to migrate equatorward (where they disperse) at rates that depend upon their size, location, and vertical structure: large and medium anticyclones propagate primarily westward while migrating slowly, whereas small storms just migrate rapidly and then collapse. The migration of these large, shallow vortices can be reduced, but not stopped, in low latitudes by an easterly jet with the same vertical structure. Anticyclones are stabler when they are thinner relative to the abyss. Thus, when N = 60, their migration is sufficiently slow that it can be stopped by a weak easterly jet. Furthermore, absolute stability sets in when N = 90 and migration ceases completely for the large, thin anticyclones that now just propagate westward. Such flows may also be usefully represented by a vertical structure that is linear in z for the velocity and static stability in the thin upper layer and vanishes in the abyss. Large, thin (N ≥ 90) anticyclones can exist indefinitely either freely or when embedded within an anticyclonic zone of alternating jet streams of similar vertical structure. This holds true for the confined linear-z representation also. The permanence of GRS-like, low-latitude vortices in Jovian flow configurations occurs in a variety of lengthy calculations with thin structures. Ocean vortices are less persistent because the thermocline is relatively thick. The baroclinic instability of easterly jets is nonquasigeostrophic and takes on the form of solitary rather than periodic waves when the jets have a thin exponential (N ≥ 90) or confined linear-z structure. Such nonlinear waves develop into vortices that exhibit a variety of configurations and evolutionary paths. In most cases multiple mergers tend toward an end state with a single large vortex. Two types of merging occur in which a stronger vortex either catches a weaker one ahead of it or reels in a weaker one from behind. This duality occurs because propagation rates depend as much on local as on global conditions. In a further complication, vortices generated by an unstable easterly tend to have an exponential structure for exponential jets but a first baroclinic eigenmodal structure for confined linear-z jets. Single vortex states resembling the GRS, with sizes ranging from 15° to 50° in longitude and with temperature gradients, velocities, and propagation rates near the observed range, can be generated either directly through the growth of a local front in a marginally unstable easterly jet or indirectly through a series of mergers of the multiple vortices generated by a more unstable easterly jet. Sets of vortices can be produced simultaneously in the anticyclonic zones centered about latitudes -21°, -33°, and -41°, and have the same relative scales as Jupiter's GRS, Large Ovals, and Small Ovals. Thin anticyclones can also be generated at the equator by the action of vortices lying in low latitudes. Equally realistic long-lived vortices can also be generated by jets with structures matching the recent Galileo spacecraft observations by using other hyperbolic forms and greater depth scales."
"7003784067;6602410736;","The effects of differential vertical diffusion of T and S in a box model of thermohaline circulation",1996,"10.1357/0022240963213628","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030433577&doi=10.1357%2f0022240963213628&partnerID=40&md5=7095e5cb279401fcce9825afeb31b864","A diffusive box model, consistent with geostrophy, is proposed as an alternative to more usual advective box models of the ocean thermohaline circulation. When vertical diffusion coefficients for T and S are taken as identically equal (the normal assumption in all numerical ocean models to date), the diffusive box model exhibits both steady-state modes and time-dependent behaviors which are essentially indistinguishable from those of an advective model, under both fixed flux and mixed (T restoring) boundary conditions. The thermohaline ""circulation"" of the diffusive box model, however, is a combination of a convective branch and a vertical diffusive branch, involving zero volume flux. Modifications in behavior of the diffusive box model are investigated for a plausible range of values for the ratio d = KS/KT of the vertical turbulent diffusivities of S and T. When surface fluxes of heat and freshwater are constant, the model with d ≠ 1 exhibits additional steady-state modes in which convection is absent from the system, as well as a periodic oscillatory mode. Compared to results with d ≡ 1 under mixed surface boundary conditions, the model with d ≠ 1 exhibits extended ranges of multiple equilibria, a different mode transition near present-day values of freshwater forcing magnitude, and the possibility of quasi-periodic oscillatory states. The sensitivity of the present box model, coupled with that previously observed in a primitive equation model (Gargett and Holloway, 1992), raises serious questions about the ability of numerical models to predict the evolution of the ocean thermohaline circulation under changing atmospheric forcing, even if other problems with such prediction were resolved."
"15048581500;6507073275;","Massively parallel solvers for elliptic partial differential equations in numerical weather and climate prediction",2014,"10.1002/qj.2327","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922885646&doi=10.1002%2fqj.2327&partnerID=40&md5=511f47981961aec2b2935fc9ce5f509f","The demand for substantial increases in the spatial resolution of global weather and climate prediction models makes it necessary to use numerically efficient and highly scalable algorithms to solve the equations of large-scale atmospheric fluid dynamics. For stability and efficiency reasons, several of the operational forecasting centres, in particular the Met Office and the European Centre for Medium-Range Weather Forecasts (ECMWF) in the UK, use semi-implicit semi-Lagrangian time-stepping in the dynamical core of the model. The additional burden with this approach is that a three-dimensional elliptic partial differential equation (PDE) for the pressure correction has to be solved at every model time step and this often constitutes a significant proportion of the time spent in the dynamical core. In global models, this PDE must be solved in a thin spherical shell. To run within tight operational time-scales, the solver has to be parallelized and there seems to be a (perceived) misconception that elliptic solvers do not scale to large processor counts and hence implicit time-stepping cannot be used in very high-resolution global models. After reviewing several methods for solving the elliptic PDE for the pressure correction and their application in atmospheric models, we demonstrate the performance and very good scalability of Krylov subspace solvers and multigrid algorithms for a representative model equation with more than 1010 unknowns on 65 536 cores on the High-End Computing Terascale Resource (HECToR), the UK's national supercomputer. For this, we tested and optimized solvers from two existing numerical libraries (the Distributed and Unified Numerics Environment (DUNE) and Parallel High Performance Preconditioners (hypre)) and implemented both a conjugate gradient solver and a geometric multigrid algorithm based on a tensor-product approach, which exploits the strong vertical anisotropy of the discretized equation. We study both weak and strong scalability and compare the absolute solution times for all methods; in contrast to one-level methods, the multigrid solver is robust with respect to parameter variations. © 2014 Royal Meteorological Society."
"36992744000;15765007300;","Impact of physical parameterizations on idealized tropical cyclones in the Community Atmosphere Model",2011,"10.1029/2010GL046297","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951884237&doi=10.1029%2f2010GL046297&partnerID=40&md5=f35fb0ae6ad682d0856427c029dfe06f","This paper explores the impact of the physical parameterization suite on the evolution of an idealized tropical cyclone within the National Center for Atmospheric Research's (NCAR) Community Atmosphere Model (CAM). The CAM versions 3.1 and 4 are used to study the development of an initially weak vortex in an idealized environment over a 10-day simulation period within an aqua-planet setup. The main distinction between CAM 3.1 and CAM 4 lies within the physical parameterization of deep convection. CAM 4 now includes a dilute plume Convective Available Potential Energy (CAPE) calculation and Convective Momentum Transport (CMT). The finite-volume dynamical core with 26 vertical levels in aqua-planet mode is used at horizontal grid spacings of 1.0, 0.5 and 0.25. It is revealed that CAM 4 produces stronger and larger tropical cyclones by day 10 at all resolutions, with a much earlier onset of intensification when compared to CAM 3.1. At the highest resolution CAM 4 also accounts for changes in the storm's vertical structure, such as an increased outward slope of the wind contours with height, when compared to CAM 3.1. An investigation concludes that the new dilute CAPE calculation in CAM 4 is largely responsible for the changes observed in the development, strength and structure of the tropical cyclone. Copyright © 2011 by the American Geophysical Union."
"35363537800;55366919900;7402755545;57219264062;57079437400;7004870892;6602562780;","Connectivity among straits of the northwest Pacific marginal seas",2009,"10.1029/2008JC005218","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69549101752&doi=10.1029%2f2008JC005218&partnerID=40&md5=21ef5cdb8692cd9da18ad43e10215268","The connectivity among straits of the northwest Pacific marginal seas is investigated with a primitive-equation ocean circulation model simulated for 10 years from 1994 to 2003. Over the simulation interval the temporal and spatial means and variations of the model sea surface temperature are comparable to those of the satellite sea surface temperature. The model transport through the straits shows good agreement with the available observations and a high seasonality in the Taiwan Strait, the Korea Strait, and the Soya Strait but relatively low seasonality in the Tsugaru Strait. The Kuroshio and Taiwan Warm Current (TWC) are two sources of water flowing through the Korea Strait. The volume transport in the Korea Strait is dominated by the Kuroshio in winter (83%) and by the TWC in summer (66%). Relative to the transport through the Korea Strait, the transport percentages of the Tsugaru Strait connecting to the northwest Pacific Ocean are 79% in winter and 65% in summer. The seasonality of the Korea Strait transport is positively correlated with the cross-strait wind stress. The drifter experiments show that it takes about 4 months for most of the drifters deployed in the Taiwan Strait to enter the Korea Strait and more than 2 months to travel from the Korea Strait to the Tsugaru and Soya straits. Copyright 2009 by the American Geophysical Union."
"36077992900;7005874502;7005720566;","The nonlinear transient atmospheric response to tropical forcing",2007,"10.1175/2007JCLI1383.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-37349130222&doi=10.1175%2f2007JCLI1383.1&partnerID=40&md5=8526deb0287c062bda3339fd27e65ee5","Ensemble integrations using a primitive-equation dry atmospheric model were performed to investigate the atmospheric transient response to tropical thermal forcings that resemble El Niño and La Niña. The response develops in the North Pacific within 1 week after the integration. The signal in the North Atlantic and Europe is established by the end of the second week. Significant asymmetry was found between the responses in El Niñlo and La Niña that is similar to the observations, that is, one feature is that the 550-hPa positive height response in the North Pacific of the La Niña run is located about 30° west of the negative response of the El Niño run; another feature is that the responses in the North Atlantic and Europe for the La Niña and El Niño cases have similar patterns with the same polarity. The first feature is established within 2 weeks of the integration, while the second feature develops starting from the end of the second week. Several factors contribute to this nonlinearity of the response. In the Tropics, the shape of the Rossby wave response and the zonal extent of the Kelvin wave are not symmetric between El Niño and La Niña, which seems to be associated with the dependence of the wave property on the modified zonal mean flow. This is especially important in the equatorial region to the west of the forcing, which is likely responsible for the phase shift of the major extratropical response in the North Pacific. The transient eddy activity in the extratropics feeds back to the response and helps to maintain the nonlinearity. © 2007 American Meteorological Society."
"7004429544;","Semi-implicit time-integrators for a scalable spectral element atmospheric model",2005,"10.1256/qj.03.218","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27144503810&doi=10.1256%2fqj.03.218&partnerID=40&md5=9d689f4a6724e4c108ff7877080d3518","The Naval Research Laboratory's spectral element atmospheric model (NSEAM) for scalable computer architectures is presented. This new dynamical core is based on a high-order spectral element (SE) method in space and uses semi-implicit methods in time based on either the traditional second-order leapfrog (LF2) or second-order backward difference formulas (BDF2). The novelties of NSEAM are: it is geometrically flexible and thereby can accommodate any type of grid; LF2 or BDF2 are used to construct the semi-implicit method; and the horizontal operators are written, discretized, and solved in three-dimensional Cartesian space. The semi-implicit NSEAM is validated using: five baroclinic test cases; direct comparisons to the explicit version of NSEAM which has been extensively tested and the results previously reported in the literature; and comparisons with operational weather prediction and well-established climate models. A comparison with the US Navy's spectral transform global forecast model illustrates that NSEAM is 60% faster on an IBM SP4 using 96 processors for the current operational resolution of T239 L30. However, NSEAM can accommodate many more processors while continuing to scale efficiently even at higher grid resolutions. In fact, we show that at T498 L60, NSEAM scales linearly up to 384 processors. © Royal Meteorological Society, 2005."
"6508127897;7003967543;6602864563;","Secondary flows induced by wind forcing in the Rhône region of freshwater influence",2004,"10.1007/s10236-003-0079-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4944234723&doi=10.1007%2fs10236-003-0079-y&partnerID=40&md5=33ad10e60b3dcc73b3b3b7b305179c82","Secondary flows induced by the blocking effect of a river plume on a transverse upwelling are investigated in a microtidal region of freshwater influence (ROFI). A nested version of the SYMPHONIE primitive-equation free-surface model for 3-D baroclinic coastal flows has been developed for the Rhône ROFI. The main characteristics of the model are a generalized sigma coordinate system in finite differences, using a time splitting for external and internal modes and high-order numerical advection schemes for density fields in combination with an modified turbulence closure scheme. The nesting system consists of two grids forced by the high-resolution A LADIN model atmospheric data. The coarse grid of 3 km resolution for the whole Gulf of Lions allows the forcing of the Liguro-Provençal large-scale current when the fine mesh of 1-km resolution is centred on the river mouth of the Grand Rhône. Documented field experiments from the Biodypar 3 field campaign performed during March 1999 are used for validation. Numerical results, CTD profiles and a SPOT TSM visible image are in good agreement concerning the shape and structure of the river plume. Other coastal flow features can be observed from satellite imagery. Computations of realistic situations recover these main secondary structures. Complementary process-oriented runs give an explanation of how the coastal upwelling induced by an inhomogeneous offshore wind is destabilized by the combination of the river plume and along-shelf current-blocking effects. In the end, a factor-separation analysis provides evidence that the locally non-linear effects in momentum contribute to the occurrence of secondary vortices."
"7102969748;56056796100;7006334009;6602080118;8708285900;7003749832;7004862184;7005163997;57199567923;7003312252;6603858877;6602626008;7003935423;6603627827;7003354633;7003658485;6602901792;15749208900;7003580674;7202214528;6602128937;15749483800;56253852700;6602115663;","Model intercomparison in the Mediterranean: MEDMEX simulations of the seasonal cycle",2002,"10.1016/S0924-7963(02)00060-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18444394310&doi=10.1016%2fS0924-7963%2802%2900060-X&partnerID=40&md5=84cf32c8fed3e61263af78b88ca2fa4c","The simulation of the seasonal cycle in the Mediterranean by several primitive equation models is presented. All models were forced with the same atmospheric data, which consists in either a monthly averaged wind-stress with sea surface relaxation towards monthly mean sea surface temperature and salinity fields, or by daily variable European Centre for Medium Range Weather Forecast (ECMWF) reanalysed wind-stress and heat fluxes. In both situations models used the same grid resolution. Results of the modelling show that the model behaviour is similar when the most sensitive parameter, vertical diffusion, is calibrated properly. It is shown that an unrealistic climatic drift must be expected when using monthly averaged forcing functions. When using daily forcings, drifts are modified and more variability observed, but when performing an EOF analysis of the sea surface temperature, it is shown that the basic cycle, represented similarly by the models, consists of the seasonal cycle which accounts for more than 90% of its variability. © 2002 Elsevier Science B.V. All rights reserved."
"7003553425;6701746830;6506782011;7003941060;","The response of the Greenland ice sheet to climate changes in the 21st century by interactive coupling of an AOGCM with a thermomechanical ice-sheet model",2002,"10.3189/172756402781816537","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036968119&doi=10.3189%2f172756402781816537&partnerID=40&md5=5d405e17724c284125ca51125c7bba92","We present results from a greenhouse warming experiment obtained from an atmosphere-ocean-sea-ice general circulation model that is interactively coupled with a three-dimensional model of the Greenland ice sheet. The experiment covers the period 1970-2099 and is driven by the mid-range Intergovernmental Panel on Climate Change SRESB2 scenario. The Greenland model is a thermomechanical high-resolution (20 km) model coupled with a viscoelastic bedrock model. The melt-and-runoff model is based on the positive degree-day method and includes meltwater retention in the snowpack and the formation of superimposed ice. The atmospheric-oceanic general circulation model (AOGCM) is a coarse-resolution model without flux correction based on the Laboratoire de Météorologie Dynamique (Paris) LMD 5.3 atmospheric model coupled with a primitive-equation, free-surface oceanic component incorporating sea ice (coupled large-scale ice-ocean (CLIO). By 2100, average Greenland annual temperature is found to rise by about 4.5°C and mean precipitation by about 35%. The total fresh-water flux approximately doubles over this period due to increased runoff from the ice sheet and the ice-free land, but the calving rate is found to decrease by 25%. The ice sheet shrinks equivalent to 4 cm of sea-level rise. The contribution from the background evolution is not more than 50% of the total predicted sea-level rise. We did not find significant changes in the patterns of climate change over the North Atlantic region compared with a climate-change run without Greenland fresh-water feedback."
"7402205043;56962915800;","A coupled modeling study of the seasonal cycle of the Pacific cold tongue. Part I: Simulation and sensitivity experiments",2001,"10.1175/1520-0442(2001)014<0765:ACMSOT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035284321&doi=10.1175%2f1520-0442%282001%29014%3c0765%3aACMSOT%3e2.0.CO%3b2&partnerID=40&md5=5926b02aed049b892f7588225af6d01f","A coupled tropical ocean-atmosphere model that fills the gap between anomalous coupled models and fully coupled general circulation models is described. Both the atmosphere and ocean are represented by two and one-half layer primitive equation models, which accentuate the physical processes in the oceanic mixed layer and atmospheric boundary layer. The two media are coupled through both momentum and heat flux exchanges without explicit flux correction. The coupled model, driven by solar radiation, reproduces realistic seasonal cycles of the mixed layer temperature, currents, and depth, and the surface winds and rainfall in the tropical Pacific. The model results indicate that the equatorial westward phase propagation of the annual warming is primarily caused by zonal temperature advection and downward solar radiation modified by clouds, whereas the wind-evaporation-SST feedback plays a minor role. The meridional wind component appears to have a stronger impact than the zonal wind component on the seasonal cycle of the eastern Pacific cold tongue, because the cross equatorial winds have stronger annual variation, which is more effective in regulation of SST through changing surface evaporation and mixed layer entrainment. The annual variation of the solar forcing is shown to have a significant impact on the long-term mean state. Without the seasonal cycle forcing, the western Pacific warm pool would shift eastward and the latitudinal climate asymmetry in the eastern Pacific would be stronger."
"6602649666;26642891500;55951473800;","Generalized inverse of a reduced gravity primitive equation ocean model and tropical atmosphere-ocean data",2000,"10.1175/1520-0493(2000)128<1757:GIOARG>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033942738&doi=10.1175%2f1520-0493%282000%29128%3c1757%3aGIOARG%3e2.0.CO%3b2&partnerID=40&md5=d101533a3db89ecca7a1986a70f7784b","A nonlinear 21/2-layer reduced gravity primitive equations (PE) ocean model is used to assimilate sea surface temperature (SST) data from the Tropical Atmosphere-Ocean (TAO) moored buoys in the tropical Pacific. The aim of this project is to hindcast cool and warm events of this part of the ocean, on seasonal to interannual timescales. The work extends that of Bennett et al., who used a modified Zebiak-Cane coupled model. They were able to fit a year of 30-day averaged TAO data to within measurement errors, albeit with significant initial and dynamical residuals. They assumed a 100-day decorrelation timescale for the dynamical residuals. This long timescale for the residuals reflects the neglect of resolvable processes in the intermediate coupled model, such as horizontal advection of momentum. However, the residuals in the nonlinear PE model should be relatively short timescale errors in parameterizations. The scales for these residuals are crudely estimated from the upper ocean turbulence studies of Peters et al. and Moum. The assimilation is performed by minimizing a weighted least squares functional expressing the misfits to the data and to the model throughout the tropical Pacific and for 18 months. It is known that the minimum lies in the ""data subspace"" of the state or solution space. The minimum is therefore sought in the data subspace, by using the representer method to solve the Euler-Lagrange (EL) system. Although the vector space decomposition and solution method assume a linear EL system, the concept and technique are applied to the nonlinear EL system (resulting from the nonlinear PE model), by iterating with linear approximations to the nonlinear EL system. As a first step, the authors verify that sequences of solutions of linear iterates of the forward PE model do converge. The assimilation is also used as a significance test of the hypothesized means and covariances of the errors in the initial conditions, dynamics, and data. A ""strong constraint"" inverse solution is computed. However, it is outperformed by the ""weak constraint"" inverse. A cross validation by withheld data is presented, as well as an inversion with the model forced by the Florida State University winds, in place of a climatological wind forcing used in the former inversions."
"24425028900;7003833060;","Zonal winds near Venus' cloud top level: A model study of the interaction between the zonal mean circulation and the semidiurnal tide",1987,"10.1016/0019-1035(87)90100-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042890847&doi=10.1016%2f0019-1035%2887%2990100-X&partnerID=40&md5=e9b0d67d6e054dc78358ef385b0ae5a8","A primitive equation wave-mean flow interaction model, designed by J. R. Holton and used originally to study Earth's middle atmosphere, has been adapted to Venus in order to clarify our understanding of the interaction between the semidiurnal tide and the thermally driven mean meridional circulation near the cloud top level. With or without the tide the model produces midlatitude jets whose structure is insensitive to vertical shear of the background angular velocity above and below the cloud top level, but it is sensitive to background angular velocity at the cloud top level. When this background angular velocity is close to that of Venus, the latitudes and speeds of these jets are similar to the latitudes and speeds of jets at the Venus cloud top level as inferred from observed temperatures and the cyclostrophic balance condition. In agreement with the hypothesis of Fels and Lindzen, the model tide accelerates the equatorial zonal wind near the cloud top level and decelerates it at higher levels. The tidal vertical wavelength, maximum amplitude, dissipative decay length, and zonal flow accelerations are sensitive functions of background angular velocity, in agreement with elementary gravity wave theory. In the equatorial cloud top region, tidal acceleration is comparable in magnitude to the decelerative effects of vertical advection and the model's Rayleigh friction damping. For sufficiently rapid initial zonal flow near the cloud top level, the area-weighted global mean cloud top level zonal wind increases with time over a 50-day model run as a result of tidal acceleration. Agreement between the model tide and the observed tide, or the tide determined in the more detailed calculations of Pechmann and Ingersoll, is best when the background angular velocity at the jet level is about 30% larger than that observed. © 1987."
"35330117400;","The linear response of a stratified global atmosphere to tropical thermal forcing.",1984,"10.1175/1520-0469(1984)041<2217:TLROAS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021638906&doi=10.1175%2f1520-0469%281984%29041%3c2217%3aTLROAS%3e2.0.CO%3b2&partnerID=40&md5=562941835603ec41fce1dd8f100df4a9","The linear response of model normal modes in a stratified atmosphere to tropical thermal forcing is investigated by using global primitive equations which are linearized with respect to a resting state and include a prescribed thermal forcing and momentum dissipation. By the method of separation of the variables, the basic equations are split up into vertical and horizontal equations. The homogeneous parts of these equations are solved spectrally to obtain the model normal modes. -from Author"
"57190227631;55745955800;7401806579;","Sensitivity of simulated climate to two atmospheric models: Interpretation of differences between dry models and moist models",2013,"10.1175/MWR-D-11-00367.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878199629&doi=10.1175%2fMWR-D-11-00367.1&partnerID=40&md5=54d4041202a6b196858988e355875f95","The dynamical core of the Institute of Atmospheric Physics of theChinese Academy of SciencesAtmospheric General Circulation Model (IAP AGCM) and the Eulerian spectral transform dynamical core of the CommunityAtmosphereModel, version 3.1 (CAM3.1), developed at theNational Center forAtmosphericResearch (NCAR) are used to study the sensitivity of simulated climate. The authors report thatwhen the dynamical cores are used with the same CAM3.1 physical parameterizations of comparable resolutions, the model with the IAP dynamical core simulated a colder troposphere than that from the CAM3.1 core, reducing the CAM3.1 warm bias in the tropical and midlatitude troposphere. However, when the two dynamical cores are used in the idealized Held-Suarez tests without moisture physics, the IAP AGCM core simulated a warmer troposphere than that in CAM3.1. The causes of the differences in the full models and in the dry models are then investigated. The authors show that the IAP dynamical core simulated weaker eddies in both the full physics and the dry models than those in the CAM due to different numerical approximations. In the dry IAP model, the weaker eddies cause smaller heat loss from poleward dynamical transport and thus warmer troposphere in the tropics and midlatitudes. When moist physics is included, however, weaker eddies also lead to weaker transport of water vapor and reduction of high clouds in the IAP model, which then causes a colder troposphere due to reduced greenhouse warming of these clouds. These results show how interactive physical processes can change the effect of a dynamical core on climate simulations between two models. © 2013 American Meteorological Society."
"7003955986;56270367000;23478660100;6701550654;","Sea level forcing in the Mediterranean Sea between 1960 and 2000",2008,"10.1016/j.gloplacha.2008.07.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52949093501&doi=10.1016%2fj.gloplacha.2008.07.004&partnerID=40&md5=d53a5c47508f54b9a8e1093f55615f2b","Sea level trends and inter-annual variability in the Mediterranean Sea for the period 1960-2000 is explored by comparing observations from tide gauges with sea level hindcasts from a barotropic 2D circulation model, and two full primitive equation 3D ocean circulation models, a regional one and the Mediterranean component of a global one,. In the 2D model, 50% of the sea level variance was found to result from the wind and atmospheric pressure forcing. In the 3D models, 20% of the sea level variance was explained by the steric effects. The sea level residuals at the tide gauges locations, calculated by subtraction of the 2D model output from the sea level observations are significantly correlated (r = 0.4) with the steric signals from the 3D models. After the removal of the atmospheric and the steric contributions the tide-gauge sea level records indicate a period where sea level was stable (1960-1975) and a period where sea level was rising (1975-2000) with rates in the range 1.1-1.8 mm/yr. A part of the residual trend can be explained by the contribution of local land movements (0.3 mm/yr) while its major part indicates a global signal, probably mass addition, appearing after 1975. © 2008 Elsevier B.V. All rights reserved."
"7801685271;35932112100;7005677258;8558968300;","A polar low over the Japan Sea on 21 January 1997. Part II: A numerical study",2004,"10.1175/1520-0493(2004)132<1552:APLOTJ>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3943091071&doi=10.1175%2f1520-0493%282004%29132%3c1552%3aAPLOTJ%3e2.0.CO%3b2&partnerID=40&md5=b34590610089fb94b92abe275c9fb011","A remarkable isolated polar low observed over the Japan Sea on 21 January 1997 is studied by numerical simulations using a 20-km-mesh regional primitive equation model [Regional Spectral Model (RSM) of the Japan Meteorological Agency] and a 5-km-mesh nonhydrostatic mesoscale model [Meteorological Research Institute Nonhydrostatic Model (MRI-NHM)] and by sensitivity experiments using the MRI-NHM. The 24-h integration of RSM starting from 0000 UTC 21 January reproduces quite well the polar low's movement and development, including the initial wrapping of the west part of an east-west-oriented vorticity zone. The vorticity budget analysis indicates that the stretching term plays a dominant role in the polar low development. The simulation by MRI-NHM reproduces surprisingly well the wrapping of the western part of the east-west-oriented vortcity zone associated with a cloud band, the spiral-shaped cloud pattern, and the ""eye"" structure near the vortex center. The wind speed and resulting sea surface heat fluxes of the simulated polar low exhibited a significant deviation from axisymmetry. The eye, almost free of cloud, was relatively dry and was associated with a strong downdraft and a warm core. A thermodynamic budget analysis indicates that the warm core is mainly caused by the adiabatic warming due to the downdraft. Two types of sensitivity experiments using a 6-km-mesh MRI-NHM are performed: In the first type, the physical processes such as condensational heating and/or surface heat fluxes are switched on-off throughout the whole integration time of 24 h, as in the past sensitivity studies. In the second type, on the other hand, both condensational heating and surface heat fluxes are incorporated up to a certain time, but then one or all of them are switched on-off for the following 1 h. This minimizes the deformation of the environment of the vortex and is suitable for studying the direct effect of the physical processes on the vortex development. The results of the sensitivity experiments show that the rapid development of the present polar low is principally caused by the condensational heating. The surface heat fluxes, on the other hand, are important for maintaining the environment that supports the vortex development; that is, the absence of the surface heat fluxes stabilizes the stratification in the boundary layer so that the vortex development is severely suppressed. © 2004 American Meteorological Society."
"7203009194;7102535623;7003659713;35514012200;","Wind stress effects on subsurface pathways from the subtropical to tropical Atlantic",2002,"10.1175/1520-0485(2002)032<2257:WSEOSP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036670433&doi=10.1175%2f1520-0485%282002%29032%3c2257%3aWSEOSP%3e2.0.CO%3b2&partnerID=40&md5=14404b19b0a7a0f3c5ad28301679054d","A reduced-gravity, primitive equation, upper-ocean GCM is used to study subduction pathways in the Atlantic subtropical and tropical gyres. In order to compare the different responses in the pathways to strong and weak wind stress forcings, Hellerman and Rosenstein (HR) and da Silva (DSV) climatological annual-mean and monthly wind stress forcings are used to force the model. It is shown that subtropical-tropical communication is dependent on both the strength and structure of the wind forcing. A comparison between the two experiments shows two results for the North Atlantic: 1) the full communication window between the subtropical and tropical gyres is similar in width despite the difference in the intensity of the winds and 2) the interior exchange window width is substantially larger in the weak forcing experiment (DSV) than the strong forcing experiment (HR), accompanied by a larger transport as well. The South Atlantic exhibits a similar communication between the subtropics and Tropics in both cases. The annual-mean of the seasonally varying forcing also supports these results. A two-layer ventilated thermocline model is developed with a zonally varying, even though idealized, wind stress in the North Atlantic, which includes the upward Ekman pumping region absent from the classical ventilated thermocline model. The model shows that the communication window for subduction pathways is a function of the zonal gradient of the Ekman pumping velocity, not the Ekman pumping itself, at outcrop lines and at the boundary between the subtropical and tropical gyres. This solution is validated using three additional GCM experiments. It is shown that the communication windows are primarily explained by the ventilated thermocline model without considering the buoyancy effects. From the GCM experiments, the interior exchange window, which is a part of the communication window and cannot be explained by the ventilated thermocline model, is widened by two factors: 1) eliminating part of the positive Ekman pumping region in the eastern North Atlantic and 2) weakening the Ekman pumping over the whole region. The implications of these results suggest that changes in the wind forcing on the order of the difference in the wind products used here can have a significant effect on the attributes of the communication window and, hence, the thermocline structure at lower latitudes."
"7004014731;56228733900;7103342287;7404297096;56265106600;26426079600;","Mesospheric inversions and their relationship to planetary wave structure",2002,"10.1029/2001jd000756","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036231149&doi=10.1029%2f2001jd000756&partnerID=40&md5=8a8a0708a90d34759a44f4d23f8cc455","Mesospheric inversions are studied in vertical soundings from the French lidar at Observatoire de Haute-Provence and in synoptic global structure that was observed simultaneously by the UARS satellite. The latter provides the instantaneous three-dimensional (3-D) structure of the circulation that accompanies mesospheric inversions. A numerical simulation with a 3-D primitive equation model is then shown to reproduce major features of the observed behavior. Both reveal an extensive pattern of inverted thermal structure. The behavior is closely related to planetary waves, which, in the model, experience strong absorption in the upper mesosphere and lower thermosphere. Inverted thermal structure mirrors the synoptic pattern of potential vorticity, which marks the polar night vortex. Both are strongly distorted during stratospheric warmings, when inverted thermal structure at midlatitudes is favored. The region of negative lapse rate coincides with those altitudes where planetary wave temperature undergoes an abrupt phase shift. Wave temperature is then driven out of phase with wave geopotential. This alters the vertical structure of planetary waves, from westward tilt and upward amplification below the inversion to nearly barotropic structure and upward decay above the inversion. Accompanying the upward decay of planetary waves above the inversion is a decay of flow distortion, as the disturbed vortex is gradually restored toward polar symmetry."
"6603404591;7005485117;","An observing system simulation exeriment for the laser atmospheric wind sounder (LAWS)",1993,"10.1175/1520-0450(1993)032<1453:AOSSEF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027805236&doi=10.1175%2f1520-0450%281993%29032%3c1453%3aAOSSEF%3e2.0.CO%3b2&partnerID=40&md5=7fbc8596132fe8f6579656113fa097dc","A series of observing system simulation experiments (OSSEs) was conducted to assess the potential impact of the Laser Atmospheric Wind Sounder (LAWS) instrument on a 5-day forecast using the Florida State University (FSU) primitive equation multilevel spectral global circulation model. This proposed Earth Observing System satelliteborne instrument is a CO2 Doppler lidar wind sounding system. The instrument's requirement for usable measurements is that clouds or high concentrations of tropospheric aerosols must exist within the sample volume. The inclusion of LAWS wind observations exhibits an overall improvement of the forecast skill for this study. The greatest increase in skill is in the Southern Hemisphere, as can be seen in both the motion and mass fields. The 98° sun-synchronous orbit resolved the polar meteorological features much better than the 55° inclined orbit. Otherwise, the two different orbits were very similar, with the 55° inclined showing a better analysis of the tropics. -from Authors"
"6603906063;","Mesoscale upwelling and density finestructure in the seasonal thermocline - a dynamical model",1992,"10.1175/1520-0485(1992)022<1257:MUADFI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027075811&doi=10.1175%2f1520-0485%281992%29022%3c1257%3aMUADFI%3e2.0.CO%3b2&partnerID=40&md5=c7e07265de079518920da97110a0837a","Results of a three-dimensional primitive equation model are presented simulating turbulent mesoscale motions in the seasonal thermocline on an f plane. The model is based on a hybrid vertical coordinate scheme and conserves isopycnic potential vorticity. The model results support observations and findings of earlier atmospheric and oceanic models. It is emphasized that mesoscale turbulent structures may have a profound influence on primary productivity, mixed-layer, and internal wave dynamics. -from Author"
"7409653025;7004093651;7101630970;7006629146;","A vertical finite-difference scheme based on a hybrid σ-θ-p coordinate",1992,"10.1175/1520-0493(1992)120<0851:avfdsb>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027041959&doi=10.1175%2f1520-0493%281992%29120%3c0851%3aavfdsb%3e2.0.co%3b2&partnerID=40&md5=b62c7f4a9c1e2a3327fb82704f7e154c","A vertical discretization of the primitive equations in a general vertical coordinate is described that enables a primitive equation model to use terrain-following sigma levels near the ground and isentropic levels higher up, with a smooth transition region in between. Therefore, it combines many of the advantages of the computational efficiency of σ coordinates and the predictive and diagnostic potential of θ coordinates, and should be particularly useful for general circulation models to be used for studies of stratosphere-troposphere exchange and middle-atmosphere transport of trace gases. It is shown that the semi-implicit time scheme can be used in a straightforward manner with this discretization. -from Authors"
"7005454026;6602920335;","Diagnosis of ageostrophic circulations in a two-dimensional primitive equation model of frontogenesis.",1985,"10.1175/1520-0469(1985)042<1283:DOACIA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022264252&doi=10.1175%2f1520-0469%281985%29042%3c1283%3aDOACIA%3e2.0.CO%3b2&partnerID=40&md5=3932cae2a6f4be4c5b84229b85c6e114","Diagnoses are presented of the transverse ageostrophic circulation patterns for two cases from a two-dimensional primitive equation model of frontogenesis forced by a combination of confluence and horizontal shear. The cold advection case (the specified alongfront potential temperature gradient results in differential cold advection by the upper-level jet) realistically simulates upper-level frontogenesis in response to tilting by a cross-front gradient of subsidence. The warm advection case features a frontal system spanning the troposphere, which develops in response to differential horizontal advection. -from Authors"
"16439174800;","On the linear theory of the atmospheric response to sea surface temperature anomalies.",1977,"10.1175/1520-0469(1977)034<0603:otltot>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0017445571&doi=10.1175%2f1520-0469%281977%29034%3c0603%3aotltot%3e2.0.co%3b2&partnerID=40&md5=a9503d648808299a0aaad8d5209cef9e","A linear, hemispheric, two-level model which is based on the primitive equations is used to study the steady-state response of the atmosphere to sea surface temperature anomalies ( SSTA ). First it is shown by comparison with analytical theories that the model's vertical resolution is not too coarse for such a study. Then the model's response to an idealised heat source in middle latitudes is examined, and it is demonstrated that the main features of the response can be explained in terms of a simple quasi-geostrophic theory. The model is applied to SSTA cases off Newfoundland where statistically significant observations are available. The verification of the model's results against these observations is generally favourable downstream of the SSTA, i.e., the observed low (high) at the surface downstream of a warm (cold) pool is simulated. However, the linear theory predicts a weak surface high upstream of a positive SSTA which has no statistically significant counterpart in the observations. The model is able to reproduce approximately the blocking situation over Europe during the period 1958-60 when the observed SSTA in the Atlantic is prescribed. Realistic pressure and flow patterns in the tropics are obtained for an SSTA in the eastern equatorial Pacific and for an SSTA in the tropical Atlantic. In the first case the influence of SSTA's in the tropics on the mid-latitude circulation turns out to be negligible. This result is not supported by the observations. The SSTA in the Atlantic, however, causes a rather strong response at midlatitudes which is similar to that found in experiments with general circulations models where the same SSTA has been prescribed. The influence of the tropical mean basic wind field and the grid spacing on the midlatitude response is discussed. Finally, it is shown that the linear model must fail when the SSTA is the result of atmospheric circulation anomalies. (A)"
"57190120779;57203084853;","Seasonal sensitivity of the eddy-driven jet to tropospheric heating in an idealized AGCM",2016,"10.1175/JCLI-D-15-0723.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977550085&doi=10.1175%2fJCLI-D-15-0723.1&partnerID=40&md5=a65fb6914ace8537644583d116937572","A dry dynamical core is used to investigate the seasonal sensitivity of the circulation to two idealized thermal forcings: A tropical upper-tropospheric heating and a polar lower-tropospheric heating. The thermal forcings are held constant, and the response of the circulation in each month of the year is explored. First, the circulation responses to tropical warming and polar warming are studied separately, and then the response to the simultaneously applied forcings is analyzed. Finally, the seasonality of the internal variability of the circulation is explored as a possible mechanism to explain the seasonality of the responses. The primary results of these experiments are as follows: 1) There is a seasonal sensitivity in the circulation response to both the tropical and polar forcings. 2) The jet position response to each forcing is greatest in the transition seasons, and the jet speed response exhibits a seasonal sensitivity to both forcings, although the seasonal sensitivities are not the same. 3) The circulation response is nonlinear in the transition seasons, but approximately linear in the winter months. 4) The internal variability of the unforced circulation exhibits a seasonal sensitivity that may partly explain the seasonal sensitivity of the forced response. The seasonality of the internal variability of daily MERRA reanalysis data is compared to that of the model, demonstrating that the broad conclusions drawn from this idealized modeling study may be useful for understanding the jet response to anthropogenic forcing. © 2016 American Meteorological Society."
"8696068200;56021872900;55998591400;55416202700;57193170776;6701735773;","DYNAMICO-1.0, an icosahedral hydrostatic dynamical core designed for consistency and versatility",2015,"10.5194/gmd-8-3131-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943742167&doi=10.5194%2fgmd-8-3131-2015&partnerID=40&md5=3268af5d76e5d1551fc2d3576b314042","The design of the icosahedral dynamical core DYNAMICO is presented. DYNAMICO solves the multi-layer rotating shallow-water equations, a compressible variant of the same equivalent to a discretization of the hydrostatic primitive equations in a Lagrangian vertical coordinate, and the primitive equations in a hybrid mass-based vertical coordinate. The common Hamiltonian structure of these sets of equations is exploited to formulate energy-conserving spatial discretizations in a unified way. The horizontal mesh is a quasi-uniform icosahedral C-grid obtained by subdivision of a regular icosahedron. Control volumes for mass, tracers and entropy/potential temperature are the hexagonal cells of the Voronoi mesh to avoid the fast numerical modes of the triangular C-grid. The horizontal discretization is that of Ringler et al. (2010), whose discrete quasi-Hamiltonian structure is identified. The prognostic variables are arranged vertically on a Lorenz grid with all thermodynamical variables collocated with mass. The vertical discretization is obtained from the three-dimensional Hamiltonian formulation. Tracers are transported using a second-order finite-volume scheme with slope limiting for positivity. Explicit Runge-Kutta time integration is used for dynamics, and forward-in-time integration with horizontal/vertical splitting is used for tracers. Most of the model code is common to the three sets of equations solved, making it easier to develop and validate each piece of the model separately. Representative three-dimensional test cases are run and analyzed, showing correctness of the model. The design permits to consider several extensions in the near future, from higher-order transport to more general dynamics, especially deep-atmosphere and non-hydrostatic equations. © 2015 Author(s)."
"55745073200;6701529532;","Simulated heat flux and sea ice production at coastal polynyas in the southwestern Weddell Sea",2013,"10.1002/jgrc.20133","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880722425&doi=10.1002%2fjgrc.20133&partnerID=40&md5=db9d783f8d69aab40d7aa40e55a8ef1d","Coastal polynyas are areas in an ice-covered ocean where the ice cover is exported, mostly by off-shore winds. The resulting reduction of sea ice enables an enhanced ocean-atmosphere heat transfer. Once the water temperatures are at the freezing point, further heat loss induces sea ice production. The heat exchange and ice production in coastal polynyas in the southwestern Weddell Sea is addressed using the Finite-Element Sea-ice Ocean Model, a primitive-equation, hydrostatic ocean circulation model coupled with a dynamic-thermodynamic sea-ice model, which allows to quantify the amount of heat associated with cooling of the water column. Three important polynya regions are identified: at Brunt Ice Shelf, at Ronne Ice Shelf and along the southern part of the Antarctic Peninsula. Multiyear winter means (May-September 1990-2009) give an upward heat flux to the atmosphere of 311 W/m2 in the Brunt polynyas, 511 W/m2 in Ronne Polynya and 364 W/m2 in the Antarctic Peninsula polynyas, whereof 57 W/m2, 49 W/m2 and 48 W/m2, respectively, are supplied as oceanic heat flux from deeper layers. The mean winter sea ice production is 7.2 cm/d in the Brunt polynyas corresponding to an ice volume of 1.3 ×1010 m 3/winter, 13.2 cm/d at Ronne polynya (4.4 ×1010 m3/winter), and 9.2 cm/d in the Antarctic Peninsula polynyas (2.1 ×1010 m3/winter). The heat flux to the atmosphere inside polynyas is 7 to 9 times higher than the heat flux in the adjacent area; polynya ice production per unit area exceeds adjacent values by a factor of 9 to 14. ©2013. American Geophysical Union. All Rights Reserved."
"6507400558;57199689992;7004978125;7801642934;","Multiscale waves in an MJO background and convective momentum transport feedback",2012,"10.1175/JAS-D-11-0152.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863396318&doi=10.1175%2fJAS-D-11-0152.1&partnerID=40&md5=7e91bb3ead32735d92ed96d2d5d9198e","The authors use linear analysis for a simple model to study the evolution of convectively coupled waves (CCWs) in a background shear and background moisture mimicking the observed structure of the Madden- Julian oscillation (MJO). This is motivated by the observation, in an idealized setting, of intraseasonal twoway interactions between CCWs and a background wind. It is found here that profiles with a bottom-heavy moisture content are more favorable to the development of mesoscale/squall line-like waves whereas synoptic-scale CCWs are typically more sensitive to the shear strength. The MJO envelope is thus divided into three regions, in terms of the types of CCWs that are favored: an onset region in front that is favorable to Kelvin waves, a mature or active region in the middle in which squall lines are prominent, and the stratiform and decay phase region in the back that is favorable to westward inertia-gravity (WIG) waves. A plausible convective momentum transport (CMT) feedback is then provided according to the results of the idealized two-way interaction model. The active region, in particular, coincides with the westerly wind burst where both Kelvin waves and squall lines are believed to play a significant role in both the deceleration of low-/high-level easterly/westerly winds and the acceleration of low-/high-level westerly/easterly winds. The WIG waves in the wake could be a precursor for a subsequent MJO event through the acceleration of low-/high-level easterly/ westerly winds, which in turn favor Kelvin waves, and the cycle repeats. These results open interesting directions for future studies using observations and/or detailed numerical simulations using the full primitive equation. © 2012 American Meteorological Society."
"7006075169;7202748672;","What constrains spread growth in forecasts initialized from ensemble Kalman filters?",2011,"10.1175/2010MWR3246.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951643933&doi=10.1175%2f2010MWR3246.1&partnerID=40&md5=c6c2a5e4226d7b4c08272bd8b38771a3","The spread of an ensemble of weather predictions initialized from an ensemble Kalman filter may grow slowly relative to other methods for initializing ensemble predictions, degrading its skill. Several possible causes of the slow spread growth were evaluated in perfectand imperfect-model experiments with a twolayer primitive equation spectral model of the atmosphere. The causes examined were the covariance localization, the additive noise used to stabilize the assimilation method and parameterize the system error, and the model error itself. In these experiments, the flow-independent additive noise was the biggest factor in constraining spread growth. Preevolving additive noise perturbations were tested as a way to make the additive noise more flow dependent. This modestly improved the data assimilation and ensemble predictions, both in the two-layer model results and in a brief test of the assimilation of real observations into a global multilevel spectral primitive equation model. More generally, these results suggest that methods for treating model error in ensemble Kalman filters that greatly reduce the flow dependency of the background-error covariances may increase the filter analysis error and decrease the rate of forecast spread growth. © 2011 American Meteorological Society."
"7401868458;55716319700;9244992800;","Vertically propagating Klevin waves and tropical tropopause variability",2008,"10.1175/2007JAS2466.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45849117654&doi=10.1175%2f2007JAS2466.1&partnerID=40&md5=688dcd7bd75412c315db23a1c036bf1f","The relationship between local convection, vertically propagating Kelvin waves, and tropical tropopause height variability is examined. This study utilizes both simulations of a global primitive-equation model and global observational datasets. Regression analysis with the data shows that convection over the western tropical Pacific is followed by warming in the upper troposphere (UT) and cooling in lower stratosphere (LS) over most longitudes, which results in a lifting of the tropical tropopause. The model results reveal that these UT-LS temperature anomalies are closely associated with vertically propagating Kelvin waves, indicating that these Kelvin waves drive tropical tropopause undulations at intraseasonal time scales. The model simulations further show that regardless of the longitudinal position of the imposed heating, the UT-LS Kelvin wave reaches its maximum amplitude over the western Pacific. This result, together with an analysis based on wave action conservation, is used to contend that the Kelvin wave amplification over the western Pacific should be attributed to the zonal variation of background zonal wind field, rather than to the proximity of the heating. The wave action conservation law is also used to offer an explanation as to why the vertically propagating Kelvin waves play the central role in driving tropical tropopause height undulations. The zonal and vertical modulation of the Kelvin waves by the background flow may help explain the origin of the very cold air over the western tropical Pacific, which is known to cause freeze-drying of tropospheric air en route to the stratosphere. © 2008 American Meteorological Society."
"6701335353;6603573706;16643457000;7003665132;7003430681;","Investigation of the summer Kara Sea circulation employing a variational data assimilation technique",2007,"10.1029/2006JC003728","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250758563&doi=10.1029%2f2006JC003728&partnerID=40&md5=d8605317c77fdb6ebfc209b30a404b75","The summer circulations and hydrographic fields of the Kara Sea are reconstructed for mean, positive and negative Arctic Oscillation regimes employing a variational data assimilation technique which provides the best fit of reconstructed fields to climatological data and satisfies dynamical and kinematic constraints of a quasi-stationary primitive equation ocean circulation model. The reconstructed circulations agree well with the measurements and are characterized by inflow of 0.63, 0.8, 0.51 Sv through Kara Gate and 1.18, 1.1, 1.12 Sv between Novaya Zemlya and Franz Josef Land, for mean climatologic conditions, positive and negative AO indexes, respectively. The major regions of water outflow for these regimes are the St. Anna Trough (1.17, 1.21, 1.34 Sv) and Vilkitsky/Shokalsky Straits (0.52, 0.7, 0.51 Sv). The optimized velocity pattern for the mean climatological summer reveals a strong anticyclonic circulation in the central part of the Kara Sea (Region of Fresh Water Inflow, ROFI zone) and is confirmed by ADCP surveys and laboratory modeling. This circulation is well pronounced for both high and low AO phases, but in the positive AO phase it is shifted approximately 200 km west relatively to its climatological center. During the negative AO phase the ROFI locaion is close to its climatological position. The results of the variational data assimilation approach were compared with the simulated data from the Hamburg Shelf Ocean Model (HAMSOM) and Naval Postgraduate School 18 km resolution (NPS-18) model to validate these models. Copyright 2007 by the American Geophysical Union."
"37019381400;7201785152;55686667100;","Dynamics of synoptic eddy and low-frequency flow interaction. Part III: Baroclinic model results",2006,"10.1175/JAS3717.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746864827&doi=10.1175%2fJAS3717.1&partnerID=40&md5=7390662a05e0babe17a9b1cd62ab9b7d","In this three-part study, a linear closure has been developed for the synoptic eddy and low-frequency flow (SELF) interaction and demonstrated that internal dynamics plays an important role in generating the leading low-frequency modes in the extratropical circulation anomalies during cold seasons. In Part III, a new linearized primitive equation system is first derived for time-mean flow anomalies. The dynamical operator of the system includes a traditional part depending on the observed climatological mean state and an additional part from the SELF feedback closure utilizing the observed climatological properties of synoptic eddy activity. The latter part relates nonlocally all the anomalous eddy-forcing terms in equations of momentum, temperature, and surface pressure to the time-mean flow anomalies. Using the observational data, the closure was validated with reasonable success, and it was found that terms of the SELF feedback in the momentum and pressure equations tend to reinforce the low-frequency modes, whereas those in the thermodynamic equation tends to damp the temperature anomalies to make the leading modes equivalent barotropic. Through singular vector analysis of the linear dynamical operator, it is highlighted that the leading modes of the system resemble the observed patterns of the Arctic Oscillation, Antarctic Oscillation, and Pacific-North American pattern, in which the SELF feedback plays an essential role, consistent with the finding of the barotropic model study in Part II. © 2006 American Meteorological Society."
"36077992900;7005874502;7004332887;56380425900;57111001300;","Tropical links of the Arctic Oscillation",2002,"10.1029/2002GL015822","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037110223&doi=10.1029%2f2002GL015822&partnerID=40&md5=b9e11fac456ce90aaa14d565d03db953","A primitive equation dry atmospheric model is used to investigate the response of the Arctic Oscillation (AO) to diabatic forcing. Integrations are made for 51 winter seasons (DJF) from 1948/49 to 1998/99. For each winter the model uses a time-averaged forcing that is calculated empirically from the NCEP/NCAR reanalyses. The ensemble mean of the simulations reproduces much of the observed AO interannual variability. Two additional sets of experiments are conducted. In one case the interannually varying forcing is prescribed only in the tropics, while in another it is prescribed only in the extratropics. These simulations indicate that a significant part of the interannual variability of the wintertime AO, as well as its trend, is linked to forcing from the tropics, and that extratropical forcing has no role to play, independent of the tropical forcing, in reconstructing the observed AO variability. © Copyright 2002 by the American Geophysical Union."
"7102969748;7102870874;7006653289;7003639093;6602678456;7003602532;","Modelling the Danube-influenced north-western continental shelf of the Black Sea. I: Hydrodynamical processes simulated by 3-D and box models",2002,"10.1006/ecss.2000.0658","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036522543&doi=10.1006%2fecss.2000.0658&partnerID=40&md5=f4db92bd3ef70c23ae04bbdb319daaa7","A hydrodynamical modelling of the Black Sea is presented using the GHER 3-D primitive equation model. Results of a very high resolution model with 5 km grid size are analysed and the dominant features of general circulation in the Black Sea are highlighted. Compared with a coarse resolution model, forced with the same climatic monthly averaged atmospheric data, the high resolution model exhibits stronger variability, including frontal structures and coastal upwellings induced by baroclinic instabilities, in particular along the Turkish coast. A comparison of the shelf-open sea exchanges, with particular focus on the cold intermediate waters, shows that both models lead to a replenishment of the CIL in the basin interior by cold waters formed on the shelf. Due to the better representation of frontal structures, the high resolution model is an appropriate candidate for coupling with a biological model. Problems of calibration, interpretation and data availability typically arise from this kind of coupled 3-D model. In order to overcome such difficulties, the results of the 3-D hydrodynamical model are used to guide the development of an integrated 0-D box model capable of achieving the objectives of projects like EROS21, where the effect of changes in the Danube inflows on the shelf ecosystem is investigated. The 0-D model is thus designed to cover this region and is obtained through integration over an appropriate variable volume. The integration procedure shows where the weaknesses of an 0-D approach might lie. Diagnoses in the 3-D model of the integral quantities show the range of uncertainty one can expect in the exchange laws of the 0-D model. © 2002 Elsevier Science Ltd. All rights reserved."
"7403058740;","Atmospheric energy cycle viewed from wave-mean-flow interaction and Lagrangian mean circulation",2001,"10.1175/1520-0469(2001)058<3036:AECVFW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035888770&doi=10.1175%2f1520-0469%282001%29058%3c3036%3aAECVFW%3e2.0.CO%3b2&partnerID=40&md5=027df5e60d1c919c640ef935d9a89442","A formulation is proposed to analyze energetics of the global atmosphere. To see effects of wave-mean-flow interaction and Lagrangian mean meridional circulation from nonlinear and nongeostrophic senses, rate equations of potential and kinetic energies are derived from primitive equations expressed in terms of the pressure-isentrope hybrid-vertical coordinates. The present scheme does not directly exchange the zonal mean available potential energy with the eddy available potential energy but does exchange the zonal mean kinetic energy with the eddy available potential energy. The latter is contributed to by the vertical divergence of the form drag over isentropic surfaces, which is the major term of the Eliassen-Palm flux divergence. One application is made to two-dimensional (a longitude-altitude plane) channel fluid. This system has no energy conversion between the mean and eddy kinetic energies. In the process of wave-mean-flow interactions, the mean flow amplifies waves through the advection of positive isentropic thickness anomaly toward higher portions over undulated isentropes and, accordingly, the mean kinetic energy is converted into the eddy available potential energy. The eddy available potential energy is converted into the eddy kinetic energy when the flow field deforms, conserving the mean zonal flows. Another application is made to baroclinic instability waves. The zonal mean available potential energy is released to the zonal mean kinetic energy by driving mean meridional wind. Simultaneously the kinetic energy of mean zonal wind is converted into the eddy available potential energy through wave-mean-flow interactions. Under the geostrophic equilibrium condition, these two conversions are almost equal to each other. Geostrophic adjustments may assist conversions from the eddy available potential energy into the eddy kinetic energy. All the processes might be the main stream of dynamical energy flows at mid- and high latitudes."
"7004258125;7006957668;","Empirical stochastic models for the dominant climate statistics of a general circulation model",1999,"10.1175/1520-0469(1999)056<3436:ESMFTD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033208559&doi=10.1175%2f1520-0469%281999%29056%3c3436%3aESMFTD%3e2.0.CO%3b2&partnerID=40&md5=dc1b7f94ce6b632ec50114460af11911","Two Markov models with different dynamics and forcing are used to model the transient eddy statistics of an idealized general circulation model (GCM). The first Markov model employs a physically based dynamical operator composed of the linearized primitive equations plus spatially uniform damping. This model, when driven by spatially uncorrelated forcing, failed to produce reasonable fluxes and variances, despite tuning of the damping and forcing coefficients. This result contrasts with previous studies that have used the linearized quasigeostrophic equations to model extratropical eddy statistics. The second Markov model is constructed empirically from the time-lagged covariances of the GCM time series. This empirical Markov model could reproduce the dominant covariances over a range of time lags, provided it contained a sufficiently large number of degrees of freedom. It could not, however, reproduce the time-lag evolution of the trailing EOFs contained in the model. The errors in the trailing EOFs displayed a systematic behavior that could be explained by assuming that the ""effective noise""-the noise required to reproduce the full covariances-is correlated over timescales comparable to the smallest e-folding time of the eigenmodes. Under this assumption, the effective noise is not white, but, for sufficiently large model dimension, the dominant disturbances still can be modeled appropriately by a Markov model because their associated decorrelation rates are small compared to the decorrelation rate of noise. This explanation is illustrated using a three-variable Markov model. These results suggest the following criteria for Markov model estimation: the lag and number of EOFs should be chosen such that the least damped modes show little or no dependence on lag and that none of the imaginary eigenvalues are aliased (in a sense defined in the paper). The resulting Markov model for the dominant disturbances is not sensitive to EOF truncation or choice of time lag, except for the structure of the singular vectors and adjoints, and the ordering of the eigenmodes. The sensitivity in singular vectors and adjoints is a plausible consequence of nonnormality, as nonnormality of the underlying physical system leads to singular vectors differing considerably from the normal modes and EOFs. The stable eigenmodes resemble the leading EOFs used to construct the empirical model, but differ considerably from the unstable eigenmodes of the linearized GCM. This difference is attributed to nonlinear processes implicitly represented in the Markov model. The dissipation and stochastic forcing were concentrated in the Tropics and subtropics, in contrast to the eddy variance and fluxes, which were concentrated in subtropics and midlatitudes. The associated singular vectors also were localized initially in the Tropics and subtropics, but eventually develop into robust extratropical disturbances. Interestingly, the dominant singular vectors undergo a growth and decay life cycle characteristic of the classic nonlinear life cycle, with time-averaged fluxes in close agreement with those diagnosed from the GCM climatology. The fact that the forcing, dissipation, and initial singular vectors are concentrated in the same vicinity suggests a dynamical feedback between Tropics and subtropics."
"7102046393;25953950400;","Balanced and unbalanced circulations in a primitive equation simulation of a midlatitude MCC. Part II: Analysis of balance",1997,"10.1175/1520-0469(1997)054<0479:baucia>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5844295882&doi=10.1175%2f1520-0469%281997%29054%3c0479%3abaucia%3e2.0.co%3b2&partnerID=40&md5=f1523a2c071df519674a8c4527dde863","A nonlinear balance condition, which permits the diagnosis of both balanced divergent and nondivergent flows, is presented. This analysis approach is applied to the results of a numerical simulation of a midlatitude mesoscale convective complex (MCC) to assess the degree of balance of these and similar convective weather systems. It is found that, to a large extent, the simulated MCC represents a highly balanced fluid system. The nondivergent component of the MCC wind field was found to be largely balanced from the time of initial convection to dissipation. Perhaps more surprisingly, the storm-induced divergent model winds are also balanced to a fair degree, though certainly less so than the nondivergent flow. Further, the balanced divergent flow makes up a significant portion of the total balanced flow in some regions of the MCC. System-scale divergence profiles of the model and balanced winds are compared and found to agree reasonably well, especially in the growth and mature stages of the MCC. Within a stationary averaging volume enclosing the MCC, the greatest disparity between the model and balanced circulations is found in the downward vertical motion. The model downward mass flux significantly exceeds the balanced downward flux at most times during the simulation, suggesting that the process of mass adjustment due to convective heating is largely dominated by unbalanced fast-manifold processes, such as inertiagravity waves. The unbalanced flow is found to be composed largely of divergent circulations of periodic nature (i.e., gravity waves). The appearance and characteristics of these features are found to be in good agreement with current theoretical predictions regarding the atmospheric response to convective heating and associated compensating subsidence. The (modified) Rossby radii (λR) for two lowest-order gravity wave modes are calculated. The mesoscale convective vortex (MCV) within the storm is larger than λR for all but the gravest mode. The λRn for the mature storm as an ensemble also indicates a good degree of balance with λRn=1 scaling similar to the MCC and larger values of n scaling smaller than the system as a whole. These λR values strongly suggest that this simulated MCC represents an inertially stable balanced mesoscale convective system."
"24784252800;","Variational principle of instability of atmospheric motions",1989,"10.1007/BF02658013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51249172002&doi=10.1007%2fBF02658013&partnerID=40&md5=087231520683528aa17a0dc6478dfa44","Problems of instability of rotating atmospheric motions are investigated by using nonlinear governing equations and the variational principle. The method suggested in this paper is universal for obtaining criteria of instability in all models with all possible basic flows. For example, the model can be barotropic or baroclinic, layer or continuous, quasi-geostrophic or primitive equations; the basic flow can be zonal or nonzonal, steady or unsteady. Although the basic flows possess a great deal of variety, they all are the stationary points in the functional space determined by an appropriate invariant functional. The basic flow is an unsteady one if the conservation of angular momentum is included in the associated functional. The second variation, linear or nonlinear, gives the criteria of instability. Especially, the general criteria of instability for unsteady basic flow, orographically disturbed flow as well as nongeostrophic flow are first obtained by the method described in this paper. It is also shown that the difference between the criteria of instability obtained by the linear theory and our variational principle clearly indicates the importance of using nonlinear governing equations. In the appendix the theory is extended to cases such as in a β-plane where the fluid does not possess finite total energy, hence the variational principle can not be directly applied. However, a generalized Liapounoff norm can still be obtained on the basis of variational consideration. © 1989 Advances in Atmospheric Sciences."
"57203088316;","The slow equations",1989,"10.1002/qj.49711548510","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024785033&doi=10.1002%2fqj.49711548510&partnerID=40&md5=e6c333d94957a11f1e066a0f431d5fcc","A filtered system of equations is derived, using the ideas of normal mode initialization. This slow equation system models the low frequency rotational atmospheric motions; there are no solutions corresponding to gravity waves. The prognostic element of the system is an equation expressing the conservation of potential vorticity. The slow equations differ from the general balance system at second order in the Rossby number, and are free from the spurious solutions found in that system. Integration of a barotropic model with the slow equations shows them to be highly accurate when compared with the primitive equations. Since the slow equation model has no high frequency solutions and is free from data shock, it may be useful for continuous assimilation of observational data. Copyright © 1989 Royal Meteorological Society"
"7004605826;7005548544;","The causation and sensitivity of the northern winter planetary waves.",1985,"10.1175/1520-0469(1985)042<0724:tcasot>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022226671&doi=10.1175%2f1520-0469%281985%29042%3c0724%3atcasot%3e2.0.co%3b2&partnerID=40&md5=08010a1565fdea0cc89f020eebed849b","We have made high resolution calculations of the wintertime stationary atmospheric response to planetary scale topographic and thermal forcings. A numerical model has been used that solves the spherical primitive equations linearized about observed zonal wind and temperature fields. The model's lid is placed high enough so that spurious reflections do not affect the results. Considerable attention has been paid to numerical accuracy.-from Authors"
"7801489016;7201772478;","A numerical study of the development mechanisms of polar lows.",1985,"10.3402/tellusa.v37i5.11689","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022167261&doi=10.3402%2ftellusa.v37i5.11689&partnerID=40&md5=9b06414e22e326b70c8aef98e2d1582f","Two well-documented polar lows, one occurring in the Atlantic Ocean and the other in the Pacific Ocean, are modeled 'numerically'. These numerical results are compared with our analytic results in order to determine how the effects of nonlinearity and more complete physics may modify our tentative conclusions. The numerical model used in this study is The Pennsylvania State University/National Center for Atmospheric Research, three-dimensional primitive equation mesoscale model with a high-resolution planetary boundary-layer parameterization and moist physics.-from Authors"
"31067496800;15765007300;52263850600;13406399300;7202192265;36992744000;36179077700;57201880425;6603565405;6602230359;6603218374;7202208382;8696068200;57193170776;57192468922;11939929300;23967739600;36762751600;7801332133;7202447177;6603247427;16242524600;7004676489;55189671700;6701335949;25647939800;56520853700;55622628300;7004134577;55793350400;26431637400;","DCMIP2016: A review of non-hydrostatic dynamical core design and intercomparison of participating models",2017,"10.5194/gmd-10-4477-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85037726783&doi=10.5194%2fgmd-10-4477-2017&partnerID=40&md5=0c72fe90386045ee1d67327c0f5212d6","Atmospheric dynamical cores are a fundamental component of global atmospheric modeling systems and are responsible for capturing the dynamical behavior of the Earth's atmosphere via numerical integration of the Navier-Stokes equations. These systems have existed in one form or another for over half of a century, with the earliest discretizations having now evolved into a complex ecosystem of algorithms and computational strategies. In essence, no two dynamical cores are alike, and their individual successes suggest that no perfect model exists. To better understand modern dynamical cores, this paper aims to provide a comprehensive review of 11 non-hydrostatic dynamical cores, drawn from modeling centers and groups that participated in the 2016 Dynamical Core Model Intercomparison Project (DCMIP) workshop and summer school. This review includes a choice of model grid, variable placement, vertical coordinate, prognostic equations, temporal discretization, and the diffusion, stabilization, filters, and fixers employed by each system."
"7003532926;55008428200;6506333296;6603752490;6602679900;6507368982;6602333928;56828803500;7006113053;","Simulation of the present-day climate with the climate model INMCM5",2017,"10.1007/s00382-017-3539-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011674776&doi=10.1007%2fs00382-017-3539-7&partnerID=40&md5=b005cf59cae165548aa6790890001b50","In this paper we present the fifth generation of the INMCM climate model that is being developed at the Institute of Numerical Mathematics of the Russian Academy of Sciences (INMCM5). The most important changes with respect to the previous version (INMCM4) were made in the atmospheric component of the model. Its vertical resolution was increased to resolve the upper stratosphere and the lower mesosphere. A more sophisticated parameterization of condensation and cloudiness formation was introduced as well. An aerosol module was incorporated into the model. The upgraded oceanic component has a modified dynamical core optimized for better implementation on parallel computers and has two times higher resolution in both horizontal directions. Analysis of the present-day climatology of the INMCM5 (based on the data of historical run for 1979–2005) shows moderate improvements in reproduction of basic circulation characteristics with respect to the previous version. Biases in the near-surface temperature and precipitation are slightly reduced compared with INMCM4 as well as biases in oceanic temperature, salinity and sea surface height. The most notable improvement over INMCM4 is the capability of the new model to reproduce the equatorial stratospheric quasi-biannual oscillation and statistics of sudden stratospheric warmings. © 2017, Springer-Verlag Berlin Heidelberg."
"36660575800;57209470805;55351188700;7004974000;55329402900;57193079972;6507391636;55081793600;6602143017;57212184340;57198886794;7203062717;6506736298;55841327700;23666237800;48261098800;55168502600;56575903900;26534538800;57209469769;54790711600;57209188201;57210957523;55823994500;55962164400;57190439142;57209466846;56003449400;55896877200;57209474671;7003287989;56884317100;57189891225;15076805100;57209474092;57200685547;57209475168;","Saudi-KAU Coupled Global Climate Model: Description and Performance",2017,"10.1007/s41748-017-0009-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031928909&doi=10.1007%2fs41748-017-0009-7&partnerID=40&md5=f780eead4cb5e51893f57406f5283092","Background: A new coupled global climate model (CGCM) has been developed at the Center of Excellence for Climate Change Research (CECCR), King Abdulaziz University (KAU), known as Saudi-KAU CGCM. Purpose: The main aim of the model development is to generate seasonal to subseasonal forecasting and long-term climate simulations. Methods: The Saudi-KAU CGCM currently includes two atmospheric dynamical cores, two land components, three ocean components, and multiple physical parameterization options. The component modules and parameterization schemes have been adopted from different sources, and some have undergone modifications at CECCR. The model is characterized by its versatility, ease of use, and the physical fidelity of its climate simulations, in both idealized and realistic configurations. A description of the model, its component packages, and parameterizations is provided. Results: Results from selected configurations demonstrate the model’s ability to reasonably simulate the climate on different time scales. The coupled model simulates El Niño-Southern Oscillation (ENSO) variability, which is fundamental for seasonal forecasting. It also simulates Madden-Julian Oscillation (MJO)-like disturbances with features similar to observations, although slightly weaker. Conclusions: The Saudi-KAU CGCM ability to simulate the ENSO and the MJO suggests that it is capable of making useful predictions on subseasonal to seasonal timescales. © 2017, The Author(s)."
"31067496800;55394412800;15765007300;7004069241;","A proposed baroclinic wave test case for deep- and shallow-atmosphere dynamical cores",2014,"10.1002/qj.2241","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904958115&doi=10.1002%2fqj.2241&partnerID=40&md5=66d4ecd7afb68d2bd0c7d4094e938eee","Idealised studies of key dynamical features of the atmosphere provide insight into the behaviour of atmospheric models. A very important, well understood, aspect of midlatitude dynamics is baroclinic instability. This can be idealised by perturbing a vertically sheared basic state in geostrophic and hydrostatic balance. An unstable wave mode then results with exponential growth (due to linear dynamics) in time until, eventually, nonlinear effects dominate and the wave breaks. A new, unified, idealised baroclinic instability test case is proposed. This improves on previous ones in three ways. First, it is suitable for both deep- and shallow-atmosphere models. Second, the constant surface pressure and zero surface geopotential of the basic state makes it particularly well-suited for models employing a pressure- or height-based vertical coordinate. Third, the wave triggering mechanism selectively perturbs the rotational component of the flow; this, together with a vertical tapering, significantly improves dynamic balance. © 2013 Royal Meteorological Society."
"57188966058;7202048112;57210180554;6602858513;7406243250;","Atmospheric moisture budget and spatial resolution dependence of precipitation extremes in aquaplanet simulations",2014,"10.1175/JCLI-D-13-00468.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900387649&doi=10.1175%2fJCLI-D-13-00468.1&partnerID=40&md5=9f553d28e4d1c83569319a846aa0a6dd","This study investigates the moisture budgets and resolution dependency of precipitation extremes in an aquaplanet framework based on the Community Atmosphere Model, version 4 (CAM4). Moisture budgets from simulations using two different dynamical cores, the Model for Prediction Across Scales-Atmosphere (MPAS-A) and High Order Method Modeling Environment (HOMME), but the same physics parameterizations suggest that during precipitation extremes the intensity of precipitation is approximately balanced by the vertical advective moisture transport. The resolution dependency in extremes from simulations at their native grid resolution originates from that of vertical moisture transport, which is mainly explained by changes in dynamics (related to vertical velocity ω) with resolution. When assessed at the same grid scale by areaweighted averaging the fine-resolution simulations to the coarse grids, simulations with either dynamical core still demonstrate resolution dependency in extreme precipitation with no convergence over the tropics, but convergence occurs at a wide range of latitudes over the extratropics. The use of lower temporal frequency data (i.e., daily vs 6 hourly) reduces the resolution dependency. Although thermodynamic (moisture) changes become significant in offsetting the effect of dynamics when assessed at the same grid scale, especially over the extratropics, changes in dynamics with resolution are still large and explain most of the resolution dependency during extremes. This suggests that the effects of subgrid-scale variability of v and vertical moisture transport during extremes are not adequately parameterized by the model at coarse resolution. The aquaplanet framework and analysis described in this study provide an important metric for assessing sensitivities of cloud parameterizations to spatial resolution and dynamical cores under extreme conditions. © 2014 American Meteorological Society."
"42661692800;7202048112;6506328135;6508063123;57210180554;6602858513;7406243250;","The dependence of ITCZ structure on model resolution and dynamical core in aquaplanet simulations",2014,"10.1175/JCLI-D-13-00269.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896075417&doi=10.1175%2fJCLI-D-13-00269.1&partnerID=40&md5=b9529dbe1094c5f5a0091b3aec8fddc0","Aquaplanet simulations using the Community Atmosphere Model, version 4 (CAM4), with the Model for Prediction Across Scales-Atmosphere (MPAS-A) and High-Order Method Modeling Environment (HOMME) dynamical cores and using zonally symmetric sea surface temperature (SST) structure are studied to understand the dependence of the intertropical convergence zone (ITCZ) structure on resolution and dynamical core. While all resolutions in HOMME and the low-resolution MPAS-A simulations give a single equatorial peak in zonal mean precipitation, the high-resolution MPAS-A simulations give a double ITCZ with precipitation peaking around 28-38 on either side of the equator. This study reveals that the structure of ITCZ is dependent on the feedbacks between convection and large-scale circulation. It is shown that the difference in specific humidity betweenHOMMEandMPAS-A can lead to different latitudinal distributions of the convective available potential energy (CAPE) by influencing latent heat release by clouds and the upper-tropospheric temperature. With lower specific humidity, the high-resolution MPAS-A simulation has CAPE increasing away from the equator that enhances convection away from the equator and, through a positive feedback on the circulation, results in a double ITCZ structure. In addition, it is shown that the dominance of antisymmetric waves in the model is not enough to cause double ITCZ, and the lateral extent of equatorial waves does not play an important role in determining the width of the ITCZ but rather the latter may influence the former. © 2014 American Meteorological Society."
"26430995400;56850959100;","Macroturbulent equilibration in a thermally forced primitive equation system",2012,"10.1175/JAS-D-11-041.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857199990&doi=10.1175%2fJAS-D-11-041.1&partnerID=40&md5=54ed76051a1bfaa4394c8020f1aa4a5b","A major question for climate studies is to quantify the role of turbulent eddy fluxes in maintaining the observed ocean-atmosphere state. It has been argued that eddy fluxes keep the midlatitude atmosphere in a state that is marginally critical to baroclinic instability, which provides a powerful constraint on the response of the atmosphere to changes in external forcing. No comparable criterion appears to exist for the ocean. This is particularly surprising for the Southern Ocean, a region whose dynamics are very similar to the midlatitude atmosphere, but observations and numerical models suggest that the currents are supercritical. This paper aims to resolve this apparent contradiction using a combination of theoretical considerations and eddy-resolving numerical simulations. It is shown that both marginally critical and supercritical mean states can be obtained in an idealized diabatically forced (and thus atmosphere-like) Boussinesq system, if the thermal expansion coefficient is varied from large atmosphere-like values to small oceanlike values. The argument is made that the difference in the thermal expansion coefficient dominantly controls the difference in the deformation scale between the two fluids and ultimately renders eddies ineffective in maintaining a marginally critical state in the limit of small thermal expansion coefficients. © 2012 American Meteorological Society."
"9244992800;7003961970;7004060399;","The effect of topography on storm-track intensity in a relatively simple general circulation model",2009,"10.1175/2008JAS2742.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549132948&doi=10.1175%2f2008JAS2742.1&partnerID=40&md5=40cd6ce01485a8f2be1b1955a8e80b3d","The effect of topography on storm-track intensity is examined with a set of primitive equation model integrations. This effect is found to be crucially dependent on the latitudinal structure of the background flow impinging on the topography. If the background flow consists of a weak double jet, higher topography leads to an intensification of the storm track downstream of the topography, consistent with enhanced baroclinicity in that region. However, if the background flow consists of a strong single jet, topography weakens the storm track, despite the fact that the baroclinicity downstream of the topography is again enhanced. The different topographic impact results from the different wave packets in the two background flows. For a weak double-jet state, wave packets tend to radiate equatorward and storm-track eddies grow primarily at the expense of local baroclinicity. In contrast, for a strong single-jet state, wave packets persistently propagate in the zonal direction and storm tracks are affected not only by local baroclinicity but also by far-upstream disturbances via downstream development. It is the reduction of the latter by the topography that leads to weaker storm tracks in a strong single-jet state. The implications of these findings for Northern Hemisphere storm tracks are also discussed. © 2009 American Meteorological Society."
"7202607288;7006747377;35495909800;35371325600;35475926200;7004678728;6603738005;24167615900;23479549200;","Reconstruction and simulation of stratospheric ozone distributions during the 2002 austral winter",2005,"10.1175/JAS-3336.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-16644383844&doi=10.1175%2fJAS-3336.1&partnerID=40&md5=853c2611767221cd9d9858508be9fed9","Satellite-based solar occultation measurements during the 2002 austral winter have been used to reconstruct global, three-dimensional ozone distributions. The reconstruction method uses correlations between potential vorticity and ozone to derive ""proxy"" distributions from the geographically limited occultation observations. Ozone profiles from the Halogen Occultation Experiment (HALOE), the Polar Ozone and Aerosol Measurement III (POAM III), and the Stratospheric Aerosol and Gas Experiment II and III (SAGE II and III) are incorporated into the analysis. Because this is one of the first uses of SAGE III data in a scientific analysis, preliminary validation results are shown. The reconstruction method is described, with particular emphasis on uncertainties caused by noisy and/or multivalued correlations. The evolution of the solar occultation data and proxy ozone fields throughout the winter is described, and differences with respect to previous winters are characterized. The results support the idea that dynamical forcing early in the 2002 winter influenced the morphology of the stratosphere in a significant and unusual manner, possibly setting the stage for the unprecedented major stratospheric warming in late September. The proxy is compared with ozone from mechanistic, primitive equation model simulations of passive ozone tracer fields during the time of the warming. In regions where chemistry is negligible compared to transport, the model and proxy ozone fields agree well. The agreement between, and changes in, the large-scale ozone fields in the model and proxy indicate that transport processes, particularly enhanced poleward transport and mixing, are the primary cause of ozone changes through most of the stratosphere during this unprecedented event. The analysis culminates with the calculation of globally distributed column ozone during the major warming, showing quantitatively how transport of low-latitude air to the polar region in the middle stratosphere led to the diminished ozone hole in 2002. © 2005 American Meteorological Society."
"7402478173;6504719808;7102322882;","A new general circulation model of Jupiter's atmosphere based on the UKMO Unified Model: Three-dimensional evolution of isolated vortices and zonal jets in mid-latitudes",2004,"10.1016/j.pss.2003.06.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1442311844&doi=10.1016%2fj.pss.2003.06.006&partnerID=40&md5=14d516b32e6efc4557d33bd056421014","We have been developing a new three-dimensional general circulation model for the stratosphere and troposphere of Jupiter based on the dynamical core of a portable version of the Unified Model of the UK Meteorological Office. Being one of the leading terrestrial GCMs, employed for operational weather forecasting and climate research, the Unified Model has been thoroughly tested and performance tuned for both vector and parallel computers. It is formulated as a generalized form of the standard primitive equations to handle a thick atmosphere, using a scaled pressure as the vertical coordinate. It is able to accurately simulate the dynamics of a three-dimensional fully compressible atmosphere on the whole or a part of a spherical shell at high spatial resolution in all three directions. Using the current version of the GCM, we examine the characteristics of the Jovian winds in idealized configurations based on the observed vertical structure of temperature. Our initial focus is on the evolution of isolated eddies in the mid-latitudes. Following a brief theoretical investigation of the vertical structure of the atmosphere, limited-area cyclic channel domains are used to numerically investigate the nonlinear evolution of the mid-latitude winds. First, the evolution of deep and shallow cyclones and anticyclones are tested in the atmosphere at rest to identify a preferred horizontal and vertical structure of the vortices. Then, the dependency of the migration characteristics of the vortices are investigated against modelling parameters to find that it is most sensitive to the horizontal diffusion. We also examine the hydrodynamical stability of observed subtropical jets in both northern and southern hemispheres in the three-dimensional nonlinear model as initial value problems. In both cases, it was found that the prominent jets are unstable at various scales and that vorteces of various sizes are generated including those comparable to the White Ovals and the Great Red Spot. © 2003 Elsevier Ltd. All rights reserved."
"6701843355;","What caused the onset of the 1997-98 El Niño?",2000,"10.1175/1520-0493(2000)128<2601:wctoot>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033827963&doi=10.1175%2f1520-0493%282000%29128%3c2601%3awctoot%3e2.0.co%3b2&partnerID=40&md5=b4bf90da300939baa09a5e0591f17f34","There has been intense debate about the causes of the 1997-98 El Niño. One side sees the obvious intense westerly wind events as the main cause for the exceptional heating in summer 1997, the other emphasizes slower oceanic processes. A quantitative analysis of all factors contributing to the onset of this El Niño is presented here. Specifically, the Niño-3 index in the Hamburg Ocean Primitive Equation Model OGCM at 1 June 1997 is decomposed into contributions from the fluxes and initial state at six months' lead time. The initial-state thermal anomalies contribute about 40% compared with an average year, and the wind stress about 50% Compared with the previous year, in which no El Niño developed, the main difference is in the zonal wind stress. This contribution is concentrated at the time and place of the strong westerly wind events in December 1996, and March and April 1997. As westerly wind events are difficult to predict, this limited the predictability of the onset of this El Niño."
"6701843355;6603829010;6603456128;7102290938;55911428100;","Tracking down the ENSO delayed oscillator with an adjoint OGCM",1999,"10.1175/1520-0493(1999)127<1477:tdtedo>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032730920&doi=10.1175%2f1520-0493%281999%29127%3c1477%3atdtedo%3e2.0.co%3b2&partnerID=40&md5=35c14c4dbe3dfd70bc41c75543906b88","According to the delayed-oscillator picture of ENSO, a positive SST anomaly in the eastern tropical Pacific will cause westerly wind anomalies closer to the date line to first give a positive feedback, and later, via planetary wave reflection at the western boundary, a negative feedback. The aim of this study is to follow a chain of sensitivities that lead to a delayed-oscillator mechanism in a general circulation model. To this end, the adjoint of such an ocean model is used for studying sensitivities of ENSO indices. The ocean model used in this study is the Hamburg Ocean Primitive Equation (HOPE) ocean general circulation model. Its adjoint has been constructed using the Adjoint Model Compiler. Applied to a scalar function computed with a forward model run, an adjoint run goes back in time and calculates sensitivities as the derivatives of this function to forcing fields or ocean state variables at earlier times. Results from six adjoint runs are reported, tracing the sensitivities of the NINO3 and NINO3.4 indices in October 1987, December 1987, and December 1988, as simulated by a Pacfic-only version of HOPE forced by ECHAM-3 fluxes. The sensitivities to sea level can be followed back in time for more than a year. They are nonlocal: patterns propagate back in time that are identified as adjoint Kelvin and n = 1, 2, and 3 Rossby waves, with speeds compatible with those obtained from model density profiles. Both the first and the second baroclinic modes seem to play a role. In contrast, the model sensitivities to heat flux, zonal surface currents, and SST are local and decay in about a month. The sensitivities to the wind stress agree with the wave interpretation of the sea-level sensitivities, but only the n = 1 Rossby wave is visible. Going back in time, the sensitivity to westerly anomalies along the equator changes sign, in agreement with the delayed-oscillator picture. Finally, a statistical atmosphere model is used to convert sensitivities to wind stress at a given time to sensitivities to SST through the atmosphere at that time. Focusing on the sensitivities to the ENSO index region itself at an earlier time then closes the circle. These sensitivities have a natural interpretation as delayed-oscillator coefficients and show the expected behavior of a positive sensitivity in the recent past changing to a negative sensitivity at longer lags. However, the strength of these feedbacks, and hence the relevance of this mechanism in ENSO simulated in HOPE, cannot be determined accurately."
"6602334969;6701550654;7003586963;","A sigma-coordinate primitive equation model for studying the circulation in the South Atlantic. Part II: Meridional transports and seasonal variability",1998,"10.1016/S0967-0637(97)00087-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032052334&doi=10.1016%2fS0967-0637%2897%2900087-3&partnerID=40&md5=fbb2112dd1b33bf5f802f41fc6e46577","The mean and seasonal variability of the circulation and meridional heat transport in the South Atlantic are investigated using a set of numerical experiments. The primitive equation model uses a topography-following (sigma) coordinate. The model domain is limited to the South Atlantic basin. Artificial boundaries at Drake Passage, between Brazil and Angola, and between South Africa and Antarctica are treated as open boundaries. Finally, recent and self-consistent estimates of seasonal fluxes are used to define a model-dependent atmospheric forcing. Quasi-diagnostic simulations forced by constant climatological winds are first conducted to determine the sensitivity of model solutions to bottom topography smoothing, and to diagnose meridional fluxes from a mass field that is relaxed to the annual climatology of Levitus (1982). Model results show good agreement with known climatological circulation features in this basin, especially in the Confluence Region, where coarse resolution models usually give smooth structures. Sensitivity studies show that the more detailed features of the circulation are influenced by the model bathymetry. The model simulates a meridional circulation whose upper branch (the return flow that balances the southward flow of North Atlantic Deep Water) is composed of Intermediate (IW) and Thermocline (TW) Waters. The transport of IW is found to be predominant, and the value of meridional heat transport consequently falls within the low estimates. We notice that the meridional heat balance is sensitive to the position of the Confluence. When this region occurs too far south, the amount of IW contributing to the return flow of the overturning cell is reduced. Prognostic simulations forced by seasonal winds and heat fluxes are studied to quantify the impact of wind forcing on the circulation in the South Atlantic. Particular attention is focused on meridional transports at 30°S. Analysis of the mean annual circulation confirms that the upper branch of the meridional circulation is predominantly Composed of IW (9 Sv), rather than TW (5.3 Sv). The mean transport of the lower branch is 16 Sv, in agreement with recent estimates by Schlitzer (1996). The annual meridional heat transport (0.29 PW) is still within the low estimates, but agrees well with other estimates that give a dominant role to IW (Rintoul, 1991). Original results also concern the variability of the upper branch of the meridional circulation. It is shown that the wind creates seasonal variability in the Subtropical Gyre, which has a marked impact on the water mass balance in the South Atlantic. In winter, a large convergence to the north of the Subtropical Gyre (27°S) reduces the northward flow of IW, whereas stronger Ekman pumping favors an equatorward transport of TW. In summer, this convergence disappears and a larger transport of IW is allowed. Thus a more complex scheme is proposed for the meridional circulation, in which local wind forcing in the South Atlantic Basin has a significant role in preconditioning the surface waters of the global overturning cell."
"56402758400;55778380300;19640035700;23989037500;","Revisiting the Phase Curves of WASP-43b: Confronting Re-analyzed Spitzer Data with Cloudy Atmospheres",2018,"10.3847/1538-3881/aaaebc","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045568706&doi=10.3847%2f1538-3881%2faaaebc&partnerID=40&md5=22538597cd8fac35200b6b57934f1840","Recently acquired Hubble and Spitzer phase curves of the short-period hot Jupiter WASP-43b make it an ideal target for confronting theory with data. On the observational front, we re-analyze the 3.6 and 4.5 μm Spitzer phase curves and demonstrate that our improved analysis better removes residual red noise due to intra-pixel sensitivity, which leads to greater fluxes emanating from the nightside of WASP-43b, thus reducing the tension between theory and data. On the theoretical front, we construct cloud-free and cloudy atmospheres of WASP-43b using our Global Circulation Model (GCM), THOR, which solves the non-hydrostatic Euler equations (compared to GCMs that typically solve the hydrostatic primitive equations). The cloud-free atmosphere produces a reasonable fit to the dayside emission spectrum. The multi-phase emission spectra constrain the cloud deck to be confined to the nightside and have a finite cloud-top pressure. The multi-wavelength phase curves are naturally consistent with our cloudy atmospheres, except for the 4.5 μm phase curve, which requires the presence of enhanced carbon dioxide in the atmosphere of WASP-43b. Multi-phase emission spectra at higher spectral resolution, as may be obtained using the James Webb Space Telescope, and a reflected-light phase curve at visible wavelengths would further constrain the properties of clouds in WASP-43b. © 2018. The American Astronomical Society. All rights reserved."
"16636807900;","Vertical Velocity in the Gray Zone",2017,"10.1002/2017MS001059","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85031728098&doi=10.1002%2f2017MS001059&partnerID=40&md5=6daa22596ceb7eead5abbb95986928dd","We describe how convective vertical velocities (Formula presented.) vary in the “gray zone” of horizontal resolution, using both hydrostatic and nonhydrostatic versions of GFDL's FV3 dynamical core, as well as analytical solutions to the equations of motion. We derive a simple criterion (based on parcel geometries) for a model to resolve convection, and find that (Formula presented.) resolution can be required for convergence of (Formula presented.). We also find, both numerically and analytically, that hydrostatic systems overestimate (Formula presented.), by a factor of 2–3 in the convection-resolving regime. This overestimation is simply understood in terms of the “effective buoyancy pressure” of Jeevanjee and Romps (2015, 2016). © 2017. The Authors."
"55823047900;8977001000;","Evaluating low-cloud simulation from an upgraded multiscale modeling framework model. Part I: Sensitivity to spatial resolution and climatology",2013,"10.1175/JCLI-D-12-00200.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881630278&doi=10.1175%2fJCLI-D-12-00200.1&partnerID=40&md5=307a655812d4ae3b02c6c60a6ad1ac6a","The multiscale modeling framework, which replaces traditional cloud parameterizations with a 2D cloudresolving model (CRM) in each atmospheric column, is a promising approach to climate modeling. TheCRM component contains an advanced third-order turbulence closure, helping it to better simulate low-level clouds. In this study, two simulations are performed with 1.98 3 2.58 grid spacing but they differ in the vertical resolution. The number of model layers below 700 hPa increases from 6 in one simulation (IP-6L) to 12 in another (IP-12L) to better resolve the boundary layer. The low-cloud horizontal distribution and vertical structures in IP-12L are more realistic and its global mean is higher than in IP-6L and closer to that of CloudSat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) observations. The spatial patterns of tropical precipitation are significantly improved; for example, a single intertropical convergence zone (ITCZ) in the Pacific, instead of double ITCZs in an earlier study that used coarser horizontal resolution and a different dynamical core in its host general circulation model (GCM), and the intensity of the South Pacific convergence zone (SPCZ), and the ITCZ in the Atlantic is more realistic. Many aspects of the global seasonal climatology agree well with observations except for excessive precipitation in the tropics. In terms of spatial correlations and patterns in the tropical/subtropical regions, most surface/vertically integrated properties show greater improvement over the earlier simulation than that with lower vertical resolution. The relationships between low-cloud amount and several large-scale properties are consistent with those observed in five low-cloud regions. There is an imbalance in the surface energy budget, which is an aspect of the model that needs to be improved in the future. © 2013 American Meteorological Society."
"36992744000;15765007300;","An analytic vortex initialization technique for idealized tropical cyclone studies in AGCMs",2011,"10.1175/2010MWR3488.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79951919251&doi=10.1175%2f2010MWR3488.1&partnerID=40&md5=1641a1afe0d2f4c398ed858ba6b62966","The paper discusses the design of idealized tropical cyclone experiments in atmospheric general circulation models (AGCMs). The evolution of an initially weak, warm-core vortex is investigated over a 10-day period with varying initial conditions that include variations of the maximum wind speed and radius of maximum wind. The initialization of the vortex is built upon prescribed 3D moisture, pressure, temperature, and velocity fields that are embedded into tropical environmental conditions. The initial fields are in exact hydrostatic and gradient-wind balance in an axisymmetric form. The formulation is then generalized to provide analytic initial conditions for an approximately balanced vortex in AGCMs with height-based vertical coordinates. An extension for global models with pressure-based vertical coordinates is presented. The analytic initialization technique can easily be implemented on any AGCM computational grid. The characteristics of the idealized tropical cyclone experiments are illustrated in high-resolution model simulations with the Community Atmosphere Model version 3.1 (CAM3.1) developed at the National Center for Atmospheric Research. The finite-volume dynamical core in CAM 3.1 with 26 vertical levels is used, and utilizes an aquaplanet configuration with constant sea surface temperatures of 29°C. The impact of varying initial conditions and horizontal resolutions on the evolution of the tropical cyclone-like vortex is investigated. Identical physical parameterizations with a constant parameter set are used at all horizontal resolutions. The sensitivity studies reveal that the initial wind speed and radius of maximum wind need to lie above a threshold to support the intensification of the analytic initial vortex at horizontal grid spacings of 0.5° and 0.25° (or 55 and 28 km in the equatorial regions). The thresholds lie between 15 and 20 m s-1 with a radius of maximum wind of about 200-250 km. In addition, a convergence study with the grid spacings 1.0°, 0.5°, 0.25°, and 0.125° (or 111, 55, 28, and 14 km) shows that the cyclone gets more intense and compact with increasing horizontal resolution. The 0.5°, 0.25°, and 0.125° simulations exhibit many tropical cyclone-like characteristics such as a warm-core, low-level wind maxima, a slanted eyewall-like vertical structure and a relatively calm eye. The 0.125° simulation even starts to resolve spiral rainbands and reaches maximum wind speeds of about 72-83 m s-1 at low levels. These wind speeds are equivalent to a category-5 tropical cyclone on the Saffir-Simpson hurricane scale. It is suggested that the vortex initialization technique can be used as an idealized tool to study the impact of varying resolutions, physical parameterizations, and numerical schemes on the simulation and representation of tropical cyclone-like vortices in global atmospheric models. © 2011 American Meteorological Society."
"57195881858;","Simulations of subtropical cyclones in a baroclinic channel model",2010,"10.1175/2010JAS3411.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77958612591&doi=10.1175%2f2010JAS3411.1&partnerID=40&md5=75ce2c637c97b442cac7dd73af02bfb9","The present study considers a variety of cyclone developments that occur in an idealized, baroclinic channel model featuring full condensation heating effects over an ocean with prescribed sea surface temperature variation. The geostrophic basic-state jet is specified by the tropopause shape, and horizontal shear is included by specifying the meridional variation of zonal wind on the lower boundary. The horizontal shear induces anticyclonic wave breaking of baroclinic waves. Normal mode perturbations are computed using a ""fake-dry"" version of the model but integrated forward using full physics. Low-latitude moist convection is particularly strong in simulations with strong surface easterlies that destabilize the troposphere through water vapor fluxes from the ocean surface. Deep convection produces a locally elevated dynamic tropopause and an associated anticyclone. This modified zonal flow supports moist baroclinic instability. The resulting cyclones, identified as subtropical cyclones, occur in deep westerly vertical wind shear but are nearly devoid of lower-tropospheric baroclinicity initially. These systems are distinguished from baroclinically dominated secondary cyclones that also form at relatively low latitudes in the simulations. For weak jets and strong subtropical surface easterlies, subtropical cyclone development dominates formation on the midlatitude jet. For strong westerly jets or weak horizontal shear, the situation is reversed and the midlatitude baroclinic wave can help or hinder the ultimate intensification of the subtropical cyclone. The similarity of this cross-latitude influence to the extratropical transition of tropical cyclones is noted. © 2010 American Meteorological Society."
"23020433600;6603460713;7201437088;","Impact of the Eastern Weddell ice shelves on water masses in the eastern Weddell Sea",2006,"10.1029/2005JC003212","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34447544270&doi=10.1029%2f2005JC003212&partnerID=40&md5=316b04fe6623ace975f3a8a216bfc8db","We use a primitive equation Ocean General Circulation Model to simulate the ocean circulation regime in the Eastern Weddell Sea. The computer model ROMBAX (Revisited Ocean Model based on Bryan And Cox) is an improved version of an earlier ocean model, which has been developed to allow the simulation of the flow regime in ice shelf covered regions. The Eastern Weddell Ice Shelf (EWIS) region is of particular importance because of its narrow continental shelf and its location at the inflow of water masses from the east into the southern Weddell Sea. We have compared the simulated flow pattern and water properties in the EWIS region with the available sparse observations. While the general observed structure of temperature and salinity is reproduced, the model tends to overestimate the on-shore flow of warm deep waters. This discrepancy is not large enough to seriously influence the ice shelf - ocean interaction, which is in good agreement with estimates based on field observations. The mean net melt rate is found to be 0.88 in yr-1 (2.1 mSv) and has a strong seasonal cycle. Sensitivity studies with different ice shelf configurations (no melting, no ice shelf, closed cavity) show strong impacts on the water mass properties in the EWIS region, with up to 0.7°C difference in temperature and 0.05 in salinity relative to the control run. Our results suggest that the EWIS region is of substantial importance to water mass preconditioning and formation in the Weddell Sea, although no deep or bottom water formation occurs in the eastern Weddell Sea directly. Copyright 2006 by the American Geophysical Union."
"56212576300;35554288100;7402598368;","Effects of bottom friction on nonlinear equilibration of an oceanic baroclinic jet",2004,"10.1175/1520-0485(2004)034<0416:EOBFON>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842810921&doi=10.1175%2f1520-0485%282004%29034%3c0416%3aEOBFON%3e2.0.CO%3b2&partnerID=40&md5=dc7ca48a4ad5fcbe0d3e73e71e952c60","Bottom friction is an important sink of energy in the ocean. Indeed, high-resolution ocean models need bottom friction to achieve a satisfactory kinetic energy level at equilibrium. However, bottom friction has also subtle and discriminating effects on the different energy transfers and therefore on the 3D structure of the flow, some of which have to be clarified. In this study, those effects on an unstable baroclinic jet are reexamined using a primitive equation model. As in previous studies using quasigeostrophic models, it was found that bottom friction strongly affects the barotropic mode whereas the baroclinic modes are weakly changed. The new result is that bottom friction yields a significant space-scale selection. Analysis of the dynamics reveals strong agreement with previous quasigeostrophic studies at the mesoscale in the interior but differences in the eddy field at small scales close to the surface. A rationalization of these results is proposed by a comparison with preceding atmospheric studies. It is shown that the ""barotropic governor"" of James and Gray is not active in ocean simulations and that the scale selection induced by bottom friction is primarily induced by nonlinear interactions in the three-dimensional structure of the eddy field. © 2004 American Meteorological Society."
"57054407300;7004643321;","Numerical simulation of the Gulf Stream System: The Loop Current and the deep circulation",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037670924&partnerID=40&md5=b2cc2cd8849d98073be516a2713266d8","The Loop Current and the deep circulation in the Gulf of Mexico are numerically investigated by a primitive equation, sigma coordinate ocean model with realistic surface fluxes obtained from an atmospheric forecast model. A deep cyclonic circulation, bounded by the deep basin in the eastern Gulf of Mexico, is spun up by the Loop Current; the deep cyclonic circulation is coincident with a southward current of the Loop Current eastern limb and weakens after Loop Current ring separation and cessation of the southward current. The anticyclonic, semienclosed Loop Current also induces anticyclonic lower layer columnar eddies in the eastern gulf. These lower layer eddies decouple from the upper layer Loop Current. The westward translation speed of a Loop Current ring is about 2.16-5.18 km d-1; the lower layer eddies have a higher speed and lead the rings into the central gulf. The time-averaged surface circulation of the Gulf of Mexico basin is anticyclonic, mainly because of the transport of anticyclonic vorticity by Loop Current rings in the surface layer an average lower layer cyclonic circulation occurs along the continental slope of the basin."
"57197390302;7004332887;57111001300;36077992900;7005874502;","Hindcasting the NAO using diabatic forcing of a simple AGCM",2002,"10.1029/2001gl014502","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036558492&doi=10.1029%2f2001gl014502&partnerID=40&md5=846a0d729b55c2cdd5e3e9987b6375d5","A primitive equation dry atmospheric model with a rudimentary representation of the model physics is used to hindcast the winter NAO using diabatic forcing diagnosed from NCAR/NCEP reanalysis data in the period 1949-1999. Using ensembles of experiments we are able to reproduce the observed NAO index in the ensemble mean with a correlation of 0.79. By prescribing time dependent forcing only in the tropics (30°S-30°N), or only in the extra-tropics, we show that the recent upward trend in the NAO is related to tropical forcing. The implication is that coupling with the mid-latitude or Arctic ocean is not important for the trend. The model also exhibits the recent eastward shift in the sea level pressure signature of the interannual NAO variability and shows that this is associated with non-linear dynamical processes."
"6602918386;57212280726;6508004743;6603665315;","Sensitivity of tropical storms simulated by a general circulation model to changes in cumulus parametrization",2001,"10.1256/smsqj.57102","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035066783&doi=10.1256%2fsmsqj.57102&partnerID=40&md5=ea0709b7c19270e98544bf0096fef655","A number of recent studies have examined the statistics of tropical storms simulated by general circulation models (GCMs) forced by observed sea surface temperatures. Many GCMs have demonstrated an ability to simulate some aspects of the observed interannual variability of tropical storms, in particular, variability in storm frequency. This has led to nascent attempts to use GCMs as part of programs to produce operational seasonal forecasts of tropical-storm numbers. In this study, the sensitivity of the statistics of GCM-simulated tropical storms to changes in the model's physical parametrizations is examined. After preliminary results indicated that these statistics were most sensitive to details of the convective parametrization, GCM simulations with identical dynamical cores but different convective parametrizations were created. The parametrizations examined included moist convective adjustment, two variants of the Arakawa-Schubert scheme, and several variants of the relaxed Arakawa-Schubert (RAS) scheme; the impact of including a shallow-convection parametrization was also examined. The simulated tropical-storm frequency, intensity, structure, and interannual variability were all found to exhibit significant sensitivities to changes in convective parametrization. A particularly large sensitivity was found when the RAS and Arakawa-Schubert parametrizations were modified to place restrictions on the production of deep convection. Climatologies of the GCM tropical atmosphere and composites of tropical storms were examined to address the question of whether the tropical-storm statistics were directly impacted on by changes in convection associated with tropical storms, or if they were indirectly affected by parametrization-induced changes in the tropical mean atmosphere. A number of results point to the latter being the primary cause. A regional hurricane model, initialized with mean states from the GCM simulation climatologies, is used to further investigate this point. Particularly compelling is the fact that versions of the RAS scheme that produce significantly less realistic simulations of tropical storms nevertheless produce a much more realistic interannual variability of storms, apparently due to an improved tropical mean climate. A careful analysis of the background convective available potential energy (CAPE) is used to suggest that this quantity is particularly relevant to the occurrence of tropical storms in the low-resolution GCMs, although this may not be the case with observations. If the tropical CAPE is too low, tropical storms in the low-resolution GCMs cannot form with realistic frequency."
"56249837700;24498795300;57194045072;","Impact of westerly wind bursts on the warm pool of the TOGA-COARE domain in an OGCM",1998,"10.1007/s003820050208","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031961487&doi=10.1007%2fs003820050208&partnerID=40&md5=c003ae4336a612a1562585dda7c30091","A primitive equation model is used to investigate the warm pool equilibrium of the tropical Pacific ocean. Attention is focused on the upper ocean. The oceanic response is described using an isothermal approach applied to warm waters contained in the TOGA-COARE domain. The heat balance shows that all the terms, atmospheric surface fluxes, advection and diffusion, operate in the heat bugdet with different time scales. Over long periods, diffusive heat fluxes transfer heat received from the atmosphere out of the warm pool trough the top of the main thermocline. Over short periods, the impact of westerly wind bursts modifies this balance: atmospheric heating is reversed, diffusion is enhanced and advective heat transports out of the warm pool operate through zonal and vertical contributions. We were able to relate the two latter processes to zonal jets and Ekman pumping, respectively. Conversely, the meridional contribution always represents a source of heat, mainly due to the tropical wind convergence. The modelling results clearly show that except during strong wind events, entrainment cooling is not an important component of the budget. The inability to remove heat is due to the salt stratification which needs to be first reduced or even destroyed by westerly wind bursts to activate heat entrainment into deeper layers. Finally, we suggest that the near zero estimate for the surface heat flux entering the warm pool may be extended to longer periods including seaosnal to interannual time scale."
"7402826517;","Dissipation dependence of the jet latitude",1997,"10.1175/1520-0442(1997)010<0176:DDOTJL>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031450389&doi=10.1175%2f1520-0442%281997%29010%3c0176%3aDDOTJL%3e2.0.CO%3b2&partnerID=40&md5=94369327c813bcceaea4eae530ae8693","Zonally averaged flows in general circulation models exhibit strong sensitivity to the strength of the surface friction, subgrid-scale diffusion, and gravity wave drag. A commonly observed effect is that the midlatitude jets shift poleward as the drag on the zonal wind is decreased. In the present two-level primitive equation model the jet moves poleward with decreasing surface friction and with increasing subgrid-scale diffusion. The barotropic component of the jet shows much greater sensitivity than does the baroclinic component. Experiments using different values of friction for the eddies and for the zonal means reveal that the jet latitude is primarily controlled by the drag on the zonal means. The shift in the latitude of the jet is derived from the altered equilibrium response of the zonal wind to forcing by eddies when the friction is changed and the change in meridional structure of the eddy momentum fluxes in response to the modified zonal wind. The latter effect is also displayed by linear baroclinic modes. © 1997 American Meteorological Society."
"7402578974;7006629146;","Inertial instability on an asymmetric low-latitude flow",1996,"10.1256/smsqj.52906","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029656410&doi=10.1256%2fsmsqj.52906&partnerID=40&md5=8b44f049fe9bd8f69e8b4027e87929bb","Both satellite data and numerical model simulations have suggested a link between propagation of planetary waves into the low-latitude middle atmosphere and the occurrence of dynamical structures with small vertical scale similar to those predicted by the theory of symmetric inertial instability. It is here argued that existing theories that consider the growth of disturbances to a basic flow that is independent of longitude are unlikely to be directly relevant to such observations. A theory is presented that takes account of longitudinal variations in the structure of the basic flow, using WKB methods and the notion of absolute instability to find localized unstable modes. In the limit of large vertical wavenumber it is demonstrated analytically that the flow is absolutely unstable. For finite vertical wavenumber the calculation is based on numerical derivation of the dispersion relation. The growth rates and the spatial structure of the unstable modes relative to the variation of the basic flow are predicted. The results are compared to those from numerical solution of the linear stability problem and with full numerical simulation in a three-dimensional primitive-equation model. It is found that under some circumstances the longitudinal variation causes the maximum growth rate to occur at finite vertical wavenumber, rather than at infinite vertical wavenumber as is the case when the basic flow is independent of longitude."
"7101630970;7201785152;","The initial value problem for tropical perturbations to a baroclinic atmosphere",1991,"10.1002/qj.49711749803","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026302114&doi=10.1002%2fqj.49711749803&partnerID=40&md5=5f7177eb636552992ce46d76b31f0e35","Large‐scale wave propagation ideas have proved extremely valuable in interpreting real and model data. These ideas have been developed in the context of barotropic models, and here the extension to baroclinic atmospheres is investigated. The dispersion of waves from an initial, large‐scale, tropical perturbation to a baroclinic basic flow is studied using a direct approach. A 15‐level, spectral, primitive equation model is integrated forward in time. Even in baroclinically unstable flows it is found that for a period, normally of order 12 days, the model yields what can be considered to be the direct response to the tropical perturbations. After this time baroclinic instability dominates. The basic flows are a resting atmosphere, a climatological westerly, an equatorial longitudinal modification to this, and a 3‐D climatological December‐February state. For the perturbations used here, equatorial Kelvin waves play only a very small role. The large‐scale equatorial Rossby wave shows only small dispersion and tends to move with a Doppler‐shifted phase speed which allows it to ‘accumulate’ to the east of an equatorial maximum of 10 ms−1 or more. Rossby wavetrains propagate into the middle and high latitude westerly regions. With the climatological flow, perturbations in the Indian Ocean‐west Pacific sector trigger a modal structure in the North Pacific and wavetrain across North America very much as barotropic theory would suggest and similar to observed Pacific‐North America (PNA) patterns. In such a flow the middle latitude waves tend to extend to the equator in the westerly regions of the east Pacific and Atlantic, in agreement with observed behaviour. Copyright © 1991 Royal Meteorological Society"
"7103242280;","Fully Lagrangian numerical solutions of unbalanced frontogenesis and frontal collapse",1989,"10.1175/1520-0469(1989)046<0717:FLNSOU>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024812763&doi=10.1175%2f1520-0469%281989%29046%3c0717%3aFLNSOU%3e2.0.CO%3b2&partnerID=40&md5=cb0220f58f4f05eecc7753082883b621","Numerical simulation has failed to answer some fundamental questions about atmospheric frontogenesis because of the artificial minimum resolved scale in grid point and spectral models alike. A fully Lagrangian primitive-equation numerical model is developed for nonturbulent, slab-symmetric flow on an f-plane. With physical position treated as an explicit function of particle label and time, and model grid deforms to follow natural changes in disturbance length scales. Exact conservation of volume and potential vorticity, as well as of basic tracer variables, is demonstrated, and details of the truncation error for energy conservation are obtained for the case of second-order central differencing in label space. The Lagrangian model is used to simulate frontogenesis by horizontal wind deformation in a dry, Boussinesq atmosphere, with no prior assumption of hydrostatic or geostrophic balance. For realistic choices of the parameters governing the rate of frontogenesis, imbalances alone are found to be insufficient to prevent frontal collapse. For small values of the normalized potential vorticity, the ageostrophic secondary circulation is weaker than in the corresponding balanced solutions, and frontal collapse is accordingly delayed. -from Author"
"25645385100;55273531500;24173130300;54919468800;7003686819;8708213500;","MicroHH 1.0: A computational fluid dynamics code for direct numerical simulation and large-eddy simulation of atmospheric boundary layer flows",2017,"10.5194/gmd-10-3145-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026878190&doi=10.5194%2fgmd-10-3145-2017&partnerID=40&md5=17c1a432fb4ad44df44719365618af37","This paper describes MicroHH 1.0, a new and open-source (www.microhh.org) computational fluid dynamics code for the simulation of turbulent flows in the atmosphere. It is primarily made for direct numerical simulation but also supports large-eddy simulation (LES). The paper covers the description of the governing equations, their numerical implementation, and the parameterizations included in the code. Furthermore, the paper presents the validation of the dynamical core in the form of convergence and conservation tests, and comparison of simulations of channel flows and slope flows against well-established test cases. The full numerical model, including the associated parameterizations for LES, has been tested for a set of cases under stable and unstable conditions, under the Boussinesq and anelastic approximations, and with dry and moist convection under stationary and time-varying boundary conditions. The paper presents performance tests showing good scaling from 256 to 32 768 processes. The graphical processing unit (GPU)-enabled version of the code can reach a speedup of more than an order of magnitude for simulations that fit in the memory of a single GPU. © 2017 Author(s)."
"7103016965;24479279900;57199451114;7003495982;18134195800;7404213432;54895140000;7402882382;6603566335;6603606681;24485834000;24764483400;6602351024;","Exploring the convective grey zone with regional simulations of a cold air outbreak",2017,"10.1002/qj.3105","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85023605283&doi=10.1002%2fqj.3105&partnerID=40&md5=e1d766067a6ca71700cf707a6c056f92","Cold air outbreaks can bring snow to populated areas and can affect aviation safety. Shortcomings in the representation of these phenomena in global and regional models are thought to be associated with large systematic cloud-related radiative flux errors across many models. In this study, nine regional models have been used to simulate a cold air outbreak case at a range of grid spacings (1–16 km) with convection represented explicitly or by a parametrization. Overall, there is more spread between model results for the simulations in which convection is parametrized when compared to simulations in which convection is represented explicitly. The quality of the simulations of both the stratocumulus and the convective regions of the domain are assessed with observational comparisons 24 h into the simulation. The stratocumulus region is not well reproduced by the models, which tend to predict open cell convection with increasing resolution rather than stratocumulus. For the convective region the model spread reduces with increased resolution and there is some improvement in comparison to observations. Comparing models that have the same physical parametrizations or dynamical core suggest that both are important for accurately reproducing this case. © 2017 Crown Copyright. Quarterly Journal of the Royal Meteorological Society © 2017 Royal Meteorological Society"
"7003821149;","On the role of eddies and surface forcing in the heat transport and overturning circulation in marginal seas",2011,"10.1175/2011JCLI4130.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053144364&doi=10.1175%2f2011JCLI4130.1&partnerID=40&md5=f2ffebfd6cd921cf3f7499578eff59bf","The factors that determine the heat transport and overturning circulation in marginal seas subject to wind forcing and heat loss to the atmosphere are explored using a combination of a high-resolution ocean circulation model and a simple conceptual model. The study is motivated by the exchange between the subpolar North Atlantic Ocean and the Nordic Seas, a region that is of central importance to the oceanic thermohaline circulation. It is shown that mesoscale eddies formed in the marginal sea play a major role in determining the mean meridional heat transport and meridional overturning circulation across the sill. The balance between the oceanic eddy heat flux and atmospheric cooling, as characterized by a nondimensional number, is shown to be the primary factor in determining the properties of the exchange. Results from a series of eddy-resolving primitive equation model calculations for the meridional heat transport, overturning circulation, density of convective waters, and density of exported waters compare well with predictions from the conceptual model over a wide range of parameter space. Scaling and model results indicate that wind effects are small and the mean exchange is primarily buoyancy forced. These results imply that one must accurately resolve or parameterize eddy fluxes in order to properly represent the mean exchange between the North Atlantic and the Nordic Seas, and thus between the Nordic Seas and the atmosphere, in climate models. © 2011 American Meteorological Society."
"36468818600;7403515168;57190658202;6701797726;6602578797;","Subsurface connections in the eastern tropical Pacific during la Nia 1999-2001 and El Nio 2002-2003",2011,"10.1029/2011JC007624","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84055211838&doi=10.1029%2f2011JC007624&partnerID=40&md5=927ded5115b84822a5cf1198c13901d0","The subsurface connections between the Equatorial Current System (ECS) and the Peru Current System (PCS) between 1999 and 2005 are investigated with a primitive-equation, eddy-resolving regional model that is forced with realistic atmospheric and lateral oceanic conditions. Specific attention is given to the 1999-2000 La Nia and the 2002-2003 El Niño. The model's skill is assessed through a comparison with satellite-derived sea level anomalies and in situ sea surface temperature time series. The model reproduces fairly well the known dynamics of the region for climatological conditions, and the numerical solution obtained for the particular 1999-2000 and 2002-2003 events presents patterns rather typical of cold and warm phases of El Niño-Southern Oscillation (ENSO). Eulerian and Lagrangian diagnoses are used to derive relevant information about the density and velocity vertical structures of the ECS and the PCS. The transports of the major currents in the region are shown to differ a lot between the 1999-2000 La Nia and the 2002-2003 El Niño. The equatorial subsurface currents transfer significantly more water into the eastern tropical Pacific during La Nia than during El Niño, whereas the Peru-Chile Undercurrent (PCUC) carries more water during El Niño. The equatorial subsurface currents, and especially the primary Southern Subsurface Countercurrent, contribute to 80% of the PCUC transport during the 1999-2000 cold phase. This ratio falls down to only 20% during the 2002-2003 warm phase. Copyright 2011 by the American Geophysical Union."
"6507175562;56867254700;57206416522;","An adjoint analysis of the meridional overturning circulation in an ocean model",2006,"10.1175/JCLI3787.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748321064&doi=10.1175%2fJCLI3787.1&partnerID=40&md5=3509ecc0f22b6d65b974dddf1d1b7aff","Using the adjoint of a fully three-dimensional primitive equation ocean model in an idealized geometry, spatial variations in the sensitivity to surface boundary forcing of the meridional overturning circulation's strength are studied. Steady-state sensitivities to diapycnal mixing, wind stress, freshwater, and heat forcing are examined. Three different, commonly used, boundary-forcing scenarios are studied, both with and without wind forcing. Almost identical circulation is achieved in each scenario, but the sensitivity patterns show major (quantitative and qualitative) differences. Sensitivities to surface forcing and diapycnal mixing are substantially larger under mixed boundary conditions, in which fluxes of freshwater and heat are supplemented by a temperature relaxation term or under flux boundary conditions, in which climatological fluxes alone drive the circulation, than under restoring boundary conditions. The sensitivity pattern to diapycnal mixing, which peaks in the Tropics is similar both with and without wind forcing. Wind does, however, increase the sensitivity to diapycnal mixing in the regions of Ekman upwelling and decreases it in the regions of Ekman downwelling. Wind stress in the Southern Oceans plays a crucial role in restoring boundary conditions, but the effect is largely absent under mixed or flux boundary conditions. The results highlight how critical a careful formulation of the surface forcing terms is to ensuring a proper response to changes in forcing in ocean models. © 2006 American Meteorological Society."
"55716319700;","Baroclinic multiple zonal jets on the sphere",2005,"10.1175/JAS3481.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344449905&doi=10.1175%2fJAS3481.1&partnerID=40&md5=5d0df3ce3af7adec09435c583526cf05","Multiple zonal jets are investigated with a two-level primitive equation model on the sphere in which both baroclinicity and planetary radius are varied. As in the case for a two-layer quasigeostrophic model on a β-plane channel, it is found both that the Rhines scale successfully predicts the meridional scale of the multiple zonal jets, and that these jets are maintained in part by an eddy momentum flux divergence associated with slow baroclinic waves at the interjet minimum. A scalin g analysis suggests that njets α (a/χ m)1/2, with the constraints ζ e ≡ 8 sin2f (χ m/△χ) &gt; 1 and njets ≥ 1, where njets is the number of the jets, a the planetary radius, χm one-half of the pole-to-equator potential temperature difference, ζe the supercriticality of the two-layer Phillips model, △χ the potential temperature difference between the two levels, and Φ the latitude. The number of jets simulated by the model agrees with this scaling, provided that Ljet ≤ a, where Ljet is the jet scale. In model runs with a large planet where multiple zonal jets exist, the time-mean eddy heat flux is found to be consistent with the diffusive picture of Held and Larichev. In contrast, for the model runs with the planetary size equal to that of Earth, baroclinic adjustment is found to be more relevant. These results are consistent with the finding that in the large-planet (Earth-like) model runs, the jet/eddy scale is smaller than (comparable to) the corresponding planetary radius. © 2005 American Meteorological Society."
"6506964409;7006245928;7202364010;","Role of the atmosphere in climate variability of the tropical Atlantic",2003,"10.1175/1520-0442(2003)016<2052:ROTAIC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042346356&doi=10.1175%2f1520-0442%282003%29016%3c2052%3aROTAIC%3e2.0.CO%3b2&partnerID=40&md5=5bdc12eb71682cfa345c5334a9b18fc2","This paper explores climate variability of the lower troposphere and boundary layer in the tropical Atlantic sector through a series of modeling simulations with a diagnostic primitive equation model. The focus is on the role that realistic diabatic heating and its vertical placement as well as surface temperature have in inducing/ reinforcing the local monthly wind circulation, the role that thermal and momentum transients play in the Tropics, the potential for feedbacks, and the way through which other basins influence the tropical Atlantic region. NCEP-NCAR reanalysis data for the period 1958 93 are used to provide forcing and model verification. In the first part of the paper local effects are considered. It is found that the most important terms controlling anomalous surface winds over the ocean are boundary layer temperature gradients and diabatic heating anomalies at low levels (below 780 mb). Anomalous diabatic heating at mid- and upper levels (430-690 mb) contributes to the near-surface circulation poleward of 15 over the warm hemisphere. Anomalous diabatic heating over the African continent influences zonal winds well into the ocean. It is found that the anomalies of surface latent heat flux induced by the interhemispheric distribution of anomalies provide positive feedback on both sides of the equator, in the deep Tropics and west of 20 W. It provides negative feedback off the northwest coast of Africa. In the second part the relative importance of remote forcing is considered. It is found that anomalous heating associated with interhemispheric gradients of surface temperature in the tropical Atlantic influence winds in the northern extratropics in a wavelike pattern during boreal spring. Anomalous heating associated with equatorial anomalies of surface temperature influence winds in the southern extratropics in a wavelike pattern during boreal summer. In contrast, the influence of heating in the midlatitudes is confined to the northern subtropics. Anomalous ENSO-related diabatic heating influences near-surface winds in the tropical Atlantic, which resembles the local response to interhemispheric gradients of surface temperature. This remote influence induces changes in the intensity of the Atlantic Walker and Hadley circulations as a consequence of the direct effect of heating in the eastern tropical Pacific."
"57193921169;7004069241;","The deep-atmosphere Euler equations with a mass-based vertical coordinate",2003,"10.1256/qj.02.153","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037255542&doi=10.1256%2fqj.02.153&partnerID=40&md5=a98986f0394131f352490574de626e83","The terrain-following hydrostatic pressure-coordinate system for the shallow-atmosphere Euler equations is generalized for deep atmospheres using a mass-based vertical coordinate. A consequent benefit is that an existing (shallow atmosphere) hydrostatic primitive-equations model, which uses a pressure-based terrain-following vertical coordinate, could be modified for non-hydrostatic deep-atmosphere applications, without the need to change the scientific and computing infrastructure substantially in which it is embedded."
"7004069241;57193921169;57192158845;","Analysis of the numerics of physics-dynamics coupling",2002,"10.1256/qj.02.25","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036820868&doi=10.1256%2fqj.02.25&partnerID=40&md5=dfbc2a71ffcf885e6a0ab90f7c019daa","A methodology for analysing the numerical properties of schemes for coupling physics parametrizations to a dynamical core is presented. As an example of its application, the methodology is used to study four coupling schemes ('explicit', 'implicit', 'split-implicit' and 'symmetrized split-implicit') in the context of a semi-implicit semi-Lagrangian dynamical core. Each coupling scheme is assessed in terms of its numerical stability and of the accuracy of both its transient and steady-state responses. Additionally, the occurrence of spurious, computational resonance is analysed and discussed. It is found that in this respect all four schemes behave similarly. In particular, in the absence of any damping mechanism to control resonance, the time-step restriction needed to avoid spurious resonance is twice as restrictive for time-dependent forcing as for stationary forcing."
"56284582200;7101867299;","A simple theoretical model for the intensification of tropical cyclones and polar lows",1998,"10.1256/smsqj.54712","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031819004&doi=10.1256%2fsmsqj.54712&partnerID=40&md5=bfb7e47982742f94b205c1b7ed321249","A simple theoretical model for the intensification of tropical cyclones and polar lows is developed using a minimal set of physical assumptions. These disturbances are assumed to be balanced systems intensifying through the WISHE (Wind-Induced Surface Heat Exchange) intensification mechanism, driven by surface fluxes of heat and moisture into an atmosphere which is neutral to moist convection. The equation set is linearized about a resting basic state and solved as an initial-value problem. A system is predicted to intensify with an exponential perturbation growth rate scaled by the radial gradient of an efficiency parameter which crudely represents the effects of unsaturated processes. The form of this efficiency parameter is assumed to be defined by initial conditions, dependent on the nature of a pre-existing vortex required to precondition the atmosphere to a state in which the vortex can intensify. Evaluation of the simple model using a primitive-equation, nonlinear numerical model provides support for the prediction of exponential perturbation growth. Good agreement is found between the simple and numerical models for the sensitivities of the measured growth rate to various parameters, including surface roughness, the rate of transfer of heat and moisture from the ocean surface, and the scale for the growing vortex."
"7006104042;6602139264;7005295515;35239081300;","Physical interpretation of the attractor dimension for the primitive equations of atmospheric circulation",1997,"10.1175/1520-0469(1997)054<1137:PIOTAD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031474721&doi=10.1175%2f1520-0469%281997%29054%3c1137%3aPIOTAD%3e2.0.CO%3b2&partnerID=40&md5=1efb7401cef72b04556d9472ea2a7baa","In a series of recent papers, some of the authors have addressed with mathematical rigor some aspects of the primitive equations governing the large-scale atmospheric motion. Among other results, they derived without evaluating it an expression for the dimension of the attractor for those equations. It is known that the long-term behavior of the motion and states of the atmosphere can be described by the global attractor. Namely, starting with a given initial value, the solution will tend to the attractor as t goes to infinity. The dimension estimate of the global attractor is evaluated in this article, showing that this global attractor possesses a finite but large number of degrees of freedom. Using some arguments based on the known physical dissipation mechanisms, the bound on the dimension of the attractor in terms of the observable quantities governing the heating and energy dissipation accompanying the motion of the atmosphere is made immediately transparent. Consequently, to the extent that the resolution needed in numerical simulations of the long-term atmospheric motion is related to the dimension of the attractor, the result in this article suggests that the required resolution is quite sensitive to the magnitude of the effective (or eddy) viscosity, while it appears to be less sensitive to the details of the way that the atmosphere is heated."
"56130997600;7006417494;","Analytic approximations for moist convectively adjusted regions",1997,"10.1175/1520-0469(1997)054<1054:AAFMCA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031444080&doi=10.1175%2f1520-0469%281997%29054%3c1054%3aAAFMCA%3e2.0.CO%3b2&partnerID=40&md5=4530a3dbda9407562f6c44474fa37d1f","Solutions are obtained for convective regions in a continuously stratified, linearized primitive equation model using a smoothly posed moist convective adjustment parameterization of cumulus convection. In the approximation in which the convective adjustment time is fast compared to other processes, the vertical structure of the temperature field is constrained to be close to the quasi-equilibrium structure determined by the convective scheme. This in turn constrains the vertical structure of the baroclinic pressure gradients and velocity field. Analytic solutions result for vertical structures, while the horizontal and time dependence is governed by equations akin to shallow water equations. These consist of equations linking baroclinic velocities and pressure gradients, plus a moist static energy equation governing thermodynamics. This system holds for basic states that are slowly varying in space, for regions where deep convection happens frequently enough to constrain the temperature field. An effective static stability for these convectively constrained motions, the gross moist stability M, is defined in terms of thermodynamic variables. In time-dependent solutions, M determines phase speeds in deep convective regions. In solutions forced by sea surface temperature, M determines the work that must be done by vertical motion, which must in turn be balanced by surface fluxes. Surface fluxes tend to draw boundary layer temperature and moisture toward values determined by SST, while the convection translates these into deep baroclinic temperature and pressure gradients. The balance between surface fluxes and the effect of the gross moist stability on vertical motion determines how closely boundary layer enthalpy can follow SST. This picture combines modified versions of mechanisms proposed in simple models by Lindzen and Nigam, and Neelin and Held within a thermodynamically consistent framework. It also helps interpret models with convergence feedback schemes and the Gill model, and allows free parameters in these models to be related to basic thermodynamic quantities."
"7004010406;7102315560;","A theoretical model of Australian northwest cloudband disturbances and Southern Hemisphere storm tracks: The role of SST anomalies",1996,"10.1175/1520-0469(1996)053<1410:ATMOAN>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030455247&doi=10.1175%2f1520-0469%281996%29053%3c1410%3aATMOAN%3e2.0.CO%3b2&partnerID=40&md5=9d6fa1cf0cac5e6144569fc0526b5f95","The authors examine the effects of an enhanced sea surface temperature gradient, between the central Indian Ocean and the Indonesian archipelago, on the structure of the monthly averaged three-dimensional July global circulation and particularly on its consequent instability properties. This study has been conducted using a two-level primitive-equation model including a wave-CISK cumulus heating parameterization and using basic states taken from two AGCM simulations of the July circulation, with and without an enhanced SST gradient. The growing disturbances have been analyzed for various strengths of the cumulus heating. The study has focused on circulation changes associated with the development of Australian northwest cloudband disturbances and changes in Southern Hemisphere storm tracks. With an enhanced SST gradient, the authors have found a new group of modes that can be associated with circulation changes surrounding the onset of the simulated northwest cloudband events. Such modes are shown to compare favorably with simulated perturbations in the circulation and the results of an EOF analysis. With an enhanced gradient, there is also a discernible equatorward shift of the storm track instability modes over the Australian region, and the modes have much larger amplitude on the subtropical jet. The upper-level divergence is also more concentrated in the Australian region."
"7402401574;","Lagrangian flow in the middle atmosphere",1994,"10.1002/qj.49712051909","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028667315&doi=10.1002%2fqj.49712051909&partnerID=40&md5=3dfc611b5ac42cad4006bce3458d3ea5","The Lagrangian view of air flow in the middle atmosphere is studied by computing tens of thousands of particle trajectories in a global primitive‐equation model. This approach focuses attention on the long‐term fate of air and provides a high‐resolution view of air transport. Simulations are carried out for both the northern and southern winters to permit an inter‐hemispheric comparison. The first part of the paper concentrates on transport in the meridional plane. Trajectories followed for many months show patterns which are well organized on a global scale. Ensembles of particles followed for a much shorter time are used to calculate a Lagrangian mean meridional circulation which shows close similarities to published diabatic circulations calculated from observational data. Maps of meridional dispersion reveal a broad mid‐latitude band, with well defined boundaries, in which rapid dispersion occurs. A more detailed visualization of transport in and around the southern polar vortex in late winter shows that small scales are generated in this mid‐latitude region, but not in the vortex nor at low latitudes. The ability of the vortex to retain a labelled air mass for many months is clearly demonstrated, and the relevance of the results to understanding springtime ozone depletion is discussed. Copyright © 1994 Royal Meteorological Society"
"7003991093;","Mechanisms and parameterizations of geostrophic adjustment and a variational approach to balanced flow",1992,"10.1175/1520-0469(1992)049<1144:MAPOGA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027008835&doi=10.1175%2f1520-0469%281992%29049%3c1144%3aMAPOGA%3e2.0.CO%3b2&partnerID=40&md5=d62382a52c19d052aca09020704832b4","Geostrophic balance is shown to be the minimum energy state, for a given linear potential vorticity field, for small deviations of the height field around a resting state, in the shallow-water equations. This includes (but is not limited to) the linearized shallow-water equations. Quasigeostrophic motion is evolution on the slow manifold defined by advection of linear potential vorticity by the velocity field that minimizes that energy. Other linear and nonlinear arguments suggest that geostrophic adjustment is a process whereby the energy of a flow is minimized consistent with the maintenance of the potential vorticity field. It is also shown how the process of geostrophic adjustment may be significantly accelerated, or parameterized, in the primitive equations by the addition of certain terms to the equations of motion. Application of the parameterization to an unbalanced state in a primitive equation model is very effective in achieving a balanced state and in continuously filtering gravity waves. -from Author"
"7406500730;","A study of nonhydrostatic effects in idealized sea breeze systems",1991,"10.1007/BF00119419","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025955909&doi=10.1007%2fBF00119419&partnerID=40&md5=088daf7e3d6d2f627500f3ca0c2ef7ea","Nonhydrostatic effects in two-dimensional mesoscale sea breeze systems are investigated by numerical simulations. It is shown that nonhydrostatic effects are directly contributed by the vertical gradients of the vertical velocity variance as well as by the vertical accelerations. It is also shown that a K-type turbulence closure is not suitable in a nonhydrostatic primitive equation model, and a higher-order closure scheme should therefore be used. Results from hydrostatic and fully-nonhydrostatic models are compared for various surface and atmospheric background conditions, such as scale and strength of surface heating, geostrophic wind, stability, surface roughness contrast, Coriolis effect, etc. It is found that for strongly developed sea breeze cases, vertical gradients of vertical velocity variance contribute most to nonhydrostatic forcing in the lower layers, and that the resultant nonhydrostatic pressure gradient acts against the hydrostatic pressure gradient, so that nonhydrostatic simulations produce weaker systems than hydrostatic ones. For weak sea breeze systems, the difference between the two models tends to be small. © 1991 Kluwer Academic Publishers."
"57216189838;7404416268;","Synoptic-scale influences of snow cover and sea ice.",1986,"10.1175/1520-0493(1986)114<1795:SSIOSC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022841549&doi=10.1175%2f1520-0493%281986%29114%3c1795%3aSSIOSC%3e2.0.CO%3b2&partnerID=40&md5=b005a14a1de192047c76f5b78fa749fc","Daily observational data to 30 winters (1951-80) are used to test the hypothesis that anomalous distributions of snow and ice cover influence the intensification and/or trajectories or synoptic- scale cyclones. The pools of objectively chosen cases include 100 wintertime cyclonic events in the marginal snow/ice zones of each of three regions: eastern North America, the North Atlantic Ocean and the North Pacific Ocean. The results also suggest that forecasts of weekly or monthly circulation patterns may, in situations of extreme snow/ice cover, be improved by consideration of observed snow/ice anomalies, if these anomalies persist through the forecast period. Controlled experiments with the NCAR (National Center for Atmospheric Research) primitive equations forecast model show a weaker dependence on the extent of snow and ice, although qualitative similarities to the data-based results are detectable.-from Authors"
"13406399300;7202192265;36644095800;7103342287;57002623400;7202979963;6701431208;7102645933;36179077700;7406243250;31067496800;8696068200;25031430500;7102696626;57203093888;36992744000;36876405100;8866821900;35767566800;6701357023;","NCAR Release of CAM-SE in CESM2.0: A Reformulation of the Spectral Element Dynamical Core in Dry-Mass Vertical Coordinates With Comprehensive Treatment of Condensates and Energy",2018,"10.1029/2017MS001257","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050495279&doi=10.1029%2f2017MS001257&partnerID=40&md5=a9f4e7ff9be21e4e4dbe77388d434612","It is the purpose of this paper to provide a comprehensive documentation of the new NCAR (National Center for Atmospheric Research) version of the spectral element (SE) dynamical core as part of the Community Earth System Model (CESM2.0) release. This version differs from previous releases of the SE dynamical core in several ways. Most notably the hybrid sigma vertical coordinate is based on dry air mass, the condensates are dynamically active in the thermodynamic and momentum equations (also referred to as condensate loading), and the continuous equations of motion conserve a more comprehensive total energy that includes condensates. Not related to the vertical coordinate change, the hyperviscosity operators and the vertical remapping algorithms have been modified. The code base has been significantly reduced, sped up, and cleaned up as part of integrating SE as a dynamical core in the CAM (Community Atmosphere Model) repository rather than importing the SE dynamical core from High-Order Methods Modeling environment as an external code. ©2018. The Authors."
"12645982700;","Canonical transfer and multiscale energetics for primitive and quasigeostrophic atmospheres",2016,"10.1175/JAS-D-16-0131.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994166949&doi=10.1175%2fJAS-D-16-0131.1&partnerID=40&md5=789c569033618fd1b47f7962abc97b70","The past years have seen the success of a novel and rigorous localized multiscale energetics formalism in a variety of ocean and engineering fluid applications. In a self-contained way, this study introduces it to the atmospheric dynamical diagnostics, with important theoretical updates and clarifications of some common misconceptions about multiscale energy. Multiscale equations are derived using a new analysis apparatus-namely, multiscale window transform-with respect to both the primitive equation and quasigeostrophic models. A reconstruction of the ""atomic"" energy fluxes on the multiple scale windows allows for a natural and unique separation of the in-scale transports and cross-scale transfers from the intertwined nonlinear processes. The resulting energy transfers bear a Lie bracket form, reminiscent of the Poisson bracket in Hamiltonian mechanics; hence, we would call them ""canonical."" A canonical transfer process is a mere redistribution of energy among scale windows, without generating or destroying energy as a whole. By classification, a multiscale energetic cycle comprises available potential energy (APE) transport, kinetic energy (KE) transport, pressure work, buoyancy conversion, work done by external forcing and friction, and the cross-scale canonical transfers of APE and KE, which correspond respectively to the baroclinic and barotropic instabilities in geophysical fluid dynamics. A buoyancy conversion takes place in an individual window only, bridging the two types of energy, namely, KE and APE; it does not involve any processes among different scale windows and is hence basically not related to instabilities. This formalism is exemplified with a preliminary application to the study of the Madden-Julian oscillation. © 2016 American Meteorological Society."
"7004978125;56434851400;","A multiscale model for the intraseasonal impact of the diurnal cycle over the maritime continent on the Madden-Julian oscillation",2016,"10.1175/JAS-D-15-0158.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84958635409&doi=10.1175%2fJAS-D-15-0158.1&partnerID=40&md5=dbc5d6dd6c90f41b98f7cc070c3bdf8e","The eastward-propagating Madden-Julian oscillation (MJO) typically exhibits complex behavior during its passage over the Maritime Continent, sometimes slowly propagating eastward and other times stalling and even terminating there with large amounts of rainfall. This is a huge challenge for present-day numerical models to simulate. One possible reason is the inadequate treatment of the diurnal cycle and its scale interaction with the MJO. Here these two components are incorporated into a simple self-consistent multiscale model that includes one model for the intraseasonal impact of the diurnal cycle and another one for the planetary/intraseasonal circulation. The latter model is forced self-consistently by eddy flux divergences of momentum and temperature from a model for the diurnal cycle with two baroclinic modes, which capture the intraseasonal impact of the diurnal cycle. The MJO is modeled as the planetary-scale circulation response to a moving heat source on the synoptic and planetary scales. The results show that the intraseasonal impact of the diurnal cycle during boreal winter tends to strengthen the westerlies (easterlies) in the lower (upper) troposphere in agreement with the observations. In addition, the temperature anomaly induced by the intraseasonal impact of the diurnal cycle can cancel that from the symmetric-asymmetric MJO with convective momentum transfer, yielding stalled or suppressed propagation of the MJO across the Maritime Continent. The simple multiscale model should be useful for the MJO in observations or more complex numerical models. © 2016 American Meteorological Society."
"36138641800;35345503300;36866503400;","Interactions between stationary waves and ice sheets: Linear versus nonlinear atmospheric response",2012,"10.1007/s00382-011-1004-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857441142&doi=10.1007%2fs00382-011-1004-6&partnerID=40&md5=d16bff351fea9b4f79cde0acc2caff26","This study examines the mutual interaction between topographically-forced atmospheric stationary waves and continental-scale ice sheets using a thermomechanical ice-sheet model coupled to a linear as well as a fully-nonlinear dry atmospheric primitive equation model. The focus is on how the stationary-wave induced ablation feeds back on the ice sheet. Simulations are conducted in which an embryonal ice mass, on an idealised ""North American"" continent, evolves to an equilibrium ice sheet. Under the coupling to the linear atmospheric model, the equilibrium ice sheet is primarily controlled by the ratio between the wavelength of the stationary waves and the zonal continental extent. When this ratio is near two, the ice sheet has its center of mass shifted far eastward and its shape is broadly reminiscent of the Laurentide ice sheet at LGM. For wavelengths comparable to the continental extent, however, the ice margin extends far equatorward on the central continent but is displaced poleward near the eastern coast. Remarkably, the coupling to the nonlinear atmospheric model yields equilibrium ice sheets that are virtually identical to the ones obtained in uncoupled simulations, i. e. a symmetric ice sheet with a zonal southern margin. Thus, the degree of linearity of the atmospheric response should control to what extent topographically-forced stationary waves can reorganise the structure of ice sheets. If the stationary-wave response is linear, the present results suggest that spatial reconstructions of past ice sheets can provide some information on the zonal-mean atmospheric circulation that prevailed. © 2011 Springer-Verlag."
"6603139566;7005256983;","Modulation of the Great Plains low-level jet and moisture transports by orography and large-scale circulations",2003,"10.1029/2002jd003005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342289983&doi=10.1029%2f2002jd003005&partnerID=40&md5=5c33dfcf899772026b8c17b75968acd2","This paper describes orographic processes that modulate the Great Plains low-level jet (LLJ) and related hydrology of the Mississippi River basin. Mechanical flow deflection by the Rocky Mountains is diagnosed in 50 years of monthly averaged National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) Reanalysis fields and in a series of integrations using a primitive equation version of the Utah Global Model (UGM). Although the mountain profiles are fixed over periods of short-to medium-range climate changes, their influence on the LLJ is not stationary because evolving ambient flows produce changing LLJ responses. Ensembles of medium-range forecasts are made for the 1993 U.S. floods and for the 1988 U.S. drought. The forecasts distinguish some of the observed precipitation differences between these years, but the magnitude of the differences is underestimated. Seasonal and longer-term changes of the ambient flow occur on large scales, while the response of the LLJ occurs on smaller scales that may promote cloud generation and precipitation. Month-long simulations with monthly averaged conditions suggest that the Great Plains LLJ is a component of the large-scale circulation associated with the topography of the western United States. Orography thus provides a scale transfer mechanism that focuses global-scale features into the regional-scale responses. These are relevant to precipitation distribution and to moisture budgets of the larger individual river basins comprising the GCIP domain. A theoretical interpretation of the large-scale, mechanical influence of orography on surrounding low-level circulations is proposed. Copyright 2003 by the American Geophysical Union."
"7003894514;57203997211;7004060399;","An efficient spectral dynamical core for distributed memory computers",2002,"10.1175/1520-0493(2002)130<1384:AESDCF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036566631&doi=10.1175%2f1520-0493%282002%29130%3c1384%3aAESDCF%3e2.0.CO%3b2&partnerID=40&md5=6bd20e6bb8832ef669f29c0ae0d1b13f","The practical question of whether the classical spectral transform method, widely used in atmospheric modeling, can be efficiently implemented on inexpensive commodity clusters is addressed. Typically, such clusters have limited cache and memory sizes. To demonstrate that these limitations can be overcome, the authors have built a spherical general circulation model dynamical core, called BOB (""Built on Beowulf""), which can solve either the shallow water equations or the atmospheric primitive equations in pressure coordinates. That BOB is targeted for computing at high resolution on modestly sized and priced commodity clusters is reflected in four areas of its design. First, the associated Legendre polynomials (ALPs) are computed ""on the fly"" using a stable and accurate recursion relation. Second, an identity is employed that eliminates the storage of the derivatives of the ALPs. Both of these algorithmic choices reduce the memory footprint and memory bandwidth requirements of the spectral transform. Third, a cache-blocked and unrolled Legendre transform achieves a high performance level that resists deterioration as resolution is increased. Finally, the parallel implementation of BOB is transposition-based, employing load-balanced, one-dimensional decompositions in both latitude and wavenumber. A number of standard tests is used to compare BOB's performance to two well-known codes-the Parallel Spectral Transform Shallow Water Model (PSTSWM) and the dynamical core of NCAR's Community Climate Model CCM3. Compared to PSTSWM, BOB shows better timing results, particularly at the higher resolutions where cache effects become important. BOB also shows better performance in its comparison with CCM3's dynamical core. With 16 processors, at a triangular spectral truncation of T85, it is roughly five times faster when computing the solution to the standard Held-Suarez test case, which involves 18 levels in the vertical. BOB also shows a significantly smaller memory footprint in these comparison tests."
"7003639093;7102969748;","Numerical simulations of seasonal and interannual variability of the Black Sea thermohaline circulation",1999,"10.1016/S0924-7963(99)00043-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032694666&doi=10.1016%2fS0924-7963%2899%2900043-3&partnerID=40&md5=75e7ff67c6c297cfa1fb4dfcb0e80fce","The Black Sea general circulation is simulated by a primitive equation model with active free surface. The forcing is seasonally variable and is based on available climatic data. The model reproduces the main features of the Black Sea circulation, including the fiver discharge effects on the mean sea level and the Bosphorus outflow. Model results show that the simulated sea surface elevation increases in spring over the whole sea, reaching a maximum in the Danube delta area. In the same region, a minimum is observed in winter. The amplitude of the seasonal oscillations (about 8-12 cm over the whole basin) is of the same order of magnitude as the maximum horizontal variations (about 15-18 cm between the coastal areas and the basin interior). This strong signal formed mostly by river discharges, along with the seasonal variability in the other forcing functions and the local dynamics creates a well-pronounced interannual variability. The performance of the model in simulating the seasonal and interannual variability is critically analyzed, with a special attention on the cold intermediate water formation and the circulation in the upper 150 m. The simulations demonstrate that the source of intermediate waters is on the shelf, and that the water mass in the core of cold intermediate layer changes with time as a response to the periodic forcing at sea surface. This type of variability is characterized by pronounced interannual changes, proving that important differences could exist between water mass structure in different years, even when using identical atmospheric forcings each year."
"7005143365;7003633691;7103126833;57218972637;","Bhopal gas leak: A numerical simulation of episodic dispersion",1995,"10.1016/1352-2310(95)00031-S","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028991280&doi=10.1016%2f1352-2310%2895%2900031-S&partnerID=40&md5=ca21a714c218e6be66517860729b4369","A mesoscale meteorological model coupled with a Lagrangian particle dispersion (LPD) model was used to simulate the Bhopal methyl isocyanate (MIC) gas leak. A simple two layer K-closure version of the Pielke primitive equation meteorological model was used to produce the wind and turbulence fields in the planetary boundary layer (PBL). Initialized by a single 3 m s-1 geostrophic wind, the PBL model produced a low wind speed stable surface layer capped by a 250 m high nocturnal inversion. The results compared well with limited meteorological observations. However, the LPD model failed to produce enough vertical and horizontal mixing to match the extent of the affected area which was derived from the mortality statistics. Recommendations to improve the model physics to accomodate enhanced mixing in urban areas and to treat MIC thermodynamics and chemistry are suggested. © 1995."
"7402879136;","On the structure of a convergent cloud band over the Japan sea in winter; A prediction experiment",1987,"10.2151/jmsj1965.65.6_871","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0039095770&doi=10.2151%2fjmsj1965.65.6_871&partnerID=40&md5=644e777e64313174165dfb58e3d24b5e","A prediction experiment is performed with a very-fine-mesh (42km at 60°N) primitive equation model for a heavy snowfall event in the Hokuriku District associated with a convergent cloud band over the Japan Sea. Using the result of the experiment, together with observed data including special soundings, we elucidate the structure of the convergent cloud band with a line of active convection on its southwestern edge. The atmosphere around the cloud band has the following characteristic features: - a low-level convergence, middle-level divergence zone accompanied by intense positive vorticity along the line of active convection, - a warm and weak-wind zone along the line of active convection embedded in cold airmass - a weak stable layer on the northeastern side of the line of active convection as a boundary between two layers: a lower layer with northerly cold air flow toward the line of active convection and an upper layer with southwesterly warm air flow which has been heated in the line of active convection, - a west-northwesterly air flow on the southwestern side of the line of active convection with weak vertical wind shear and nearly neutral stratification up to the top of the cold airmass, - a strong-wind zone at the divergent level (700-6OOmb) 300-500km northeast of the line of active convection. On the basis of cross-section and trajectory analyses, we can make a clear picture of the atmosphere around the cloud band. Heat and water vapor budget analysis indicates that over the southern Japan Sea the mesoscale thermal structure around the cloud band is largely maintained by localized release of latent heat in large-scale cold air advection field. © 1987, Meteorological Society of Japan."
"7201439545;7004504559;7004211281;7004157687;","Modelling the Quasi‐Equilibrium Dynamics of the Atmosphere",1987,"10.1002/qj.49711347704","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023510665&doi=10.1002%2fqj.49711347704&partnerID=40&md5=9fc6d5ce6152d350bfde5528a0ae80ea","The prime need in forecasting atmospheric motions is to predict the synoptic pattern accurately, and to fill in as much mesoscale detail on it as possible. the problem is difficult because the atmospheric fields contain almost discontinuous structures such as fronts and inversions, and the large‐scale flow may separate around mountains. This paper demonstrates that such phenomena may be described as quasi‐equilibrium structures where the fluid remains close to a minimum energy state. This minimum is shown to correspond to geostrophic and hydrostatic balance, and the implied quasi‐equilibrium evolution to correspond to the Lagrangian form of the geostrophic momentum equations. Examples of flows that can be treated include boundary layers separating at surface fronts and mountain blocking with associated drag. By including diabatic effects, the inland penetration of sea breezes can also be studied. the quasi‐equilibrium idea can be applied globally, but describes only a limited subset of tropical motions. Primitive equation models attempt to produce these structures by relying on explicit geostrophic adjustment. This paper presents evidence that this is not always adequate, especially when the structures contain discontinuities. Implicit algorithms are described which may be more effective. Copyright © 1987 Royal Meteorological Society"
"7003735935;7005467554;","Four-dimensional data assimilation in the monsoon region. Part I: experiments with wind data.",1987,"10.1175/1520-0493(1987)115<1678:fddait>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023111795&doi=10.1175%2f1520-0493%281987%29115%3c1678%3afddait%3e2.0.co%3b2&partnerID=40&md5=2a8ec73ccfe0aab18c168b09b365d2ef","A limited area primitive equation model is used to study the feasibility of four dimensional data assimilation in the monsoon region and studies the applicability of several assimilation techniques currently employed in global models. Tries to determine how the model atmosphere responds to the insertion of asynchronous data and its impact on the assimilation prediction cycle and also what assimilation strategies work best for limited area models in the tropics."
"56123889200;25226537800;55348249000;56524152600;57191290414;7003748648;9534827700;","Pan-European climate at convection-permitting scale: a model intercomparison study",2020,"10.1007/s00382-018-4114-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044088741&doi=10.1007%2fs00382-018-4114-6&partnerID=40&md5=8b3d7dc58ed627bd27cd5070210d877f","We investigate the effect of using convection-permitting models (CPMs) spanning a pan-European domain on the representation of precipitation distribution at a climatic scale. In particular we compare two 2.2 km models with two 12 km models run by ETH Zürich (ETH-12 km and ETH-2.2 km) and the Met-Office (UKMO-12 km and UKMO-2.2 km). The two CPMs yield qualitatively similar differences to the precipitation climatology compared to the 12 km models, despite using different dynamical cores and different parameterization packages. A quantitative analysis confirms that the CPMs give the largest differences compared to 12 km models in the hourly precipitation distribution in regions and seasons where convection is a key process: in summer across the whole of Europe and in autumn over the Mediterranean Sea and coasts. Mean precipitation is increased over high orography, with an increased amplitude of the diurnal cycle. We highlight that both CPMs show an increased number of moderate to intense short-lasting events and a decreased number of longer-lasting low-intensity events everywhere, correcting (and often over-correcting) biases in the 12 km models. The overall hourly distribution and the intensity of the most intense events is improved in Switzerland and to a lesser extent in the UK but deteriorates in Germany. The timing of the peak in the diurnal cycle of precipitation is improved. At the daily time-scale, differences in the precipitation distribution are less clear but the greater Alpine region stands out with the largest differences. Also, Mediterranean autumnal intense events are better represented at the daily time-scale in both 2.2 km models, due to improved representation of mesoscale processes. © 2018, © Crown 2018."
"7405763496;57189251941;57202984538;25642405500;56006103500;7101727951;57192944066;57199433321;26029479600;57202988441;","The Korean Integrated Model (KIM) System for Global Weather Forecasting",2018,"10.1007/s13143-018-0028-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049959860&doi=10.1007%2fs13143-018-0028-9&partnerID=40&md5=8f15340a979a6a1a7eae8effd676e5bd","The Korea Institute of Atmospheric Prediction Systems (KIAPS) began a national project to develop a new global atmospheric model system in 2011. The ultimate goal of this 9-year project is to replace the current operational model at the Korea Meteorological Administration (KMA), which was adopted from the United Kingdom’s Meteorological Office’s unified model (UM) in 2010. The 12-km Korean Integrated Model (KIM) system, consisting of a spectral-element non-hydrostatic dynamical core on a cubed sphere grid and a state-of-the-art physics parameterization package, has been launched in a real-time forecast framework, with initial conditions obtained via the advanced hybrid four-dimensional ensemble variational data assimilation (4DEnVar) over its native grid. A development strategy for KIM and the evolution of its performance in medium-range forecasts toward a world-class global forecast system are described. Outstanding issues in KIM 3.1 as of February 2018 are discussed, along with a future plan for operational deployment in 2020. © 2018, Korean Meteorological Society and Springer Nature B.V."
"55933133600;7004861251;","Evaluation of extreme rainfall and temperature over North America in CanRCM4 and CRCM5",2016,"10.1007/s00382-015-2807-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949560963&doi=10.1007%2fs00382-015-2807-7&partnerID=40&md5=c54fc7116b7af36e6d5dc310b2f2bcc0","We assess the ability of two Canadian regional climate models (RCMs), CanRCM4 and CRCM5, to simulate North American climate extremes over the period 1989–2009. Both RCMs use lateral boundary conditions derived from the ERA-Interim reanalysis and share the same dynamical core but use different nesting strategies, land-surface and physics schemes. The annual cycle and spatial patterns of extreme temperature indices are generally well reproduced in both models but the magnitude varies. In central and southern North America, maximum temperature extremes are up to 7 °C warmer in CanRCM4. There is a cool bias in minimum temperature extremes in both RCMs. The shape of the annual cycle of extreme rainfall varies between simulations. There is a wet bias in CRCM5 extreme rainfall on the west coast throughout the year and in winter rainfall elsewhere. In summer both RCMs have precipitation biases in the south-east. These rainfall and temperature biases are likely associated with differences in the physical parameterisation of rainfall. CanRCM4 simulates too little convective rainfall, while over-estimating large-scale rainfall; nevertheless, cloud cover is well simulated. CRCM5 simulates more large-scale rainfall throughout the year on the west coast and in winter in other regions. The spatial extent, intensity and location of atmospheric river (AR) landfall are well reproduced by the RCMs, as is the fraction of winter rainfall from AR days. Spectral nudging improves agreement on landfall latitude between the RCM and the driving model without greatly diminishing the intensity of the rainfall extreme. © 2015, The Author(s)."
"8866821900;7402435469;57212416832;","Reference aquaplanet climate in the Community Atmosphere Model, Version 5",2016,"10.1002/2015MS000593","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978322325&doi=10.1002%2f2015MS000593&partnerID=40&md5=3846a283d00d7db20690bc98a7daefcc","Fundamental characteristics of the aquaplanet climate simulated by the Community Atmosphere Model, Version 5.3 (CAM5.3) are presented. The assumptions and simplifications of the configuration are described. A 16 year long, perpetual equinox integration with prescribed SST using the model's standard 1°grid spacing is presented as a reference simulation. Statistical analysis is presented that shows similar aquaplanet configurations can be run for about 2 years to obtain robust climatological structures, including global and zonal means, eddy statistics, and precipitation distributions. Such a simulation can be compared to the reference simulation to discern differences in the climate, including an assessment of confidence in the differences. To aid such comparisons, the reference simulation has been made available via earthsystemgrid.org. Examples are shown comparing the reference simulation with simulations from the CAM5 series that make different microphysical assumptions and use a different dynamical core. © 2016. The Authors."
"56487312300;6603581315;8374319200;24472698700;57191654133;","SPEEDY-IER: A fast atmospheric GCM with water isotope physics",2015,"10.1002/2014JD022194","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922008164&doi=10.1002%2f2014JD022194&partnerID=40&md5=140cf10d3fe4eab658ed8f651007185b","The interpretation of variations in the global isotopic composition of precipitation and water vapor can be strengthened using an isotope-enabled atmospheric general circulation model (AGCM). Here we present a fast-physics atmospheric circulation model suitable for long ensemble integrations: the efficient AGCM Simplified Parameterizations, Primitive Equation Dynamics (SPEEDY), with newly added water isotope physics. The model (SPEEDY-isotope-enabled reconstructions (IER)) simulates the hydrological cycle and isotope ratios in atmospheric water at a fraction of the computational cost of Intergovernmental Panel on Climate Change (IPCC)-class GCMs. Despite its simplified physics, SPEEDY-IER captures many key features of the observed range of tropical, subtropical, and midlatitude isotope variability when compared to the Global Network of Isotopes in Precipitation, Stable Water Isotope Intercomparison Group (SWING2) simulations, and satellite observations of isotopes in vapor. The incorporation of water isotopes in SPEEDY required two updates to the model’s physics: postcondensational exchange associated with falling rain and soil hydrology. It is evident that these physical processes are essential for a skillful simulation of isotopes in precipitation and vapor. We conduct a suite of sensitivity tests to constrain effective parameters in the rain exchange and land models and assess the impact of the new physics to isotope simulations. The strong sensitivity to parameter choice in these components reaffirms the importance of land-atmosphere interactions and rain-vapor exchange on stable water isotope ratios in the atmosphere and thus on the interpretation of paleoclimate records. The utility of SPEEDY-IER for climate applications is discussed. © 2014. American Geophysical Union. All Rights Reserved."
"31067496800;","Understanding the treatment of waves in atmospheric models. Part 1: The shortest resolved waves of the 1D linearized shallow-water equations",2014,"10.1002/qj.2226","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905004987&doi=10.1002%2fqj.2226&partnerID=40&md5=a8109879c16d5672b92064a2c4d1f52b","This article provides an intercomparison of the dispersive and diffusive properties of several standard numerical methods applied to the 1D linearized shallow-water equations without the Coriolis term, including upwind and central finite-volume, spectral finite-volume, discontinuous Galerkin, spectral element, and staggered finite-volume. All methods are studied up to tenth-order accuracy, where possible. A consistent framework is developed which allows for direct intercomparison of the ability of these methods to capture the behaviour of linear gravity waves. The Courant-Friedrichs-Lewy (CFL) condition is also computed, which is important for gauging the stability of these methods, and leads to a measure of approximate equal error cost. The goal of this work is threefold: first, to determine the shortest wavelength which can be considered 'resolved' for a particular method; second, to determine the effect of increasing the order of accuracy on the ability of a method to capture wave-like motion; and third, to determine which numerical methods offer the best treatment of wave-like motion. © 2013 Royal Meteorological Society."
"55394412800;7004069241;7004093651;","Dispersion analysis of the spectral element method",2012,"10.1002/qj.1906","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84868156490&doi=10.1002%2fqj.1906&partnerID=40&md5=d4f3c8ad944e934d1e562dfde649a10f","The spectral element method (SEM) has (with exact time integration) the desirable attribute of locally and globally conserving mass, energy and potential vorticity. It also scales well on massively parallel computers. Another desirable attribute of a numerical method for an atmospheric dynamical core is that it should have good numerical dispersion properties in order to accurately represent wave propagation and adjustment processes. Application of the SEM to the one-way wave equation is analysed to provide insight into its dispersion properties as a function of spectral order. For the lowest-order spectral truncation (linear) the SEM discretisation is formally equivalent to centred second-order finite differences on an Arakawa A grid. It consequently shares its poor dispersion properties, including energy propagation in the wrong direction for the short-wavelength half of the spectrum. Increasing the spectral truncation of the SEM to quadratic improves its dispersion properties for the long-wavelength part of the spectrum, but the problem of energy propagation in the wrong direction for the short-wavelength part remains. Further increasing the order of the spectral truncation not only fails to address the poor energy propagation at small scales, but also introduces new problems, including gaps in the spectrum of frequencies that can be represented, and localisation of eigenmode structures near element boundaries. Numerical integrations confirm that these SEM dispersion properties lead to reversed group velocities and to grid imprinting at spectral element boundaries. © 2012 Royal Meteorological Society and British Crown, the Met Office."
"22962457400;7401977103;","A general circulation model ensemble study of the atmospheric circulation of Venus",2010,"10.1029/2009JE003490","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951035332&doi=10.1029%2f2009JE003490&partnerID=40&md5=25eb1d2fa344f5c7dc65f28d2f1c32aa","The response of three numerical model dynamical cores to Venus-like forcing and friction is described in this paper. Each dynamical core simulates a super-rotating atmospheric circulation with equatorial winds of 35 ± 10 m/s, maintained by horizontally propagating eddies leaving the equatorial region and inducing a momentum convergence there. We discuss the balance between the mean circulation and eddies with reference to the production of a super-rotating equatorial flow. The balance between the horizontal eddies and vertical eddies in the polar region is discussed and shown to produce an indirect overturning circulation above the jet. The indirect overturning may be related to the observed region of the polar dipole in the Venus atmosphere. Reservoirs of energy and momentum are calculated for each dynamical core and explicit sources and sinks are diagnosed from the general circulation model (GCM). The effect of a strong ""sponge layer"" damping to rest is compared with eddy damping and found to change significantly the momentum balance within the top ""sponge layer"" but does not significantly affect the super-rotation of the bulk of the atmosphere. The Lorenz (1955) energy cycle is calculated and the circulation is shown to be dominated by energy conversion between the mean potential energy and mean kinetic energy reservoirs, with barotropic energy conversion between the mean kinetic energy and eddy kinetic energy reservoirs. We suggest modifications to the GCM parameterizations on the basis of our analysis of the atmospheric circulation and discuss the effect of numerical parameterizations on the simulated atmosphere. Copyright 2010 by the American Geophysical Union."
"7102315560;","Genesis of intraseasonal oscillations and equatorial waves",2002,"10.1175/1520-0469(2002)059<2761:GOIOAE>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036797145&doi=10.1175%2f1520-0469%282002%29059%3c2761%3aGOIOAE%3e2.0.CO%3b2&partnerID=40&md5=f8b1b94e3597b2a4595d9bca68d7bcac","The particular role of evaporation-wind feedback, and as well cumulus convection and dissipation, in the formation of the Madden-Julian 30-60-day intraseasonal oscillation (MJO) and equatorially trapped waves, including Kelvin, equatorial Rossby, mixed Rossby-gravity, and eastward inertio-gravity waves, has been studied using a global two-level primitive equation instability model. The evaporation has been specified through a bulk aerodynamic formula, and the convection through a generalized Kuo-type parameterization with a moist static stability that is positive everywhere so that wave-conditional instability of the second kind (CISK) is not possible. Both three-dimensional and zonally averaged basic states for January 1979 have been employed, and the e-folding times, periods, structures, and propagation characteristics of these waves have been analyzed and compared with their observed properties. The MJO modes appear to be particularly realistic when the three-dimensional basic state includes evaporation- wind feedback, which promotes the zonal wavenumber-1 component of the eastward-propagating velocity potential, and cumulus convection. The tropical velocity potential propagates eastward relatively quickly around the globe (≈13.6 m s-1, corresponding to a period of 34.4 days), while in the convective region between the Indian Ocean and the date line the divergence propagates more slowly (≈4.5 m s-1). The MJO has a largely first internal mode structure in the Tropics with a more equivalent barotropic structure of the streamfunction in the extratropics, including distinct Pacific-North American and Eurasian patterns. The MJO modes do not lie along any of the theoretical dispersion curves of equatorially trapped waves and have distinctly longer periods than the model convectively coupled Kelvin waves, even at zonal wavenumber 1, as in the observational study of M. Wheeler and G.N. Kiladis. The Kelvin mode streamfunction fields also do not exhibit the largely equivalent barotropic teleconnection patterns in the extratropics typical of the MJO. With cumulus convection and evaporation- wind feedback, the model equatorially trapped Kelvin, equatorial Rossby, mixed Rossby-gravity, and eastward inertio-gravity waves have periods, structures, and propagation characteristics comparable to those of corresponding convectively coupled observed waves."
"7005337548;","Does the wind control the import and export of the South Atlantic?",2000,"10.1175/1520-0485(2000)030<2650:DTWCTI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034487581&doi=10.1175%2f1520-0485%282000%29030%3c2650%3aDTWCTI%3e2.0.CO%3b2&partnerID=40&md5=f5bf3cf5a5ea493e05847ed5dea31b74","A different way of examining the meridional flux of warm and intermediate water (σe &lt; 27.50) from the Southern Ocean into the South Atlantic is proposed. The method considers the Americas to be a ""pseudo island"" in the sense that the continent is entirely surrounded by water but has no circulation around it. It is shown that, although the northern connection between the Atlantic and the Pacific (via the Bering Strait) is weak, it imposes severe limitations on the sea level in the Atlantic basin: so much so that it allows one to compute the meridional transport without finding the detailed solution to the complete wind-thermohaline problem. The method employs an integration of the linearized momentum equations along a closed contour containing the Americas, Greenland, the Atlantic, and parts of the Arctic Ocean. First, an idealized rectangular model involving three layers, an active continuously stratified upper layer containing both thermocline (σ6 &lt; 26.80) and intermediate water (26.80 &lt; σ6 &lt; 27.80), an inert deep layer (27.80 &lt; σ6 &lt; 27.90), and a southward moving bottom layer (σ6 &gt; 27.90) is considered. In this idealized model, the Americas are represented by the pseudo island. Deep-water formation is allowed (in the northern part of the basin east of the Americas and south of the gap connecting the Atlantic-Arctic basin to the Pacific), but the cooling rate need not be specified. The basin is subject to both zonal winds and heat exchange with the atmosphere [i.e., ρ = p(x, y, z)], but, for simplicity, (temporarily) meridional winds are not allowed. A simple analytical expression for the transport of the meridional overturning cell is derived, and process-oriented numerical experiments that were conducted (using a primitive equation layer-and-a-half isopyenic model) are in excellent agreement with the theory. The theory is then extended to a more convoluted geography subject to both zonal and meridional winds. The surprising results is found that, even for the complex situation, the northward transport of upper and intermediate water is given simply by ∮ τ dllplf, where fc is the average Coriolis parameter along a line connecting the southern tip of the Americas with the southern tip of Africa and τ is the wind stress along the integration path (I). This implies that, although the amount of high-latitude cooling is responsible for the location and manner in which bottom water is formed, it has very limited effect on the net meridional mass flux (which constitutes the so-called conveyor). Detailed application of the above formula to the Atlantic using actual geography and spherical coordinates as well as actual meridional and zonal winds (adopted from 40-yr averages given by NCEP) gives the reasonable estimate of 9 Sv (Sv ≡ 106 m3 s-:) for the transport of the conveyor upper limb."
"6603703438;6701413579;35497573900;7103211168;35584652300;","A uniform- and variable-resolution stretched-grid GCM dynamical core with realistic orography",2000,"10.1175/1520-0493(2000)128<1883:AUAVRS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033942437&doi=10.1175%2f1520-0493%282000%29128%3c1883%3aAUAVRS%3e2.0.CO%3b2&partnerID=40&md5=6bd59fa6ceeb5c515c9cdfcd048fa40f","The impact of introducing a realistic orographic forcing into a uniform- and variable-resolution stretched-grid GCM dynamical core is investigated by performing long-term and medium range integrations. Comparisons are made between various stretched-grid simulations and a control that consists of a uniform grid integration at high resolution. These comparisons include those where the orography has and has not been filtered to eliminate small-scale noise. Results from the region of interest with highest resolution show that 1) the stretched-grid GCM provides an efficient downscaling over the area of interest, that is, it properly simulates not only large-scale but also mesoscale features: and 2) the introduction of orography has a greater impact than the effect of stretching. Results presented here suggest that dynamical core integrations with both uniform and stretched grids should consider orographic forcing as an integral part of the model dynamics."
"6701676992;7006629146;","Reflection of planetary waves in three-dimensional tropospheric flows",1999,"10.1175/1520-0469(1999)056<0652:ROPWIT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033076750&doi=10.1175%2f1520-0469%281999%29056%3c0652%3aROPWIT%3e2.0.CO%3b2&partnerID=40&md5=4fcc17b1636ed5fb789951fc17eff221","The authors consider quasi-stationary planetary waves that are excited by localized midlatitude orographic forcing in a three-dimensional primitive-equation model. The waves propagate toward subtropical regions where the background flow is weak and the waves are therefore likely to break. Potential vorticity fields on isentropic surfaces are used to diagnose wave breaking. Nonlinear pseudomomentum conservation relations are used to quantify the absorption-reflection behavior of the wave-breaking regions. Three different three-dimensional flow configurations are represented: (i) a barotropic flow, (ii) a simple baroclinic flow, and (iii) a more realistic baroclinic flow. In order to allow the propagation of large-scale waves to be studied over extended periods for the baroclinic flows, the authors apply a mechanical damping at low levels to delay the onset of baroclinic instability. For basic states (i) and (ii) the forcing excites a localized wave train that propagates into the subtropics and, for large enough wave amplitude, gives rise to a reflected wave train propagating along a great circle route into midlatitudes. It is argued that the reflection is analogous to the nonlinear reflection predicted by Rossby wave critical layer theory. Both the directly forced wave train and the reflected wave train are quite barotropic in character and decay due to the damping. However, the low-level damping does not inhibit the reflection. The authors also consider the effect of thermal damping on the absorption-reflection behavior and find that, for realistic wave amplitudes, reflection is not inhibited by thermal damping with a timescale as low as 5 days. For the third basic state it is found that the small-amplitude response has the character of a longitudinally propagating wave train that slowly decays with distance away from the forcing. The authors argue that part of this decay is due to low-latitude absorption and show that at larger amplitudes the decay is inhibited by nonlinear reflection. The authors also compare for each basic state absorption-reflection behavior for isolated wave trains and for waves forced in a single longitudinal wavenumber."
"36869879700;7202386372;7406589460;7004091067;57201038190;","Numerical simulations of an observed gravity current and gravity waves in an environment characterized by complex stratification and shear",1996,"10.1175/1520-0469(1996)053<3570:NSOAOG>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030326368&doi=10.1175%2f1520-0469%281996%29053%3c3570%3aNSOAOG%3e2.0.CO%3b2&partnerID=40&md5=4f87707769408cf846501497822a3b4f","Numerical simulations of a gravity current in an environment characterized by complex stratification and vertical wind shear have been performed using a nonhydrostatic, two-dimensional, dry, primitive-equation model. Data from one of the most complete documentations to date of gravity waves associated with a gravity current, presented in an earlier study, are used both to prescribe the gravity current's environment and for validation of the simulated gravity current and its associated gravity waves. These comparisons indicate that the gravity current observed by a Doppler wind profiler and sodars was well simulated in terms of depth, density contrast, and propagation speed and that the model produced a variety of gravity waves similar in many ways to those observed. Because uncertainties remained concerning the gravity wave generation mechanisms derived from the observations (e.g., wavelengths were not observed), the validated simulations are used to test these tentative hypotheses. The simulations confirm that trapped lee-type gravity waves formed in response to flow over the head of the gravity current and that Kelvin-Helmholtz (KH) waves were created because of shear atop the cold air within the gravity current. The 2.8-km wavelength of the simulated KH waves agrees with the 2- to 3-km wavelength inferred from the observations. However, the 6.4-km wavelength of the simulated lee-type waves is significantly shorter than the 12.5-km wavelength inferred from the observational data, even though wave periods (20-23 minutes) are nearly identical. Sensitivity tests indicate that the curvature in the wind profile associated with the low-level opposing inflow and an elevated isothermal layer worked together to support the development of the trapped lee-type waves. The model produces a deep vertically propagating wave above the gravity current head that was not present in the observations. As deduced in the earlier study, sensitivity tests indicate that the prefrontal, near-surface stable layer was too shallow to support the generation of a bore; that is, conditions were supercritical. Synthesis of detailed observations and numerical simulations of these mesoscale phenomena thus offers the broadest examination possible of the complex physical processes."
"7102201685;7003496841;","Splitting methods for problems with different timescales",1994,"10.1175/1520-0493(1994)122<2614:SMFPWD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028583423&doi=10.1175%2f1520-0493%281994%29122%3c2614%3aSMFPWD%3e2.0.CO%3b2&partnerID=40&md5=f1fd3a02a0b14f9e429d1e7be42004e3","Using the mathematical analysis developed in a previous manuscript, it is shown that splitting schemes are not appropriate for badly skewed hyperbolic systems. In a number of atmospheric models, the semi-implicit method is used to treat the badly skewed vertical sound wave terms. This leads to the excitation of the high-frequency waves in a nonphysical manner. It is also shown that this is equivalent to solving the primitive equations; that is, a model using this method for the large-scale case will be ill posed at the lateral boundaries. -from Authors"
"36486213200;7102836087;","Localized forcing of slantwise motion at fronts",1991,"10.1002/qj.49711750104","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026278679&doi=10.1002%2fqj.49711750104&partnerID=40&md5=f94439b76ae705418d3d4f8a018dff4b","A cold front is here modelled as a baroclinic zone in which there is a local low‐level forcing of ageostrophic motion. Such forcing may result from the outflow from line‐convection at the surface front, or from synoptic‐scale frontogenesis, and is represented by a localized fixed region in which anomalies of the inertia and/or buoyancy of the air are imposed, either continuously or impulsively. The response to this forcing is described when the baroclinic flow is either unstable or weakly stable to symmetric instability. Such conditions are thought to be typical of cold fronts. The flow is examined using classical parcel theory, a (new) more complete parcel theory, a primitive‐equation numerical model, and the so‐called Geometric (or balanced) Model. The predicted motion involves a lens‐shaped area oriented along the sloping isentropes, with geometry dictated by the background potential vorticity and the imposed anomalies in inertia or buoyancy. The lens has zero or weakly negative potential vorticity, in the case of a background flow which is symmetrically stable. This lens, grown in a symmetrically stable atmosphere, is offered as an alternative explanation for the observed state of (moist) slantwise neutrality at a cold front, in contrast to that explanation which assumes an irreversible adjustment to symmetric instability. Copyright © 1991 Royal Meteorological Society"
"6602360644;35104377300;36239721900;20733375100;6601966393;35737196600;7004338399;6603820216;6603776561;","Off-shelf fluxes across the southern Adriatic margin: Factors controlling dense-water-driven transport phenomena",2016,"10.1016/j.margeo.2015.08.016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84951009687&doi=10.1016%2fj.margeo.2015.08.016&partnerID=40&md5=65d57b2a5e9c7d1c42b6b31952d52415","The northern Adriatic Sea is a basin where dense shelfwaters formduringwinters if the following favorable conditions are attained: high salinities, mainly related to low river water discharge (Po river in primis) during fall season, and strong heat fluxes induced by cold and dry Bora wind events blowing from north-east. Extremely favorable conditions to Northern Adriatic Dense Waters (NAdDW) formation characterized winter 2012 when, following several months of low Po river runoff, a strong event of Cold Air Outbreak (CAO) occurred from the end of January until mid-February. Consequently, the mean temperature of northern Adriatic waters dropped to about 6°C and exceptional densities (potential density anomaly locally exceeding 30.0 kgm-3)were reached. The production and spreadingmechanisms of densewater in the Adriatic Sea have beenmodeled bymeans of the COAWST (Coupled-Ocean-Atmosphere-Wave-Sediment-Transport) modeling system. The model builds upon a high-resolution (1 kmspaced horizontal grid), fully 3-D primitive equations hydrodynamicmodel coupledwith a phase-averaged wave model and sediment routines, and is driven by simulated atmospheric forcings. The dataset used to assess model outputs relies on the measurements acquired during the dedicated field campaigns ""Operation Dense Water"", a set of two rapid response cruises carried out in southern Adriatic during winter 2012, and by five mooring arrays deployed in the Southern Adriatic Margin (SAM) that allowed the continuous acquisition of temperature, salinity, currents and suspended matter samples. Results from the integrated data-model approach suggest that the NAdDW propagates along the shelf to the southern basin following both a shallower vein and a deeper stream,with a process characterized by a strong variability (mean value of 0.31 Sv with peaks rapidly growing in the first weeks after the CAO up to 2.19 Sv). Additionally, COAWST capability to couple different numericalmodels allowed to disentangle the relative importance of aspects on dense water generation, mixing and spreading, demonstrating how coupled runs can lead to volumes up to 50% largerwith respect to uncoupled simulations. Additional light is shed on the transport pathways off the shelf and on possible sediment transport phenomena in the area, in this benefiting froman unprecedented spatial resolution and a newbathymetry reflecting very high resolution data acquired viamulti-beamtechniques. Although densewater propagation appears as a relatively large-scale process involving thewholewestern side of the SAM, topographic local discontinuities and seabed slopes appear crucial in triggering descent and governing flow patterns. The presence of suspended sediment along the water column, despite not significantly influencing the overall fluxes across sections, is responsible of pulling part of the veins towards deeper zones. © 2015 Elsevier B.V."
"52263850600;31067496800;15765007300;","Dynamical core model intercomparison project: Tracer transport test cases",2014,"10.1002/qj.2208","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84902293585&doi=10.1002%2fqj.2208&partnerID=40&md5=670baa96c1933c5c9d7b209a7bf34da6","Three-dimensional advection tests are required to assess the ability of transport schemes of dynamical cores to model tracer transport on the sphere accurately. A set of three tracer-transport test cases for three-dimensional flow is presented. The tests focus on the physical and numerical issues that are relevant to three-dimensional tracer transport: positivity preservation, inter-tracer correlations, horizontal-vertical coupling, order of accuracy and choice of vertical coordinate. The first test is a three-dimensional deformational flow. The second test is a Hadley-like global circulation. The final test is a solid-body rotation test in the presence of rapidly varying orography. A variety of assessment metrics, such as error norms, convergence rates and mixing diagnostics, are used. The tests are designed for easy implementation within existing and developing dynamical cores and have been a cornerstone of the 2012 Dynamical Core Model Intercomparison Project (DCMIP). Example results are shown using the transport schemes in two dynamical cores: the Community Atmosphere Model finite-volume dynamical core (CAM-FV) and the cubed-sphere finite-volume MCore dynamical core. © 2013 Royal Meteorological Society."
"6602888227;7003876983;57213561342;15065565300;7201568549;7004070482;13406399300;15765007300;","Angular momentum budget in General Circulation Models of superrotating atmospheres: A critical diagnostic",2012,"10.1029/2012JE004223","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84871556318&doi=10.1029%2f2012JE004223&partnerID=40&md5=0ac77b106110c634d90df7e26574a8b6","To help understand the large disparity in the results of circulation modeling for the atmospheres of Titan and Venus, where the whole atmosphere rotates faster than the surface (superrotation), the atmospheric angular momentum budget is detailed for two General Circulation Models (GCMs). The LMD GCM is tested for both Venus (with simplified and with more realistic physical forcings) and Titan (realistic physical forcings). The Community Atmosphere Model is tested for both Earth and Venus with simplified physical forcings. These analyses demonstrate that errors related to atmospheric angular momentum conservation are significant, especially for Venus when the physical forcings are simplified. Unphysical residuals that have to be balanced by surface friction and mountain torques therefore affect the overall circulation. The presence of topography increases exchanges of angular momentum between surface and atmosphere, reducing the impact of these numerical errors. The behavior of GCM dynamical cores with regard to angular momentum conservation under Venus conditions provides an explanation of why recent GCMs predict dissimilar results despite identical thermal forcing. The present study illustrates the need for careful and detailed analysis of the angular momentum budget for any GCM used to simulate superrotating atmospheres. © 2012. American Geophysical Union. All Rights Reserved."
"15124698700;7401836526;","Weather-layer dynamics of baroclinic eddies and multiple jets in an idealized general circulation model",2008,"10.1175/2007JAS2280.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40949121531&doi=10.1175%2f2007JAS2280.1&partnerID=40&md5=c0c8d53bc51eb1706b17ffdd7afc5117","The general circulation and the behavior of multiple jets and baroclinic eddies are described for an atmosphere in which meridional potential temperature gradients and eddies are confined to a weather layer. The weather layer is separated from the frictional lower boundary by a statically stable barotropic layer with significant mass. Closure of the zonal momentum budget in the resulting circulation is achieved through ageostrophic meridional cells that extend to the lower boundary, at which momentum is dissipared: In a series of simulations with a multilevel primitive equation model, dynamic changes in the static stability of the weather layer are found to be critical in determining the scaling of the baroclinic eddies, an effect not captured in quasigeostrophic models. For simulations with a single jet in each hemisphere, the static stability of the weather layer adjusts so that a significant inverse energy cascade to scales larger than the Rossby deformation radius does not occur. The eddy length is found to scale with both the Rossby deformation radius and the Rhines scale. Simulations with larger planetary radii and low pole-to-equator temperature gradients exhibit multiple jets in each hemisphere. Eddy lengths and energies for the jet nearest the equator in each hemisphere have the same scaling as those in the single-jet simulations. Similar scalings are found for jets farther poleward but with different constants of proportionality that are consistent with more supercritical eddies. The local eddy length is found to have only a weak variation with latitude, and the local meridional jet spacing is found to scale with the local eddy length in all cases. Insights from the weather-layer simulations may be relevant to circulations in gas giant planets and the ocean. © 2008 American Meteorological Society."
"56247576300;","Information flow in ensemble weather predictions",2007,"10.1175/JAS3857.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34147129242&doi=10.1175%2fJAS3857.1&partnerID=40&md5=bacbffd3061137f2ce55e36bbe2024ae","In a weather prediction, information flows from the initial conditions to a later prediction. The uncertainty in the initial conditions implies that such a flow should be quantified with tools from probability theory. Using several recent developments in information theory, this flow is explored using a moderate-resolution primitive equation atmospheric model with simplified physics. Consistent with operational experience and other methodologies explored in the literature, such as singular vectors, it is found that the midlatitude flow is mainly in an easterly direction. At upper levels, the flow is primarily steered by advection of the jet stream; however, at low levels there is clear evidence that synoptic dynamics are important and this makes the direction of flow more complex. Horizontal rather than vertical flow is generally found to be more important, although there was evidence for propagation from the mid- to upper troposphere of zonal velocity. As expected, as the length of the prediction increases, more remote areas become important to local predictions. To obtain reliable/stable results, rather large ensembles are used; however, it is found that the basic qualitative results can be obtained with ensembles within present practical reach. The present method has the advantage that it makes no assumptions concerning linearity or ensemble Gaussianicity. © 2007 American Meteorological Society."
"9244992800;55716319700;","Preferred modes of variability and their relationship with climate change",2006,"10.1175/JCLI3705.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745252215&doi=10.1175%2fJCLI3705.1&partnerID=40&md5=7d5a919aa4fbf0197d7c5ba8347b273e","Spatial structure of annular modes shows a remarkable resemblance to that of the recent trend in the observed circulation (Thompson et al.). This study performs a series of multilevel primitive equation model simulations to examine the extent to which the annular mode is capable of predicting changes in the zonal-mean flow response to external heat perturbations. Each of these simulations represents a statistically steady state and differs from each other in the values of the imposed tropical heating (H) and high-latitude cooling (C). Defining the annula r mode as the first empirical orthogonal function (EOF1) of zonal-mean tropospheric zonal wind, it is found that the ""climate predictability"" is generally high in the small C-large H region of the parameter space, but is markedly low in the large C-small H region. In the former region, EOF1 represents meridional meandering of the midlatitude jet, while in the latter region, EOF1 and EOF2 combine to represent coherent poleward propagation of zonal-mean flow anomalies. It is also found that the climate predictability tends to be higher with respect to changes in C than to changes in H. The implications of these findings for the Southern Hemisphere climate predictability are also presented. © 2006 American Meteorological Society."
"56726831900;6602250413;7101630970;7202946344;","The counter-propagating Rossby-wave perspective on baroclinic instability. Part III: Primitive-equation disturbances on the sphere",2005,"10.1256/qj.04.22","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27644478671&doi=10.1256%2fqj.04.22&partnerID=40&md5=0e18774c9f02c6d7937a10c16dfa09c7","Baroclinic instability of perturbations described by the linearized primitive equations, growing on steady zonal jets on the sphere, can be understood in terms of the interaction of pairs of counter-propagating Rossby waves (CRWs). The CRWs can be viewed as the basic components of the dynamical system where the Hamiltonian is the pseudoenergy and each CRW has a zonal coordinate and pseudomomentum. The theory holds for adiabatic frictionless flow to the extent that truncated forms of pseudomomentum and pseudoenergy are globally conserved. These forms focus attention on Rossby wave activity. Normal mode (NM) dispersion re lations for realistic jets are explained in terms of the two CRWs associated with each unstable NM pair. Although derived from the NMs, CRWs have the conceptual advantage that their structure is zonally untilted, and can be anticipated given only the basic state. Moreover, their zonal propagation, phase-locking and mutual interaction can all be understood by 'PV-thinking' applied at only two 'home-bases' - potential vorticity (PV) anomalies at one home-base induce circulation anomalies, both locally and at the other home-base, which in turn can advect the PV gradient and modify PV anomalies there. At short wavelengths the upper CRW is focused in the mid-troposphere just above the steering level of the NM, but at longer wavelengths the upper CRW has a second wave-activity maximum at the tropopause. In the absence of meridional shear, CRW behaviour is very similar to that of Charney modes, while shear results in a meridional slant with height of the air-parcel displacement-structures of CRWs in sympathy with basic-state zonal angular-velocity surfaces. A consequence of this slant is that baroclinically growing eddies (on jets broader than the Rossby radius) must tilt downshear in the horizontal, giving rise to up-gradient momentum fluxes that tend to accelerate the barotropic component of the jet. © Royal Meteorological Society, 2005."
"7006421134;7004696243;","Excitation of transient waves by localized episodic heating in the tropics and their propagation into the middle atmosphere",1996,"10.2151/jmsj1965.74.2_189","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0040454929&doi=10.2151%2fjmsj1965.74.2_189&partnerID=40&md5=2e188b01d0b93ad475d9ac2612a090a2","Response of a resting spherical atmosphere to transient localized heating in the tropics is studied theoretically with linearized primitive equations. The method of separation of variables is used to solve the problem, and time-integrations of the full nonlinear equations are also done to assess the linearity of the response. The linearity of the response is good for some realistic values of the heating. The dominant responses are equatorially-trapped vertically propagating waves whose vertical scale matches that of the heating and global normal (or free) modes. In the middle atmosphere, the equatorially trapped waves respond effectively if the angular frequency is the order of 10 × [damping rate]. If the frequency is greater than this order, the response is suppressed in a stochastic sense; while if the frequency is less than this order, it is suppressed by the damping. Spatial pattern of the response is obtained for a realization of idealized stochastic heating with a Gaussian form in space and time. For the heating, of which the time scale is a few days or longer, horizontal cross sections of the response show the ""Gill pattern"" at the beginning and then the response disperses zonally in low latitudes. For short-lived heating, on the other hand, the gravity wave response expands concentrically at the beginning and then the response spreads zonally in low latitudes. Energy and momentum spectra to various kinds of wave are calculated for the stochastic heating. As the time scale of the heating events decreases, gravity-wave responses increase relatively to Rossby-wave responses. As the zonal scale of the heating events decreases, on the other hand, Rossby-wave responses slightly increase relatively to the gravity-wave responses. Heating just on the equator is less effective to excite Rossby waves than that off the equator. Energy and momentum of these vertically propagating waves are of comparable orders to those of the real atmosphere if the heating has an appropriate spectrum with a realistic amount comparable to the total latent heat release in the tropics; and so does the energy of global normal modes. Wave energy propagation into the middle atmosphere has to be taken into account even for the calculation of the transient response in the troposphere if the dominant frequency is larger than the damping rate."
"6602121676;7007021074;","An observational and prognostic numerical investigation of complex terrain dispersion",1995,"10.1175/1520-0450(1995)034<0650:AOAPNI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028810564&doi=10.1175%2f1520-0450%281995%29034%3c0650%3aAOAPNI%3e2.0.CO%3b2&partnerID=40&md5=3e813c97714d04831d370e2fbfd977d4","The Atmospheric Studies in Complex Terrain Program conducted a field experiment at the interface of the Rocky Mountains and the Great Plains in the winter of 1991. Extensive meteorological observation were taken in northeastern Colorado near Rocky Flats to characterize overnight conditions in the region. Simultaneously, a tracer dispersion experiment using over 130 samplers to track plume development was conducted by Rocky Flats facility personnel. These two datasets provided an opportunity to investigate the accuracy and applicability of a fully prognostic, primitive equation, mesoscale model to the simulation of complex terrain dispersion. -Authors"
"7102541338;7004360355;57203109046;8706262900;35596728700;","Global observations and modeling of nonmigrating diurnal tides generated by tide-planetary wave interactions",2015,"10.1002/2015JD023739","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84955193722&doi=10.1002%2f2015JD023739&partnerID=40&md5=827ec0221fca108eb5e7e8146c1edf05","Advective processes that couple planetary waves with tides have long been proposed as sources of nonmigrating diurnal tides. This paper reports observations of short-term variability in global observations of nonmigrating tides predicted to arise from the interaction of the migrating diurnal tide (DW1) with a quasi-stationary planetary wave number one (PW1). PW1 and tidal definitions are extracted from satellite temperatures and high-altitude meteorological analyses. During winter months, the evolution of westward traveling diurnal tides with zonal wave number 2 (DW2) generally tracks that of strong-amplitude stratospheric PW1. DW1 and PW1 spectra are used to compute nonlinear tidal forcing terms arising from advection. We then examine the response of a primitive equation model to the observation-based nonlinear forcing. The model experiments indicate that meridional advection of PW1 zonal momentum by DW1 is a significant source of lower thermospheric DW2. Modeled DW2 amplitudes are very consistent with observed DW2 amplitudes when stratospheric PW1 penetrates to equatorial latitudes. The model experiments also indicate that the interaction can imprint short-term variability associated with wintertime PW1 upon DW2 in the summer hemisphere and the lower thermosphere. © 2015. The Authors."
"57202299549;7006705919;7406243250;15765007300;","Short-term time step convergence in a climate model",2015,"10.1002/2014MS000368","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928780295&doi=10.1002%2f2014MS000368&partnerID=40&md5=d8bcfe004e06807a91cab9cc18d281c8","This paper evaluates the numerical convergence of very short (1 h) simulations carried out with a spectral-element (SE) configuration of the Community Atmosphere Model version 5 (CAM5). While the horizontal grid spacing is fixed at approximately 110 km, the process-coupling time step is varied between 1800 and 1 s to reveal the convergence rate with respect to the temporal resolution. Special attention is paid to the behavior of the parameterized subgrid-scale physics. First, a dynamical core test with reduced dynamics time steps is presented. The results demonstrate that the experimental setup is able to correctly assess the convergence rate of the discrete solutions to the adiabatic equations of atmospheric motion. Second, results from full-physics CAM5 simulations with reduced physics and dynamics time steps are discussed. It is shown that the convergence rate is 0.4 - considerably slower than the expected rate of 1.0. Sensitivity experiments indicate that, among the various subgrid-scale physical parameterizations, the stratiform cloud schemes are associated with the largest time-stepping errors, and are the primary cause of slow time step convergence. While the details of our findings are model specific, the general test procedure is applicable to any atmospheric general circulation model. The need for more accurate numerical treatments of physical parameterizations, especially the representation of stratiform clouds, is likely common in many models. The suggested test technique can help quantify the time-stepping errors and identify the related model sensitivities. © 2015. The Authors."
"37060344000;26643566500;7404955059;","The effects of the RAW filter on the climatology and forecast skill of the SPEEDY model",2011,"10.1175/2010MWR3530.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953229612&doi=10.1175%2f2010MWR3530.1&partnerID=40&md5=e2682926952581ff87a2c111535a31ad","In a recent study, Williams introduced a simple modification to the widely used Robert-Asselin (RA) filter for numerical integration. The main purpose of the Robert-Asselin-Williams (RAW) filter is to avoid the undesired numerical damping of theRAfilter and to increase the accuracy. In the present paper, the effects of the modification are comprehensively evaluated in the Simplified Parameterizations, Primitive Equation Dynamics (SPEEDY) atmospheric general circulation model. First, the authors search for significant changes in the monthly climatology due to the introduction of the new filter. After testing both at the local level and at the field level, no significant changes are found, which is advantageous in the sense that the new scheme does not require a retuning of the parameterized model physics. Second, the authors examine whether the new filter improves the skill of short- and medium-term forecasts. January 1982 data from the NCEP-NCAR reanalysis are used to evaluate the forecast skill. Improvements are found in all the model variables (except the relative humidity, which is hardly changed). The improvements increase with lead time and are especially evident in medium-range forecasts (96-144 h). For example, in tropical surface pressure predictions, 5-day forecasts made using the RAWfilter have approximately the same skill as 4-day forecasts made using the RA filter. The results of this work are encouraging for the implementation of the RAW filter in other models currently using the RA filter. © 2011 American Meteorological Society."
"36185311300;7005396385;55671920100;","On the three-dimensional residual mean circulation and wave activity flux of the primitive equations",2010,"10.2151/jmsj.2010-307","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954797261&doi=10.2151%2fjmsj.2010-307&partnerID=40&md5=934ed48132f66483ccb57121e2902ff5","The transformed Eulerian-mean (TEM) equations are useful in examining how the generation and/or dissipation of atmospheric waves drives the mean meridional circulation. However, the TEM equations do not provide a three-dimensional view of the transport. Several previous studies extended the TEM equation system to three dimensions but usually under the quasi-geostrophic assumption, which excludes small-scale phenomena such asgravity waves. Miyahara recently derived three-dimensional wave activity flux and the corresponding residual circulation applicable to gravity waves. However, his formulation has two flaws. First, the three-dimensional residual mean circulation does not satisfy the continuity equation. Second, the Eulerian-mean flow appears in the advection terms and the residual circulation appears in the Coriolis force term of the zonal momentum quation, unlike in the TEM one. The present study developed theoretical formulae of a three-dimensional residual mean circulation and wave activity flux on the basis of primitive equations that overcome these flaws. It is confirmed that the three-dimensional residual mean circulation accords with the sum of the Eulerian time-mean flow andthe Stokes drift and that the three-dimensional wave activity flux accords with the mean tangential forces across material surfaces corrugated by the waves under an assumption similar to the TEM equations. A simple physical meaning is given for the terms including the shear of time-mean flow in the three-dimensional wave activity flux. Moreover, the time mean tracer transport equation is derived using the three-dimensional residual mean circulation. A simple case study using the new formulae was made on the three-dimensional transport of stratospheric ozone in the Southern Hemisphere. It is shown that the product of the Coriolis parameter and the strong poleward/equatorward Stokes drifts also balances the divergence/convergence of the three-dimensional waveactivity flux. © 2010, Meteorological Society of Japan."
"37092322400;7202364010;7006245928;","Origin of the springtime westerly bias in equatorial Atlantic surface winds in the community Atmosphere Model version 3 (CAM3) simulation",2008,"10.1175/2008JCLI2138.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349115430&doi=10.1175%2f2008JCLI2138.1&partnerID=40&md5=a6f267fdac30a00598d807ce3f8712ff","This study makes the case that westerly bias in the surface winds of the National Center for Atmospheric Research (NCAR) Community Atmosphere Model, version 3 (CAM3), over the equatorial Atlantic in boreal spring has its origin in the rainfall (diabatic heating) bias over the tropical South American continent. The case is made by examination of the spatiotemporal evolution of regional precipitation and wind biases and by dynamical diagnoses of the westerly wind bias from experiments with a steady, linearized dynamical core of an atmospheric general circulation model. Diagnostic modeling indicates that underestimating rainfall over the eastern Amazon region can lead to the westerly bias in equatorial Atlantic surface winds. The study suggests that efforts to reduce coupled model biases, especially seasonal ones, must target continental biases, even in the deep tropics where ocean-atmosphere interaction generally rules. © 2008 American Meteorological Society."
"14324150200;7004912629;7005922032;","Implementation of a non-hydrostatic, adaptive-grid dynamics core in CAM3. Part I: Comparison of dynamics cores in aqua-planet simulations",2008,"10.1007/s00382-008-0381-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-54949154552&doi=10.1007%2fs00382-008-0381-y&partnerID=40&md5=cc005118da6a9d8f0244c752d5cc419b","We report on our implementation of EULAG as a dynamical core in the Community Atmospheric Model (CAM). EULAG is a non-hydrostatic, parallel computational model for all-scale geophysical flows. EULAG's name derives from its two computational options: EULerian (flux form) or semi-LAGrangian (advective form). The model combines nonoscillatory forward-in-time (NFT) numerical algorithms with a robust elliptic Krylov solver. A signature feature of EULAG is that it is formulated in generalized coordinates. In particular, this enables grid adaptivity. In total, these features give EULAG novel advantages over the existing dynamical cores in CAM. This paper uses a series of aqua-planet simulations to demonstrate that CAM-EULAG results compare favorably with those from CAM simulations at standard CAM resolution that use current finite volume or Eulerian-spectral dynamical core options. We also show that the grid adaptivity implemented in CAM3-EULAG allows higher resolution in selected regions without causing anomalous behavior such as spurious wave reflection. © Springer-Verlag 2008."
"7102495827;","A dynamical core with double Fourier series: Comparison with the spherical harmonics method",2006,"10.1175/MWR3121.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646458244&doi=10.1175%2fMWR3121.1&partnerID=40&md5=f6d8adcb62f0f0325554055ca0bc2100","A dynamical core of a general circulation model with the spectral method using double Fourier series (DFS) as basis functions is presented. The model uses the hydrostatic balance approximation and sigma coordinate system in the vertical direction and includes no topography. The model atmosphere is divided into 25 layers with equal sigma depths. Prognostic equations for the vorticity, divergence, temperature, and logarithmic surface pressure are solved by the DFS spectral-transform method with the Fourier filtering at middle and high latitudes. A semi-implicit time-stepping procedure, which deals with the eigendecomposition and inversion of the 3D Helmholtz equation associated with the gravity wave terms, is incorporated for the gravity wave-related terms. The DFS model is tested in terms of the solution of the 3D Helmholtz equation, balanced initial state, developing baroclinic waves, and short- and long-term Held-Suarez-Williamson simulations for T42, T62, T84, and T106 resolutions. It is found that the DFS model is stable and accurate and produces almost the same results as the spherical harmonics method (SHM). The normalized difference (i.e., L2 norm error) measured from the results of highest-resolution SHM-T106 showed a desirable convergence of the DFS solution with the resolution. The convergence property, however, varies with the test case and prognostic variables. The total mass (or global integrated surface pressure) is conserved to a good approximation in the long-term simulations. Computing on the high-performance computer NEC SX-5 (parallel-vector architecture) indicated that DFS is more efficient than the SHM and the efficiency increases with the resolution, for example, by factors of 2.09 and 7.68 for T212 and T1022, respectively. © 2006 American Meteorological Society."
"56322979700;7003871651;7004060399;7102167757;","Enhancement of Rossby wave breaking by steep potential vorticity gradients in the winter stratosphere",2004,"10.1175/1520-0469(2004)061<0904:EORWBB>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2342464884&doi=10.1175%2f1520-0469%282004%29061%3c0904%3aEORWBB%3e2.0.CO%3b2&partnerID=40&md5=47804acdabbd52e3e4c9f5903f366790","This work investigates the extent to which potential vorticity gradients affect the vertical propagation of planetary-scale Rossby waves on the edge of a stratospheric polar vortex and their eventual nonlinear saturation and breaking. Using two different numerical modeling approaches, it is shown that wave propagation and wave breaking are significantly reduced when the potential vorticity gradients at the vortex edge are anomalously weak. The efficiency of the first model, based on high-resolution contour dynamics, permits a full exploration of the parameter space of wave forcing amplitude and edge steepness. A more realistic primitive equation model in spherical geometry both confirms the contour dynamics results and highlights some direct implications for stratospheric modeling in more comprehensive models. The results suggest that stratospheric models using horizontal resolutions of spectral T42 or less may significantly underestimate the vertical propagation and breaking of planetary waves, and may consequently misrepresent such important stratospheric processes as the mean meridional circulation, sudden warmings, and the mixing of chemically distinct polar and midlatitude air. © 2004 American Meteorological Society."
"7202048299;7004188723;","Dynamic stabilization of atmospheric single column models",2004,"10.1175/1520-0442(2004)017<1004:DSOASC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0347890119&doi=10.1175%2f1520-0442%282004%29017%3c1004%3aDSOASC%3e2.0.CO%3b2&partnerID=40&md5=919c60a498f49dfa371390af6c0d3f4c","Single column models (SCMs) provide an economical framework for assessing the sensitivity of atmospheric temperature and humidity to natural and imposed perturbations, and also for developing improved representations of diabatic processes in weather and climate models. Their economy is achieved at the expense of ignoring interactions with the circulation dynamics; thus, advection by the large-scale flow is either prescribed or neglected. This artificial decoupling of the diabatic and adiabatic tendencies can often cause rapid error growth in SCM integrations, especially in the Tropics where large-scale vertical advection is important. As a result, SCMs can quickly develop highly unrealistic thermodynamic structures, making it pointless to study their subsequent evolution. This paper suggests one way around this fundamental difficulty through a simple coupling of the diabatic and adiabatic tendencies. In essence, the local vertical velocity m any instant is specified by a formula that links the local vertical temperature advection to the evolution of SCM-generated diabatic heating rates up to that instant. This vertical velocity is then used to determine vertical humidity advection, and also horizontal temperature and humidity advection under an additional assumption that the column is embedded in a uniform environment. The parameters in the formula are estimated in a separate set of calculations. from the approach to equilibrium of a linearized global primitive equation model forced by steady heat sources. As a test, the parameterized dynamics are used to predict the linear model's local response to oscillating heat sources, and found to perform remarkably well over a wide range of space and time scales. In a second test, the parameterization is found to capture important aspects of a general circulation model's vertical advection and temperature tendencies and their lead-lag relationships with diabatic heating fluctuations at convectively active locations in the Tropics. When implemented in the NCAR SCM, the dynamically coupled SCM shows a clear improvement over its uncoupled counterpart for tropical conditions observed during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Coupling effectively stabilizes the SCM. As a result. short-term prediction errors are substantially reduced, the ensemble spread is reduced in ensemble runs, and the SCM is able to maintain realistic thermodynamic structures in extended runs. Such a dynamically coupled SCM should therefore be more useful not only for isolating, physical parameterization errors in weather and climate models, but also for economical simulations of regional climate variability. © 2004 American Meteorological Society."
"7004069241;57193921169;","The deep-atmosphere Euler equations in a generalized vertical coordinate",2003,"10.1175//2564.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141682986&doi=10.1175%2f%2f2564.1&partnerID=40&md5=35c6b26ed6000b12a570c39e6be4b82d","Previous analysis of the hydrostatic primitive equations using a generalized vertical coordinate is extended to the deep-atmosphere nonhydrostatic Euler equations, and some special vertical coordinates of interest are noted. Energy and axial angular momentum budgets are also derived. This would facilitate the development of conserving finite-difference schemes for deep-atmosphere models. It is found that the implied principles of energy and axial angular momentum conservation depend on the form of the upper boundary. In particular, for a modeled atmosphere of finite extent, global energy conservation is only obtained for a rigid lid, fixed in space and time. To additionally conserve global axial angular momentum, the height of the lid cannot vary with longitude."
"55739579300;55716319700;","Hadley cell dynamics in a primitive equation model. Part I: Axisymmetric flow",2001,"10.1175/1520-0469(2001)058<2845:HCDIAP>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035482947&doi=10.1175%2f1520-0469%282001%29058%3c2845%3aHCDIAP%3e2.0.CO%3b2&partnerID=40&md5=c7557138c6872d3cb68fa7701a8cce5e","A strategy is adopted that applies the mean meridional circulation (MMC) equation to two different steady states of a primitive equation model. This allows for the investigation of the mechanisms behind the sensitivity of the Hadley cell structure to individual source terms in an axisymmetric circulation. Specifically, the strategy allows the MMC response to the individual source terms to be partitioned into direct and indirect components. The model's Hadley cell strengthens and broadens as the viscosity of the model is increased. It is found that a substantial portion of this sensitivity is attributable to diabatic heating and surface friction changes, which are ultimately induced by changes in viscosity. Similar behavior is found as the meridional gradient of the radiative-convective equilibrium temperature is increased, except that in this case the indirect response arises through the viscosity and surface friction change. In both cases, the changes in the static stability change are found to be of secondary importance. It is found that the latitudinal extent of the Hadley cell is more sensitive to the meridional temperature gradient than to the static stability. However, when the static stability is decreased (increased) by a sufficient amount, the Hadley cell becomes narrower (broader). Additional analyses indicate that the change in Hadley cell width is a response to the change in Hadley cell strength."
"8152726300;7003971889;6603585706;","Rayleigh friction, Newtonian cooling, and the linear response to steady tropical heating",2000,"10.1175/1520-0469(2000)057<1937:RFNCAT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034209687&doi=10.1175%2f1520-0469%282000%29057%3c1937%3aRFNCAT%3e2.0.CO%3b2&partnerID=40&md5=14740ab57d75aa84383eb133423c72a7","A series of studies are performed to examine the response of the tropical atmosphere to a prescribed steady, large-scale, elevated heat source (i.e., a region of persistent precipitation). Special emphasis is placed on the surface wind response in two idealized cases in which dissipation is achieved exclusively by Rayleigh friction or by Newtonian cooling. Starting from the linearized equations on an equatorial beta plane, theoretical arguments are presented that suggest there are qualitative differences in the solutions of these two models. A dry spectral primitive equation model of the atmosphere is employed and confirms the results obtained from the analytical studies. The results from both the analytical study and the numerical simulations are consistent in showing that Rayleigh friction and Newtonian cooling play totally different roles in the tropical atmosphere. Newtonian cooling homogenizes the atmospheric motion in the vertical direction, and a strong, vertically uniform wind is found below the base of the heat source. When Rayleigh friction dominates, the circulation driven by the heat source is confined to the layer where the heat source is located. It is also shown that a strong Hadley circulation is associated with reasonable strong Rayleigh friction, but not with Newtonian cooling alone. Finally, the numerical solution is found for the case where Newtonian cooling acts uniformly in the vertical and Rayleigh friction is included in the lower atmosphere to mimic crudely the dissipation of momentum in the boundary layer. The introduction of the simple boundary layer dramatically reduces the surface circulation that was supported in the Newtonian cooling alone case. Together these results suggest a significant surface circulation is unlikely to be driven by an elevated heat source if it resides above the top of the boundary layer.A series of studies are performed to examine the response of the tropical atmosphere to a prescribed steady, large-scale, elevated heat source (i.e., a region of persistent precipitation). Special emphasis is placed on the surface wind response in two idealized cases in which dissipation is achieved exclusively by Rayleigh friction or by Newtonian cooling. Starting from the linearized equations on an equatorial beta plane, theoretical arguments are presented that suggest there are qualitative differences in the solutions of these two models. A dry spectral primitive equation model of the atmosphere is employed and confirms the results obtained from the analytical studies. The results from both the analytical study and the numerical simulations are consistent in showing that Rayleigh friction and Newtonian cooling play totally different roles in the tropical atmosphere. Newtonian cooling homogenizes the atmospheric motion in the vertical direction, and a strong, vertically uniform wind is found below the base of the heat source. When Rayleigh friction dominates, the circulation driven by the heat source is confined to the layer where the heat source is located. It is also shown that a strong Hadley circulation is associated with reasonable strong Rayleigh friction, but not with Newtonian cooling alone. Finally, the numerical solution is found for the case where Newtonian cooling acts uniformly in the vertical and Rayleigh friction is included in the lower atmosphere to mimic crudely the dissipation of momentum in the boundary layer. The introduction of the simple boundary layer dramatically reduces the surface circulation that was supported in the Newtonian cooling alone case. Together these results suggest a significant surface circulation is unlikely to be driven by an elevated heat source if it resides above the top of the boundary layer."
"7102439098;7005173878;7006248174;7006558339;","The bomb 14C transient in the Pacific Ocean",2000,"10.1029/1999jc900228","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033670299&doi=10.1029%2f1999jc900228&partnerID=40&md5=810fd91f0e95d4816194f131deadb7ea","A modeling study of the bomb 14C transient is presented for the Pacific Ocean. A primitive equation ocean circulation model has been configured for a high-resolution domain that accounts for the Indonesian Throughflow (ITF). Four separate runs were performed: (1) seasonal forcing with 20 Sv of ITF transport, (2) seasonal forcing with 10 Sv of ITF transport, (3) seasonal forcing with no ITF transport, and (4) interannual forcing with 15 Sv of ITF transport. This study has two main objectives. First, it is intended to describe the time evolution of the bomb 14C transient. This serves as a tool with which one can identify the physical processes controlling the evolving bomb 14C distribution in the Pacific thermocline and thus provides an interpretive framework for the database of Δ14C measurements in the Pacific. Second, transient tracers are applied to the physical oceanographic problem of intergyre exchange. This is of importance in furthering our understanding of the potential role of the upper Pacific Ocean in climate variability. We use bomb 14C as a dye tracer of intergyre exchange between the subtropical gyres and the equatorial upwelling regions of the equatorial Pacific. Observations show that while the atmospheric Δ14C signal peaked in the early to mid-1960s, the Δ14C levels in the surface water waters of the subtropical gyres peaked near 1970, and the Δ14C of surface waters in the equatorial Pacific continued to rise through the 1980s. It is shown that the model exhibits skill in representing the large-scale observed features observed for the bomb C transient in the Pacific Ocean. The model successfully captures the basin-scale inventories of bomb 14C in the tropics as well as in the extratropics of the North Pacific. For the equatorial Pacific this is attributed to the model's high meridional resolution. The discrepancies in the three-dimensional distribution of bomb 14C between the model and data are discussed within the context of the dynamical controls on the Δ14C distribution of bomb 14C in the Pacific. Copyright 1999 by the American Geophysical Union."
"7409830026;7409506465;7409593771;7409779886;","The effect of dust radiative heating on low-level frontogenesis",1995,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029412336&partnerID=40&md5=75f8d0378b1ef16f0081fdc94b5f15fc","Severe dust storms frequently occur over northwestern China during spring. In this paper, numerical simulations are performed to examine the effect of dust radiative heating on surface frontogenesis. The absorption and multiple scattering of the dust are included in an atmospheric radiation scheme. A two-dimensional primitive equation model with 20 levels in the vertical is used for idealized simulations. The results show positive interaction between low-level frontogenesis and dust radiative heating. The adiabatic frontogenesis forcing is enhanced by the feedback of the dust radiative heating. These results suggest that the dust heating can significantly affect mesoscale weather systems in arid and desert regions. -from Authors"
"35330117400;","Nonlinear normal mode initialization and the bounded derivative method",1982,"10.1029/RG020i003p00385","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020335781&doi=10.1029%2fRG020i003p00385&partnerID=40&md5=9651c15fb406083ae1b679f6b4cb08b4","Recently, two new approaches have been proposed for the initialization of primitive equation models. One is called the nonlinear normal mode procedure, developed by Baer and Machenhauer. It is suitable for a global primitive equation model in which the construction of the model normal modes is feasible. The other approach is called the bounded derivative method, proposed by Kreiss. It can be applicable to both pure initial value and initial boundary value problems. Leith established a connection between the nonlinear normal mode procedure and the classical balancing based on quasi‐geostrophic theory. The purpose of this paper is to compare the three procedures of initialization for a baroclinic primitive equation model with beta plane geometry in pressure coordinates. To the degree of approximation employed, the initialization by the bounded derivative method agrees with the classical balance procedure with quasi‐geostrophic assumptions. We demonstrate for the same prediction model that nonlinear normal mode balancing leads to an initialization scheme identical to the one derived from the bounded derivative method within the degree of approximations. Since both new approaches to initialization are more general than the classical procedures, the connection of the two approaches with the quasi‐geostrophic formulation will enhance our understanding of the dynamics of large‐scale motions beyond the classical quasi‐geostrophic theory. This paper is not subject to U.S. copyright. Published in 1982 by the American Geophysical Union."
"57202535936;6603699044;26536715700;","Validation of mountain precipitation forecasts from the convection-permitting NCAR ensemble and operational forecast systems over the western United States",2018,"10.1175/WAF-D-17-0144.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048660596&doi=10.1175%2fWAF-D-17-0144.1&partnerID=40&md5=0704ddff972c7a3e74d49321e6f20608","Convection-permitting ensembles can capture the large spatial variability and quantify the inherent uncertainty of precipitation in areas of complex terrain; however, such systems remain largely untested over the western United States. In this study, we assess the capabilities of deterministic and probabilistic cool-season quantitative precipitation forecasts (QPFs) produced by the 10-member, convection-permitting (3-km horizontal grid spacing) NCAR Ensemble using observations collected by SNOTEL stations at mountain locations across the western United States and precipitation analyses from PRISM. We also examine the performance of operational forecast systems run by NCEP including the High Resolution Rapid Refresh (HRRR) model, the NAM forecast system with a 3-km continental United States (CONUS) nest, GFS, and the Short-Range Ensemble Forecast system (SREF). Overall, we find that higher-resolution models, such as the HRRR, NAM-3km CONUS nest, and an individual member of the NCAR Ensemble, are more deterministically skillful than coarser models, especially over the narrow interior ranges of the western United States, likely because they better resolve topography and thus better simulate orographic precipitation. The 10-member NCAR Ensemble is also more probabilistically skillful than 13-member subensembles composed of each SREF dynamical core, but less probabilistically skillful than the full 26-member SREF, as a result of insufficient spread. These results should help guide future short-range model development and inform forecasters about the capabilities and limitations of several widely used deterministic and probabilistic modeling systems over the western United States. © 2018 American Meteorological Society."
"7203088716;","Mean-flow effects of thermal tides in the mesosphere and lower thermosphere",2017,"10.1175/JAS-D-16-0194.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020316989&doi=10.1175%2fJAS-D-16-0194.1&partnerID=40&md5=6a6c101b0654981e2c6b84b9b01154ed","This study addresses the heat budget of the mesosphere and lower thermosphere with regard to the energy deposition of upward-propagating waves. To this end, the energetics of gravity waves are recapitulated using an anelastic version of the primitive equations. This leads to an expression for the energy deposition of waves that is usually resolved in general circulation models. The energy deposition is shown to be mainly due to the frictional heating and, additionally, due to the negative buoyancy production of wave kinetic energy. The frictional heating includes contributions from horizontal and vertical momentum diffusion, as well as from ion drag. This formalism is applied to analyze results from a mechanistic middle-atmosphere general circulation model that includes energetically consistent parameterizations of diffusion, gravity waves, and ion drag. This paper estimates 1) the wave driving and energy deposition of thermal tides, 2) the model response to the excitation of thermal tides, and 3) the model response to the combined energy deposition by parameterized gravity waves and resolved waves. It is found that thermal tides give rise to a significant energy deposition in the lower thermosphere. The temperature response to thermal tides is positive. It maximizes at polar latitudes in the lower thermosphere as a result of poleward circulation branches that are driven by the predominantly westward Eliassen-Palm flux divergence of the tides. In addition, thermal tides give rise to a downward shift and reduction of the gravity wave drag in the upper mesosphere. Including the energy deposition in the model causes a substantial warming in the upper mesosphere and lower thermosphere. © 2017 American Meteorological Society."
"55765793100;56271269000;7201646015;55396541600;","The dynamics of Southern Ocean storm tracks",2015,"10.1175/JPO-D-14-0075.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924964849&doi=10.1175%2fJPO-D-14-0075.1&partnerID=40&md5=7d66be6d56f1ce06eba01eed4196cc74","The mechanisms that initiate and maintain oceanic ""storm tracks"" (regions of anomalously high eddy kinetic energy) are studied in a wind-driven, isopycnal, primitive equation model with idealized bottom topography. Storm tracks are found downstream of the topography in regions strongly influenced by a largescale stationary meander that is generated by the interaction between the background mean flow and the topography. In oceanic storm tracks the length scale of the stationary meander differs from that of the transient eddies, a point of distinction from the atmospheric storm tracks. When the zonal length and height of the topography are varied, the storm-track intensity is largely unchanged and the downstream storm-track length varies only weakly. The dynamics of the storm track in this idealized configuration are investigated using a wave activity flux (related to the Eliassen-Palmflux and eddy energy budgets). It is found that vertical fluxes of wave activity (which correspond to eddy growth by baroclinic conversion) are localized to the region influenced by the standing meander. Farther downstream, organized horizontal wave activity fluxes (which indicate eddy energy fluxes) are found. A mechanism for the development of oceanic storm tracks is proposed: the standing meander initiates localized conversion of energy from the mean field to the eddy field, while the storm track develops downstream of the initial baroclinic growth through the ageostrophic flux ofMontgomery potential. Finally, the implications of this analysis for the parameterization and prediction of storm tracks in ocean models are discussed. © 2015 American Meteorological Society."
"57202299549;6603247427;55930419900;","Ensemble Held-Suarez test with a spectral transform model: Variability, sensitivity, and convergence",2008,"10.1175/2007MWR2044.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44449094063&doi=10.1175%2f2007MWR2044.1&partnerID=40&md5=1ee8b7e1515229868ba800e706282971","The idealized test case proposed by Held and Suarez is carried out with the atmospheric general circulation model ECHAM5 of the Max Planck Institute for Meteorology. The aim is to investigate the sensitivity of the solutions of the spectral dynamical core to spatial and temporal resolution, and to evaluate the numerical convergence of the solutions. Low-frequency fluctuations at time scales as long as thousands of days are found in ultralong integrations. To distinguish the effect of changed resolution from the fluctuations caused by the internal variability, the ensemble method is employed in experiments at resolutions ranging from T31 to T159 with 16 to 81 vertical levels. Significance of the differences between ensembles is assessed by three different statistical tests. Convergence property of the numerical solution is concisely summarized by a ratio index. Results show that the simulated climate state in the Held-Suarez test is sensitive to spatial resolution. Increase of horizontal resolution leads to slight weakening and poleward shift of the westerly jets. Significant warming is detected in high latitudes, especially near the polar tropopause, while the tropical tropopause becomes cooler. The baroclinic wave activity intensifies considerably with increased horizontal resolution. Higher vertical resolution also leads to stronger eddy variances and cooling near the tropical tropopause, but equatorward shift of the westerly jets. The solutions show an indication of convergence at T85L31 resolution according to all the three statistical tests applied. Differences between integrations with various time steps are judged to be within the noise level induced by the inherent low-frequency variability. © 2008 American Meteorological Society."
"7003467276;6507815511;7003531755;35894581100;","Tropical Pacific-driven decadal energy transport variability",2005,"10.1175/JCLI3389.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-24644525108&doi=10.1175%2fJCLI3389.1&partnerID=40&md5=fdc82f45611468847c236435fb7fde92","The atmospheric energy transport variability associated with decadal sea surface temperature variability in the tropical Pacific is studied using an atmospheric primitive equation model coupled to a slab mixed layer. The decadal variability is prescribed as an anomalous surface heat flux that represents the reduced ocean heat transport in the tropical Pacific when it is anomalously warm. The atmospheric energy transport increases and compensates for the reduced ocean heat transport. Increased transport by the mean meridional overturning (i.e., the strengthening of the Hadley cells) causes increased poleward energy transport. The subtropical jets increase in strength and shift equatorward, and in the midlatitudes the transients are affected. NCEP-NCAR reanalysis data show that the warming of the tropical Pacific in the 1980s compared to the early 1970s seems to have caused very similar changes in atmospheric energy transport indicating that these atmospheric transport variations were driven from the tropical Pacific. To study the implication of these changes for the coupled climate system an ocean model is driven with winds obtained from the atmosphere model. The poleward ocean heat transport increased when simulated wind anomalies associated with decadal tropical Pacific variability were used, showing a negative feedback between decadal variations in the mean meridional circulation in the atmosphere and in the Pacific Ocean. The Hadley cells and subtropical cells act to stabilize each other on the decadal time scale. © 2005 American Meteorological Society."
"7103342287;7004014731;","Three-dimensionality and forcing of the Brewer-Dobson circulation",2002,"10.1175/1520-0469(2002)059<0976:TDAFOT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036326764&doi=10.1175%2f1520-0469%282002%29059%3c0976%3aTDAFOT%3e2.0.CO%3b2&partnerID=40&md5=0b672f4e9a282164fe2c0fc0f1616415","Integrations with the nonlinear primitive equations are used to study 3D diabatic structure underlying the Brewer-Dobson circulation of the middle atmosphere. Such structure reveals zonally asymmetric contributions to mean downwelling over the winter hemisphere. It is used to evaluate contributions to w̄* from mechanical dissipation of planetary waves, associated with irreversible eddy dispersion and from thermal dissipation of planetary waves, associated with irreversible heat transfer. Zonal-mean downwelling follows disproportionately from those longitudes where air is deflected across contours of radiative equilibrium. This zonally asymmetric contribution to w̄* is pronounced at high latitudes, where the displaced vortex achieves cross-polar flow that drives air across sharply different radiative environments. Air parcels orbiting about the vortex then experience a wide swing in radiative-equilibrium temperature, driving them well out of thermal equilibrium. This renders the heat transfer experienced by them irreversible, resulting in net cooling and descent to lower χ with each orbit about the displaced vortex. By destroying anomalous potential vorticity (PV), irreversible heat transfer also leads to thermal dissipation of planetary waves and acts to resymmetrize the vortex diabatically. Integrations in which irreversible dispersion is suppressed recover much the same diabatic motion as the full integration. Downwelling is reduced at midlatitudes, where the contribution from irreversible eddy dispersion is concentrated, but it is virtually unchanged at high latitudes, where the contribution from irreversible heat transfer prevails. Lagrangian integrations show that thermal dissipation of wave activity accounts for a major fraction of the downwelling over the winter hemisphere. This is especially true at high latitudes, where cross-polar flow leads to irreversible cooling and a systematic drift of air to lower χ. Were it not for this contribution to w̄*, the Arctic stratosphere would be several tens of Kelvin colder."
"55996815000;7103294731;","The middle-atmosphere Hadley circulation and equatorial inertial adjustment",2001,"10.1175/1520-0469(2001)058<3077:TMAHCA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035513339&doi=10.1175%2f1520-0469%282001%29058%3c3077%3aTMAHCA%3e2.0.CO%3b2&partnerID=40&md5=c1c9d157426489ac3d0608f987215461","In the tropical middle atmosphere the climatological radiative equilibrium temperature is inconsistent with gradient-wind balance and the available angular momentum, especially during solstice seasons. Adjustment toward a balanced state results in a type of Hadley circulation that lies outside the ""downward control"" view of zonally averaged dynamics. This middle-atmosphere Hadley circulation is reexamined here using a zonally symmetric balance model driven through an annual cycle. It is found that the inclusion of a realistic radiation scheme leads to a concentration of the circulation near the stratopause and to its closing off in the mesosphere, with no need for relaxational damping or a rigid lid. The evolving zonal flow is inertially unstable, leading to a rapid process of inertial adjustment, which becomes significant in the mesosphere. This short-circuits the slower process of angular momentum homogenization by the Hadley circulation itself, thereby weakening the latter. The effect of the meridional circulation associated with extratropical wave drag on the Hadley circulation is considered. It is shown that the two circulations are independent for linear (quasigeostrophic) zonal-mean dynamics, and interact primarily through the advection of temperature and angular momentum. There appears to be no significant coupling in the deep Tropics via temperature advection since the wave-driven circulation is unable to alter meridional temperature gradients in this region. However, the wave-driven circulation can affect the Hadley circulation by advecting angular momentum out of the Tropics. The validity of the zonally symmetric balance model with parameterized inertial adjustment is tested by comparison with a three-dimensional primitive equations model. Fields from a middle-atmosphere GCM are also examined for evidence of these processes. While many aspects of the GCM circulation are indicative of the middle-atmosphere Hadley circulation, particularly in the upper stratosphere, it appears that the circulation is obscured in the mesosphere and lower stratosphere by other processes."
"6506725113;6701843355;6603829010;","Variational Assimilation of Tropical Atmosphere-Ocean and expendable bathythermograph data in the Hamburg Ocean Primitive Equation ocean general circulation model, adjusting the surface fluxes in the tropical ocean",2001,"10.1029/1999jc000136","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034820012&doi=10.1029%2f1999jc000136&partnerID=40&md5=fc09385a8afa8be85db11e58478fc2a4","A four-dimensional variational method has been developed that assimilates expandable bathythermograph and Tropical Atmosphere-Ocean subsurface temperature data into the Hamburg Ocean Primitive Equation model. The method decreases the misfit between model and observed ocean temperatures by adjusting the surface forcing. The main goal of the assimilation scheme is to improve ocean analyses in the tropical Pacific. As a first study, only wind stress is adjusted in the assimilation. In two identical twin experiments it is demonstrated that the scheme works well in the equatorial Pacific. The scheme is capable of reducing errors in the ocean analysis that originate either from the wind stress forcing or the initial state. The impact of model errors on the data assimilation is investigated in a experiment with real observations. In this experiment the temperature innovations near the equator are comparable to those of an optimal interpolation data assimilation scheme. Copyright 2001 by the American Geophysical Union."
"6701726931;7006629146;","Mechanisms for wave packet formation and maintenance in a quasigeostrophic two-layer model",1999,"10.1175/1520-0469(0)056<2457:MFWPFA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032779124&doi=10.1175%2f1520-0469%280%29056%3c2457%3aMFWPFA%3e2.0.CO%3b2&partnerID=40&md5=20e285bec4269e2ca286f743e8dabfd9","A quasigeostrophic, two-layer, β-plane channel model is used to investigate the dynamics of baroclinic wave packets. A series of experiments are performed in which an unstable flow is maintained by lower-level Ekman friction and radiative relaxation toward a temperature profile that corresponds to a broad parabolic upper-level jet. The final statistically steady state achieved in each experiment is found to depend on the magnitude of the hyperdiffusivity ν(o) and the supercriticality, which is controlled by β. The most important qualitative difference in such states between experiments is found to be the degree to which a waveguide in the upper level is found to develop. The mechanism for this upper-level waveguide development is the mixing effect of the eddies at the flanks of the jet, which leads to a strong potential vorticity gradient at the center of the channel, with well-mixed regions to the north and south. Two distinct regimes with different qualitative behavior are observed and illustrated by two particular experiments. In the first regime strong hyperdiffusivity inhibits the development of the waveguide. Steady wave packets are shown to stabilize the background flow upstream by increasing the meridional shear of the jet. This upstream stabilization is argued to be a mechanism for packet maintenance in this regime. In the second regime the diffusivity is lower, and a well-developed upper-level waveguide results. The wave packets in this regime are unsteady and are shown to stabilize the background flow at, and slightly upstream of, their maxima. Wave activity diagnostics suggest that the most important mechanism in maintaining these packets is the zonal convergence of wave activity, indicating that the wave packets are undergoing a form of nonlinear self-focusing, analogous to that identified in weakly nonlinear models. Finally, results are presented from a 10-level primitive equation model with parameter values relevant to the real atmosphere. In this experiment the nonlinear response of the background flow to the wave packets is shown to be qualitatively very similar to that observed in the low-diffusivity two-layer model experiment.A quasigeostrophic, two-layer, β-plane channel model is used to investigate the dynamics of baroclinic wave packets. A series of experiments are performed in which an unstable flow is maintained by lower-level Ekman friction and radiative relaxation toward a temperature profile that corresponds to a broad parabolic upper-level jet. The final statistically steady state achieved in each experiment is found to depend on the magnitude of the hyperdiffusivity v0 and the supercriticality, which is controlled by β. The most important qualitative difference in such states between experiments is found to be the degree to which a waveguide in the upper level is found to develop. The mechanism for this upper-level waveguide development is the mixing effect of the eddies at the flanks of the jet, which leads to a strong potential vorticity gradient at the center of the channel, with well-mixed regions to the north and south. Two distinct regimes with different qualitative behavior are observed and illustrated by two particular experiments. In the first regime strong hyperdiffusivity inhibits the development of the waveguide. Steady wave packets are shown to stabilize the background flow upstream by increasing the meridional shear of the jet. This upstream stabilization is argued to be a mechanism for packet maintenance in this regime. In the second regime the diffusivity is lower, and a well-developed upper-level waveguide results. The wave packets in this regime are unsteady and are shown to stabilize the background flow at, and slightly upstream of, their maxima. Wave activity diagnostics suggest that the most important mechanism in maintaining these packets is the zonal convergence of wave activity, indicating that the wave packets are undergoing a form of nonlinear self-focusing, analogous to that identified in weakly nonlinear models. Finally, results are presented from a 10-level primitive equation model with parameter values relevant to the real atmosphere. In this experiment the nonlinear response of the background flow to the wave packets is shown to be qualitatively very similar to that observed in the low-diffusivity two-layer model experiment."
"36992744000;15765007300;7406243250;","Tropical cyclones in the spectral element configuration of the Community Atmosphere Model",2012,"10.1002/asl.399","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867932009&doi=10.1002%2fasl.399&partnerID=40&md5=382b84066f51151294ccadc41ea266d3","This paper explores the evolution of idealized tropical cyclones in the Community Atmosphere Model CAM 5 with the spectral element (SE) dynamical core at grid spacings of 111, 55 and 28 km.Over 10 simulation days the storms become increasingly intense and compact with increasing resolution.The experiments reveal unrealistically strong tropical cyclone intensities of minimum surface pressures ranging from 845 to 865 hPa and absolute maximum wind speeds greater than 100 m s -1 at the highest resolution, especially when small physics time steps are used.This unphysical behavior is related to the manner in which the physics time step is applied in CAM 5.The analysis indicates that the behavior of the physics parameterizations, namely the partitioning between convective and large-scale precipitation, at small time steps contributes to this intensity. © 2012 Royal Meteorological Society."
"6507253177;7003991093;","Equilibration of baroclinic turbulence in primitive equations and quasigeostrophic models",2009,"10.1175/2008JAS2848.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-69849086463&doi=10.1175%2f2008JAS2848.1&partnerID=40&md5=75991aa8fe9f4a08d26609cc67c1ac72","This paper investigates the equilibration of baroclinic turbulence in an idealized, primitive equation, two-level model, focusing on the relation with the phenomenology of quasigeostrophic turbulence theory. Simulations with a comparable two-layer quasigeostrophic model are presented for comparison, with the deformation radius in the quasigeostrophic model being set using the stratification from the primitive equation model. Over a fairly broad parameter range, the primitive equation and quasigeostrophic results are in qualitative and, to some degree, quantitative agreement and are consistent with the phenomenology of geostrophic turbulence. The scale, amplitude, and baroclinicity of the eddies and the degree of baroclinic instability of the mean flow all vary fairly smoothly with the imposed parameters; both models are able, in some parameter ranges, to produce supercritical flows. The criticality in the primitive equation model, which does not have any convective parameterization scheme, is fairly sensitive to the external parameters, most notably the planet size (i.e., the f/β ratio), the forcing time scale, and the factors influencing the stratification. In some parameter settings of the models, although not those that are most realistic for the earth's atmosphere, it is possible to produce eddies that are considerably larger than the deformation scales and an inverse cascade in the barotropic flow with a -25/3 spectrum. The vertical flux of heat is found to be related to the isentropic slope. © 2009 American Meteorological Society."
"8849029800;57034458200;","An analytical model for the rapid intensification of tropical cyclones",2009,"10.1002/qj.433","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70149085827&doi=10.1002%2fqj.433&partnerID=40&md5=d5ac6ca1850d9b054c695be20bbd9580","The nonlinearity and complexity of the primitive equations have been key obstacles to our understanding of tropical cyclones (TCs), particularly in relation to the dynamical processes leading to their rapid intensification. In this study, an axisymmetric model, in which all nonlinear terms in the horizontal momentum equations are retained, is used to examine analytically the effects of organized deep convection on TC rapid intensification. By prescribing a vertical profile of the vertical motion with exponential growth in the core region, a class of exact time-dependent solutions for the primary circulations of TCs are obtained. The analytical solutions are shown to capture well many observed dynamical structures in both the core and outer regions and the rapid growth of TCs in terms of maximum winds and central pressure drops. The analytical solutions reveal that (1) the rotational flows in the inner-core region grow double-exponentially, and the central pressure drops occur at rates much faster than the rotational growth; (2) the amplification rates of the primary circulations differ profoundly from those of the secondary circulations; (3) the rotational flows tend to grow from the bottom upwards with the fastest growth occurring at the lowest levels; and (4) the TC growth rates depend critically on the vertical structure of tangential flows, with a faster rate for a lower-level peak rotation. The nonlinear dynamics are shown to play an important role in the rapid growth of TCs. It is demonstrated that the analytical solutions can also be used to construct dynamically consistent vortices for the initialization of TC models. Limitations and possible improvements of the analytical model are also discussed. © 2009 Royal Meteorological Society."
"7202619752;7404970050;","Baroclinic development within zonally-varying flows",2007,"10.1002/qj.87","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548236997&doi=10.1002%2fqj.87&partnerID=40&md5=9c15c48a16cccf3be12082ea05020a1f","Previous idealized-modelling studies have shown the importance of across-jet barotropic shear to the resulting evolution of cyclones, anticyclones, surface-based fronts, and upper-level fronts. Meanwhile, many observational studies of cyclones have shown the importance of along-jet variations in the horizontal wind speed (i.e. confluence and diffluence). This study investigates the importance of these along-jet (zonal, for zonally-oriented jets) variations in the horizontal wind speed to the resulting structures and evolutions of baroclinic waves, using idealized models of growing baroclinic waves. An idealized primitive-equation channel model is configured with growing baroclinic perturbations embedded within confluent and diffluent background flows. When the baroclinic perturbations are placed in background confluence, the lower-tropospheric frontal structure and evolution initially resemble the Shapiro-Keyser cyclone model, with a zonally-oriented cyclone, strong warm front, and bent-back warm front. Later, as the baroclinic wave is amplified in the stronger downstream baroclinicity, the warm sector of the cyclone narrows, becoming more reminiscent of the Norwegian cyclone model. The upper-level frontal structure develops with a southwest-northeast orientation, and becomes strongest at the base of the trough, where geostrophic cold advection is occurring. In contrast, when the baroclinic perturbations are placed in background diffluence, the lower-tropospheric frontal structure and evolution resemble the Norwegian cyclone model, with a meridionally-oriented cyclone, strong cold front, and occluded front. The upper-level frontal structure is initially oriented northwest-southeast on the western side of the trough, before becoming zonally oriented. Weak geostrophic temperature advection occurs along its length. These results are compared to those from previous observational and idealized-modelling studies. Copyright © 2007 Royal Meteorological Society."
"6601956073;6603148881;24492486300;","Seasonal rainfall predictions over the southeast United States using the Florida State University nested regional spectral model",2007,"10.1029/2006JD007535","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34848890272&doi=10.1029%2f2006JD007535&partnerID=40&md5=bdff5af7a28a9dfe7e19f455f16610f5","Seasonal rainfall predictions over the southeast United States using the recently developed Florida State University (FSU) nested regional spectral model are presented. The regional model is nested within the PSU coupled model, which includes a version of the Max Plank Institute Hamburg Ocean Primitive Equation model. The southeast U.S. winter has a rather strong climatic signal due to teleconnections with tropical Pacific sea surface temperatures and thus provides a good test case scenario for a modeling study. Simulations were done for 12 boreal winter seasons, from 1986 to 1997. Both the regional and global models captured the basic large-scale patterns of precipitation reasonably well when compared to observed station data. The regional model was able to predict the anomaly pattern somewhat better than the global model. The regional model was particularly more skillful at predicting the frequency of significant rainfall events, in part because of the ability to produce heavier rainfall events. Copyright 2007 by the American Geophysical Union."
"56726831900;7101630970;6602250413;7202946344;","The counter-propagating Rossby-wave perspective on baroclinic instability. Part IV: Nonlinear life cycles",2005,"10.1256/qj.04.23","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27644539289&doi=10.1256%2fqj.04.23&partnerID=40&md5=d523e17e2d31efd9991ec783d506ecc0","Pairs of counter-propagating Rossby waves (CRWs) can be used to describe baroclinic instability in linearized primitive-equation dynamics, employing simple propagation and interaction mechanisms at only two locations in the meridional plane - the CRW 'home-bases'. Here, it is shown how some CRW properties are remarkably robust as a growing baroclinic wave develops nonlinearly. For example, the phase difference between upper-level and lower-level waves in potential-vorticity contours, defined initially at the home-bases of the CRWs, remains almost constant throughout baroclinic wave life cycles, despite the occurrence of frontogenesis and Rossby-wave breaking. As the lower wave saturates nonlinearly the whole baroclinic wave changes phase speed from that of the normal mode to that of the self-induced phase speed of the upper CRW. On zonal jets without surface meridional shear, this must always act to slow the baroclinic wave. The direction of wave breaking when a basic state has surface meridional shear can be anticipated because the displacement structures of CRWs tend to be coherent along surfaces of constant basic-state angular velocity, Ū. This results in up-gradient horizontal momentum fluxes for baroclinically growing disturbances. The momentum flux acts to shift the Jet meridionally in the direction of the increasing surface Ū, so that the upper CRW breaks in the same direction as occurred at low levels. © Royal Meteorological Society, 2005."
"7402478173;7102322882;6504719808;","Hadley circulations and Kelvin wave-driven equatorial jets in the atmospheres of Jupiter and Saturn",2005,"10.1016/j.pss.2004.03.009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-15844376696&doi=10.1016%2fj.pss.2004.03.009&partnerID=40&md5=90a970b719dd32795d33dc904b019016","We propose a dynamical mechanism that can plausibly explain the origin of the broad prograde equatorial winds observed on Jupiter and Saturn, and examine the feasibility of this mechanism using two- (2D) and three-dimensional (3D) numerical simulation models. The idea is based on combining a narrow Gaussian jet peaking at the equator, which is induced by the momentum transfer from an upward propagating equatorial Kelvin-wave, and a pair of off-equatorial jets due to a meridional-vertical circulation similar to the tropical Hadley circulation on Earth. We employ for this feasibility study a 2D mechanistic mean-flow model which incorporates the influence of prescribed waves, and a 3D general circulation model, based on the generalised primitive equations of atmospheric motion. We then confirm that the dynamical models of both kinds can successfully reproduce theoretically expected flows of a reasonable magnitude, and that when two mechanisms are combined, a broad super-rotating jet is produced with off-equatorial maxima in zonal velocity for both Jupiter and Saturn, approximately in accordance with observations. © 2005 Elsevier Ltd. All rights reserved."
"7003428365;7006452341;","Interdecadal variability in a hybrid coupled ocean-atmosphere-sea ice model",2004,"10.1175/1520-0485(2004)034<1756:IVIAHC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4043080627&doi=10.1175%2f1520-0485%282004%29034%3c1756%3aIVIAHC%3e2.0.CO%3b2&partnerID=40&md5=8d18d3e4458aac15f669bf3eb14df654","Interdecadal climate variability in an idealized coupled ocean-atmosphere-sea-ice model is studied. The ocean component is a fully three-dimensional primitive equation model and the atmospheric component is a two-dimensional (2D) energy balance model of Budyko-Sellers-North type, while sea ice is represented by a 2D thermodynamic model. In a wide range of parameters the model climatology resembles certain aspects of observed climate. Two types of interdecadal variability are found. The first one is characterized by northward-propagating upper-ocean temperature anomalies in the northwestern part of the ocean basin and a westward-propagating, wavelike temperature pattern at depth. The other type has larger-scale temperature anomalies that propagate westward in both the upper and deep ocean, along the sea ice edge. Both types of oscillations have been found previously in similar models that do not include sea ice. Therefore, the oscillation mechanism does not depend on sea-ice feedbacks nor is it modified very much by the inclusion of sea ice. For some parameter values, the interdecadal oscillations are self-sustained, while for others they are damped. Stochastic-forcing experiments show that, in the latter case, significant interdecadal signals can still be identified in the time series of oceanic heat transport. The periods of these signals, however, do not closely match those identified in a stability analysis of the deterministic model when linearized about its steady state. The authors show that linearization around the actual climatology of the stochastically forced integrations provides a better match for some of the modes that were poorly explained when linearizing about the deterministic model's steady state. The main difference between the two basic states is in the distribution of climatological convective depth, which is affected strongly by intermittent atmospheric forcing. © 2004 American Meteorological Society."
"35330117400;","On the nonhydrostatic atmospheric models with inclusion of the horizontal component of the earth's angular velocity",2003,"10.2151/jmsj.81.935","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642529761&doi=10.2151%2fjmsj.81.935&partnerID=40&md5=721b93d9b1287f856cf95d23d4fd1b7b","Two nonhydrostatic effects that have been neglected traditionally in the hydrostatic primitive-equation models are studied in this article. One such effect is due to the vertical acceleration in the vertical equation of motion. The other is due to a Coriolis term involving 2Ω cos (latitude), where Ω is the rate of earth's rotation, and is referred to here as a cos (latitude) Coriolis term. Cos (latitude Coriolis terms appear in the vertical and zonal equations of motion. The questions to be investigated are: (1) what are the dynamical consequences of these two nonhydrostatic effects, (2) how the roles of cos (latitude) Coriolis terms can be compared with sin (latitude) Coriolis terms, (3) which nonhydrostatic effect is likely more important, and (4) should these effects be included in atmospheric modeling for describing what kind of motions? These questions are studied quantitatively through a normal mode analysis of compressible, and stratified atmosphere with rotation on a tangent planes in a three-dimensional space that is open horizontally, but bounded by two rigid horizontal planes in the vertical. Numerical results are presented for an isothermal model. Considering the current trend of numerical modeling in permitting to use finer resolutions and to extend the top of model atmosphere higher, it is prudent to include both nonhydrostatic effects in the dynamical core of next generation atmospheric models for all scales of motions."
"7007019497;57205984002;6603168350;7005461772;","Modeling the baroclinic circulation in the area of the Sicily channel: The role of stratification and energy diagnostics",2003,"10.1029/2002jc001502","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141940670&doi=10.1029%2f2002jc001502&partnerID=40&md5=8a1611c3a0f3808465efcf48c5093e77","Aspects of the circulation of the Sicily channel region are studied with a high-resolution, primitive equation, sigma coordinate model. This work is an attempt to study the process governing the purely baroclinic dynamics and its sensitivity to seasonal stratification, thus no atmospheric forcing is used. Two numerical experiments are analyzed using, as initial conditions, diagnostic velocity fields derived from the winter and summer climatological hydrologies. The quasi-steady state is characterized by circulation patterns, in the depth range of the Modified Atlantic Water (MAW) and the Levantine Intermediate Water (LIW), strongly controlled by mesoscale eddies and topography. Seasonal difference is found in the surface current which exhibits the major variability on the African side, downstream of Adventure Bank and the Ionian Slope where the absolute maximum occurs. The intermediate circulation instead does not show relevant seasonal differences. LIW enters through the two passages south of Malta Plateau and preferentially flows along the Sicilian shelf edge exiting over the northern sill. Its pathway is strongly controlled by subsurface cyclonic and anticyclonic cells. The results are in good agreement with observations. An energy diagnostics is applied to model results and sheds important light on dynamical characteristics of the mesoscale eddy field and indicates seasonal differences in the energetic exchange with the mean flow. The analysis of the mean (MKE) and eddy (EKE) kinetic energy, the transfer terms between energy compartments and the eddy momentum flux divergence indicates how eddies are strongly energetic in summer and exchange energy more efficiently with the mean flow. In the quasi-steady state MAW volume transport and MKE and EKE fluctuations are strongly correlated. This result suggests that mesoscale motions can control up to 40% of volume transport variability."
"7409074131;7003601925;7007085057;","Study of block onset using sensitivity perturbations in climatological flows",1999,"10.1175/1520-0493(1999)127<0879:SOBOUS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032744115&doi=10.1175%2f1520-0493%281999%29127%3c0879%3aSOBOUS%3e2.0.CO%3b2&partnerID=40&md5=84bfd68c3c9ebd8230f71686f7ce5144","This work describes the dynamics of adjoint sensitivity perturbations that excite block onsets over the Pacific and Atlantic Oceans. Appropriate functions are derived for the blocking indices for these two regions and the model basic flow is constructed from Northern Hemisphere climatological data. The concepts of sensitivity analysis are extended to forced problems. This tool is used to investigate block onset due to atmospheric forcing, such as that resulting from tropical sea surface temperature anomalies. These linear studies are carried out in a hemispherical, primitive equations, θ-coordinate, two-layer model. Results show that wind sensitivity perturbations less than 10 m s-1 and sensitivity forcing of vorticity sources of the order of 1.5 x 10-10 s-2 are sufficient to excite block onset. Both for the Pacific and Atlantic blocking, sensitivity perturbations and forcing perturbations, when expressed in terms of vertical vorticity, display a Rossby wave train structure mainly found on the southward flanks of the Pacific and Atlantic jets, that is, near the Philippines and the Caribbean regions. From inferences based on the flow evolution of these sensitivity perturbations and with the help of potential vorticity analyses on the two constant potential temperature surfaces in this model, a dynamical framework that may explain Pacific and Atlantic block onsets is proposed. The nonuniform potential vorticity distribution in the jets, in particular the concentration of these gradients on potential vorticity waveguides, and the Lagrangian advection of potential vorticity by the eddies making up the stationary Rossby wave train and their energy propagation and convergence all conspire to play a key role in the growth of the synoptic-scale eddies supported by baroclinic as well as barotropic processes. It is proposed that the structural modification of the eddies in the wave train leads to the planetary structures that become associated with block onset. More specifically, the wave train in the Pacific evolves into a blocking dipole while the Atlantic block is found at the leading edge of the Rossby wave train across the Atlantic. Furthermore, this study shows that at the initial time the Pacific block displays a clear baroclinic structure while the wave train associated with the Atlantic block has a much more barotropic structure. The significance of these results and their potential applications to predictions of blocking are discussed.This work describes the dynamics of adjoint sensitivity perturbations that excite block onsets over the Pacific and Atlantic Oceans. Appropriate functions are derived for the blocking indices for these two regions and the model basic flow is constructed from Northern Hemisphere climatological data. The concepts of sensitivity analysis are extended to forced problems. This tool is used to investigate block onset due to atmospheric forcing, such as that resulting from tropical sea surface temperature anomalies. These linear studies are carried out in a hemispherical, primitive equations, θ-coordinate, two-layer model. Results show that wind sensitivity perturbations less than 10 m s-1 and sensitivity forcing of vorticity sources of the order of 1.5×10-10 s-2 are sufficient to excite block onset. Both for the Pacific and Atlantic blocking, sensitivity perturbations and forcing perturbations, when expressed in terms of vertical vorticity, display a Rossby wave train structure mainly found on the southward flanks of the Pacific and Atlantic jets, that is, near the Philippines and the Caribbean regions. From inferences based on the flow evolution of these sensitivity perturbations and with the help of potential vorticity analyses on the two constant potential temperature surfaces in this model, a dynamical framework that may explain Pacific and Atlantic block onsets is proposed. The nonuniform potential vorticity distribution in the jets, in particular the concentration of these gradients on potential vorticity waveguides, and the Lagrangian advection of potential vorticity by the eddies making up the stationary Rossby wave train and their energy propagation and convergence all conspire to play a key role in the growth of the synoptic-scale eddies supported by baroclinic as well as barotropic processes. It is proposed that the structural modification of the eddies in the wave train leads to the planetary structures that become associated with block onset. More specifically, the wave train in the Pacific evolves into a blocking dipole while the Atlantic block is found at the leading edge of the Rossby have train across the Atlantic. Furthermore, this study shows that at the initial time the Pacific block displays a clear baroclinic structure while the wave train associated with the Atlantic block has a much more barotropic structure. The significance of these results and their potential applications to predictions of blocking are discussed."
"7801561092;6701387222;7402899368;","A Coupled Biosphere-Atmosphere Climate Model Suitable for Studies of Climatic Change Due to Land Surface Alterations",1998,"10.1175/1520-0442(1998)011<1749:ACBACM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1542398197&doi=10.1175%2f1520-0442%281998%29011%3c1749%3aACBACM%3e2.0.CO%3b2&partnerID=40&md5=98a84db6e8fdfa34e1060bd1e1071931","A biosphere model based on BATS (Biosphere-Atmosphere Transfer Scheme) is coupled to a primitive equation global statistical-dynamical model in order to study the climatic impact due to land surface alterations. The fraction of the earth's surface covered by each vegetation type according to BATS is obtained for each latitude belt. In the control experiment, the mean annual zonally averaged climate is well simulated when compared with observations. Deforestation and desertification experiments are performed. In the deforestation experiment, the evergreen broadleaf tree in the Amazonian region is substituted by short grass; in the desertification experiment the semidesert, and the tall grass and deciduous shrubs are substituted by desert and semidesert in the African continent, respectively. The results show that in both the experiments there is a reduction in evapotranspiration and precipitation in the perturbed region and an increase in the soil surface temperature, the temperature of the foliage air layer, and the foliage temperature. Also, the latent heat flux decreased in the perturbed cases relative to the control case. To partially compensate for the decrease in latent heating, sensible heat flux increased in the perturbed cases compared with the control case. The changes in the deforestation case are greater in the latitude belt centered at 5°S, where in most part the Amazonian forest is situated. Otherwise, the changes in the desertification are greater in the latitude belt centered at 15°N. When there is also degradation of the African tropical forest (substitution of evergreen broadleaf trees by short grass), the greatest changes occur southward from that region (in the latitude belt centered at 5°N), and the magnitude of the changes are also increased. This shows the important role of the modification of tropical forest when there is degradation of the vegetation in the African region from 20°N to 0oo. The results regarding the changes in the temperature and in the energy fluxes are in agreement with those of earlier experiments carried out with sophisticated general circulation models, which shows the usefulness of this kind of simple model."
"7201847619;7004379782;","An analysis of the vertical structure equation for arbitrary thermal profiles",1989,"10.1002/qj.49711548508","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024799555&doi=10.1002%2fqj.49711548508&partnerID=40&md5=0393f878e0cc9655728e62b5a8b5f21e","The vertical structure equation is a singular Sturm‐Liouville problem whose eigenfunctions describe the vertical dependence of the normal modes of the primitive equations linearized about a given thermal profile. The eigenvalues give the equivalent depths of the modes. We study, for arbitrary thermal profiles, the spectrum of the vertical structure equation and the appropriateness of various upper boundary conditions. Our results depend critically upon whether or not the thermal profile is such that the basic state atmosphere is bounded. This is not surprising since, as we point out, the vertical structure equation is not meaningful at large heights because of the traditional shallowness approximations which are used to derive the primitive equations. The nature of the spectrum of a singular Sturm‐Liouville problem depends only on the behaviour of the coefficients of the differential equation near the singular boundary. Spectral results therefore have no physical significance for unbounded atmospheres. For all bounded atmospheres we show that the spectrum is totally discrete, regardless of details of the thermal profile. For the barotropic equivalent depth, which corresponds to the lowest eigenvalue, we obtain upper and lower bounds which depend only on the surface temperature and the atmosphere height. All eigenfunctions are bounded, but always have first derivatives which become unbounded near the top. We prove that the commonly invoked upper boundary condition that vertical velocity must vanish as pressure tends to zero, as well as a number of alternative conditions, are well posed. For unbounded atmospheres, on the other hand, we show that typically there is a continuous spectrum, that the boundary condition of vanishing vertical velocity is not well posed, and that the eigenfunctions. if any. are unbounded. Copyright © 1989 Royal Meteorological Society"
"57217275562;7402363038;","The Effect of the Hadley Circulation On the Meridional Propagation of Stationary Waves",1987,"10.1002/qj.49711347706","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023482570&doi=10.1002%2fqj.49711347706&partnerID=40&md5=a9d0adb94205dc1386788e6118d52fda","The effect on the meridional propagation of stationary planetary waves of the inclusion of the zonal mean Hadley circulation in linearized models of the atmosphere is examined. In a forced barotropic vorticity equation model a meridional wind in the basic state enables wave propagation through tropical easterlies in the direction of the wind. This is shown to be consistent with the WKB solution. In a multi‐level linearized steady primitive equation model with an idealized meridional circulation tropical forcing can still produce response through easterlies although propagation from one mid‐latitude to the other is much less than in the barotropic result. This is explained through WKB and wave‐tracing methods for a simplified three‐dimensional vorticity equation. the near non‐divergence of the unforced tropical motion permits a wave to travel largely within a layer of favourable winds. In a twelve‐level model using observed January and July zonal mean conditions the Hadley circulation changes the response to earth topographic forcing mainly in the subtropics. However, tropical heat forcing can now produce a large mid‐latitude response, in the winter hemisphere especially. the resulting subtropical jets suggest a mechanism for the maintenance of those observed over Australia during the northern monsoon season and adjacent to the anomalous forcing of the 1983 El Niño. Copyright © 1987 Royal Meteorological Society"
"7402765035;","A four-dimensional analysis exactly satisfying equations of motion.",1986,"10.1175/1520-0493(1986)114<0388:AFDAES>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022823711&doi=10.1175%2f1520-0493%281986%29114%3c0388%3aAFDAES%3e2.0.CO%3b2&partnerID=40&md5=4f67d1d7037d7603c494e16d7e155a38","This report describes some preliminary experiments which use highly simplified filtered and primitive equation models of an atmosphere with f-plane geometry. These simple models are used because of the substantial computational resources required by the minimization method. It is demonstrated that the method is stable in an assimilation cycle, is able to maintain an accurate estimate of the motion field from temperature observations alone and yields a small analysis error. Unfortunately, forecasts made from the four-dimensional analyses exhibit rapid error growth initially; as a result these forecasts are better than ordinary forecasts only for the first 24 h. Beyond 24 h both types of forecasts have the same skill. -Author"
"25654862800;6602678456;7004923518;55424730400;7003639093;","Use of FerryBox surface temperature and salinity measurements to improve model based state estimates for the German Bight",2011,"10.1016/j.jmarsys.2011.02.020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955054547&doi=10.1016%2fj.jmarsys.2011.02.020&partnerID=40&md5=c646d3cd751c2a2d0fa5b1c7ac565105","The potential of FerryBox sea surface temperature (SST) and salinity (SSS) measurements for the improvement of state estimates in the German Bight is investigated. The paper quests the hypothesis that the parallel analysis of remote sensing and FerryBox data, as well as data simulated by a numerical model, could increase the efficiency of using the information contained in the FerryBox data when producing state estimates. The analysis uses output from a 3-D primitive equation numerical model, up-to-date remote sensing products, and classical in-situ observations as complementary information. A Kalman filter approach is applied to extrapolate one-dimensional FerryBox data acquired along the ferry route from Cuxhaven to Immingham to larger two-dimensional areas. The method makes use of a priori information about the background statistics provided by a numerical model. Maps of extrapolation errors are presented. The impact of the special FerryBox sampling with a revisit time of typically 36. h is investigated based on synthetic data. In particular the aliasing problem associated with the M2 tidal signal is discussed. It is demonstrated that reasonable extrapolation errors can be achieved with a linear interpolation method in combination with a filter operation. Real FerryBox measurements acquired in 2007 are used for assimilation experiments with a 3-D primitive equation model. A standard optimal interpolation (OI) technique is applied for this purpose. The required background statistics are estimated from a free run performed with the model. It is demonstrated that an assimilation of FerryBox SST data leads to a qualitative improvement of the SST state estimates over large areas. Our analysis showed that the natural variability of SSS along the FerryBox track is small compared to the measurement errors and the errors resulting from the specific FerryBox sampling. The use of FerryBox SSS data in an assimilation system is therefore more demanding than the use of the respective SST data. Comparisons with independent observations demonstrate that the improvements in the SSS state estimates are more pronounced for synoptic and short time events. © 2011 Elsevier B.V."
"36154754400;15765007300;7005087624;13406399300;","A stability analysis of divergence damping on a latitude-longitude grid",2011,"10.1175/2011MWR3607.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053196623&doi=10.1175%2f2011MWR3607.1&partnerID=40&md5=8cf4baacbd9471ab2ea6b3a0e106b2a3","The dynamical core of an atmospheric general circulation model is engineered to satisfy a delicate balance between numerical stability, computational cost, and an accurate representation of the equations of motion. It generally contains either explicitly added or inherent numerical diffusion mechanisms to control the buildup of energy or enstrophy at the smallest scales. The diffusion fosters computational stability and is sometimes also viewed as a substitute for unresolved subgrid-scale processes. A particular form of explicitly added diffusion is horizontal divergence damping. In this paper a von Neumann stability analysis of horizontal divergence damping on a latitude-longitude grid is performed. Stability restrictions are derived for the damping coefficients of both second- and fourthorder divergence damping. The accuracy of the theoretical analysis is verified through the use of idealized dynamical core test cases that include the simulation of gravity waves and a baroclinic wave. The tests are applied to the finite-volume dynamical core of NCAR's Community Atmosphere Model version 5 (CAM5). Investigation of the amplification factor for the divergence damping mechanisms explains how small-scale meridional waves found in a baroclinic wave test case are not eliminated by the damping. © 2011 American Meteorological Society."
"6507253177;","The sensitivity of the isentropic slope in a primitive equation dry model",2008,"10.1175/2007JAS2284.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38849209090&doi=10.1175%2f2007JAS2284.1&partnerID=40&md5=3cb39525d067fd112dd9a6e6394782fc","This paper discusses the sensitivity of the isentropic slope in a primitive equation dry model forced with Newtonian cooling when the heating is varied. This is done in two different ways, changing either the radiative equilibrium baroclinicity or the diabatic time scale for the zonal-mean flow. When the radiative equilibrium baroclinicity is changed, the isentropic slope remains insensitive against changes in the forcing, in agreement with previous results. However, the isentropic slope steepens when the diabatic heating rate is accelerated for the zonal-mean flow. Changes in the ratio between the interior and the boundary diffusivities as the diabatic heating rate is varied appear to be responsible for the violation of the constant criticality constraint in this model. Theoretical arguments are used to relate the sensitivity of the isentropic slope to that of the isentropic mass flux, which also remains constant when the radiative-equilibrium baroclinicity is changed. The sensitivity of the isentropic mass flux on the heating depends on how the gross stability changes. Bulk stabilities calculated from isobaric averages and gross stabilities estimated from isentropic diagnostics are not necessarily equivalent because a significant part of the return flow occurs at potential temperatures colder than the mean surface temperature. © 2008 American Meteorological Society."
"7006735547;7004060399;","A very large, spontaneous stratospheric sudden warming in a simple AGCM: A prototype for the Southern Hemisphere warming of 2002?",2005,"10.1175/JAS-3314.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17044402519&doi=10.1175%2fJAS-3314.1&partnerID=40&md5=6b1c26e8e1b426f7c4695a5450ad01a2","An exceptionally strong stratospheric sudden warming (SSW) that spontaneously occurs in a very simple stratosphere-troposphere AGCM is discussed. The model is a dry, hydrostatic, primitive equation model without planetary stationary waves. Transient baroclinic wave-wave interaction in the troposphere thus provides the only source of upward-propagating wave activity into the stratosphere. The model's SSW is grossly similar to the Southern Hemisphere major SSW of 2002: it occurs after weaker warmings ""precondition"" the polar vortex for breaking, it involves a split of the polar vortex, and it has a downward-propagating signature. These similarities suggest that the Southern Hemisphere SSW of 2002 might itself have been caused by transient baroclinic wave-wave interaction. The simple model used for this study also provides some insight into how often such extreme events might occur. The frequency distribution of SSWs in the model has exponential, as opposed to Gaussian, tails. This suggests that very large amplitude SSWs, though rare, might occur with higher frequency than might be naively expected."
"55686667100;7201785152;","Dynamical prototype of the Arctic Oscillation as revealed by a neutral singular vector",2004,"10.1175/1520-0442(2004)017<2119:DPOTAO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3042787740&doi=10.1175%2f1520-0442%282004%29017%3c2119%3aDPOTAO%3e2.0.CO%3b2&partnerID=40&md5=03b0014b80f9bce20fc123ca46f51fdf","Origin of the Arctic Oscillation (AO) was explored from a dynamical perspective, using a primitive equation model linearized about the observed winter climatology. In order to obtain a leading low-frequency mode of the model atmosphere, singular vector analysis is performed on the linear dynamical operator. The singular mode (v vector) with the smallest singular value, referred to as the neutral mode, has a considerable similarity to the observed AO in many aspects, suggesting that, at least in a linear dynamical framework, the AO is a dynamically consistent mode of variability that arises from the zonal asymmetry of the time-mean state. Diagnosis of the neutral mode shows that a zonal flow-stationary wave interaction and an interaction between anomalous and climatological stationary waves are both of importance for maintenance of the spatial structure. Besides, vortex stretching-shrinking is significant in the upper levels, which indicates that a baroclinic process has a certain role as well. It is found that the formation of a hemispheric scale of the neutral mode is accomplished within several days via propagation of Rossby wave packets along jet streams that act as a waveguide. The neutral mode structure is robust for a wide range of model damping parameters, and especially preferred when the damping is weakened in the free troposphere. The corresponding optimal forcing (u vector) indicates that, though its robustness is relatively ambiguous, the neutral mode is most effectively excited by a certain pattern of the extratropical thermal forcing, in addition to a modest sensitivity to the deep heating anomaly over the tropical Indian Ocean. © 2004 American Meteorologicsl Society."
"55899460500;6701395093;","Primitive-equation-based low-order models with seasonal cycle. Part I: Model construction",2003,"10.1175/1520-0469(2003)060<0465:PEBLOM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042130519&doi=10.1175%2f1520-0469%282003%29060%3c0465%3aPEBLOM%3e2.0.CO%3b2&partnerID=40&md5=fd7f82d1c41b1424a9b16af9fba19382","In a continuation of previous investigations on deterministic reduced atmosphere models with compact state space representation, two main modifications are introduced. First, primitive equation dynamics is used to describe the nonlinear interactions between resolved scales. Second, the seasonal cycle in its main aspects is incorporated. Stability considerations lead to a gridpoint formulation of the basic equations in the dynamical core. A total energy metric consistent with the equations can be derived, provided surface pressure is treated as constant in time. Using this metric, a reduction in the number of degrees of freedom is achieved by a projection onto three-dimensional empirical orthogonal functions (EOFs). each of them encompassing simultaneously all prognostic variables (winds and temperature). The impact of unresolved scales and not explicitly described physical processes is incorporated via an empirical linear parameterization. The basis patterns having been determined from 3 sigma levels from a GCM dataset, it is found that, in spite of the presence of a seasonal cycle, at most 500 are needed for describing 90% of the variance produced by the GCM. If compared to previous low-order models with quasigeostrophic dynamics, the reduced models exhibit at this and lower-order truncations, a considerably enhanced capability to predict GCM tendencies. An analysis of the dynamical impact of the empirical parameterization is given, hinting at an important role in controlling the seasonally dependent storm track dynamics."
"6602578797;7003749832;7003312252;","Simulation and analysis of the mesoscale circulation in the northwestern Mediterranean Sea",2003,"10.5194/angeo-21-281-2003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037779433&doi=10.5194%2fangeo-21-281-2003&partnerID=40&md5=12d803b409d6e50d844a62e6559829be","The large-scale and mesoscale circulation of the northwestern Mediterranean Sea are simulated with an eddy-resolving primitive-equation regional model (RM) of 1/16° resolution embedded in a general circulation model (GM) of the Mediterranean Sea of 1/8° resolution. The RM is forced by a monthly climatology of heat fluxes, precipitation and wind stress. The GM, which uses the same atmospheric forcing, provides initial and boundary conditions for the RM. Analysis of the RM results shows that several realistic features of the large-scale and mesoscale circulation are evident in this region. The mean cyclonic circulation is in good agreement with observations. Mesoscale variability is intense along the coasts of Sardinia and Corsica, in the Gulf of Lions and in the Catalan Sea. The length scales of the Northern Current meanders along the Provence coast and in the Gulf of Lions' shelf are in good agreement with observations. Winter Intermediate Water is formed along most of the north-coast shelves, between the Gulf of Genoa and Cape Creus. Advection of this water by the mean cyclonic circulation generates a complex eddy field in the Catalan Sea. Intense anticyclonic eddies are generated northeast of the Balearic Islands. These results are in good agreement with mesoscale activity inferred from satellite altimetric data. This work demonstrates the feasibility of a downscaling system composed of a general-circulation, a regional and a coastal model, which is one of the goals of the Mediterranean Forecasting System Pilot Project."
"56160100900;7004471232;6701831809;35514012200;8884425800;","Assimilation of TQPEX/Poseidon altimetric data in a primitive equation model of the tropical Pacific Ocean during the 1992-1996 El Niño-Southern Oscillation period",2000,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033670781&partnerID=40&md5=77cbe9df5e2bfc886015e66066995be7","Four years of TOPEX/Poseidon data (October 1992 to October 1996) are assimilated into a high-resolution primitive equation model [Gent and Cane, 1989] of the tropical Pacific Ocean. The assimilation method used is a degraded version of the Singular Evolutive Extended Kalman filter approach [Pham et al., 1998] in which the reduced order basis is fixed. The along-track TOPEX/Poseidon sea surface height residuals are introduced in the model every 3 days. Initialization of the model runs appears to be crucial. This is particularly true for the 1992-1996 period, which is characterized by several El Niño and La Niña events and exhibits quite anomalous climatological behavior. An in situ database dedicated to this period was built and used to initialize the model properly. The simulation results with and without assimilation were compared with expendable bathythermograph and Tropical Atmosphere-Ocean in situ observations. The impact of sea surface height assimilation is observed both on the surface and subsurface temperature and velocity fields. The deficiencies of the free model in terms of means and variability structures are significantly reduced. More importantly, the evolution of the model fields over time is considerably improved by the assimilation. These supposedly more realistic assimilated four-dimensional fields are used to investigate the mechanism responsible tor the 1992-1996 warm pool replenishment and depletion. This approach provides insights into the combined role of zonal and meridional transports in balancing volume changes in the warm pool. Copyright 2000 by the American Geophysical Union."
"7004274115;","The dynamical balance of leading singular vectors in a primitive-equation model",2000,"10.1256/smsqj.56603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033863746&doi=10.1256%2fsmsqj.56603&partnerID=40&md5=0e43d3a1272363e34f13739bd767a9b4","The dynamical balance of singular vectors (SVs) determined with respect to an energy norm for a primitive-equation atmospheric model is investigated. Partitioning between balanced and unbalanced components is primarily performed in terms of geostrophic and ageostrophic normal modes. Results indicate that if linearized effects of moist convection are not considered, the initial structure of the leading (most rapidly growing) SV is primarily geostrophic, although the ageostrophic part is significant. At the concluding time, however, the structure is almost totally geostrophic. The initially uncorrelated geostrophic and ageostrophic portions of the SV separately evolve into highly correlated structures. These two separately evolved portions therefore reinforce each other, so that the sum of the concluding total perturbation energies of the two portions is less than the corresponding energy of the non-partitioned SV. The high correlations also suggest that the inverse of the tangent linear model would be ill-suited for estimating an initial perturbation given an imperfectly known final one. There is no hint of significant high-frequency inertial gravity-wave activity."
"6603447004;7201554561;56033135100;7103413199;","The importance of moisture distribution for the growth and energetics of mid-latitude systems",1999,"10.1007/s00585-999-0242-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033477026&doi=10.1007%2fs00585-999-0242-y&partnerID=40&md5=96f98fffafd6ab6d9177d9a7614467eb","A primitive equation model is used to study the sensitivity of baroclinic wave life cycles to the initial latitude-height distribution of humidity. Diabatic heating is parametrized only as a consequence of condensation in regions of large-scale ascent. Experiments are performed in which the initial relative humidity is a simple function of model level, and in some cases latitude bands are specified which are initially relatively dry. It is found that the presence of moisture can either increase or decrease the peak eddy kinetic energy of the developing wave, depending on the initial moisture distribution. A relative abundance of moisture at mid-latitudes tends to weaken the wave, while a relative abundance at low latitudes tends to strengthen it. This sensitivity exists because competing processes are at work. These processes are described in terms of energy box diagnostics. The most realistic case lies on the cusp of this sensitivity. Further physical parametrizations are then added, including surface fluxes and upright moist convection. These have the effect of increasing wave amplitude, but the sensitivity to initial conditions of relative humidity remains. Finally, 'control' and 'doubled CO2' life cycles are performed, with initial conditions taken from the time-mean zonal-mean output of equilibrium GCM experiments. The attenuation of the wave resulting from reduced baroclinicity is more pronounced than any effect due to changes in initial moisture."
"7003968166;57195139224;7005131869;","Upstream development in idealized baroclinic wave experiments",1999,"10.3402/tellusa.v51i5.14476","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033393352&doi=10.3402%2ftellusa.v51i5.14476&partnerID=40&md5=de862fa9b180ec3c35ff714f44064720","An idealized dry primitive equation model on the f-plane is used to study upstream (and downstream) baroclinic wave development. The simulations are initiated with localized finite amplitude and vertically evanescent perturbations, specified either as upper-level potential vorticity or surface potential temperature anomalies. The nonlinear evolution of these nonmodal perturbations leads to the generation of large-scale upper-level induced primary and downstream surface cyclones, and distinctively smaller, shallow and more slowly intensifying upstream systems. It is shown that in particular the genesis and evolution of upstream cyclones is highly sensitive to the scale of the initial perturbation. Narrow upper-level troughs (or zonally confined surface temperature anomalies) are favorable for upstream development, whereas no or only weak upstream activity occurs with broad planetary-scale troughs (or zonally extended surface temperature anomalies) as initial perturbations. It is proposed that this sensitivity property of upstream development is qualitatively related to the dispersion characteristics of surface edge waves. The shortcomings of the present approach are discussed, and some consideration is given to the occurrence of upstream cyclogenesis in the real atmosphere, to the relationship with earlier concepts of secondary cyclogenesis, and to possible implications for the issue of predictability of extratropical weather systems."
"7102046393;25953950400;","Balanced and unbalanced circulations in a primitive equation simulation of a midlatitude MCC. Part I: The numerical simulation",1997,"10.1175/1520-0469(1997)054<0457:BAUCIA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031469423&doi=10.1175%2f1520-0469%281997%29054%3c0457%3aBAUCIA%3e2.0.CO%3b2&partnerID=40&md5=73c14ffbed4f2d922682dfdbd62f6193","A midlatitude mesoscale convective complex (MCC), which occurred over the central United States on 23-24 June 1985, was simulated using the Regional Atmospheric Modeling System (RAMS). The multiply nestedgrid simulation agreed reasonably well with surface, upper-air, and satellite observations and ground-based radar plots. The simulated MCC had a typical structure consisting of a leading line of vigorous convection and a trailing region of less intense stratiform rainfall. Several other characteristic MCC circulations were also simulated: a divergent cold pool in the lower troposphere, midlevel convergence coupled with a relatively cool descending rear-inflow jet, and relatively warm updraft structure, and a cold divergent anticyclone in the tropopause region. Early in the MCC simulation, a mesoscale convectively induced vortex (MCV) formed on the eastern edge of the convective line. While frequently associated with MCCs and other mesoscale convective systems (MCSs), MCVs are more typically reported in the mature and decaying stages of the life cycle. Several hours later, a second MCV formed near the opposite end of the convective line, and by the mature phase of the MCC, these MCVs were embedded within a more complex system-wide vortical flow in the lower troposphere. Analysis of the first MCV during its incipient phase indicates that the vortex initially formed near the surface by convergence/stretching of the large low-level ambient vertical vorticity in this region. Vertical advection appeared largely responsible for the upward extension of this MCV to about 3.5 km above the surface, with tilting of horizontal vorticity playing a secondary role. This mechanism of MCV formation is in contrast to recent idealized high-resolution squall line simulations, where MCVs were found to result from the tilting into the vertical of storm-induced horizontal vorticity formed near the top of the cold pool. Another interesting aspect of the simulation was the development of a banded vorticity structure at midtropospheric levels. These bands were found to be due to the apparent vertical transport of zonal momentum by the descending rear-to-front circulation, or rear-inflow jet. An equivalent alternative viewpoint of this process, deformation of horizontal vorticity filaments by the convective updrafts and rear-inflow jet, is discussed. Part II of this work presents a complementary approach to the analysis presented here, demonstrating that the circulations seen in this MCC simulation are, to a large degree, contained within the nonlinear balance approximation, the related balanced omega equation, and the PV as analyzed from the PE model results."
"7404247296;","A note on the relation between the “traditional approximation” and the metric of the primitive equations",1989,"10.1111/j.1600-0870.1989.tb00374.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981588444&doi=10.1111%2fj.1600-0870.1989.tb00374.x&partnerID=40&md5=9d651f9a92ca0242e79b80284494d8ab","The so‐called “traditional approximation” consists in the neglect of certain terms in the equations of motion, in particular the horizontal Coriolis components. The validity of this approximation has long been discussed in the literature. In this study, it is shown that it is possible to exploit the shallowness of the atmosphere for a simplification of the spherical metric of the considered system (“Metrische Vereinfachung”). A Lagrange equation with this simplified metric may then be used to derive the equations of motion. These equations will not contain the problematic terms neglected in the “traditional approximation”. Using this procedure, it is possible to include a simple friction model through a dissipation function. 1989 Blackwell Munksgaard"
"6506788908;","The dynamics of the Western Mediterranean Sea: a wind forced case study.",1987,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023477685&partnerID=40&md5=92e6dbab67b05554824b4260d462b7b5","Numerical model simulations are used to examine the effects of wind forcing on the dynamics of the upper-layer circulation within the Western Mediterranean Sea. A one-layer, reduced-gravity, primitive equations model on a beta-plane is used to perform the numerical simulations. The model is forced by both monthly mean climatological winds and monthly mean surface winds from the Fleet Numerical Oceanography Center's regional atmospheric forecast model for the Mediterranean Sea, the Naval Operational Regional Atmospheric Prediction System (NORAPS). The simulation results show that wind forcing and the variability in the wind forcing can significantly affect the circulation dynamics of the Western Mediterranean Sea. -Author"
"57192158845;14519102400;7004069241;","Stability of vertical discretization schemes for semi-implicit primitive equation models: theory and application.",1983,"10.1175/1520-0493(1983)111<1189:SOVDSF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020860139&doi=10.1175%2f1520-0493%281983%29111%3c1189%3aSOVDSF%3e2.0.CO%3b2&partnerID=40&md5=ae663f745f1cda27a878e6f3bcaf27e2","The equations are linearized about a stationary rotating basic state atmosphere that has a vertically shearing zonal wind. The amplification matrix of the finite-element model is constructed and its eigenvalues examined for possible instability. Investigating the small time step limit of that matrix, we identify two operators whose eigenvectors are the 'physical' and 'computational' modes of the semi-implicit method, respectively, and whose eigenvalues are their frequencies.-from Authors"
"7006434077;7404578173;24513973500;7402835457;","Characteristics of air pollution in the presence of land and sea breeze-A numerical simulation",1983,"10.1016/0004-6981(83)90005-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020553678&doi=10.1016%2f0004-6981%2883%2990005-7&partnerID=40&md5=e094ab7c66ee1ad63a5678933fd70590","Characteristics of air pollution in the coastal region in the presence of the land and sea breeze were investigated numerically. First, two-dimensional primitive equations of momentum and heat were integrated to simulate the wind field of the land and sea breeze. Then, the motion of pollutant emitted into the land and sea breeze circulation, after its diurnal variation became completely cyclic, were traced for three days. Three cases with constant emission rate from line sources which are located aloft on the shoreline and on the sea surface, respectively, and from the surface source along the shore were examined. Characteristics of the diurnal pattern, including the apparent ""background concentration"" on the shore, as well as the daily variation of the pollutant concentration were discussed. From the analysis of long-period trajectories of neutrally-buoyant particles, general macroscopic motions of the pollutant were revealed. © 1983."
"7006060300;","Synoptic‐scale forcing of coastal lows: Forced double kelvin waves in the atmosphere",1981,"10.1002/qj.49710745204","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019655550&doi=10.1002%2fqj.49710745204&partnerID=40&md5=9d8c71d3b81cb8270085cf5e0a493bfb","Gill (1977) has interpreted the coastal lows of southern Africa as atmospheric coastal Kelvin waves. the lows are trapped horizontally next to the steep slopes of the Great Central Plateau by Coriolis forces and vertically by a low‐level inversion. This hypothesis is tested and extended using two linear models. A barotropic primitive‐equation analysis on an equatorial beta‐plane models the generation of these waves. an impermeable eastern boundary is included to reflect the blocking of the low‐level flow below the coastal inversion by the orography. Results of the linear analysis suggest that the formation of the coastal lows may be explained in terms of the scattering of eastward‐propagating synoptic‐scale disturbances at the meridional boundary. the boundary response is structurally similar to a Kelvin wave. At the frequencies of interest, no zonally propagating Rossby waves are excited. Further, in contrast to the case of a western boundary, the equatorial response is negligible. A two‐layer, f‐plane model enables the dynamics of the layer of fluid below the interior inversion to be incorporated. At the period of the synoptic forcing (six days), the boundary response is a maximum along the escarpment and decays exponentially from it. the e‐folding distance is slightly less than the appropriate Rossby radius of deformation. These results, together with observations, suggest that the coastal low and its companion low over the interior may be interpreted as forced internal double Kelvin waves. The possible application of these results to foehn (chinook) winds and lee cyclogenesis is mentioned. Copyright © 1981 Royal Meteorological Society"
"55622148300;7005720566;","Extratropical response to the MJO: Nonlinearity and sensitivity to the initial state",2018,"10.1175/JAS-D-17-0189.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040929328&doi=10.1175%2fJAS-D-17-0189.1&partnerID=40&md5=d50700857f64dbb738f5cbaa95f39d4b","Previous studies have shown that the Madden-Julian oscillation (MJO) has a global impact that may provide an important source of skill for subseasonal predictions. The extratropical response was found to be the strongest when the tropical diabatic heating has a dipole structure with convection anomaly centers of opposite sign in the eastern Indian Ocean and the western Pacific. A positive (negative) MJO dipole heating refers to that with heating (cooling) in the eastern Indian Ocean and cooling (heating) in the western Pacific. In this study, two aspects of the extratropical response to the MJO are examined: 1) nonlinearity, which answers the question of whether the response to a positive MJO dipole heating is the mirror image of that to a negative MJO, and 2) sensitivity to the initial state, which explores the dependence of the extratropical response on the initial condition of the westerly jet. Ensemble integrations using a primitive-equation global atmospheric circulation model are performed with anomalous tropical thermal forcings that resemble a positive MJO (+MJO) and a negative MJO (-MJO). The response in the first week is largely linear. After that, significant asymmetry is found between the response in the positive MJO and the negative MJO. The 500-hPa negative geopotential height response in the North Pacific of the -MJO run is located about 30° east of the positive height response of the +MJO run. There is also an eastward shift of the extratropical wave train in the Pacific-North American region. This simulated nonlinearity is in agreement with the observations. The two leading response patterns among the ensemble members are identified by an empirical orthogonal function (EOF) analysis. EOF1 represents an eastward shift of the wave train, which is positively correlated with strengthening of the East Asian subtropical upper-troposphere westerly jet in the initial condition. On the other hand, EOF2 represents an amplification of the response, which is associated with a southward shift of the westerly jet in the initial state. © 2018 American Meteorological Society."
"51360903200;55622148300;","Tropical atmospheric forcing of the wintertime North Atlantic Oscillation",2016,"10.1175/JCLI-D-15-0583.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84960876715&doi=10.1175%2fJCLI-D-15-0583.1&partnerID=40&md5=45b80a961bbf115c43d6249e5ce0be55","The relationship between the interannual wintertime variability of the North Atlantic Oscillation (NAO) and tropical heating anomalies is examined using the NCEP-NCAR reanalysis and observation-based sea surface temperature (SST) and precipitation data for the period from 1980 to 2011. The NAO is found to be significantly correlated with the precipitation anomalies in the tropical Indian Ocean and tropical American-Atlantic region, but not with the underlying SST anomalies. The tropical heating impact on the NAO is examined and the evolution process of the influence is explored by numerical experiments using a primitive equation atmospheric model forced by atmospheric heating perturbations. Results from the reanalysis data and numerical experiments suggest that the atmospheric heating in the tropical Indian Ocean appears to be a driving force for the NAO variability. The atmospheric response to the tropical heating involves the combined effects of Rossby wave dispersion, normal mode instability, and transient eddy feedback. The remote forcing influence on the NAO tends to be organized and achieved by the circumglobal teleconnection pattern. By contrast, the influence of the tropical American-Atlantic heating on the NAO is weak. The linkage between the NAO and the tropical American-Atlantic heating is likely through the anomalously meridional atmospheric circulation over the Atlantic Ocean. © 2016 American Meteorological Society."
"55816797600;7003991093;55260519600;","Spontaneous superrotation and the role of kelvin waves in an idealized dry GCM",2014,"10.1175/JAS-D-13-0150.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893851217&doi=10.1175%2fJAS-D-13-0150.1&partnerID=40&md5=61e3814145bd164255e94a052113ea1d","The nondimensional parameter space of an idealized dry primitive equation model is explored to find superrotating climate states. The model has no convective parameterization and is forced using a simple thermal relaxation to a prescribed radiative equilibrium temperature. It is demonstrated that, of four nondimensional parameters that determine the model's state, only the thermal Rossby number has a significant effect on superrotation. The mode that drives the transition to superrotation in an intermediate-thermal-Rossby-number atmosphere is shown to behave like a Kelvin wave in the tropics. © 2014 American Meteorological Society."
"15056344900;23768134300;7402721790;7201709645;","A multimoment constrained finite-volume model for nonhydrostatic atmospheric dynamics",2013,"10.1175/MWR-D-12-00144.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878196511&doi=10.1175%2fMWR-D-12-00144.1&partnerID=40&md5=ba72f59c35faed23d10efdac2c849994","The two-dimensional nonhydrostatic compressible dynamical core for the atmosphere has been developed by using a new nodal-type high-order conservative method, the so-called multimoment constrained finitevolume (MCV) method. Different from the conventional finite-volume method, the predicted variables (unknowns) in an MCV scheme are the values at the solution points distributed within each mesh cell. The time evolution equations to update the unknown point values are derived from a set of constraint conditions based on themultimoment concept, where the constraint on the volume-integrated average (VIA) for eachmesh cell is cast into a flux form and thus guarantees rigorously the numerical conservation. Two important features make the MCV method particularly attractive as an accurate and practical numerical framework for atmospheric and oceanicmodeling. 1) The predicted variables are the nodal values at the solution points that can be flexibly located within a mesh cell (equidistant solution points are used in the present model). It is computationally efficient and provides great convenience in dealing with complex geometry and source terms. 2) High-order and physically consistent formulations can be built by choosing proper constraints in view of not only numerical accuracy and efficiency but also underlying physics. In this paper the authors present a dynamical core that uses the third- and the fourth-order MCV schemes. They have verified the numerical outputs of both schemes by widely used standard benchmark tests and obtained competitive results. The present numerical core provides a promising and practical framework for further development of nonhydrostatic compressible atmospheric models. © 2013 American Meteorological Society."
"9333569900;7006550959;6701313416;","Response of idealized baroclinic wave life cycles to stratospheric flow conditions",2009,"10.1175/2009JAS2827.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649454108&doi=10.1175%2f2009JAS2827.1&partnerID=40&md5=d3c771b015b1d1f385ae49a9fc0687ef","Dynamical stratosphere - troposphere coupling through a response of baroclinic waves to lower stratospheric flow conditions is investigated from an initial value approach. A series of adiabatic and frictionless nonlinear baroclinic wave life cycles in a midlatitude tropospheric jet with different initial zonal flow conditions in the stratosphere is simulated, using a dry primitive equation model with spherical geometry. When a stratospheric jet, located at various latitudes between 35° and 70°, is removed from the initial conditions, the wavenumber-6 life cycle behavior changes from the well-known LC1 to LC2 evolution, characterized by anticyclonic and cyclonic wave breaking, respectively. Linear theory, in terms of refractive index and the structure of the corresponding fastest-growing normal mode, is found to be unable to explain this stratosphere-induced LC1 to LC2 transition. This implies that altered nonlinear wave - mean flow interactions are important. The most significant stratosphere-induced change that extends into the nonlinear baroclinic growth stage is a region of downward wave propagation in the lower stratosphere associated with positive values of the squared refractive index near 20 km. Furthermore, it is demonstrated that the difference between the response of the tropospheric circulation to LC1 and LC2 life cycles closely resembles the meridional and vertical structure of the North Atlantic Oscillation (NAO), with positive (negative) NAO-like anomalies being driven by LC1 (LC2). Thus, a weakened stratospheric jet induces the generation of negative NAO-like anomalies in the troposphere, consistent with the observed stratosphere - NAO connection. © 2009 American Meteorological Society."
"22833710700;8948405600;6507467563;","Interannual and decadal variations in cross-shelf transport in the Gulf of Alaska",2009,"10.1175/2008JPO4014.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67649920797&doi=10.1175%2f2008JPO4014.1&partnerID=40&md5=2a355d17f5c701e08e54cfafa76b38b0","The marine ecosystem of the Gulf of Alaska (GOA) is one of the richest on the planet. The center of the GOA is characterized by high-nutrient and low-chlorophyll-a concentration. Recent observational studies suggest that advection of iron-rich coastal water is the primary mechanism controlling open ocean productivity. Specifically, there is evidence that mesoscale eddies along the coastal GOA entrain iron-rich coastal waters into the ocean interior. This study investigates the cross-shelf transport statistics in the GOA using a free-surface, hydrostatic, eddy-resolving primitive equation model over the period 1965-2004. The statistics of coastal water transport are computed using a model passive tracer, which is continuously released at the coast. The passive tracer can thus be considered a proxy for coastal biogeochemical quantities such as silicate, nitrate, iron, or oxygen, which are critical for explaining the GOAecosystem dynamics. On average along the Alaska Current, it has been shown that at the surface while the advection of tracers by the average flow is directed toward the coast consistent with the dominant downwelling regime of the GOA, it is the mean eddy fluxes that contribute to offshore advection into the gyre interior. South of the Alaskan Peninsula, both the advection of tracers by the average flow and the mean eddy fluxes contribute to the mean offshore advection. On interannual and longer time scales, the offshore transport of the passive tracer in the Alaskan Stream does not correlate with large-scale atmospheric forcing, nor with local winds. In contrast in the Alaska Current region, stronger offshore transport of the passive tracer coincides with periods of stronger downwelling (in particular during positive phases of the Pacific decadal oscillation), which trigger the development of stronger eddies. © 2009 American Meteorological Society."
"26532085500;7402826517;","Downward influence of stratospheric final warming events in an idealized model",2009,"10.1029/2008GL036624","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65249184492&doi=10.1029%2f2008GL036624&partnerID=40&md5=76032afee412e38e94824520b5ab5ce7","The stratospheric final warming is the final transition of the zonal winds from wintertime westerlies to summertime easterlies as solar heating of the high latitude stratosphere increases. Here the stratospheric influence on the tropospheric circulation during the stratospheric final warming events is investigated through ensemble model integrations of a simple dynamical core general circulation model. When the radiative equilibrium temperature in the stratosphere alone is gradually changed from a winter to a summer profile, the model generates realistic final warmings. As in the observations, the simulated final warmings occur at different ""dates"" in different realizations. Following previously published analyses of observed final warmings, we form a climatological springtime transition and compute composite anomalies centered on the final warmings. Simulations for both non-topographic and topographic cases show that starting five days before the final warming, the stratospheric zonal wind rapidly decelerates, in association with a strong upward Eliassen-Palm (EP) flux anomaly and EP flux convergence. Precursor events of wave driven zonal-wind deceleration occur, but at different times in simulations with and without topography. The composite zonal wind anomalies for final warmings with and without topography are compared with each other and with observations. In both cases, a statistically significant zonal wind anomaly extends downward to the surface, similarly to what is observed in the Northern Hemisphere (NH). These tropospheric zonal wind anomalies are stronger in the simulations with topography. Tropospheric geopotential height anomalies across the final warming also resemble NH observations. Copyright 2009 by the American Geophysical Union."
"24349915500;7004611313;7406423941;7003449105;6701865306;57212798589;6603833747;","A nested grid model of the Oregon Coastal Transition Zone: Simulations and comparisons with observations during the 2001 upwelling season",2009,"10.1029/2008JC004863","https://www.scopus.com/inward/record.uri?eid=2-s2.0-66149170111&doi=10.1029%2f2008JC004863&partnerID=40&md5=e234afc270d03fcc0287ff35898b7c63","The Oregon Coastal Transition Zone (OCTZ) extends several hundred kilometers offshore where shelf flows interact with the northern California Current. A primitive-equation numerical ocean model is used to study the upwelling circulation in this region from 1 May to 1 November 2001. This OCTZ model obtains initial and boundary conditions from a larger-scale model of the California Current System and forcing from a regional atmospheric model product. The model results are compared with extensive in situ and remotely sensed data, and the model is found to provide a realistic representation of flows both over the shelf and in the broader OCTZ. Simulation of coastal sea level and shelf currents over the complex topography of the central Oregon coast is improved quantitatively relative to previous regional models. A particularly significant qualitative improvement is realistic representation of coastal jet separation and eddy formation offshore of Cape Blanco. Three-dimensional Lagrangian analysis of water parcel displacement shows that the surface waters inshore of the separated jet are upwelled from near the bottom along the shelf as far north as 45.5°N. A large eddy, which incorporates some of this upwelled water and carries it farther westward, forms offshore in the late summer. Ensemble simulations show a distinction between the strongly deterministic response to wind forcing over the shelf and the more unstable, less predictable jet separation and offshore eddy formation processes in the region near Cape Blanco. © 2009."
"6701335949;","A linear analysis of the NCAR CCSM finite-volume dynamical core",2008,"10.1175/2007MWR2217.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-49749099288&doi=10.1175%2f2007MWR2217.1&partnerID=40&md5=74d911d543add138cf9f6c6a826650c8","The NCAR Community Climate System Model (CCSM) finite-volume atmospheric core uses a C-D-grid discretization to solve the equations of motion. A linear analysis of this discretization shows that it behaves as a D grid to leading order, it possesses the poor response of the D grid for short-wavelength divergent modes, the poor response of the C and D grids for short-wavelength rotational modes, and is only first-order accurate in time and damping. The scheme combines a modified forward-backward time integration for gravity waves with forward-in-time upwind-biased advection schemes, and the solver uses a vector-invariant form of the momentum equations. Other approaches using these equations are considered that circumvent some of the problems inherent in the current approach. © 2008 American Meteorological Society."
"7101734050;7003601925;6602761067;","An analaysis of west African dynamics using a linearized GCM",2008,"10.1175/2007JAS2194.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-45849134177&doi=10.1175%2f2007JAS2194.1&partnerID=40&md5=a08330c44694c070db664d54a12a9768","This study utilizes a linear, primitive equation spherical model to study the development and propagation of easterly wave disturbances over West Africa. Perturbations are started from an initial disturbance consisting of a barotropic vortex and the governing equations are integrated forward in time. The perturbations are introduced into basic states corresponding to the observed dynamical and thermodynamical characteristics of two wet years in the Sahel and two dry years. The model simulations show consistent contrasts in wave activity between the wet and dry years. The waves are markedly stronger in the wet years and show a barotropic structure throughout the troposphere. The waves tend to extend throughout the troposphere to the level of the tropical easterly jet (TEJ) in the wet years, but not in the dry years. The upper-tropospheric shear, which is stronger in wet years, appears to be a key factor in wave development. This shear is dependent on'the intensity of the TEJ, suggesting that the TEJ is an important factor in interannual variability in the Sahel. When the overall shear is weak, vertical development is suppressed. Another contrast is that in the dry years the growth rates show a single maximum around 3000-4000 km, but in the wet years there is a second, around 6000-7000 km. This suggests that both synoptic-scale and planetary-scale waves are active in the rainy season of some wet years. Imposing considerations of potential vorticity, the generation of planetary-scale waves implies a strong link between the surface and the TEJ in wet years. Such a link is absent in the dry years. This is likely a major factor in the interannual variability of rainfall in the Sahel. © 2008 American Meteorological Society."
"7202741460;14834158800;","Potential vorticity aspects of the MJO",2006,"10.1016/j.dynatmoce.2006.02.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749658781&doi=10.1016%2fj.dynatmoce.2006.02.003&partnerID=40&md5=d45e29d7dfc8cd0a2e846f71567c3ab7","Considering linearized motion about a resting basic state, we derive analytical solutions of the equatorial β-plane primitive equations under the assumption that the flow is steady in a reference frame moving eastward with a diabatic forcing resembling a Madden-Julian Oscillation (MJO) convective envelope. The solutions are analyzed in terms of potential vorticity (PV) dynamics. Because the diabatic source term for PV contains a factor β y, the diabatic heat source is ineffective at generating a PV anomaly at the equator but maximizes the PV response near the poleward edges of the heat source. In this way a moving heat source can produce two ribbons of lower tropospheric PV anomaly, a positive one off the equator in the northern hemisphere and a negative one off the equator in the southern hemisphere, with oppositely signed PV anomalies in the upper troposphere. Associated with these PV anomalies are geopotential anomalies that are shifted several hundred kilometers poleward. In the lower troposphere these zonally elongated geopotential anomalies resemble ITCZ trough zones, which demonstrates the close connection between the MJO wake dynamics and the formation of double ITCZs. To demonstrate that the MJO wake response can be described by simple PV dynamics, we propose an invertibility principle relating the PV to the streamfunction, which in turn is locally related to the geopotential. This equatorial invertibility principle accurately recovers the balanced wind and mass fields found in the MJO wake in the primitive equation model. However, while the invertibility principle highlights the ability of simple PV dynamics to accurately describe the flow in the wake of an MJO convective envelope, it also clearly illustrates the inability of such dynamics to describe the Kelvin-like flow pattern ahead of the convection. © 2006 Elsevier B.V. All rights reserved."
"6603169474;7004978125;","Boundary layer dissipation and the nonlinear interaction of equatorial baroclinic and barotropic Rossby waves",2004,"10.1080/03091920410001686712","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5044229214&doi=10.1080%2f03091920410001686712&partnerID=40&md5=9ce7ad78c958f7a8c9969d8ea1e2cfea","Two-layer equatorial primitive equations for the free troposphere in the presence of a thin atmospheric boundary layer and thermal dissipation are developed here. An asymptotic theory for the resonant nonlinear interaction of long equatorial baroclinic and barotropic Rossby waves is derived in the presence of such dissipation. In this model, a self-consistent asymptotic derivation establishes that boundary layer flows are generated by meridional pressure gradients in the lower troposphere and give rise to degenerate equatorial Ekman friction. That is to say, the asymptotic model has the property that the dissipation matrix has one eigenvalue which is nearly zero: therefore the dynamics rapidly dissipates flows with pressure at the base of the troposphere and creates barotropic/baroclinic spin up/spin down. The simplified asymptotic equations for the amplitudes of the dissipative equatorial barotropic and baroclinic waves are studied by linear theory and integrated numerically. The results indicate that although the dissipation slightly weakens the tropics to midlatitude connection, strong localized wave packets are nonetheless able to exchange energy between barotropic and baroclinic waves on intraseasonal timescales in the presence of baroclinic mean shear. Interesting dissipation balanced wave-mean flow states are discovered through numerical simulations. In general, the boundary layer dissipation is very efficient for flows in which the barotropic and baroclinic components are of the same sign at the base of the free troposphere whereas the boundary layer dissipation is less efficient for flows whose barotropic and baroclinic components are of opposite sign at the base of the free troposphere. © 2004 Taylor and Francis Ltd."
"7102160097;56160100900;6701831809;7004471232;","Can we improve the representation of modeled ocean mixed layer by assimilating surface-only satellite-derived data? A case study for the tropical Pacific during the 1997-1998 El Niño",2003,"10.1029/2002jc001603","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141724791&doi=10.1029%2f2002jc001603&partnerID=40&md5=636c18c662dcbd80dc062330eee05469","In the tropical oceans the density mixed layer does influence the ocean-atmosphere interactions, a feature that is fundamental to the development of energetic climatic events such as the El Niño-Southern Oscillation (ENSO) phenomenon. The aim of this work is to take advantage of existing sea surface temperature (SST) and velocity together with future sea surface salinity (SSS) satellite-derived data by assimilating these data in a primitive equation model in order to improve the modeled mixed layer. As satellite SSS data are not yet available, and to better analyze how assimilation works, we performed twin experiments in a context that renders assimilation conclusive with regard to real experiment. Two simulations using different forcing were used for the experiments. They have errors that are comparable to the ones between any simulation and real observations. The assimilation scheme is an adaptive version of the SEEK filter [Pham et al., 1998] readily usable for assimilating real data. An assimilation experiment was conducted covering the 1997-1998 ENSO event to analyze the main characteristics of the actual mixed layer. Looking in particular at the relevance of SSS, SST, mixed layer depth, and barrier layer thickness, satellite-derived data prove to be useful to better simulate the oceanic mixed layer. Velocity data are specially needed to control the zonal equatorial current. Interestingly, assimilation of surface-only data still worked well below the mixed layer, and some improvements were detectable in terms of barrier layer thickness, even though the limit of the assimilation scheme was reached."
"7102160097;56160100900;6701831809;7004471232;","Assimilation of sea surface salinity in a tropical Oceanic General Circulation Model (OGCM): A twin experiment approach",2002,"10.1029/2001jc000849","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037569581&doi=10.1029%2f2001jc000849&partnerID=40&md5=a948e9fbec231b5be2e1e87c56d4b96f","Observing ocean surface salinity in the global ocean is a challenging issue for future years' oceanographic activities. It is motivated by the active role of salinity that is now well recognized in ocean dynamics and ocean/atmosphere exchanges. This is particularly evident in the case of the El Niño Southern Oscillation (ENSO) phenomenon in the tropical Pacific Ocean. Improvements to ocean state estimation and predictions will require that salinity observations must be taken into proper account in conjunction with temperature and altimetric data. The sensitivity of a primitive equation model of the tropical Pacific Ocean to sea surface salinity (SSS) is studied through the use of a data assimilation technique in the rather academic ""twin experiment"" context. The data assimilation technique used, the Singular Evolutive Extended Kalman (SEEK) filter, is derived from the conventional Kalman filter theory. The paper explains why such a sophisticated technique is necessary. Indeed, an empirical scheme such as the Newtonian relaxation method, used in the same conditions, fails to constrain either the observed (surface) variable or the other components of the state vector. Within the experimental context chosen, the assimilation of SSS data with the SEEK filter is able to constrain most of the model variables linked with the SSS signal. SSS information, in particular, appears relatively successful in restoring zonal velocity, which is an important variable in warm/ fresh pool migration, and in simulating a barrier layer in the atmospheric convergence zones. The final analysis errors are small and stable over time. This is widely true when simulating satellite SSS observations based on the GODAE criteria (0.2 psu error, 200 km, 10 days), which shows the potential of these observations. To extend these results to a real context, the problems of model-data bias and unknown error covariances must be addressed as they are actually a strong limitation in assimilation performance when assimilating any real data set."
"7202611735;7003408439;","A model of rossby waves linked to submonthly convection over the eastern tropical Pacific",2000,"10.1175/1520-0469(2000)057<3785:AMORWL>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034351727&doi=10.1175%2f1520-0469%282000%29057%3c3785%3aAMORWL%3e2.0.CO%3b2&partnerID=40&md5=c672ad15a92c9c137665074ff3f08f3d","Equatorward-propagating wave trains in the upper troposphere are observed to be associated with deep convection over the eastern tropical Pacific on the submonthly timescale during northern winter. The convection occurs in the regions of ascent and reduced static stability ahead of cyclonic anomalies in the wave train. In this study an atmospheric primitive equation model is used to examine the roles of the dry wave dynamics and the diabetic heating associated with the convection. Many features of a dry integration initialized with a localized wave train in the African-Asian jet on a three-dimensional dimensional climatological basic state quantitatively agree with the observations, including the zonal wavenumber 6-7 scale of the waves, the time period of approximately 12 days, and the cross-equatorial Rossby wave propagation over the eastern Pacific. There is ascent and reduced static stability ahead of the cyclonic anomalies, consistent with the interpretation that the waves force the convection. The spatial scale of the waves appears to be set by the basic state: baroclinic growth upstream in the Asian jet favors waves with zonal wavenumber 6. On reaching the Pacific sector, lower-wavenumber components of the wave train are not refracted so strongly equatorward, while higher-wavenumber components are advected quickly along the Pacific jet before they can propagate equatorward. Once over the Pacific, the wave train approximately obeys barotropic Rossby wave dynamics. The observed lower-tropospheric anomalies include an equatorial Rossby wave that propagates westward from the region of cross-equatorial wave propagation and tropical convection. However, this equatorial Rossby wave is not forced directly by the dry equatorward-propagating wave train but appears in a separate integration as a forced response to the observed diabetic heating associated with the tropical convection."
"35572026100;6603195572;57193882808;6701670597;","Asymptotic approaches to convective quasi-equilibrium",2000,"10.1002/qj.49712656615","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033861299&doi=10.1002%2fqj.49712656615&partnerID=40&md5=b928834ea6927ddd39f1ed6fa529c735","The physical principle of convective quasi-equilibrium proposed by Arakawa and Schubert states that the atmosphere is effectively adjusted to equilibrium by an active role of convective heating against large-scale forcing (physical convective quasi-equilibrium, or PCQ). A simple consequence of this principle is that the rate of change of the thermodynamic field (typically measured by the convective available potential energy (CAPE)) is much smaller than the rate of change of the large-scale forcing (diagnostic convective quasi-equilibrium, or DCQ). Such a diagnostic state is generally observed in the tropical atmosphere at the synoptic-scale, and this is often taken as a proof for the physical mechanisms behind Arakawa and Schubert's convective quasi-equilibrium: however, theoretically, there are several alternative physical mechanisms that are also able to establish this diagnostic state. The paper examines the approach of the tropical atmospheric system to DCQ with increasing time-scale in order to distinguish various alternatives to PCQ. The latter predicts that the system approaches DCQ exponentially with a time-scale characteristic of convection. However, the alternatives considered in the paper predict algebraic asymptotes to DCQ with increasing time-scale. First it is demonstrated that PCQ is not required to achieve DCQ by considering a linear primitive-equation system with arbitrary convective heating, in which the roles of convective heating and large-scale forcing are completely reversed; algebraic asymptotes are achieved. An even simpler analogue is to assume that the rate of generating CAPE is controlled by white-noise forcing. More generally, such an algebraic asymptote is obtained by any system with a power-law spectrum both for CAPE and large-scale forcing, although a restriction must be applied to ensure a decreasing asymptote with increasing time-scale. The approach to DCQ is examined for both the Maritime Continent Thunderstorm Experiment data and cloud-resolving model simulation data, and both indicate no tendency for exponential adjustments in the short time limit."
"56253209700;","Stability of steady fronts with uniform potential vorticity",1995,"10.1175/1520-0469(1995)052<0724:sosfwu>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029106096&doi=10.1175%2f1520-0469%281995%29052%3c0724%3asosfwu%3e2.0.co%3b2&partnerID=40&md5=5637cc88f2d235973320bc1b984917c4","The linear stability of steady frontal zones is considered using the primitive equations. The frontal zones chosen have uniform potential vorticity and form a sequence of ""snapshots' of the deformation- induced front as it evolves toward frontal collapse. The stability for a given alongfront wavelength is determined by integrating a numerical model forward from an initial condition of the basic-state front plus white noise. Two classes of instabilities emerge. In one class, the modes are modified versions of familiar, synoptic-scale baroclinic waves. The other class consists of Kelvin-Helmboltz (KH) instabilities. -Author"
"7402942478;7005548544;","On the establishment of stationary waves in the Northern Hemisphere winter",1993,"10.1175/1520-0469(1993)050<0043:OTEOSW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027385244&doi=10.1175%2f1520-0469%281993%29050%3c0043%3aOTEOSW%3e2.0.CO%3b2&partnerID=40&md5=97b1d2a39ed217a8bf271038618d0dd5","The establishment of stationary waves in the Northern Hemisphere winter is investigated using stationary and time-dependent linear primitive equation models. Confirming the results of Nigam and Lindzen, we find that small displacements of the subtropical jet can cause significant changes in the stationary-wave response. The time scale for stationary establishment is found to be on the order of 5 days, both in the troposphere and in the lower stratosphere. The exception is for a northward shift of the subtropical jet, in which case the establishment of the new stationary solution in the stratosphere occurs on a longer time scale, which is mainly determined by dissipation. Implications for low-frequency atmospheric variability and mid- and long-range weather forecasting are discussed. -Authors"
"6701513498;57206269467;6507914868;6505492327;","Advances in the Theory of Atmospheric Fronts",1985,"10.1016/S0065-2687(08)60190-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022197175&doi=10.1016%2fS0065-2687%2808%2960190-9&partnerID=40&md5=ccffa18c001171124f178b8386c6947e","This chapter examines the advances in the theory of atmospheric fronts. The observation of convergence lines at boundaries among air masses has had profound implications for theoretical and applied meteorology. The primary breakthrough in the understanding of the relationship between surface frontogenesis and the evolution of planetary waves resulted from the primitive-equation numerical simulation. In the numerical solution, growing finite-amplitude baroclinic waves produced regions of more intense temperature gradients suggestive of frontal zones. The comparison of the theoretical model results with Williams's numerical solution showed that Hoskins's equation system with the semigeostrophic approximation produced most of the features that Williams's primitive-equation system provided but with the advantage that an analytic solution could be found for the frontogenesis problem. The presence of persistent vortex stretching near the surface in the semigeostrophic equations produces an unbounded growth of vorticity until the semigeostrophic approximation is no longer valid. © 1985, Academic Press, Inc."
"7006961728;57192120809;7006298660;","A model of the atmospheric boundary layer over the marginal ice zone ( Bering Sea).",1983,"10.1029/JC088iC05p02836","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021032938&doi=10.1029%2fJC088iC05p02836&partnerID=40&md5=651f602bf629ba1277f781c005092671","A one-layer, primitive equation model is presented for the atmospheric boundary layer over the marginal ice zone (MIZ). The model simulates the slow rate of inversion growth and rate of warming of the boundary layer seaward of an ice edge for off-ice winds observed on two cruises in the Bering Sea by the NOAA R/V Surveyor. Results suggest an atmospheric mechanism for rafting at the windward side of the marginal ice zone, divergence of the ice at the edge, and ice-band formation seaward of the edge.-from Authors"
"57190608540;56575686800;7003991093;","Regime change behavior during Asian monsoon onset",2018,"10.1175/JCLI-D-17-0118.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85043238575&doi=10.1175%2fJCLI-D-17-0118.1&partnerID=40&md5=4ee713b98cbe585546287a8ea406020d","As the ITCZ moves off the equator on an aquaplanet, the Hadley circulation transitions from an equinoctial regime with two near-symmetric, significantly eddy-driven cells to a monsoon-like regime with a strong, thermally direct cross-equatorial cell, intense low-latitude precipitation, and a weak summer hemisphere cell. Dynamical feedbacks appear to accelerate the transition. This study investigates the relevance of this behavior to monsoon onset by using primitive equation model simulations ranging from aquaplanets to more realistic configurations with Earth's continents and topography. A change in the relationship between ITCZ latitude and overturning strength is identified once the ITCZ moves poleward of approximately 7°. Monsoon onset is associated with off-equatorial ascent in regions of nonnegligible planetary vorticity, and this is found to generate a vortex stretching tendency that reduces upper-level absolute vorticity. In an aquaplanet, this causes a transition to the cross-equatorial, thermally direct regime, intensifying the overturning circulation. Analysis of the zonal momentum budget suggests that a stationary wave, driven by topography and land-sea contrast, can trigger a similar transition in the more realistic model configuration, with the wave extending the ascent region of the Southern Hemisphere Hadley cell northward, and enhanced overturning then developing to the south. These two elements of the circulation resemble the East and South Asian monsoons. © 2018 American Meteorological Society."
"6603356769;8844177800;","A deformation-based parametrization of ocean mesoscale eddy reynolds stresses",2017,"10.1016/j.ocemod.2017.02.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013017030&doi=10.1016%2fj.ocemod.2017.02.004&partnerID=40&md5=6868b239c8c2011a20219788e04e7e26","Ocean mesoscale eddies strongly affect the strength and variability of large-scale ocean jets such as the Gulf Stream and Kuroshio Extension. Their spatial scales are too small to be fully resolved in many current climate models and hence their effects on the large-scale circulation need to be parametrized. Here we propose a parametrization of mesoscale eddy momentum fluxes based on large-scale flow deformation. The parametrization is argued to be suitable for use in eddy-permitting ocean general circulation models, and is motivated by an analogy between turbulence in Newtonian fluids (such as water) and laminar flow in non-Newtonian fluids. A primitive-equations model in an idealised double-gyre configuration at eddy-resolving horizontal resolution is used to diagnose the relationship between the proposed closure and the eddy fluxes resolved by the model. Favourable correlations suggest the closure could provide an appropriate deterministic parametrization of mesoscale eddies. The relationship between the closure and different representations of the Reynolds stress tensor is also described. The parametrized forcing possesses the key quasi-geostrophic turbulence properties of energy conservation and enstrophy dissipation, and allows for upgradient fluxes leading to the sharpening of vorticity gradients. The implementation of the closure for eddy-permitting ocean models requires only velocity derivatives and a single parameter that scales with model resolution. © 2017 The Authors"
"19337780500;7004208552;","Internal-tide interactions with the Gulf Stream and Middle Atlantic Bight shelfbreak front",2016,"10.1002/2016JC011639","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983338558&doi=10.1002%2f2016JC011639&partnerID=40&md5=c63083d63e87ac4411aa604320b0ea33","Internal tides in the Middle Atlantic Bight region are found to be noticeably influenced by the presence of the shelfbreak front and the Gulf Stream, using a combination of observations, equations, and data-driven model simulations. To identify the dominant interactions of these waves with subtidal flows, vertical-mode momentum and energy partial differential equations are derived for small-amplitude waves in a horizontally and vertically sheared mean flow and in a horizontally and vertically variable density field. First, the energy balances are examined in idealized simulations with mode-1 internal tides propagating across and along the Gulf Stream. Next, the fully nonlinear dynamics of regional tide-mean-flow interactions are simulated with a primitive-equation model, which incorporates realistic summer-mesoscale features and atmospheric forcing. The shelfbreak front, which has horizontally variable stratification, decreases topographic internal-tide generation by about 10% and alters the wavelengths and arrival times of locally generated mode-1 internal tides on the shelf and in the abyss. The (sub)mesoscale variability at the front and on the shelf, as well as the summer stratification itself, also alter internal-tide propagation. The Gulf Stream produces anomalous regions of O(20 mW m−2) mode-1 internal-tide energy-flux divergence, which are explained by tide-mean-flow terms in the mode-1 energy balance. Advection explains most tide-mean-flow interaction, suggesting that geometric wave theory explains mode-1 reflection and refraction at the Gulf Stream. Geometric theory predicts that offshore-propagating mode-1 internal tides that strike the Gulf Stream at oblique angles (more than thirty degrees from normal) are reflected back to the coastal ocean, preventing their radiation into the central North Atlantic. © 2016. American Geophysical Union. All Rights Reserved."
"16162149600;8750834400;8420354200;36155758500;13606959300;","Vertical propagation of planetary-scale waves in variable background winds in the upper cloud region of Venus",2015,"10.1016/j.icarus.2014.07.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919780765&doi=10.1016%2fj.icarus.2014.07.011&partnerID=40&md5=1fbbb556a755f34e07d26b9de65aaa3a","Recently it was found that the low-latitude zonal wind and the amplitudes of Kelvin and Rossby waves at the cloud top of Venus show long-term variations in a synchronized manner. For the purpose of explaining this synchronization, we investigated the influence of the background zonal wind profile on the upward propagation of Kelvin and Rossby waves at altitudes 60-80. km. Results from a linearized primitive equation model suggests that Kelvin waves can reach the cloud top height when the background wind speed is slow, whereas Rossby waves can reach the cloud top when the background wind speed is fast. These features obtained from the model are consistent with the observations. Since the momentum deposition by these waves can accelerate or decelerate the mean flow, these waves may contribute to the variation of the background wind. The calculated spatial distributions of the momentum dissipation indicate that the Kelvin waves accelerate the low-latitude atmosphere, and thus they can act to induce transition from the slow wind period to the fast wind period. On the other hand, the Rossby waves decelerate mainly the mid-latitude atmosphere, so that additional mechanisms are required to decelerate the low-latitude atmosphere. A possible mechanism is momentum advection caused by the Rossby wave-induced meridional circulation. © 2014 Elsevier Inc."
"36998033800;36102803900;8558370300;7201746369;","Rossby waves mediate impacts of tropical oceans on west Antarctic atmospheric circulation in austral winter",2015,"10.1175/JCLI-D-15-0113.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84947594656&doi=10.1175%2fJCLI-D-15-0113.1&partnerID=40&md5=123415c3f6b1c4c96a1c39ab33216242","Recent studies link climate change around Antarctica to the sea surface temperature of tropical oceans, with teleconnections from the Pacific, Atlantic, and Indian Oceans making different contributions to Antarctic climate. In this study, the impacts of each ocean basin on the wintertime Southern Hemisphere circulation are identified by comparing simulation results using a comprehensive atmospheric model, an idealized dynamical core model, and a theoretical Rossby wave model. The results herein show that tropical Atlantic Ocean warming, Indian Ocean warming, and eastern Pacific cooling are all able to deepen the Amundsen Sea low located adjacent to West Antarctica, while western Pacific warming increases the pressure to the west of the international date line, encompassing the Ross Sea and regions south of the Tasman Sea. In austral winter, these tropical ocean basins work together linearly to modulate the atmospheric circulation around West Antarctica. Further analyses indicate that these teleconnections critically depend on stationary Rossby wave dynamics and are thus sensitive to the background flow, particularly the subtropical/midlatitude jet. Near these jets, wind shear is amplified, which strengthens the generation of Rossby waves. On the other hand, near the edges of the jets the meridional gradient of the absolute vorticity is also enhanced. As a consequence of the Rossby wave dispersion relationship, the jet edge may reflect stationary Rossby wave trains, serving as a waveguide. The simulation results not only identify the relative roles of each of the tropical ocean basins in the tropical-Antarctica teleconnection, but also suggest that a deeper understanding of teleconnections requires a better estimation of the atmospheric jet structures. © 2015 American Meteorological Society."
"55940993400;57210837523;","Comparisons of empirical localization techniques for serial ensemble kalman filters in a simple atmospheric general circulation model",2014,"10.1175/MWR-D-13-00152.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893859982&doi=10.1175%2fMWR-D-13-00152.1&partnerID=40&md5=66bb37804f21603cc57832713357b99e","Two techniques for estimating good localization functions for serial ensemble Kalman filters are compared in observing system simulation experiments (OSSEs) conducted with the dynamical core of an atmospheric general circulation model. The first technique, the global group filter (GGF), minimizes the root-mean-square (RMS) difference between the estimated regression coefficients using a hierarchical ensemble filter. The second, the empirical localization function (ELF), minimizes the RMS difference between the true values of the state variables and the posterior ensemble mean. Both techniques provide an estimate of the localization function for an observation's impact on a state variable with few a priori assumptions about the localization function. The ELF localizations can have values larger than 1.0 at small distances, indicating that this technique addresses localization but also can correct the prior ensemble spread in the same way as a variance inflation when needed. OSSEs using ELF localizations generally have smaller root-mean-square error (RMSE) than the optimal Gaspari and Cohn (GC) localization function obtained by empirically tuning the GC width. The localization functions estimated by the GGF are broader than those from the ELF, and the OSSEs with the GGF localization generally have larger RMSE than the optimal GC localization function. The GGFs are too broad because of spurious correlation biases that occur in the OSSEs. These errors can be reduced by using a stochastic EnKF with perturbed observations instead of a deterministic EAKF. © 2014 American Meteorological Society."
"6603178923;56828803500;6603090797;","Numerical model of the hydrodynamics of the Black Sea and the Sea of Azov with variational initialization of temperature and salinity",2013,"10.1134/S0001433813060133","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890875329&doi=10.1134%2fS0001433813060133&partnerID=40&md5=6c0c157099709cf4610a9caec6d2e014","A numerical primitive-equation model of the hydrodynamics of the Black Sea and the Sea of Azov in σ-coordinates is proposed. The model has a resolution of ∼4 × 4 km in horizontal coordinates with 40-σ levels in the vertical and includes the four-dimensional variational initialization of temperature and salinity fields. A numerical initialization algorithm combines splitting methods and adjoint equations. Flow, temperature, sea level, and salinity fields driven by atmospheric forcing are calculated for the year 2008. The calculations are made in a variational initialization - prediction regime. Temperature and salinity fields are initialized at the end of each month. The optimality system includes forward and adjoint transport-diffusion equations for heat and salt that are linearized on the assimilation interval. Results of three numerical experiments with different sets of assimilated data in comparison with the prediction obtained from the forward model are discussed. © 2013 Pleiades Publishing, Ltd."
"12139081400;7203088716;","Horizontal momentum diffusion in GCMs using the dynamic smagorinsky model",2013,"10.1175/MWR-D-12-00101.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875685420&doi=10.1175%2fMWR-D-12-00101.1&partnerID=40&md5=d7b4d32d010eeda828debdcaa11468ac","A dynamic version of Smagorinsky's diffusion scheme is presented that is applicable for large-eddy simulations (LES) of the atmospheric dynamics. The approach is motivated (i) by the incompatibility of conventional hyperdiffusion schemes with the conservation laws, and (ii) because the conventional Smagorinsky model (which fulfills the conservation laws) does not maintain scale invariance, which is mandatory for a correct simulation of the macroturbulent kinetic energy spectrum. The authors derive a two-dimensional (horizontal) formulation of the dynamic Smagorinsky model (DSM) and present three solutions of the socalled Germano identity: the method of least squares, a solution without invariance of the Smagorinsky parameter, and a tensor-norm solution. The applicability of the tensor-norm approach is confirmed in simulations with the Kühlungsborn mechanistic general circulation model (KMCM). The standard spectral dynamical core of the model facilitates the implementation of the test filter procedure of the DSM. Various energy spectra simulated with the DSM and the conventional Smagorinsky scheme are presented. In particular, the results show that only the DSM allows for a reasonable spectrum at all scales. Latitude-height cross sections of zonal-mean fluid variables are given and show that the DSM preserves the main features of the atmospheric dynamics. The best ratio for the test-filter scale to the resolution scale is found to be 1.33, resulting in dynamically determined Smagorinsky parameters cS from 0.10 to 0.22 in the troposphere. This result is very similar to other values of cS found in previous three-dimensional applications of the DSM. © 2013 American Meteorological Society."
"22950688100;6507671561;","Differing impacts of resolution changes in latitude and longitude on the midlatitudes in the LMDZ atmospheric GCM",2011,"10.1175/2011JCLI4093.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-83755183432&doi=10.1175%2f2011JCLI4093.1&partnerID=40&md5=c2dd72972829edc66efae572e6af3c0e","This article examines the sensitivity of the Laboratoire de Météorologie Dynamique Model with Zoom Capability (LMDZ), a gridpoint atmospheric GCM, to changes in the resolution in latitude and longitude, focusing on the midlatitudes. In a series of dynamical core experiments, increasing the resolution in latitude leads to a poleward shift of the jet, which also becomes less baroclinic, while the maximum eddy variance decreases. The distribution of the jet positions in time also becomes wider. On the contrary, when the resolution increases in longitude, the position and structure of the jet remain almost identical, except for a small equatorward shift tendency. An increase in eddy heat flux is compensated by a strengthening of the Ferrel cell. The source of these distinct behaviors is then explored in constrained experiments in which the zonal-mean zonal wind is constrained toward the same reference state while the resolution varies. While the low-level wave sources always increase with resolution in that case, there is also enhanced poleward propagation when increasing the resolution in longitude, preventing the jet shift. The diverse impacts on the midlatitude dynamics hold when using the full GCM in a realistic setting, either forced by observed SSTs or coupled to an ocean model. © 2011 American Meteorological Society."
"7402725328;7406243250;7202192265;13406399300;6603753099;6701357023;","Evaluation of the HOMME dynamical core in the aquaplanet configuration of NCAR CAM4: Rainfall",2011,"10.1175/2011JCLI3860.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052799976&doi=10.1175%2f2011JCLI3860.1&partnerID=40&md5=a5da750c8bfdf3441d58d3b2b240e4d9","The NCAR Community Climate System Model, version 4 (CCSM4), includes a new dynamical core option based on NCAR's High-Order Method Modeling Environment (HOMME). HOMME is a petascale-capable high-order element based conservative dynamical core developed on the cubed-sphere grid. Initial simulations have been completed in an aquaplanet configuration of the Community Atmosphere Model, version 4 (CAM4), the atmospheric component of CCSM4. The authors examined the results of this simulation and assessed its fidelity in simulating rainfall, which is one of the most important components of the earth's climate system. For this they compared the results from two other dynamical cores of CAM4: the finite volume (FV) and Eulerian (EUL). Instantaneous features of rainfall in HOMME are similar to FV and EUL. Similar to EUL and FV, HOMME simulates a single-peak intertropical convergence zone (ITCZ) over the equator. The strength of the ITCZ is found to be almost the same in HOMME and EUL but more in FV. It is observed that in HOMME and EUL, there is higher surface evaporation, which supplies more moisture to the deep tropics and gives more rainfall over the ITCZ. The altitude of maximum precipitation is found to be at almost the same level in all three dynamical cores. The eastward propagation of rainfall bands is organized and more prominent in FV and HOMME than in EUL. The phase speed of the eastward propagation in HOMME is found to be higher than in FV. The results show that, in general, the rainfall simulated by HOMME falls in a regime between that of FV and EUL. Hence, they conclude that the key aspects of rainfall simulation with HOMME falls into an acceptable range, as compared to the existing dynamical cores used in the model. © 2011 American Meteorological Society."
"26221127400;7004041202;7003975505;","Present-day arctic sea ice variability in the coupled ECHAM5/MPI-OM model",2010,"10.1175/2009JCLI3065.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954369582&doi=10.1175%2f2009JCLI3065.1&partnerID=40&md5=26a9eb0b831446a9cc8187535d709102","As a contribution to a detailed evaluation of Intergovernmental Panel on Climate Change (IPCC)-type coupled climate models against observations, this study analyzes Arctic sea ice parameters simulated by the Max-Planck-Institute for Meteorology (MPI-M) fully coupled climate model ECHAM5/Max-Planck-Institute for Meteorology Hamburg Primitive Equation Ocean Model (MPI-OM) for the period from 1980 to 1999 and compares them with observations collected during field programs and by satellites. Results of the coupled run forced by twentieth-century CO2 concentrations show significant discrepancies during summer months with respect to observations of the spatial distribution of the ice concentration and ice thickness. Equally important, the coupled run lacks interannual variability in all ice and Arctic Ocean parameters. Causes for such big discrepancies arise from errors in the ECHAM5/MPI-OM atmosphere and associated errors in surface forcing fields (especially wind stress). This includes mean bias pattern caused by an artificial circulation around the geometric North Pole in its atmosphere, as well as insufficient atmospheric variability in the ECHAM5/MPI-OM model, for example, associated with Arctic Oscillation/North Atlantic Oscillation (AO/NAO). In contrast, the identical coupled ocean-ice model, when driven by NCEP-NCAR reanalysis fields, shows much increased skill in its ice and ocean circulation parameters. However, common to both model runs is too strong an ice export through the Fram Strait and a substantially biased heat content in the interior of the Arctic Ocean, both of which may affect sea ice budgets in centennial projections of the Arctic climate system. © 2010 American Meteorological Society."
"6603435381;7006901882;","Detecting unstable structures and controlling error growth by assimilation of standard and adaptive observations in a primitive equation ocean model",2006,"10.5194/npg-13-67-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846275584&doi=10.5194%2fnpg-13-67-2006&partnerID=40&md5=1d1ae74c2f649f92db40e7e82249af85","Oceanic and atmospheric prediction is based on cyclic analysis-forecast systems that assimilate new observations as they become available. In such observationally forced systems, errors amplify depending on their components along the unstable directions; these can be estimated by Breeding on the Data Assimilation System (BDAS). Assimilation in the Unstable Subspace (AUS) uses the available observations to estimate the amplitude of the unstable structures (computed by BDAS), present in the forecast error field, in order to eliminate them and to control the error growth. For this purpose, it is crucial that the observational network can detect the unstable structures that are active in the system. These concepts are demonstrated here by twin experiments with a large state dimension, primitive equation ocean model and an observational network having a fixed and an adaptive component. The latter consists of observations taken each time at different locations, chosen to target the estimated instabilities, whose positions and features depend on the dynamical characteristics of the flow. The adaptive placement and the dynamically consistent assimilation of observations (both relying upon the estimate of the unstable directions of the data-forced system), allow to obtain a remarkable reduction of errors with respect to a non-adaptive setting. The space distribution of the positions chosen for the observations allows to characterize the evolution of instabilities, from deep layers in western boundary current regions, to near-surface layers in the eastward jet area. © 2006 Author(s)."
"7003750400;7005759537;","A unified perspective on the dynamics of axisymmetric hurricanes and monsoons",2006,"10.1175/JAS3763.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750599500&doi=10.1175%2fJAS3763.1&partnerID=40&md5=ab9f38acf4c6296d16dcc14e5e6c4a15","This paper provides a unified perspective on the dynamics of hurricane- and monsoonlike vortices by identifying them as specific limiting cases of a more general flow system. This more general system is defined as stationary axisymmetric balanced flow of a stably stratified non-Boussinesq atmosphere on the f plane. The model is based on the primitive equations assuming gradient wind balance in the radial momentum equation. The flow is forced by heating in the vortex center, which is implemented as relaxation toward a specified equilibrium temperature Te. The flow is dissipated through surface friction, and it is assumed to be almost inviscid in the interior. The heating is assumed supercritical, which means that Te does not allow a regular thermal equilibrium solution with zero surface wind, and which gives rise to a cross-vortex secondary circulation. Numerical solutions are obtained using time stepping to a steady state, where at each step the Eliassen secondary circulation is diagnosed as part of the solution strategy. Reality and regularity of the solution is discussed, putting this work in relation to previous work. Scaling analysis suggests that for a given geometry, essential vortex properties are controlled by the ratio F = αT/CD, where αT is the rate of thermal relaxation and CD quantifies the strength of surface friction for a given surface wind. For large F, the temperature is close to Te and the vortex shows properties that can be associated with a hurricane including strong cyclonic surface winds. On the other hand, for small F, the vortex shows properties that can be associated with a monsoon; that is, the surface winds are small and the secondary circulation keeps the temperature significantly away from Te. The scaling analysis is verified by numerical solutions spanning a wide range of the parameter space. It is shown how the two limiting cases correspond with the respective approximate semianalytical theories presented previously. The results imply an important role of or for hurricane formation. © 2006 American Meteorological Society."
"7202082738;57203598634;7202662751;7003495590;7005343619;","Blue crab larval dispersion and retention in the Mississippi Bight: Testing the hypothesis",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0142134393&partnerID=40&md5=6c4729c663237c31e77b2989a65b41c7","An hypothesis relating physical forcing to dispersion and retention of blue crab larvae was tested in the area of the Mississippi Bight. Seasonal circulation patterns derived from a 3-dimensional, primitive equation, sigma-coordinate model of the Gulf of Mexico (GOM) indicate favorable conditions for offshore dispersal of larvae and their return to nearshore waters as megalopae occur between April and October. Large basin-scale events, such as Loop Current intrusions into the GOM with spin-off eddy generation and anomalies in average wind stress may interrupt this circulation pattern and change the settlement success rate. Meteorological and hydrological factors thought to influence settlement were compared to daily records of megalopal abundance in Mississippi Sound for the years 1991 through 1999. Wind stress was strongly correlated with settlement success. Eastward wind stress during the months of July and August, when the larvae are at sea, and westward wind stress during recruitment in September and October were important in retaining larvae in the general area and subsequently returning them near shore as megalopae, respectively. Northward intrusion of the Loop Current and warm core ring detachment during late summer altered circulation patterns and decreased settlement success."
"7201978222;7004014731;","Radiative influence of Antarctica on the polar-night vortex",2001,"10.1175/1520-0469(2001)058<1300:RIOAOT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035872673&doi=10.1175%2f1520-0469%282001%29058%3c1300%3aRIOAOT%3e2.0.CO%3b2&partnerID=40&md5=390779fd540e5d699699875d199a5b87","Temperatures over the Antarctic plateau are sharply colder than those over its maritime surroundings. The sharp temperature contrast due to Antarctica is conveyed upward through 9.6-μm absorption by ozone, which shapes the thermal structure in the stratosphere. The radiative impact of Antarctica on the polar stratosphere is investigated in three-dimensional integrations of the nonlinear primitive equations, coupled to a full radiative-transfer calculation that is performed with and without clouds. Cooling associated with Antarctica depresses radiative-equilibrium temperatures by as much as 10 K. This direct radiative influence emerges clearly at high latitudes of the lowermost stratosphere. It is accompanied elsewhere by temperature changes of opposite sign, which result indirectly through adiabatic warming by the induced residual meridional circulation. Collectively, these influences reinforce the polar-night vortex, shift the jet axis poleward, and intensify downward transport over the polar cap by the residual circulation. In this way, radiative forcing from below contributes significantly to the features that distinguish the Antarctic vortex from the Arctic vortex."
"7103342287;7102346999;7201978222;7004014731;","A hough spectral model for three-dimensional studies of the middle atmosphere",1999,"10.1175/1520-0469(1999)056<1461:AHSMFT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033150006&doi=10.1175%2f1520-0469%281999%29056%3c1461%3aAHSMFT%3e2.0.CO%3b2&partnerID=40&md5=3886ecc8157c561468690f1aadc593ae","A three-dimensional framework is developed for studying the middle atmosphere in relation to upper-tropospheric structure. The numerical model is formulated from the primitive equations in isentropic coordinates, which directly characterize diabatic processes forcing the Brewer-Dobson circulation. It is anchored in observed tropospheric variability, so integrations provide middle atmospheric behavior that tracks observed variations in the upper troposphere. The numerical framework is versatile and computationally efficient. It achieves enhanced performance by incorporating eigenfunctions of the primitive equations to represent structure spectrally in all three coordinates. Scale-selective dissipation can then be applied entirely at sixth order, which leaves all but the shortest vertical scales undamped. This feature allows vertical diffusion to be made small enough to represent stratospheric transport as advective (rather than diffusive) for most of the scales carried in the integration. Transport across the model's lower boundary, which is positioned near the tropopause, is calculated prognostically from diabatic processes in the middle atmosphere, in concert with tropospheric influences imposed at the bottom. Integrations in which different tropospheric influences are represented can then be used to provide an understanding of how transport and chemical composition depend on processes in the middle atmosphere and in the troposphere. Integrations forced by observed tropospheric behavior are validated against climatological structure, as well as tracer behavior deduced from satellite measurements. The isentropic formulation, together with sixth-order vertical dissipation, enable potential vorticity to be conserved quite accurately. The results throw light on the three-dimensional structure of the Brewer-Dobson circulation and how it follows from diabatic processes operating in the middle atmosphere and tropospheric processes operating below.A three-dimensional framework is developed for studying the middle atmosphere in relation to upper-tropospheric structure. The numerical model is formulated from the primitive equations in isentropic coordinates, which directly characterize diabatic processes forcing the Brewer-Dobson circulation. It is anchored in observed tropospheric variability, so integrations provide middle atmospheric behavior that tracks observed variations in the upper troposphere. The numerical framework is versatile and computationally efficient. It achieves enhanced performance by incorporating eigenfunctions of the primitive equations to represent structure spectrally in all three coordinates. Scale-selective dissipation can then be applied entirely at sixth order, which leaves all but the shortest vertical scales undamped. This feature allows vertical diffusion to be made small enough to represent stratospheric transport as advective (rather than diffusive) for most of the scales carried in the integration. Transport across the model's lower boundary, which is positioned near the tropopause, is calculated prognostically from diabatic processes in the middle atmosphere, in concert with tropospheric influences imposed at the bottom. Integrations in which different tropospheric influences are represented can then be used to provide an understanding of how transport and chemical composition depend on processes in the middle atmosphere and in the troposphere. Integrations forced by observed tropospheric behavior are validated against climatological structure, as well as tracer behavior deduced from satellite measurements. The isentropic formulation, together with sixth-order vertical dissipation, enable potential vorticity to be conserved quite accurately. The results throw light on the three-dimensional structure of the Brewer-Dobson circulation and how it follows from diabatic processes operating in the middle atmosphere and tropospheric processes operating below."
"57202721532;7402095113;","The effects of external forcing, dissipation and nonlinearity on the solutions of atmospheric equations",1997,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030667560&partnerID=40&md5=599425d470ce3a68406f80138bf0884a","Based on the primitive equations of the atmosphere, we study the effects of external forcing, dissipation and nonlinearity on the solutions of stationary motion and non-stationary motion. The results show that the asymptotic behavior of solutions of the forced dissipative nonlinear system is essentially different from that of the adiabatic non-dissipative system, the adiabatic dissipative system, the diabatic non-dissipative system and the diabatic dissipative linear system, and that the joint action of external forcing, dissipation and nonlinearity is the source of multiple equilibria. From this we can conclude that the important actions of diabatic heating and dissipation must be considered in the models of the long-term weather and the climate."
"7003689703;","Beta-induced transition of strong isolated eddies",1996,"10.1175/1520-0485(1996)026<2223:BITOSI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030435572&doi=10.1175%2f1520-0485%281996%29026%3c2223%3aBITOSI%3e2.0.CO%3b2&partnerID=40&md5=879549fc88f069deedf152abd7e65457","Strong eddies on the β plane are considered within the framework of the one-layer primitive equations. The attention is focused on calculating the β-induced changes to the spatial structure of the eddy, as well as the speed of its translation. In contrast to the earlier studies, the results of this paper are valid for eddies with Ro ∼ 1 and are applicable to both lenses and eddies in a layer of nonzero average depth. It is demonstrated that no steady solution exists for eddies translating at a speed inside the Rossby-wave speed range, reflecting that such eddies must radiate and lose energy. In addition to the speed restriction, steadily translating eddies must satisfy a certain constraint imposed on their far-field asymptotics."
"26430935600;7201507999;","Ocean model studies of upper-ocean variability of 0°, 160°W during the 1982-1983 ENSO: local and remotely forced response",1993,"10.1175/1520-0485(1993)023<0425:OMSOUO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027835115&doi=10.1175%2f1520-0485%281993%29023%3c0425%3aOMSOUO%3e2.0.CO%3b2&partnerID=40&md5=fa91cba7ccfca1f8b551b7c3fdea27d8","A hindcast of the 1982-1983 ENSO event using a primitive equation ocean circulation model forced by monthly mean wind stresses based on the SADLER pseudostress fields shows very good agreement with observations at 0°, 159°W between June 1982 and March 1983. Meridional wind stress changes have little effect on either the zonal velocity or temperature fields. Local zonal wind stress variations can account for the qualitative changes in the upper-ocean zonal flow, but cannot reproduce the observed thermal changes or the timing and quantitative evolution of the zonal flow. Remote forcing is needed to account for these latter aspects of the observations. Eastward-propagating Kelvin response appears to be quite important, but westward-propagating Rossby variance forced during 1982 from east of 160°W does not appear to play any significant role. The idealized remote-forcing experiments indicate that westerly events can account for the variability not explained by local forcing; the essential aspect is how the forcing projects onto the vertical modes defined by the stratification under the forcing at the time of the wind event. -from Authors"
"7004211281;7201439545;","A duality principle in semigeostrophic theory",1987,"10.1175/1520-0469(1987)044<3449:ADPIST>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023528747&doi=10.1175%2f1520-0469%281987%29044%3c3449%3aADPIST%3e2.0.CO%3b2&partnerID=40&md5=a6e78f743f51fdf021b267a4f0ac473f","The semigeostrophic equations are a filtered approximation to the primitive equations that have been applied with considerable success to the study of atmospheric frontogenesis and to the study of the influence of orography on the balanced component of flow. In the simplest Boussinesq and f-plane form of these equations the requirement that the instantaneous solutions should not be symmetrically unstable can be expressed geometrically as the need for a certain potential related to the geopotential field to a convex function. Conversely, any convex function can be associated directly with a stable solution of the semigeostrophic equations. This property of convexity is sufficient to allow a natural mapping from any instantaneous solution to a conjugate solution in which the roles of cyclonic and anticyclonic regions are reversed. In terms of this surprising duality, a solution possessing a mature surface front is associated with a conjugate solution whose flow is blocked or separated by orography, allowing some general conclusions concerning the appearance of surface fronts to be translated directly to corresponding statements concerning orographic blocking, and vice versa. -from Authors"
"7005454026;6602920335;","The effect of along- front temperature variation in a two- dimensional primitive equation model of surface frontogenesis.",1987,"10.1175/1520-0469(1987)044<0577:TEOAFT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023510933&doi=10.1175%2f1520-0469%281987%29044%3c0577%3aTEOAFT%3e2.0.CO%3b2&partnerID=40&md5=18fc668dacfc2d31f5d11c6db490d315","The central hypothesis (attributable to Eliassen) is that cold and warm fronts may be distinguished by the orientation of the cross-front thermal wind component and the sense of the associated along-front temperature variation. Three simulations comprising confluent forcing and differing initial specifications of the along-front potential temperature gradient are examined in detail. In the first simulation the along-front potential temperature gradient is set to zero, establishing a control for specifying along-front potential temperature variations respectively characteristic of cold and warm fronts in the latter 2 simulations. These simulations are referred to as the cold and warm advection cases, reflecting the initial sense of the potential temperature advection in the along-front direction at low levels in the model atmosphere.-from Authors"
"55119602800;57208455668;18435749300;11939929300;57192468922;57075896200;","Toward convective-scale prediction within the next generation global prediction system",2019,"10.1175/BAMS-D-17-0246.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065143927&doi=10.1175%2fBAMS-D-17-0246.1&partnerID=40&md5=8653d63efc3e123d74a35c4ac65e7d76","The variable-resolution version of a Finite-Volume Cubed-Sphere Dynamical Core (FV3)-based global model improves the prediction of convective-scale features while maintaining skillful global forecasts. © 2019 American Meteorological Society."
"23987208900;7102322882;56151271900;","Simulating Jupiter's weather layer. Part I: Jet spin-up in a dry atmosphere",2019,"10.1016/j.icarus.2018.12.005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062210204&doi=10.1016%2fj.icarus.2018.12.005&partnerID=40&md5=4c8794b61f81194dfef61eac3787fc1a","We investigate the dynamics of Jupiter's upper troposphere and lower stratosphere using a General Circulation Model that includes two-stream radiation and optional heating from below. Based on the MITgcm dynamical core, this is a new generation of Oxford's Jupiter General Circulation Model [Zuchowski, L.C. et al., 2009. Plan. Space Sci., 57, 1525–1537, doi:10.1016/j.pss.2009.05.008]. We simulate Jupiter's atmosphere at up to 0.7° horizontal resolution with 33 vertical levels down to a pressure of 18 bar, in configurations with and without a 5.7Wm −2 interior heat flux. Simulations ran for 130000–150000 d to allow the deep atmosphere to come into radiative equilibrium. Baroclinic instability generates alternating, eddy-driven, midlatitude jets in both cases. With interior heating the zonal jets migrate towards the equator and become barotropically unstable. This generates Rossby waves that radiate away from the equator, depositing westerly momentum there via eddy angular momentum flux convergence and spinning up a super-rotating 20ms −1 equatorial jet throughout the troposphere. There are 30–35 zonal jets with latitudinal separation comparable with the real planet, and there is strong eddy activity throughout. Without interior heating the jets do not migrate and a divergent eddy angular momentum flux at the equator spins up a broad, 50ms −1 sub-rotating equatorial jet with weak eddy activity at low latitudes. © 2018 The Authors"
"55940993400;7202748672;7202946344;","Improving Assimilation of Radiance Observations by Implementing Model Space Localization in an Ensemble Kalman Filter",2018,"10.1029/2018MS001468","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058996559&doi=10.1029%2f2018MS001468&partnerID=40&md5=7f8f0a8ec79c61dbf2a5edf5fab7b40c","Experiments using the National Oceanic and Atmospheric Administration Finite-Volume Cubed-Sphere Dynamical Core Global Forecasting System (FV3GFS) reveal that the four-dimensional ensemble-variational method (4DEnVAR) performs similarly to an ensemble Kalman filter (EnKF) when no radiance observations are assimilated, but 4DEnVAR is superior to an EnKF when radiance observations are assimilated. The hypothesis for the cause of the differences between 4DEnVAR and EnKF is the difference in vertical localization, since radiance observations are integral observations in the vertical and 4DEnVAR uses model space localization while the EnKF uses observation space localization. A modulation approach, which generates an expanded ensemble from the raw ensemble and eigenvectors of the localization matrix, has been adopted to implement model space localization in the operational National Oceanic and Atmospheric Administration EnKF. As constructed, the expanded ensemble is a square root of the vertically localized background error covariance matrix, so no explicit vertical localization is necessary during the EnKF update. The size of the expanded ensemble is proportional to the rank of the vertical localization matrix—for a vertical localization scale of 1.5 (3.0) scale heights, 12 (7) eigenvectors explain 96% of the variance of the localization matrix, so the expanded ensemble is 12 (7) times larger than the raw ensemble. Results from assimilating only radiance observations in the FV3GFS model confirm that EnKF with model-space vertical localization performs better than observation-space localization, and produces results similar to 4DEnVAR. Moreover, a 960-member ensemble is sufficient to turn off the vertical localization entirely and yields significant improvements comparing to an 80-member ensemble with model space localization. ©2018. The Authors."
"25031430500;7103342287;7005920812;36179077700;6701431208;13406399300;6506848305;7102696626;","Regional Climate Simulations With the Community Earth System Model",2018,"10.1002/2017MS001227","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85051268863&doi=10.1002%2f2017MS001227&partnerID=40&md5=fece987a884a20c7a1515b0c379f1a27","The spectral element (SE) variable-resolution (VR) mesh dynamical core is tested in developmental versions of the Community Earth System Model version 2 (CESM2). The SE dynamical core is tested in baroclinic wave, aquaplanet and full physics configurations to evaluate variable-resolution simulations against uniform high and uniform low-resolution simulations. Different physical parameterization suites are also evaluated to gauge their sensitivity to resolution. Dry dynamical core variable-resolution cases compare well to high-resolution tests. More recent versions of the atmospheric physics, including cloud schemes for CESM2, are less sensitive to changes in horizontal resolution. Most of the sensitivity is due to sensitivity to time step and interactions between deep convection and large-scale condensation, which is expected from the closure methods. The resulting full physics SE-VR model produces a similar climate to the global low-resolution mesh and similar high-frequency statistics in the high-resolution region. The SE-VR simulations are able to reproduce uniform high-resolution results, making them an effective tool for regional climate simulations at lower computational cost. Some biases are reduced (orographic precipitation in Western United States), but biases do not necessarily go away at high resolution (e.g., summertime surface temperatures). Variable-resolution grids are a viable alternative to traditional nesting for regional climate studies and are available in CESM2. © 2018. The Authors."
"14058428800;","Are sudden stratospheric warmings generic? Insights from an idealized GCM",2016,"10.1175/JAS-D-15-0353.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028505316&doi=10.1175%2fJAS-D-15-0353.1&partnerID=40&md5=67191a38a9a43646f7b11b0c099f853b","This work examines the life cycle of sudden stratospheric warmings (SSWs) from composites of a large number of events. The events are sampled from idealized general circulation model (GCM) integrations and form a database of several hundred major, displacement, splitting, and weak vortex events. It is shown that except for a few details, the generic zonal-mean evolution does not depend on the definition used to detect SSWs. In all cases, the composites show the stratosphere in a positive annular mode phase prior to the events and a barotropic response in the stratosphere at onset. There is a clear positive peak in upward Eliassen-Palm (EP) flux prior to the onset date in the stratosphere and a much weaker peak in the troposphere, making the evolution more consistent with the picture of the stratosphere acting as a variable filter of tropospheric EP flux, rather than SSWs being forced by a strong ''burst'' in the troposphere. When comparing composites of SSWs from the database with apparent influence at the surface (downward ''propagating'') to those without such influence, the only significant differences are a somewhat more barotropic response at the onset date and longer persistence in the lower stratosphere after the onset for propagating SSWs. There is no significant difference in EP flux between propagating and nonpropagating events, and none of the definitions considered here shows a particular skill in selecting propagating events. © 2016 American Meteorological Society."
"6506511319;","Met office unified model tropical cyclone performance following major changes to the initialization scheme and a model upgrade",2016,"10.1175/WAF-D-16-0040.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994159072&doi=10.1175%2fWAF-D-16-0040.1&partnerID=40&md5=5a2ecd67c78e17fbdae01325267a0c4b","The Met Office has used various schemes to initialize tropical cyclones (TCs) in its numerical weather prediction models since the 1980s. The scheme introduced in 1994 was particularly successful in reducing track forecast errors in the model. Following modifications in 2007 the scheme was still beneficial, although to a lesser degree than before. In 2012 a new trial was conducted that showed that the scheme now had a detrimental impact on TC track forecasts. As a consequence of this, the scheme was switched off. The Met Office Unified Model (MetUM) underwent a major upgrade in 2014 including a new dynamical core, changes to the model physics, an increase in horizontal resolution, and changes to satellite data usage. An evaluation of the impact of this change on TC forecasts found a positive impact both on track and particularly intensity forecasts. Following implementation of the new model formulation in 2014, a new scheme for initialization of TCs in the MetUM was developed that involved the assimilation of central pressure estimates from TC warning centers. A trial showed that this had a positive impact on both track and intensity predictions from the model. Operational results from the MetUM in 2014 and 2015 showed that the combined impact of the model upgrade and new TC initialization scheme was a dramatic cut in both TC track forecast errors and intensity forecast bias."
"7003372313;","Wind-induced equatorial bulge in Venus and Titan general circulation models: Implication for the simulation of superrotation",2013,"10.1002/grl.50841","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84883450968&doi=10.1002%2fgrl.50841&partnerID=40&md5=2cb443a6acda39c1feb12f3409e79509","The centrifugal force associated with the superrotation in Venus' and Titan's middle atmosphere reduces the effective gravity and thereby modifies the shape of the geopotential surface, which manifests itself as an equatorial bulge. General circulation models (GCMs) based on the hydrostatic primitive equations cannot correctly represent this dynamics since the vertical component of the centrifugal force does not appear in the hydrostatic equation. Consequently, they are likely to underestimate the poleward pressure gradient force and superrotation in gradient wind balance. This effect can be accounted for in nonhydrostatic GCMs or in quasi-hydrostatic GCMs, in which the hydrostatic equation is supplemented by the vertical component of the centrifugal and Coriolis force and which do not make the shallow-atmosphere approximation. A quasi-hydrostatic GCM is shown to predict faster superrotation than a hydrostatic GCM run under otherwise identical conditions. Key Points Superrotation in Venus' and Titan's atmosphere causes an equatorial bulge Hydrostatic GCMs cannot represent it unless the equations are corrected Superrotation becomes stronger if this effect is taken into account in the GCM ©2013. American Geophysical Union. All Rights Reserved."
"7004069241;55394412800;7003595038;","Analysis of a mixed finite-element pair proposed for an atmospheric dynamical core",2013,"10.1002/qj.2028","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880702584&doi=10.1002%2fqj.2028&partnerID=40&md5=48f72031f8e456bbc3a5b1209f8f65b9","We present a numerical dispersion analysis for the P2 - P1DG finite-element pair applied to the linear shallow-water equations in one dimension. The aim is to provide insight into the numerical dispersion properties of the RT1 and BDFM1 finite-element pairs in two dimensions, which have recently been proposed for horizontal discretisations of atmospheric dynamical cores with quasi-uniform grids. This is achieved via analysis of a one-dimensional RT1 element. Whilst these finite-element pairs have been shown to have many desirable properties that extend properties of the C grid to non-orthogonal quadrilateral and triangular grids, including stationary geostrophic modes on the f plane, and a 2:1 ratio of velocity to pressure degrees of freedom (a necessary condition for the absence of spurious mode branches), it is also important to have appropriately physical numerical wave propagation. In the absence of Coriolis force, we compute the group velocity for P2 - P1DG. We find that, as well as dropping to zero at the grid-scale, which also occurs for the C-grid finite-difference method, the group velocity also drops to zero in a narrow band around kh = π which corresponds to eigenmodes with a wavelength close to two element widths. This is a potential problem because it increases the amount of wavenumber space that needs to be filtered. In this one-dimensional case, we find that this particular issue can be removed by a small modification of the equations, namely partially lumping the mass matrix, in such a way that the other favourable properties of the scheme are not affected. We discuss various symmetric and asymmetric modifications of the mass matrix, and show that both such modifications preserve energy conservation (having modified the definition of discrete kinetic energy). Finally we illustrate our findings with numerical experiments, and discuss the potential to extend this modification to two-dimensional schemes. © 2012 Royal Meteorological Society and British Crown Copyright, the Met Office."
"26665643500;23082420800;7006256622;7003922138;42661269900;","Precessional cycles and their influence on the north pacific and north atlantic summer anticyclones",2013,"10.1175/JCLI-D-12-00343.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880664044&doi=10.1175%2fJCLI-D-12-00343.1&partnerID=40&md5=c5aeee2c4e4172f6421e1f903f9d336e","The response of the Northern Hemisphere summer anticyclones to a change in the timing of perihelion is investigated using the GFDL Climate Model version 2.1 (CM2.1). The orbital forcing consists of changes in the seasonal cycle of the top-of-atmosphere insolation as the perihelion shifts from the Northern Hemisphere winter to the Northern Hemisphere summer solstice. The North Pacific summer anticyclone experiences a large strengthening as well as a northward and westward expansion. The North Atlantic subtropical high experiences a smaller change that consists of a slight westward expansion but little change in strength. Experiments with a primitive equation atmospheric model show that these changes represent the circulation response to changes in the diabatic heating, both local and remotely. The remote diabatic forcing is associated with changes in the Southeast Asian and African summer monsoons, and the local forcing is dominated by a combined effect of a change in low clouds and local precipitation. © 2013 American Meteorological Society."
"36120812600;56178572000;7402583785;21234333100;7102595308;55800591500;","Momentum budget of the migrating diurnal tide in the Whole Atmosphere Community Climate Model at vernal equinox",2012,"10.1029/2011JD017089","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859918792&doi=10.1029%2f2011JD017089&partnerID=40&md5=8ec6e5ff30f0c83b4dd001d47ef898d4","The momentum budget of the migrating diurnal tide (DW1) at the vernal equinox is studied using the Whole Atmosphere Community Climate Model, version 4 (WACCM4). Classical tidal theory provides an appropriate first-order prediction of the DW1 structure, while gravity wave (GW) forcing and advection are the two most dominant terms in the momentum equation that account for the discrepancies between classical tidal theory and the calculation based on the full primitive equations. It differs from the conclusion by McLandress (2002a) that the parameterized GW effect is substantially weaker than advection terms based on the Canadian Middle Atmosphere Model (CMAM). In the region where DW1 maintains a large amplitude, GW forcing in the wave breaking region always damps DW1 and advances its phase. The linear advection largely determined by the latitudinal shear of the zonal mean zonal wind makes a dominant contribution to the phase change of DW1 in the zonal wind compared to the GW forcing and nonlinear advection. However, nonlinear advection is more important than GW forcing and linear advection in modulating the amplitude and phase of DW1 in the meridional wind. The DW1 amplitudes in temperature and winds are smaller than the TIMED observations, suggesting that GW forcing is overestimated in the WACCM4 and results in a large damping of DW1. Copyright 2012 by the American Geophysical Union."
"23019516000;14010178500;7403206351;7801525210;","The influence of lateral mixing on a phytoplankton bloom: Distribution in the Kerguelen Plateau region",2009,"10.1016/j.dsr.2008.12.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349148267&doi=10.1016%2fj.dsr.2008.12.018&partnerID=40&md5=88db26cef37e6584b8a26b89e95b4971","A unique phytoplankton bloom appears every year during the austral spring/summer in the northern Kerguelen Plateau region. The Kerguelen Ocean and Plateau compared Study (KEOPS) showed that an increase in subsurface iron coming up from the seafloor through vertical mixing was responsible for the observed increase in chlorophyll-a above the plateau. We demonstrate that the bloom pattern is not a simple increase of biomass over shallow water: it is strongly influenced by the bathymetry and its spatial extent controlled by strong currents around the plateau. Here we focus on lateral mixing process to explain the particular shape of the bloom. We use the Smagorinsky [1963. General circulation experiments with the primitive equations. I. The basic experiment. Monthly Weather Review 91 (3), 99-164] formula to estimate and map fields of lateral mixing time scales (τ) due to barotropic tidal currents, barotropic atmospheric forced currents, Ekman velocities and geostrophic velocities. Results show that short time scale mixing is strongly influenced by the tides while the other processes have minor influences. Comparisons of τ and satellite chlorophyll-a images show that the spatial pattern of the bloom seems to be delimited by a barrier of high lateral mixing that is essentially due to tides. This emphasises the role played by the tides over the Kerguelen Plateau in supplying iron to the phytoplankton and containing the horizontal shape of the bloom. This is one of the first times such a link has been demonstrated, which has implications for the study of iron advection in the ocean. © 2009 Elsevier Ltd. All rights reserved."
"7101716599;35209683700;","Diagnostic and dynamical analyses of two outstanding aspects of storm tracks",2007,"10.1016/j.dynatmoce.2006.06.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847615257&doi=10.1016%2fj.dynatmoce.2006.06.004&partnerID=40&md5=48e4fe2aa0211654cbd56fa105955e75","This paper reports diagnostic and dynamical analyses about two aspects of winter storm tracks in Northern Hemisphere. It is first established with NCEP/NCAR reanalysis data that the Atlantic storm track is distinctly more intense than the Pacific storm track in 30 out of 40 winters even though the Atlantic jet is considerably weaker and that the intensity of the two storm tracks are positively correlated. It is hypothesized that the continent-ocean configuration, in conjunction with the related differential friction, could be a significant contributing factor to such relative intensity. Supporting evidence for this hypothesis is presented in the context of a quasi-geostrophic two-level model analysis. We also establish that the intensity of the Pacific storm track is a minimum in mid-winter (MWMIN) in 21 of 40 winters, whereas in contrast the Atlantic storm track is most intense in mid-winter (MWMAX) in 25 of 40 winters. The structural characteristics of the composite mean flows as well as the energetics in MWMIN and MWMAX are compared. It is hypothesized that a significant enhancement of barotropic damping relative to the baroclinic growth in mid-winter is a major contributing factor to the occurrence of MWMIN. Supporting evidence for this hypothesis is presented from another idealized model analysis. Successful simulation of MWMIN can be made in a global spherical multi-level primitive equation model only if the proxy forcing is enhanced in early winter. However, the model still captures the difference between MWMIN and MWMAX even without using such enhanced forcing. The major caveat of this study is that moist dynamics has not been taken into consideration. © 2006 Elsevier B.V. All rights reserved."
"7004427982;45761547800;6701357023;7401993654;","Climate modeling with spectral elements",2006,"10.1175/MWR3360.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846222367&doi=10.1175%2fMWR3360.1&partnerID=40&md5=eb0db9c0d2d155459c655928aef78914","As an effort toward improving climate model component performance and accuracy, an atmospheric-component climate model has been developed, entitled the Spectral Element Atmospheric Climate Model and denoted as CAM_SEM. CAM_SEM includes a unique dynamical core coupled at this time to the physics component of the Community Atmosphere Model (CAM) as well as the Community Land Model. This model allows the inclusion of local mesh refinement to seamlessly study imbedded higher-resolution regional climate concurrently with the global climate. Additionally, the numerical structure of the model based on spectral elements allows for application of state-of-the-art computing hardware most effectively and economically to produce the best prediction/simulation results with minimal expenditure of computing resources. The model has been tested under various conditions beginning with the shallow water equations and ending with an Atmospheric Model Intercomparison Project (AMIP)-style run that uses initial conditions and physics comparable to the CAM2 (version 2 of the NCAR CAM climate model) experiments. For uniform resolution, the output of the model compares favorably with the published output from the CAM2 experiments. Further integrations with local mesh refinement included indicate that while greater detail in the prediction of mesh-refined regions - that is, regional climate - is observed, the remaining coarse-grid results are similar to results obtained from a uniform-grid integration of the model with identical conditions. It should be noted that in addition to spectral elements, other efficient schemes have lately been considered, in particular the finite-volume scheme. This scheme has not yet been incorporated into CAM_SEM. The two schemes - finite volume and spectral element - are quasi-independent and generally compatible, dealing with different aspects of the integration process. Their impact can be assessed separately and the omission of the finite-volume process herein will not detract from the evaluation of the results using the spectral-element method alone. © 2006 American Meteorological Society."
"7201439545;","On the accuracy of the semi-geostrophic approximation",2000,"10.1256/smsqj.56412","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034077027&doi=10.1256%2fsmsqj.56412&partnerID=40&md5=8b9e86361361c6c1ec6c4eede29a596f","The semi-geostrophic model has been widely used to understand atmospheric flows such as fronts and developing cyclones. However, there have been a number of demonstrations of its lack of accuracy. This paper presents theory and computations to demonstrate that the semi-geostrophic model is an accurate approximation to the primitive equations either on horizontal scales larger than the Rossby radius of deformation or when the ratio of horizontal to vertical scales is greater than f/N."
"57217432162;7406589460;6602486985;57213319039;","Jetlet formation from diabatic forcing with applications to the 1994 Palm Sunday tornado outbreak",1998,"10.1175/1520-0493(1998)126<2061:JFFDFW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032450375&doi=10.1175%2f1520-0493%281998%29126%3c2061%3aJFFDFW%3e2.0.CO%3b2&partnerID=40&md5=bf208ec482034929ec6c36ae39c9e923","The three-dimensional responses of simple stably stratified barotropic and baroclinic flows to prescribed diabatic forcing are investigated using a dry, hydrostatic, primitive equation numerical model (the North Carolina State University Geophysical Fluid Dynamics Model). A time-dependent diabatic forcing is utilized to isolate the effects of latent heat release in a midlatitude convective system. Examination of the mass-momentum adjustments to the diabatic forcing is performed with a focus on the development of an isolated midlevel wind maximum. The results of both cases suggest the formation of a midlevel wind maximum in the form of a perturbation meso-β-scale cyclone, which later propagates downstream as the heating is decreased. The scale of the perturbation cyclone remains at a sub-Rossby radius of deformation length scale. Therefore, the mass perturbations adjust to the wind perturbations as the mesocyclone propagates downstream. Transverse vertical circulations, which favor ascent on the right flank of the wind maximum, appear to be attributed to compensatory gravity wave motions, initially triggered by the thermal forcing, which laterally disperses as the heating is reduced. The simple model simulations are used to explain more complex results from a previous mesoscale modeling study (the Mesoscale Atmospheric Simulation System, MASS), in which it was hypothesized that an upstream mesoscale convective complex triggered a midlevel jetlet through geostrophic adjustment of the wind to the latent heat source. The MASS simulated jetlet attained a transverse vertical circulation that favored ascent on the right flank of the midlevel jetlet. The jetlet and accompanying transverse vertical circulations later propagated downstream aiding in the formation of the 27-28 March 1994 tornadic environment in Alabama and Georgia."
"7004544454;7409819344;6603894240;6701803136;7404936842;","Parallelization and distribution of a coupled atmosphere-ocean general circulation model",1993,"10.1175/1520-0493(1993)121<2062:PADOAC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027868988&doi=10.1175%2f1520-0493%281993%29121%3c2062%3aPADOAC%3e2.0.CO%3b2&partnerID=40&md5=0c3a7e522f4c6f490f0d731cf8e5a89c","First, the domains of both the gridpoint AGCM and OGCM are divided into subdomains for which calculations are carried out concurrently (domain decomposition). Second, the model is decomposed based on the diversity of tasks performed by its major components (task decomposition). Three such components are identified: a) AGCM/physics, which computes the effects on the grid-scale flow of subgrid-scale processes such as convection and turbulent mixing; b) AGCM/dynamics, which computes the evolution of the flow governed by the primitive equations; and c) the OGCM. Task decomposition allows the AGCM/dynamics and OGCM calculations to be carried out concurrently. Last, computation and communication are organized in such a way that the exchange of data between different tasks is carried out in subdomains of the model domain (I/O decomposition). In a dedicated computer network environment, the wall-clock time required by the resulting distributed application is reduced to that for the AGCM/physics, with the other two components and interprocess communications running in parallel. -from Authors"
"7202748672;","A comparison of primitive and balance equation simulations of baroclinic waves",1993,"10.1175/1520-0469(1993)050<1519:ACOPAB>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027795729&doi=10.1175%2f1520-0469%281993%29050%3c1519%3aACOPAB%3e2.0.CO%3b2&partnerID=40&md5=6d5ec1906f4f44ba262cc1510efed93b","The balance equations are an approximate set of equations that reduce to gradient wind balance under steady, circular flow conditions on an f plane. Scale analysis indicates that these equations are potentially quite accurate over a wide variety of atmospheric conditions. Motivated by an apparent lack of numerical solutions of this set, we compare simulations of nonlinear baroclinic waves under adiabatic conditions with the primitive and balance equations. As predicted by the scale analysis, the balance equations describe the wave evolution with very high accuracy in situations where the errors made by approximate equation sets based on geostrophy are significant. -Author"
"7102367341;7101630970;","Some comparisons of atmospheric internal and boundary baroclinic instability.",1985,"10.1175/1520-0469(1985)042<2142:SCOAIA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022266330&doi=10.1175%2f1520-0469%281985%29042%3c2142%3aSCOAIA%3e2.0.CO%3b2&partnerID=40&md5=afd5192d27d0b600c81727c3b0dcddbf","The existence of boundary baroclinic instability (as exemplified by the Eady or Charney problems) and internal baroclinic instability, which requires the potential vorticity gradient to take both signs in the fluid interior, is unified by regarding the boundary temperature gradients in the external problem as equivalent to infinitely thin sheets of non-zero potential vorticity gradient. It is shown that this analogy can be generalized from the quasi-geostrophic to the primitive equation systems. The linear instability problem on the sphere is examined using the primitive equations; the results are consistent with those of simple conceptual models where potential vorticity gradients are concentrated in thin sheets. The normal modes are integrated into the nonlinear regime, and it is shown that the low-level potential vorticity gradients evolve in a similar way to the surface temperature fields in the lifecycles of external modes. Frontal structures are absent, though the enstrophy cascade produces narrow, elongated low-level features around the time of maximum wave activity. Finally, a lifecycle for a boundary unstable flow is compared with that for an initial flow.-from Authors"
"57193791961;16837735900;7005911418;","WRF hub-height wind forecast sensitivity to PBL scheme, grid length, and initial condition choice in complex terrain",2017,"10.1175/WAF-D-16-0120.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016633390&doi=10.1175%2fWAF-D-16-0120.1&partnerID=40&md5=fc63f81eebef49afcc8f86c237b7838c","This study evaluates the sensitivity of wind turbine hub-height wind speed forecasts to the planetary boundary layer (PBL) scheme, grid length, and initial condition selection in the Weather Research and Forecasting (WRF) Model over complex terrain. Eight PBL schemes available for the WRF-ARW dynamical core were tested with initial conditions sources from the North American Mesoscale (NAM) model and Global Forecast System (GFS) to produce short-term wind speed forecasts. The largest improvements in forecast accuracy primarily depended on the grid length or PBL scheme choice, although the most important factor varied by location, season, time of day, and bias-correction application. Aggregated over all locations, the Asymmetric Convective Model, version 2 (ACM2) PBL scheme provided the best forecast accuracy, particularly for the 12-km grid length. Other PBL schemes and grid lengths, however, did perform better than the ACM2 scheme for individual seasons or locations. © 2017 American Meteorological Society."
"57193630037;7005561589;7201746369;55716319700;","The dynamics of the extratropical response to Madden–Julian Oscillation convection",2017,"10.1002/qj.2993","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015264200&doi=10.1002%2fqj.2993&partnerID=40&md5=b999cd14feebffdadb34b32f5ba991bd","The Rossby wave source (RWS) and the corresponding extratropical wave response to tropical convection associated with different phases of the Madden–Julian Oscillation (MJO) is investigated with the dynamical core of a climate model. The initial flow is specified to correspond to the boreal winter climatological flow and an imposed tropical heating that is derived from the observed precipitation for all eight MJO phases. One key question addressed here is why does the extratropical Rossby wave train depart the subtropics at a longitude well to the east of the RWS. For all eight MJO phases, it is found that the extratropical response over the North Pacific and North America is almost entirely due to the MJO convection over the western tropical Pacific. The RWS is excited within the first 24 h after the model heating is turned on. For MJO phases 1–3 and 8, the RWS leads to the development of a cyclonic anomaly over southeast Asia via advection of the climatological absolute vorticity by the anomalous divergent wind in the subtropics and by horizontal convergence in the Tropics. MJO phases 4–7 show opposite features. The resulting anomaly is then advected eastward by the climatological zonal wind toward the central Pacific, after which dispersion into the extratropics and the excitation of a Pacific/North American teleconnection pattern takes place. © 2016 Royal Meteorological Society"
"55829903800;7005702722;","The linear response function of an idealized atmosphere. Part I: Construction using green's functions and applications",2016,"10.1175/JAS-D-15-0338.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988407819&doi=10.1175%2fJAS-D-15-0338.1&partnerID=40&md5=b5d74448e1a5820d134d0da2adc41d66","A linear response function (LRF) determines the mean response of a nonlinear climate system to weak imposed forcings, and an eddy flux matrix (EFM) determines the eddy momentum and heat flux responses to mean-flow changes. Neither LRF nor EFM can be calculated from first principles owing to the lack of a complete theory for turbulent eddies. Here the LRF and EFM for an idealized dry atmosphere are computed by applying numerous localized weak forcings, one at a time, to a GCM with Held-Suarez physics and calculating the mean responses. The LRF and EFM for zonally averaged responses are then constructed using these forcings and responses through matrix inversion. Tests demonstrate that LRF and EFM are fairly accurate. Spectral analysis of the LRF shows that the most excitable dynamical mode, the neutral vector, strongly resembles the model's annular mode. The framework described here can be employed to compute the LRF and EFM for zonally asymmetric responses and more complex GCMs. The potential applications of the LRF and EFM constructed here are (i) forcing a specified mean flow for hypothesis testing, (ii) isolating/quantifying the eddy feedbacks in complex eddy-mean flow interaction problems, and (iii) evaluating/improving more generally applicable methods currently used to construct LRFs or diagnose eddy feedbacks in comprehensive GCMs or observations. As an example for (iii), in Part II, the LRF is also computed using the fluctuation-dissipation theorem (FDT), and the previously calculated LRF is exploited to investigate why FDT performs poorly in some cases. It is shown that dimension reduction using leading EOFs, which is commonly used to construct LRFs from the FDT, can significantly degrade the accuracy owing to the nonnormality of the operator. © 2016 American Meteorological Society."
"55764437400;6602755372;26643546500;56850959100;55541588900;6507341071;7201914891;","Submesoscale water-mass spectra in the Sargasso sea",2015,"10.1175/JPO-D-14-0108.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942902329&doi=10.1175%2fJPO-D-14-0108.1&partnerID=40&md5=0cb1470bdc0792bae3aadd1855d6088f","Submesoscale stirring contributes to the cascade of tracer variance from large to small scales. Multiple nested surveys in the summer Sargasso Sea with tow-yo and autonomous platforms captured submesoscale water-mass variability in the seasonal pycnocline at 20-60-m depths. To filter out internal waves that dominate dynamic signals on these scales, spectra for salinity anomalies on isopycnals were formed. Salinity-gradient spectra are approximately flat with slopes of -0.2 ± 0.2 over horizontal wavelengths of 0.03-10 km. While the two to three realizations presented here might be biased, more representative measurements in the literature are consistent with a nearly flat submesoscale passive tracer gradient spectrum for horizontal wavelengths in excess of 1 km. A review of mechanisms that could be responsible for a flat passive tracer gradient spectrum rules out (i) quasigeostrophic eddy stirring, (ii) atmospheric forcing through a relict submesoscale winter mixed layer structure or nocturnal mixed layer deepening, (iii) a downscale vortical-mode cascade, and (iv) horizontal diffusion because of shear dispersion of diapycnal mixing. Internal-wave horizontal strain appears to be able to explain horizontal wavenumbers of 0.1-7 cycles per kilometer (cpkm) but not the highest resolved wavenumbers (7-30 cpkm). Submesoscale subduction cannot be ruled out at these depths, though previous observations observe a flat spectrum well below subduction depths, so this seems unlikely. Primitive equation numerical modeling suggests that nonquasigeostrophic subinertial horizontal stirring can produce a flat spectrum. The last need not be limited to mode-one interior or surface Rossby wavenumbers of quasigeostrophic theory but may have a broaderband spectrum extending to smaller horizontal scales associated with frontogenesis and frontal instabilities as well as internal waves. © 2015 American Meteorological Society."
"6507190607;7004178217;6603062918;","Connecting the dots: A versatile model for the atmospheres of tidally locked super-earths",2014,"10.1093/mnras/stu1793","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84913615107&doi=10.1093%2fmnras%2fstu1793&partnerID=40&md5=8a8225e7c034be19c6af3af76b3d8c6c","Radiative equilibrium temperatures are calculated for the troposphere of a tidally locked Super-Earth based on a simple greenhouse model, using Solar system data as a guideline. These temperatures provide in combination with a Newtonian relaxation scheme thermal forcing for a 3D atmosphere model using the dynamical core of the Massachusetts Institute of Technology global circulation model. Our model is of the same conceptional simplicity than the model of Held &amp; Suarez and is thus computationally fast. Furthermore, because of the coherent, general derivation of radiative equilibrium temperatures, our model is easily adaptable for different planets and atmospheric scenarios. As a case study relevant for Super-Earths, we investigate a Gl581g-like planet with Earth-like atmosphere and irradiation and present results for two representative rotation periods of Prot = 10 d and Prot = 36.5 d. Our results provide proof of concept and highlight interesting dynamical features for the rotating regime 3 &lt; Prot &lt; 100 d, which was shown by Edson et al. to be an intermediate regime between equatorial superrotation and divergence. We confirm that the Prot = 10 d case is more dominated by equatorial superrotation dynamics than the Prot = 36.5 d case, which shows diminishing influence of standing Rossby-Kelvin waves and increasing influence of divergence at the top of the atmosphere.We argue that this dynamical regime change relates to the increase in Rossby deformation radius, in agreement with previous studies. However, we also pay attention to other features that are not or only in partial agreement with other studies, like, e.g. the number of circulation cells and their strength, the role and extent of thermal inversion layers, and the details of heat transport. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society."
"57030797300;23045565900;","Effective isentropic diffusivity of tropospheric transport",2014,"10.1175/JAS-D-13-0333.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84906751205&doi=10.1175%2fJAS-D-13-0333.1&partnerID=40&md5=aec70975a52aa777a3fbdcb533a9a0c8","Tropospheric transport can be described qualitatively by the slow mean diabatic circulation and rapid isentropic mixing, yet a quantitative understanding of the transport circulation is complicated, as nearly half of the isentropic surfaces in the troposphere frequently intersect the ground.A theoretical framework for the effective isentropic diffusivity of tropospheric transport is presented. Compared with previous isentropic analysis of effective diffusivity, a new diagnostic is introduced to quantify the eddy diffusivity of the nearsurface isentropic flow. This diagnostic also links the effective eddy diffusivity directly to a diffusive closure of eddy fluxes through a finite-amplitude wave activity equation. The theory is examined in a dry primitive equation model on the sphere. It is found that the upper troposphere is characterized by a diffusivity minimum at the jet's center with enhanced mixing at the jet's flanks and that the lower troposphere is dominated by stronger mixing throughout the baroclinic zone. This structure of isentropic diffusivity is generally consistent with the diffusivity obtained from the geostrophic component of the flow. Furthermore, the isentropic diffusivity agrees broadly with the tracer equivalent length obtained from either a spectral diffusion scheme or a semi-Lagrangian advection scheme, indicating that the effective diffusivity of tropospheric transport is largely dictated by large-scale stirring rather than details of the smallscale diffusion acting on the tracers. © 2014 American Meteorological Society."
"14058428800;6506539438;7003991093;","Maintenance of the stratospheric structure in an idealized general circulation model",2013,"10.1175/JAS-D-12-0305.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888019001&doi=10.1175%2fJAS-D-12-0305.1&partnerID=40&md5=b3a7034a240018120c5be43f50c2a4d1","This work explores the maintenance of the stratospheric structure in a primitive equation model that is forced by a Newtonian cooling with a prescribed radiative equilibrium temperature field. Models such as this are well suited to analyze and address questions regarding the nature of wave propagation and troposphere- stratosphere interactions. The focus lies on the lower to midstratosphere and the mean annual cycle, with its large interhemispheric variations in the radiative background state and forcing, is taken as a benchmark to be simulated with reasonable verisimilitude. A reasonably realistic basic stratospheric temperature structure is a necessary first step in understanding stratospheric dynamics. It is first shown that using a realistic radiative background temperature field based on radiative transfer calculations substantially improves the basic structure of the model stratosphere compared to previously used setups. Then, the physical processes that are needed to maintain the seasonal cycle of temperature in the lower stratosphere are explored. It is found that an improved stratosphere and seasonally varying topographically forced stationary waves are, in themselves, insufficient to produce a seasonal cycle of sufficient amplitude in the tropics, even if the topographic forcing is large. Upwelling associated with baroclinic wave activity is an important influence on the tropical lower stratosphere and the seasonal variation of tropospheric baroclinic activity contributes significantly to the seasonal cycle of the lower tropical stratosphere. Given a reasonably realistic basic stratospheric structure and a seasonal cycle in both stationary wave activity and tropospheric baroclinic instability, it is possible to obtain a seasonal cycle in the lower stratosphere of amplitude comparable to the observations. © 2013 American Meteorological Society."
"36061723700;7103293551;56011471100;6603854214;16316745800;","Physical characteristics and dynamics of the coastal Latex09 eddy derived from in situ data and numerical modeling",2013,"10.1029/2012JC008229","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878950015&doi=10.1029%2f2012JC008229&partnerID=40&md5=4726b3569c5628b8e594e878b238667b","[1] We investigate the dynamics of a coastal anticyclonic eddy in the western part of the Gulf of Lion (GoL) in the northwestern Mediterranean Sea during the Latex campaign in the summer 2009 (Latex09). The sampling strategy combines sea surface temperature satellite imagery, hull-mounted acoustic Doppler current profiler data, conductivity-temperature-depth casts, and drifter trajectories. Our measurements reveal an anticyclonic eddy (Latex09 eddy) with a diameter of ∼23 km and maximum depth of 31m, centered at 3°34'E, 42°33'N. We use a high resolution, three-dimensional, primitive equation numerical model to investigate its generation process and evolution. The model is able to reproduce the observed eddy, in particular its size and position. The model results suggest that the Latex09 eddy is induced by a large anticyclonic circulation in the northwestern part of the GoL, pushed and squeezed toward the coast by a meander of the Northern Current. This represents a new generation mechanism that has not been reported before. The post generation dynamics of the eddy is also captured by the model. The collision of the Latex09 eddy with Cape Creus results in a transient structure, which is depicted by the trajectories of two Lagrangian drifters during Latex09. The transient structure and its advection lead to a transfer of mass and vorticity from the GoL to the Catalan shelf, indicating the importance of mesoscale structures in modulating such exchanges in the region. © 2012. American Geophysical Union. All Rights Reserved."
"36054921000;8558370300;7004060399;","Abrupt circulation responses to tropical upper-tropospheric warming in a relatively simple stratosphere-resolving AGCM",2012,"10.1175/JCLI-D-11-00166.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865161418&doi=10.1175%2fJCLI-D-11-00166.1&partnerID=40&md5=14197286fa47044e7b14e45c7bf6c85d","The circulation response of the atmosphere to climate change-like thermal forcing is explored with a relatively simple, stratosphere-resolving general circulation model. The model is forced with highly idealized physics, but integrates the primitive equations at resolution comparable to comprehensive climate models. An imposed forcing mimics the warming induced by greenhouse gasses in the low-latitude upper troposphere. The forcing amplitude is progressively increased over a range comparable in magnitude to the warming projected by Intergovernmental Panel on Climate Change coupled climate model scenarios. For weak to moderate warming, the circulation response is remarkably similar to that found in comprehensive models: the Hadley cell widens and weakens, the tropospheric midlatitude jets shift poleward, and the Brewer-Dobson circulation (BDC) increases. However, when the warming of the tropical upper troposphere exceeds a critical threshold,;5K, an abrupt change of the atmospheric circulation is observed. In the troposphere the extratropical eddy-driven jet jumps poleward nearly 108. In the stratosphere the polar vortex intensifies and the BDC weakens as the intraseasonal coupling between the troposphere and the stratosphere shuts down. The key result of this study is that an abrupt climate transition can be effected by changes in atmospheric dynamics alone, without need for the strong nonlinearities typically associated with physical parameterizations. It is verified that the abrupt climate shift reported here is not an artifact of the model's resolution or numerics. © 2012 American Meteorological Society."
"6506965119;36460220700;7003630013;","Direct numerical simulation of the turbulent Ekman layer: Evaluation of closure models",2012,"10.1175/JAS-D-11-0107.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84858214773&doi=10.1175%2fJAS-D-11-0107.1&partnerID=40&md5=f6253963f233a45ee28ff61ed1ce9bb5","A direct numerical simulation (DNS) at a Reynolds number of 1000 was performed for the neutral atmospheric boundary layer (ABL) using the Ekman layer approximation. The DNS results were used to evaluate several closure approximations that model the turbulent stresses in the Reynolds averaged momentum equations. Two first-order closure equations proposed by O'Brien and by Large, McWilliams, and Doney were tested; both models approximate the eddy diffusivity as a function of height using cubic polynomials. Of these two models, the O'Brien model, which requires data both at the surface layer and at the top of the boundary layer, proved superior. The higher-order k-« model also agreed well with DNS results and more accurately represented the eddy diffusivity in this rotational flow. © 2012 American Meteorological Society."
"14820677200;57213319039;15137624600;7101699632;7102331727;7201847605;","Dust storm over the Black Rock Desert: Larger-scale dynamic signatures",2011,"10.1029/2010JD014784","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953239494&doi=10.1029%2f2010JD014784&partnerID=40&md5=b2a75a7c6b7d3d4e7a24da055a39ce9e","A dust storm that originated over the Black Rock Desert (BRD) of northwestern Nevada is investigated. Our primary goal is to more clearly understand the sequence of dynamical processes that generate surface winds responsible for entraining dust from this desert. In addition to reliance on conventional surface and upper-air observations, we make use of reanalysis data sets (NCAR/NCEP and NARR) - blends of primitive equation model forecasts and observations. From these data sets, we obtain the evolution of vertical motion patterns and ageostrophic motions associated with the event. In contrast to earlier studies that have emphasized the importance of indirect transverse circulations about an upper-level jet streak, our results indicate that in this case the transition from an indirect to a direct circulation pattern across the exit region of upper-level jet streak is central to creation of low-level winds that ablate dust from the desert. It is further argued that the transition of vertical circulation patterns is in response to adjustments to geostrophic imbalance - an adjustment time scale of 6-9 h. Although unproven, we suggest that antecedent rainfall over the alkali desert 2 weeks prior to the event was instrumental in lowering the bulk density of sediments and thereby improved the chances for dust ablation by the atmospheric disturbance. We comprehensively compare/contrast our results with those of earlier investigators, and we present an alternative view of key dynamical signatures in atmospheric flow that portend the likelihood of dust storms over the western United States. Copyright 2011 by the American Geophysical Union."
"23485410200;7202676587;7404187480;6603821988;35573051400;","Using different formulations of the transformed Eulerian mean equations and Eliassen-Palm diagnostics in general circulation models",2010,"10.1175/2010JAS3355.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955541791&doi=10.1175%2f2010JAS3355.1&partnerID=40&md5=960f19c7e177eebe2c747e181169d1b6","Transformed Eulerian mean (TEM) equations and Eliassen-Palm (EP) flux diagnostics are presented for the general nonhydrostatic, fully compressible, deep atmosphere formulation of the primitive equations in spherical geometric coordinates. The TEM equations are applied to a general circulation model (GCM) based on these general primitive equations. It is demonstrated that a naive application in this model of the widely used approximations to the EP diagnostics, valid for the hydrostatic primitive equations using log-pressure as a vertical coordinate and presented, for example, by Andrews et al. in 1987 can lead to misleading features in these diagnostics. These features can be of the same order of magnitude as the diagnostics themselves throughout the winter stratosphere. Similar conclusions are found to hold for ""downward control"" calculations. The reasons are traced to the change of vertical coordinate from geometric height to log-pressure. Implications for the modeling community, including comparison of model output with that from reanalysis products available only on pressure surfaces, are discussed. © 2010 American Meteorological Society."
"7402435469;57212416832;15765007300;","Two dynamical core formulation flaws exposed by a baroclinic instability test case",2009,"10.1175/2008MWR2587.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249158190&doi=10.1175%2f2008MWR2587.1&partnerID=40&md5=2f267342596fc3c4e8e0a9292db63333","Two flaws in the semi-Lagrangian algorithm originally implemented as an optional dynamical core in the NCAR Community Atmosphere Model (CAM3.1) are exposed by steady-state and baroclinic instability test cases. Remedies are demonstrated and have been incorporated in the dynamical core. One consequence of the first flaw is an erroneous damping of the speed of a zonally uniform zonal wind undergoing advection by a zonally uniform zonal flow field. It results from projecting the transported vector wind expressed in unit vectors at the arrival point to the surface of the sphere and is eliminated by rotating the vector to be parallel to the surface. The second flaw is the formulation of an a posteriori energy fixer that, although small, systematically affects the temperature field and leads to an incorrect evolution of the growing baroclinic wave. That fixer restores the total energy at each time step by changing the provisional forecast temperature proportionally to the magnitude of the temperature change at that time step. Two other fixers are introduced that do not exhibit the flaw. One changes the provisional temperature everywhere by an additive constant, and the other changes it proportionally by a multiplicative constant. © 2009 American Meteorological Society."
"8618667100;6603137309;6701511841;7006718746;","Resonant wave interactions in the equatorial waveguide",2008,"10.1175/2008JAS2387.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049111138&doi=10.1175%2f2008JAS2387.1&partnerID=40&md5=c1fe28ad52580a12018b45a066c5f0ff","Weakly nonlinear interactions among equatorial waves have been explored in this paper using the adiabatic version of the equatorial β-plane primitive equations in isobaric coordinates. Assuming rigid lid vertical boundary conditions, the conditions imposed at the surface and at the top of the troposphere were expanded in a Taylor series around two isobaric surfaces in an approach similar to that used in the theory of surface-gravity waves in deep water and capillary-gravity waves. By adopting the asymptotic method of multiple time scales, the equatorial Rossby, mixed Rossby-gravity, inertio-gravity, and Kelvin waves, as well as their vertical structures, were obtained as leading-order solutions. These waves were shown to interact resonantly in a triad configuration at the O(ε) approximation. The resonant triads whose wave components satisfy a resonance condition for their vertical structures were found to have the most significant interactions, although this condition is not excluding, unlike the resonant conditions for the zonal wavenumbers and meridional modes. Thus, the analysis has focused on such resonant triads. In general, it was found that for these resonant triads satisfying the resonance condition in the vertical direction, the wave with the highest absolute frequency always acts as an energy source (or sink) for the remaining triad components, as usually occurs in several other physical problems in fluid dynamics. In addition, the zonally symmetric geostrophic modes act as catalyst modes for the energy exchanges between two dispersive waves in a resonant triad. The integration of the reduced asymptotic equations for a single resonant triad shows that, for the initial mode amplitudes characterizing realistic magnitudes of atmospheric flow perturbations, the modes in general exchange energy on low-frequency (intraseasonal and/or even longer) time scales, with the interaction period being dependent upon the initial mode amplitudes. Potential future applications of the present theory to the real atmosphere with the inclusion of diabatic forcing, dissipation, and a more realistic background state are also discussed. © 2008 American Meteorological Society."
"6603906063;7202214528;35952114200;8585168600;6601976436;7003580674;7005997993;6507728383;","A forecast experiment in the Balearic Sea",2008,"10.1016/j.jmarsys.2007.05.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40649091411&doi=10.1016%2fj.jmarsys.2007.05.008&partnerID=40&md5=f2b78b70857d62f1a4784d7c5e9863be","A forecast experiment in the Balearic Sea is presented which is based on the Harvard Ocean Prediction System (HOPS). HOPS is modular, containing a high-resolution primitive equations model, packages for objective analysis and data assimilation (Optimum Interpolation), an interface to implement atmospheric forcing and another interface for one-way nesting of HOPS into any other larger-scale circulation model. Here, to prevent false advection from open boundaries, HOPS is nested into the basin-scale DieCAST model [Dietrich, D.E., Haney, R.L., Fernández, V., Josey, S.A., Tintoré, J., 2004. Air-sea fluxes based on observed annual cycle surface climatology and ocean model internal dynamics: a non-damping zero-phase-lag approach applied to the Mediterranean Sea. J. Mar. Syst., 52, 145-165] and atmospheric forcing fields were provided in terms of HIRLAM fields by the Spanish National Institute of Meteorology. The forecast capability of HOPS is demonstrated in terms of a hindcast experiment, utilising two observational data sets of a subregion of the Balearic Sea which were acquired in mid September and early October 2002. While the data of the first survey is used for model initialisation, that of the second survey serves for validation of the forecast products. The forecast skill of the system is evaluated quantitatively by three different objective methods, comparing the rms difference of vertical profiles and horizontal fields, and pattern correlations, both for temperature and salinity. In five out of six cases, the forecasted fields are closer to the validation data set than the fields used for initialisation, i.e. the forecast beats persistence and the forecast is successful. Taking into account further available options of HOPS (implementation of additional tracers, tracking of Lagrangian particles, biological modules, two-way nesting), the system is operational for a wide field of possible applications. © 2007 Elsevier B.V. All rights reserved."
"10042470700;7005087624;6701537033;7004687638;6506819877;7102450474;6507460574;7102696626;7006705919;","Evaluation of a CCSM3 simulation with a finite volume dynamical core for the atmosphere at 1° latitude × 1.25° longitude resolution",2008,"10.1175/2007JCLI2060.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44449101097&doi=10.1175%2f2007JCLI2060.1&partnerID=40&md5=ded0abc6f8b6830eeb3ea2ea359147bc","A simulation of the present-day climate by the Community Climate System Model version 3 (CCSM3) that uses a Finite Volume (FV) numerical method for solving the equations governing the atmospheric dynamics is presented. The simulation is compared to observations and to the well-documented simulation by the standard CCSM3, which uses the Eulerian spectral method for the atmospheric dynamics. The atmospheric component in the simulation herein uses a 1° latitude × 1.25° longitude grid, which is a slightly finer resolution than the T85-grid used in the spectral transform. As in the T85 simulation, the ocean and ice models use a nominal 1-degree grid. Although the physical parameterizations are the same and the resolution is comparable to the standard model, substantial testing and slight retuning were required to obtain an acceptable control simulation. There are significant improvements in the simulation of the surface wind stress and sea surface temperature. Improvements are also seen in the simulations of the total variance in the tropical Pacific, the spatial pattern of ice thickness distribution in the Arctic, and the vertically integrated ocean circulation in the Antarctic Circumpolar Current. The results herein demonstrate that the FV version of the CCSM coupled model is a state-of-the-art climate model whose simulation capabilities are in the class of those used for Intergovernmental Panel on Climate Change (IPCC) assessments. The simulated climate is very similar to that of the T85 version in terms of its biases, and more like the T85 model than the other IPCC models. © 2008 American Meteorological Society."
"14623355800;6701849971;7006550959;","Subscale forcing in a global atmospheric circulation model and stochastic parametrization",2006,"10.1256/qj.05.139","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33748790664&doi=10.1256%2fqj.05.139&partnerID=40&md5=975de42d3e0665a2e490166d8d222557","A global atmospheric circulation model is used to derive the properties of the subscale forcing in the primitive equations. The study is based on a simulation with the model PUMA (Portable University Model of the Atmosphere), which represents a dynamical core with linear diabatic heating and friction. The subscale forcing is determined for a low wave number resolution T21 (≈5° × 5°) embedded in T42 resolution (≈2.5° × 2.5°) using the differences between the low wave number filtered T42 model and the forcing by low wave numbers (T21). The mean subscale forcing vanishes (besides a small heating contribution). The variance has largest values in the midlatitudes for vorticity (mid-troposphere), temperature (lower troposphere), and in the polar mid-troposphere for divergence. The temporal correlations reveal a slow decay in the first few hours followed by an exponential decay with an e-folding time of about one day. The correlation with hyperdiffusion (∼∇8) is below 0.4. Based on these results the design of stochastic parametrizations is suggested. © Royal Meteorological Society, 2006."
"6701335353;7003665132;7404692349;","Reconstruction of summer Barents Sea circulation from climatological data",2006,"10.3137/ao.440201","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33745629352&doi=10.3137%2fao.440201&partnerID=40&md5=5deb29026c4eaa15346fcabc26068e43","An estimate of the summer Barents Sea circulation is constructed as a four-dimensional variational inverse of the monthly hydrographic and atmospheric climatologies. The reconstructed evolution of temperature, salinity, and velocity fields provides the best fit to climatological data and satisfies dynamical and kinematic constraints of a primitive equation ocean circulation model. The data-optimized Barents Sea state is in general agreement with the existing schemes of circulation in the region. The circulation is characterized by the 3.2 Sv inflow from the Norwegian Sea with the Norwegian Atlantic Current. Approximately 1.5 Sv of this inflow recirculates along the northern flank of Bear Island Trough, while the major branch of the current crosses the Barents Sea and outflows through Franz Josef Land - Novaya Zemliya and the Kara Gate straits with transports of 1.1 Sv and 0.6 Sv, respectively. The data assimilation reveals an eastward current between the Great and Central banks and cyclonic circulation in the region between Central Bank and Novaya Zemliya. These two circulation features have recently been confirmed in a number of publications. The reconstructed surface heat and salt fluxes are in qualitative and quantitative agreement with the known observational estimates. The posterior error analysis and sensitivity experiments provide additional arguments in support of the reliability of the data assimilation results. © Canadian Meteorological and Oceanographic Society."
"55469187200;","Jet sets",2003,"10.2151/jmsj.81.439","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0242658886&doi=10.2151%2fjmsj.81.439&partnerID=40&md5=3670e435708e39fe3f0342892826841c","To broaden the range of known circulations and to test existing theory, a variety of issues are examined concerning the dynamics of flows in thick, thin, and transitional atmospheric layers. The circulations are produced numerically using a primitive equation model subject to simple heating functions. To confine the motions to a thin upper layer, the heating is chosen to produce a flow with either an exponential (EXP) vertical structure, or one that is linear (LIN) aloft while vanishing below. Five sets of solutions are created to define the terrestrial and jovian axisymmetric states, some basic terrestrial states, and the transitional jovian states for the two structures. The axisymmetric cases examine how the surface drag, static stability, rotation rate, and layer thickness influence the flow character. The standard theory is extended to allow for a weaker drag and the solutions confirm that at lower rates the Hadley cells become wider, and the thermal fronts sharper and double. In the absence of any drag, the cells disappear and a thermal wind prevails globally. But in the absence of a background static stability, the cells become more intense and create their own stable temperature field. For normal parameter values, the Hadley cells adhere to the theoretical form as the rotation rate increases, except when their width falls below 3° of latitude. Furthermore, when the heated layer is thin and the jets are confined aloft, the cells develop vertically bimodal amplitudes, while remaining deep and exhibiting the usual widths. The basic 3-D terrestrial cases examine the role of the heating rate, static stability, surface drag, and rotation rate on the flow character. The mean jets exist within a limited latitudinal range, with their location being as much dependent on the heating amplitude as on the heating distribution. When the background static stability is absent, the standard circulation theory becomes less valid as the cells and baroclinic instability become more intense and act together to stabilize low and middle latitudes. However, when the drag is reduced, the baroclinic instability becomes much weaker and confined to lower levels because of suppression by the jet's stronger barotropic component. Other forms of baroclinic instability can be produced by creating double-jet flows, either by increasing the rotation rate or by adding an extra source of baroclinicity in low latitudes. The transitional jovian cases examine how the multiple jets behave as the active layer is varied between thick and thin for the LIN and EXP structures. In all cases, the jet widths remain constant with latitude, but their amplitudes vary, peaking either in low or middle latitudes depending on how the baroclinicity is distributed. An extra baroclinicity in low latitudes produces a jet whose barotropic instability can drive an equatorial superrotation, regardless of layer thickness. The eddy-driven jets have a similar dynamics for all layer thicknesses but, unlike the steady LIN jets, the EXP jets also migrate equatorward and, on rare occasions, poleward."
"55469187200;","Jovian dynamics. Part II: The genesis and equilibration of vortex sets",2002,"10.1175/1520-0469(2002)059<1356:JDPITG>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036090198&doi=10.1175%2f1520-0469%282002%29059%3c1356%3aJDPITG%3e2.0.CO%3b2&partnerID=40&md5=cec7e4abde96ed09c3e494a99768bf02","To extend studies of the dynamics of thin atmospheric layers, the generation and equilibration of multiple anticyclonic vortex sets associated with long solitary baroclinic Rossby waves are examined numerically using a primitive equation model with Jovian parameters subject to a simple heating function. The authors seek primarily to model the three main groups of anticyclones seen on Jupiter, namely, the Great Red Spot, the three White Ovals, and the dozen or so Small Ovals that occur at latitudes of -21°, -33°, and -41°, respectively. The motions are confined to thin upper layers by exponential vertical structures that favor absolute vortex stability. Calculations are also made to examine the regeneration, intrazonal and interscale interactions, and propagation rates of vortices. Vortex sets resembling the three main Jovian groups in scale, form, and number can be simultaneously generated and maintained in a steady configuration by a heating that produces stable westerly and weakly unstable easterly jets. The steady configuration occurs when an optimal number of vortices exists in a balance between a weak heating and a weak dissipation. Vortex behavior can be more complex in the heated system because the generation of new storms offsets the tendency to merge into fewer vortices. The solutions also show that intrazonal vertex interactions can lead, in some situations, to the destruction of anticyclones modeling the Great Red Spot."
"36102803900;","Transient sea-ice polynya forced by oceanic flow variability",2000,"10.1016/S0079-6611(01)00010-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034952470&doi=10.1016%2fS0079-6611%2801%2900010-6&partnerID=40&md5=ae883c75e98c31abb1ef97ae3a89ddc8","In the Weddell Sea during the winters of 1974-1976 a significant opening in the sea-ice cover occurred in the vicinity of a large bathymetric feature - the Maud Rise seamount. The event is commonly referred to as the Weddell Polynya. Aside from such a large-scale, relatively persistent polynya in the Weddell Sea, transient, small-scale polynya can also appear in the sea-ice cover at various times throughout the winter and at various locations with respect to the Maud Rise. The underlying causes for the occurrence of such transient polynya have not been unambiguously identified. We hypothesize that variations in the mean ocean currents are one major contributor to such variability in the sea-ice cover. Analysis of the sea-ice equations with certain idealized patterns of ocean currents serving as forcing is shown to lead to Ekman transports of sea ice favorable to the initiation of transient polynya. Aside from the actual spatial pattern of the idealized ocean currents, many other factors need also be taken into account when looking at such transient polynya. Two other such factors discussed are variations in the sea-ice thickness field and the treatment of the sea-ice rheology. Simulations of a sea-ice model coupled to a dynamical ocean model show that the interaction of (dynamical) oceanic currents with large-scale topographic features, such as the Maud Rise, does lead to the formation of transient polynya, again through Ekman transport effects. This occurs because the seamount has a dynamic impact on the three-dimensional oceanic flow field all the way up through the water column, and hence on the near surface ocean currents that are in physical contact with the sea ice. Further simulations of a sea-ice model coupled to a dynamic ocean model and forced with atmospheric buoyancy fluxes show that transient polynya can be enhanced when atmospheric cooling provides a positive feedback mechanism allowing preferential open-ocean convection to occur. The convection, which takes hold at sites where transient polynya have been initiated by sea-ice-ocean stress interaction, has an enhancing effect arising from the convective access to warmer, deeper waters. To investigate all of these effects in a hierarchical manner we use a primitive equation coupled sea-ice-ocean numerical model configured in a periodic channel domain with specified atmospheric conditions. We show that oceanic flow variability can account for temporal variability in small-scale, transient polynya and thus point to a plausible mechanism for the initiation of large-scale, sustained polynya such as the Weddell Polynya event of the mid 1970s. © 2001 Elsevier Science Ltd."
"7101874266;7004093651;7101630970;35974590700;","Further development of a hybrid-isentropic GCM",1999,"10.1256/smsqj.55816","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032708448&doi=10.1256%2fsmsqj.55816&partnerID=40&md5=fd1c74436386262156252c285c4bf68e","The UK Universities' Global Atmospheric Modelling Programme hybrid-isentropic general-circulation model (HIGCM) uses a flexible σ-θ-p vertical coordinate, where p is pressure, θ is potential temperature, and σ = p/p* where p* is surface pressure. Three major improvements to the HIGCM are presented. The first improvement is a modification to the vertical-difference scheme so that spurious vertical motions in the isentropic domain are minimized. The second improvement is a modification to the implementation of the radiation scheme so that it is now able to damp, and does not itself create, noisy temperature profiles; this allows the model to be run without ad hoc extra vertical diffusion and so allows a cleaner comparison with σ-p simulations. The third improvement is to extend the isentropic domain up to the top of the model thus allowing σ-θ or σ-θ-p simulations to be performed. Idealized baroclinic instability life-cycle experiments are used to investigate the impact of the new vertical scheme on the dynamical core of the HIGCM. The reduction in spurious vertical velocities is found to be substantial whilst the impact on the global conservation properties and overall evolution is found to be very small. These simulations also show that the commonly used nabla2(n) form of scale-selective dissipation can seriously compromise global energy conservation when model-layer thicknesses have significant horizontal gradients. The impact of the isentropic coordinate on the climate of the full GCM is investigated by performing perpetual January simulations using σ-θ, σ-θ-p and σ-p vertical coordinates. The most robust response to the isentropic coordinate is a warming of the southern hemisphere high-latitude lower stratosphere. In the northern hemisphere the largest changes in zonal mean temperature are in the polar stratosphere. The possible mechanisms by which the isentropic coordinate may yield these changes are described and investigated. The results strongly suggest that many of the potential benefits of the isentropic coordinate are realized, to some extent at least, with the HIGCM."
"7004274115;","The statistical equilibrium solution of a primitive-equation model.",1984,"10.3402/tellusa.v36i1.11464","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021579820&doi=10.3402%2ftellusa.v36i1.11464&partnerID=40&md5=510a36fc2240794022cd773b652f081f","The statistical equilibrium solution of an f-plane, primitive-equation model with a single quadratic energy invariant is determined by numerical integration. The initial condition resembles the atmosphere in terms of the shape and magnitude of its energy spectrum. The equilibrium solution is one in which energy is equipartitioned among all the linearly independent modes of the system. This state is attained after two simulated years. -from Author"
"7005808242;57216035093;35497573900;","Albedo feedback, the meridional structure of the effective heat diffusivity, and climatic sensitivity: results from dynamic and diffusive models.",1981,"10.1175/1520-0469(1981)038<1911:AFTMSO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019697469&doi=10.1175%2f1520-0469%281981%29038%3c1911%3aAFTMSO%3e2.0.CO%3b2&partnerID=40&md5=054f4729728ac1d2565fbd4268c42d71","The sensitivity of a two-level primitive equation atmospheric model to solar constant perturbations is examined in the presence of surface albedo feedback. The model is simplified to the point that a large number of numerical experiments can be performed and statistically steady states defined with relative ease.-from Authors"
"23967739600;36469994200;7404358451;6506756436;57210010133;7004279605;6603490158;8255473900;","FVM 1.0: A nonhydrostatic finite-volume dynamical core for the IFS",2019,"10.5194/gmd-12-651-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85061628953&doi=10.5194%2fgmd-12-651-2019&partnerID=40&md5=c4edfe4adf9f7919c355583b64c19746","We present a nonhydrostatic finite-volume global atmospheric model formulation for numerical weather prediction with the Integrated Forecasting System (IFS) at ECMWF and compare it to the established operational spectral-transform formulation. The novel Finite-Volume Module of the IFS (henceforth IFS-FVM) integrates the fully compressible equations using semi-implicit time stepping and non-oscillatory forward-in-time (NFT) Eulerian advection, whereas the spectral-transform IFS solves the hydrostatic primitive equations (optionally the fully compressible equations) using a semi-implicit semi-Lagrangian scheme. The IFS-FVM complements the spectral-transform counterpart by means of the finite-volume discretization with a local low-volume communication footprint, fully conservative and monotone advective transport, all-scale deep-atmosphere fully compressible equations in a generalized height-based vertical coordinate, and flexible horizontal meshes. Nevertheless, both the finite-volume and spectral-transform formulations can share the same quasi-uniform horizontal grid with co-located arrangement of variables, geospherical longitude-latitude coordinates, and physics parameterizations, thereby facilitating their comparison, coexistence, and combination in the IFS.</p> <p>We highlight the advanced semi-implicit NFT finite-volume integration of the fully compressible equations of IFS-FVM considering comprehensive moist-precipitating dynamics with coupling to the IFS cloud parameterization by means of a generic interface. These developments - including a new horizontal-vertical split NFT MPDATA advective transport scheme, variable time stepping, effective preconditioning of the elliptic Helmholtz solver in the semi-implicit scheme, and a computationally efficient implementation of the median-dual finite-volume approach - provide a basis for the efficacy of IFS-FVM and its application in global numerical weather prediction. Here, numerical experiments focus on relevant dry and moist-precipitating baroclinic instability at various resolutions. We show that the presented semi-implicit NFT finite-volume integration scheme on co-located meshes of IFS-FVM can provide highly competitive solution quality and computational performance to the proven semi-implicit semi-Lagrangian integration scheme of the spectral-transform IFS. © Author(s) 2019."
"7004093651;24492504500;7003991093;9250477900;55806956100;","A Framework for convection and boundary layer parameterization derived from conditional filtering",2018,"10.1175/JAS-D-17-0130.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042163759&doi=10.1175%2fJAS-D-17-0130.1&partnerID=40&md5=b3fc87dee6fd0ac0a97b42d65c0bc347","A new theoretical framework is derived for parameterization of subgrid physical processes in atmospheric models; the application to parameterization of convection and boundary layer fluxes is a particular focus. The derivation is based on conditional filtering, which uses a set of quasi-Lagrangian labels to pick out different regions of the fluid, such as convective updrafts and environment, before applying a spatial filter. This results in a set of coupled prognostic equations for the different fluid components, including subfilter-scale flux terms and entrainment/detrainment terms. The framework can accommodate different types of approaches to parameterization, such as local turbulence approaches and mass flux approaches. It provides a natural way to distinguish between local and nonlocal transport processes and makes a clearer conceptual link to schemes based on coherent structures such as convective plumes or thermals than the straightforward application of a filter without the quasi-Lagrangian labels. The framework should facilitate the unification of different approaches to parameterization by highlighting the different approximations made and by helping to ensure that budgets of energy, entropy, and momentum are handled consistently and without double counting. The framework also points to various ways in which traditional parameterizations might be extended, for example, by including additional prognostic variables. One possibility is to allow the large-scale dynamics of all the fluid components to be handled by the dynamical core. This has the potential to improve several aspects of convection-dynamics coupling, such as dynamical memory, the location of compensating subsidence, and the propagation of convection to neighboring grid columns. © 2018 American Meteorological Society."
"56402758400;7102322882;","Exploring the Venus global super-rotation using a comprehensive general circulation model",2016,"10.1016/j.pss.2016.09.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84993977990&doi=10.1016%2fj.pss.2016.09.001&partnerID=40&md5=0af34b866fc55dcac6fb7af056f55ee5","The atmospheric circulation in Venus is well known to exhibit strong super-rotation. However, the atmospheric mechanisms responsible for the formation of this super-rotation are still not fully understood. In this work, we developed a new Venus general circulation model to study the most likely mechanisms driving the atmosphere to the current observed circulation. Our model includes a new radiative transfer, convection and suitably adapted boundary layer schemes and a dynamical core that takes into account the dependence of the heat capacity at constant pressure with temperature. The new Venus model is able to simulate a super-rotation phenomenon in the cloud region quantitatively similar to the one observed. The mechanisms maintaining the strong winds in the cloud region were found in the model results to be a combination of zonal mean circulation, thermal tides and transient waves. In this process, the semi-diurnal tide excited in the upper clouds has a key contribution in transporting axial angular momentum mainly from the upper atmosphere towards the cloud region. The magnitude of the super-rotation in the cloud region is sensitive to various radiative parameters such as the amount of solar radiative energy absorbed by the surface, which controls the static stability near the surface. In this work, we also discuss the main difficulties in representing the flow below the cloud base in Venus atmospheric models. Our new radiative scheme is more suitable for 3D Venus climate models than those used in previous work due to its easy adaptability to different atmospheric conditions. This flexibility of the model was crucial to explore the uncertainties in the lower atmospheric conditions and may also be used in the future to explore, for example, dynamical-radiative-microphysical feedbacks. © 2016 Elsevier Ltd"
"55840004000;7006117817;26537690400;7004713805;7103158465;7006913252;7404574877;24177252800;15726838100;57191836456;57212235065;57191851976;8443545600;35572640900;35222948700;57191848835;56688303400;57191843780;6701534440;6603728352;7006790175;9433270100;20436676300;","The Brazilian Global Atmospheric Model (BAM): Performance for tropical rainfall forecasting and sensitivity to convective scheme and horizontal resolution",2016,"10.1175/WAF-D-16-0062.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994174601&doi=10.1175%2fWAF-D-16-0062.1&partnerID=40&md5=6eb5d1f02da1f8676dbb67cc98f3cbc4","This article describes the main features of the Brazilian Global Atmospheric Model (BAM), analyses of its performance for tropical rainfall forecasting, and its sensitivity to convective scheme and horizontal resolution. BAM is the new global atmospheric model of the Center for Weather Forecasting and Climate Research [Centro de Previsão de Tempo e Estudos Climáticos (CPTEC)], which includes a new dynamical core and state-of-the-art parameterization schemes. BAM's dynamical core incorporates a monotonic two-time-level semi-Lagrangian scheme, which is carried out completely on the model grid for the tridimensional transport of moisture, microphysical prognostic variables, and tracers. The performance of the quantitative precipitation forecasts (QPFs) from two convective schemes, the Grell-Dévényi (GD) scheme and its modified version (GDM), and two different horizontal resolutions are evaluated against the daily TRMM Multisatellite Precipitation Analysis over different tropical regions. Three main results are 1) the QPF skill was improved substantially with GDM in comparison to GD; 2) the increase in the horizontal resolution without any ad hoc tuning improves the variance of precipitation over continents with complex orography, such as Africa and South America, whereas over oceans there are no significant differences; and 3) the systematic errors (dry or wet biases) remain virtually unchanged for 5-day forecasts. Despite improvements in the tropical precipitation forecasts, especially over southeastern Brazil, dry biases over the Amazon and La Plata remain in BAM. Improving the precipitation forecasts over these regions remains a challenge for the future development of the model to be used not only for numerical weather prediction over South America but also for global climate simulations."
"24168098300;56033135100;7201613656;","The relative contribution of orbital forcing and greenhouse gases to the North American deglaciation",2015,"10.1002/2015GL066005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956906669&doi=10.1002%2f2015GL066005&partnerID=40&md5=0c555e8aa04a81867ceb5f0373e7f227","Understanding what drove Northern Hemisphere ice sheet melt during the last deglaciation (21-7 ka) can help constrain how sensitive contemporary ice sheets are to greenhouse gas (GHGs) changes. The roles of orbital forcing and GHGs in the deglaciation have previously been modeled but not yet quantified. Here for the first time we calculate the relative effect of these forcings on the North American deglaciation by driving a dynamical ice sheet model (GLIMMER-CISM) with a set of unaccelerated transient deglacial simulations with a full primitive equation-based ocean-atmosphere general circulation model (FAMOUS). We find that by 9 ka, orbital forcing has caused 50% of the deglaciation, GHG 30%, and the interaction between the two 20%. Orbital forcing starts affecting the ice volume at 19 ka, 2000 years before CO2 starts increasing in our experiments, a delay which partly controls their relative effect. Key Points We decompose the forcings of North American ice volume changes during the last deglaciation Orbital forcing drives 50%, greenhouse gases 30%, and forcing interactions 20% of the deglaciation The difference in timing of the forcings partly explains their relative contribution. © 2015. American Geophysical Union. All Rights Reserved."
"56006103500;7004429544;57203326023;56567092700;","Verification of a non-hydrostatic dynamical core using the horizontal spectral element method and vertical finite difference method: 2-D aspects",2014,"10.5194/gmd-7-2717-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84914709064&doi=10.5194%2fgmd-7-2717-2014&partnerID=40&md5=a775ed97de45721a5a81a8f16b19776c","The non-hydrostatic (NH) compressible Euler equations for dry atmosphere were solved in a simplified two-dimensional (2-D) slice framework employing a spectral element method (SEM) for the horizontal discretization and a finite difference method (FDM) for the vertical discretization. By using horizontal SEM, which decomposes the physical domain into smaller pieces with a small communication stencil, a high level of scalability can be achieved. By using vertical FDM, an easy method for coupling the dynamics and existing physics packages can be provided. The SEM uses high-order nodal basis functions associated with Lagrange polynomials based on Gauss-Lobatto-Legendre (GLL) quadrature points. The FDM employs a third-order upwind-biased scheme for the vertical flux terms and a centered finite difference scheme for the vertical derivative and integral terms. For temporal integration, a time-split, third-order Runge-Kutta (RK3) integration technique was applied. The Euler equations that were used here are in flux form based on the hydrostatic pressure vertical coordinate. The equations are the same as those used in the Weather Research and Forecasting (WRF) model, but a hybrid sigma-pressure vertical coordinate was implemented in this model. <br><br> We validated the model by conducting the widely used standard tests: linear hydrostatic mountain wave, tracer advection, and gravity wave over the Schär-type mountain, as well as density current, inertia-gravity wave, and rising thermal bubble. The results from these tests demonstrated that the model using the horizontal SEM and the vertical FDM is accurate and robust provided sufficient diffusion is applied. The results with various horizontal resolutions also showed convergence of second-order accuracy due to the accuracy of the time integration scheme and that of the vertical direction, although high-order basis functions were used in the horizontal. By using the 2-D slice model, we effectively showed that the combined spatial discretization method of the spectral element and finite difference methods in the horizontal and vertical directions, respectively, offers a viable method for development of an NH dynamical core. © Author(s) 2014."
"43461275900;35271403600;35767372800;45861618700;56649979200;6603709773;","Weakening of the east asian summer monsoon at 1000–1100 a.D. within the medieval climate anomaly: Possible linkage to changes in the indian ocean-western pacific",2014,"10.1002/2013JD021199","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84898437759&doi=10.1002%2f2013JD021199&partnerID=40&md5=3a2acffb6432585fefa0d4367ae1dc0a","Monsoon droughts, especially on a decadal-to-centennial timescale, may have a profound impact on the populations of East Asia. Previous work has suggested that the East Asian summer monsoon (EASM) was synchronously strong across East Asia during the Medieval Climate Anomaly (MCA, 900–1300 A.D.); however, there is a dearth of studies addressing the issue of whether or not the EASM varied significantly during the entire duration of the MCA. Here we present results from a diverse range of proxy paleoclimatic records from the monsoonal and temperate Asian region in order to evaluate the occurrence of such short timescale variability within the MCA. Within the context of an overall strong EASM during the MCA, a weakening of the monsoon was detected in many of the records during the period 1000–1100 A.D. Comparison of the timing of this event with variations of sea surface temperature (SST) of the Indian Ocean-western Pacific and with proxy records of solar activity reveals a significant covariation, suggesting that the driver of the event may have resulted from changes in the Indian Ocean-western Pacific, related to changes in solar activity. To further address the issue of a terrestrial-oceanic linkage, we used the ECHAM and the global Hamburg Ocean Primitive Equation (ECHO-G) coupled climate model to simulate the variation of EASM precipitation over the last millennium. The model results suggest an interval of weak East Asian summer monsoon at 1000–1100 A.D., and they also reveal a significant positive correlation with the SST of the Indian Ocean-western Pacific. © 2014. American Geophysical Union. All rights reserved."
"13406399300;6701431208;8696068200;6602888227;7406243250;","Held-Suarez simulations with the Community Atmosphere Model Spectral Element (CAM-SE) dynamical core: A global axial angular momentum analysis using Eulerian and floating Lagrangian vertical coordinates",2014,"10.1002/2013MS000268","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899060400&doi=10.1002%2f2013MS000268&partnerID=40&md5=f8990167e4ae7a703c5c391ba02c3c7f","In this paper, an analysis of the global AAM conservation properties of NCAR's Community Atmosphere Model Spectral Element (CAM-SE) dynamical core under Held-Suarez forcing is presented. It is shown that the spurious sources/sinks of AAM in CAM-SE are 3 orders of magnitude smaller than the parameterized (physical) sources/sinks. The effect on AAM conservation by changing various numerical aspects of the dynamical core (e.g., different vertical coordinates, reduced formal order of accuracy, increased dissipation, and decreased divergence damping) is investigated. In particular, it is noted that changing from Eulerian (hybrid-sigma) to floating Lagrangian vertical coordinates does not alter the global AAM conservation properties of CAM-SE. Key Points CAM-SE conserves global axial angular momentum (AAM) well Vertical coordinate/ polynomial order does not impact AAM properties CAM-SE dynamical core is well suited for Venus/Titan simulations © 2014. American Geophysical Union. All Rights Reserved."
"23095598900;57192002640;55204516100;46761389000;57208943246;6507601369;","Meteorologically-driven circulation and flushing times of the Bay of Algeciras, Strait of Gibraltar",2014,"10.1016/j.marpolbul.2014.01.036","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896395626&doi=10.1016%2fj.marpolbul.2014.01.036&partnerID=40&md5=a1798f2c3501cc12fbe03655e35f786c","A primitive-equation model has been used to investigate the meteorologically-driven circulation of the Bay of Algeciras. It is shown that the mean circulation of Atlantic Water (AW) is characterized by an anticyclonic cell, while Mediterranean Water (MW) follows a preferred cyclonic pathway. Meteorological forcing distorts substantially the AW mean circulation pattern, and only modulates that of the MW. Winds drive a vertical circulation cell in the Atlantic layer consistent with Ekman dynamics, whereas the horizontal circulation pattern is markedly dependent on the swift Atlantic jet entering the Mediterranean and changes from clearly anticyclonic to cyclonic as the jet separates or approaches the strait's northern shoreline. This occurs through atmospheric pressure-driven acceleration/deceleration of the jet, in agreement with internal hydraulics theory predictions. It is also found that the renewal of AW is largely modulated by tides, with meteorological forcing playing a secondary role. The opposite applies to the renewal of MW. © 2014 Elsevier Ltd."
"8623918800;7202484739;7406372329;","Evaluation of multiple dynamic initialization schemes for tropical cyclone prediction",2013,"10.1175/MWR-D-12-00329.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888404759&doi=10.1175%2fMWR-D-12-00329.1&partnerID=40&md5=325dddb746494441183eddc50a20834b","Three different dynamic initialization schemes for tropical cyclone (TC) prediction in numerical prediction systems are described and evaluated. The first scheme involves the removal of the analyzed vortex, followed by the insertion of a dynamically initialized vortex into the model analyses. This scheme is referred to as the tropical cyclone dynamic initialization scheme (TCDI) because the TC component is nudged to the observed surface pressure in an independent three-dimensional primitive equation model prior to insertion. The second scheme is a 12-h relaxation to the analyses' horizontal momentum before the forecast integration begins, and is called the dynamic initialization (DI) scheme. The third scheme is a combination of the previous two schemes, and is called the two-stage dynamic initialization scheme (TCDI/DI). In the first stage, TCDI is implemented in order to improve the representation of the TC vortex. In the second stage, DI is invoked in order to improve the balance between the inserted TC vortex and its environment. All three dynamic initialization schemes are compared with a control (CNTL) scheme, which creates the initial vortex using synthetic TC observations that match the observed intensity and structure in a three-dimensional variational data assimilation (3DVAR) system. The four schemes are tested on 120 cases in the North Atlantic and western North Pacific basins during 2010 and 2011 using the Naval Research Laboratory's TC prediction model: Coupled Ocean-Atmosphere Mesoscale Prediction System-Tropical Cyclones (COAMPS-TC). It is demonstrated that TCDI/DI performed the best overall with regard to intensity forecasts, reducing the average minimum central pressure error for all lead times by 24.4% compared to the CNTL scheme. © 2013 American Meteorological Society."
"44561454300;7403535713;","Baroclinic instability on hot extrasolar planets",2012,"10.1111/j.1365-2966.2012.21312.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863880223&doi=10.1111%2fj.1365-2966.2012.21312.x&partnerID=40&md5=c7098c2cc884ebf7d95fdb0839227bb6","We investigate baroclinic instability in flow conditions relevant to hot extrasolar planets. The instability is important for transporting and mixing heat, as well as for influencing large-scale variability on the planets. Both linear normal mode analysis and non-linear initial-value calculations are carried out - focusing on the freely-evolving, adiabatic situation. Using a high-resolution general circulation model (GCM) which solves the traditional primitive equations, we show that large-scale jets similar to those observed in current GCM simulations of hot extrasolar giant planets are likely to be baroclinically unstable, on a timescale of a few to a few tens of planetary rotations, generating cyclones and anticyclones that drive weather systems. The growth rate and scale of the most unstable mode obtained in the linear analysis are in qualitative, good agreement with the full non-linear calculations. In general, unstable jets evolve differently depending on their signs (eastward or westward), due to the change in sign of the jet curvature. For jets located at or near the equator, instability is strong at the flanks - but not at the core. Crucially, the instability is either poorly or not at all captured in simulations with low resolution and/or high artificial viscosity. Hence, the instability has not been observed or emphasized in past circulation studies of hot extrasolar planets. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS."
"7402725328;24468968100;","Effects of time step size on the simulation of tropical climate in NCAR-CAM3",2011,"10.1007/s00382-011-0994-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960983921&doi=10.1007%2fs00382-011-0994-4&partnerID=40&md5=2642361efef00809b23cba5bfe99a174","This paper describes the effects of time step on the simulation of tropical climate in the NCAR-Community Atmosphere Model version 3 (CAM3). A set of multi-year integrations are carried out in a real-planet framework using actual land-ocean distribution and observed sea surface temperature. Over the tropics there is an increase in total rainfall with a decrease in time step size. Using a lower time step, there is a decrease in the convective component of rainfall, however, the stratiform component increases, and more than compensates the decrease in the former, thus leading to a higher total rainfall. A decrease in time step leads to an increase in the frequencies of moderate, and heavy rainfall categories, which is responsible for the increase in time mean total rainfall over the tropics. Also, the spatial distribution of rainfall becomes more realistic during both summer and winter seasons. In regard to the simulation of equatorial waves, it is found that a lower time step leads to a reduction in the speed of Kelvin waves. The latent heating profile becomes more bottom-heavy with a reduction in time step size, which potentially leads to slower Kelvin waves. Finally, additional experiments conducted in an aqua-planet framework show a consistent and systematic change in the analyzed variables with change in time step, and hence confirm the robustness of the results across modeling frameworks. © 2011 The Author(s)."
"6507815511;7003467276;","The efficient global primitive equation climate model SPEEDO V2.0",2010,"10.5194/gmd-3-105-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957937134&doi=10.5194%2fgmd-3-105-2010&partnerID=40&md5=2e9bb78603e863be4918518f91e0dcbb","The efficient primitive-equation coupled atmosphere-ocean model SPEEDO V2.0 is presented. The model includes an interactive sea-ice and land component. SPEEDO is a global earth system model of intermediate complexity. It has a horizontal resolution of T30 (triangular truncation at wave number 30) and 8 vertical layers in the atmosphere, and a horizontal resolution of 2 degrees and 20 levels in the ocean. The parameterisations in SPEEDO are developed in such a way that it is a fast model suitable for large ensembles or long runs (of O(104) years) on a typical current workstation. The model has no flux correction. We compare the mean state and inter-annual variability of the model with observational fields of the atmosphere and ocean. In particular the atmospheric circulation, the mid-latitude patterns of variability and teleconnections from the tropics are well simulated. To show the capabilities of the model, we performed a long control run and an ensemble experiment with enhanced greenhouse gases. The long control run shows that the model is stable. CO2 doubling and future climate change scenario experiments show a climate sensitivity of 1.84 KW-1m2, which is within the range of state-of-the-art climate models. The spatial response patterns are comparable to state-of-the-art, higher resolution models. However, for very high greenhouse gas concentrations the parameterisations are not valid. We conclude that the model is suitable for past, current and future climate simulations and for exploring wide parameter ranges and mechanisms of variability. However, as with any model, users should be careful when using the model beyond the range of physical realism of the parameterisations and model setup."
"7402725328;7102021223;6602829165;","The impact of the time step on the intensity of ITCZ in an aquaplanet GCM",2008,"10.1175/2008MWR2478.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57149129466&doi=10.1175%2f2008MWR2478.1&partnerID=40&md5=e6d54cd764d85e2b83d0cc70919081f2","Several numerical experiments have been conducted using the NCAR Community Atmosphere Model, version 3 (CAM3) to examine the impact of the time step on rainfall in the intertropical convergence zone (ITCZ) in an aquaplanet. When the model time step was increased from 5 to 60 min the rainfall in the ITCZ decreased substantially. The impact of the time step on the ITCZ rainfall was assessed for a fixed spatial resolution (T63 with L26) for the semi-Lagrangian dynamical core (SLD). The increase in ITCZ rainfall at higher temporal resolution was primarily a result of the increase in large-scale precipitation. This increase in rainfall was caused by the positive feedback between surface evaporation, latent heating, and surface wind speed. Similar results were obtained when the semi-Lagrangian dynamical core was replaced by the Eulerian dynamical core. When the surface' evaporation was specified, changes in rainfall were largely insensitive to temporal resolution. The impact of temporal resolution on rainfall was more sensitive to the latitudinal gradient of SST than to the magnitude of SST. © 2008 American Meteorological Society."
"45761547800;6701357023;7004427982;7401993654;7406243250;","A spectral element version of CAM2",2007,"10.1175/2007MWR2058.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36749054005&doi=10.1175%2f2007MWR2058.1&partnerID=40&md5=af78746731ddfa49c5eca463c41c5502","The authors describe a recent development and some applications of a spectral element dynamical core. The improvements and development include the following: (i) the code was converted from FORTRAN 77 to FORTRAN 90; (ii) the dynamical core was extended to the generalized terrain-following, or hybrid η, vertical coordinates; (iii) a fourth-order Runge-Kutta (RK4) method for time integration was implemented; (iv) moisture effects were added in the dynamical system and a semi-Lagrangian method for moisture transport was implemented; and (v) the improved dynamical core was coupled with the Community Atmosphere Model version 2 (CAM2) physical parameterizations and Community Land Model version 2 (CLM2) in such a way that it can be used as an alternative dynamical core in CAM2. This spectral element version of CAM2 is denoted as CAM-SEM. A mass fixer as used in the Eulerian version of CAM2 (CAM-EUL) is also implemented in CAM-SEM. Results from multiyear simulations with CAM-SEM (coupled with CLM2) with climatology SST are also presented and compared with simulations from CAMEUL. Close resemblances are shown in simulations from CAM-SEM and CAM-EUL. The authors found that contrary to what is suggested by some other studies, the high-order Lagrangian interpolation (with a limiter) using the spectral element basis functions may not be suitable for moisture and other strongly varying fields such as cloud and precipitation. © 2007 American Meteorological Society."
"6602599886;7202207134;","Energetics of the layer-thickness form drag based on an integral identity",2006,"10.5194/os-2-161-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749988980&doi=10.5194%2fos-2-161-2006&partnerID=40&md5=4ab334bc22aa6f824f87ee8a00b1f3fe","The vertical redistribution of the geostrophic momentum by the residual effects of pressure perturbations (called the layer-thickness form drag) is investigated using thickness-weighted temporal-averaged mean primitive equations for a continuously stratified fluid in an adiabatic formulation. A four-box energy diagram, in which the mean and eddy kinetic energies are defined by the thickness-weighted mean velocity and the deviation from it, respectively, shows that the layer-thickness form drag reduces the mean kinetic energy and endows the eddy field with an energy cascade. The energy equations are derived using an identity (called the ""pile-up rule"") between cumulative sums of the Eulerian mean quantity and the thickness-weighted mean quantity in each vertical column. The pile-up rule shows that the thickness-weighted mean velocity satisfies a no-normal-flow boundary condition at the top and bottom of the ocean, which enables the volume budget of pressure flux divergence in the energy diagram to be determined. With the pile-up rule, the total kinetic energy based on the Eulerian mean can be rewritten in a thickness-weighted form. The four-box energy diagram in the present study should be consistent with energy diagrams of layer models, the temporal-residual-mean theory, and Iwasaki's atmospheric theory. Under certain assumptions, the work of the layer-thickness form drag in the global ocean circulation is suggested to be comparable to the work done by the wind forcing."
"23011078700;7004093651;","Entropy sources in a dynamical core atmosphere model",2006,"10.1256/qj.04.189","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644605448&doi=10.1256%2fqj.04.189&partnerID=40&md5=a205146c1c712e8e206e8f8644c088d3","Numerical atmosphere models are not generally constructed to ensure accurate treatment of entropy, but little is known about the significance of the resulting errors. This paper examines the entropy changes during a baroclinic wave simulation in a typical dynamical core model, specifically a σ-coordinate spectral model, which includes scale-selective dissipation terms in the form of a numerical hyperdiffusion. Lagrangian entropy conservation is found to be badly represented, with numerical transport errors resulting in cross-isentrope mass fluxes which are of the same size as those associated with some real diabatic processes. In a global average, the total entropy increases at a rate of just 0.5 mW m-2K-1. This, however, is seen to be the residual of two opposing numerical effects which are several times larger, namely the destruction of entropy by dispersion and Gibbs errors, and its creation by diffusion. The entropy generated by diffusion is shown to be remarkably insensitive to the details of the diffusion scheme. This leads us to hypothesize that the entropy source from diffusion is determined by the rate at which small scales are generated by the deformation field of the large-scale flow so that, while the diffusion mechanism is clearly unrealistic, the magnitude of the entropy source is, we argue, representative of that generated by physical dissipative processes in the real atmosphere. Even in this simple model it is not possible to quantify precisely the different entropy sources and sinks which combine to give the overall entropy change. However, we can say that if there is a systematic spurious entropy source in this model, then it is small, i.e. of size 0.5 mW m-2K-1 or smaller. © Royal Meteorological Society, 2006."
"7004014731;7103342287;","Dynamics of the 2-day wave in a nonlinear model of the middle and upper atmosphere",2003,"10.1029/2003jd003648","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1342312189&doi=10.1029%2f2003jd003648&partnerID=40&md5=cff02f776b50e76e133af6cc0c814d93","The 2-day wave is investigated in a three-dimensional model of the nonlinear primitive equations. Extending upward from the tropopause into the thermosphere, the model is forced stochastically by fluctuations of tropospheric wave structure. The behavior recovered is broadly consistent with linear calculations of the Rossby-gravity normal mode in the presence of instability. The mode's amplification depends sensitively upon details of the zonal-mean flow, which determine instability through a reversal of potential vorticity (PV) gradient. On the other hand, the mode's period and structure are robust. They retain much the same form under a variety of conditions. The response is sharply discriminated to wave number 3 and westward periods of 2.0-2.3 days, even though forcing is broadband. Under January conditions, strong easterlies and the accompanying reversal of PV gradient enable the mode to amplify through sympathetic interaction with the mean flow. The amplifying signal eventually emerges from random variability, which is excited by broadband forcing. Amplification continues until eddy velocities approach 70 m/s, whereupon the signal saturates. Horizontal mixing then ensues, destroying the meridional gradient of PV, which in turn limits instability and further amplification. Under June conditions the response fluctuates randomly during the entire integration, with no evidence of sustained amplification. Nevertheless, it too is sharply discriminated to westward periods of 2.0-2.3 days, achieving eddy velocities of 10-20 m/s. The sharply discriminated response appears even when a reversal of PV gradient is absent, leaving the mean flow stable. Under all of these conditions the structure of eddy stream function Ψ′ is nearly barotropic, with antisymmetric character between the hemispheres. Eddy motion assumes the form of a wave-number-3 pattern of equatorial gyres, reducing in the tropics to ν′ and strong cross-equatorial motion. The pattern is very similar to the limiting structure of the 2-day wave observed by UARS. Although magnified in the summer stratosphere and mesosphere, the structure of Ψ′ is global, with a phase reversal between the hemispheres. The modal structure extends upward into the thermosphere and, albeit weaker, as low as the tropopause. © 2003 by the American Geophysical Union."
"6603734346;","The Structure of Idealized Upper-Tropospheric Shear Lines",1999,"10.1175/1520-0469(1999)056<2830:TSOIUT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033566486&doi=10.1175%2f1520-0469%281999%29056%3c2830%3aTSOIUT%3e2.0.CO%3b2&partnerID=40&md5=fe834c879abd3912e1dacc4f584fea54","The structure of idealized two-dimensional shear lines has been calculated for specified tropopause potential temperature anomalies. A cold anomaly corresponds to an intrusion of stratospheric air into the troposphere. A balanced hydrostatic primitive equation structure is derived using an iterative technique. The resulting wind and vertical displacement of the tropopause are compared with a recent result extending quasigeostrophic theory to situations where the variation of potential vorticity along an isentrope or isobar is large, as is the case, for instance, when the isosurface intersects the tropopause. The formulation of the theory is clarified by analyzing the relation between quasigeostrophic potential vorticity and Ertel's potential vorticity. The comparison between the low-Rossby number theoretical approximation and primitive equation structures confirms the theoretical prediction that (he relative error is proportional to the Rossby number. The constant of proportionality is close to unity. The effect of the lower boundary condition on the shear line structure is analyzed. For a shear line consisting of an upper-tropospheric potential vorticity anomaly in the absence of a surface temperature anomaly it is found that the horizontal extent of the wind is not limited, as might have been expected, by the Rossby deformation radius, but rather by the largest scale of the shear line, which may be somewhat greater. © 1999 American Meteorological Society."
"6508109179;7003601925;7203047936;","The role of wave breaking, linear instability, and PV transports in model block onset",1998,"10.1175/1520-0469(1998)055<2852:TROWBL>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032468341&doi=10.1175%2f1520-0469%281998%29055%3c2852%3aTROWBL%3e2.0.CO%3b2&partnerID=40&md5=1cecf974b2d9d12f1ef01b0e280c48ba","To understand mechanisms responsible for the onset of atmospheric blocks, the authors study model blocks that form in a two-layer isentropic primitive equation model. The latter includes diabatic heating, parameterized as a Newtonian relaxation of the actual interface toward an equilibrium interface, and a zonal wavenumber-2 orography. The study concentrates on four different blocking events. One of the blocks is present in the control run, while the remaining three are excited by appropriate perturbation of the model's state vector at preselected times when the prevailing flows are classified as zonal. With the parameter calibration chosen in this investigation two phases in the formation of the blocks are conveniently identified: The first phase consists of the formation of cutoff or nearly cutoff cyclones in the upper layer at low latitudes, and the second phase features a rapid intensification of the upper-layer blocking ridge, accompanied by advection of high potential vorticity (PV) beneath it. While the initiation of the first phase may be perceived as far back in time as 6 days before the second phase, the latter occurs on a timescale of 1 to 2 days, giving rise to a well-defined blocking pattern. The first phase features the Simmons-Hoskins basic baroclinic life cycle in the total PV field that acts as a conditioner of the large-scale flow for the second phase to occur. The authors hypothesize that the second phase consists of (intense) instability of normal mode form, very much as in the theory of barotropic and baroclinic instability of three-dimensional basic-state flows for the onset of blocks. From a different perspective, based on the concept of interaction between different scales of motion, both phases predominantly involve the transport of synoptic-scale potential vorticity by the planetary waves. Planetary-planetary interactions are, however, nonnegligible."
"7102366816;7102835431;7004332887;","On the unsteady separation/intrusion of the Gaspé current and variability in Baie des Chaleurs: Modeling studies",1997,"10.1029/97JC00589","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031449356&doi=10.1029%2f97JC00589&partnerID=40&md5=46056721fdd9bf769fabf797bf8f5589","A numerical model has been used to study separation/intrusion of an unsteady, baroclinic coastal jet, the Gaspé Current (GC) and its impact on dynamics and thermodynamics of the Baie des Chaleurs (BdC, Gulf St. Lawrence, Canada). The model has 2 1/2 layers with primitive equation dynamics and an embedded bulk mixed layer (ML) model. It is forced with observed atmospheric fluxes, as well as the GC. The simulations show that the variability in the Baie des Chaleurs is controlled by the characteristics of the unsteady GC separation/intrusion. On the basis of the dynamic and vorticity balance analyses, it is found that the separation is related to the adverse pressure gradient force which is induced by the ageostrophic terms in the momentum equations and to local vorticity intensification due to the inertial effect in the flow. The simulations demonstrate characteristics of unsteady separation. The presence of separation in an accelerating current, as well as in a linear current, with strong deceleration when momentum advection is neglected, gives new insight into the mechanisms of unsteady boundary current separation. Unsteady separation or intrusion occurrence depends on the magnitude of the GC transport, as well as its rate and duration of deceleration or acceleration. The GC intrusion generates cyclonic circulation in the BdC. Prevailing westerly winds reduce the cyclonic circulation inside the bay but have little effect on separation/intrusion near the entrance. The GC either intrudes along the coastline (attachment) or after separation (reattachment). Increasing vertical shear of the GC and offshore movement of the GC axis reduces the tendency to separate. The finding of an asymmetric response of GC separation/intrusion to symmetric GC forcing explains the monthly mean features seen in observations taken in the bay. Copyright 1997 by the American Geophysical Union."
"6603552038;57203140160;57203598636;6602784254;6602451467;","A comparison of inert trace constituent transport between the University of Wisconsin isentropic-sigma model and the NCAR community climate model",1997,"10.1175/1520-0493(1997)125<0120:ACOITC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000689719&doi=10.1175%2f1520-0493%281997%29125%3c0120%3aACOITC%3e2.0.CO%3b2&partnerID=40&md5=256d5a717039a4ddb3f715867e6cbf1d","Five- and 10-day inert trace constituent distributions prognostically simulated with the University of Wisconsin (UW) hybrid isentropic-sigma (θ-σ) model, the nominally identical UW sigma (σ) model, and the National Center for Atmospheric Research Community Climate Model 2 (CCM2) are analyzed and compared in this study. The UW θ-σ and σ gridpoint models utilize the flux form of the primitive equations, while CCM2 is based on the spectral representation and uses semi-Lagrangian transport (SLT) for trace constituents. Results are also compared against a version of the CCM that uses spectral transport for the trace constituent. These comparisons 1) contrast the spatial and temporal evolution of the filamentary transport of inert trace constituents simulated with the UW θ-σ and σ models against a ""state of the art"" GCM under both isentropic and nonisentropic conditions and 2) examine the ability of the models to conserve the initial trace constituent maximum value during 10-day integrations. Results show that the spatial distributions of trace constituent evolve in a similar manner, regardless of the transport scheme or model type. However, when compared to the UW θ-σ model's ability to simulate filamentary structure and conserve the initial trace constituent maximum value, results from the other models in this study indicate substantial spurious dispersion. The more accurate conservation demonstrated with the UW θ-σ model is especially noticeable within extratropical amplifying baroclinic waves, and it stems from the dominance of two-dimensional, quasi-horizontal isentropic exchange processes in a stratified baroclinic atmosphere. This condition, which largely precludes spurious numerical dispersion associated with vertical advection, is unique to isentropic coordinates. Conservation of trace constituent maxima in sigma coordinates suffers from the complexity of, and inherent need for, resolving three-dimensional transport in the presence of vertical wind shear during baroclinic amplification, a condition leading to spurious vertical dispersion. The experiments of this study also indicate that the shape-preserving SLT scheme used in CCM2 further reduces conservation of the initial maximum value when compared to the spectral transport of trace constituents, although the patterns are more coherent and the Gibbs phenomenon is eliminated."
"6602351462;","Modeling of albedo and thermal inertia induced mesoscale circulations in the midlatitude summertime Martian atmosphere",1996,"10.1029/96JE01131","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0010389887&doi=10.1029%2f96JE01131&partnerID=40&md5=a5e1166678fe6cc25ec099336a8eef9b","Mesoscale circulations in the Martian atmosphere induced by variations in surface albedo (a) and soil thermal inertia (I) or both have been studied numerically with a two-dimensional primitive equation model. The latitudinal and seasonal parameters correspond to northern midlatitudes and midsummer. The variations in the surface properties induce surface temperature variations, which in turn, drive horizontal winds and vertical motions. A circulation cell not unlike a terrestrial seabreeze cell is formed at 1300-1400 local time (LT), the vertical motion peaks just prior to sunset and persists until 2100-2300 LT. The horizontal winds accelerate throughout the day and peak around 2100 LT. The acceleration picks up at 1600-1800 LT owing to the collapse of vertical momentum mixing. In the thermal inertia case the surface temperature gradient reverses around 1800 LT, leading to reversed forcing and nocturnal return flow. Owing to the Coriolis effect, the perpendicular wind component (v) dominates the magnitude of the horizontal flow. The extrema of horizontal winds and vertical motions occurring for variations of a = 0.20-0.30 and I = 250-350 SI units and optical thickness τ= 0.4 can be up to 7-8 m/s and approximately 3-4 cm/s, respectively. The strength of the circulation is sensitive to the amount of suspended dust; the maximum wind speed is reduced by a factor of more than 2 when τ is changed from 0.1 to 1.0. The effects of superimposed thermal inertia and albedo variations depend on their respective magnitudes and signs: if a and I increase in the same direction, the circulations are amplified, and the phases are close to phases of circulations induced ,by thermal inertia variations alone. If the variations have opposite signs, the circulations are attenuated, and the time of largest forcing can shift from daytime to the night; circulation and surface stress patterns are also shifted in phase by up to several hours. Surface stress τ0 induced by the circulations is discernible as of few hours after sunrise and peaks in the region of a and I variations. If the forcing is due to a or I variation alone or due to the amplifying combination of the two, τ0 peaks in the early afternoon (typically at 1200-1400 LT) and collapses 2-3 hours prior to sunset, primarily owing to the collapse of vertical momentum mixing. In case of opposing surface property variations, τ0 maximum is shifted in phase and can occur as early as 0800 LT owing to predominantly nocturnal forcing. The circulations studied here appear not to play a significant role in dust raising, as the magnitude of the stress generated is at least an order of magnitude below the estimated dust raising threshold. Copyright 1996 by the American Geophysical Union."
"6602697681;7005922032;","The impact of doubled CO2 on the energetics and hydrologic processes of mid-latitude transient eddies",1992,"10.1007/BF00209341","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027086192&doi=10.1007%2fBF00209341&partnerID=40&md5=decca131aa8df6c8678fa637da10efd6","Atmospheric transient eddies contribute significantly to mid-latitude energy and water vapor transports. Changes in the global climate, as induced by greenhouse enhancement, will likely alter transient eddy behavior. Unraveling all the feedbacks that occur in general circulation models (GCMs) can be difficult. Here, we isolate the transient eddies from the feedbacks and focus on the response of the eddies to simulated zonal-mean climate change that results from CO2-doubling. Using a primitive-equation spectral model, we examine the impact of such climate change on the life cycles of transient eddies. We compare transient eddy behavior in experiments with initial conditions that are given by the zonal-mean climates of GCMs with current and doubled amounts of CO2. The smaller meridional temperature gradient in a doubled CO2 climate leads to a reduction in eddy kinetic energy, especially in the subtropics. The decrease in subtropical eddy energy is related to a substantial reduction in equatorward flux of eddy activity during the latter part of the life cycle. The reduction in equatorward energy flux alters the moisture cycle. Eddy meridional transport of water vapor is shifted slightly poleward and subtropical precipitation is reduced. The water vapor transport exhibits a relatively small change in magnitude, compared to changes in eddy energy, due to the compensating effect of higher specific humidity in the doubled-CO2 climate. An increase in high-latitude precipitation is related to the poleward shift in eddy water vapor flux. Our experiments indicate that the simulation of climate change in eddy water vapor transport and eddy-generated precipitation is sensitive to model resolution and requires a minimum truncation of rhomboidal 30 in a spectral model. Surface evaporation amplifies climatic changes in water vapor transport and precipitation in our experiments. © 1992 Springer-Verlag."
"7201439545;","On the incorporation of atmospheric boundary layer effects into a balanced model",1989,"10.1002/qj.49711548906","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024870427&doi=10.1002%2fqj.49711548906&partnerID=40&md5=c87533839618c92210c5170d1c391798","A method of coupling the thermal and frictional forcing in the atmospheric boundary layer to a semi‐geostrophic model of the internal dynamics is developed. It is illustrated by two‐dimensional sea‐breeze simulations, which are compared with those of a two‐dimensional primitive equation model. It is demonstrated that the main features of the circulation on a horizontal scale larger than 20 km can be simulated with the semi‐geostrophic model, but the detailed local circulations cannot. Copyright © 1989 Royal Meteorological Society"
"6701335949;","Truncation error estimates for refinement criteria in nested and adaptive models",1989,"10.1175/1520-0493(1989)117<0872:teefrc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024830232&doi=10.1175%2f1520-0493%281989%29117%3c0872%3ateefrc%3e2.0.co%3b2&partnerID=40&md5=099e043efde1cf5d99450acc03fb2719","A simple method for calculating the truncation error at any time during an integration is described. Two cases using the shallow-water equations and the hydrostatic primitive equations are examined to demonstrate the accuracy of the method and illuminate the relationships among the truncation error, a particular discretization, the equations being solved and the flow physics. The relationship between the truncation error and the solution error is also discussed and it is argued that minimization of the truncation error is the necessary consideration for producing more accurate numerical solutions. -from Author"
"7004069241;14519102400;57192158845;","An analysis of the vertical structure equation in sigma coordinates",1985,"10.1080/07055900.1985.9649232","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0345438458&doi=10.1080%2f07055900.1985.9649232&partnerID=40&md5=fc6f78a050cda176694b73673bc7e3b2","An analysis of the vertical structure equation of sigma coordinate primitive equation models is given that brings together and extends the work of several authors. We derive the vertical structure equation, and obtain its solution for a two‐parameter family of vertical structure profiles that includes those of previous studies. For this family, it is shown that in the limiting case of an unbounded atmosphere the spectrum becomes partially continuous, rather than entirely discrete as in the bounded case. A criterion is obtained for the validity of the linearization used to derive the vertical structure equations, and it turns out that this criterion is satisfied by all but one of the previous studies. Asymptotic expansions are derived and used to explain two observations of Wiin‐Nielsen (1971a), viz. why the equivalent depths of the internal modes are relatively insensitive to the precise choice of lower boundary condition, and why one choice in particular leads to the elimination of the external mode; these asymptotic expansions also yield surprisingly accurate numerical values for the equivalent depths. Finally, the projection of atmospheric data onto modes found by direct numerical approximation of the vertical structure equation is shown, particularly for the least grave modes, to be very sensitive to resolution; consequently care must be exercised when interpreting the results of data projection studies that use this approach. © 1985 Taylor & Francis Group, LLC."
"55747696500;11939929300;57208455668;","Evaluation of tropical cyclone structure forecasts in a high-resolution version of the multiscale GFDL fvGFS model",2018,"10.1175/WAF-D-17-0140.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050870729&doi=10.1175%2fWAF-D-17-0140.1&partnerID=40&md5=95292ecef1b6f501f3f9321d0b2e9e5d","A nested version of the cubed-sphere finite-volume dynamical core (FV3) with GFS physics (fvGFS) is capable of tropical cyclone (TC) prediction across multiple space and time scales, from subseasonal prediction to high-resolution structure and intensity forecasting. Here, a version of fvGFS with 2-km resolution covering most of the North Atlantic is evaluated for its ability to simulate TC track, intensity, and finescale structure. TC structure is evaluated through a comparison of forecasts with three-dimensional Doppler radar from P-3 flights by NOAA's Hurricane Research Division (HRD), and the structural metrics evaluated include the 2-km radius of maximum wind (RMW), slope of the RMW, depth of the TC vortex, and horizontal vortex decay rate. Seven TCs from the 2010-16 seasons are evaluated, including 10 separate model runs and 38 individual flights. The model had some success in producing rapid intensification (RI) forecasts for Earl, Edouard, and Matthew. The fvGFS model successfully predicts RMWs in the 25-50-km range but tends to have a small bias at very large radii and a large bias at very small radii. The wind peak also tends to be somewhat too sharp, and the vortex depth occasionally has a high bias, especially for storms that are observed to be shallow. Composite radial wind shows that the boundary layer tends to be too deep, although the outflow structure aloft is relatively consistent with observations. These results highlight the utility of the structural evaluation of TC forecasts and also show the promise of fvGFS for forecasting TCs. © 2018 American Meteorological Society."
"54784916000;7406500188;7403968239;","Factors determining the asymmetry of ENSO",2017,"10.1175/JCLI-D-16-0923.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85025601876&doi=10.1175%2fJCLI-D-16-0923.1&partnerID=40&md5=07b3258ed4775ec711b3c11cabdb8bf3","A fundamental aspect of the observed ENSO is the positive asymmetry between its two phases: the strongest El Niño is stronger than the strongest La Niña. The nonlinear term in the equation for the surface ocean heat budget has been theorized as a cause of the asymmetry. This theory is challenged by the diversity of asymmetry among the CMIP5 models: these models all employ primitive equations and thus have the nonlinear term in the heat budget equation for the ocean surface, yet the asymmetry simulated by these models ranges from significantly negative to significantly positive. Here, the authors employ an analytical but nonlinear model-a model that simulates the observed ENSO asymmetry-to show that the nonlinear heating term does not guarantee the oscillation in the system to possess positive asymmetry. Rather, the system can have regimes with negative, zero, and positive asymmetry. The regime in which the system finds itself depends on a multitude of physical parameters. Moreover, the range of certain physical parameters for the system to fall in the regime with positive asymmetry in the oscillation is rather narrow, underscoring the difficulty of simulating the observed ENSO asymmetry by CMIP5 models. Moreover, stronger positive asymmetry is found to be associated with a more complicated oscillation pattern: the two adjacent strongest warm events are spaced farther apart and more small events occur in between. These results deepen the understanding of factors that are behind the asymmetry of ENSO and offer paths to take to improve model-simulated ENSO asymmetry. © 2017 American Meteorological Society."
"36089222400;7102157679;","Propagating annular modes: Empirical orthogonal functions, principal oscillation patterns, and time scales",2017,"10.1175/JAS-D-16-0291.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018370132&doi=10.1175%2fJAS-D-16-0291.1&partnerID=40&md5=5a190f514e2dbe266ebc6275cc25a6ea","The two leading empirical orthogonal functions (EOFs) of zonal-mean zonal wind describe north-south fluctuations, and intensification and narrowing, respectively, of the midlatitude jet. Under certain circumstances, these two leading EOFs cannot be regarded as independent but are in fact manifestations of a single, coupled, underlying mode of the dynamical system describing the evolution in time of zonal wind anomalies. The true modes are revealed by the principal oscillation patterns (POPs). The leading mode and its associated eigenvalue are complex, its structure involves at least two EOFs, and it describes poleward (or equatorward) propagation of zonal-mean zonal wind anomalies. In this propagating regime, the principal component (PC) time series associated with the two leading EOFs decay nonexponentially, and the response of the system to external forcing in a given EOF does not depend solely on the PC decorrelation time nor on the projection of the forcing onto that EOF. These considerations are illustrated using results from an idealized dynamical core model. Results from Southern Hemisphere ERA-Interim data are partly consistent with the behavior of the model's propagating regime. Among other things, these results imply that the time scale that determines the sensitivity of a model to external forcing might be different from the decorrelation time of the leading PC and involves both the rate of decay of the dynamical mode and the period associated with propagation. © 2017 American Meteorological Society."
"55829903800;7005702722;","The linear response function of an idealized atmosphere. Part II: Implications for the practical use of the fluctuation-dissipation theorem and the role of operator's nonnormality",2016,"10.1175/JAS-D-16-0099.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988328415&doi=10.1175%2fJAS-D-16-0099.1&partnerID=40&md5=ff7b4c89da46ed4ce8c989c4ea09a66d","A linear response function (LRF) relates the mean response of a nonlinear system to weak external forcings and vice versa. Even for simple models of the general circulation, such as the dry dynamical core, the LRF cannot be calculated from first principles owing to the lack of a complete theory for eddy-mean flow feedbacks. According to the fluctuation-dissipation theorem (FDT), the LRF can be calculated using only the covariance and lag-covariance matrices of the unforced system. However, efforts in calculating the LRFs for GCMs using FDT have produced mixed results, and the reason(s) behind the poor performance of the FDT remain(s) unclear. In Part I of this study, the LRF of an idealized GCM, the dry dynamical core with Held-Suarez physics, is accurately calculated using Green's functions. In this paper (Part II), the LRF of the same model is computed using FDT, which is found to perform poorly for some of the test cases. The accurate LRF of Part I is used with a linear stochastic equation to show that dimension reduction by projecting the data onto the leading EOFs, which is commonly used for FDT, can alone be a significant source of error. Simplified equations and examples of 2 × 2 matrices are then used to demonstrate that this error arises because of the nonnormality of the operator. These results suggest that errors caused by dimension reduction are a major, if not the main, contributor to the poor performance of the LRF calculated using FDT and that further investigations of dimension-reduction strategies with a focus on nonnormality are needed. © 2016 American Meteorological Society."
"55940993400;7202748672;","A four-dimensional incremental analysis update for the ensemble Kalman filter",2016,"10.1175/MWR-D-15-0246.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978127942&doi=10.1175%2fMWR-D-15-0246.1&partnerID=40&md5=f8b1ae133de0f9dad54d71e8104d6467","The analysis produced by the ensemble Kalman filter (EnKF) may be dynamically inconsistent and contain unbalanced gravity waves that are absent in the real atmosphere. These imbalances can be exacerbated by covariance localization and inflation. One strategy to combat the imbalance in the analyses is the incremental analysis update (IAU), which uses the dynamic model to distribute the analyses increments over a time window. The IAU has been widely used in atmospheric and oceanic applications. However, the analysis increment that is gradually introduced during a model integration is often computed once and assumed to be constant for an assimilation window, which can be seen as a three-dimensional IAU (3DIAU). Thus, the propagation of the analysis increment in the assimilation window is neglected, yet this propagation may be important, especially for moving weather systems. To take into account the propagation of the analysis increment during an assimilation window, a four-dimensional IAU (4DIAU) used with the EnKF is presented. It constructs time-varying analysis increments by applying all observations in an assimilation window to state variables at different times during the assimilation window. It then gradually applies these time-varying analysis increments through the assimilation window. Results from a dry two-layer primitive equation model and the NCEP GFS show that EnKF with 4DIAU (EnKF-4DIAU) and 3DIAU (EnKF-3DIAU) reduce imbalances in the analysis compared to EnKF without initialization (EnKF-RAW). EnKF-4DIAU retains the time-varying information in the analysis increments better than EnKF-3DIAU, and produces better analysis and forecast than either EnKF-RAW or EnKF-3DIAU. © 2016 American Meteorological Society."
"57105531200;56726831900;56284582200;","The non-conservation of potential vorticity by a dynamical core compared with the effects of parametrized physical processes",2016,"10.1002/qj.2729","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957657358&doi=10.1002%2fqj.2729&partnerID=40&md5=3e345829df1c5799e504b3c6c98090d7","Numerical models of the atmosphere combine a dynamical core, which approximates solutions to the adiabatic, frictionless governing equations for fluid dynamics, with tendencies arising from the parametrization of other physical processes. Since potential vorticity (PV) is conserved following fluid flow in adiabatic, frictionless circumstances, it is possible to isolate the effects of non-conservative processes by accumulating PV changes in an air-mass-relative framework. This 'PV tracer technique' is used to accumulate separately the effects on PV of each of the different non-conservative processes represented in a numerical model of the atmosphere. Dynamical cores are not exactly conservative because they introduce, explicitly or implicitly, some level of dissipation and adjustment of prognostic model variables which acts to modify PV. Here, the PV tracers technique is extended to diagnose the cumulative effect of the non-conservation of PV by a dynamical core and its characteristics relative to the PV modification by parametrized physical processes. Quantification using the Met Office Unified Model reveals that the magnitude of the non-conservation of PV by the dynamical core is comparable to those from physical processes. Moreover, the residual of the PV budget, when tracing the effects of the dynamical core and physical processes, is at least an order of magnitude smaller than the PV tracers associated with the most active physical processes. The implication of this work is that the non-conservation of PV by a dynamical core can be assessed in case-studies with a full suite of physics parametrizations and directly compared with the PV modification by parametrized physical processes. The non-conservation of PV by the dynamical core is shown to move the position of the extratropical tropopause while the parametrized physical processes have a lesser effect at the tropopause level. © 2016 Royal Meteorological Society."
"56726831900;6507612700;","The slowly evolving background state of the atmosphere",2015,"10.1002/qj.2518","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941191836&doi=10.1002%2fqj.2518&partnerID=40&md5=4387e90f08d0cfa94197ebabf10a96e1","The theory of wave-mean flow interaction requires a partition of the atmospheric flow into a notional background state and perturbations to it. Here, a background state, known as the Modified Lagrangian Mean (MLM), is defined as the zonally symmetric state obtained by requiring that every potential vorticity (PV) contour lying within an isentropic layer encloses the same mass and circulation as in the full flow. For adiabatic and frictionless flow, these two integral properties are time-invariant and the MLM state is a steady solution of the primitive equations. The time dependence in the adiabatic flow is put into the perturbations, which can be described by a wave-activity conservation law that is exact even at large amplitude. Furthermore, the effects of non-conservative processes on wave activity can be calculated from the conservation law. A new method to calculate the MLM state is introduced, where the position of the lower boundary is obtained as part of the solution. The results are illustrated using Northern Hemisphere ERA-Interim data. The MLM state evolves slowly, implying that the net non-conservative effects are weak. Although 'adiabatic eddy fluxes' cannot affect the MLM state, the effects of Rossby-wave breaking, PV filamentation and subsequent dissipation result in sharpening of the polar vortex edge and meridional shifts in the MLM zonal flow, both at tropopause level and on the winter stratospheric vortex. The rate of downward migration of wave activity during stratospheric sudden warmings is shown to be given by the vertical scale associated with polar vortex tilt divided by the time-scale for wave dissipation estimated from the wave-activity conservation law. Aspects of troposphere-stratosphere interaction are discussed. The new framework is suitable to examine the climate and its interactions with disturbances, such as midlatitude storm tracks, and makes a clean partition between adiabatic and non-conservative processes. © 2015 Royal Meteorological Society."
"57210180554;6602858513;","Impact of variable-resolution meshes on midlatitude baroclinic eddies using CAM-MPAS-A",2014,"10.1175/MWR-D-13-00366.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84910020650&doi=10.1175%2fMWR-D-13-00366.1&partnerID=40&md5=352990bf4a688fdae8afaf75f0d893bf","The effects of a variable-resolution mesh on simulated midlatitude baroclinic eddies in idealized settings are examined. Both aquaplanet and Held-Suarez experiments are performed using the Model for Prediction Across Scales-Atmosphere (MPAS-A) hydrostatic dynamical core implemented within the National Science Foundation-Department of Energy (NSF-DOE) Community Atmosphere Model (CAM-MPAS-A). In the real world, midlatitude eddy activity is organized by orography, land-sea contrasts, and sea surface temperature anomalies. In these zonally symmetric idealized settings, transients should have an equal probability of occurring at any longitude. However, the use of a variable-resolution mesh with a circular high-resolution region centered at 308N results in a maximum in eddy kinetic energy on the eastern side and downstream of this high-resolution region in both aquaplanet and Held-Suarez CAM-MPAS-A simulations. The presence of a geographically confined maximum in both simulations suggests this response is mainly attributable to CAM-MPAS-A's ability to resolve eddies via the model dynamics as resolution increases. However, in the aquaplanet simulation, a secondary maximum in eddy kinetic energy is present, which is probably linked to the resolution dependencies of the CAMphysics. Thesemesh responsesmust be considered when interpreting realworld variable-resolution CAM-MPAS-A simulations, particularly in climate change experiments. © 2014 American Meteorological Society."
"56256258400;7003991093;","The role of criticality on the horizontal and vertical scales of extratropical eddies in a dry GCM",2014,"10.1175/JAS-D-13-0351.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903884761&doi=10.1175%2fJAS-D-13-0351.1&partnerID=40&md5=384800eff41ebdb6c70a505db619dcfe","This paper discusses the sensitivity of the horizontal and vertical scales of extratropical eddies when criticality is varied in a dry, primitive-equation, general circulation model. Criticality is a measure of extratropical isentropic slope and when defined appropriately its value is often close to 1 for Earth's climate. The model is forced by a Newtonian relaxation of temperature to a prescribed temperature profile, and criticality is increased by increasing the thermal relaxation rate on the mean flow. When criticality varies near 1, it is shown that there exists a weakly nonlinear regime in which the eddy scale increases with criticality without involving an inverse cascade, while at the same time the Rossby radius may in fact decrease. The quasigeostrophic instability of the Charney problem is revisited. It is demonstrated that both the horizontal and vertical scales of the most unstable wave depend on criticality, and simple estimates for the two scales are obtained. The authors reconcile the opposite trends of the eddy scale and Rossby radius and obtain an estimate for the eddy scale in terms of the Rossby radius and criticality that is broadly consistent with simulations. © 2014 American Meteorological Society."
"36138641800;","Interactions between topographically and thermally forced stationary waves: Implications for ice sheet evolution",2012,"10.3402/tellusa.v64i0.11088","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84865118748&doi=10.3402%2ftellusa.v64i0.11088&partnerID=40&md5=96d01f406b48a8ac2de219875616de87","This study examines mutualinteractions between stationary waves and ice sheets using a dry atmospheric primitive equation model coupled to a three dimensional thermomechanical ice sheet model. The emphasis is on how non linear interactions between thermal and topographical forcing of the stationary waves influence the ice sheet evolution by changing the ablation. Simulations are conducted in which a small ice cap, on an idealised Northern Hemisphere continent, evolves to an equilibrium continental scale ice sheet. In the absence of stationary waves, the equilibrium ice sheet arrives at symmetric shape with a zonal equatorward margin. In isolation, the topographically induced stationary waves have essentially no impact on the equilibrium features of the ice sheet. The reason is that the temperature anomalies are located far from the equatorward ice margin. When forcing due to thermal cooling is added to the topographical forcing, thermally induced perturbation winds amplify the topographically induced stationary wave response, which that serves to increase both the equatorward extent and the volume of the ice sheet. Roughly, a 10% increase in the ice volume is reported here. Hence, the present study suggests that the topographically induced stationary wave response can be substantially enhanced by the high albedo of ice sheets.© 2012 J. Liakka."
"56613241100;35510247100;57203684194;","A novel technique for nonlinear sensitivity analysis: Application to moist predictability",2009,"10.1002/qj.460","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349606211&doi=10.1002%2fqj.460&partnerID=40&md5=cdba867f491dc4296f0015558fc119ca","A new nonlinear technique is described to compute the sensitivity of synoptic perturbation growth to environmental moisture. The perturbation growth is defined using a nonlinear generalization of singular vectors called Nonlinear Singular Vectors (NLSV). For a given atmospheric state evolving in time, the nonlinear sensitivity method consists in maximizing the growth rate of perturbations by seeking both the optimal NLSV perturbations and the most favorable spatial distribution of the moisture field. This results in a new atmospheric state that differs initially only by the water vapour field. The NLSV computed along this new state has the largest possible growth rate for all possible water vapour fields. We apply this method to a simulation of the moist primitive equations. For the particular case we study, we obtain a moistening of the lower troposphere and an amplification of energy of optimal perturbations three times larger than the amplification of optimal perturbations computed without altering the water vapour field. The optimal perturbations are similar to the perturbations of the unmodified water vapour case. A noteworthy property is that the complete saturation of the atmosphere leads to a smaller increase in amplification rate, which means that the water vapour field is strongly tied to the NLSV structure. Mechanisms explaining these results are discussed. This technique overcomes the limitations (in particular the linearity assumption) of moist singular vector analysis using moist norms or adjoint sensitivity analysis. It can be applied to diagnose sensitivity to other fields as well. © 2009 Royal Meteorological Society."
"16475714800;7006184606;","Wind-evaporation feedback and abrupt seasonal transitions of weak, axisymmetric hadley circulations",2008,"10.1175/2007JAS2608.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-52049087611&doi=10.1175%2f2007JAS2608.1&partnerID=40&md5=28c6467e6f1224c413440dc1e3168c7b","For an imposed thermal forcing localized off the equator, it is known that conservation of absolute angular momentum in axisymmetric flow produces a nonlinear response once the forcing exceeds a critical amplitude. It is shown here that, for a moist atmosphere in convective quasi-equilibrium, the combination of wind-dependent ocean surface enthalpy fluxes and zonal momentum advection can provide a separate feedback that causes the meridional flow to evolve nonlinearly as a function of a sea surface temperature (SST) forcing, even if an angular momentum-conserving response is not achieved. This wind-evaporation feedback is examined in both an axisymmetric primitive equation model and a simple model that retains only a barotropic and single baroclinic mode. Only SST forcings that do not produce an angular momentum-conserving response are examined here. The wind-evaporation feedback is found to be inhibited in models with linear dynamics because the barotropic component of the Hadley circulation, which is coupled to the baroclinic circulation via surface drag, keeps surface winds small compared to upper-level winds. In models with nonlinear dynamics, the convergence of zonal momentum into the ascending branch of the cross-equatorial Hadley cell can create barotropic westerlies that constructively add to the baroclinic wind at the surface, thereby eliminating the inhibition of the wind-evaporation feedback. The possible relevance of these results to the onset of monsoons is discussed. © 2008 American Meteorological Society."
"7004014731;7103342287;","Control of the tropical tropopause and vertical transport across it",2004,"10.1175/1520-0442(2004)017<0965:COTTTA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842689995&doi=10.1175%2f1520-0442%282004%29017%3c0965%3aCOTTTA%3e2.0.CO%3b2&partnerID=40&md5=272db5a9aef1cb010a84ab7793abe890","A 3D primitive equation model is used to investigate how the tropical tropopause is influenced by cumulus convection in the troposphere and mean upwelling in the stratosphere. The model simulates the residual mean circulation explicitly, whereas it represents the influence of convection on large-scale structure through statistical properties of cloud. Within this global framework, a change of extratropical planetary waves induces a large change of downwelling over the winter hemisphere, compensated at lower latitudes by a change of upwelling. This exerts a major influence on thermal structure in the extratropics, but only a minor one in the Tropics. On seasonal time scales, however, the influence in the Tropics is significant. During northern winter, extratropical planetary waves are sharply amplified. The accompanying intensification of tropical upwelling, while small compared to the intensification of extratropical downwelling, accounts for about half of the observed seasonal change of the tropical tropopause. Remarkably, anomalous thermal structure extends even into the summer hemisphere where the tropopause is anomalously high and cold. Just the reverse is found in the winter hemisphere. Contrasting with this is the dependence on convection, which is large in the Tropics. An intensification or deepening of convection elevates and cools the tropical tropopause. Accompanying those changes overhead is anomalous downwelling in the lowermost stratosphere. It is forced by convective cooling, at and above the level of neutral buoyancy (LNB), where overshooting cumulus are colder than their environment. Anomalous temperature is out of phase above and below the LNB, consistent with cumulus detrainment and observed changes that accompany the outbreak of cold cloud. Conversely, an elevation of the LNB, as would accompany an increase of moist static energy (e.g., SST), elevates but warms the tropical tropopause. This dependence may explain geographical variations of the tropopause. A change of tropical convection also influences the extratropical circulation, secondarily through the absorption of planetary waves, which then modulates downwelling and temperature over the winter hemisphere. Vertical transport into the stratosphere depends on both mechanisms, which interact. Above the LNB, convective cooling drives environmental downwelling that transports stratospheric air into the troposphere at sites of deep convection. There, air of high θ mixes with air of low θ that has been convected above the LNB inside overshooting cumulus. The mixture, having been cooled mechanically, then experiences enhanced radiative warming that carries it upward at sites removed from convection. © 2004 American Meteorological Society."
"55899460500;6701395093;","Primitive-equation-based low-order models with seasonal cycle. Part II: Application to complexity and nonlinearity of large-scale atmosphere dynamics",2003,"10.1175/1520-0469(2003)060<0478:PEBLOM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0042823431&doi=10.1175%2f1520-0469%282003%29060%3c0478%3aPEBLOM%3e2.0.CO%3b2&partnerID=40&md5=d34bf889a27e2ad3e7152b3894d9c030","A recently developed class of semiempirical low-order models is utilized for the reexamination of several aspects of the complexity and nonlinearity of large-scale dynamics in a GCM. Given their low dimensionality, these models are quite realistic, due to the use of the primitive equations, an efficient EOF basis, and an empirical seasonally dependent linear parameterization of the impact of unresolved scales and not explicitely described processes. Fairly different results are obtained with respect to the dependence of short-term predictability or climate simulations on the number of employed degrees of freedom. Models using 500 degrees of freedom are significantly better in short-term predictions than smaller counterparts. Meaningful predictions of the first 500 EOFs are possible for 4-5 days, while the mean anomaly correlation for the leading 30 EOFs stays above 0.6 for up to 9 days. In a 30-EOF model this is only 6 days. A striking feature is found when it comes to simulations of the monthly mean states and transient fluxes: the 30-EOF model is performing just as well as the 500-EOF model. Since similar behavior is also found in the reproduction of the number and shape of the three significant cluster centroids in the January data of the GCM, one can speculate on a characteristic dimension in the range of a few tens for the large-scale part of the climate attractor. A partial failure diagnosed in the predictability of climate change by our statistical-dynamical models indicates that the employed empirical parameterizations might actually be climate dependent. Understanding their dependence on the large-scale flow could be a pre-requisite for applicability to climate change studies. In a further analysis no support is found for the classic hypothesis that the observed cluster centroids, indicating multimodality in the climate statistics, can be interpreted as quasi steady states of the GCM's low-frequency dynamics."
"35611249700;25223207200;","Dynamics and mechanism for sea surface cooling near the Indian tip during winter monsoon",2002,"10.1029/2000jc000455","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037113444&doi=10.1029%2f2000jc000455&partnerID=40&md5=9682a6673c4300eb1b6c75da762f718b","Wintertime sea surface temperature (SST) cooling south of the Indian tip (hereafter tip) is investigated during a 14 day gap wind event (21 January to 3 February 1997) using satellite data and the three-dimensional, primitive equation, sigma coordinate Princeton Ocean Model (POM). The advanced very high resolution radiometer SST reveals surface cooling of 1.5°C over the 14 day period near west of Sri Lanka. A spatial-mean time series of surface forcing west of Sri Lanka indicate a bell-shaped pattern, which is characterized by maximum wind stress and outgoing heat flux (sum of turbulent heat flux and net surface long-wave radiation) of 0.12 N/m2 and 450 W/m2, respectively, on 27 January. POM simulation is performed with realistic bottom topography, with seasonal stratification, and with daily mean surface forcing derived from NASA scatterometer (NSCAT) winds and National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) meteorological variables. During 21 - 28 January, Ekman dynamics together with positive wind stress curl promote SST cooling along the west coast of Sri Lanka. Thereafter irregular and shallow topography near the tip promotes diapycnal mixing, and the characteristic surface circulation significantly influences the evolution of the SST pattern along the periphery of the tip. An anticyclonic circulation evolves in the Gulf of Mannar under the influence of local negative wind stress curl after 27 January. Examination of a zonal section of density and vertical heat diffusion reveals that the initial stratification in the vicinity of the tip weakens because of diapycnal mixing and vertical diffusion of the surface heat. The mixed layer heat budget near the west of Sri Lanka and south of the tip reveals that the surface heat depletion dictates SST changes throughout the event. From our earlier works [Luis and Kawamura, 2000, 2001] and from the results of the present investigation it is inferred that the wintertime SST cooling in the vicinity of the tip is a case of topography-monsoon-ocean interaction."
"7102328865;7005520511;7202948477;","A coupled ice-ocean model for the Greenland, Iceland and Norwegian Seas",1999,"10.1016/S0967-0645(99)00019-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033151610&doi=10.1016%2fS0967-0645%2899%2900019-3&partnerID=40&md5=133d334850e637cd90f029f0a906abdf","Simulations from a coupled ice-ocean model that highlight the importance of synoptic forcing on sea-ice dynamics are described. The ocean model is a non-hydrostatic primitive equation model coupled to a dynamic thermodynamic sea ice model. The ice modelling sensitivity study presented here is part of an ongoing research programme to define the role played by sea ice in the energy balance of the Greenland Sea. The different categories of sea ice found in the subpolar regions are simulated through the use of equations for thin ice, thick ice and the Marginal Ice Zone. A basin scale numerical model of the Greenland, Iceland and Norwegian Seas has a horizontal resolution of 20 km and a vertical grid spacing of 50 m. This resolution is adequate for resolving the mesoscale topographic structures known to control the circulation in this region. The spin-up reproduces the main features of the circulation, including the cyclonic gyres in the Norwegian and Greenland Basins and Iceland Plateau. Topographic steering of the flow is evident. The baroclinic Rossby radius of deformation is between 5 and 10 km so that the model is not eddy-resolving. The coupled ice-ocean model was run for a period of two weeks. The influence of horizontal resolution of the atmospheric model was tested by comparing simulations using six hourly wind fields from the ECMWF with those generated using six hourly fields from a HIRLAM, with horizontal resolutions of 1°and 0.18°respectively. The simulations show reasonable agreement with satellite ice compactness data and data of ice transports across sections at 79°N, 75°N and Denmark Strait."
"55046667600;7102202012;","The dependence of the Hadley circulation on the thermal relaxation time",1997,"10.1175/1520-0469(1997)054<1379:tdothc>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031136312&doi=10.1175%2f1520-0469%281997%29054%3c1379%3atdothc%3e2.0.co%3b2&partnerID=40&md5=3623964eece1670e89ec841c8f8b33d8","Analytic and numerical solutions are found for the nonlinear Hadley circulation problem with respect to the dependence of the strength and the extent of the Hadley circulation on the thermal relaxation time. The dependence on the thermal relaxation time is a crucial parameter to investigate since the simplifications used in previous studies assumed a large thermal relaxation time, to justify the geostrophic assumption, but in the presence of moist convection, thermal relaxation may be fast in the convection regions. In this study, a primitive equation model is used to investigate the effect of different latitudinal distribution of thermal relaxation time on the extent of the circulation cells, the zonal wind, the temperature distribution, and the strength of the meridional circulations. It is found that the extent of the Hadley circulation is insensitive to the value of the thermal relaxation time τ, while the strength of the circulation is very sensitive to τ (but in a way that is predictable based on the 1/τ scaling)."
"7003440089;6504352932;7003627515;","Simulation of atmospheric circulation during the GIMEX 91 experiment using a meso-γ primitive equations model",1995,"10.1175/1520-0442(1995)008<2843:SOACDT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029505491&doi=10.1175%2f1520-0442%281995%29008%3c2843%3aSOACDT%3e2.0.CO%3b2&partnerID=40&md5=6e686b6b401bb034b9028c9beac43fb4","A meso-γ-scale atmospheric model has been used to simulate atmospheric circulations observed during the Greenland Ice Margin EXperiment (GIMEX). The simulations shown here are two-dimensional and cover the 12-13 July 1991 period, a typical summer situation in this area. The synoptic-scale wind forcing is included. Simulated wind, temperature, humidity, and turbulent fluxes compare reasonably well with available observations. The simulated heat used to melt snow or ice is also shown. -from Authors"
"7201494779;7404405578;7409783816;6701475557;7409565879;","A two-dimensional model with coupled dynamics, radiation, and photochemistry 1. Simulation of the middle atmosphere",1993,"10.1029/93jd01909","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027836340&doi=10.1029%2f93jd01909&partnerID=40&md5=7367770c9fde12419c2bae9737c77328","Spatial and seasonal distribution of ozone and other trace gases are simulated using the interactive two-dimensional model of the stratosphere (Schneider et al., 1989) updated to include full gas phase chemistry. The model consists of a primitive equation dynamics module, a full radiative transfer scheme, and a comprehensive gas phase chemistry module. The circulation is derived from heating rates in the stratosphere that are calculated using model-generated ozone. In the troposphere, parameterized heating rates are adopted. The eddy momentum flux divergence in the zonal mean momentum equation is given by the eddy fluxes of potential vorticity. Eddy fluxes of potential vorticity and tracers are parameterized using a set of predetermined diffusion coefficients. The adopted values for Kyy, which are based on values derived by Newman et al. (1988), show a hemispherical asymmetry in that the values in the lower stratosphere are consistently smaller in the southern hemisphere. -from Authors"
"55951683800;","The climatic response of the Arctic Ocean to Soviet river diversions",1984,"10.1007/BF00144608","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021639717&doi=10.1007%2fBF00144608&partnerID=40&md5=29439097ef987a94b902febf097670af","A numerical model is constructed to evaluate the effect of river diversions on the circulation of the Arctic Ocean, including the climatically important response in the extent of sea ice. The ocean model solves the primitive equations of motion in finite-difference form for the irregular geometry of the Arctic Ocean and Greenland/Norwegian Sea, using 110 km horizontal grid spacing and up to 13 unevenly spaced levels in the vertical. Annual mean atmospheric conditions and river discharges are specified from observations. The presence of sea ice is diagnosed on the basis of model ocean temperature; and the effects of sea ice on the surface fluxes of momentum, heat, and salt are included in a simplified way. Lateral exchanges at the southernmost boundary are held near observed values but respond to circulation changes in the Greenland/Norwegian Sea. Three equilibrium solutions are obtained by eighty-year integrations from simple initial conditions: the first with inflow from all rivers, the second with one-third of the inflow diverted from four major rivers (the Ob, Yenesei, Dvina, and Pechora), and the third with total diversion from those rivers. The middle case corresponds to maximal diversions which are either planned or envisioned by the Soviet Union over the next fifty years, whereas the final extreme case is run in the event that model sensitivity is low relative to that of nature. The control integration gives a good simulation of known water masses and currents. In the Central Arctic, for example, the model correctly predicts a strong shallow halocline, a relatively warm intermediate layer of Atlantic origin, and a temperature jump across the deep Lomonosov Ridge. The overall pattern of surface salinity and the margin of the pack ice are also properly simulated. When runoff into the marginal Kara and Barents Seas is diverted, either in part or in full, almost no effect on the halocline results in the Central Arctic. In particular, deep convection does not develop in the Eurasian Basin, the possibility of which was suggested by Aagaard and Coachman (1975). The vertical stability within the two marginal seas is considerably decreased by the total diversion of four rivers, but not to the point of convective overturning. The surface currents in this area change to confine the water with increased salinity to the shelf region. At deeper levels, an increased salinity tongue spreads into the deep basins of the ice-free Greenland/Norwegian Sea, where existing deep convection is slightly enhanced. As a result, there is some additional heat loss from the Atlantic layer before it enters the Central Arctic. The ice extent remains nearly the same as before within the Kara and Barents Seas. In fact, since modified bottom currents over the continental shelf bring in less heat from the Greenland Sea, an increased thickness of sea ice may result there, in spite of reduced vertical stability. These model responses are generally in agreement with those suggested by Micklin (1981) and by Soviet investigations of the effect of river diversions. These annualmean results should be regarded as tentative, pending confirmation by studies which include the seasonal cycles of runoff and atmospheric forcing. © 1984 D. Reidel Publishing Company."
"7102315560;","Scale selection and energy spectra of disturbances in Southern Hemisphere flows.",1981,"10.1175/1520-0469(1981)038<2573:SSAESO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019728737&doi=10.1175%2f1520-0469%281981%29038%3c2573%3aSSAESO%3e2.0.CO%3b2&partnerID=40&md5=f113a1c2eb1450191cfd5b944782d87a","The growth and nonlinear interaction of initially small-amplitude disturbances, having a complete spectrum of zonal wavenumbers, with zonally averaged flows characteristic of January and May Southern Hemisphere situations, are studied in a multilevel primitive equation spectral model incorporating spherical geometry and viscous dissipation.-from Author"
"16022263500;56942309200;57194417556;57194102643;26659116700;23484340400;55967916100;57219758400;","The Limits of the Primitive Equations of Dynamics for Warm, Slowly Rotating Small Neptunes and Super Earths",2019,"10.3847/1538-4357/aaf6e9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062008245&doi=10.3847%2f1538-4357%2faaf6e9&partnerID=40&md5=162b6ecefb6f398151ff4ed76f243fb4","We present significant differences in the simulated atmospheric flow for warm, tidally locked small Neptunes and super Earths (based on a nominal GJ 1214b) when solving the simplified, and commonly used, primitive dynamical equations or the full Navier-Stokes equations. The dominant prograde, superrotating zonal jet is markedly different between the simulations, which are performed using practically identical numerical setups, within the same model. The differences arise due to the breakdown of the so-called ""shallow-fluid"" and traditional approximations, which worsens when rotation rates are slowed, and day-night temperature contrasts are increased. The changes in the zonal advection between simulations solving the full and simplified equations, give rise to significant differences in the atmospheric redistribution of heat, altering the position of the hottest part of the atmosphere and temperature contrast between the daysides and nightsides. The implications for the atmospheric chemistry, and therefore, observations need to be studied with a model including a more detailed treatment of the radiative transfer and chemistry. Small Neptunes and super Earths are extremely abundant and important, potentially bridging the structural properties (mass, radius, and composition) of terrestrial and gas giant planets. Our results indicate care is required when interpreting the output of models solving the primitive equations of motion for such planets. © 2019. The American Astronomical Society. All rights reserved."
"35218751800;35960179900;35092376500;9239400200;6602705884;","Exploring the Lyapunov instability properties of high-dimensional atmospheric and climate models",2018,"10.5194/npg-25-387-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047723393&doi=10.5194%2fnpg-25-387-2018&partnerID=40&md5=0be42d1c1a02418cb12d1dbbdb826a49","The stability properties of intermediate-order climate models are investigated by computing their Lyapunov exponents (LEs). The two models considered are PUMA (Portable University Model of the Atmosphere), a primitive-equation simple general circulation model, and MAOOAM (Modular Arbitrary-Order Ocean-Atmosphere Model), a quasi-geostrophic coupled ocean-atmosphere model on a β-plane. We wish to investigate the effect of the different levels of filtering on the instabilities and dynamics of the atmospheric flows. Moreover, we assess the impact of the oceanic coupling, the dissipation scheme, and the resolution on the spectra of LEs. The PUMA Lyapunov spectrum is computed for two different values of the meridional temperature gradient defining the Newtonian forcing to the temperature field. The increase in the gradient gives rise to a higher baroclinicity and stronger instabilities, corresponding to a larger dimension of the unstable manifold and a larger first LE. The Kaplan-Yorke dimension of the attractor increases as well. The convergence rate of the rate function for the large deviation law of the finite-time Lyapunov exponents (FTLEs) is fast for all exponents, which can be interpreted as resulting from the absence of a clear-cut atmospheric timescale separation in such a model. The MAOOAM spectra show that the dominant atmospheric instability is correctly represented even at low resolutions. However, the dynamics of the central manifold, which is mostly associated with the ocean dynamics, is not fully resolved because of its associated long timescales, even at intermediate orders. As expected, increasing the mechanical atmosphere-ocean coupling coefficient or introducing a turbulent diffusion parametrisation reduces the Kaplan-Yorke dimension and Kolmogorov-Sinai entropy. In all considered configurations, we are not yet in the regime in which one can robustly define large deviation laws describing the statistics of the FTLEs. This paper highlights the need to investigate the natural variability of the atmosphere-ocean coupled dynamics by associating rate of growth and decay of perturbations with the physical modes described using the formalism of the covariant Lyapunov vectors and considering long integrations in order to disentangle the dynamical processes occurring at all timescales. © 2018 Author(s)."
"36644095800;36992744000;","An explanation for the sensitivity of the mean state of the community atmosphere model to horizontal resolution on aquaplanets",2017,"10.1175/JCLI-D-16-0069.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020088698&doi=10.1175%2fJCLI-D-16-0069.1&partnerID=40&md5=550303a712ff0bf1b2fe718d1bacf6db","The sensitivity of the mean state of the Community Atmosphere Model to horizontal resolutions typical of present-day general circulation models is investigated in an aquaplanet configuration. Nonconvergence of the mean state is characterized by a progressive drying of the atmosphere and large reductions in cloud coverage with increasing resolution. Analyses of energy and moisture budgets indicate that these trends are balanced by variations in moisture transport by the resolved circulation, and a reduction in activity of the convection scheme. In contrast, the large-scale precipitation rate increases with resolution, which is approximately balanced by greater advection of dry static energy associated with more active resolved vertical motion in the ascent region of the Hadley cell. An explanation for the sensitivity of the mean state to horizontal resolution is proposed, based on linear Boussinesq theory. The authors hypothesize that an increase in horizontal resolution in the model leads to a reduction in horizontal scale of the diabatic forcing arising from the column physics, facilitating finescale flow and faster resolved convective updrafts within the dynamical core, and steering the coupled system toward a new mean state. This hypothesis attempts to explain the underlying mechanism driving the variations in moisture transport observed in the simulations. © 2017 American Meteorological Society."
"55940118700;28267547300;7004471232;","On the merger of subsurface isolated vortices",2016,"10.1080/03091929.2015.1135430","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84958998903&doi=10.1080%2f03091929.2015.1135430&partnerID=40&md5=e4b1d740f0276cd2cc54ed4d8afc7e88","Vortex merger is a phenomenon characterizing the whole class of geophysical vortices, from atmospheric storms and large oceanic eddies up to small scale turbulence. Here we focus on the merger of subsurface oceanic anticyclones in an idealized primitive equations model. This study has been motivated by past and recent observations of colliding lens-like anticyclones off of Gibraltar Strait. The critical conditions for merger (critical merger distance and time needed for merger) are determined. We will show that the predictions of classical two-dimensional merger are not verified for subsurface isolated vortices. For instance, critical merger distances will be reduced because of the vortex potential vorticity (PV) structure. The post-merger characteristics of the vortex (radius, extension and PV), are also determined. Merger-related effects, like production of peripheral filaments and small-scale eddies are also investigated and suggest the contribution of merger in both direct and inverse energy cascades. © 2016 Taylor & Francis."
"14631186000;7101727951;","Spectral transformation using a cubed-sphere grid for a three-dimensional variational data assimilation system",2015,"10.1175/MWR-D-14-00089.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943411458&doi=10.1175%2fMWR-D-14-00089.1&partnerID=40&md5=74111c0d49f1745a2073e4ee3b32fbaa","Atmospheric numerical models using the spectral element method with cubed-sphere grids (CSGs) are highly scalable in terms of parallelization. However, there are no data assimilation systems for spectral element numerical models. The authors devised a spectral transformation method applicable to the model data on a CSG (STCS) for a three-dimensional variational data assimilation system (3DVAR). To evaluate the 3DVAR system based on the STCS, the authors conducted observing system simulation experiments (OSSEs) using Community Atmosphere Model with Spectral Element dynamical core (CAM-SE). They observed root-mean-squared error reductions: 24% and 34% for zonal and meridional winds (U and V), respectively; 20% for temperature (T); 4% for specific humidity (Q); and 57% for surface pressure (Ps) in analysis and 28% and 27% for U and V, respectively; 25% for T; 21% for Q; and 31% for Ps in 72-h forecast fields. In this paper, under the premise that the same number of grid points is set, the authors show that the use of a greater polynomial degree, np, produces better performance than use of a greater element count, ne, on equiangular coordinates in terms of the wave representation."
"55802056700;15765007300;","Idealized quasi-biennial oscillations in an ensemble of dry GCM dynamical cores",2015,"10.1175/JAS-D-14-0236.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943392282&doi=10.1175%2fJAS-D-14-0236.1&partnerID=40&md5=dd6a15c3eee0f9764434dd0a51ad6fb0","The paper demonstrates that quasi-biennial oscillation (QBO)-like oscillations can be simulated in an ensemble of dry GCM dynamical cores that are driven by a simple Held-Suarez temperature relaxation and low-level Rayleigh friction. The tropical stratospheric circulations of four dynamical cores, which are options in NCAR's Community Atmosphere Model, version 5 (CAM5), are intercompared. These are the semi-Lagrangian (SLD) and Eulerian (EUL) spectral transform, finite-volume (FV), and spectral element (SE) dynamical cores. The paper investigates how the model design choices impact the wave generation, propagation, and dissipation mechanisms in the equatorial region. SLD, EUL, and SE develop spontaneous QBO-like oscillations in the upper equatorial stratosphere, whereas FV does not sustain the oscillation. Transformed Eulerian-mean (TEM) analyses reveal that resolved waves are the dominant drivers of the QBOs. However, the Eliassen-Palm flux divergence is strongly counteracted by the TEM momentum budget residual, which represents the forcing by diffusion and thermal damping. Interestingly, a reversed Brewer-Dobson circulation accelerates the downward propagation of the SLD's QBO, whereas the EUL's and SE's QBOs are slowed by a mean ascent. Waves are abundant in the SLD's, EUL's, and SE's tropical atmosphere despite the absence of moist convection as a typical wave trigger. Dynamic instabilities are suggested as a wave-triggering mechanism in the troposphere and wave-dissipation process in the stratosphere. In particular, there are indications that the increased occurrences of strongly negative instability indicators in SLD, EUL, and SE are related to more vigorous wave activities and higher magnitudes of the resolved wave forcing in comparison to FV. © 2015 American Meteorological Society."
"16302259500;8750834400;7102322882;6603634026;57216119439;7004480520;","Analytical solution for waves in planets with atmospheric superrotation. II. Lamb, surface, and centrifugal waves",2014,"10.1088/0067-0049/213/1/18","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904336926&doi=10.1088%2f0067-0049%2f213%2f1%2f18&partnerID=40&md5=6e6bf8211647851a313975224a228df2","This paper is the second in a two-part study devoted to developing tools for a systematic classification of the wide variety of atmospheric waves expected on slowly rotating planets with atmospheric superrotation. Starting with the primitive equations for a cyclostrophic regime, we have deduced the analytical solution for the possible waves, simultaneously including the effect of the metric terms for the centrifugal force and the meridional shear of the background wind. In those cases where the conditions for the method of the multiple scales in height are met, these wave solutions are also valid when vertical shear of the background wind is present. A total of six types of waves have been found and their properties were characterized in terms of the corresponding dispersion relations and wave structures. In this second part, we study the waves' solutions when several atmospheric approximations are applied: Lamb, surface, and centrifugal waves. Lamb and surface waves are found to be quite similar to those in a geostrophic regime. By contrast, centrifugal waves turn out to be a special case of Rossby waves that arise in atmospheres in cyclostrophic balance. Finally, we use our results to identify the nature of the waves behind atmospheric periodicities found in polar and lower latitudes of Venus's atmosphere. © 2014. The American Astronomical Society. All rights reserved."
"57214576588;36917877800;","An analytic solution for linear gravity waves in a channel as a test for numerical models using the non-hydrostatic, compressible Euler equations",2013,"10.1002/qj.2105","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890240233&doi=10.1002%2fqj.2105&partnerID=40&md5=c51d3a6412d8bc8b24b0d5d4f9136242","A slightly modified version of the idealized test set-up used by Skamarock and Klemp is proposed: the quasi linear two-dimensional expansion of sound and gravity waves in a flat channel induced by a weak warm bubble. For this test case an exact analytic solution of the linearized compressible, non-hydrostatic Euler equations for a shallow atmosphere has been derived. This solution can be used as a benchmark to assess compressible, non-hydrostatic dynamical cores which are the basis for many of today's, and probably most of the future, atmospheric models. Comparisons and convergence studies of two quite differently designed numerical limited-area simulation models, COSMO and DUNE, against this analytic solution are performed. © 2013 Royal Meteorological Society."
"6504265453;57192430052;","Comparison of a simple 2-D Pluto general circulation model with stellar occultation light curves and implications for atmospheric circulation",2012,"10.1029/2011JE003957","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84861146164&doi=10.1029%2f2011JE003957&partnerID=40&md5=51aa0e939a93e40f2c3ab6ca12b0bc12","We use a simple Pluto general circulation model (sPGCM) to predict for the first time the wind on Pluto and its global, large-scale structure, as well as the temperature and surface pressure. Wind is a fundamental atmospheric variable that has previously been neither measured nor explicitly modeled on Pluto. We ran the sPGCM in 2-D mode (latitude, height, and time varying) using the Massachusetts Institute of Technology general circulation model dynamical core, a simple radiative-convective scheme, and no frost cycle. We found that Pluto's atmosphere is dynamically active in the zonal direction with high-speed, high-latitude jets that encircle the poles in gradient wind balance and prograde with Pluto's rotation. The meridional and vertical winds do not show evidence for a Hadley cell (or other large-scale structure) due to the low-altitude temperature inversion. The horizontal variation in surface pressure is a small fraction of the previously derived interannual variation in surface pressure. The simple general circulation model output was validated with stellar occultation light curve data from the years 1988, 2002, 2006, and 2007. For 2006 and 2007, the best fit global mean surface pressure was 24 microbar, in 2002 it was 22 microbar, and in 1988 it was 12 microbar (1 microbar error bars). For all years the methane mixing ratio was 1% (0.2% error bars). This work is a first step for future Pluto, Triton, and Kuiper Belt object atmosphere general circulation models that will also include longitudinal variations and a volatile cycle. Copyright 2012 by the American Geophysical Union."
"55217594200;38362516500;8869357700;36939938600;54421396700;54421344300;","Numerical study of the barotropic responses to a rapidly moving typhoon in the East China Sea",2011,"10.1007/s10236-011-0436-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-81255185565&doi=10.1007%2fs10236-011-0436-1&partnerID=40&md5=06746e967910d0129bb59df5ed106943","Barotropic responses of the East China Sea to typhoon KOMPASU are investigated using a highresolution, three-dimensional, primitive equation, and finite volume coastal ocean model. Even the fact that the typhoon KOMPASU only brushed across the brink of China mainland without landing, it still imposed great influence across China's east coastal area, where storm surges ranging from 35 to 70 cm were intrigued during this event and a large wake of water setdown due to the outward radial transport driven by the cyclonic wind stress was generated after the KOMPASU traveled across the Yellow Sea. Analysis of the numerical results reveals that the barotropic waves propagating along the coast after the typhoon's landing can be identified as Kelvin wave and the currents associated with the storm are geostrophic currents. A series of model runs are initiated to diagnose the effects of wind stress, atmospheric pressure, and storm track variation on the surge's spatial distribution in the East China Sea. The barotropic waves affected by the atmospheric disturbance due to the typhoon in deep Pacific Ocean travel far more rapidly, arriving at the coastal regions at least 60 h ahead of the typhoon. The wave amplitudes are merely 0.2-0.4 cm and damp gradually due to friction. The model experiments also confirm that the surge levels in nearshore regions are highly dominated by winds, whereas the water level variations in deeper areas are controlled by the atmospheric pressure forcing during typhoon events in the East China Sea. © 2011 Springer-Verlag."
"8618667100;6603137309;","Resonant wave interactions in the presence of a diurnally varying heat source",2009,"10.1175/2009JAS2899.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-73549084979&doi=10.1175%2f2009JAS2899.1&partnerID=40&md5=e0c345394768aabf66c728deea922337","Resonant interactions among equatorial waves in the presence of a diurnally varying heat source are studied in the context of the diabatic version of the equatorial β-plane primitive equations for a motionless, hydrostatic, horizontally homogeneous and stably stratified background atmosphere. The heat source is assumed to be periodic in time and of small amplitude [i.e., O(ε)] and is prescribed to roughly represent the typical heating associated with deep convection in the tropical atmosphere. In this context, using the asymptotic method of multiple time scales, the free linear Rossby, Kelvin, mixed Rossby-gravity, and inertiogravity waves, as well as their vertical structures, are obtained as leading-order solutions. These waves are shown to interact resonantly in a triad configuration at the O(ε) approximation, and the dynamics of these interactions have been studied in the presence of the forcing. It is shown that for the planetary-scale wave resonant triads composed of two first baroclinic equatorially trapped waves and one barotropic Rossby mode, the spectrum of the thermal forcing is such that only one of the triad components is resonant with the heat source. As a result, to illustrate the role of the diurnal forcing in these interactions in a simplified fashion, two kinds of triads have been analyzed. The first one refers to triads composed of a k=0 first baroclinic geostrophic mode, which is resonant with the stationary component of the diurnal heat source, and two dispersive modes, namely, a mixed Rossby-gravity wave and a barotropic Rossby mode. The other class corresponds to triads composed of two first baroclinic inertio-gravity waves in which the highest-frequency wave resonates with a transient harmonic of the forcing. The integration of the asymptotic reduced equations for these selected resonant triads shows that the stationary component of the diurnal heat source acts as an ""accelerator"" for the energy exchanges between the two dispersive waves through the excitation of the catalyst geostrophic mode. On the other hand, since in the second class of triads the mode that resonates with the forcing is the most energetically active member because of the energy constraints imposed by the triad dynamics, the results show that the convective forcing in this case is responsible for a longer time scale modulation in the resonant interactions, generating a period doubling in the energy exchanges. The results suggest that the diurnal variation of tropical convection might play an important role in generating lowfrequency fluctuations in the atmospheric circulation through resonant nonlinear interactions. © 2009 American Meteorological Society."
"6602084752;20733898400;","Stability and accuracy of the physics - Dynamics coupling in spectral models",2007,"10.1002/qj.119","https://www.scopus.com/inward/record.uri?eid=2-s2.0-35548950627&doi=10.1002%2fqj.119&partnerID=40&md5=1d2f30e8ac0a43b3ed7c14fc6ba0d7bd","This article first reviews the existing spectral time-step organizations of the Integrated Forecast System (IFS) of the ECMWF and the ARPEGE/ ALADIN/AROME models of Météo-France and the ALADIN partners. They are characterized according to four choices concerning the physics - dynamics coupling: (1) the order in which the physics parametrization and the dynamics are called and coupled inside the time-step computation, (2) the space-time location of the physics coupling on the semi-Lagrangian trajectory, (3) parallel or sequential time stepping of the different physics parametrizations and (4) parallel or sequential physics - dynamics coupling. It is found that according to this classification, IFS on the one hand and the ARPEGE/ALADIN/AROME models on the other hand exhibit two distinct structures. In the models, the dynamical cores of the semi-implicit semi-Lagrangian two-time-level schemes are linearized around a stationary reference state. This state differs from the real atmospheric state (i.e. the exact solution of the equations). This article generalizes the framework introduced by Staniforth, Wood and Côté to study the relation between the coupled physics parametrization and such reference and atmospheric states. Subsequently, the two above-mentioned time-step organizations are translated into this simplified frame. Extra degrees of freedom are added to allow for obvious improvements of the existing spectral time-step organizations. In order to deal with the complexity of the emerging structures and to avoid tedious algebraic manipulations, a numerical methodology is proposed to characterize their properties. This framework is then used to make a comparative study of the numerical stability and the accuracy of the physics - dynamics coupling within the two above-mentioned time-step organizations. Potential improvements are briefly discussed. Copyright © 2007 Royal Meteorological Society."
"57203109046;","Generalized Hough modes: The structure of damped global-scale waves propagating on a mean flow with horizontal and vertical shear",2005,"10.1175/JAS3500.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-26244457766&doi=10.1175%2fJAS3500.1&partnerID=40&md5=707e1eeaac05509aeae66b0fc879710e","The technique of classical tidal theory in which linear disturbances to a background flow at rest are expanded in terms of Hough modes is generalized for damped disturbances to a general zonal mean state under the assumption that the vertical scale of the background flow is longer than the vertical scale of the disturbance. Generalized Hough modes provide an alternative to the concept of mode coupling between classical modes as a means of describing how the mean flow and damping affect the wave structure. Generalized modes take into account the horizontal shear of the mean flow and damping at lowest order. Effects of vertical shear in the mean flow only arise as first-order corrections, and hence generalized modes provide exact modal solutions to the linearized primitive equations when the mean flow only varies with latitude. © 2005 American Meteorological Society."
"6603710209;7003594013;","Modelling the 3-D carbon flux across the Iberian margin during the upwelling season in 1998",2001,"10.1016/S0079-6611(01)00080-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035688687&doi=10.1016%2fS0079-6611%2801%2900080-5&partnerID=40&md5=882e801f472100ede412e106c0ee7691","A 3-dimensional (3-D) primitive equation model coupled to a biological model was used to study the effects of physics on the productivity and carbon export along the Iberian coast during the upwelling season (May-September). Open boundaries for this model were generated with a basin scale model covering major parts of the North Atlantic and nested in two steps into models with grid resolutions of 10 and 3.3km, respectively. The ecosystem model consists of eight state variables (nitrate, ammonium, silicate, diatoms, flagellates, meso- and microzooplankton, fast and slow sinking detritus) and assumes that nitrogen and silicate are the potential limiting nutrients. The primitive equation models produced coastal upwelling that injects nutrients into the euphotic zone in response to northerly wind forcing. Filaments were formed when the upwelling favourable wind peaked in July/August. High primary production was found on the shelf and in the core of the upwelling filaments. The simulations used atmospheric input from 1998 allowing comparison with a Lagrangian experiment in August 1998. The ecological model, having the same structure as a model been applied on boreal shelves, gave good simulations of the carbon flux on and off the Iberian margin. However, some stocks and rates of carbon were not well validated with the data from the field investigation. The simulated net export of carbon from May to September across the 400km long, 200m isobath is estimated to be 4.4×1011gC or 6.3mgC m-2.s-1. © 2001 Elsevier Science Ltd. All rights reserved."
"7202364010;55463815300;","ENSO surface winds in CCM3 simulation: Diagnosis of errors",2000,"10.1175/1520-0442(2000)013<3172:ESWICS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034277741&doi=10.1175%2f1520-0442%282000%29013%3c3172%3aESWICS%3e2.0.CO%3b2&partnerID=40&md5=971b69c75a908ad7bf4a650e43915404","The structure of surface-wind anomalies associated with ENSO variability is extracted from Comprehensive Ocean-Atmosphere Dataset observations and European Centre for Medium-Range Forecasts (ECMWF) and National Centers for Environmental Prediction (NCEP) reanalyses, along with estimates of uncertainty. The targets are used to evaluate ENSO surface winds produced by the National Center for Atmospheric Research's atmospheric GCM known as the Community Climate Model, version 3 (CCM3), when integrated in the climate-simulation mode. Simulated anomalies have stronger easterlies in the off-equatorial Tropics and stronger equatorward flow in the Pacific than any of the observational estimates do. CCM3's wind departures are found to be large when compared with the difference of the reanalysis anomalies and should thus be considered to be errors. In a companion paper, the authors make a compelling case for the presence of robust errors in CCM3's ENSO heating distribution, based on comparisons with the residually diagnosed heating anomalies from ECMWF and NCEP reanalyses. The linkage between specific features of CCM3's surface-wind and heating errors is investigated using a steady, linear, global, primitive equation model (18 vertical σ levels, 30 zonal waves, and latitude spacing of 2.5°). Diagnostic modeling indicates that stronger equatorward flow in the Pacific results largely from excessive diabatic cooling in the off-equatorial Tropics, a key heating error linked to a more meridional redistribution of ENSO heating in CCM3. The 'bottom-heavy' structure of CCM3's equatorial heating anomalies, on the other hand, is implicated in the generation of zonal-wind errors in the central and eastern tropical Pacific. In the diagnostic simulation of CCM3's ENSO variability, the longwave heating anomalies, with peak values near 850 mb, contribute as much to surface zonal winds as do all other heating components together-a novel finding, needing corroboration. This study, along with the companion paper, illustrates the dynamical diagnosis strategy-of circulation and forcing intercomparisons with observed counterparts, followed by diagnostic modeling-for analyzing errors in the GCM's simulation of climate variability.The structure of surface-wind anomalies associated with ENSO variability is extracted from Comprehensive Ocean-Atmosphere Dataset observations and European Centre for Medium-Range Forecasts (ECMWF) and National Centers for Environmental Prediction (NCEP) reanalyses, along with estimates of uncertainty. The targets are used to evaluate ENSO surface winds produced by the National Center for Atmospheric Research's atmospheric GCM known as the Community Climate Mode, version 3 (CCM3), when integrated in the climate-simulation mode. Simulated anomalies have stronger easterlies in the off-equatorial Tropics and stronger equatorward flow in the Pacific than any of the observational estimate do. CCM3's wind departures are found to be large when compared with the difference of the reanalysis anomalies and should thus be considered to be errors. In a companion paper, the authors make a compelling case for the presence of robust errors in CCM3's ENSO heating distribution, based on comparisons with the residually diagnosed heating anomalies from ECMWF and NCEP reanalyses. The linkage between specific features of CCM3's surface-wind and heating errors is investigated using a steady, linear, global, primitive equation model (18 vertical σ levels, 30 zonal waves, and latitude spacing of 2.5°). Diagnostic modeling indicates that stronger equatorward flow in the Pacific results largely from excessive diabatic cooling in the off-equatorial Tropics, a key heating error linked to a more meridional redistribution of ENSO heating in CCM3. The 'bottom-heavy' structure of CCM3's equatorial heating anomalies, on the other hand, is implicated in the generation of zonal-wind errors in the central and eastern tropical Pacific. In the diagnostic simulation of CCM3's ENSO variability, the longwave heating anomalies, with peak values near 850 mb, contribute as much to surface zonal winds as do all other heating components together-a novel finding, needing corroboration. This study, along with the companion paper, illustrates the dynamical diagnosis strategy-of circulation and forcing intercomparisons with observed counterparts, followed by diagnostic modeling-for analyzing errors in the GCM's simulation of climate variability."
"6701439242;7102836087;","The semi-geostrophic diagnosis of vertical motion. I: Formulation and coordinate transformations",1999,"10.1002/qj.1999.49712555607","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032810255&doi=10.1002%2fqj.1999.49712555607&partnerID=40&md5=78af5a6efc0ab88b29e698160d4b08ae","Theoretical considerations suggest that the semi-geostrophic (SG) omega equation should provide a more accurate diagnosis of vertical velocity than the classical quasi-geostrophic (QG) omega equation in the presence of significant horizontal variations in static stability and potential vorticity. Only very few previous studies have compared the performance of the two methods applied to either real or simulated data. Furthermore, it is almost certain that such comparisons have been affected by uncertainties associated with transformations between physical and geostrophic momentum (GM) coordinates, these being necessary in order to solve the SG omega equation in a form which retains the conceptual simplicity of the QG omega equation. Here we describe an accurate method of mapping between physical and GM coordinates which is suitable for operating on a large, discrete data base. The result of an inverse mapping is used to measure the accuracy of the method. This is shown to be sensitive to the chosen grid-point resolution in GM space, which may need to be considerably greater than the given resolution in physical space in order to resolve dynamically significant features in regions of negative geostrophic shear. The SG equations do not apply when the Jacobian of the GM coordinate transformation (J) changes sign within the domain of the analysis. If such a situation occurs with real data then it is necessary to apply an adjustment to the sampled geopotential (or pressure) data, in order to satisfy the condition J > 0 everywhere prior to a SG diagnosis of vertical velocity. A variational approach to this problem is described and tested using data generated by a primitive-equation model of a developing cyclone."
"7102054073;","Some aspects of the sensitivity of stratospheric climate simulation to model lid height",1997,"10.1029/97jd01771","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000172722&doi=10.1029%2f97jd01771&partnerID=40&md5=1271c6a1c4e34e7bf3a1aadb5d5df27a","Two ensembles of simulations of the middle atmosphere are compared for early northern hemisphere winter. The two ensembles differ only in the position of the model lid (80 km or 96 km). Two sets of comparisons are carried out using a primitive equation mechanistic model; the first uses Rayleigh friction in the mesosphere to mimic the effect of gravity waves, and the second uses the Hines gravity wave parameterization. Simulations which use Rayleigh friction are found to show little climatic sensitivity to the position of the lid. Simulations which use the Hines parameterization are shown to be very sensitive to the position of the lid, and this sensitivity is seen directly up to six scale heights below the lid. Indirect effects may extend throughout the middle atmosphere. This sensitivity is believed to be due to real circulation changes and not any numerical artifacts resulting from reflections from the model lid."
"7103180783;7102367341;","The effect of barotropic shear on baroclinic instability Part I: Normal mode problem",1997,"10.1016/S0377-0265(96)00471-X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030961644&doi=10.1016%2fS0377-0265%2896%2900471-X&partnerID=40&md5=bd1a281b6050e154198a4ac1aad22f92","The effect of barotropic shear in the basic flow on baroclinic instability is investigated using a linear multilevel quasi-geostrophic β-plane channel model and a nonlinear spherical primitive equation model. Barotropic shear has a profound effect on baroclinic instability. It reduces the growth rates of normal modes by severely restricting their structure, confirming earlier results with a two-layer model. Dissipation, in the form of Ekman pumping and Newtonian cooling, does not change the main characteristics of the effect of the shear on normal mode instability. Barotropic shear in the basic state, characterized by large shear vorticity with small horizontal curvature, also affects the nonlinear development of baroclinic waves. The shear limits the energy conversion from the zonal available potential energy to eddy energy, reducing the maximum eddy kinetic energy level reached by baroclinic waves. Barotropic shear, which controls the level of eddy activity, is a major factor which should be considered when parameterizing the eddy temperature and momentum fluxes induced by baroclinic waves in a climate model."
"6602794611;7004512139;7004013012;","Modeling North Pacific SST anomalies as a response to anomalous atmospheric forcing",1990,"10.1016/0924-7963(90)90204-N","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025668226&doi=10.1016%2f0924-7963%2890%2990204-N&partnerID=40&md5=93fcb8fbbe8cc2a2cb90129f3917f83e","Large-scale sea surface temperature anomalies (SSTA) in the North Pacific ocean are often persistent for several months during wintertime. There is observational evidence that these patterns are forced by anomalous atmospheric circulation. Since the latter is in part related to the tropical El Niño/Southern Oscillation (ENSO) phenomenon it is hypothesized that part of the North Pacific SSTA's may be interpreted as remote oceanic response to anomalous equatorial Pacific SSTA's. Two experiments with a multi-level primitive equation model of the North Pacific have been conducted to study the influence of such anomalous atmospheric circulation on the SST. In both experiments anomalous wind stress as derived from the 1950-1979 COADS subset is specified as anomalous forcing. In experiment 1 no anomalous heat flux is introduced whereas in experiment 2 anomalous heat fluxes are estimated from anomalous surface winds and a simple advective atmosphere. In both experiments the GCM SSTA response are able to reproduce the main features of the time series of observed SSTA, in particular in winter. In experiment 1, however, the magnitudes are systematically too low. The addition of anomalous heat fluxes in experiment 2 significantly improves the simulation. The ENSO signal is clearly present in both simulations. © 1990."
"7006705919;","Toward atmospheres without tops: Absorbing upper boundary conditions for numerical models",1986,"10.1002/qj.49711247415","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983962270&doi=10.1002%2fqj.49711247415&partnerID=40&md5=90fc6904f2372c6e52f2f48c38e98784","The appropriate upper boundary condition (UBC) formulation for the dynamical equations used in atmospheric physics is discussed in terms of both theoretical and computational aspects. The previous work on the UBC formulation is reviewed in the context of a linear mid‐latitude primitive equation (PE) model. A new technique for constructing the UBC is introduced. The technique depends upon the existence of analytic solutions to simplifications to the equations of motion. These analytic solutions are used to construct the exact radiation UBCs (often used in tidal theory and studies of the upper atmosphere) which are non‐local in time and space. Approximate UBCs, which are local in time, are formed through rational approximations to the exact radiation UBCs. The technique is demonstrated to be effective for both Rossby and gravity modes. The UBC is tested for computational problems initially in the linear PE model, and subsequently in a forced, damped nonlinear quasi‐geostrophic model. Copyright © 1986 Royal Meteorological Society"
"7801489016;7201772478;","A numerical study of the development mechanisms of polar lows",1985,"10.1111/j.1600-0870.1985.tb00444.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977723271&doi=10.1111%2fj.1600-0870.1985.tb00444.x&partnerID=40&md5=7cddb913da2c67904082ad9c96fdac4d","Two well‐documented polar lows, one occurring in the Atlantic Ocean and the other in the Pacific Ocean, are modeled numerically. These numerical results are compared with our analytic results in order to determine how the effects of nonlinearity and more complete physics may modify our tentative conclusions. The numerical model used in this study is The Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR), three‐dimensional (3‐D) primitive equation mesoscale model with a high‐resolution planetary boundary‐layer parameterization and moist physics. A prediction equation for ground temperature takes into account the existence of variable surface parameters such as albedo, emissivity, thermal inertia. roughness and moisture availability. The Atlantic polar low developed in a shallow but intense baroclinic zone in the Denmark Strait region during the first 24 h of the forecast period. Sensitivity studies with the 3‐D model revealed that the baroclinity was sufficient to allow realistic development while the polar low was in the vicinity of this baroclinic zone. However, both convective and non‐convective latent heating and the surface fluxes of sensible and latent heat were necessary for the simulation of observed development after this polar low departed from this baroclinic zone and entered the Norwegian Sea. The fact that convective and non‐convective latent heating were both essential for simulating the observed development of the Atlantic polar low is consistent with previous analytic‐model results. Like the Atlantic polar low, the Pacific polar low developed in an intense baroclinic zone, but this baroclinic zone was deep. Sensitivity studies revealed that baroclinity in conjunction with only non‐convective latent heating, overdeveloped the polar low, unlike the analytic results. It was only through the use of the convective parameterization and the convective heating profile that correct development of the simulated Pacific polar low resulted. Surface fluxes played little role in this development. Thus, moist baroclinity and CISK (conditional instability of the second kind) were both important to the observed development of both the Atlantic and Pacific polar lows. 1985 Blackwell Munksgaard"
"7403947790;7004818189;","A linear analysis of the transition curve for the baroclinic annulus.",1983,"10.1175/1520-0469(1983)040<2293:ALAOTT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020969799&doi=10.1175%2f1520-0469%281983%29040%3c2293%3aALAOTT%3e2.0.CO%3b2&partnerID=40&md5=eb7f37f207076af4977bdbeca0ab1562","A rotating cylindrical annulus of an incompressible fluid with horizontal density gradients is studied by the use of numerical models. These states are tested for stability to nonaxisymmetric perturbations by the use of a model based upon the linearized hydrostatic primitive equations. The results include a prediction of the transition curve, the curve separating axisymmetric flow and nonaxisymmetric flow. This predicted curve is very close to that observed in the laboratory. -from Authors"
"6603463226;6701762060;","Inclusion of sensible heating in convective parameterization applied to lake-effect snow.",1979,"10.1175/1520-0493(1979)107<0551:IOSHIC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0018675967&doi=10.1175%2f1520-0493%281979%29107%3c0551%3aIOSHIC%3e2.0.CO%3b2&partnerID=40&md5=ee3a3c3504ca7fdf6e49110fd3ad7c45","A method has been designed for including the surface fluxes of water vapor and sensible heat from water surfaces in a convective parameterization scheme for a primitive equation numerical model of the atmosphere. The grid size is 48km. Application of the model to Lake Huron and vicinity in the simulation of 3 lake-effect storm cases resulted in predictions of vertical transport of heat and moisture and the consequent alteration of air mass properties, as well as precipitation. The maximum grid-square average observed precipitation over 6h was 0.75, 0.86 and 0.54cm for the 3 cases. These values may be compared to maximum predicted values for those grid squares where observations were available. The predicted maxima were 0.60, 0.76 and 0.57cm, respectively. The model was also employed to isolate the various physical influences on precipitation. While model results were not clear-cut, they indicated that for near-lake points, heat and moisture from the lake were the principal causes of precipitation. Orographic lift and shoreline frictional convergence appeared to be secondary factors. -Authors"
"57190242570;57190237768;","A case study of frontal behaviour using a 10‐level primitive equation model",1970,"10.1002/qj.49709640811","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0040291427&doi=10.1002%2fqj.49709640811&partnerID=40&md5=e0c76c0f088a59ce31212ce23fb22040","The predicted air motion and precipitation patterns obtained from a 10‐level primitive equation model of the atmosphere are presented for comparison with the observed patterns analysed by isentropic and Doppler radar techniques for the same occasion by Browning and Harrold (1969). There is considerable agreement over the scales of motion which it is possible to predict using the model though it is possible that further refinement in the handling of friction and topography and of the cloud physics can improve the predicted overall large‐scale distribution of rainfall. Copyright © 1970 Royal Meteorological Society"
"6603822174;36088682200;35733801500;57194348549;","Vorticity-divergence semi-Lagrangian global atmospheric model SL-AV20: Dynamical core",2017,"10.5194/gmd-10-1961-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85019666238&doi=10.5194%2fgmd-10-1961-2017&partnerID=40&md5=3b5f9476042e50fccc565649f9fab38c","SL-AV (semi-Lagrangian, based on the absolute vorticity equation) is a global hydrostatic atmospheric model. Its latest version, SL-AV20, provides global operational medium-range weather forecast with 20gkm resolution over Russia. The lower-resolution configurations of SL-AV20 are being tested for seasonal prediction and climate modeling. <br><br> The article presents the model dynamical core. Its main features are a vorticity-divergence formulation at the unstaggered grid, high-order finite-difference approximations, semi-Lagrangian semi-implicit discretization and the reduced latitude-longitude grid with variable resolution in latitude. <br><br> The accuracy of SL-AV20 numerical solutions using a reduced lat-lon grid and the variable resolution in latitude is tested with two idealized test cases. Accuracy and stability of SL-AV20 in the presence of the orography forcing are tested using the mountain-induced Rossby wave test case. The results of all three tests are in good agreement with other published model solutions. It is shown that the use of the reduced grid does not significantly affect the accuracy up to the 25g% reduction in the number of grid points with respect to the regular grid. Variable resolution in latitude allows us to improve the accuracy of a solution in the region of interest. © Author(s) 2017. CC Attribution 3.0 License."
"55623053700;16073249900;7402525425;","Quantifying the incoherent M2 internal tide in the Philippine sea",2016,"10.1175/JPO-D-16-0023.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982245375&doi=10.1175%2fJPO-D-16-0023.1&partnerID=40&md5=8b89af81635390f0248f39dc04a8ae3a","The baroclinic tides are a crucial source of mixing energy into the deep ocean; however, the incoherent portion of the spectrum is not well examined because it is difficult to observe. This study estimates the coherent and incoherent M2 internal tide energy fluxes in the Philippine Sea using a primitive equation model that resolves the M2 barotropic and baroclinic tides and the time-evolving atmospherically forced eddying circulation. A time-mean, incoherent, internal tide energy flux of 25% of the coherent energy flux is found to emanate eastward into the Philippine Sea from the Luzon Strait and a time-mean incoherent portion of 30% of the coherent energy flux propagates westward into the South China Sea (SCS). The incoherent internal tide energy results from baroclinic tide generation and propagation variability. Quantifying the incoherent portion estimates the energy missing from altimeter-derived or line-integral acoustic measurements and places short-lived, in situ observations in the context of variability. © 2016 American Meteorological Society."
"6602702740;56828803500;14623838400;","Modeling Black Sea circulation with high resolution in the coastal zone",2016,"10.1134/S0001433816030142","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977109135&doi=10.1134%2fS0001433816030142&partnerID=40&md5=06bf39bbd5082ea03ecaddf6a4a3b1cc","We present a numerical model of Black Sea circulation based on primitive equations with improved spatial resolution in the coastal zone. The model equations are formulated in a two-pole orthogonal coordinate system with arbitrary locations of the poles and a vertical σ coordinate. Increased horizontal resolution is gained by displacing the pole into the vicinity of the separated subdomain. The problem is solved over a grid with a variable step. The northern coordinate pole is displaced to the vicinity of Gelendzhik; the grid step varies from 150 m in the coastal zone to 4.6 km in the main basin. We simulated the fields of currents, sea level, temperature, and salinity under the given atmospheric forcing in 2007. The model is capable of reproducing the large-scale Black Sea circulation and submesoscale variations in the coastal currents. © 2016, Pleiades Publishing, Ltd."
"56900961900;15765007300;","A moist aquaplanet variant of the Held-Suarez test for atmospheric model dynamical cores",2016,"10.5194/gmd-9-1263-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84964339312&doi=10.5194%2fgmd-9-1263-2016&partnerID=40&md5=48f3b3a302687bb37bc6e73e98798b72","A moist idealized test case (MITC) for atmospheric model dynamical cores is presented. The MITC is based on the Held-Suarez (HS) test that was developed for dry simulations on a flat Earth and replaces the full physical parameterization package with a Newtonian temperature relaxation and Rayleigh damping of the low-level winds. This new variant of the HS test includes moisture and thereby sheds light on the nonlinear dynamics-physics moisture feedbacks without the complexity of full-physics parameterization packages. In particular, it adds simplified moist processes to the HS forcing to model large-scale condensation, boundary-layer mixing, and the exchange of latent and sensible heat between the atmospheric surface and an ocean-covered planet. Using a variety of dynamical cores of the National Center for Atmospheric Research (NCAR)'s Community Atmosphere Model (CAM), this paper demonstrates that the inclusion of the moist idealized physics package leads to climatic states that closely resemble aquaplanet simulations with complex physical parameterizations. This establishes that the MITC approach generates reasonable atmospheric circulations and can be used for a broad range of scientific investigations. This paper provides examples of two application areas. First, the test case reveals the characteristics of the physics-dynamics coupling technique and reproduces coupling issues seen in full-physics simulations. In particular, it is shown that sudden adjustments of the prognostic fields due to moist physics tendencies can trigger undesirable large-scale gravity waves, which can be remedied by a more gradual application of the physical forcing. Second, the moist idealized test case can be used to intercompare dynamical cores. These examples demonstrate the versatility of the MITC approach and suggestions are made for further application areas. The new moist variant of the HS test can be considered a test case of intermediate complexity. © Author(s) 2016."
"55758816800;7004689241;","Offshore transport of shelf water by deep-ocean eddies",2016,"10.1175/JPO-D-16-0085.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85006483333&doi=10.1175%2fJPO-D-16-0085.1&partnerID=40&md5=fbc2b6d28e822d72094796c4b23a5b6e","At continental margins, energetic deep-ocean eddies can transport shelf water offshore in filaments that wrap around the eddy. One example is that of Gulf Stream warm-core rings interacting with the Mid-Atlantic Bight shelf. The rate at which shelf water is exported in these filaments is a major unknown in regional budgets of volume, heat, and salt. This unknown transport is constrained using a series of idealized primitive equation numerical experiments wherein a surface-intensified anticyclonic eddy interacts with idealized shelf-slope topography. There is no shelfbreak front in these experiments, and shelf water is tracked using a passive tracer. When anticyclones interact with shelf-slope topography, they suffer apparent intrusions of shelf-slope water, resulting in a subsurface maximum in offshore transport. The simulations help construct an approximate model for the filament of exported water that originates inshore of any given isobath. This model is then used to derive an expression for the total volume of shelf-slope water transported by the eddy across that isobath. The transport scales with water depth, radius, and azimuthal velocity scale of the eddy. The resulting expression can be used with satellite-derived eddy properties to estimate approximate real-world transports ignoring the presence of a shelfbreak front. The expression assumes that the eddy's edge is at the shelf break, a condition not always satisfied by real eddies."
"36154754400;15765007300;52263850600;7005087624;","Potential vorticity: Measuring consistency between GCM dynamical cores and tracer advection schemes",2015,"10.1002/qj.2389","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928300858&doi=10.1002%2fqj.2389&partnerID=40&md5=67e34ab2be306e654189e80350b2821c","Ertel's potential vorticity (PV) is used as a diagnostic tool to give a direct comparison between the treatment of PV in the dynamics and the integration of PV as a passive tracer, yielding a systematic evaluation of a model's consistency between the dynamical core's integration of the equations of motion and its tracer transport algorithm. Several quantitative and qualitative metrics are considered to measure the consistency, including error norms and grid-independent probability density functions. Comparisons between the four dynamical cores of the National Center for Atmospheric Research's (NCAR) Community Atmosphere Model version 5.1 (CAM) are presented. We investigate the consistency of these dynamical cores in an idealized setting: the presence of a breaking baroclinic wave. For linear flow, before the wave breaks, the consistency for each model is good. As the flow becomes nonlinear, the consistency between dynamic PV and tracer PV breaks down, especially at small scales. Large values of dynamic PV are observed that do not appear in the tracer PV. The results indicate that the spectral-element (CAM-SE) dynamical core is the most consistent of the dynamical cores in CAM, however the consistency between dynamic PV and tracer PV is related to and sensitive to the diffusive properties of the dynamical cores. © 2014 Royal Meteorological Society."
"44561454300;7403535713;57209592626;36089189400;8317451600;6602380901;","Intercomparison of general circulation models for hot extrasolar planets",2014,"10.1016/j.icarus.2013.11.027","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84890285686&doi=10.1016%2fj.icarus.2013.11.027&partnerID=40&md5=7487d27f88a7f746f37a87f654f18f2e","We compare five general circulation models (GCMs) which have been recently used to study hot extrasolar planet atmospheres (BOB, CAM, IGCM, MITgcm, and PEQMOD), under three test cases useful for assessing model convergence and accuracy. Such a broad, detailed intercomparison has not been performed thus far for extrasolar planets study. The models considered all solve the traditional primitive equations, but employ different numerical algorithms or grids (e.g., pseudospectral and finite volume, with the latter separately in longitude-latitude and 'cubed-sphere' grids). The test cases are chosen to cleanly address specific aspects of the behaviors typically reported in hot extrasolar planet simulations: (1) steady-state, (2) nonlinearly evolving baroclinic wave, and (3) response to fast timescale thermal relaxation. When initialized with a steady jet, all models maintain the steadiness, as they should-except MITgcm in cubed-sphere grid. A very good agreement is obtained for a baroclinic wave evolving from an initial instability in pseudospectral models (only). However, exact numerical convergence is still not achieved across the pseudospectral models: amplitudes and phases are observably different. When subject to a typical 'hot-Jupiter'-like forcing, all five models show quantitatively different behavior-although qualitatively similar, time-variable, quadrupole-dominated flows are produced. Hence, as have been advocated in several past studies, specific quantitative predictions (such as the location of large vortices and hot regions) by GCMs should be viewed with caution. Overall, in the tests considered here, pseudospectral models in pressure coordinate (PEBOB and PEQMOD) perform the best and MITgcm in cubed-sphere grid performs the worst. © 2013 Elsevier Inc."
"31067496800;10039602000;","The Flux-Form Semi-Lagrangian Spectral Element (FF-SLSE) method for tracer transport",2014,"10.1002/qj.2184","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84899492346&doi=10.1002%2fqj.2184&partnerID=40&md5=6a2ec79ffa05d4ae8ab70d9593c348fe","The spectral element dynamical core has been demonstrated to be an accurate and scalable approach for solving the equations of motion in the atmosphere. However, it is also known that use of the spectral element method for tracer transport is costly and requires substantial parallel communication over a single time step. Consequently, recent efforts have turned to finding alternative transport schemes which maintain the scalability of the spectral element method without its significant cost. This article proposes a conservative semi-Lagrangian approach for tracer transport which uses upstream trajectories to solve the transport equation on the native spectral element grid. This formulation, entitled the Flux-Form Semi-Lagrangian Spectral Element (FF-SLSE) method, is highly accurate compared to many competing schemes, allows for large time steps, and requires fewer parallel communications over the same time interval than the spectral element method. In addition, the approach guarantees local conservation and is easily paired with a filter which can be used to ensure positivity. This article presents the dispersion relation for the 1D FF-SLSE approach and demonstrates stability up to a Courant number of 2.44 with cubic basis. Several standard numerical tests are presented for the method in 2D to verify correctness, accuracy and robustness of the method, including a new test of a divergent flow in Carteisan geometry. © 2013 Royal Meteorological Society."
"8922308700;15755995900;34772240500;55544607500;7006705919;57193213111;","The Separate Physics and Dynamics Experiment (SPADE) framework for determining resolution awareness: A case study of microphysics",2013,"10.1002/jgrd.50711","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885132718&doi=10.1002%2fjgrd.50711&partnerID=40&md5=81b9c7328149643138efa88c2470dc0c","Multiresolution dynamical cores for weather and climate modeling are pushing the atmospheric community toward developing scale aware or, more specifically, resolution aware parameterizations that function properly across a range of grid spacings. Determining resolution dependence of specific model parameterizations is difficult due to resolution dependencies in many model components. This study presents the Separate Physics and Dynamics Experiment (SPADE) framework for isolating resolution dependent behavior of specific parameterizations without conflating resolution dependencies from other portions of the model. To demonstrate SPADE, the resolution dependence of theMorrison microphysics, from the Weather Research and Forecasting model, and the Morrison-Gettelman microphysics, from the Community Atmosphere Model, are compared for grid spacings spanning the cloud modeling gray zone. It is shown that the Morrison scheme has stronger resolution dependence than Morrison-Gettelman, and the partial cloud fraction capability of Morrison-Gettelman is not the primary reason for this difference. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union."
"37104438900;57204253860;7005877775;","Radiative heating of the ISCCP upper level cloud regimes and its impact on the large-scale tropical circulation",2013,"10.1002/jgrd.50114","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884237543&doi=10.1002%2fjgrd.50114&partnerID=40&md5=e8a21dd2ce175104475b7a2035a05a31","Radiative heating profiles of the International Satellite Cloud Climatology Project (ISCCP) cloud regimes (or weather states) were estimated by matching ISCCP observations with radiative properties derived from cloud radar and lidar measurements from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) sites at Manus, Papua New Guinea, and Darwin, Australia. Focus was placed on the ISCCP cloud regimes containing the majority of upper level clouds in the tropics, i.e., mesoscale convective systems (MCSs), deep cumulonimbus with cirrus, mixed shallow and deep convection, and thin cirrus. At upper levels, these regimes have average maximum cloud occurrences ranging from 30% to 55% near 12 km with variations depending on the location and cloud regime. The resulting radiative heating profiles have maxima of approximately 1 K/day near 12 km, with equal heating contributions from the longwave and shortwave components. Upper level minima occur near 15 km, with the MCS regime showing the strongest cooling of 0.2 K/day and the thin cirrus showing no cooling. The gradient of upper level heating ranges from 0.2 to 0.4 K/(daykm), with the most convectively active regimes (i.e., MCSs and deep cumulonimbus with cirrus) having the largest gradient. When the above heating profiles were applied to the 25-year ISCCP data set, the tropics-wide average profile has a radiative heating maximum of 0.45Kday-1 near 250 hPa. Column-integrated radiative heating of upper level cloud accounts for about 20% of the latent heating estimated by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). The ISCCP radiative heating of tropical upper level cloud only slightly modifies the response of an idealized primitive equation model forced with the tropics-wide TRMM PR latent heating, which suggests that the impact of upper level cloud is more important to large-scale tropical circulation variations because of convective feedbacks rather than direct forcing by the cloud radiative heating profiles. However, the height of the radiative heating maxima and gradient of the heating profiles are important to determine the sign and patterns of the horizontal circulation anomaly driven by radiative heating at upper levels. © 2012. American Geophysical Union."
"6507253177;7003991093;","Dynamics of midlatitude tropopause height in an idealized model",2011,"10.1175/2010JAS3631.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79955011379&doi=10.1175%2f2010JAS3631.1&partnerID=40&md5=9261185e9a22d0643be0676549fb9431","This paper investigates the factors that determine the equilibrium state, and in particular the height and structure of the tropopause, in an idealized primitive equation model forced by Newtonian cooling in which the eddies can determine their own depth. Previous work has suggested that the midlatitude tropopause height may be understood as the intersection between a radiative and a dynamical constraint. The dynamical constraint relates to the lateral transfer of energy, which in midlatitudes is largely effected by baroclinic eddies, and its representation in terms of mean-flow properties. Various theories have been proposed and investigated for the representation of the eddy transport in terms of the mean flow, including a number of diffusive closures and the notion that the flow evolves to a state marginally supercritical to baroclinic instability. The radiative constraint expresses conservation of energy and so must be satisfied, although it need not necessarily be useful in providing a tight constraint on tropopause height. This paper explores whether and how the marginal criticality and radiative constraints work together to produce an equilibrated flow and a tropopause that is internal to the fluid. The paper investigates whether these two constraints are consistent with simulated variations in the tropopause height and in the mean state when the external parameters of an idealized primitive equation model are changed. It is found that when the vertical redistribution of heat is important, the radiative constraint tightly constrains the tropopause height and prevents an adjustment to marginal criticality. In contrast, when the stratification adjustment is small, the radiative constraint is only loosely satisfied and there is a tendency for the flow to adjust to marginal criticality. In those cases an alternative dynamical constraint would be needed in order to close the problem and determine the eddy transport and tropopause height in terms of forcing and mean flow. © 2011 American Meteorological Society."
"7407067059;56175416300;","Surface frontogenesis and thermohaline intrusion in a shelfbreak front",2011,"10.1016/j.ocemod.2011.02.012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79954427752&doi=10.1016%2fj.ocemod.2011.02.012&partnerID=40&md5=bb7c451d781725f5cf2ac9a7a8021352","Surface frontogenesis and thermohaline intrusion are examined in a submesoscale eddy-resolving primitive-equation model simulation of an idealized summer shelfbreak front of the Middle Atlantic Bight (USA). The initial front evolves into fully developed geostrophic turbulence characterized by large Rossby number, strong vortical asymmetry, and k-3 eddy kinetic energy and density spectra (k is the horizontal wavenumber). The baroclinic eddies are trapped in the upper 20m, and their growth is limited by conversion from the eddy to mean kinetic energy. The surface frontogenesis drives vigorous thermohaline intrusions of density-compensated temperature and salinity anomalies. Warmer saltier slope waters are subducted in the wave troughs, while colder fresher shelf waters are upwelled in the wave crests. The model results compare well with the observed distribution of subsurface salinity maxima. The total eddy induced onshore salt flux is comparable to the estimated salt budget in the Mid-Atlantic shelf. © 2011 Elsevier Ltd."
"14019572700;7003991093;","An Intermediate Complexity Climate Model (ICCMp1) based on the GFDL flexible modelling system",2009,"10.5194/gmd-2-73-2009","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350646370&doi=10.5194%2fgmd-2-73-2009&partnerID=40&md5=b6fff9fae57dd4a7a4b91ea16cfc6faa","An intermediate complexity coupled ocean-atmosphere-land-ice model, based on the Geophysical Fluid Dynamics Laboratory (GFDL) Flexible Modelling System (FMS), has been developed to study mechanisms of ocean-atmosphere interactions and natural climate variability at interannual to interdecadal and longer time scales. The model uses the three-dimensional primitive equations for both ocean and atmosphere but is simplified from a ""state of the art"" coupled model by using simplified atmospheric physics and parameterisation schemes. These simplifications provide considerable savings in computational expense and, perhaps more importantly, allow mechanisms to be investigated more cleanly and thoroughly than with a more elaborate model. For example, the model allows integrations of several millennia as well as broad parameter studies. For the ocean, the model uses the free surface primitive equations Modular Ocean Model (MOM) and the GFDL/FMS sea-ice model (SIS) is coupled to the oceanic grid. The atmospheric component consists of the FMS B-grid moist primitive equations atmospheric dynamical core with highly simplified physical parameterisations. A simple bucket model is implemented for our idealised land following the GFDL/FMS Land model. The model is supported within the standard MOM releases as one of its many test cases and the source code is thus freely available. Here we describe the model components and present a climatology of coupled simulations achieved with two different geometrical configurations. Throughout the paper, we give a flavour of the potential for this model to be a powerful tool for the climate modelling community by mentioning a wide range of studies that are currently being explored. © 2009 Author(s)."
"56384704800;57202299549;56962915800;7601556245;","Consistency problem with tracer advection in the Atmospheric Model GAMIL",2008,"10.1007/s00376-008-0306-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-44649175254&doi=10.1007%2fs00376-008-0306-z&partnerID=40&md5=c533681195db89ff5c54431eaf58ca5f","The radon transport test, which is a widely used test case for atmospheric transport models, is carried out to evaluate the tracer advection schemes in the Grid-Point Atmospheric Model of IAP-LASG (GAMIL). Two of the three available schemes in the model are found to be associated with significant biases in the polar regions and in the upper part of the atmosphere, which implies potentially large errors in the simulation of ozone-like tracers. Theoretical analyses show that inconsistency exists between the advection schemes and the discrete continuity equation in the dynamical core of GAMIL and consequently leads to spurious sources and sinks in the tracer transport equation. The impact of this type of inconsistency is demonstrated by idealized tests and identified as the cause of the aforementioned biases. Other potential effects of this inconsistency are also discussed. Results of this study provide some hints for choosing suitable advection schemes in the GAMIL model. At least for the polar-region-concentrated atmospheric components and the closely correlated chemical species, the Flux-Form Semi-Lagrangian advection scheme produces more reasonable simulations of the large-scale transport processes without significantly increasing the computational expense. © Science Press 2008."
"8631000600;15749945800;6701550654;6602799315;55885258700;","Stochastic study of the temperature response of the upper ocean to uncertainties in the atmospheric forcing in an Atlantic OGCM",2008,"10.1016/j.ocemod.2007.07.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-36248994834&doi=10.1016%2fj.ocemod.2007.07.006&partnerID=40&md5=82daa1ebcdab9d07eaed3f26de86b771","The impact of errors in atmospheric forcing on the behaviour of ocean models is a fundamental issue for ocean modellers and data assimilation and one that has yet to be fully addressed. In this study, we use a stochastic modelling approach with 50 7-months (September-March) primitive equation eddy permitting (1/4°) integrations. We investigate the response of the oceanic circulation to atmospheric uncertainties, focusing principally on their impact on the upper oceanic temperature field. The ensemble is generated by perturbing the wind, atmospheric temperature and incoming solar radiation of the ERA40 reanalysis. Each perturbation consists of a random combination of the 20 dominant EOFs of the difference between the ERA40 and NCEP/CORE reanalysis datasets. The ensemble standard deviation of various interfacial and oceanic quantities is then examined in the upper 200 m of three distinct regions of the North Atlantic: in the Gulf Stream, in the Northern Tropical band and in the North East Atlantic. These show that even a very small perturbation of the atmospheric variables can lead to significant changes in the ocean properties and that regions of oceanic mesoscale activity are the most sensitive. The ocean response is driven by vertical diffusivity and eddy activity. The role of subsurface currents is also crucial in carrying the eddy signal away from the regions of mesoscale activity. Finally, the decorrelation time scale of the mesoscale activity is critical in determining the amplitude of the oceanic response. © 2007 Elsevier Ltd. All rights reserved."
"7103321545;","Similarity and difference between the South Atlantic convergence zone and the Baiu frontal zone simulated by an AGCM",2007,"10.2151/jmsj.85.277","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548019742&doi=10.2151%2fjmsj.85.277&partnerID=40&md5=17c9f7ebbc14217dd41d40bb87a407bf","Features of the South Atlantic convergence zone (SACZ) and the Baiu frontal zone (BFZ) simulated by an AGCM (T106L56: a primitive equation spectral model which has 56 σ-levels and triangular spectral truncation at wave-number 106) are studied. The 24-year integration, from 1979 to 2002, by the model constrained by observed sea-surface temperature and sea-ice distribution, is used for this study. The detailed analysis is made for the typical case of SACZ and BFZ selected from data in 1985-1996. The South American monsoon circulation and the associated precipitation are reasonably reproduced. The precipitation zone of the SACZ, which extends southeastward from the southern part of Brazil to the South Atlantic, is sustained along the southwestern rim of the South Atlantic subtropical anticyclone during the southern summer. The Asian monsoon circulation and the associated precipitation are also reasonably reproduced. The precipitation zone of the BFZ, which extends northeastward from the southern part of China to Japan is formed along the northwestern rim of the North Pacific subtropical anticyclone in June. Many common features are found in the simulated SACZ and BFZ, in regard to the frontal structure and the associated synoptic- and meso-α-scale disturbances, and the relation to the respective subtropical anticyclone. However, an important difference is seen between their geographical environments. The cold south Atlantic in the poleward side of the SACZ provides the significant baroclinicity for SACZ, while the existence of warm land mass to the poleward side of the BFZ brings on weak baroclinicity of the BFZ. Another significant difference is seen in the large-scale environmental condition. The SACZ is influenced, in essence, by the trade winds and the subtropical anticyclone over the South Atlantic. The BFZ is strongly influenced by the moisture transport due to the Indian monsoon westerly and variation of the North Pacific subtropical anticyclone related to the convective activity over the western North Pacific. © 2007, Meteorological Society of Japan."
"7102001327;7005720566;","Gravity wave diagnosis using empirical normal modes",1999,"10.1175/1520-0469(1999)056<2706:GWDUEN>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032787343&doi=10.1175%2f1520-0469%281999%29056%3c2706%3aGWDUEN%3e2.0.CO%3b2&partnerID=40&md5=1a0569ed65981bb1f10e7053a31b3fbb","The theory of empirical normal modes (ENMs) is adapted to diagnose gravity waves generated by a relatively high-resolution numerical model solving the primitive equations. The ENM approach is based on the principal component analysis (which consists of finding the most efficient basis explaining the variance of a time series), except that it takes advantage of wave-activity conservation laws. In the present work, the small-amplitude version of the pseudoenergy is used to extract from data quasi-monochromatic three-dimensional empirical modes that describe atmospheric wave activity. The spatial distributions of these quasi-monochromatic modes are identical to the normal modes of the linearized primitive equations when the underlying dynamics can be described with a stochastic linear and forced model, thus establishing a bridge between statistics and dynamics. This diagnostic method is used to study inertia-gravity wave generation, propagation, transience, and breaking over the Rockies, the North Pacific, and Central America in the troposphere-stratosphere-mesosphere Geophysical Fluid Dynamics Laboratory SKYHI general circulation model at a resolution of 1° of latitude by 1.2° of longitude. Besides the action of mountains in exciting orographic waves, inertia-gravity wave activity has been found to be generated at the jet stream level as a possible consequence of a sustained nonlinear and ageostrophic flow. In the tropical region of the model (Central America), the inertia-gravity wave source mechanism produced mainly waves with a westward vertical tilt. A significant proportion of these inertia-gravity waves was able to reach the model mesosphere without much dissipation and absorption.The theory of empirical normal modes (ENMs) is adapted to diagnose gravity waves generated by a relatively high-resolution numerical model solving the primitive equations. The ENM approach is based on the principal component analysis (which consists of finding the most efficient basis explaining the variance of a time series), except that it takes advantage of wave-activity conservation laws. In the present work, the small-amplitude version of the pseudoenergy is used to extract from data quasi-monochromatic three-dimensional empirical modes that describe atmospheric wave activity. The spatial distributions of these quasi-monochromatic modes are identical to the normal modes of the linearized primitive equations when the underlying dynamics can be described with a stochastic linear and forced model, thus establishing a bridge between statistics and dynamics. This diagnostic method is used to study inertia-gravity wave generation, propagation, transience, and breaking over the Rockies, the North Pacific, and Central America in the troposphere-stratosphere-mesosphere Geo-physical Fluid Dynamics Laboratory SKYHI general circulation model at a resolution of 1°of latitude by 1.2°of longitude. Besides the action of mountains in exciting orographic waves, inertia-gravity wave activity has been found to be generated at the jet stream level as a possible consequence of a sustained nonlinear and ageostrophic flow. In the tropical region of the model (Central America), the inertia-gravity wave source mechanism produced mainly waves with a westward vertical tilt. A significant proportion of these inertia-gravity waves was able to reach the model mesosphere without much dissipation and absorption."
"6602858513;7202583200;","Orographically induced stationary waves: dependence on latitude",1995,"10.1175/1520-0469(1995)052<2548:OISWDO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029413377&doi=10.1175%2f1520-0469%281995%29052%3c2548%3aOISWDO%3e2.0.CO%3b2&partnerID=40&md5=59f66200d5d7a0061642786c5729beb9","A general circulation model (GCM) with idealized boundary conditions is used to study the effects of a mountain's latitudinal position on the stationary wave response. In each of a series of experiments the only asymmetry in the boundary conditions is a Gaussian-shaped mountain with an e-folding width of 15° latitude placed at 0°, 15°, 30°, 45°, and 60° latitude in separate integrations. The stationary wave response in the GCM is analyzed using a linearized primitive equation model, a 3D wave-flux vector, and a barotropic ray-tracing technique. Stationary waves in the GCM are generated by modifications to the diabatic heating field, termed thermal forcing, and by obstructing the surface winds, termed mechanical forcing. In this idealized setting, the propagation patterns of the stationary waves can, for the most part, be understood through quasigeostrophic theory. The dispersion of stationary wave energy throughout the atmosphere is largely dependent upon the upper-level flow. -from Authors"
"6506197139;7801521822;57217925273;6603894240;7004544454;","Dispersion properties of the flow in the southern stratosphere during winter and spring",1995,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029141520&partnerID=40&md5=30368fb8be9c9e8c97cb34e94418e2ab","The STRATEOLE project, organized by France's Centre National de la Recherche Scientifique (CNRS), will release a large number of isopycnal balloons to drift in the lower stratosphere of the southern hemisphere. In preparation for STRATEOLE this paper studies the structure and dispersion properties of the flow in the lower stratosphere at high southern latitudes during winter and spring. The approach for investigation is based on computing trajectories of fluid parcels and isopycnal balloons using the velocity field obtained on-line during simulations with a three-dimensional primitive-equation model of the stratosphere and mesosphere. A scheme for computation of isopycnal balloon trajectories is devised, and a method for estimating the location of the polar night vortex edge is developed. The relative dispersion properties of the flow in the lower stratosphere are analyzed in the light of theories on two-dimensional turbulence. (from Authors)"
"6701594572;57197406352;7003536992;","BLFMESO - A 3-dimensional mesoscale meteorological model for microcomputers",1994,"10.1007/BF00709221","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028668501&doi=10.1007%2fBF00709221&partnerID=40&md5=d39b7b276f32a05d9a5e959657a1d4d6","A three-dimensional boundary-layer meteorological model for meso-β-scale domains has been developed for use on micro-computers (personal computers and low-end workstations). This hydrostatic model, named BLFMESO, is based on primitive equations with terrain-following coordinates and is capable of reproducing complex-terrain-induced mesoscale circulations. In this paper, a description of the model formulations and parameterizations is provided and discussed. Also presented are some sample results of BLFMESO simulations of lake effects for a 180 km × 180 km domain surrounding the city of Toronto (Canada) on Lake Ontario. Since this mesoscale model requires only about 20 minutes of computer time on a personal computer (Intel 80486-33 MHz CPU) for a 12 hour simulation, it can be a useful tool for real-time operational boundary-layer meteorology applications. © 1994 Kluwer Academic Publishers."
"7005561589;7402826517;","Comments on ‘Spatial structure of ultra‐low frequency variability of the flow in a simple atmospheric circulation model’ by I. N. James and P. M. James (October 1992, 118, 1211–1233.)",1994,"10.1002/qj.49712051714","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983941219&doi=10.1002%2fqj.49712051714&partnerID=40&md5=9d5465d9c54406555b360cf5edb78250","James and James (1992) examine internally generated interannual variability in a multi‐level primitive‐equation model. The authors claim that the variability in the global mean relative angular velocity is associated with fluctuations in the mid‐latitude zonally‐averaged zonal winds. We question this relationship, and present results from an aqua‐planet GCM which indicate that, instead, the global mean relative angular velocity is primarily related to changes in the tropical zonally‐averaged zonal winds. Furthermore, we also question whether the ‘ultra‐low‐frequency variability’ examined by James and James is not simply just ‘climate noise’. Copyright © 1994 Royal Meteorological Society"
"55894188500;7006441675;7101889823;7003440089;6507511542;6603076673;","Preliminary simulations of the flow field over the Attic Peninsula",1993,"10.1016/0266-9838(93)90007-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027789369&doi=10.1016%2f0266-9838%2893%2990007-5&partnerID=40&md5=4673d632771c1cb602e8aae588512279","In the frame of the APSIS experiment, three mesoscale meteorological models have been used over the Attic Peninsula. TVM (IAG UCl) developed from the URBMET code (USA, 1985) is hydrostatic, boussinesq and written in vorticity. MAR (IAG-UCL) is a fully compressible hydrostatic primitive equations model, and RAMS (CSU, USA) is non hydrostatic and fully compressible. These three models have been tested on the Athens region where strong interactions exist between different sea-breeze cells and the complex topography. Suring unstable daytime conditions, all models are shown to produce similar wind fields and good agreement with measurements, while the stable night-time leads to leads to larger differences. © 1993."
"6701853567;57203406068;7101825844;","A global low-order spectral general circulation model. Part I: formulation and seasonal climatology.",1982,"10.1175/1520-0469(1982)039<0929:AGLOSG>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020388298&doi=10.1175%2f1520-0469%281982%29039%3c0929%3aAGLOSG%3e2.0.CO%3b2&partnerID=40&md5=5e4ad12258734acd3b43266b072d7860","A global, spectral, primitive equation model is developed to study the seasonal climatology of the large-scale features of the atmosphere. The model resolution is five equally-spaced sigma levels in the vertical and triangular truncation at wavenumber 10 in the horizontal. The model reasonably reproduces the general features of the observed atmospheric circulation, seasonal cycles, interannual variations and hemispheric differences.-from Authors"
"7102315560;","Growth and vacillation cycles of disturbances in Southern Hemisphere flows.",1981,"10.1175/1520-0469(1981)038<1360:GAVCOD>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019704844&doi=10.1175%2f1520-0469%281981%29038%3c1360%3aGAVCOD%3e2.0.CO%3b2&partnerID=40&md5=dd769fdfc88819d773ef0ea45afcc732","The nonlinear interaction of initial single zonal wavenumber small-amplitude waves with Southern Hemisphere zonal flows characteristic of January and May is studied in a multilevel primitive equation spectral model with spherical geometry and viscous dissipation. -from AuthorNational Center for Atmospheric Research, Boulder, CO 80307, USA."
"7101772062;6603187267;","A further study of the annual cycle of the zonal mean circulation in the middle atmosphere.",1981,"10.1175/1520-0469(1981)038<1504:AFSOTA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019654836&doi=10.1175%2f1520-0469%281981%29038%3c1504%3aAFSOTA%3e2.0.CO%3b2&partnerID=40&md5=570001a1d2390c6f8f2f728ca7036423","The influence on the stratospheric mean circulation of planetary wavenumber 2 disturbances excited by steady forcing at the 100mb level is investigated using a global semi-spectral primitive equation model. There exists a critical forcing amplitude below which the waves have little effect on the mean flow, while above which the waves produce subseasonal time scale vacillations in the winter hemisphere, including both major and minor warmings. -from Authors"
"57200335420;54879515900;56126198500;56282183100;16025236700;55924208000;","Choosing the Optimal Numerical Precision for Data Assimilation in the Presence of Model Error",2018,"10.1029/2018MS001341","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052946155&doi=10.1029%2f2018MS001341&partnerID=40&md5=27cedb6513286dd3aeadbe70934b7098","The use of reduced numerical precision within an atmospheric data assimilation system is investigated. An atmospheric model with a spectral dynamical core is used to generate synthetic observations, which are then assimilated back into the same model using an ensemble Kalman filter. The effect on the analysis error of reducing precision from 64 bits to only 22 bits is measured and found to depend strongly on the degree of model uncertainty within the system. When the model used to generate the observations is identical to the model used to assimilate observations, the reduced-precision results suffer substantially. However, when model error is introduced by changing the diffusion scheme in the assimilation model or by using a higher-resolution model to generate observations, the difference in analysis quality between the two levels of precision is almost eliminated. Lower-precision arithmetic has a lower computational cost, so lowering precision could free up computational resources in operational data assimilation and allow an increase in ensemble size or grid resolution. ©2018. The Authors."
"7006770362;18536452000;6507563616;6602444854;8874791900;7003712840;7102423693;7801340865;6602142887;55998823100;57197478967;44761200000;","Enviro-HIRLAM online integrated meteorology-chemistry modelling system: Strategy, methodology, developments and applications (v7.2)",2017,"10.5194/gmd-10-2971-2017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027360640&doi=10.5194%2fgmd-10-2971-2017&partnerID=40&md5=01f2e66889cff1cfb56b3f6a7aa873ce","The Environment - High Resolution Limited Area Model (Enviro-HIRLAM) is developed as a fully online integrated numerical weather prediction (NWP) and atmospheric chemical transport (ACT) model for research and forecasting of joint meteorological, chemical and biological weather. The integrated modelling system is developed by the Danish Meteorological Institute (DMI) in collaboration with several European universities. It is the baseline system in the HIRLAM Chemical Branch and used in several countries and different applications. The development was initiated at DMI more than 15 years ago. The model is based on the HIRLAM NWP model with online integrated pollutant transport and dispersion, chemistry, aerosol dynamics, deposition and atmospheric composition feedbacks. To make the model suitable for chemical weather forecasting in urban areas, the meteorological part was improved by implementation of urban parameterisations. The dynamical core was improved by implementing a locally mass-conserving semi-Lagrangian numerical advection scheme, which improves forecast accuracy and model performance. The current version (7.2), in comparison with previous versions, has a more advanced and cost-efficient chemistry, aerosol multi-compound approach, aerosol feedbacks (direct and semi-direct) on radiation and (first and second indirect effects) on cloud microphysics. Since 2004, the Enviro-HIRLAM has been used for different studies, including operational pollen forecasting for Denmark since 2009 and operational forecasting atmospheric composition with downscaling for China since 2017. Following the main research and development strategy, further model developments will be extended towards the new NWP platform - HARMONIE. Different aspects of online coupling methodology, research strategy and possible applications of the modelling system, and ""fit-for-purpose"" model configurations for the meteorological and air quality communities are discussed. © Author(s) 2017."
"36873159700;55899460500;","The interaction between gravity waves and solar tides in a linear tidal model with a 4-D ray-tracing gravity-wave parameterization",2016,"10.1002/2016JA022478","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988653852&doi=10.1002%2f2016JA022478&partnerID=40&md5=2f917c3de64713189a41c6f47574424b","Gravity waves (GWs) play an important role in atmospheric dynamics. Due to their short wavelengths, they must be parameterized in current weather and forecast models, which cannot resolve them explicitly. We are here the first to report the possibility and the implication of having an online GW parameterization in a linear but global model that incorporates their horizontal propagation, the effects of transients and of horizontal background gradients on GW dynamics. The GW parameterization is based on a ray-tracer model with a spectral formulation that is safe against numerical instabilities due to caustics. The global model integrates the linearized primitive equations to obtain solar tides (STs), with a seasonally dependent reference climatology, forced by a climatological daily cycle of the tropospheric and stratospheric heating, and the (instantaneous) GW momentum and buoyancy flux convergences resulting from the ray tracer. Under a more conventional “single-column” approximation, where GWs only propagate vertically and do not respond to horizontal gradients of the resolved flow, GW impacts are shown to be significantly changed in comparison with “full” experiments, leading to significant differences in ST amplitudes and phases, pointing at a sensitive issue of GW parameterizations in general. In the full experiment, significant semidiurnal STs arise even if the tidal model is only forced by diurnal heating rates. This indicates that an important part of the tidal signal is forced directly by GWs via their momentum and buoyancy deposition. In general, the effect of horizontal GW propagation and the GW response to horizontal large-scale flow gradients is rather observed in nonmigrating than in migrating tidal components. ©2016. American Geophysical Union. All Rights Reserved."
"7402435469;57212416832;36876405100;6507501796;7406243250;7103377710;","Energy considerations in the Community Atmosphere Model (CAM)",2015,"10.1002/2015MS000448","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945461404&doi=10.1002%2f2015MS000448&partnerID=40&md5=f8c136b9727d09004d88ac20b73c8503","An error in the energy formulation in the Community Atmosphere Model (CAM) is identified and corrected. Ten year AMIP simulations are compared using the correct and incorrect energy formulations. Statistics of selected primary variables all indicate physically insignificant differences between the simulations, comparable to differences with simulations initialized with rounding sized perturbations. The two simulations are so similar mainly because of an inconsistency in the application of the incorrect energy formulation in the original CAM. CAM used the erroneous energy form to determine the states passed between the parameterizations, but used a form related to the correct formulation for the state passed from the parameterizations to the dynamical core. If the incorrect form is also used to determine the state passed to the dynamical core the simulations are significantly different. In addition, CAM uses the incorrect form for the global energy fixer, but that seems to be less important. The difference of the magnitude of the fixers using the correct and incorrect energy definitions is very small. © 2015. The Authors."
"7004676489;6701335949;55189671700;","Idealized global nonhydrostatic atmospheric test cases on a reduced-radius sphere",2015,"10.1002/2015MS000435","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944884296&doi=10.1002%2f2015MS000435&partnerID=40&md5=19ca6a75b0c12837eb4cbf638c72e073","Idealized simulations on a reduced-radius sphere can provide a useful vehicle for evaluating the behavior of nonhydrostatic processes in nonhydrostatic global atmospheric dynamical cores provided the simulated cases exhibit good agreement with corresponding flows in a Cartesian geometry, and for which there are known solutions. Idealized test cases on a reduced-radius sphere are presented here that focus on both dry and moist dynamics. The dry dynamics cases are variations of mountain-wave simulations designed for the Dynamical Core Model Intercomparison Project (DCMIP), and permit quantitative comparisons with linear analytic mountain-wave solutions in a Cartesian geometry. To evaluate moist dynamics, an idealized supercell thunderstorm is simulated that has strong correspondence to results obtained on a flat plane, and which can be numerically converged by specifying a constant physical diffusion. A simple Kessler-type routine for cloud microphysics is provided that can be readily implemented in atmospheric simulation models. Results for these test cases are evaluated for simulations with the Model for Prediction across scales (MPAS). They confirm close agreement with corresponding simulations in a Cartestian geometry; the mountain-wave results agree well with analytic mountain-wave solutions, and the simulated supercells are consistent with other idealized supercell simulation studies and exhibit convergent behavior. © 2015. The Authors."
"6506756436;7004115548;","An alternative cell-averaged departure point reconstruction for pointwise semi-Lagrangian transport schemes",2015,"10.1002/qj.2509","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941192119&doi=10.1002%2fqj.2509&partnerID=40&md5=d148164e56d0e7ef187309813006a2bc","Convection-permitting limited-area models based on the same spectral semi-implicit semi-Lagrangian (SL) techniques which are used in the ECMWF global model, are run operationally in several countries of the ALADIN/HIRLAM consortium. Forecasters have reported a general tendency for these models to produce overestimated precipitation and unrealistic divergent winds at the edges of the cold outflows generated by the precipitation evaporation in the vicinity of convective clouds. These grid-point storms have been associated with a spurious behaviour of the pointwise interpolation used in the SL scheme, where grid-scale buoyant updraughts create strong small-scale convergence near the surface. A modification of the interpolation weights in the SL transport scheme introduces the concept of cell-averaging into the traditional pointwise SL scheme which improves the conservation property of the scheme and eliminates the spurious mode. The COMAD (COntinuous Mapping about Departure points) correction applied to the standard interpolation weights takes into account the deformation of the air parcels along each direction of interpolation in order to improve the continuity and the conservative property of the re-mapping between the model grid points and the origin points of the backward trajectories. The method has been validated with the small planet configuration of the Integrated Forecast System at ECMWF and with the limited-area version of the same dynamics used for the AROME (Météo-France) and HARMONIE (HIRLAM) models. The pathological behaviour of grid-scale buoyant flows permitted by these dynamical cores is corrected by the COMAD interpolations. The precipitation forecasts in the convection-permitting models AROME/HARMONIE which show an overestimation of intense convective precipitation are systematically improved by the new weights. © 2015 Royal Meteorological Society."
"56460283800;6701500839;8696068200;","A conservative adaptive wavelet method for the shallow-water equations on the sphere",2015,"10.1002/qj.2473","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939466396&doi=10.1002%2fqj.2473&partnerID=40&md5=d23bb1e9c9fb75453ae91b12b711a2e9","We introduce an innovative wavelet-based approach to adjust local grid resolution dynamically to maintain a uniform specified error tolerance. Extending the work of Dubos and Kevlahan, a wavelet multiscale approximation is used to make the Thuburn-Ringler-Skamarock-Klemp (TRiSK) model dynamically adaptive for the rotating shallow-water equations on the sphere. This article focuses on the challenges encountered when extending the adaptive wavelet method to the sphere and ensuring an efficient parallel implementation using message passing interface (MPI). The wavelet method is implemented in Fortran 95 with an emphasis on computational efficiency and scales well up to O(102) processors for load-unbalanced scenarios and up to at least O(103) processors for load-balanced scenarios. The method is verified using standard smooth test cases and a nonlinear test case proposed by Galewsky et al. The dynamical grid adaption provides compression ratios of up to 50 times in a challenging homogenous turbulence test case. The adaptive code is about three times slower per active grid point than the equivalent non-adaptive TRiSK code and about four times slower per active grid point than an equivalent spectral code. This computationally efficient adaptive dynamical core could serve as the foundation on which to build a complete climate or weather model. © 2015 Royal Meteorological Society."
"16302259500;8750834400;7102322882;6603634026;57216119439;7004480520;","Analytical solution for waves in planets with atmospheric superrotation. I. Acoustic and inertia-gravity waves",2014,"10.1088/0067-0049/213/1/17","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904307363&doi=10.1088%2f0067-0049%2f213%2f1%2f17&partnerID=40&md5=e5242e102eb5bf1260101182931e04f6","This paper is the first of a two-part study devoted to developing tools for a systematic classification of the wide variety of atmospheric waves expected on slowly rotating planets with atmospheric superrotation. Starting with the primitive equations for a cyclostrophic regime, we have deduced the analytical solution for the possible waves, simultaneously including the effect of the metric terms for the centrifugal force and the meridional shear of the background wind. In those cases when the conditions for the method of the multiple scales in height are met, these wave solutions are also valid when vertical shear of the background wind is present. A total of six types of waves have been found and their properties were characterized in terms of the corresponding dispersion relations and wave structures. In this first part, only waves that are direct solutions of the generic dispersion relation are studied - acoustic and inertia-gravity waves. Concerning inertia-gravity waves, we found that in the cases of short horizontal wavelengths, null background wind, or propagation in the equatorial region, only pure gravity waves are possible, while for the limit of large horizontal wavelengths and/or null static stability, the waves are inertial. The correspondence between classical atmospheric approximations and wave filtering has been examined too, and we carried out a classification of the mesoscale waves found in the clouds of Venus at different vertical levels of its atmosphere. Finally, the classification of waves in exoplanets is discussed and we provide a list of possible candidates with cyclostrophic regimes. © 2014. The American Astronomical Society. All rights reserved."
"8696068200;24478214200;","A semihydrostatic theory of gravity-dominated compressible flow",2014,"10.1175/JAS-D-14-0080.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84916201191&doi=10.1175%2fJAS-D-14-0080.1&partnerID=40&md5=150dde32acdfe431c2df350313ad9c5e","From Hamilton's least-action principle, compressible equations of motion with density diagnosed from potential temperature through hydrostatic balance are derived. Slaving density to potential temperature suppresses the degrees of freedom supporting the propagation of acoustic waves and results in a soundproof system. The linear normal modes and dispersion relationship for an isothermal state of rest on f and β planesare accurate from hydrostatic to nonhydrostatic scales, except for deep internal gravity waves. Specifically, the Lamb wave and long Rossby waves are not distorted, unlike with anelastic or pseudoincompressible systems. Compared to similar equations derived by A. Arakawa and C. S. Konor, the semihydrostatic system derived here possesses an additional term in the horizontal momentum budget. This term is an apparent force resulting from the vertical coordinate not being the actual height of an air parcel but its hydrostatic height (the hypothetical height it would have after the atmospheric column it belongs to has reached hydrostatic balance through adiabatic vertical displacements of air parcels). The Lagrange multiplier λ introduced in Hamilton's principle to slave density to potential temperature is identified as the nonhydrostatic vertical displacement (i.e., the difference between the actual and hydrostatic heights of an air parcel). The expression of nonhydrostatic pressure and apparent force from λ allow the derivation of a well-defined linear symmetric positive definite problem for λ. As with hydrostatic equations, vertical velocity is diagnosed through Richardson's equation. The semihydrostatic system has therefore precisely the same degrees of freedom as the hydrostatic primitive equations, while retaining much of the accuracy of the fully compressible Euler equations. © 2014 American Meteorological Society."
"56555458900;14059214300;22137065500;55487667200;57211379123;7408519295;","Evaluation of cloud vertical structure simulated by recent BCC_AGCM versions through comparison with CALIPSO-GOCCP data",2014,"10.1007/s00376-013-3099-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897476376&doi=10.1007%2fs00376-013-3099-7&partnerID=40&md5=7f269bca236c1f41ce80b49dab16cae4","The abilities of BCC_AGCM2.1 and BCC_AGCM2.2 to simulate the annual-mean cloud vertical structure (CVS) were evaluated through comparison with GCM-Oriented CALIPSO Cloud Product (CALIPSO-GOCCP) data. BCC_AGCM2.2 has a dynamical core and physical processes that are consistent with BCC_AGCM2.1, but has a higher horizontal resolution. Results showed that both BCC_AGCM versions underestimated the global-mean total cloud cover (TCC), middle cloud cover (MCC) and low cloud cover (LCC), and that BCC_AGCM2.2 underestimated the global-mean high cloud cover (HCC). The global-mean cloud cover shows a systematic decrease from BCC_AGCM2.1 to BCC_AGCM2.2, especially for HCC. Geographically, HCC is significantly overestimated in the tropics, particularly by BCC_AGCM2.1, while LCC is generally overestimated over extra-tropical lands, but significantly underestimated over most of the oceans, especially for subtropical marine stratocumulus clouds. The leading EOF modes of CVS were extracted. The BCC_AGCMs perform well in reproducing EOF1, but with a larger variance explained. The two models also capture the basic features of EOF3, except an obvious deficiency in eigenvector peaks. EOF2 has the largest simulation biases in both position and strength of eigenvector peaks. Furthermore, we investigated the effects of CVS on relative shortwave and longwave cloud radiative forcing (RSCRF and RLCRF). Both BCC_AGCM versions successfully reproduce the sign of regression coefficients, except for RLCRF in PC1. However, the RSCRF relative contributions from PC1 and PC2 are overestimated, while the relative contribution from PC3 is underestimated in both BCC_AGCM versions. The RLCRF relative contribution is underestimated for PC2 and overestimated for PC3. © 2014 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"6504265453;7003436398;15124325100;","An investigation of a super-Earth exoplanet with a greenhouse-gas atmosphere using a general circulation model",2013,"10.1016/j.icarus.2012.12.019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884981675&doi=10.1016%2fj.icarus.2012.12.019&partnerID=40&md5=a00f36c54632cb036e6726e6b19a1057","We use the Massachusetts Institute of Technology general circulation model (GCM) dynamical core, in conjunction with a Newtonian relaxation scheme that relaxes to a gray, analytical solution of the radiative transfer equation, to simulate a tidally locked, synchronously orbiting super-Earth exoplanet. This hypothetical exoplanet is simulated under the following main assumptions: (1) the size, mass, and orbital characteristics of GJ 1214b (Charbonneau, D. [2009]. Nature 462, 891-894), (2) a greenhouse-gas dominated atmosphere, (3), the gas properties of water vapor, and (4) a surface. We have performed a parameter sweep over global mean surface pressure (0.1, 1, 10, and 100. bar) and global mean surface albedo (0.1, 0.4, and 0.7). Given assumption (1) above, the period of rotation of this exoplanet is 1.58 Earth-days, which we classify as the rapidly rotating regime. Our parameter sweep differs from Heng and Vogt (Heng, K., Vogt, S.S. [2011]. Mon. Not. R. Astron. Soc. 415, 2145-2157), who performed their study in the slowly rotating regime and using Held and Suarez (Held, I.M., Suarez, M.J. [1994]. Bull. Am. Meteorol. Soc. 75 (10), 1825-1830) thermal forcing. This type of thermal forcing is a prescribed function, not related to any radiative transfer, used to benchmark Earth's atmosphere. An equatorial, westerly, superrotating jet is a robust feature in our GCM results. This equatorial jet is westerly at all longitudes. At high latitudes, the flow is easterly. The zonal winds do show a change with global mean surface pressure. As global mean surface pressure increases, the speed of the equatorial jet decreases between 9 and 15. h local time (substellar point is located at 12. h local time). The latitudinal extent of the equatorial jet increases on the nightside. For the two greatest initial surface pressure cases, an increasingly westerly component of flow develops at middle to high latitudes between 11 and 18. h local time. On the nightside, the easterly flow in the midlatitudes also increases in speed as global mean surface pressure increases. Furthermore, the zonal wind speed in the equatorial and midlatitude jets decreases with increasing surface albedo. Also, the latitudinal width of the equatorial jet decreases as surface albedo increases. © 2013 Elsevier Inc."
"6701521854;7006422084;6506209657;","The meteorological global model GLOBO at the ISAC-CNR of Italy assessment of 1.5 yr of experimental use for medium-range weather forecasts",2011,"10.1175/WAF-D-11-00027.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857296374&doi=10.1175%2fWAF-D-11-00027.1&partnerID=40&md5=41d19bff1ddf33814aca2292bf519fe4","Since August 2009, the GLOBOatmospheric general circulation model has been running experimentally at the Institute of Atmospheric Sciences and Climate (ISAC) of the National Council of Research of Italy. GLOBO is derived from the Bologna Limited Area Model (BOLAM), a gridpoint limited-area meteorological model that was developed at the same institute and that has been extended to the entire earth atmosphere. The main dynamical features and physical parameterizations of GLOBO are presented. Starting from initial conditions obtained from the analysis of the NCEP Global Forecast System (GFS) model valid at 0000 UTC, 6-day forecasts with average horizontal resolution of 32 km were performed on a daily basis and in real time. The assessment of the forecast skill during the 1.5-yr period included the calculation of the monthly averaged root-mean-square errors (model prediction versus gridded analyses) of geopotential height at 500 hPa and mean sea level pressure for the northern and southern extratropics, performed accordingly to WMO Commission for Basic Systems (CBS) standards. The verification results are compared with models from other global data processing and forecasting system centers, as are available in the literature. The GLOBOskill for medium-range forecasts turns out to be comparable to that of the above models. The lack of analyses based on model forecasts and data assimilation is likely to penalize the scores for shorter-term forecasts. © 2011 American Meteorological Society."
"7103271625;7006739521;","Climate modeling",2008,"10.1146/annurev.environ.33.020707.160752","https://www.scopus.com/inward/record.uri?eid=2-s2.0-68049126436&doi=10.1146%2fannurev.environ.33.020707.160752&partnerID=40&md5=19ab5adf914c8e0bd96e260b945e582e","Climate models simulate the atmosphere, given atmospheric composition and energy from the sun, and include explicit modeling of, and exchanges with, the underlying oceans, sea ice, and land. The models are based on physical principles governing momentum, thermodynamics, cloud microphysics, radiative transfer, and turbulence. Climate models are evolving into Earth-system models, which also include chemical and biological processes and afford the prospect of links to studies of human dimensions of climate change. Although the fundamental principles on which climate models are based are robust, computational limits preclude their numerical solution on scales that include many processes important in the climate system. Despite this limitation, which is often dealt with by parameterization, many aspects of past and present climate have been successfully simulated using climate models, and climate models are used extensively to predict future climate change resulting from human activity. © 2008 by Annual Reviews."
"16246205000;57203012011;55738957800;7003652577;","Dynamical effects of convective momentum transports on global climate simulations",2008,"10.1175/2007JCLI1848.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40849106821&doi=10.1175%2f2007JCLI1848.1&partnerID=40&md5=844ecae32fe0bdda2c0244a34851c80c","Dynamical effects of convective momentum transports (CMT) on global climate simulations are investigated using the NCAR Community Climate Model version 3 (CCM3). To isolate the dynamical effects of the CMT, an experimental setup is proposed in which all physical parameterizations except for the deep convection scheme are replaced with idealized forcing. The CMT scheme is incorporated into the convection scheme to calculate the CMT forcing, which is used to force the momentum equations, while convective temperature and moisture tendencies are not passed into the model calculations in order to remove the physical feedback between convective heating and wind fields. Excluding the response of complex physical processes, the model with the experimental setup contains a complete dynamical core and the CMT forcing. Comparison between two sets of 5-yr simulations using this idealized general circulation model (GCM) shows that the Hadley circulation is enhanced when the CMT forcing is included, in agreement with previous studies that used full GCMs. It suggests that dynamical processes make significant contributions to the total response of circulation to CMT forcing in the full GCMs. The momentum budget shows that the Coriolis force, boundary layer friction, and nonlinear interactions of velocity fields affect the responses of zonal wind field, and the adjustment of circulation follows an approximate geostrophic balance. The adjustment mechanism of meridional circulation in response to ageostrophic CMT forcing is examined. It is found that the strengthening of the Hadley circulation is an indirect response of the meridional wind to the zonal CMT forcing through the Coriolis effect, which is required for maintaining near-geostrophic balance. © 2008 American Meteorological Society."
"7103321545;36842329100;55619302013;35776608800;","Polar-air outbreak and air-mass transformation over the east coast of Asia as simulated by an AGCM",2006,"10.2151/jmsj.84.47","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646419014&doi=10.2151%2fjmsj.84.47&partnerID=40&md5=7bbc93f36428a04699bca2c51289f30d","The present report studies features of the polar-air outbreak and the associated air-mass transformation over the east coast of Asia simulated in an AGCM (T106L52: a primitive equation spectral model, which has 52 σ-levels and triangular spectral truncation at wave-number 106) that used climatological SST in comparison with the features described in several observational studies. The large-scale circulations are properly reproduced for January Y07 (the 7th year after the spin up integration). A typical case of polar-air outbreak simulated in January is studied in detail. During the polar-air outbreak, cyclonic northwesterly polar-air streams over the Sea of Japan and the northwestern Pacific, and anticyclonic northeasterly polar-air streams over the East China Sea and the South China Sea are reasonably simulated. During the polar-air outbreak, the sensible and latent heat fluxes simulated over the Sea of Japan reach to ∼150 and ∼250 W m-2, while those over the East China Sea reach to ∼75 and ∼250 W m-2, respectively. These simulated fluxes agree with the fluxes evaluated in observational studies. The multi-layer structure of the transformed air-mass, including the unstable surface layer, the subcloud layer, and the cloud layer capped by the stable layer, simulated over the coastal areas of Asia is consistent with the observations for the cases of typical polar-air outbreak. However, the precipitation over the coastal areas of Japan simulated during the polar-air outbreak is significantly small as compared with the observation. This is due to the insufficient horizontal resolution of the T106L52 to simulate mesoscale circulation systems which induce snowfalls. In addition, the duration of the polar-air outbreak simulated in the AGCM is relatively short as compared with that in the real atmosphere, since the anticyclone over the continent tends to extend eastward in the model. © 2006, Meteorological Society of Japan."
"56175416300;6601976436;8705630200;7003580674;","Analysis of the circulation and shelf-slope exchanges in the continental margin of the northwestern Mediterranean",2006,"10.5194/os-2-173-2006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33750175776&doi=10.5194%2fos-2-173-2006&partnerID=40&md5=83965bd3905c33dec024b48be520ad3b","In this paper, we present the results from a high horizontal resolution numerical simulation of the northwestern Mediterranean using a z-level, non-hydrostatic, primitive equation ocean model (DieCAST). The high resolution allows an accurate representation of the submarine canyons that presides in the region. The model is one-way coupled to a large scale model of the Mediterranean Sea through open boundaries and uses the atmospheric forcing fields provided in terms of HIRLAM outputs by the Spanish National Institute of Meteorology. Results show that the model can successfully reproduce the complex general circulation characteristics of the area, including the modifications induced by canyons in their vicinity and other phenomena observed such as instabilities and coastal trapped waves. The sea surface temperature is similar to satellite observations except that simulated temperatures are slightly warmer near the coast than observations and colder near the open boundaries. An important topic of this work is the computation of the shelf-slope exchanges, which are able to renew shelf waters in a few months."
"7203024042;36025455800;6602649666;6603854428;8690530500;","Synoptic forcing of the Korea Strait transport",2005,"10.1016/j.dsr2.2004.08.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-23944455681&doi=10.1016%2fj.dsr2.2004.08.018&partnerID=40&md5=49fba34a75dc1786ad880b5e8cc0f4ec","Korea Strait transport variations in the synoptic frequency band (2-20 days) are examined using results of a numerical 3-D primitive equation model, satellite observed sea-level variations, a linear barotropic adjoint dynamic model, and observed transports. The 3-D numerical model does not assimilate observations, and the agreement with the observed transport implies that wind forcing is one of the main contributors to variations in the synoptic band. The satellite-observed and 3-D model sea-level indicate a sea-level response to wind stress along the east Korean coast that propagates toward the Korea Strait and changes the sea-level slope across the strait. The adjoint results indicate that wind stress is most influential in the area east of Korea along with secondarily important area along the East China Sea shelf break south of Japan. The mechanism connecting wind stress to transport variations is a Kelvin wave propagation that changes sea-level slope across the strait, leading to the altered geostrophic transport through the strait. A strong southerly wind initially produces a sea-level set down along the east Korea coast and a sea-level increase along the shelf break. The set down propagates to the Korea Strait as a Kelvin wave, sea level across the strait changes, and the transport through the strait increases. Similarly, northerly wind stress produces a set up along the Korea coast and subsequent decreased transport. Wind stresses across the Yellow and East China Seas are not a significant forcing mechanism since Kelvin waves would propagate away from the strait. Barotropic transport response to wind stress is rapid (on the order of 3 h), but the relatively slow development of the atmospheric forcing (on the order of 1-2 days) modulates the response."
"7005742394;7004048039;6603598937;8415051400;","Interaction of binary tropical cyclones in a coupled tropical cyclone-ocean model",2000,"10.1029/2000JD900268","https://www.scopus.com/inward/record.uri?eid=2-s2.0-18144385872&doi=10.1029%2f2000JD900268&partnerID=40&md5=f19b4b822015d6f674f8caf5fdc078e5","The motion and evolution of binary tropical cyclones was investigated using a coupled tropical cyclone-ocean movable nested grid model. The model consists of eight-layer atmospheric and seven-layer ocean primitive equation models. Several regimes of binary storm interaction have been identified, depending on the initial separation distance (d) and differences in storm strengths. At d less than a few hundred kilometers, interacting storms experienced complete merger (CM) or partial merger (PM). At larger d (between about 600 km and 1000 km), three regimes of storm interaction have been found: PM, straining out (SO), characterized by complete disintegration of the weaker storm, and mutual straining out (MSO), characterized by weakening and dissipation of both storms. SO occurred when the interacting storms had substantially different intensities and strengths. MSO was observed when the interacting storms were comparable in size and intensity. In the latter case the storms were unable to approach each other at distances smaller than a certain minimum distance (of about 450-500 km) without being mutually stretched out. Moreover, initial attraction of the storms in this regime was replaced by repulsion, as frequently observed in the western Pacific. At d exceeding about 1000 km, elastic interaction (EI) was found, when the storms interact without any significant changes in their intensity and structure. In additional experiments with a conditional instability of the second kind (CISK) type parameterization of convective heating the storm interaction was very different: The storms were nearly axisymmetric and very compact, and they continued approaching each other until they merged. Thus more realistic simulations of binary storm interaction can be achieved by using a physically more reasonable convective parameterization. Copyright 2000 by the American Geophysical Union."
"7007181954;56033135100;","Synoptic-scale perturbations in AGCM simulations of the present and Last Glacial Maximum climates",2000,"10.1007/PL00007923","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033873352&doi=10.1007%2fPL00007923&partnerID=40&md5=6c8ded7265d1ec1d66a044df5adc5124","The conditions of development of mid-latitude depressions (synoptic eddies) in the winter Northern Hemisphere mid-latitudes at the Last Glacial Maximum (LGM, 21 000 years ago) are very different from the present ones: this period is characterised by a general cooling of the extra-tropics, with massive ice sheets over the Northern Hemisphere continents and sea-ice extending very far south over the North Atlantic. The present work uses regression analysis to study the characteristics of the synoptic eddies in present-day and LGM climate simulations by the Atmospheric General Circulation Model (AGCM) of the UK Universities' Global Atmospheric Programme (UGAMP). In the LGM experiment, the structure of the Pacific eddies is similar to the present-day (PD) situation, but they are weaker. On the other hand, the Atlantic eddies show an increased zonal wavelength and a much shallower structure in the temperature and vertical wind perturbations. To understand the changes of these characteristics from present-day to LGM, we compare them to those computed for the most unstable modes of the corresponding mean flows, determined using a dry primitive equation model. A normal-mode stability analysis is carried both on zonally symmetric and asymmetric flows for each of the Northern Hemisphere storm-tracks. The changes in the most unstable normal modes found by both these analyses give a good account of changes in the structure of the perturbations as retrieved from the AGCM, suggesting that changes in the mean state (especially the temperature gradient) is the main driver of these changes. However in the case of the present-day Atlantic storm-track, the growth rate of these modes is found to be very low compared to the other cases. A complementary analysis evaluates the importance of non-modal growth, in the form of downstream development of perturbations, for each of the storm-tracks. This type of growth is found to be especially important in the case of the present-day Atlantic storm-track."
"7102926738;7402349939;","Frontal interaction with mesoscale topography",1999,"10.1175/1520-0469(1999)056<3544:FIWMT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033569072&doi=10.1175%2f1520-0469%281999%29056%3c3544%3aFIWMT%3e2.0.CO%3b2&partnerID=40&md5=938ef7c07fd9e4c2ad1f1608c7e2fab8","A two-dimensional, hydrostatic, nearly adiabatic primitive equation model is used to study the evolution of a front passing across topography. Frontogenesis is forced by shearing deformation associated with the nonlinear evolution of an Eady wave. This study extends previous work by including an upper-level potential vorticity (PV) anomaly and a growing baroclinic wave in a baroclinically unstable basic state. Results for the Eady wave simulations show that the mountain retards and blocks the approaching front at the surface while the upper-level PV anomaly associated with the front moves across the domain unaffected. Warm advection ahead of the lee trough forces convergence and cyclonic vorticity growth near the base of the lee slope. This vorticity growth is further encouraged by the approach of the upper-level PV anomaly. The upper-level PV anomaly then couples with this new surface vorticity center and propagates downstream. The original surface front remains trapped on the windward slope. Thus when the upstream blocking is strong, frontal propagation is discontinuous across the ridge. This evolution occurs for tall mountains and narrow mountains, as well as weak fronts. For low mountains, wide mountains, and strong fronts, only weak retardation is observed on the windward slope. The surface front remains coupled with the upper-level PV anomaly. The front moves continuously across the mountain. The net result, regardless of mountain size and shape, is that the front reaches the base of the lee slope stronger, sooner, and with a decreased cross-front scale compared to the 'no-mountain' case. Well downstream of the mountain, no position change of the surface front is observed.A two-dimensional, hydrostatic, nearly adiabatic primitive equation model i used to study the evolution of a front passing across topography. Frontogenesis is forced by shearing deformation associated with the nonlinear evolution of an Eady wave. This study extends previous work by including an upper-level potential vorticity (PV) anomaly and a growing baroclinic wave in a baroclinically unstable basic state. Results for the Eady wave simulations show that the mountain retards and blocks the approaching front at the surface while the upper-level PV anomaly associated with the front moves across the domain unaffected. Warm advection ahead of the lee trough forces convergence and cyclonic vorticity growth near the base of the lee slope. This vorticity growth is further encouraged by the approach of the upper-level PV anomaly. The upper-level PV anomaly then couples with this new surface vorticity center and propagates downstream. The original surface front remains trapped on the windward slope. Thus when the upstream blocking is strong, frontal propagation is discontinuous across the ridge. This evolution occurs for tall mountains and narrow mountains, as well as weak fronts. For low mountains, wide mountains, and strong fronts, only weak retardation is observed on the windward slope. The surface front remains coupled with the upper-level PV anomaly. The front moves continuously across the mountain. The net result, regardless of mountain size and shape, is that the front reaches the base of the lee slope stronger, sooner, and with a decreased cross-front scale compared to the 'no-mountain' case. Well downstream of the mountain, no position change of the surface front is observed."
"7004069241;","André robert (1929–1993): His pioneering contributions to numerical modelling",1997,"10.1080/07055900.1997.9687341","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27544501216&doi=10.1080%2f07055900.1997.9687341&partnerID=40&md5=96966ba0f362fe480e106d493882c109","The pioneering contributions of André Robert to numerical modelling are reviewed. Highlights include: his early work on spectral modelling; the introduction of a weak time filter to permit extended integrations of models for climate modelling; the development of highly-efficient semi-implicit semi-Lagrangian time integration schemes; the extension of these techniques for efficiently integrating the hydrostatic primitive equations to the fully-elastic Euler equations; and the identification of and solution to deficiencies in the traditional approaches to applying lateral boundary conditions in limited area models. These contributions all have one thing in common. They are the result of having reduced a complex problem to its essence in order to properly understand its origin, and thereby develop a conceptually simple solution that not only addresses the problem in its simplified context but also in the original complex one. His inspirational contributions have profoundly influenced, and continue to influence, the development by the international geophysical fluid dynamics community of atmospheric and oceanic models for applications and research in weather, climate and air quality. André Robert was a true pioneer of numerical modelling and Will be sorely missed, but his contributions Will endure for many years to come. © 1997 Taylor & Francis Group, LLC."
"57212856885;7102636922;6701672112;","Impact of ocean circulation on regional polar climate simulations using the Arctic region climate system model",1997,"10.3189/s026030550001404x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031396375&doi=10.3189%2fs026030550001404x&partnerID=40&md5=e3d19f2a1c683be5cfe8be67ac9d262d","Global climate models have pointed to the polar regions as very sensitive areas in response to climate change. However, these models often do not contain representations of processes peculiar to the polar regions such as dynamic sea ice, permafrost, and Arctic stratus clouds. Further, global models do not have the resolution necessary to model accurately many of the important processes and feedbacks. Thus, there is a need for regional climate models of higher resolution. One such model (ARCSyM) has been developed by A. Lynch and W. Chapman. This model incorporates the NCAR Regional Climate Model (RegCM2) with the addition of Flato-Hibler cavitating fluid sea-ice dynamics and Parkinson-Washington ice thermodynamic formulation. Recently work has been conducted to couple a mixed-layer ocean to the atmosphere-ice model, and a three-dimensional (3-D) dynamical ocean model, in this case the S-Coordinate Primitive Equation Model (SPEM), to the ice model. Simulations including oceanic circulation will allow investigations of the feedbacks involved in fresh-water runoff from sea-ice melt and sea-ice transport. Further, it is shown that the definition of the mixed-layer depth has significant impact on ice thermodynamics."
"6603432771;7004247643;7005960075;","Combining data and a global primitive equation ocean general circulation model using the adjoint method",1996,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030435304&partnerID=40&md5=a2ffc02728d838ca0c2d261aeffb0a6f","A Primitive Equation Ocean General Circulation Model (PE OGCM) in a global configuration similar to that used in coupled ocean-atmosphere models is fitted to climatological data using the adjoint method. It is demonstrated that a successful assimilating of data into a fully complex PE OGCM critically depends on a very careful choice of the surface boundary condition formulation, on the optimization problem formulation, and on the initial guess for the optimization solution."
"7006695342;57206232972;6603466189;7005256983;","The dynamical basis of regional vertical motion fields surrounding localized tropical heating",1995,"10.1175/1520-0442(1995)008<1217:TDBORV>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029505163&doi=10.1175%2f1520-0442%281995%29008%3c1217%3aTDBORV%3e2.0.CO%3b2&partnerID=40&md5=0d4cf689f80fbec9487dbd5d298d353f","A series of real-data integrations of the National Center for Atmospheric Research Community Climate Model with tropical heat anomalies display regions of pronounced subsidence and drying surrounding the anomaly. The present emphasis is upon subsidence and drying centers located several thousand kilometers westward and poleward of the heating. These features are repeatedly found in several different series of medium to extended range forecast experiments, including cases of tropical Atlantic heating and tropical east Pacific heating. This highly predictable sinking response is established within the first five days of these integrations. The normal modes of a set of primitive equations linearized about a resting basic state are used to partition model response into gravity-inertia and Rossby modes. The results show that most of the vertical motion response can be explained by gravity-mode contributions. -from Authors"
"7003531755;7004074265;","Convective interaction with dynamics in a linear primitive equation model",1994,"10.1175/1520-0469(1994)051<1307:CIWDIA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028554068&doi=10.1175%2f1520-0469%281994%29051%3c1307%3aCIWDIA%3e2.0.CO%3b2&partnerID=40&md5=fbe8faf0468f60668762605d9c86dc97","A new global atmosphere model purpose designed for climate studies is introduced. The model is solved in terms of the normal modes of the linearized primitive equations on a sphere, which allows use of long time steps without introducing computational instability of phase errors of the linear wave components. The model is tested by attempting to simulate the tropical intraseasonal oscillation using an idealized sea surface temperature distribution. Simple treatments of radiation and boundary-layer processes are used together with the much more complete Betts-Miller convection scheme. -from Authors"
"7201483081;57203598636;6602451467;6603552038;55428373200;","Numerical investigations with a hybrid isentropic-sigma model. Part I: normal-mode characteristics",1991,"10.1175/1520-0469(1991)048<2005:NIWAHI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026277206&doi=10.1175%2f1520-0469%281991%29048%3c2005%3aNIWAHI%3e2.0.CO%3b2&partnerID=40&md5=4c053ad290fb8c52c0744ce055d5ac6d","In the validation experiment of a hybrid isentropic-sigma coordinate primitive equation model developed at the University of Wisconsin (the UW θ-σ model), an initial value technique is used to investigate numerically the normal-mode characteristics of baroclinically amplifying disturbances over a spectrum of meteorologically significant wavelengths. The experiments are designed to determine the impact of coupling an isentropic-coordinate free atmospheric domain to a sigma-coordinate planetary boundary layer (PBL) on the normal-mode characteristics. -from Authors"
"7102577095;","Tropical influences on the predictability of ultralong waves.",1980,"10.1175/1520-0469(1980)037<1141:TIOTPO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019184223&doi=10.1175%2f1520-0469%281980%29037%3c1141%3aTIOTPO%3e2.0.CO%3b2&partnerID=40&md5=fb96301836b84b3149941761e8be0b24","Some implications of predicatbility theory for ultralong waves are examined in an ensemble of real-data forecasts carried out with a primitive-equation numerical model in both global and hemispheric configurations. Adverse tropical influences on middle-latitude forecast skill are essentially confined to the ultra-long waves (zonal wavenumbers 1-3). These effects of tropical deficiencies in the pridiction model and in the initial data provide a patial explanation for the poor skill of typical acutal forecasts of ultralong waves, relative to the skill expected on the basis of predictability theory. -from Author National Center for Atmospheric Research boulder, CO 80307."
"7004657713;7004002518;","Upslope enhanced extreme rainfall events over the Canadian Western Plains: a mesoscale numerical simulation.",1979,"10.1175/1520-0493(1979)107<0650:UEEREO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0018688211&doi=10.1175%2f1520-0493%281979%29107%3c0650%3aUEEREO%3e2.0.CO%3b2&partnerID=40&md5=b7686ec08ab98ec22d049b59d5ab4adf","A limited-area numerical model, previously applied to the study of cold easterly circulations over the Canadian Western Plains, is used to simulate upslope enhanced extreme rainfall events over the Saskatchewan River and adjacent drainage basins. Following Lavoie (1972) the atmospheric structure was represented by three layers; a constant flux layer in contact with earth's surface, a well-mixed planetary boundary layer capped by an inversion, and a deep stratum of overlying stable air. The governing primitive equations were averaged through the depth of the mixed layer with interactions between the mixed layer and both the underlying and overlying air being suitably parameterized. The model sucessfully simulated mean persistent (3-day) extreme rainfall distributions associated with occluded cyclones over the Saskatchewan River Basin. - from Authors"
"55176818100;7004479957;","Spatially Extended Tests of a Neural Network Parametrization Trained by Coarse-Graining",2019,"10.1029/2019MS001711","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070870530&doi=10.1029%2f2019MS001711&partnerID=40&md5=8de2eb403fdab22ecc47983fc4c761ae","General circulation models (GCMs) typically have a grid size of 25–200 km. Parametrizations are used to represent diabatic processes such as radiative transfer and cloud microphysics and account for subgrid-scale motions and variability. Unlike traditional approaches, neural networks (NNs) can readily exploit recent observational data sets and global cloud-system resolving model (CRM) simulations to learn subgrid variability. This article describes an NN parametrization trained by coarse-graining a near-global CRM simulation with a 4-km horizontal grid spacing. The NN predicts the residual heating and moistening averaged over (160 km)2 grid boxes as a function of the coarse-resolution fields within the same atmospheric column. This NN is coupled to the dynamical core of a GCM with the same 160-km resolution. A recent study described how to train such an NN to be stable when coupled to specified time-evolving advective forcings in a single-column model, but feedbacks between NN and GCM components cause spatially extended simulations to crash within a few days. Analyzing the linearized response of such an NN reveals that it learns to exploit a strong synchrony between precipitation and the atmospheric state above 10 km. Removing these variables from the NN's inputs stabilizes the coupled simulations, which predict the future state more accurately than a coarse-resolution simulation without any parametrizations of subgrid-scale variability, although the mean state slowly drifts. ©2019. The Authors."
"54983307800;26666431500;22934904700;7202954964;","Single precision in the dynamical core of a nonhydrostatic global atmospheric model: Evaluation using a baroclinic wave test case",2018,"10.1175/MWR-D-17-0257.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042397949&doi=10.1175%2fMWR-D-17-0257.1&partnerID=40&md5=c69556eed7ef3beaa464df54bc107a2b","Reducing the computational cost of weather and climate simulations would lower electric energy consumption. From the standpoint of reducing costs, the use of reduced precision arithmetic has become an active area of research. Here the impact of using single-precision arithmetic on simulation accuracy is examined by conducting Jablonowski and Williamson's baroclinic wave tests using the dynamical core of a global fully compressible nonhydrostatic model. The model employs a finite-volume method discretized on an icosahedral grid system and its mesh size is set to 220, 56, 14, and 3.5 km. When double-precision arithmetic is fully replaced by single-precision arithmetic, a spurious wavenumber-5 structure becomes dominant in both hemispheres, rather than the expected baroclinic wave growth only in the Northern Hemisphere. It was found that this spurious wave growth comes from errors in the calculation of gridcell geometrics. Therefore, an additional simulation was conducted using double precision for calculations that only need to be performed for model setup, including calculation of gridcell geometrics, and single precision everywhere else, meaning that all calculations performed each time step used single precision. In this case, the model successfully simulated the growth of the baroclinic wave with only small errors and a 46% reduction in runtime. These results suggest that the use of single-precision arithmetic will allow significant reduction of computational costs in next-generation weather and climate simulations using a fully compressible nonhydrostatic global model with the finite-volume method. © 2018 American Meteorological Society."
"56033201200;6603871013;11939722900;56341281700;7006760857;57189581196;","Moving towards a wave-resolved approach to forecasting mountain wave induced clear air turbulence",2017,"10.1002/met.1656","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85022339037&doi=10.1002%2fmet.1656&partnerID=40&md5=2a2570f6191a1a5df28a30093a2a93ee","Mountain wave breaking in the lower stratosphere is one of the major causes of atmospheric turbulence encountered in commercial aviation, which in turn is the cause of most weather-related aircraft incidents. In the case of clear air turbulence (CAT), there are no visual clues and pilots are reliant on operational forecasts and reports from other aircraft. Traditionally mountain waves have been sub-grid-scale in global numerical weather prediction (NWP) models, but recent developments in NWP mean that some forecast centres (e.g. the UK Met Office) are now producing operational global forecasts that resolve mountain wave activity explicitly, allowing predictions of mountain wave induced turbulence with greater accuracy and confidence than previously possible. Using a bespoke turbulent kinetic energy diagnostic, the Met Office Unified Model (MetUM) is shown to produce useful forecasts of mountain CAT during three case studies over Greenland, and to outperform the current operational Met Office CAT prediction product (the World Area Forecast Centre (WAFC) London gridded CAT product) in doing so. In a long term, 17-month, verification, MetUM forecasts yield a turbulence prediction hit rate of 80% with an accompanying false alarm rate of under 40%. These skill scores are a considerable improvement on those reported for the mountain wave component of the WAFC product, although no direct comparison is available. The major implication of this work is that sophisticated global NWP models are now sufficiently advanced to provide skilful forecasts of mountain wave turbulence. © 2017 Crown Copyright, Met Office Meteorological Applications © 2017 Royal Meteorological Society"
"13406399300;7406243250;8339569900;31067496800;7202192265;57002623400;54581048500;","CAM-SE-CSLAM: Consistent coupling of a conservative semi-lagrangian finite-volume method with spectral element dynamics",2017,"10.1175/MWR-D-16-0258.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013982485&doi=10.1175%2fMWR-D-16-0258.1&partnerID=40&md5=111270e97eedc56010b2a261098ce77a","An algorithm to consistently couple a conservative semi-Lagrangian finite-volume transport scheme with a spectral element (SE) dynamical core is presented. The semi-Lagrangian finite-volume scheme is the Conservative Semi-Lagrangian Multitracer (CSLAM), the SE dynamical core is the National Center for Atmospheric Research (NCAR)'s Community Atmosphere Model-Spectral Elements (CAM-SE). The primary motivation for coupling CSLAM with CAM-SE is to accelerate tracer transport for multitracer applications. The coupling algorithm result is an inherently mass-conservative, shape-preserving, consistent (for a constant mixing ratio, the CSLAM solution reduces to the SE solution for air mass) transport that is efficient accurate. This is achieved by first deriving formulas for diagnosing SE airmass flux through the CSLAM control volume faces. Thereafter, the upstream Lagrangian CSLAM areas are iteratively perturbed to match the diagnosed SE airmass flux, resulting in an equivalent upstream Lagrangian grid that spans the sphere without gaps or overlaps (without using an expensive search algorithm). This new CSLAM algorithm is not specific to airmass fluxes provided by CAM-SE but applies to any airmass fluxes that satisfy the Lipshitz criterion for which the Courant number is less than one. © 2017 American Meteorological Society."
"7006622255;24490844700;7006550959;7102096431;6701313416;55919261400;","PLASIM-GENIE v1.0: A new intermediate complexity AOGCM",2016,"10.5194/gmd-9-3347-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988735470&doi=10.5194%2fgmd-9-3347-2016&partnerID=40&md5=4e2b0e35b24d5295e6b619e0c8cfff71","We describe the development, tuning and climate of Planet Simulator (PLASIM)-Grid-ENabled Integrated Earth system model (GENIE), a new intermediate complexity Atmosphere-Ocean General Circulation Model (AOGCM), built by coupling the Planet Simulator to the ocean, sea-ice and land-surface components of the GENIE Earth system model. PLASIM-GENIE supersedes GENIE-2, a coupling of GENIE to the Reading Intermediate General Circulation Model (IGCM). The primitive-equation atmosphere includes chaotic, three-dimensional (3-D) motion and interactive radiation and clouds, and dominates the computational load compared to the relatively simpler frictionalgeostrophic ocean, which neglects momentum advection. The model is most appropriate for long-timescale or large ensemble studies where numerical efficiency is prioritised, but lack of data necessitates an internally consistent, coupled calculation of both oceanic and atmospheric fields. A 1000-year simulation with PLASIM-GENIE requires approximately 2 weeks on a single node of a 2.1 GHz AMD 6172 CPU. We demonstrate the tractability of PLASIM-GENIE ensembles by deriving a subjective tuning of the model with a 50-member ensemble of 1000-year simulations. The simulated climate is presented considering (i) global fields of seasonal surface air temperature, precipitation, wind, solar and thermal radiation, with comparisons to reanalysis data; (ii) vegetation carbon, soil moisture and aridity index; and (iii) sea surface temperature, salinity and ocean circulation. Considering its resolution, PLASIM-GENIE reproduces the main features of the climate system well and demonstrates usefulness for a wide range of applications. © 2016 Author(s)."
"31067496800;36992744000;15765007300;","Analytical initial conditions and an analysis of baroclinic instability waves in f - and β-plane 3D channel models",2015,"10.1002/qj.2583","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950107428&doi=10.1002%2fqj.2583&partnerID=40&md5=9fe06bf6854a3b684cd1273c0c35bfc7","The article presents a description of idealized, balanced initial conditions for dry 3D channel models with either the hydrostatic or non-hydrostatic shallow-atmosphere equation set. Both the analytical expressions for an f- and β-plane configuration are provided and possible variations are discussed. The initialization with an overlaid perturbation is then used for baroclinic instability studies which can serve either as a test case for the numerical discretization or for physical science investigations such as the impact of the Coriolis parameter on the evolution of baroclinic waves. Example results for two channel models are presented: the MCore and the Weather Research and Forecasting (WRF) models. The simulations show that the evolution of the baroclinic wave on the β-plane is more unstable than the corresponding f-plane configuration, experiencing a faster linear growth rate of the most unstable wave mode, a shorter most unstable wavelength, a narrower meridional width, and an earlier breaking of the baroclinic wave. A theoretical analysis based on linearized quasi-geostrophic (QG) theory sheds light on these findings. It is shown that the simulated baroclinic instability waves on both the f- and β-plane closely match the predicted wavelength, shape and linear growth rate obtained from the QG theory, thus validating the model results. © 2015 Royal Meteorological Society."
"35750631600;57212494429;7403656261;7202746265;","Response of OceanSat II scatterometer winds in the Bay of Bengal circulation",2014,"10.1080/01431161.2014.926423","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905730095&doi=10.1080%2f01431161.2014.926423&partnerID=40&md5=fc367de3c4c69433d1ec4259b2a0f542","Surface wind is one of the major forcing factors in any ocean circulation model. The response of satellite-derived OceanSat II scatterometer (OSCAT) winds during spring (February and March) 2010 in the Bay of Bengal (BOB) surface circulation is described in this study. Wind stress is calculated from wind speed derived from OSCAT by the bulk-aerodynamic formula. The Regional Ocean Modeling System is used in this study because it is a free-surface, terrain-following, primitive-equations ocean model widely used by the scientific community for a diverse range of applications. The model is used after a climatological simulation with Comprehensive Ocean-Atmosphere Data Set (COADS) forcing when the model simulation reached the annual cycle. The paper also carried out a comparative study of National Centers for Environmental Prediction (NCEP) forcing over the same time period. The comparison of model-simulated surface temperature to National Oceanic and Atmospheric Administration (NOAA) sea surface temperature (SST) indicates that meso-scale features in the BOB are resolved due to the finer resolution of this model. Comparisons of water mass characteristics to the available ARGO floats show good agreement in different locations within the BOB. This study confirms the usefulness of OSCAT winds in simulating the meso-scale feature in the BOB. © 2014 Taylor & Francis."
"6505799826;7006614214;","Jupiter's Great Red Spot: Fine-scale matches of model vorticity patterns to prevailing cloud patterns",2013,"10.1016/j.icarus.2013.03.026","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84876995058&doi=10.1016%2fj.icarus.2013.03.026&partnerID=40&md5=5b43b8f01fd6f8cc9f2584ce87a92ffd","We report on a set of six new matches between fine-scale features in the vorticity field of a three-dimensional (3D), primitive-equation, finite-difference model of Jupiter's Great Red Spot that includes no clouds or cloud physics, and quasi-permanent structures in reflected visible-band images of the clouds. These add to similar success by Cho et al. (Cho, J., de la Torre Juárez, M., Ingersoll, A.P., Dritschel, D.G. [2001]. J. Geophys. Res. 106, 5099-5106), who earlier captured four characteristic features of the GRS, also reproduced here, using a 3D quasi-geostrophic, cloud-free contour-dynamics model. In that study and this, the key enabling model attribute is sufficient horizontal resolution, rather than the moist-convective and cloud-microphysics processes often required to match the patterns of clouds in terrestrial hurricanes. The only significant feature that these dry models do not capture is the episodic moist-convective plumes seen in the northwest quadrant adjacent to the GRS. We initialize with Jupiter's averaged zonal winds plus an approximately balanced, smooth 3D ellipsoidal anticyclone. The threshold horizontal grid-resolution to obtain the fine-scale matches is approximately δy/Ld≲0.15, where δy≲300km is the meridional grid spacing and Ld~2000km the Rossby deformation length. For models with this or finer horizontal resolution, the best correspondence with observations is reached after about six vortex turnaround times from initialization (~30 Earth days), but good facsimiles of nearly all the studied features appear after only 1.5 turnaround times (~7-8days). We conclude that in images of Jupiter, it is not accurate to associate clouds with upward motion, since these dry models reproduce the observed cloud patterns without this association, and indeed the synoptic-scale vertical motions in the model, as well as those deduced from observations, do not at all correspond to the observed cloud patterns. Instead, Jupiter's cloud-top patterns indicate the effects of local shear in the manner of passive-tracer fields. As a corollary, the water clouds on Jupiter, which lie unseen below its visible clouds, are the only ones on the planet likely to correlate with upwelling in the manner that clouds do on Earth. The next step is to extend studies such as this past the reflected visible band, for example to include the GRS's 5-μm emission bright collar, which may require the inclusion of cloud physics to enable the successful simulation of large voids. © 2013 Elsevier Inc.."
"26430995400;56850959100;","The vertical structure of the eddy diffusivity and the equilibration of the extratropical atmosphere",2013,"10.1175/JAS-D-12-086.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84877327207&doi=10.1175%2fJAS-D-12-086.1&partnerID=40&md5=ff303cf36b3ae90969bc3d26cf112c60","Observations suggest that the time- and zonal-mean state of the extratropical atmosphere adjusts itself such that the so-called ""criticality parameter"" (which relates the vertical stratification to the horizontal temperature gradient) is close to one. T. Schneider has argued that the criticality parameter is kept near one by a constraint on the zonal momentum budget in primitive equations. The constraint relies on a diffusive closure for the eddy flux of potential vorticity (PV) with an eddy diffusivity that is approximately constant in the vertical. The diffusive closure for the eddy PV flux, however, depends crucially on the definition of averages along isentropes that intersect the surface. It is argued that the definition favored by Schneider results in eddy PV fluxes whose physical interpretation is unclear and that do not satisfy the proposed closure in numerical simulations. An alternative definition, first proposed by T.-Y. Koh and R. A. Plumb, is preferred. A diffusive closure for the eddy PV flux under this definition is supported by analysis of the PV variance budget and can be used to close the near-surface zonal momentum budget in idealized numerical simulations. Following this approach, it is shown that O(1) criticalities are obtained if the eddy diffusivity decays from its surface value to about zero over the depth of the troposphere, which is likely to be the case in Earth's atmosphere. Large criticality parameters, however, are possible if the eddy diffusivity decays only weakly in the vertical, consistent with results from quasigeostrophic models. This provides theoretical support for recent numerical studies that have found supercritical mean states in primitive equation models. © 2013 American Meteorological Society."
"7004093651;7404187480;","A geometrical view of the shallow-atmosphere approximation, with application to the semi-Lagrangian departure point calculation",2013,"10.1002/qj.1962","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84873313438&doi=10.1002%2fqj.1962&partnerID=40&md5=8a440de2838c8db823695b809ca59c6b","The widely used shallow-atmosphere approximation is a geometrical approximation in which the metric departs from the usual Euclidean metric. This leads to a number of important consequences: shallow-atmosphere space is intrinsically curved (i.e. non-Euclidean), geodesics are not unique, the status of the centre of the Earth is uncertain, and position vectors are not well-defined. Vector semi-Lagrangian numerical models that use the shallow-atmosphere approximation must allow explicitly for the non-Euclidean geometry. During early testing of a new semi-implicit, semi-Lagrangian dynamical core, a semi-implicit (Crank-Nicolson) discretization of the vector departure point equation was found to lead to an instability in deep-atmosphere (i.e. Euclidean) geometry, but not in shallow-atmosphere geometry. The instability can be avoided by an alternative treatment in which the departure point equation is projected onto its horizontal and vertical components before discretization. Interestingly, this stable treatment of the deep-atmosphere case makes use of much of the mathematical machinery of the shallow-atmosphere departure point calculation. © 2012 Royal Meteorological Society and British Crown the Met Office."
"7003745084;55830654800;55279353500;7006453728;","Modeling the vulnerability of an urban groundwater system due to the combined impacts of climate change and management scenarios",2013,"10.1175/2012EI000499.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882680206&doi=10.1175%2f2012EI000499.1&partnerID=40&md5=9542d407a2554673c65157adb55f05b1","Climate change impact on a groundwater-dependent small urban town has been investigated in the semiarid hard rock aquifer in southern India. A distributed groundwater model was used to simulate the groundwater levels in the study region for the projected future rainfall (2012-32) obtained from a general circulation model (GCM) to estimate the impacts of climate change and management practices on groundwater system. Management practices were based on the human-induced changes on the urban infrastructure such as reduced recharge from the lakes, reduced recharge from water and wastewater utility due to an operational and functioning underground drainage system, and additional water extracted by the water utility for domestic purposes. An assessment of impacts on the groundwater levels was carried out by calibrating a groundwater model using comprehensive data gathered during the period 2008-11 and then simulating the future groundwater level changes using rainfall from six GCMs [Institute of Numerical Mathematics Coupled Model, version 3.0 (INM-CM.3.0); L'Institut Pierre-Simon Laplace Coupled Model, version 4 (IPSL-CM4); Model for Interdisciplinary Research on Climate, version 3.2 (MIROC3.2); ECHAM and the global Hamburg Ocean Primitive Equation (ECHO-G); Hadley Centre Coupled Model, version 3 (HadCM3); and Hadley Centre Global Environment Model, version 1 (HadGEM1)] that were found to show good correlation to the historical rainfall in the study area. The model results for the present condition indicate that the annual average discharge (sum of pumping and natural groundwater outflow) was marginally or moderately higher at various locations than the recharge and further the recharge is aided from the recharge from the lakes. Model simulations showed that groundwater levels were vulnerable to the GCM rainfall and a scenario of moderate reduction in recharge from lakes. Hence, it is important to sustain the induced recharge from lakes by ensuring that sufficient runoff water flows to these lakes. © 2013."
"16432829300;15724305400;7004418377;","Vertical mixing and coherent anticyclones in the ocean: The role of stratification",2010,"10.5194/npg-17-37-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953008889&doi=10.5194%2fnpg-17-37-2010&partnerID=40&md5=b3432a69cb9459f761a4d8da650460fc","The role played by wind-forced anticyclones in the vertical transport and mixing at the ocean mesoscale is investigated with a primitive-equation numerical model in an idealized configuration. The focus of this work is to determine how the stratification impacts such transport. The flows, forced only at the surface by an idealized wind forcing, are predominantly horizontal and, on average, quasigeostrophic. Inside vortex cores and intense filaments, however, the dynamics is strongly ageostrophic. Mesoscale anticyclones appear as islands of increased penetration of wind energyinto the ocean interior and they represent the maxima of available potential energy. The amount of available potential energy is directly correlated with the degree of stratification. The wind energy injected at the surface is transferred at depth through the generation and subsequent straining effect of Vortex Rossby Waves (VRWs), and through near-inertial internal oscillations trapped inside anticyclonic vortices. Both these mechanisms are affected by stratification. Stronger transfer but larger confinement close to the surface is found when the stratification is stronger. For weaker stratification, vertical mixing close to the surface is less intense but below about 150 m attains substantially higher values due to an increased contribution of both VRWs, whose time scale is on the order of few days, and of near-inertial motions, with a time scale of few hours. © 2008 Author(s)."
"37019381400;","Synoptic eddy feedback and air-sea interaction in the North Atlantic region",2007,"10.1007/s00382-007-0256-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548633759&doi=10.1007%2fs00382-007-0256-7&partnerID=40&md5=b42071ee0b72134a9261601c740be0e3","This paper explores the role of synoptic eddy feedback in the air-sea interaction in the North Atlantic region, particularly the interaction between the North Atlantic Oscillation (NAO) and the North Atlantic sea surface temperature anomalies (SSTA) tripole. A linearized five-layer primitive equation atmospheric model with synoptic eddy and low-frequency flow (SELF) interaction is coupled with a linearized oceanic mixed-layer model to investigate this issue. In this model, the ""climatological"" storm track/activity (or synoptic eddy activity) is characterized in terms of spatial structures, variances, decay time scales and propagation speeds through the complex empirical orthogonal function (CEOF) analysis on the observed data, which provides a unique tool to investigate the role of synoptic eddy feedback in the North Atlantic air - sea coupling. Model experiments show that the NAO-like atmospheric circulation anomalies can produce tripole-like SSTA in the North Atlantic Ocean, and the tripole-like SSTA can excite a NAO-like dipole with an equivalent barotropic structure in the atmospheric circulation, which suggests a positive feedback between the NAO and the SSTA tripole. This positive feedback makes the NAO/SSTA tripole-like mode be the leading mode of the coupled dynamical system. The synoptic eddy feedback plays an essential role in the origin of the NAO/SSTA tripole-like leading mode and the equivalent barotropic structure in the atmosphere. Without synoptic eddy feedback, the atmosphere has a baroclinic structure in the response field to the tripole-like SSTA forcing, and the leading mode of the dynamic system does not resemble NAO/SSTA tripole pattern. © Springer-Verlag 2007."
"35108659500;6602847318;","A global Eta model on quasi-uniform grids",2007,"10.1002/qj.17","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247233962&doi=10.1002%2fqj.17&partnerID=40&md5=3ee01d8062e14c43b6c8aaac4f279446","The application of quasi-uniform grids in global models of the atmosphere is an attempt to increase the computational efficiency by a more cost-effective exploitation of the computing infrastructure. This paper describes the development of a global version of NCEP's regional, step-coordinate, Eta model on two quasi-uniform grids: cubic and octagonal. The governing equations are expressed in a general curvilinear form, so that the cubic and the octagonal versions of the model share the same code in spite of different mapping of the computational domain. The dynamical core of the derived global Eta model is successfully tested in the benchmark test of Held and Suarez. The model with the step-wise formulation of the terrain and full physics is integrated in a series of tests with real data, and the results are compared both with the analysis and the results of the regional Eta model. Copyright © 2007 Royal Meteorological Society."
"7401651825;7202623257;","A nonhydrostatic primitive-equation model for studying small-scale processes: An object-oriented approach",2006,"10.1016/j.csr.2006.01.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33746312434&doi=10.1016%2fj.csr.2006.01.018&partnerID=40&md5=26cff6f66d3435827deb787b5e2cb7fa","A nonhydrostatic model for simulating small-scale processes in the ocean is described. The model is developed using the object-oriented approach. The system is modeled as a set of cooperating objects to manage both the behavioral and information complexity associated with modeling oceanic processes. Objects are storage variables that are created based on classes. A class defines the variables and routines that are members of all objects of that class. The program accesses data stored in these objects using the defined interfaces. Because both data and function are accessed through objects, the model is better organized than one written in a procedural language. The program is easier to understand, debug, maintain, and evolve. Abstraction of the data in the nonhydrostatic model is implemented in both C++ and Matlab. Three examples obtained from the Matlab version of the code illustrate the capabilities of the model in cases where nonhydrostatic effects are important. The model successfully simulates nonhydrostatic atmospheric lee waves, internal waves at a discharge plume, and internal solitary waves generated by tidal flow over a sill. These examples show that the model is capable of studying strongly nonlinear, nonhydrostatic flow processes. © 2006 Elsevier Ltd. All rights reserved."
"7004247643;","Uncertainties in thermohaline circulation response to greenhouse warming",2000,"10.1029/2000GL006108","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033625909&doi=10.1029%2f2000GL006108&partnerID=40&md5=ba1208512e6bc15b24b8b6705ca73d58","The uncertainty in the response of the thermohaline circulation to greenhouse forcing due to the use of flux adjustments in coupled ocean-atmosphere models is evaluated. This is done by using a different yet physically justifiable flux adjustment procedure and examining its effect on the thermohaline response to greenhouse forcing in a three dimensional primitive equations coupled ocean atmosphere general circulation model. It is found that while the initial thermohaline circulation weakening is robust, its eventual recovery which is seen in some coupled model simulations may be more sensitive to the details of the flux adjustment procedure and may therefore be less certain."
"7005677595;21742961600;","Responses of different nonhydrostatic, pressure-coordinate models to orographic forcing",1999,"10.1175/1520-0469(1999)056<2553:RODNPC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344771148&doi=10.1175%2f1520-0469%281999%29056%3c2553%3aRODNPC%3e2.0.CO%3b2&partnerID=40&md5=ca5ef19b91687faec7ee39cba57c8b9c","Estimation of accuracy of different high-resolution, sound-filtered, pressure-coordinate models is carried out by modeling their response to orographic forcing. Evaluated models are the elastic nonhydrostatic model (EFM), the anelastic nonhydrostatic model (AEM), and the hydrostatic primitive equation model (HSM). These models are compared to the exact, nonfiltered, nonhydrostatic, pressure-coordinate dynamics (ExM). All model equations are linearized, a wave equation for vertical displacements of air particles is derived, and exact analytical stationary solutions for each model are compared for uniform flow over given smooth orography (bell-shaped mountain). These linear solutions reveal that compressible (ExM, EFM) and incompressible (AEM, HSM) models are different at long horizontal scales l approx. 1000 km. Differences are especially large in the vertical velocity field (up to 100%) at the medium and upper levels of the atmosphere, where incompressible models give systematic reductions of wave amplitudes. All models are effectively incompressible and coincide with high precision in the region 10 km < l < 500-700 km. As expected, the first critical scale is l approx. 10 km, below which the HSM fails. The second critical scale is at l approx. 100 m (moderate winds) to l approx. 1000 m (strong winds), below which the AEM becomes inconsistent with the other models in temperature fluctuation presentation. The EFM represents a universal approximation, valid at all scales.Estimation of accuracy of different high-resolution, sound-filtered, pressure-coordinate models is carried out by modeling their response to orographic forcing. Evaluated models are the elastic nonhydrostatic model (EFM), the anelastic nonhydrostatic model (AEM), and the hydrostatic primitive equation model (HSM). These models are compared to the exact, nonfiltered, nonhydrostatic, pressure-coordinate dynamics (ExM). All model equations are linearized, a wave equation for vertical displacements of air particles is derived, and exact analytical stationary solutions for each model are compared for uniform flow over given smooth orography (bell-shaped mountain). These linear solutions reveal that compressible (ExM, EFM) and incompressible (AEM, HSM) models are different at long horizontal scales l ~ 1000 km. Differences are especially large in the vertical velocity field (up to 100%) at the medium and upper levels of the atmosphere, where incompressible models give systematic reductions of wave amplitudes. All models are effectively incompressible and coincide with high precision in the region 10 km < l < 500-700 km. As expected, the first critical scale is l ~ 10 km, below which the HSM fails. The second critical scale is at l ~ 100 m (moderate winds) to l ~ 1000 m (strong winds), below which the AEM becomes inconsistent with the other models in temperature fluctuation presentation. The EFM represents a universal approximation, valid at all scales."
"57207141014;57200779562;","Numerical simulations of maritime frontogenesis",1997,"10.1175/1520-0469(1997)054<0314:NSOMF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030766916&doi=10.1175%2f1520-0469%281997%29054%3c0314%3aNSOMF%3e2.0.CO%3b2&partnerID=40&md5=e471a94857a34a65f2e5c8b57c350a19","A hydrostatic primitive equation model initialized in a highly baroclinically unstable state was used to simulate maritime cyclogenesis and frontogenesis. In order to identify boundary layer physical processes important in maritime frontogenesis, several different simulations were performed. In an effort to isolate impacts due solely to the boundary layer, moist processes were not included. An adiabatic and inviscid simulation provided the control for these experiments. Two different boundary layer parameterizations were used: a K-theory parameterization featuring Richardson-number-dependent eddy diffusivity and a second-order closure scheme with prognostic equations for the turbulence quantities. Results indicated that strong warm and cold fronts formed in the adiabatic and inviscid case but that the vertical motion fields were weak. In the K-theory simulation, the results were somewhat more realistic with stronger vertical motion. In both the K-theory and second-order closure simulations, the boundary layer in the cold air was highly unstable and deep mixed layers formed in this region with a large generation of turbulence. The largest cross-front temperature gradients existed in the frontal zone above the mixed layer. These structures were in qualitative agreement with observations of maritime cold fronts over the northwest Pacific Ocean. The second-order closure simulations produced a shallower mixed layer in the cold air with a stronger, more narrow front and large vertical motion. These simulations were more consistent with observations. Results from the second-order closure simulations demonstrated that turbulent mixing of momentum was critical in reproducing the frontogenetic (and frontolytic) effects of the transverse secondary circulation."
"7006421134;7004696243;","Propagation of waves exited by localized episodic heating in the tropics and their effect on the middle atmosphere: Comparison between two QBO phases",1997,"10.2151/jmsj1965.75.3_641","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0040600582&doi=10.2151%2fjmsj1965.75.3_641&partnerID=40&md5=5d5edb117222991b610726620d440630","Propagation of waves excited by localized episodic heating in the tropical troposphere and their effect on the middle atmosphere are investigated numerically with a global primitive-equation model in which a realistic radiation scheme for the middle atmosphere is incorporated. Equinoctial initial states with two opposite phases of the quasi-biennial oscillation (QBO) are used for comparison of the propagation and the effect of the waves. Time evolutions of the responses of the equinoctial initial states are not much different from the linear responses of a resting atmosphere obtained by Horinouchi and Yoden (1996). If the duration of the heating is small (less than about a day), Eliassen-Palm (EP) flux in the middle atmosphere is mainly due to gravity waves including Kelvin waves, while if the duration is large (more than about a day), it is mainly due to Kelvin waves, Rossby waves, and Rossby-gravity waves. In the westerly-shear phase of the QBO, westerly acceleration comparable to or a little smaller than that required by the QBO is obtained for wide range of heating parameters, while in the easterly-shear phase, realistic easterly acceleration cannot be obtained if the heating events have large time and horizontal scales (more than about a day and a few thousand kilometers). Gravity waves propagating into the low-and mid-latitude mesosphere are affected by the QBO. The difference in the divergence of the EP flux due to gravity waves may explain the observed quasi-biennial variations in the low-and mid-latitude mesosphere. Excitation of the global normal mode 5-day wave is sensitive to the QBO phase. Since such a QBO modulation has not been observed, this result implies that the source of the 5-day wave in the real atmosphere is not or not only in the tropics, but a considerable portion of the wave is excited outside the tropics."
"6506756436;7102836087;7004953446;","Consequences of the geostrophic momentum approximation on barotropic instability",1997,"10.1175/1520-0469(1997)054<0103:COTGMA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031436429&doi=10.1175%2f1520-0469%281997%29054%3c0103%3aCOTGMA%3e2.0.CO%3b2&partnerID=40&md5=150523261ad7b74a86ec24954778f2b2","A subsynoptic instability with dominant barotropic signature has been found to be a possible mechanism for the development of frontal waves. Linear semigeostrophic calculations of the growth rate of waves developing along a front exhibiting a low-level potential vorticity band are here compared with the results of similar experiments made with a primitive equation model. The growth rates of the subsynoptic instability are significantly underestimated by the semigeostrophic system, a result which is the opposite of what has been found by previous semigeostrophic-primitive equation comparisons in the case of baroclinic instability calculations. Analytical solutions of the Rayleigh model of pure barotropic instability confirm this behavior of the geostrophic momentum approximation (GMA) in the case of barotropic instability. The inaccuracy of the equations with GMA is very sensitive to the basic wind shear amplitude. Such sensitivity seems to be directly linked with the definition of the semigeostrophic vorticity. It should be noted, however, that the frontal wave instability is not filtered by the balanced system but rather it is described in a quantitatively inaccurate way."
"7101867299;","A three‐dimensional generalization of Eliassen's balanced vortex equations derived from Hamilton's principle",1991,"10.1002/qj.49711749902","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026083752&doi=10.1002%2fqj.49711749902&partnerID=40&md5=d65d3f9589cf1486b0b527f2f68ad601","A new set of equations is derived for nearly circular flow in gradient balance. For precisely axisymmetric motion, the system reduces to the well‐known balanced vortex equations of Eliassen. The derivation is based on the assumption that the radial component of velocity is small in comparison to the azimuthal component. By applying this approximation to Hamilton's principle for a continuum of fluid parcels, while preserving the time and particle‐labelling symmetries of the primitive equations, it is ensured that the resulting system possesses conservation laws for energy and potential vorticity. In potential radius coordinates, the Lagrangian equations of motion take the form of the geostrophic and hydrostatic balance conditions. The system is also presented in Eulerian form, and a practical integration scheme, based on a linear elliptic equation for geopotential tendency, is described. Finally, the set is rederived by a conventional scale analysis in order to determine constraints on the diabatic forcings which are required for consistency with the approximation. Copyright © 1991 Royal Meteorological Society"
"24373643500;","The effects of non-linearity on thermal tides in a 3-D numerical model",1989,"10.1016/0021-9169(89)90109-8","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38249022689&doi=10.1016%2f0021-9169%2889%2990109-8&partnerID=40&md5=ea3f0b7cfff6d77475f7587634fe43d0","Absorption of solar radiation is taken as the cause of atmospheric tides, which are simulated by a global, 3-D primitive equation model for the altitude region 0 km-120 km. To investigate non-linear effects, two model versions are used, one with the complete non-linear equation set, the other with the linear equation set. Tide simulations are then performed under the same conditions (background atmosphere and radiation for solstice) with both model versions and directly compared. The diurnal tide can be regarded as a linear phenomenon, whereas the semi-diurnal tide is modified in lower latitudes above 65 km by non-linear effects. Due to the interaction of the tidal components with the background wind, a strong westward zonal flow is generated in the non-linear model above 70 km. © 1989."
"7004657713;7004002518;","Numerical simulation of cold easterly circulations over the Canadian Western Plains using a mesoscale boundary-layer model",1977,"10.1007/BF02186084","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1142282078&doi=10.1007%2fBF02186084&partnerID=40&md5=dd4df3d91fbc77b4b4830226689a3b0f","Arctic outbreaks over the Canadian Western Plains during the late spring period frequently take the form of a cold east-northeasterly flow over a warmer, sloping surface. A mesoscale numerical model is developed in an attempt to simulate such circulations. Following Lavoie (1972) the atmospheric structure of the cold air mass is represented by three layers: a constant flux layer in contact with the earth's surface, a well-mixed planetary boundary layer capped by an inversion, and a deep stratum of overlying stable air. Averaging the set of governing primitive equations through the depth of the mixed layer yields predictive equations for the horizontal wind components, potential temperature, specific humidity, and the height of the inversion. Time-dependent calculations are limited to this layer by parameterizing the interactions between the mixed layer and both the underlying and overlying layers. Precipitation from limited convective clouds, and latent heat within the layer are included in terms of mesoscale variables. A 47.6-km by 47.6-km grid mesh of 1369 points covering the Canadian Prairie Provinces is used to represent the variables. The governing equations are solved numerically with terrain influences, surface roughness, temperature variations, and moisture fluxes allowed to perturb the mixed layer from its initial conditions until resultant mesoscale boundary-layer weather patterns evolve. The mean spring topographic precipitation pattern is successfully reproduced by the simulated late spring upslope flow with limited convective precipitation. Mesoscale planetary boundary-layer weather patterns appear to exert a dominant control over the location and intensity of perturbations in the spring precipitation pattern. The elimination of surface heating significantly reduces the area and intensity of precipitation. A case study based on observed initial conditions showed that the model could reproduce a persistent limited convective precipitation pattern maintained by upslope flow and that a low-level trough exerts a marked influence on the location and the intensity of the precipitation. © 1977 D. Reidel Publishing Company."
"55394412800;55542200200;7801353107;57193921169;7004093651;7003595038;","A mixed finite-element, finite-volume, semi-implicit discretization for atmospheric dynamics: Cartesian geometry",2019,"10.1002/qj.3501","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060290702&doi=10.1002%2fqj.3501&partnerID=40&md5=342d71cd1fff80869d2a16bec741c0b1","To meet the challenges posed by future generations of massively parallel supercomputers, a reformulation of the dynamical core for the Met Office's weather and climate model is presented. This new dynamical core uses explicit finite-volume type discretizations for the transport of scalar fields coupled with an iterated-implicit, mixed finite-element discretization for all other terms. The target model aims to maintain the accuracy, stability and mimetic properties of the existing Met Office model independent of the chosen mesh while improving the conservation properties of the model. This paper details that proposed formulation and, as a first step towards complete testing, demonstrates its performance for a number of test cases in (the context of) a Cartesian domain. The new model is shown to produce similar results to both the existing semi-implicit semi-Lagrangian model used at the Met Office and other models in the literature on a range of bubble tests and orographically forced flows in two and three dimensions. © 2019 Royal Meteorological Society"
"56519415200;57111001300;7101851249;","Resolution Dependence and Rossby Wave Modulation of Atmospheric Rivers in an Aquaplanet Model",2018,"10.1029/2017JD027899","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049862740&doi=10.1029%2f2017JD027899&partnerID=40&md5=b09bac468be3f4b82d172d1df09430d4","Atmospheric rivers (ARs) are examined in a set of aquaplanet simulations using the Model for Prediction Across Scales dynamical core run at multiple horizontal resolutions, namely, 240, 120, and 60 km. As the resolution is increased, there is an increase in the occurrence of long-lasting ARs. At the same time there is also an increase in the local finite-amplitude wave activity (LWA) of upper-tropospheric absolute vorticity, a measure for Rossby wave phase and amplitude that is closely linked with wave breaking. Consistent with the notion that changes in ARs are driven by midlatitude dynamics, a strong relationship is identified between ARs and the equatorward component of LWA. A logistic regression model is used to quantify the probability of AR occurrence based solely on LWA and explains most of the change in AR frequency with resolution. LWA is a diagnostic that may be easily applied to the broadly available output of phase 6 of the Coupled Model Intercomparison project and other model simulations, thus enabling scientists to infer AR and Rossby wave characteristics. AR characteristics, in particular, require higher-resolution moisture and winds at multiple levels that are not always easily available. ©2018. American Geophysical Union. All Rights Reserved."
"57202718351;7004689241;","Shelf flows forced by Deep-Ocean anticyclonic eddies at the shelf break",2018,"10.1175/JPO-D-17-0237.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049102025&doi=10.1175%2fJPO-D-17-0237.1&partnerID=40&md5=8d054e84f2dbd6903bd6e7540ea089f9","Isolated monopolar eddies in the ocean tend to move westward. Those shed by western boundary currents may then interact with the continental margin. This simple picture is complicated by the presence of other flow features, but satellite observations show that many western boundary continental shelves experience cross-shelfbreak exchange flows forced by mesoscale eddies translating near the shelf break. Here we extend our previous study of eddy interaction with a flat shelf to that with a sloping shelf. Using a set of primitive equation numerical simulations, we address the vertical structure of the onshore and offshore flows forced by the eddy, the origin of the exported shelf water, and the extent to which eddy water can penetrate onto the shelf. The simulations reveal an asymmetry in the vertical structure of cross-shelfbreak flows: the offshore flow is generally barotropic, whereas the onshore flow is always baroclinic. The exported shelf water is sourced from downstream of the eddy in the coastal-trapped wave direction and is supplied by a barotropic alongshore jet. This ""supply jet"" has a Rhines-like cross-shore length scale proportional to (eddy velocity scale/shelf topographic beta)1/2 measured from the shelf break. Eddy water is forced onto the shelf and is present up to a distance of one internal Rossby deformation radius, defined using shelf properties, from the shelf break. We rationalize these horizontal and vertical scales, connect them to existing observations, and extend our previous parameterization of eddy-forced offshore shelf-water flux to account for nonzero shelf slopes. © 2018 American Meteorological Society."
"55759186800;7003320046;","A quantitative test case for global-scale dynamical cores based on analytic wave solutions of the shallow-water equations",2016,"10.1002/qj.2861","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981484902&doi=10.1002%2fqj.2861&partnerID=40&md5=d3d03e973dd671109d050c39c84b8762","Recently derived analytic wave solutions of the shallow-water equations (SWEs) on the rotating spherical Earth are employed to construct a test case for hydrostatic dynamical cores of global-scale general circulation models (GCMs). The proposed test case is more relevant to the SWEs than the frequently used Rossby–Haurwitz test case which is based on wave solutions of the non-divergent barotropic vorticity equation and not the SWEs. The applicability of the proposed test case to operational GCMs is demonstrated by using the spectral Eulerian dynamical core of the atmospheric component of NCAR's Community Earth System Model to simulate the analytic solutions. An initial slowly propagating Rossby wave and a fast eastward propagating inertia–gravity wave are both accurately simulated for 100 wave periods. In order to quantify the accuracy of the simulations, two error-measures are suggested which complement the conservation of global energy and, unlike the frequently used L2 error-measure, provide independent assessments of the errors in the phase speeds and the meridional structures of the simulated waves and are therefore more relevant to periodic wave solutions. © 2016 Royal Meteorological Society"
"55500860200;","Understanding anomalous eddy vorticity forcing in North Atlantic oscillation events",2016,"10.1175/JAS-D-15-0253.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982275287&doi=10.1175%2fJAS-D-15-0253.1&partnerID=40&md5=deb9f19fa8bae2ffaa612352897fb395","This study proposes an anomalous eddy vorticity forcing (EVF) decomposing procedure to investigate physical mechanisms responsible for the formation of the anomalous EVF associated with North Atlantic Oscillation (NAO) events. Utilizing the Geophysical Fluid Dynamics Laboratory (GFDL) dynamical core atmospheric model, a series of NAO initial-value short-term experiments are conducted. Applying the EVF decomposing procedure to the results of these experiments, the anomalous nonlinear EVF associated with the NAO events in the model can be decomposed into several fundamental linear eddy-eddy interaction terms and an unimportant nonlinear eddy-eddy interaction term. Compared with the NAO-free situation, synoptic-scale eddies have faster (slower) eastward phase speeds during the positive (negative) NAO events. Through a synoptic-scale eddy-eddy interaction mechanism, the behaviors of anomalous EVF components in the positive (negative) NAO events are well explained by synoptic-scale eddies with faster (slower) eastward phase speeds. Therefore, synoptic-scale eddies with faster (slower) eastward phase speeds are responsible for the development of the anomalous EVF associated with positive (negative) NAO events. Note that at the initial stage of the NAO initial-value experiments, the faster (slower) phase speeds of the synoptic-scale eddies are specified by modifying the initial-value fields and then are amplified/maintained by the strengthening (weakening) zonal wind in the middle and high latitudes associated with the approaching positive (negative)-phase NAO. Therefore, this study indicates that the properties of the synoptic-scale eddies at the initial stage determine the upcoming NAO anomalies. © 2016 American Meteorological Society."
"55797316500;24802214200;55713442200;7406671641;","A study of the impact of parameter optimization on ENSO predictability with an intermediate coupled model",2016,"10.1007/s00382-015-2608-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957430665&doi=10.1007%2fs00382-015-2608-z&partnerID=40&md5=4838671e81ba6fdbdae248033e91e474","Model error is a major obstacle for enhancing the forecast skill of El Niño-Southern Oscillation (ENSO). Among three kinds of model error sources—dynamical core misfitting, physical scheme approximation and model parameter errors, the model parameter errors are treatable by observations. Based on the Zebiak-Cane model, an ensemble coupled data assimilation system is established to study the impact of parameter optimization (PO) on ENSO predictions within a biased twin experiment framework. “Observations” of sea surface temperature anomalies drawn from the “truth” model are assimilated into a biased prediction model in which model parameters are erroneously set from the “truth” values. The degree by which the assimilation and prediction with or without PO recover the “truth” is a measure of the impact of PO. Results show that PO improves ENSO predictability—enhancing the seasonal-interannual forecast skill by about 18 %, extending the valid lead time up to 33 % and ameliorating the spring predictability barrier. Although derived from idealized twin experiments, results here provide some insights when a coupled general circulation model is initialized from the observing system. © 2015, Springer-Verlag Berlin Heidelberg."
"9738329300;15127430500;8284529400;8732198500;55976582900;","Implementation of the Community Earth System Model (CESM) version 1.2.1 as a new base model into version 2.50 of the MESSy framework",2016,"10.5194/gmd-9-125-2016","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84956693582&doi=10.5194%2fgmd-9-125-2016&partnerID=40&md5=4cda469610a515627538511958b4fe88","The Community Earth System Model (CESM1), maintained by the United States National Centre for Atmospheric Research (NCAR) is connected with the Modular Earth Submodel System (MESSy). For the MESSy user community, this offers many new possibilities. The option to use the Community Atmosphere Model (CAM) atmospheric dynamical cores, especially the state-of-the-art spectral element (SE) core, as an alternative to the ECHAM5 spectral transform dynamical core will provide scientific and computational advances for atmospheric chemistry and climate modelling with MESSy. The well-established finite volume core from CESM1(CAM) is also made available. This offers the possibility to compare three different atmospheric dynamical cores within MESSy. Additionally, the CESM1 land, river, sea ice, glaciers and ocean component models can be used in CESM1/MESSy simulations, allowing the use of MESSy as a comprehensive Earth system model (ESM). For CESM1/MESSy set-ups, the MESSy process and diagnostic submodels for atmospheric physics and chemistry are used together with one of the CESM1(CAM) dynamical cores; the generic (infrastructure) submodels support the atmospheric model component. The other CESM1 component models, as well as the coupling between them, use the original CESM1 infrastructure code and libraries; moreover, in future developments these can also be replaced by the MESSy framework. Here, we describe the structure and capabilities of CESM1/MESSy, document the code changes in CESM1 and MESSy, and introduce several simulations as example applications of the system. The Supplements provide further comparisons with the ECHAM5/MESSy atmospheric chemistry (EMAC) model and document the technical aspects of the connection in detail. © 2016 Author(s)."
"7403744370;6506756436;15765007300;57193921169;","Bridging the (knowledge) gap between physics and dynamics",2016,"10.1175/BAMS-D-15-00103.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959165121&doi=10.1175%2fBAMS-D-15-00103.1&partnerID=40&md5=6f950c47de8007ce2040e7c6b7708a0b","The first Physics Dynamics Coupling (PDC14) workshop was held in December 2014 in Mexico. When adjusting the physics?dynamics coupling in relation to the time-stepping scheme in the Integrated Forecasting System (IFS) at the European Centre for Medium-Range Weather Forecasts (ECMWF), Beljaars and colleagues show clear improvements in the root-mean-square (RMS) errors of the 10-m wind speeds. Beljaars and colleagues and Wan and colleagues have shown the usefulness of complex general circulation models (GCM) tests. However, in general there is a lack of understanding of whether, and if so how, the theoretical results relate to the full models. For this reason several groups are currently working on bridging this gap by developing test cases that have nearly the complexity of full model runs but are sufficiently transparent and portable to aid experimentation and model comparison. focus is on the inclusion of simplified moist processes because they reveal a fundamental coupling process between the dynamical core and physics."
"55998591400;8696068200;55394412800;","Energy-conserving finite-difference schemes for quasi-hydrostatic equations",2015,"10.1002/qj.2590","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84952298841&doi=10.1002%2fqj.2590&partnerID=40&md5=1809d4d7daacaaec967e21ae0143651d","The pressure-based hydrostatic primitive equations model LMD-Z is extended to solve the quasi-hydrostatic deep-atmosphere as well as the non-traditional shallow-atmosphere equations (with a complete Coriolis force representation). The continuous equations are first derived in their curl form using Eulerian horizontal and non-Eulerian vertical coordinates. The equations are then interpreted as a Hamiltonian system, as they are expressed in terms of functional derivatives of the Hamiltonian. Using a finite-difference scheme on a longitude/latitude grid and based either on a Lagrangian or mass-based vertical coordinate, the discrete scheme is obtained by imitating the Hamiltonian formulation at the discrete level. It is shown how this form leads straightforwardly to the conservation of discrete total energy. The relation between the discrete equations and the discrete antisymmetry property of the Poisson bracket is discussed. The computing infrastructure of the dynamical core is kept essentially unchanged but the modification of the hydrostatic balance requires a mass-based vertical coordinate. Also, absolute angular momentum is used as a prognostic variable instead of relative velocity, which allows time-dependent metric terms and the non-traditional Coriolis force to be absorbed into it. The prototype implementation is applied to idealized circulations of an Earth-like small planet and validates the stability and accuracy of the new dynamical core. © 2015 Royal Meteorological Society."
"6507253177;7005808242;26430995400;","Kinetic energy-conserving hyperdiffusion can improve low resolution atmospheric models",2015,"10.1002/2015MS000480","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939618679&doi=10.1002%2f2015MS000480&partnerID=40&md5=6992cf318b60d2fe4b3d069fe35caff8","Motivated by findings that energetically consistent subgrid dissipation schemes can improve eddy-permitting ocean simulations, this work investigates the impact of the subgrid dissipation scheme on low-resolution atmospheric dynamical cores. A kinetic energy-conserving dissipation scheme is implemented in the model adding a negative viscosity term that injects back into the eddy field the kinetic energy dissipated by horizontal hyperdiffusion. The kinetic energy-conserving scheme enhances numerical convergence when horizontal resolution is changed with fixed vertical resolution and gives superior low-resolution results. Improvements are most obvious for eddy kinetic energy but also found in other fields, particularly with strong or little scale-selective horizontal hyperdiffusion. One advantage of the kinetic energy-conserving scheme is that it reduces the sensitivity of the model to changes in the subgrid dissipation rate, providing more robust results. © 2015. The Authors."
"15044268700;25637373000;6507492100;7004687638;35984036000;6602075440;7005814217;7102450474;7102696626;56725357800;","A spectral transform dynamical core option within the Community Atmosphere Model (CAM4)",2015,"10.1002/2014MS000329","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84937202641&doi=10.1002%2f2014MS000329&partnerID=40&md5=4767cacb37c02808173cc7d572420618","An ensemble of simulations covering the present day observational period using forced sea surface temperatures and prescribed sea-ice extent is configured with an 85 truncation resolution spectral transform dynamical core (T85) within the Community Atmosphere Model (CAM), version 4 and is evaluated relative to observed and model derived data sets and the one degree finite volume (FV) dynamical core. The spectral option provides a well-known base within the climate model community to assess climate behavior and statistics, and its relative computational efficiency for smaller computing platforms allows it to be extended to perform high-resolution climate length simulations. Overall, the quality of the T85 ensemble is similar to FV. Analyzing specific features of the T85 simulations show notable improvements to the representation of wintertime Arctic sea level pressure and summer precipitation over the Western Indian subcontinent. The mean and spatial patterns of the land surface temperature trends over the AMIP period are generally well simulated with the T85 ensemble relative to observations, however the model is not able to capture the extent nor magnitude of changes in temperature extremes over the boreal summer, where the changes are most dramatic. Biases in the wintertime Arctic surface temperature and annual mean surface stress fields persist with T85 as with the CAM3 version of T85, as compared to FV. An experiment to identify the source of differences between dycores has revealed that the longwave cloud forcing is sensitive to the choice of dycore, which has implications for tuning strategies of the physics parameter settings. Key Points Longwave cloud forcing in T85 CAM4 is sensitive to the choice of dynamical core Improved precipitation over India does not translate to improved surface stress The increase in temperature extremes during NH summer is underestimated © 2014. The Authors."
"7403535713;44561454300;36089189400;","Sensitivity and variability redux in hot-Jupiter flow simulations",2015,"10.1093/mnras/stv1947","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949257349&doi=10.1093%2fmnras%2fstv1947&partnerID=40&md5=5b30e410bee9336c8d2aeeb8fa1557ef","We revisit the issues of sensitivity to initial flow and intrinsic variability in hot-Jupiter atmospheric flow simulations, issues originally investigated by Cho et al. and Thrastarson & Cho. The flow in the lower region (~1 to 20 MPa) 'dragged' to immobility and uniform temperature on a very short time-scale, as in Liu & Showman, leads to effectively a complete cessation of variability as well as sensitivity in three-dimensional (3D) simulations with traditional primitive equations. Such momentum (Rayleigh) and thermal (Newtonian) drags are, however, ad hoc for 3D giant planet simulations. For 3D hot-Jupiter simulations, which typically already employ a strong Newtonian drag in the upper region, sensitivity is not quenched if only the Newtonian drag is applied in the lower region, without the strong Rayleigh drag: in general, both sensitivity and variability persist if the two drags are not applied concurrently in the lower region. However, even when the drags are applied concurrently, vertically propagating planetary waves give rise to significant variability in the ~0.05-0.5 MPa region, if the vertical resolution of the lower region is increased (e.g. here with 1000 layers for the entire domain). New observations on the effects of the physical setup and model convergence in 'deep' atmosphere simulations are also presented. © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society."
"56716277600;36103465000;7102340415;","Realizing surface-driven flows in the primitive equations",2015,"10.1175/JPO-D-14-0097.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944063152&doi=10.1175%2fJPO-D-14-0097.1&partnerID=40&md5=0443b62b90d619634cb90a6a5dde030d","The surface quasigeostrophic (SQG) model describes flows with surface buoyancy perturbations with no interior quasigeostrophic potential vorticity at small Rossby number Ro and O(1) Burger number, where quasigeostrophic dynamics are expected to hold. Numerical simulations of SQG dynamics have shown that vortices are frequently generated at small scales, which may have O(1) Rossby numbers and therefore may be beyond the limits of SQG. This paper examines the dynamics of an initially geostrophically balanced elliptical surface buoyancy perturbation in both the SQG model and the nonhydrostatic Boussinesq primitive equations (PE). In the case of very small Rossby number, it is confirmed that both models agree, as expected. For larger Ro, non-SQG effects emerge and as a result the solution of the PE deviates significantly from that of SQG. In particular, an increase in the Rossby number has the following effects: (i) the buoyancy filaments at the surface are stabilized in that they generate fewer secondary vortices; (ii) the core of the vortex experiences inertial instability, which results in a uniform buoyancy profile in its interior; (iii) the divergent part of the energy spectrum increases in magnitude; (iv) the PE model has significantly more gravity waves that are radiated from the vortex; (v) the magnitude of the vertical velocity increases; and (vi) in the mature stages of evolution, there are gravitational instabilities that develop because of the complicated dynamics inside the vortex. It is demonstrated that significant non-SQG effects are evident when the large-scale Rossby number of the initial flow is about 0.05 and the local Rossby number is O(1). © 2015 American Meteorological Society."
"57154893800;7410249955;55744344700;","Numerical evidence of turbulence generated by nonbreaking surface waves",2015,"10.1175/JPO-D-14-0121.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920886585&doi=10.1175%2fJPO-D-14-0121.1&partnerID=40&md5=eef0315115b5387f50b2de8ebf3c2743","Numerical simulation of monochromatic surface waves propagating over a turbulent field is conducted to reveal the mechanism of turbulence production by nonbreaking waves. The numerical model solves the primitive equations subject to the fully nonlinear boundary conditions on the exact water surface. The result predicts growth rates of turbulent kinetic energy consistent with previous measurements and modeling. It also validates the observed horizontal anisotropy of the near-surface turbulence that the spanwise turbulent intensity exceeds the streamwise component. Such a flow structure is found to be attributed to the formation of streamwise vortices near the water surface, which also induces elongated surface streaks. The averaged spacing between the streaks and the depth of the vortical cells approximates that of Langmuir turbulence. The strength of the vortices arising from the wave-turbulence interaction, however, is one order of magnitude less than that of Langmuir cells, which arises from the interaction between the surface waves and the turbulent shear flow. In contrast to Langmuir turbulence, production from the Stokes shear does not dominate the energetics budget in wave-induced turbulence. The dominant production is the advection of turbulence by the velocity straining of waves. © 2015 American Meteorological Society."
"57207473157;25226875800;7401436524;","Simulations of stratus clouds over Eastern China in CAM5: Sources of errors",2015,"10.1175/JCLI-D-14-00350.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84920268378&doi=10.1175%2fJCLI-D-14-00350.1&partnerID=40&md5=3f75794e2350324902686475af2a48f5","A previous study by Zhang et al. suggested two biases of the high-resolution configured Community Atmosphere Model, version 5 (CAM5), in simulating stratus clouds over eastern China, including an underestimation of stratus occurrence frequency and a spurious low stratus amount when present (AWP) value center over the Sichuan basin. In this study, the causes for these two problems are further explored. The underestimate of stratus occurrence frequency in the model is attributed to the bias in large-scale ambient environmental fields. This is confirmed by investigating the differences between two climate counterparts. Results suggest that when the environmental fields in the climate ensemble become more realistic, the simulations of stratus cloud radiative forcing and cloud fraction are enhanced, mainly caused by a corresponding increase in the stratus occurrence frequency. The specific sources of the cloud changes between these two ambient climates are then investigated. The presence of a low stratus AWP value center is found to be sensitive to the choice of dynamical core. This is confirmed by comparing the simulations from two dynamical core counterparts: a default finite-volume core and an alternative Eulerian spectral transform core. Experiments with these two cores suggest that the spectral CAM5 is able to alleviate this problem. Correspondingly, the subsiding motions when stratus clouds occur in the default core are largely suppressed in the spectral core. As a result, the spectral CAM5 has more midtopped nimbostratus cloud fraction than the default configuration over the Sichuan basin, especially in the lower levels of the cloud profiles. © 2015 American Meteorological Society."
"56003637600;55491435100;8684892000;56962915800;57218273453;55656493400;","Improving parallel performance of a finite-difference AGCM on modern high-performance computers",2014,"10.1175/JTECH-D-13-00067.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84907996373&doi=10.1175%2fJTECH-D-13-00067.1&partnerID=40&md5=97407a5eab71248c778d4483946f903d","The rapid development of science and technology has enabled finer and finer resolutions in atmospheric general circulation models (AGCMs). Parallelization becomes progressively more critical as the resolution of AGCMs increases. This paper presents a new parallel version of the finite-difference Gridpoint Atmospheric Model of the Institute of Atmospheric Physics (IAP)-State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG; GAMIL) with various parallel optimization strategies, including two-dimensional hybrid parallel decomposition; hybrid parallel programming; parallel communications for coupling the physical packages, land surface, and dynamical core; and a cascading solution to the tridiagonal equations used in the dynamical core. The new parallel version under two different horizontal resolutions (18 and 0.258) is evaluated. The new parallel version enables GAMIL to achieve higher parallel efficiency and utilize a greater number of CPU cores. GAMIL18 achieves 37.8% parallel efficiency using 960 CPU cores, while GAMIL0.258 achieves 57.5% parallel efficiency. © 2014 American Meteorological Society."
"12796149400;7404358451;","A multiscale model for the planetary and synoptic motions in the atmosphere",2013,"10.1175/JAS-D-12-0272.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884968611&doi=10.1175%2fJAS-D-12-0272.1&partnerID=40&md5=f692ac912e4c08509587e8c378513007","A reduced asymptotic model valid for the planetary and synoptic scales in the atmosphere is presented. The model is derived by applying a systematic multiple-scales asymptotic method to the full compressible-flow equations in spherical geometry. The synoptic-scale dynamics in the model is governed by modified quasigeostrophic equations, which take into account planetary-scale variations of the background stratification and of the Coriolis parameter. The planetary-scale background is described by the planetary geostrophic equations and a new closure condition in the form of a two-scale evolution equation for the barotropic component of the background flow. This closure equation provides a model revealing an interaction mechanism from the synoptic scale to the planetary scale. To obtain a quantitative assessment of the validity of the asymptotics, the balances on the planetary and synoptic scales are studied by utilizing a primitive equations model. For that purpose, spatial and temporal variations of different terms in the vorticity equation are analyzed. It is found that, for planetary-scale modes, the horizontal fluxes of relative and planetary vorticity are nearly divergence free. It is shown that the results are consistent with the asymptotic model. © 2013 American Meteorological Society."
"52263850600;15765007300;36154754400;7005087624;","Downscale cascades in tracer transport test cases: An intercomparison of the dynamical cores in the Community Atmosphere Model CAM5",2012,"10.5194/gmd-5-1517-2012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84881130068&doi=10.5194%2fgmd-5-1517-2012&partnerID=40&md5=acf12f5483fa3190b1238a8f2d7999f1","The accurate modeling of cascades to unresolved scales is an important part of the tracer transport component of dynamical cores of weather and climate models. This paper aims to investigate the ability of the advection schemes in the National Center for Atmospheric Research's Community Atmosphere Model version 5 (CAM5) to model this cascade. In order to quantify the effects of the different advection schemes in CAM5, four two-dimensional tracer transport test cases are presented. Three of the tests stretch the tracer below the scale of coarse resolution grids to ensure the downscale cascade of tracer variance. These results are compared with a high resolution reference solution, which is simulated on a resolution fine enough to resolve the tracer during the test. The fourth test has two separate flow cells, and is designed so that any tracer in the western hemisphere should not pass into the eastern hemisphere. This is to test whether the diffusion in transport schemes, often in the form of explicit hyper-diffusion terms or implicit through monotonic limiters, contains unphysical mixing. An intercomparison of three of the dynamical cores of the National Center for Atmospheric Research's Community Atmosphere Model version 5 is performed. The results show that the finite-volume (CAM-FV) and spectral element (CAM-SE) dynamical cores model the downscale cascade of tracer variance better than the semi-Lagrangian transport scheme of the Eulerian spectral transform core (CAM-EUL). Each scheme tested produces unphysical mass in the eastern hemisphere of the separate cells test. © Author(s) 2012."
"6505569858;6508060859;","Analysis of quantitative precipitation forecasts using the Dynamic State Index",2009,"10.1016/j.atmosres.2009.08.013","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70449646234&doi=10.1016%2fj.atmosres.2009.08.013&partnerID=40&md5=3ea2c648107add85a0ccc88258bfa66c","The German Weather Service (DWD) has two non-hydrostatic operational weather prediction models with different spatial resolution and precipitation parametrisations. The coarser COSMO-EU model has a spatial resolution of 7 km, whereas the higher-resolution COSMO-DE model has a gridspace of 2.8 km and explicitly resolves deep convection. To improve the numerical weather prediction (NWP) models it is necessary to understand precipitation processes. A central goal is the statistical evaluation of precipitation forecasts with dynamic parameters. Here, the Dynamic State Index (DSI) is used as a dynamic threshold parameter. The DSI theoretically describes the change of atmospheric flow fields as deviations from a stationary adiabatic solution of the primitive equations (Névir, 2004). For seasonal area means the DSI shows a remarkably high correlation with the precipitation forecasts provided by the COSMO-DE model. This is especially the case for the summer of 2007. The same analysis has been performed with the COSMO-EU forecast data and the results were compared with those from the COSMO-DE model. Moreover, an independent precipitation analysis, with a resolution corresponding to 7 km and 2.8 km, has been compared with respect to modelled precipitation and the DSI. In addition, correlations between the DSI and modelled as well as observed precipitation as a function of the forecast time for the different grid resolutions are also presented. The results show, that after 12 h, the correlation of the persistence forecast with the DSI reaches two thirds of the initial value. Thus, the DSI offers itself as a new dynamic forecast tool for precipitation events. © 2009 Elsevier B.V. All rights reserved."
"26430935600;14023984800;7006354215;","Effects of surface forcing on the seasonal cycle of the eastern equatorial Pacific",2009,"10.1357/002224009792006179","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955705726&doi=10.1357%2f002224009792006179&partnerID=40&md5=f0de560e21f919d55c3ba934092a26ec","The roles of zonal and meridional wind stress and of surface heat flux in the seasonal cycle of sea surface temperature (SST) are examined with a primitive equation (PE) model of the tropical Pacific Ocean. While a variety of previous numerical and observational studies have examined the seasonal cycle of SST in the eastern tropical Pacific, it is noteworthy that different mechanisms have been invoked as primary in each case and different conclusions have been reached regarding the relative importance of the various components of surface forcing. Here, we perform a series of numerical experiments in which different components of the surface forcing are eliminated and the resulting upper ocean variability is compared with that of the climatological experiment. The model used for these experiments reproduces a realistic climatological seasonal cycle, in which SST emerges as an independent quantity. We find that the different cases all produce qualitatively reasonable seasonal cycles of SST, though only the most complete model is also able to reproduce the seasonal cycle of near surface currents, tropical instability waves (TIWs), and net surface heat fluxes consistent with historical observations. These results indicate that simply reproducing a qualitatively accurate seasonal cycle of SST does not necessarily allow meaningful conclusions to be made about the relative importance of the different components of surface forcing. The results described here also suggest that a model simulation must at least reproduce all the documented near surface kinematic features of the equatorial Pacific cold tongue region reasonably well, before accurate inferences can be made from model experiments. This provides useful guidelines to current efforts to develop and evaluate more complex fully coupled air-sea models and shows that results for simple or intermediate ocean models that do not have this level of fidelity to the observations will be difficult to interpret."
"57219263838;7004611313;7202613485;","Ensemble-based estimates of the predictability of wind-driven coastal ocean flow over topography",2009,"10.1175/2009MWR2631.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350338751&doi=10.1175%2f2009MWR2631.1&partnerID=40&md5=01e432d5aed5a3da6adc03deca0a8d7b","The predictability of coastal ocean circulation over the central Oregon shelf, a region of strong wind-driven currents and variable topography, is studied using ensembles of 50-day primitive equation ocean model simulations with realistic topography, simplified lateral boundary conditions, and forcing from both idealized and observed wind time series representative of the summer upwelling season. The main focus is on the balance, relevant to practical predictability, between deterministic response to known or well-predicted forcing, uncertainty in initial conditions, and sensitivity to instabilities and topographic interactions. Large ensemble and single-simulation variances are found downstream of topographic features, associated with transitions between along-isobath and cross-isobath flow, which are in turn related both to the time-integrated amplitude of upwelling-favorable wind forcing and to the formation of small-scale eddies. Simulated predictability experiments are conducted and model forecasts are verified by standard statistics including anomaly correlation coefficient, and root-mean-square error. A new variant of relative entropy, the forecast relative entropy, is introduced to quantify the predictive information content in the forecast ensemble, relative to the initial ensemble. The results suggest that, even under conditions of relatively weak wind forcing, the deterministic response is stronger than instability growth over the 3-7-day forecast intervals considered here. Consequently, important elements of the coastal circulation should be accessible to predictive, dynamical forecasts on the nominal 7-day predictability time scale of the atmospheric forcing, provided that sufficiently accurate initializations are available. These results on predictability are consistent with inferences drawn from recent modeling studies of coastal ocean circulation along the central Oregon shelf, and should have general validity for other, similar regions. © 2009 American Meteorological Society."
"16246205000;57203012011;55738957800;7003652577;","Understanding the effects of convective momentum transport on climate simulations: The role of convective heating",2008,"10.1175/2008JCLI2187.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-56349094775&doi=10.1175%2f2008JCLI2187.1&partnerID=40&md5=4eef1874b3b325178846441254e2e6cb","A simplified general circulation model (GCM), consisting of a complete dynamical core, simple specified physics, and convective momentum transport (CMT) forcing, is used to understand the effects of CMT on climate simulations with a focus on the role of convective heating in the response of circulation to the CMT forcing. It is found that the convective heating dominates the meridional circulation response and dynamical processes dominate the zonal wind response to the CMT forcing in the tropics; the simplified model reproduces some of the key features of CMT-induced circulation changes observed in the full GCM in the tropics. These results suggest that the CMT-induced zonal and meridional circulation changes in the tropics in the full GCM are dominated by dynamical processes and the convective heating, respectively. Inclusion of the CMT in the model induces a marked change in convective heating, which negatively correlates with the change in vertical velocity, indicating the existence of CMT-induced convective heating-circulation feedback. The sensitivity experiment with the removal of mean convective heating feedback demonstrates that the convective heating affects the response of the meridional circulation to the CMT forcing through the CMT-induced convective heating-circulation feedback. © 2008 American Meteorological Society."
"7004069241;7404187480;","Unsteady exact solutions of the flow equations for three-dimensional spherical atmospheres",2008,"10.1002/qj.300","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57349143528&doi=10.1002%2fqj.300&partnerID=40&md5=4b24fab91dd59eb294714a1665462249","Time-dependent, closed-form solutions of the 3D Euler equations describing motion relative to a uniformly rotating coordinate frame are derived. The spherical geopotential approximation is applied but not the shallow-atmosphere and hydrostatic approximations. The solutions correspond to cyclostrophically and hydrostatically balanced vortices that are steady in inertial space and whose symmetry axes do not coincide with the rotation axis of the coordinate frame. The inertial-frame flow velocities are readily transformed to a precisely spherical rotating coordinate system in which the 3D Euler equations contain centrifugal as well as Coriolis terms. In this form the solutions may be used to test numerical models formulated in spherical coordinates under the spherical geopotential approximation, so long as the centrifugal terms are explicitly included as forcing terms. The development is repeated for the hydrostatic and non-hydrostatic primitive equations (with the shallow-atmosphere approximation) and for the shallow-water equations. In the latter case, the required explicit centrifugal force may be provided by a zonally symmetric addition to the free surface height, with an identically equal orographic elevation to ensure conservation of mass. The solutions are then identical to the unsteady shallow-water solutions of Läuter et al. that inspired this study. © Crown Copyright 2008. Reproduced with the permission of the Controller of HMSO."
"7103321545;","Similarities and differences among the south Indian Ocean convergence zone, North American convergence zone, and other subtropical convergence zones simulated using an AGCM",2008,"10.2151/jmsj.86.141","https://www.scopus.com/inward/record.uri?eid=2-s2.0-43749103584&doi=10.2151%2fjmsj.86.141&partnerID=40&md5=b5157c2d9e46739207629932e4af1a6d","I examined features of the South Indian Ocean convergence zone (SICZ) and the North American convergence zone (NACZ) simulated using an atmospheric general circulation model (AGCM; T106L56: a spectral primitive-equation model with 56 σ levels and triangular spectral truncation at wave-number 106). The 24-year model integration from 1979 to 2002 was constrained by observed sea-surface temperature and sea-ice distribution. I selected a typical case for each zone (SICZ and NACZ) from the 1985-1996 simulation. The AGCM properly simulates African and Indian Ocean monsoon circulation and precipitation. The precipitation zone of the SICZ extends southeastward from the southeastern part of Africa to the southwestern rim of the Mascarene high during Southern Hemisphere summer. North American summer monsoon circulation and precipitation were also correctly reproduced. The precipitation zone of the NACZ extends northeastward along the southeastern coast of North America to the northwestern rim of the Bermuda high during the North American summer monsoon season. I compared the features of the simulated SICZ and NACZ with features of the South Atlantic convergence zone (SACZ) and the Baiu frontal zone (BFZ) simulated using the same AGCM. The SACZ, SICZ, NACZ, and BFZ were characterized as subtropical convergence zones (STCZs) and are commonly sustained along their respective subtropical anticyclones that form over the ocean east of continents. However, their geographical environments differ significantly. Whereas the respective cool oceans at the poleward sides of the SACZ and SICZ provide significant baroclinicity for the SACZ and SICZ, the respective hot continents to the poleward sides of the BFZ and NACZ create weak baroclinicity for the BFZ and NACZ. © 2008, Meteorological Society of Japan."
"6506900387;7101739466;","Local mass conservation and velocity splitting in PV-based balanced models. Part II: Numerical results",2007,"10.1175/JAS3934.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347406385&doi=10.1175%2fJAS3934.1&partnerID=40&md5=8082e69393b7b76fb61b27b4ed3b3014","The effects of enforcing local mass conservation on the accuracy of non-Hamiltonian potential-vorticity-based balanced models (PBMs) are examined numerically for a set of chaotic shallow-water f-plane vortical flows in a doubly periodic square domain. The flows are spawned by an unstable jet and all have domain-maximum Froude and Rossby numbers Fr ∼0.5 and Ro ∼1, far from the usual asymptotic limits Ro → 0, Fr → 0, with Fr defined in the standard way as flow speed over gravity wave speed. The PBMs considered are the plain and hyperbalance PBMs defined in Part I. More precisely, they are the plain-δδ, plain-γγ, and plain-δγ PBMs and the corresponding hyperbalance PBMs, of various orders, where ""order"" is related to the number of time derivatives of the divergence equation used in defining balance and potential-vorticity inversion. For brevity the corresponding hyperbalance PBMs are called the hyper-δδ, hyper-γγ, and hyper-δγ, PBMs, respectively. As proved in Part I, except for the leading-order plain-γγ each plain PBM violates local mass conservation. Each hyperbalance PBM results from enforcing local mass conservation on the corresponding plain PBM. The process of thus deriving a hyperbalance PBM from a plain PBM is referred to for brevity as plain-to-hyper conversion. The question is whether such conversion degrades the accuracy, as conjectured by McIntyre and Norton. Cumulative accuracy is tested by running each PBM alongside a suitably initialized primitive equation (PE) model for up to 30 days, corresponding to many vortex rotations. The accuracy is sensitively measured by the smallness of the ratio ε = ∥QPBM - QPE∥ 2/∥QPE∥2, where QPBM and QPE denote the potential vorticity fields of the PBM and the PEs, respectively, and ∥ ∥2 is the L2 norm. At 30 days the most accurate PBMs have ε ≈ 10-2 with PV fields hardly distinguishable visually from those of the PEs, even down to tiny details. Most accurate is defined by minimizing ε over all orders and truncation types δδ, γγ and δγ. Contrary to McIntyre and Norton's conjecture, the minimal ε values did not differ systematically or significantly between plain and hyperbalance PBMs. The smallness of ε suggests that the slow manifolds defined by the balance relations of the most accurate PBMs, botb plain and hyperbalance, are astonishingly close to being invariant manifolds of the PEs, at least throughout those parts of phase space for which Ro ≤ 1 and Fr ≤ 0.5. As another way of quantifying the departures from such invariance, that is, of quantifying the fuzziness of the PEs' slow quasimanifold, initialization experiments starting at days 1, 2,...10 were carried out in which attention was focused on the amplitudes of inertia-gravity waves representing the imbalance arising in 1-day PE runs. With balance defined by the most accurate PBMs, and imbalance by departures therefrom, the results of the initialization experiments suggest a negative correlation between early imbalance and late cumulative error ε In such near-optimal conditions the imbalance seems to be acting like weak background noise producing an effect analogous to so-called stochastic resonance, in that a slight increase in noise level brings PE behavior closer to the balanced behavior defined by the most accurate PBMs when measured cumulatively over 30 days. © 2007 American Meteorological Society."
"7401699378;56098717400;","An investigation into axisymmetrization of a vortex embedded in horizontal shearing currents",2007,"10.1029/2006JD007087","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249659380&doi=10.1029%2f2006JD007087&partnerID=40&md5=5dd92974b678e08859cc5ea2c5475ea4","The problem of tropical cyclogenesis in a triple-scale coexisting system which includes a subtropical high ridge, a preexisting cyclonic circulation with the initial maximum tangential wind V<inf>bmax</inf> of 5 m s-1, and single-, double-, or four-cluster anomalies is examined in this paper, using a shallow water primitive equation (SWPE) model. This work validates the recent results concerning the upscale cascade mechanism suggested for tropical cyclogenesis in the double-scale coexisting system containing the basic state vortex and anomalies, and it is shown that, for the double-cluster anomaly, the mean azimuthal maximum tangential wind of the final vortex is increased and the radius of the maximum tangential wind (RMW) is contracted in the case of 1.388 ≥ K<inf>ut</inf> ≥ 0.0 in which K<inf>ut</inf> = u<inf>smax</inf> /V<inf>bmax</inf> with u<inf>smax</inf> being the maximum of the easterlies south of the initial subtropical ridge, which demonstrates an amplification of the vortex within this range of parameter. For the single-cluster anomaly of large amplitude the anomaly will become a master vortex, and for the four-cluster one the spin-up of the initial basic state vortex will be decreased. Compared with the case of still environmental currents, introducing the subtropical ridge will have the following impact on axisymmetrization in horizontal shearing currents: (1) The interaction of a single-cluster anomaly with the basic state vortex will occur in the environmental currents with cyclonic vorticity when the anomaly is located initially in the SW/SE quadrant of the basic state vortex; the interaction between the anomaly and the basic state vortex makes the spin-up double that in the case of still environmental currents. (2) Although axisymmetrization of vortex configuration may occur, it is mainly limited to the inner region of the vortex with a distinct new nonaxisymmetry in its outer region, and there exist a series of cells of smaller scales in the northeastern quadrant of the outer region. (3) The total kinetic energy for the inner region of the vortex in the mean increases but fluctuates with time, unlike the still environmental currents case in which it increases monotonicall. Copyright 2007 by the American Geophysical Union."
"7401699378;56098717400;","Diversity of microenvironments and the complexity of vortex motion",2006,"10.1029/2006GL027765","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548045052&doi=10.1029%2f2006GL027765&partnerID=40&md5=63c67665a3577a0ef4308782b7ef25cb","The complexity of major vortex motion in a system where four scales are coexisting (a subtropical high ridge, the major vortex, meso- and small-scale vortices) is examined numerically using a barotropic primitive equation model. The microenvironment of a major vortex consists of a group of small-scale vortices in which varying values for the total number N of initial small-scale vortices (N = 2, 3, 4, and 5, respectively) creates a diverse range of microenvironments. Three kinds of major vortex motion are observed: (i) the initial major vortex decays away with no new major vortex formation; (ii) a weak new major vortex forms while the major vortex decays; and (iii) a new major vortex occurs, via self-organization, with its intensity and scale similar to those in the initial stages of the original major vortex, and this vortex continues to shift westwards after the old major vortex decays. Copyright 2006 by the American Geophysical Union."
"55469187200;","Equatorial superrotation and barotropic instability: Static stability variants",2006,"10.1175/JAS3711.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33744481541&doi=10.1175%2fJAS3711.1&partnerID=40&md5=12e1f6b583384cabbaaff9b61aca2ce4","Altering the tropospheric static stability changes the nature of the equatorial superrotation associated with unstable, low-latitude, westerly jets, according to calculations with a dry, global, multilevel, spectral, primitive equation model subject to a simple Newtonian heating function. For a low static stability, the superrotation fluxes with the simplest structure occur when the stratospheric extent and horizontal diffusion are minimal. Barotropic instability occurs on the jet's equatorward flank and baroclinic instability occurs on the jet's poleward flank. Systems with a high static stability inhibit the baroctinic instability and thereby reveal more clearly that the barotropic instability is the primary process driving the equatorial superrotation. Such systems produce a flatter equatorial jet and also take much longer to equilibrate than the standard atmospheric circulation."
"7003821149;","Islands in zonal flow",2003,"10.1175/1520-0485(2003)033<2689:IIZF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1642456531&doi=10.1175%2f1520-0485%282003%29033%3c2689%3aIIZF%3e2.0.CO%3b2&partnerID=40&md5=07796238b7eac5b9f59ee0f070f166bc","The impact of a meridional gradient in sea surface temperature (warm toward the equator, cold toward the pole) on the circulation around an island is investigated. The upper-ocean eastward geostrophic flow that balances such a meridional gradient is blocked where the isotherms intersect boundaries. In the case in which the boundaries represent either the eastern or western side of a planetary-scale island, circulation integrals around the island show that some of this eastward transport will flow around both the equatorward and poleward tips of the island. There is also a net downwelling along the western side of the island and a net upwelling along the eastern side of the island. An analytic model of the eastern and western boundary currents is used together with a circulation integral to estimate the fraction of the eastward transport that flows around the equatorward and poleward tips of the island and the net upwelling/downwelling on either side of the island. Calculations with a primitive equation numerical model are in close agreement with the theory. A simple closed-form analytic solution for the transport around the island tips is derived in the limit of strong buoyancy forcing. It is found that, over a wide range of parameter space, a significant fraction of the eastward transport in the upper ocean circulates around the tips of the island from the western basin into the eastern basin."
"18837743400;7103294731;","Planetary-wave-induced transport in the stratosphere",2003,"10.1175/1520-0469(2003)060<1456:PTITS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038757548&doi=10.1175%2f1520-0469%282003%29060%3c1456%3aPTITS%3e2.0.CO%3b2&partnerID=40&md5=77e22c8fe259439fd6c7f6f3bd49eb9f","In the stratosphere, chemical tracers are drawn sytematically from the equator to the pole. This observed Brewer-Dobson circulation is driven by wave drag, which in the stratosphere arises mainly from the breaking and dissipation of planetary-scale Rossby waves. While the overall sense of the circulation follows from fundamental physical principles, a quantitative theoretical understanding of the connection between wave drag and Lagrangian transport is limited to linear, small-amplitude waves. However, planetary waves in the stratosphere generally grow to a large amplitude and break in a strongly nonlinear fashion. This paper addresses the connection between stratospheric wave drag and Lagrangian transport in the presence of strong nonlinearity, using a mechanistic three-dimensional primitive equations model together with offline particle advection. Attention is deliberately focused on a weak forcing regime, such that sudden warmings do not occur and a quasi-steady state is reached, in order to examine this question in the cleanest possible context. Wave drag is directly linked to the transformed Eulerian mean (TEM) circulation, which is often used as a surrogate for mean Lagrangian motion. The results show that the correspondence between the TEM and mean Lagrangian velocities is quantitatively excellent in regions of linear, nonbreaking waves (i.e., outside the surf zone), where streamlines are not closed. Within the surf zone, where streamlines are closed and meridional particle displacements are large, the agreement between the vertical components of the two velocity fields is still remarkably good, especially wherever particle paths are coherent so that diabatic dispersion is minimized. However, in this region the meridional mean Lagrangian velocity bears little relation to the meridional TEM velocity, and reflects more the kinematics of mixing within and across the edges of the surf zone. The results from the mechanistic model are compared with those from the Canadian Middle Atmosphere Model to test the robustness of the conclusions."
"47561064400;7401699378;","A preliminary study of the dynamics of eastward shifting cyclonic vortices",2003,"10.1007/bf02690790","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0142187301&doi=10.1007%2fbf02690790&partnerID=40&md5=829fb3f87a4b87c33f4c4876de3f0226","The dynamics of eastward shifting cyclonic vortices are investigated in terms of a barotropic primitive equation model, and six experiments are performed. Both the interaction of a cyclonic vortex with vorticity lumps and the interaction of the vortex with the shearing basic flow may induce the strengthening of the vortex in a short period, however, the vortex intensity still shows a general decreasing tendency over the whole integration time period. The interaction among the shearing basic flow, cyclonic vortex, and multiple vorticity lumps can change the tendency. The merging of the cyclonic vortex with vorticity lumps in the shearing basic flow of positive vorticity is directly responsible for the maintenance and development of the cyclonic vortex."
"6506298579;7101630970;7402969850;","The relationship between the North American summer monsoon, the Rocky Mountains and the North Pacific subtropical anticyclone in HadAM3",2002,"10.1256/qj.01.145","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036820852&doi=10.1256%2fqj.01.145&partnerID=40&md5=b30d1433019119df2a417e772816a139","In this study the relationship between the North American monsoon, the Californian sea surface temperature (SST) cold pool, the Rocky Mountains and the North Pacific subtropical anticyclone is investigated using the Hadley Centre's atmospheric climate model, HadAM3. In 1996 Hoskins hypothesized that heating in the North American monsoon might be important for the maintenance of the summertime North Pacific subtropical anticyclone, since the monsoon heating may induce descent to the north-west of the monsoon in the descending eastern flank of the subtropical anticyclone. This descent is further enhanced by radiative cooling and is associated with equatorward surface winds parallel to the western coast of North America. These equatorward winds induce oceanic upwelling of cold water and contribute to the formation of the Californian SST cold pool, which may feed back on the anticyclone by further suppressing convection and inducing descent. More recently, Rodwell and Hoskins also investigated the global summer monsoon-subtropical anticyclone relationship. They examined the role that mountains play in impeding the progress of the low-level mid-latitude westerlies, either deflecting the westerlies northwards where they ascend along the sloping mid-latitude isentropes or deflecting them southwards forcing them to descend along the isentropes. In particular, the introduction of the Rockies into a primitive-equation model adiabatically induces descent in the eastern descending flank of the North Pacific subtropical anticyclone. These hypothesized mechanisms have been investigated using HadAM3, focusing on the possible suppression of convection by the Californian SST cold pool, the response of the North Pacific subtropical anticyclone to the strength of the North American monsoon and the 'blocking' of the mid-latitude westerlies by the Rocky Mountains. The role of the Rockies is examined by integrating the model with modified orography for the Rocky Mountains. Changing the height of the Rockies alters the circulation in a way consistent with the mechanism outlined above. Higher Rocky mountains force the westerlies southwards, inducing descent in the eastern flank of the subtropical anticyclone as the air descends along the sloping isentropes. The relationship between the North American monsoon and the North Pacific subtropical anticyclone is investigated by suppressing the monsoon in HadAM3. The suppression of the monsoon is accomplished by increasing the surface albedo over Mexico, which induces anomalous ascent on the eastward flank of the subtropical anticyclone and anomalous polewards surface winds along the western coast of the North American continent, also providing support for the above hypothesis. The removal of the Californian SST cold pool, however, has a statistically insignificant effect on the model, suggesting that in this model the feedback of the SST cold pool on the eastern flank of the anticyclone is weak."
"10046329200;","On frontal dynamics in two model oceans",2002,"10.1175/1520-0485(2002)032<2915:OFDITM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036812112&doi=10.1175%2f1520-0485%282002%29032%3c2915%3aOFDITM%3e2.0.CO%3b2&partnerID=40&md5=3aade09625cd78bfd666fb8852701294","Vertically homogeneous variable-temperature layer models are often used to describe upper-ocean variability, the dynamics of jets and fronts included. Frontogenesis is known to have a preference for strong cyclonic shears. When a frontal wave winds up ageostrophically, one would expect intense cyclones and more diffuse anticyclones to be the result. This is characteristics of both atmospheric weather and the oceanic equivalent. The frontal dynamics of the variable-temperature layer model is here compared with that of the three-dimensional primitive equations, the origin of the layer model. Whereas the primitive equation numerical experiments produce dynamics according to the above, the cyclonic and anticyclonic shears and eddies are equally amplified in the corresponding variable-temperature layer experiments. It is suggested that thermal wind is basal to the desired frontal characteristics and that the layer description fails because of the way it has been defined to have none."
"7004048039;22986560300;","Implementation of a mesh movement scheme in a multiply nested ocean model and its application to air-sea interaction studies",1999,"10.1175/1520-0493(1999)127<1879:ioamms>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0345009045&doi=10.1175%2f1520-0493%281999%29127%3c1879%3aioamms%3e2.0.co%3b2&partnerID=40&md5=f4b622083da0746f7d641db5ec418ec7","A mesh movement scheme is implemented in a multiply nested primitive equation ocean model. Mesh movement can be specified or determined in the course of the model run so as to follow an evolving oceanic feature, such as a wave front or propagating eddy, or atmospheric forcing, such as a tropical cyclone. Mass, heat, and momentum are conserved during the movement. The mesh movement scheme is tested in idealized and realistic configurations of the model. The idealized tests include simulations in which the moving meshes follow a propagating equatorial Kelvin wave, a dipole, or move across an existing mesoscale eddy. The tests demonstrate that the solutions in the fine-mesh region of the nested meshes reproduce well the equivalent solutions from uniform fine-mesh models. The model is applied for simulations of the ocean response to tropical cyclones, in which the moving meshes maintain high resolution near the cyclone center. The solution in the inner meshes reproduces very well the uniform fine-mesh simulation, in particular the sea surface temperature. It demonstrates that the moving meshes do not degrade the solution, even with the application of strong winds and the generation of energetic surface currents and near-inertial gravity waves. The mesh movement scheme is also successfully applied for a real-case simulation of the ocean response to Typhoon Roy (1998) in the western North Pacific. For this experiment, the model is initialized using the fields from a general circulation model (GCM) multiyear spinup integration of the large-scale circulation in the tropical Pacific Ocean. The nested-mesh solution shows no difficulty simulating the interaction of the storm-induced currents with the existing background circulation."
"7003531755;7004074265;","Simulation of tropical climate with a linear primitive equation model",1995,"10.1175/1520-0442(1995)008<2497:SOTCWA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029510167&doi=10.1175%2f1520-0442%281995%29008%3c2497%3aSOTCWA%3e2.0.CO%3b2&partnerID=40&md5=d11e8c38b3e53541f88ef02108d98b86","The tropical climate simulated with a new global atmosphere model is presented. In this paper the authors examine the sensitivity of the model's climate to specific formulations of convection, boundary-layer physics, and radiation. The model uses the Betts-Miller convection scheme and a parameterization of the planetary boundary layer (PBL) that combines similarity theory for computation of surface fluxes with a simple scheme for diagnosing PBL depth. Radiative cooling is specified and land surface processes are bypassed by relaxing modeled low-level values to observed quantities. Orography is ignored. The model contains six vertical layers and has a horizontal resolution of about 3° × 5.625°. The authors compare the climate simulated with two different version of the Betts-Miller convection scheme. -from Authors"
"10042470700;7006864972;","Explosive marine cyclogenesis in a three-layer model with a representation of slantwise convection: a sensitivity study",1995,"10.1175/1520-0469(1995)052<0533:EMCIAT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028975169&doi=10.1175%2f1520-0469%281995%29052%3c0533%3aEMCIAT%3e2.0.CO%3b2&partnerID=40&md5=6ebf0dadb7148b7ac3e074a88fe68dbf","The major results are as follows: 1) The control simulation produces a realistic explosive cyclone. 2) The cloud mass fraction at the top of the boundary layer, which is equal to the fractional area of slantwise ascent in a grid box, essentially determines the cloud mass flux transported into the large-scale atmosphere. 3) Shallow clouds are relatively insignificant in affecting the dynamics of explosive cyclones. 4) The surface drag force weakens the development of strong horizontal wind shear and the bent-back warm front. 5) The thermal gradient in the bent-back warm front gradually increases with the thermodynamic disequilibrium between the sea surface and the atmospheric boundary layer. 6) Enhanced vertical wind shear increases the deepening rate. 7) Weak low-level stability has significant impact on cyclogenesis. 8) The effect of stable condensation is to moderately accelerate the development of the baroclinic wave. -from Authors"
"7004890337;6701357023;","Simulation and predictability in a coupled TOGA model",1993,"10.1175/1520-0442(1993)006<1843:SAPIAC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027849786&doi=10.1175%2f1520-0442%281993%29006%3c1843%3aSAPIAC%3e2.0.CO%3b2&partnerID=40&md5=4d613405d2585ec53328b07549688acc","A model of the tropical ocean and global atmosphere is described. It consists of an aqua-planet form of version one of the NCAR Community Climate Model coupled to a primitive equation model for the upper tropical ocean in a rectangular basin. A 24-year simulation is described that has almost no climate drift, a good simulation of the mean temperature gradient across the ocean, but smaller than observed annual and interannual variability. In years 9-16 of the simulation there is a dominant oscillation with a period of two years. The spatial pattern of this oscillation shows up clearly in the first empirical orthogonal function calculated from monthly averages of sea surface temperature anomalies. A series of 19 model-twin predictability experiments were carried out with the initial perturbation being a very small change in the ocean temperature field. The correlation coefficient of monthly sea surface temperature anomalies from these model-twin experiments decreases rapidly over the first 6 months and after that, more slowly, showing that there is some predictability out to a year. -from Authors"
"6507024394;35552766800;","A coupled surface boundary-layer-quasigeostrophic model",1993,"10.1016/0377-0265(93)90009-V","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027790570&doi=10.1016%2f0377-0265%2893%2990009-V&partnerID=40&md5=bb69dd7cd07b7a385a400f810b2e409e","A three-dimensional model of the mesoscale surface boundary layer of the open ocean is developed through scale analysis of the primitive equations with mixing included. A set of surface boundary-layer equations appropriate for a broad range of oceanic and atmospheric scales is thereby derived. The essential basis of the model is a coupling between quasigeostrophic dynamics away from the boundary layer and arbitrary mixing models within the mixed layer. The coupling consists of advection of the boundary layer by the horizontal and vertical components of the interior quasigeostrophic flow and forcing of the interior by the boundary layer in the form of divergence within the boundary layer which leads to vortex stretching/compression in the interior. The divergence is generalized for mesoscale wind-driven flows and includes nonlinear interaction between the directly wind-driven boundary-layer flow and the interior flow in the form of interior relative vorticity advection by the wind-driven flow. The nature of the equations leads us to apply a numerical algorithm to their solution. This algorithm is calibrated through application to idealized problems to determine the temporal and spatial grid requirements. The model is initialized with a realistic ocean flow having the properties of the Gulf Stream. © 1993."
"7102596798;","Time-dependent numerical modelling of tides in the middle atmosphere",1993,"10.5636/jgg.45.41","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027430451&doi=10.5636%2fjgg.45.41&partnerID=40&md5=eb1208ffbb37abf952091a79c512d366","A spectral method is applied to the primitive equation system, in which horizontal momentum equations, thermodynamic equation and lower boundary conditions for the geopotential height are solved by the appropriate time integration scheme, with the continuity and hydrostatic equations solved downward and upward, respectively, in the altitude direction. Boundary conditions assume non-slip hypothesis below and diffusion-dominated spongy layer above. -from Author"
"7004723203;","Steady linear response to thermal forcing of an anomaly model with an asymmetric climatology",1990,"10.1175/1520-0469(1990)047<0148:SLRTTF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025620012&doi=10.1175%2f1520-0469%281990%29047%3c0148%3aSLRTTF%3e2.0.CO%3b2&partnerID=40&md5=a952bde6e829574b262983bd33c3a3d4","An anomaly model linearized around the observed winter climatology is used to study the steady response of the atmosphere to diabatic heating. The model is an R7, nine vertical levels, primitive equations, fully spectral model, derived from the GFDL GCM (Geophysical Fluid Dynamics Laboratory's General Circulation Model). The (R7) linear amomaly model is used to investigate the linear response to equatorial and midlatitude prescribed heating. The results indicate that the solution is affected by the presence of the stationary waves in the basic state. In particular, in the case of midlatitude heating large responses can be obtained for some locations of the heating. However, because of the low resolution used in these experiments no firm conclusions can be drawn on the role of baroclinic effects. -from Author"
"7004014731;","Deep circulations under simple classes of stratification",1989,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024484034&partnerID=40&md5=956c1e93a53db4cb8f63c01e352d07bd","Deep circulations, where the motion field is vertically aligned over one or more scale heights, are considered within the framework of the Primitive Equations in three dimensions. Under barotropic and equivalent barotropic stratifications, the attending circulations are governed by a two-dimensional reduction of the full primitive equations. The reduced system provides a natural framework for investigating the behavior of total column abundances of atmospheric constituents, eg, total ozone, measured by satellite. Although the immediate application of this system is to study barotropic circulations, because temperature variations along a lower bounding material surface are fully accounted for, the reduced system may be attractive for investigating a wider class of motions, eg, baroclinic disturbances where the heat flux is confined to the surface. -from Author"
"7201588628;7102447311;57192054908;57192054628;57192059156;37019326500;57192053273;","A Simulation of Seasonal Change of the Atmospheric General Circulation with a Low Resolution Spectral Model Part I: Calculated Monthly Mean Fields",1986,"10.2467/mripapers.37.53","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0009637072&doi=10.2467%2fmripapers.37.53&partnerID=40&md5=9e4a1dd5bcf579ec9dcb6ff617e39639","A low resolution spectral general circulation model has been developed for two aims. The first is to use the model as a tool to study the mechanisms of the atmospheric variations of longer terms than 10 days. The second is to perform preliminary studies on the dynamical long-range forecast. The model adopts primitive equations in which the dependent variables, except the mixing ratio of water vapor, are expressed by spherical harmonic functions with rhomboidal truncation of wavenumber 10. It has 10 layers including the lower stratosphere. To drive and maintain the general circulation of the model atmosphere, radiation, convection, turbulent vertical mixing in the planetary boundary layer, ground thermodynamics and hydrology are all incorporated by their widely used parameterization schemes. This paper describes the model performance by showing calculated monthly mean fields for January and July. These are obtained from the last 5 years results of simulated 6.5-year seasonal changes. We show that the major large-scale phenomena of the real atmosphere have been successfully simulated by the model. For example the stratospheric polar night jet and tropospheric subtropical jet are clearly separated in the winter hemisphere. Zonal mean and geographical distribution of monthly mean fields of wind, temperature and other parameters are realistic, although the model includes some defects such as the broader ITCZ and weakened Hadley circulation. In the stratosphere of the winter Northern Hemisphere, geopotential height and temperature structures well resemble the observed ones in both amplitude and phase. Stationary wave structures of geopotential height throughout the troposphere and stratsphere are also similar to the observed ones in the winter Northern Hemisphere, but hot in the winter Southern Hemisphere. © 1986, Japan Meteorological Agency / Meteorological Research Institute. All rights reserved."
"7102447311;","A numerical experiment on the general circulation of the middle atmosphere with a three-dimensional model explicitly representing internal gravity waves and their breaking",1984,"10.1007/BF01101878","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442604034&doi=10.1007%2fBF01101878&partnerID=40&md5=a7d619d9d4225f265f159b337c3c92da","The general circulation of the middle atmosphere is simulated by means of a three-dimensional primitive equation model which covers from the south pole to the north pole but is limited to a ten-degree sector in the latitudinal direction; cyclic conditions are imposed at the east-west lateral boundaries. The model is capable of explicitly representing internal gravity waves of zonal wavelength greater than a few hundred kilometers with the use of a one-degree mesh, but planetary-scale waves were excluded. No parameterization is employed for subgrid-scale eddy viscosity (or diffusivity). With the assumption of a simple external-heating function corresponding to solstice conditions, a time integration was performed for about thirty days from the motionless state. During the whole period, random forcings were imposed on each grid of the lowest level in order to generate small-scale upwardly propagating internal gravity waves. The experiment has shown that small-scale waves were indeed excited, propagated upward, broke up near the mesopause, and greatly changed the thermally induced zonal mean motion and temperature fields in the upper mesosphere and lower thermosphere. As a result, important features of the general circulation at those levels, such as reversals of the zonal motion and the latitudinal gradient of zonal mean temperature were reproduced. © 1985 Birkhäuser Verlag."
"7005447246;","Linear and nonlinear baroclinic instability of the Northern Hemisphere winter zonal flow.",1981,"10.1175/1520-0469(1981)038<2121:LANBIO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019677912&doi=10.1175%2f1520-0469%281981%29038%3c2121%3aLANBIO%3e2.0.CO%3b2&partnerID=40&md5=c383a1586be6f6c8d19adedab0f2a4dd","The baroclinic adjustment hypothesis is examined by considering first the linear stability of a variety of atmospheres, then the normal modes are integrated using a spectral primitive equation model and their nonlinear development is found to depend on the process of barotropic decay which is not a feature of the simple theoretical models. The time-averaged wave structure, as measured by Eliassen-Palm flux divergence patterns, shows a good agreement with climatological patterns. -from Author"
"7004274115;","An analysis of interactions between geostrophic and ageostrophic modes in a simple model.",1981,"10.1175/1520-0469(1981)038<0544:AAOIBG>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019657024&doi=10.1175%2f1520-0469%281981%29038%3c0544%3aAAOIBG%3e2.0.CO%3b2&partnerID=40&md5=208ebc375792ca4ecb236d1ff002f9fc","We examine some properties of the extratropical atmosphere which act to maintain quasi-geostrophic balance. A nonlinear, f-plane, primitive equation, two-layer model is used. The momentum and temperature fields are described in terms of normal modes of the system given by the model's linear terms. These modes are classified as either geostrophic or ageostrophic depending on their associated eigenvalues. The original nonlinear equations are transformed into a system in which the modulations of the modal amplitudes by nonlinear effects are explicitly expressed in terms of the modal amplitudes themselves. This transformation facilitates a multiple-time-scale analysis. -Author"
"53880473700;12787547600;15042618500;6506340624;7005304841;6602080205;","Mechanisms for a remote response to Asian anthropogenic aerosol in boreal winter",2019,"10.5194/acp-19-9081-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85069184532&doi=10.5194%2facp-19-9081-2019&partnerID=40&md5=457bc2330b608f7fe655d14b4b8c07cb","Asian emissions of anthropogenic aerosols and their precursors have increased rapidly since 1980, with half of the increase since the pre-industrial era occurring in this period. Transient experiments with the HadGEM3-GC2 coupled model were designed to isolate the impact of Asian anthropogenic aerosols on global climate in boreal winter. It is found that this increase has resulted in local circulation changes, which in turn have driven decreases in precipitation over China, alongside an intensification of the offshore monsoon flow. No large temperature changes are seen over China. Over India, the opposite response is found, with decreasing temperatures and increasing precipitation. The dominant feature of the local circulation changes is an increase in low-level convergence, ascent, and precipitation over the Maritime Continent, which forms part of a tropical Pacific-wide La Niña-like response.</p> <p>HadGEM3-GC2 also simulates pronounced far-field responses. A decreased meridional temperature gradient in the North Pacific leads to a positive Pacific-North American circulation pattern, with associated temperature anomalies over the North Pacific and North America. Anomalous northeasterly flow over northeast Europe drives advection of cold air into central and western Europe, causing cooling in this region. An anomalous anticyclonic circulation over the North Atlantic causes drying over western Europe. Using a steady-state primitive equation model, LUMA, we demonstrate that these far-field midlatitude responses arise primarily as a result of Rossby waves generated over China, rather than in the equatorial Pacific. © 2019. This work is distributed under the Creative Commons Attribution 4.0 License."
"23013601900;57205302128;57205299261;56842269600;7402627827;35812541300;57193696364;57193702053;","Evaluation of convection-permitting precipitation forecast products using WRF, NMMB, and FV3 for the 2016-17 NOAA hydrometeorology testbed flash flood and intense rainfall experiments",2019,"10.1175/WAF-D-18-0155.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068141336&doi=10.1175%2fWAF-D-18-0155.1&partnerID=40&md5=5d357ee5e61904b03052d4d2c07ddf9d","During the summers of 2016 and 2017, the Center for Analysis and Prediction of Storms (CAPS) ran real-time storm-scale ensemble forecasts (SSEFs) in support of the Hydrometeorology Testbed (HMT) Flash Flood and Intense Rainfall (FFaIR) experiment. These forecasts, using WRF-ARW and Nonhydrostatic Mesoscale Model on the B-grid (NMMB) in 2016, and WRF-ARW and GFDL Finite Volume Cubed-Sphere Dynamical Core (FV3) in 2017, covered the contiguous United States at 3-km horizontal grid spacing, and supported the generation and evaluation of precipitation forecast products, including ensemble probabilistic products. Forecasts of 3-h precipitation accumulation are evaluated. Overall, the SSEF produces skillful 3-h accumulated precipitation forecasts, with ARW members generally outperforming NMMB members and the single FV3 member run in 2017 outperforming ARW members; these differences are significant at some forecast hours. Statistically significant differences exist in the performance, in terms of bias and ETS, among subensembles of members sharing common microphysics and PBL schemes. Year-to-year consistency is higher for PBL subensembles than for microphysical subensembles. Probability-matched (PM) ensemble mean forecasts outperform individual members, while the simple ensemble mean exhibits substantial bias. A newly developed localized probability-matched (LPM) ensemble mean product was produced in 2017; compared to the simple ensemble mean and the conventional PM mean, the LPM mean exhibits improved retention of small-scale structures, evident in both 2D forecast fields and variance spectra. Probabilistic forecasts of precipitation exceeding flash flood guidance (FFG) or thresholds associated with recurrence intervals (RI) ranging from 10 to 100 years show utility in predicting regions of flooding threat, but generally overpredict the occurrence of such events; however, they may still be useful in subjective flash flood risk assessment. © 2019 American Meteorological Society."
"36644095800;13406399300;57202522440;57002623400;7102645933;6701431208;36992744000;31067496800;","Physics-dynamics coupling with element-based high-order Galerkin methods: Quasi-equal-area physics grid",2019,"10.1175/MWR-D-18-0136.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060246636&doi=10.1175%2fMWR-D-18-0136.1&partnerID=40&md5=ebf836a5b0dc56df2284077bb3d93dc6","Atmospheric modeling with element-based high-order Galerkin methods presents a unique challenge to the conventional physics-dynamics coupling paradigm, due to the highly irregular distribution of nodes within an element and the distinct numerical characteristics of the Galerkin method. The conventional coupling procedure is to evaluate the physical parameterizations (physics) on the dynamical core grid. Evaluating the physics at the nodal points exacerbates numerical noise from the Galerkin method, enabling and amplifying local extrema at element boundaries. Grid imprinting may be substantially reduced through the introduction of an entirely separate, approximately isotropic finite-volume grid for evaluating the physics forcing. Integration of the spectral basis over the control volumes provides an area-average state to the physics, which is more representative of the state in the vicinity of the nodal points rather than the nodal point itself and is more consistent with the notion of a ''large-scale state'' required by conventional physics packages. This study documents the implementation of a quasi-equal-area physics grid into NCAR's Community Atmosphere Model Spectral Element and is shown to be effective at mitigating grid imprinting in the solution. The physics grid is also appropriate for coupling to other components within the Community Earth System Model, since the coupler requires component fluxes to be defined on a finite-volume grid, and one can be certain that the fluxes on the physics grid are, indeed, volume averaged. © 2018 American Meteorological Society."
"32367837300;57203671855;56284582200;7404142321;","Atmospheric blocking and upper-level Rossby-wave forecast skill dependence on model configuration",2018,"10.1002/qj.3326","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055705096&doi=10.1002%2fqj.3326&partnerID=40&md5=8191b3cfc76ba7a934f6beee061eee93","Weather models differ in their ability to forecast, at medium range, atmospheric blocking and the associated structure of upper-level Rossby waves. Here, we evaluate the effect of a model's dynamical core on such forecasts. Operational forecasts from the ensemble prediction systems (EPSs) of the European Centre for Medium-Range Weather Forecasts (ECMWF), the Met Office (MO) and the Korean Meteorological Administration (KMA) are used. Northern Hemisphere model output is analysed from the winters before and after a major upgrade to the dynamical core of the MO-EPS (called MOGREPS). The KMA-EPS acts as a control as it uses the same model as MOGREPS, but uses the older dynamical core throughout. The confounding factor of resolution differences between MOGREPS and the KMA-EPS is assessed using a MO forecast model hindcast experiment with the more recent dynamical core, but with the operational resolution of the KMA-EPS. The introduction of the new dynamical core in MOGREPS has led to increased forecast blocking frequency, at lead times of 5 and 7 days, counteracting the typically observed reduction in blocking frequency with lead time. Hit rates of blocking activity, onset and decay are also increased in the main blocking regions (without a corresponding increase in the false positive rate). The previously found reduction of the upper-level ridge area and tropopause sharpness (measured by an isentropic potential vorticity gradient) with lead time is also reduced with the new dynamical core. This dynamical core improvement (associated with a reduction in implicit damping) is thus demonstrated to be at least as effective as operational resolution improvements in improving the forecasts of upper-level Rossby waves and associated blocking. © 2018 Crown copyright. Quarterly Journal of the Royal Meteorological Society © 2018 Royal Meteorological Society"
"57202451299;7103294731;7103413199;","On the coupling between barotropic and baroclinic modes of extratropical atmospheric variability",2018,"10.1175/JAS-D-17-0370.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048446634&doi=10.1175%2fJAS-D-17-0370.1&partnerID=40&md5=d6a9d6094d08204c7ef6ac86c71541f4","The baroclinic and barotropic components of atmospheric dynamics are usually viewed as interlinked through the baroclinic life cycle, with baroclinic growth of eddies connected to heat fluxes, barotropic decay connected to momentum fluxes, and the two eddy fluxes connected through the Eliassen-Palm wave activity. However, recent observational studies have suggested that these two components of the dynamics are largely decoupled in their variability, with variations in the zonal mean flow associated mainly with the momentum fluxes, variations in the baroclinic wave activity associated mainly with the heat fluxes, and essentially no correlation between the two. These relationships are examined in a dry dynamical core model under different configurations and in Southern Hemisphere observations, considering different frequency bands to account for the different time scales of atmospheric variability. It is shown that at intermediate periods longer than 10 days, the decoupling of the baroclinic and barotropic modes of variability can indeed occur as the eddy kinetic energy at those time scales is only affected by the heat fluxes and not the momentum fluxes. The baroclinic variability includes the oscillator model with periods of 20-30 days. At both the synoptic time scale and the quasi-steady limit, the baroclinic and barotropic modes of variability are linked, consistent with baroclinic life cycles and the positive baroclinic feedback mechanism, respectively. In the quasi-steady limit, the pulsating modes of variability and their correlations depend sensitively on the model climatology. © 2018 American Meteorological Society."
"57219012850;36992744000;","An Idealized Test of the Response of the Community Atmosphere Model to Near-Grid-Scale Forcing Across Hydrostatic Resolutions",2018,"10.1002/2017MS001078","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042412186&doi=10.1002%2f2017MS001078&partnerID=40&md5=42d51ce793e0019e703f239ffef7f8f5","A set of idealized experiments are developed using the Community Atmosphere Model (CAM) to understand the vertical velocity response to reductions in forcing scale that is known to occur when the horizontal resolution of the model is increased. The test consists of a set of rising bubble experiments, in which the horizontal radius of the bubble and the model grid spacing are simultaneously reduced. The test is performed with moisture, through incorporating moist physics routines of varying complexity, although convection schemes are not considered. Results confirm that the vertical velocity in CAM is to first-order, proportional to the inverse of the horizontal forcing scale, which is consistent with a scale analysis of the dry equations of motion. In contrast, experiments in which the coupling time step between the moist physics routines and the dynamical core (i.e., the “physics” time step) are relaxed back to more conventional values results in severely damped vertical motion at high resolution, degrading the scaling. A set of aqua-planet simulations using different physics time steps are found to be consistent with the results of the idealized experiments. © 2018. The Authors."
"7102315560;24598030900;6602611209;35276832600;","Stochastic subgrid modelling for geophysical and three-dimensional turbulence",2017,"10.1017/9781316339251.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032197838&doi=10.1017%2f9781316339251.010&partnerID=40&md5=63b2b1becbfab7f837d69d7432c22998","Stochastic modelling and closure-based approaches to the representation of the effects of subgrid turbulence in large eddy simulations (LES) of turbulent fluids are reviewed. The focus is on methods in which the subgrid model is calculated self-consistently from higher resolution benchmark simulations or closures. Eddy viscosity and stochastic backscatter parametrisations are presented for two-dimensional turbulence of barotropic flows, for baroclinic quasi-geostrophic turbulence of the atmosphere and oceans, for atmospheric flows in multi-level primitive equation models and for three-dimensional boundary layer turbulence in channels. The performance of LES with these parametrisations is examined. Subgrid scale parametrisations for the complex problem of inhomogeneous flows over topography are also analysed. © Cambridge University Press 2017."
"34772240500;55272477500;56919006400;6701335949;7004676489;57193213111;8922308700;6701333444;55688930000;56611366900;8859530100;","Modifications to WRF's dynamical core to improve the treatment of moisture for large-eddy simulations",2015,"10.1002/2015MS000532","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959481384&doi=10.1002%2f2015MS000532&partnerID=40&md5=16d25399a384fcefba70d4d3e14c784a","Yamaguchi and Feingold (2012) note that the cloud fields in their large-eddy simulations (LESs) of marine stratocumulus using the Weather Research and Forecasting (WRF) model exhibit a strong sensitivity to time stepping choices. In this study, we reproduce and analyze this sensitivity issue using two stratocumulus cases, one marine and one continental. Results show that (1) the sensitivity is associated with spurious motions near the moisture jump between the boundary layer and the free atmosphere, and (2) these spurious motions appear to arise from neglecting small variations in water vapor mixing ratio (qv) in the pressure gradient calculation in the acoustic substepping portion of the integration procedure. We show that this issue is remedied in the WRF dynamical core by replacing the prognostic equation for the potential temperature θ with one for the moist potential temperature θm=θ(1 + 1.61qv), which allows consistent treatment of moisture in the calculation of pressure during the acoustic substeps. With this modification, the spurious motions and the sensitivity to the time stepping settings (i.e., the dynamic time step length and number of acoustic sub-steps) are eliminated in both of the example stratocumulus cases. This modification improves the applicability of WRF for LES applications, and possibly other models using similar dynamical core formulations, and also permits the use of longer time steps than in the original code. © 2015. The Authors."
"7003298801;7202928871;15752418400;","Long-period tides in an atmospherically driven, Stratified Ocean",2015,"10.1175/JPO-D-15-0006.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84942789110&doi=10.1175%2fJPO-D-15-0006.1&partnerID=40&md5=aebb1d3ca18458c3e83ee5075656349b","Long-period tides (LPT) are studied using a stratified, primitive equation model on a global domain and in the presence of a fully developed, atmospherically forced ocean general circulation. The major LPT constituents, from termensual to nodal (18.6 yr) periods, are examined. Ocean circulation variability can overwhelm the longest tide signals and make inferring LPT from data difficult, but model results suggest that bottom pressure offers cleaner signal-to-noise ratios than sea level, particularly at low latitudes where atmospherically driven variability is substantially stronger at the surface than at the bottom. Most tides exhibit a significant large-scale dynamic response, with the tendency for weaker nonequilibrium signals in the Atlantic compared to the Pacific as seen in previous studies. However, across most tidal lines, the largest dynamic signals tend to occur in the Arctic and Nordic Seas and also in Hudson Bay. Bathymetry and coastal geometry contribute to the modeled nonequilibrium behavior. Baroclinic effects tend to increase with the tidal period. Apart from short spatial-scale modulations associated with topographic interactions, the excitation of various propagating baroclinic wave modes is clearly part of the modeled LPT, particularly at tropical latitudes, for fortnightly and longer-period tides. © 2015 American Meteorological Society."
"56567515600;36917877800;57214576588;6505772219;24474612500;56187499900;","On discontinuous Galerkin approach for atmospheric flow in the mesoscale with and without moisture",2014,"10.1127/0941-2948/2014/0565","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925384568&doi=10.1127%2f0941-2948%2f2014%2f0565&partnerID=40&md5=94d0f198bc702a6d40b3271c70728450","We present and discuss discontinuous Galerkin (DG) schemes for dry and moist atmospheric flows in the mesoscale. We derive terrain-following coordinates on the sphere in strong-conservation form, which makes it possible to perform the computation on a Cartesian grid and yet conserves the momentum density on an f-plane. A new DG model, i.e. DG-COSMO, is compared to the operational model COSMO of the Deutscher Wetterdienst (DWD). A simplified version of the suggested terrain-following coordinates is implemented in DG-COSMO and is compared against the DG dynamical core implemented within the DUNE framework, which uses unstructured grids to capture orography. Finally, a few idealised test cases, including 3d and moisture, are used for validation. In addition an estimate of efficiency for locally adaptive grids is derived for locally and non-locally occurring phenomena. © 2014 The authors."
"57197636789;24503245200;6602418877;","Testing the anelastic nonhydrostatic model EULAG as a prospective dynamical core of a numerical weather prediction model Part II: Simulations of supercell",2011,"10.2478/s11600-011-0051-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053500722&doi=10.2478%2fs11600-011-0051-z&partnerID=40&md5=cbee99e599a4465810c19b1ca99d7855","The anelastic nonhydrostatic model EULAG is a candidate for the future dynamical core of a numerical weather prediction model. Achieving such an objective requires a number of experiments focused on testing correctness of the solutions and robustness of the solver. In the spirit of this idea, a set of tests related to standard atmospheric problems was performed, of which the two regarding development and evolution of a supercell were employed as benchmarks of moist dynamics of the model. Their results are discussed in this paper. Development and evolution of a stormsystem with a set of characteristic features such as stormsplitting along with the generation of horizontal vorticity and cold pool formation is investigated. In addition, the influence of domain geometry, boundary conditions and subgrid-scale mixing is examined. © 2011 Versita Warsaw and Springer-Verlag Wien."
"6507253177;7003991093;","Circulation sensitivity to heating in a simple model of baroclinic turbulence",2010,"10.1175/2009JAS3314.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955588497&doi=10.1175%2f2009JAS3314.1&partnerID=40&md5=12a8b3a5d7bdcf9545f199b3c6799b48","This paper examines the sensitivity of the circulation of an idealized primitive equation two-level model on the form and strength of the heating, aiming to understand the qualitatively different sensitivity of the isentropic slope on differential heating reported by previous idealized studies when different model formulations are used. It is argued that this contrasting behavior might arise from differences in the internal determination of the heating. To test this contention, the two-level model is forced using two different heating formulations: a standard Newtonian cooling formulation and a highly simplified formulation in which the net lower-to-upper troposphere heat transport is prescribed by construction. The results are interpreted using quasigeostrophic turbulent closures, which have previously been shown to have predictive power for the model. It is found that the strength of the circulation, as measured by eddy length and velocity scales and by the strength of the energy cycle, scales with the vertical heating (the lower-to-upper troposphere heat transport), with a weak dependence. By contrast, the isentropic slope is only sensitive to the structure of the heating, as measured by the ratio between meridional versus vertical heating, and not to the actual strength of the heating. In general the heating is internally determined, and this ratio may either increase or decrease as the circulation strengthens. It is shown that the sign of the sensitivity depends on the steepness of the relation between vertical heating and stratification for the particular heating formulation used. The quasigeostrophic limit (fixed stratification) and the prescribed heating model constrain the possible range of behaviors and provide bounds of sensitivity for the model. These results may help explain the different sensitivity of the isentropic slope on differential heating for dry and moist models and for quasigeostrophic and primitive equation models. © 2010 American Meteorological Society."
"8674035000;","Temperature decrease in the extratropics of South America in response to a tropical forcing during the austral winter",2010,"10.5194/angeo-28-1-2010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-76649140085&doi=10.5194%2fangeo-28-1-2010&partnerID=40&md5=18445f509af72bec637a8901396e495c","This paper focuses on the dynamic mechanisms that create favorable conditions for the occurrence of frosts that affect large areas of Argentina and are denominated generalized frosts (GF). The hemispheric teleconnection patterns linked to extreme cold events affecting central and northeastern Argentina during winter are identified. The objective is to determine whether the conditions found in previous studies for the composite of winters with extreme (maximum and minimum) frequency of GF occurrence respond to typical characteristics of the austral winter or they are inherent to those particular winters. Taking the mean winter as basic state in the 1961ĝ€"" 1990 period, a series of numerical experiments are run using a primitive equation model in which waves are excited with a thermal forcing. The positions of the thermal forcing are chosen according to observed convection anomalies in a basic state given by the austral winters with extreme frequency of GF occurrence. The wave trains excited by anomalous convection situated in specific regions may propagate across the Pacific Ocean and reach South America with the appropriate phase, creating the local favorable conditions for the occurrence of GF. However, the anomalous convection is, by itself, not sufficient since the response also depends on the basic state configuration. This is proved by placing the forcing over the region of significant anomalous convection for maximum and minimum frequency of GF occurrence and the response was very different in comparison to the mean winter. It is concluded that the conditions for a greater GF frequency of occurrence are inherent to these particular winters, so that such conditions are not present in the average winter."
"8266754800;8874929700;7103158914;7101785401;","The modulation of ENSO variability in CCSM3 by extratropical Rossby waves",2009,"10.1175/2009JCLI2922.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77649281648&doi=10.1175%2f2009JCLI2922.1&partnerID=40&md5=f5d24a9b53f1ece087857cf08f77528a","Evidence suggests that the magnitude and frequency of the El Niño-Southern Oscillation (ENSO) changes on interdecadal time scales. This is manifest in a distinct shift in ENSO behavior during the late 1970s. This study investigates mechanisms that may force this interdecadal variability and, in particular, on modulations driven by extratropical Rossby waves. Results from oceanic shallow-water models show that the Rossby wave theory can explain small near-zonal changes in equatorial thermocline depth that can alter the amplitude of simulated ENSO events. However, questions remain over whether the same mechanism operates in more complex coupled general circulation models (CGCMs) and what the magnitude of the resulting change would be. Experiments carried out in a state-of-the-art z-coordinate primitive equation model confirm that the Rossby wave mechanism does indeed operate. The effects of these interactions are further investigated using a partial coupling (PC) technique. This allows for the isolation of the role of wind stress-forced oceanic exchanges between the extratropics and the tropics and the subsequent modulation of ENSO variability. It is found that changes in the background state of the equatorial Pacific thermocline depth, induced by a fixed offequatorial wind stress anomaly, can significantly affect the probability of ENSO events occurring. This confirms the results obtained from simpler models and further validates theories that rely on oceanic wave dynamics to generate Pacific Ocean interdecadal variability. This indicates that an improved predictive capability for seasonal-to-interannual ENSO variability could be achieved through a better understanding of extratropical-to-tropical Pacific Ocean transfers and western boundary processes. Furthermore, such an understanding would provide a physical basis to enhance multiyear probabilistic predictions of ENSO indices. © 2009 American Meteorological Society."
"57196170962;7004429544;6602859094;7101807288;7202484739;","A sensitivity study of the Kelvin wave and the Madden-Julian Oscillation in aquaplanet simulations by the Naval Research Laboratory Spectral Element Atmospheric Model",2008,"10.1029/2008JD009887","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58149267693&doi=10.1029%2f2008JD009887&partnerID=40&md5=203016e55b90855f0aeca2dcdb3691c6","The dynamical core of the Naval Research Laboratory (NRL) Spectral Element Atmospheric Model (NSEAM) is coupled with full physics and used to investigate the organization and propagation of equatorial atmospheric waves under the aquaplanet conditions. The sensitivity of the model simulation to the amount of horizontal viscosity, distribution of the vertical levels, and selected details of the precipitation physics is examined and discussed mainly utilizing simulated convective precipitation with the aid of time-longitude plots and the spectral diagrams designed by Wheeler and Kiladis (1999). It is shown that the simulation of the Kelvin wave and Madden-Julian Oscillation depends strongly on the details of the vertical level distribution and the choice of parameters in the convective parameterization. Efforts are made to calibrate the new model to capture the essential interaction between the dynamics and physics of the atmosphere. The speed and spectrum of the eastward propagating Kelvin waves and the signature of the Madden-Julian Oscillation simulated by the new model reveal main features similar to those predicted by the simplified theory and found in limited observations. This study attempts to understand the significant variability found among the aquaplanet simulations by various global atmospheric models and highlights the uncertainties concerning convective processes and their coupling to large-scale wave motion in large-scale models of the atmosphere."
"7006581229;7403253358;","A three-dimensional wave-activity relation for pseudomomentum",2007,"10.1175/JAS3931.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347391755&doi=10.1175%2fJAS3931.1&partnerID=40&md5=637d0c79ea121b8d6010e1b5315f9dd8","A three-dimensional, nonhydrostatic local wave-activity relation for pseudomomentum is derived from the nonhydrostatic primitive equations in Cartesian coordinates by using an extension of the momentum-Casimir method. The stationary and zonally symmetric basic states are chosen and a Casimir function, which is the single-valued function of potential vorticity and potential temperature, is introduced in the derivation. The wave-activity density and wave-activity flux of the local wave-activity relation for pseudomomentum are expressed entirely in terms of Eulerian quantities so that they are easily calculated with atmospheric data and do not require the knowledge of particle placements. Constructed in the ageostrophic and non-hydrostatic dynamical framework, the local wave-activity relation for pseudomomentum is applicable to diagnosing the evolution and propagation of mesoscale weather systems. © 2007 American Meteorological Society."
"7401699378;56098717400;","A validation of the fractal dimension of cloud boundaries",2007,"10.1029/2006GL028472","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250176377&doi=10.1029%2f2006GL028472&partnerID=40&md5=4b089e7243313a99d985d97cbc62b22f","In this paper the problem of the fractal dimension of the perimeter of self-organized vortices is investigated. Results from two numerical models (using the quasi geostrophic vorticity equation and the system of barotropic primitive equations, respectively) with initial fields where the total number of initial small-scale vortices is 72, and their intensities and locations are determined stochastically, indicate that the quasi-final kinetic energy fields have a power spectrum of the form E (k) ∼ k-β, β ≈ 1.0, and the fractal dimension of the perimeter of self-organized vortices falls near 4/3. An estimation of the fractal dimension using 77 cloud samples from cloud picture data is shown to be 1.30. The simulated fractal dimension here validates results previously computed based on satellite images (1.35), and is similar to results previously modeled by Large-Eddy-Simulation and indicated by the theory of relative turbulent diffusion. Copyright 2007 by the American Geophysical Union."
"15759448500;6507560058;11939570000;","Sensitivity studies on vortex development over a polynya",2007,"10.1007/s00704-006-0233-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846045730&doi=10.1007%2fs00704-006-0233-9&partnerID=40&md5=06dca9500e19c4325ce712a4d4540fc3","The development of a cyclonic vortex over a polynya is investigated with the primitive equation mesoscale model METRAS. The impact of different atmospheric processes on vortex development is determined by calculating the terms of the vorticity tendency equation. Sensitivity studies are performed for different large-scale situations (geostrophic winds 1 ms-1, 3 ms-1, 20 ms-1, initial ice-water temperature difference of 35 K or 17.5 K) and for different polynya sizes and shapes. In general, the vortex develops within a few hours. It is intensified by buoyancy, mainly resulting from latent heat release. Advective and diffusive processes hinder the vortex development. The intensification depends on the actual situation and is faster over small polynyas and heterogeneous ice cover. These situations result in intensification periods of only 12 to 18 hours for the vortex, but create very strong vortices. Halved horizontal temperature gradients also about halve the vortex intensity. The lifetime and intensification of a vortex increases with the time the air mass spends over the water. Thus, weak winds show a slower development of the vortex but the vortex intensifies for more than 24 hours. Over big polynyas several vortices develop, a long polynya results in a longer and narrower vortex which intensifies over a longer period. © Springer-Verlag 2006."
"6602695122;7004593510;7005516423;","Local log-law-of-the-wall in neutrally-stratified boundary-layer flows",2003,"10.1023/A:1021599714936","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037399467&doi=10.1023%2fA%3a1021599714936&partnerID=40&md5=f4b79fadb36d524c25ad6ea6e41f3e9a","It is well known that in a neutrally-stratified turbulent flow in a deep constant-stress layer above a flat surface, the horizontal mean velocity varies logarithmically with height (the so-called 'log-law-of-the-wall'). More recently, the same logarithmic law has also been found in the presence of non-flat surfaces, where it governs the dynamics of the areally-averaged velocity and involves renormalized effective parameters. Here, we analyze wind profiles over two-dimensional sinusoidal hills obtained both from numerical simulations performed with a primitive equation model and from wind-tunnel measurements. We show that also the local velocity profiles behave to a very good approximation logarithmically, for a distance from the surface of the order of the maximum hill height almost to the top of the boundary layer. Such a local log-law-of-the-wall involves effective parameters smoothly depending on the position along the underlying topography. This dependence looks very similar to the topography itself."
"7006544551;6505780102;6507427790;","A high resolution hydrodynamic 3-D model simulation of the Malta shelf area",2003,"10.5194/angeo-21-323-2003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0038794025&doi=10.5194%2fangeo-21-323-2003&partnerID=40&md5=87bdfd7995423caf1b8990ca49d744b1","The seasonal variability of the water masses and transport in the Malta Channel and proximity of the Maltese Islands have been simulated by a high resolution (1.6 km horizontal grid on average, 15 vertical sigma layers) eddy resolving primitive equation shelf model (ROSARIO-I). The numerical simulation was run with climatological forcing and includes thermohaline dynamics with a turbulence scheme for the vertical mixing coefficients on the basis of the Princeton Ocean Model (POM). The model has been coupled by one-way nesting along three lateral boundaries (east, south and west) to an intermediate coarser resolution model (5 km) implemented over the Sicilian Channel area. The fields at the open boundaries and the atmospheric forcing at the air-sea interface were applied on a repeating ""perpetual"" year climatological cycle. The ability of the model to reproduce a realistic circulation of the Sicilian-Maltese shelf area has been demonstrated. The skill of the nesting procedure was tested by model-model comparisons showing that the major features of the coarse model flow field can be reproduced by the fine model with additional eddy space scale components. The numerical results included upwelling, mainly in summer and early autumn, along the southern coasts of Sicily and Malta; a strong eastward shelf surface flowalong shore to Sicily, forming part of the Atlantic Ionian Stream, with a presence throughout the year and with significant seasonal modulation, and a westward winter intensified flow of LIW centered at a depth of around 280 m under the shelf break to the south of Malta. The seasonal variability in the thermohaline structure of the domain and the associated large-scale flow structures can be related to the current knowledge on the observed hydrography of the area. The level of mesoscale resolution achieved by the model allowed the spatial and temporal evolution of the changing flow patterns, triggered by internal dynamics, to be followed in detail. This modelling effort has initiated the treatment of the open boundary conditions problem in view of the future implementation of shelf-scale real-time ocean forecasting through the sequential nesting of a hierarchy of successively embedded model domains for the downscaling of the hydrodynamics from the coarse grid Ocean General Circulation Model of the whole Mediterranean Sea to finer grids in coastal areas."
"7402887257;6701676992;","Effect of the Hadley circulation on the reflection of planetary waves in three-dimensional tropospheric flows",2002,"10.1175/1520-0469(2002)059<2846:EOTHCO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036797497&doi=10.1175%2f1520-0469%282002%29059%3c2846%3aEOTHCO%3e2.0.CO%3b2&partnerID=40&md5=396d3b7faaa9ec65e97a3885a748c4aa","The nonlinear behavior of quasi-stationary planetary waves excited by midlatitude orographic forcing is considered in a three-dimensional primitive equation model that includes a representation of the Hadley circulation. The Hadley circulation is forced by Newtonian cooling to a zonally symmetric reference temperature and vertical diffusion on the zonally symmetric component of the flow. To quantify the effect of the Hadley circulation on wave propagation, breaking, and nonlinear reflection, an initial state with no meridional flow, but with the same zonal flow as the Hadley state, is also considered. In order to allow the propagation of large- scale waves over extended periods. Rayleigh friction is applied at low levels to delay the onset of baroclinic instability. As in the absence of a Hadley circulation, the waves in the Hadley state propagate toward low latitudes where the background flow is weak and the waves are therefore likely to break. Potential vorticity fields on isentropic surfaces are used to diagnose wave breaking. Nonlinear pseudomomentum conservation relations are used to quantify the absorption-reflection behavior of the wave breaking region. In the presence of a Hadley circulation representative of winter conditions, the nonlinear reflection requires more forcing to get established, but a reflected wave train is still present in the numerical simulations, both for a longitudinally symmetric forcing and for the more realistic case of an isolated forcing. The effect of the thermal damping on the waves is more severe in the current three-dimensional simulations than in the shallow water case considered in an earlier study. Both the directly forced wave train and the reflected wave train are quite barotropic in character: however, in the shallow water case one is essentially assuming an infinite vertical scale."
"6602380901;7402132050;7005251447;","Large scale geostrophic winds with a full representation of the Coriolis force: Application to IR observations of the upper Jovian troposphere",2002,"10.1080/03091920290027943","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33747703688&doi=10.1080%2f03091920290027943&partnerID=40&md5=6023ceada87976d41c15d24c91e441b0","The diagnostics of large scale geostrophy in a stratified atmosphere are revisited in pressure coordinates using a full Coriolis force. This formulation of geostrophy includes the horizontal and vertical projections of the planetary rotation vector, is valid for shallow and deep atmospheres, accounts for the spherical geometry of the atmosphere, is not singular at the equator, and provides partial information about vertical velocities. The new expressions, although an improvement over the standard approach, are still only estimates because of the terms that are being neglected and because of the uncertainties in the observational data. The magnitudes of the errors are discussed. The accuracy of the standard hydrostatic approximation in the geostrophic regime is gauged and an alternative approach is discussed. The standard hydrostatic approximation predicts much smaller wind shears than those derived from the primitive equations. The observations are a set of global temperature maps of the upper Jovian troposphere at pressures, between 100 and 400mbar, obtained from mid-infrared observations in June, 1996. Maps of the large-scale thermal winds show higher concentration of longitudinal structures and vertical velocities along two particular zonal bands at latitudes near 15°N and 15°S. Observational criteria are proposed to validate the standard versus the new diagnostic as well as the possible geostrophic regime of Jupiter's zonal jets."
"6603075103;","Phase relations for high frequency core-mantle coupling and the Earth's axial angular momentum budget",2001,"10.1016/S0031-9201(01)00284-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035681945&doi=10.1016%2fS0031-9201%2801%2900284-9&partnerID=40&md5=82afa3fc2705a5fd17d01b8fcb55ef77","Although it has long been thought that dynamical core-mantle coupling is necessary for understanding decadal variations in the length of day (LOD), the physics of the coupling mechanism are very poorly constrained. There several hypotheses-electromagnetic, topographic, gravitational, viscous - but it is notoriously difficult to distinguish between them on observational grounds. There is both an expectation [Geophys. J. Int. 138 (1999) 679] and some evidence [J. Geophys. Res. 100 (1995) 8233; Geophys. Res. Lett. 24 (1997a) 1799] that there is significant core-mantle coupling on much faster timescales, down to subannual periods. At such frequencies, the core would no longer be the dominant driving force for LOD, but would instead interact with both the mantle and external reservoirs of angular momentum such as the atmosphere and ocean. On these much faster timescales, it is possible that some information that is obscured on decadal timescales becomes available: in particular, any characteristic timescales at very short periods may become observable. Here, I examine the angular momentum budget of the Earth on subannual to annual timescales for any additional implied constraints on the physics of angular momentum exchange between the core and the mantle. I find that the discrepancy between atmospheric angular momentum and mantle angular momentum on timescales where the ocean is thought to be unimportant has a distinctive signature which is difficult to reproduce using simple models of core-mantle coupling, although an ad hoc frictional<sub/>model does moderately well. Rather than indicating simplicity, this may instead be symptomatic of great complexity in the physics of the core-mantle boundary region. © 2001 Elsevier Science B.V. All rights reserved."
"56455165800;7003440089;","Simulation of marine stratocumulus: Effect of precipitation parameterization and sensitivity to droplet number concentration",1998,"10.1023/A:1001732526989","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032449521&doi=10.1023%2fA%3a1001732526989&partnerID=40&md5=7e175a8d0a62db3d36cbc251583ecd9b","Marine stratocumulus observations show a large variability in cloud droplet number concentration (CDNC) related to variability in aerosol concentration. Changes in CDNC modify the cloud reflectivity, but also affect cloud water content, cloud lifetime, and cloudiness, through changes in precipitation. In mesoscale models and general circulation models (GCMs), precipitation mechanisms are parameterized. Here we examine how the precipitation parameterization can affect the simulated cloud. Simulations are carried out with the one-dimensional version of the hydrostatic primitive equation model MAR (Modele Atmospherique Regional) developed at the Universite catholique de Louvain. It includes a E-ε turbulence closure, a wide-band formulation of the radiative transfer, and a parameterized microphysics including prognostic equations for water vapour, cloud droplets and rain drops concentrations. In a first step, the model is used to simulate a horizontally homogeneous stratocumulus deck observed during the Atlantic Stratocumulus Transition Experiment (ASTEX) on the night of 12-13 June 1992. The observations show that the model is able to realistically reproduce the vertical structure of the cloud-topped boundary layer. In a second step, several precipitation parameterizations commonly used in mesoscale models and GCMs are tested. It is found that most parameterizations tend to overestimate the precipitation, which results in an underestimation of the vertically integrated liquid water content. Afterwards, using those parameterizations that are sensitive to CDNC, several simulations are performed to estimate the effect of CDNC variations on the simulated cloud. Based upon the simulation results, we argue that currently used parameterizations do not enable assessment of such a sensitivity."
"56203249800;6603156317;7003876681;7102181630;","The Arctic ocean-ice system studied by contamination modelling",1997,"10.3189/s0260305500013732","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031400129&doi=10.3189%2fs0260305500013732&partnerID=40&md5=da32174391489f9acbef1497470b549c","The Arctic represents a relatively pristine frontier that is vulnerable to pollution. Substances originating at mid latitudes are transported to the Arctic by atmospheric processes, ocean currents and rivers. These pollutants can accumulate in the Arctic environment. Testing of nuclear weapons, dumping of waste and operation of ships, and nuclear power plants also pose threats. To investigate possible pollutant pathways we used a multi-level primitive-equation ocean model, coupled to a dynamic-thermodynamic sea-ice model. Coupling included conservative transfer of momentum, heat and fresh water. Atmospheric forcing (wind stress, temperature, humidity, radiation and heat fresh-water fluxes) was supplied by datasets or bulk formulae. Open lateral-boundary conditions for the ocean model were supplied either by datasets (temperature and salinity) or from a larger-scale ocean model (momentum). Two integrations were compared - one used a centred-difference advection scheme and viscous damping, while the other used a better representation of an advection scheme and a sub-gridscale eddy parameterization. Tracer simulations showed (1) the importance of good representation of numerical advection, and (2) the role of eddy interacting with sea-floor topography (the neptune effect)."
"6506464094;7004953446;","Some aspects of the sensitivity of idealized frontal waves",1996,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030422722&partnerID=40&md5=13a7e4f64926afeee8146505276f05f9","The adjoint of the doubly-periodic primitive equation model ARPEGE/ALADIN has been developed in order to study the sensitivity of two idealized frontal waves. The latter derives from the instability of frontal zones induced by low level potential vorticity anomalies. The reference trajectories are provided by the non-linear evolution of normal mode waves. The sensitivity of integral diagnostic properties (kinetic energy and geostrophic enstrophy) is computed. Two periods during the life-cycle are considered: the period of maximum linear amplification and a period following the end of the active phase. The sensitivity to the initial front is separated from that to the wave. Results for the development phase are compared to singular vector analysis. The most unstable singular vectors along the steady front are shown to control the behaviour of the sensitivity. However, the singular vectors do not grow from an interaction that is not already described by the normal mode solution. In other words, there is no strong sensitivity to upper-level anomalies. In the neutral phase, direct runs initialized with the gradients show that rather complex perturbations starting from the area between two waves can, at best, add a cold front to the waves. The gradients are analysed in terms of potential vorticity."
"6506041382;","A shallow-water semi-geostrophic model on a sphere",1996,"10.1256/smsqj.52910","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029657350&doi=10.1256%2fsmsqj.52910&partnerID=40&md5=b20dad31a4bf252c0ade8a44c37fd467","The f-plane semi-geostrophic equations have provided much insight into atmospheric motions and we wish to see if more can be gained by removing the f-plane restriction. As a first step we begin by considering the shallow-water semi-geostrophic equations on a sphere and describe a numerical solution procedure for them based on a semi-Lagrangian predictor-corrector method. It is demonstrated, numerically, that the method appears to converge to a true solution of the semi-geostrophic equations for fixed resolution, and this suggests that there is a unique solution to the continuous equations. The results from several idealized and real-data test problems are presented and show that the scheme is stable and accurate. The results are compared with those obtained from a shallow-water semi-Lagrangian primitive-equation model. The simulations are broadly similar but the semi-geostrophic solution maintains stronger anticyclones than the primitive-equation model. This is in agreement with results expected after considering f-plane baroclinic wave simulations with the effects of spherical geometry taken into account."
"7404085513;","Methods for obtaining stationary solutions of the primitive equation model and stationary and periodic solutions of the quasi-geostrophic model",1993,"10.2151/jmsj1965.71.3_305","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000893739&doi=10.2151%2fjmsj1965.71.3_305&partnerID=40&md5=1071b44e7f29e827b69c2d0ddc0d4cab","Methods for obtaining stationary solutions of the primitive equation model and stationary and periodic solutions of the quasi-geostrophic model are proposed. The key is to construct the spectral models based on the spectral coefficient method, in which non-linear terms are calculated by the interaction coefficient method. This is required to obtain explicitly Jacobian matrices which are necessary for solving the non-linear equation system by Newton’s method. Thus, solutions can be obtained for the models with a resolution which can simulate the real atmosphere. Further, a linear stability analysis for these solutions can be made. In this course, several devices for computations are necessary, particularly since the both models have diagnostic equations and the calculations of non-linear terms is complicated. Applications to various problems and future developments are also discussed. © 1993, Meteorological Society of Japan."
"8833354000;7102696820;57188570624;","A limited area model for monsoon prediction",1990,"10.1007/BF02919174","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025247559&doi=10.1007%2fBF02919174&partnerID=40&md5=df6b092e3ec3fcb1dce8df9bc20a142e","A six level regional primitive equation model has been formulated and tested for monsoon prediction. The model uses dynamic normal mode initialization scheme for obtaining initial balance. The physical processes included are: the large scale condensation, the Kuo type of eumulus convection, the surface friction, the sursible heat supply and evaporation over the sea. The actual smooth orography is included. The model has been integrated for 48 hrs using input of 7 July and 8 August 1979 when the domain of integration was dominated by an intense monsoon depression. In order to investigate the model simulation of formative stage of the depression, the model was also integrated using input of 4 July 1979. Furthermore, the envelope orography has been constructed and included in the model for investigating its effects on the monsoon prediction. Results of the model forecast are presented and discussed. © 1990, Advances in Atmospheric Sciences. All rights reserved."
"7004014731;","Deep circulations under simple classes of stratification",1989,"10.1111/j.1600-0870.1989.tb00365.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981598907&doi=10.1111%2fj.1600-0870.1989.tb00365.x&partnerID=40&md5=f9e86d7567a59fc77cbe7dfc04eb1615","Deep circulations, where the motion field is vertically aligned over one or more scale heights, are considered within the framework of the Primitive Equations in three dimensions. Important in both tropospheric and stratospheric applications, such motions are admitted by special classes of stratification, where two families of thermodynamic surfaces are not completely independent, as is true under generally baroclinic conditions. Under barotropic and equivalent barotropic stratifications, the number of degrees of freedom are reduced by one, so that the attending circulations are governed by a two‐dimensional reduction of the full primitive equations. The reduced two‐dimensional equations governing these motions are derived from the three‐dimensional primitive equations in spherical geometry. In so doing, a mapping is established between the full primitive equations and a reduced two‐dimensional system, under these special classes of stratification. Very little approximation is required in the derivation of this system, particularly within the framework of isentropic coordinates. Although not strictly equal to the shallow water equations, the reduced set is of the same general form and therefore is amenable to the same methods of solution. Moreover, while the shallow water equations serve as a heuristic analogue of atmospheric behavior, the equivalent barotropic system derived here explicitly represents atmospheric variables. The equivalent depth, an arbitrary parameter in the shallow water equations, emerges implicitly in the derivation of this system, which obeys a conservation principle analogous to Ertel's theorem for three‐dimensional flow. Owing to its correspondence to the full primitive equations, the equivalent barotropic system provides a physical basis for carrying out two‐dimensional integrations (e.g., detailed transport calculations of very high resolution) to investigate deep atmospheric motions. The reduced system also provides a natural framework for investigating the behavior of total column abundances of atmospheric constituents, e.g., total ozone, measured by satellite. Although the immediate application of this system is to study barotropic circulations, because temperature variations along a lower bounding material surface are fully accounted for, the reduced system may be attractive for investigating a wider class of motions, e.g., baroclinic disturbances where the heat flux is confined to the surface. 1989 Blackwell Munksgaard"
"6603645440;57203078473;","Transport of atmospheric tracers by planetary waves during a winter stratospheric warming event: A three-dimensional model simulation",1986,"10.1029/jd091id12p13167","https://www.scopus.com/inward/record.uri?eid=2-s2.0-17044450164&doi=10.1029%2fjd091id12p13167&partnerID=40&md5=30b78400ef3b35f8343a3fe8398cd08f","In a simple three-dimensional primitive equation model, a wave number 1 major stratospheric warming is simulated. With the aid of two idealized tracers it is shown that the transport during a major warming event is characterized by a small, well-organized tongue of subtropical air flowing around the displaced winter vortex into the polar cap and by a wide area with strong quasi-horizontal mixing (surf zone). The description of these dynamical processes requires a full three-dimensional space resolution."
"57216005348;","A high resolution numerical study of the sea-breeze front",1974,"10.1080/00046973.1974.9648375","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4844231929&doi=10.1080%2f00046973.1974.9648375&partnerID=40&md5=79725a8431ef837a43e91b7114531da7","The primitive equations are integrated numerically using a high resolution grid to investigate the sea-breeze front Two cases of the sea-breeze front are presented; the first produced in an atmosphere with a prevailing offshore flow, and the second produced in an atmosphere initially at rest. © Taylor & Francis Group, LLC."
"57120925400;57208304879;26633770700;54387426400;26321327000;56612043200;57202522440;7004245252;","HOMMEXX 1.0: A performance-portable atmospheric dynamical core for the Energy Exascale Earth System Model",2019,"10.5194/gmd-12-1423-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064412649&doi=10.5194%2fgmd-12-1423-2019&partnerID=40&md5=2378edbc25dc722a1f1113a2d3e2efa0","We present an architecture-portable and performant implementation of the atmospheric dynamical core (High-Order Methods Modeling Environment, HOMME) of the Energy Exascale Earth System Model (E3SM). The original Fortran implementation is highly performant and scalable on conventional architectures using the Message Passing Interface (MPI) and Open MultiProcessor (OpenMP) programming models. We rewrite the model in C++ and use the Kokkos library to express on-node parallelism in a largely architecture-independent implementation. Kokkos provides an abstraction of a compute node or device, layout-polymorphic multidimensional arrays, and parallel execution constructs. The new implementation achieves the same or better performance on conventional multicore computers and is portable to GPUs. We present performance data for the original and new implementations on multiple platforms, on up to 5400 compute nodes, and study several aspects of the single-and multi-node performance characteristics of the new implementation on conventional CPU (e.g., Intel Xeon), many core CPU (e.g., Intel Xeon Phi Knights Landing), and Nvidia V100 GPU. © 2019 Author(s)."
"18435749300;57208455668;55119602800;57192468922;57075896200;7201972249;57195587405;","Evaluation of tropical cyclone forecasts in the next generation global prediction system",2019,"10.1175/MWR-D-18-0227.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075809238&doi=10.1175%2fMWR-D-18-0227.1&partnerID=40&md5=a7beb9276730ce0a6454263e0f96e25e","A new global model using the GFDL nonhydrostatic Finite-Volume Cubed-Sphere Dynamical Core(FV3) coupled to physical parameterizations from the National Centers for Environmental Prediction'sGlobal Forecast System (NCEP/GFS) was built at GFDL, named fvGFS. The modern dynamical core,FV3, has been selected for the National Oceanic and Atmospheric Administration's Next GenerationGlobal Prediction System (NGGPS) due to its accuracy, adaptability, and computational efficiency, whichbrings a great opportunity for the unification of weather and climate prediction systems. The performanceof tropical cyclone (TC) forecasts in the 13-km fvGFS is evaluated globally based on 363 daily cases of 10-day forecasts in 2015. Track and intensity errors of TCs in fvGFS are compared to those in the operationalGFS. The fvGFS outperforms the GFS in TC intensity prediction for all basins. For TC track prediction,the fvGFS forecasts are substantially better over the northern Atlantic basin and the northern PacificOcean than the GFS forecasts. An updated version of the fvGFS with the GFDL 6-category cloud microphysics scheme is also investigated based on the same 363 cases. With this upgraded microphysicsscheme, fvGFS shows much improvement in TC intensity prediction over the operational GFS. Besidestrack and intensity forecasts, the performance of TC genesis forecast is also compared between the fvGFSand operational GFS. In addition to evaluating the hit/false alarm ratios, a novel method is developed toinvestigate the lengths of TC genesis lead times in the forecasts. Both versions of fvGFS show higher hitratios, lower false alarm ratios, and longer genesis lead times than those of the GFS model in most of theTC basins. © 2019 American Meteorological Society."
"6603822174;35733801500;36088682200;57194348549;57191438775;6603218312;57191927388;56205720600;24759360700;","Multiscale Global Atmosphere Model SL-AV: the Results of Medium-range Weather Forecasts",2018,"10.3103/S1068373918110080","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058952221&doi=10.3103%2fS1068373918110080&partnerID=40&md5=9fb23ee2feada073aedf148ee3475bce","Development of the multiscale version of the global atmosphere model SL-AV required many improvements in the dynamical core, replacement or refinement of parameterization algorithms and complex tuning of the model. These modifications were initially tested with the experiments on modern climate simulation and then incorporated into the model configuration for medium-range numerical weather prediction. The impact of these model improvements on forecast quality is studied in this paper. The increase in accuracy of model climate characteristics has led to the reduction of forecast errors. The comparison of quality for numerical forecasts starting from the initial data of Hydrometcenter of Russia and ECMWF is carried out. The effect of replacing the initial data turned out to be comparable to the effect of multi-year works on model development. This shows the importance and necessity of development and improvement of the Hydrometcenter of Russia data assimilation system. © 2018, Allerton Press, Inc."
"13408723100;56861493000;55703584600;7402095113;","Three-pattern decomposition of global atmospheric circulation: part II—dynamical equations of horizontal, meridional and zonal circulations",2018,"10.1007/s00382-017-3763-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85021118253&doi=10.1007%2fs00382-017-3763-1&partnerID=40&md5=d9e97cd00368f9ba99aa69d8277a4d7c","The three-pattern decomposition of global atmospheric circulation (TPDGAC) partitions three-dimensional (3D) atmospheric circulation into horizontal, meridional and zonal components to study the 3D structures of global atmospheric circulation. This paper incorporates the three-pattern decomposition model (TPDM) into primitive equations of atmospheric dynamics and establishes a new set of dynamical equations of the horizontal, meridional and zonal circulations in which the operator properties are studied and energy conservation laws are preserved, as in the primitive equations. The physical significance of the newly established equations is demonstrated. Our findings reveal that the new equations are essentially the 3D vorticity equations of atmosphere and that the time evolution rules of the horizontal, meridional and zonal circulations can be described from the perspective of 3D vorticity evolution. The new set of dynamical equations includes decomposed expressions that can be used to explore the source terms of large-scale atmospheric circulation variations. A simplified model is presented to demonstrate the potential applications of the new equations for studying the dynamics of the Rossby, Hadley and Walker circulations. The model shows that the horizontal air temperature anomaly gradient (ATAG) induces changes in meridional and zonal circulations and promotes the baroclinic evolution of the horizontal circulation. The simplified model also indicates that the absolute vorticity of the horizontal circulation is not conserved, and its changes can be described by changes in the vertical vorticities of the meridional and zonal circulations. Moreover, the thermodynamic equation shows that the induced meridional and zonal circulations and advection transport by the horizontal circulation in turn cause a redistribution of the air temperature. The simplified model reveals the fundamental rules between the evolution of the air temperature and the horizontal, meridional and zonal components of global atmospheric circulation. © 2017, Springer-Verlag GmbH Germany."
"56535542600;57092710300;7103282616;31067496800;56520921400;","An intercomparison of GCM and RCM dynamical downscaling for characterizing the hydroclimatology of California and Nevada",2018,"10.1175/JHM-D-17-0181.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055051848&doi=10.1175%2fJHM-D-17-0181.1&partnerID=40&md5=a18f69e4574bb14f7ab88d063f84db21","Dynamical downscaling is a widely used technique to properly capture regional surface heterogeneities that shape the local hydroclimatology. However, in the context of dynamical downscaling, the impacts on simulation fidelity have not been comprehensively evaluated across many user-specified factors, including the refinements of model horizontal resolution, large-scale forcing datasets, and dynamical cores. Two global-to-regional downscaling methods are used to assess these: specifically, the variable-resolution Community Earth System Model (VR-CESM) and the Weather Research and Forecasting (WRF) Model with horizontal resolutions of 28, 14, and 7 km. The modeling strategies are assessed by comparing the VR-CESM and WRF simulations with consistent physical parameterizations and grid domains. Two groups of WRF Models are driven by either the NCEP reanalysis dataset (WRF_NCEP) or VR-CESM7 results (WRF_VRCESM) to evaluate the effects of large-scale forcing datasets. The simulated hydroclimatologies are compared with reference datasets for key properties including total precipitation, snow cover, snow water equivalent (SWE), and surface temperature. The large-scale forcing datasets are critical to the WRF simulations of total precipitation but not surface temperature, controlled by the wind field and atmospheric moisture transport at the ocean boundary. No significant benefit is found in the regional average simulated hydroclimatology by increasing horizontal resolution refinement from 28 to 7 km, probably due to the systematic biases from the diagnostic treatment of rainfall and snowfall in the microphysics scheme. The choice of dynamical core has little impact on total precipitation but significantly determines simulated surface temperature, which is affected by the snow-albedo feedback in winter and soil moisture estimations in summer. © 2018 American Meteorological Society."
"56517778400;36017183900;55706080300;7401945370;35329672300;55360542200;8067118800;56959736200;","Impact of lateral boundary errors on the simulation of clouds with a nonhydrostatic regional climate model",2017,"10.1175/MWR-D-17-0158.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040441733&doi=10.1175%2fMWR-D-17-0158.1&partnerID=40&md5=aa853a8d22d7e0d342db69affbf120e9","A nonhydrostatic, regional climate limited-area model (LAM) was used to analyze lateral boundary condition (LBC) errors and their influence on the uncertainties of regional models. Simulations using the fully compressible nonhydrostatic LAM (D-NICAM) were compared against the corresponding global quasi-uniform-grid Nonhydrostatic Icosahedral Atmospheric Model (NICAM) and a stretched-grid counterpart (S-NICAM). By this approach of sharing the same dynamical core and physical schemes, possible causes of model bias and LBC errors are isolated. The simulations were performed for a 395-day period from March 2011 through March 2012 with horizontal grid intervals of 14, 28, and 56 km in the region of interest. The resulting temporal mean statistics of the temperatures at 500 hPa were generally well correlated between the global and regional simulations, indicating that LBC errors had a minor impact on the large-scale flows. However, the time-varying statistics of the surface precipitation showed that the LBC errors lead to the unpredictability of convective precipitation, which affected the mean statistics of the precipitation distributions but induced only minor influences on the large-scale systems. Specifically, extratropical cyclones and orographic precipitation are not severely affected. It was concluded that the errors of the precipitation distribution are not due to the difference of the model configurations but rather to the uncertainty of the system itself. This study suggests that applications of ensemble runs, internal nudging, or simulations with longer time scales are needed to obtain more statistically significant results of the precipitation distribution in regional climate models. © 2017 American Meteorological Society."
"57208455668;11939929300;57192468922;55802056700;56256258400;","Colliding Modons: A Nonlinear Test for the Evaluation of Global Dynamical Cores",2017,"10.1002/2017MS000965","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85039049747&doi=10.1002%2f2017MS000965&partnerID=40&md5=344b0044d204caebd942ef583fcb2e8e","The modon, a pair of counter-rotating vortices propelling one another along a straight line, is an idealization of some observed large-scale and small-scale atmospheric and oceanic processes (e.g., twin cyclones), providing a challenging nonlinear test for fluid-dynamics solvers (known as “dynamical cores”). We present an easy-to-setup test of colliding modons suitable for both shallow-water and three-dimensional dynamical cores on the sphere. Two pairs of idealized modons are configured to collide, exchange vortices, and depart in opposite directions, repeating indefinitely in the absence of ambient rotation. This test is applicable to both hydrostatic and nonhydrostatic dynamical cores and is particularly challenging for refined grids on the sphere, regardless of solution methodology, or vertical coordinate. We applied this test to three popular dynamical cores, used by three different general circulation models: the Spectral-Element (SE) core of the Community Atmosphere Model, the Geophysical Fluid Dynamics Laboratory (GFDL) spectral core, and the GFDL Finite-Volume Cubed-Sphere dynamical core (FV3). Tests with a locally refined grid and nonhydrostatic dynamics were also performed with FV3. All cores tested were able to capture the propagation, collision, and exchange of the modons, albeit the rate at which the modon was diffused varied between the three cores and showed a strong dependence on the strength of hyperdiffusion. © 2017. The Authors."
"55927861900;57191228033;57014016800;57190136413;7403558634;57191223500;","Evaluation of different versions of NCUM global model for simulation of track and intensity of tropical cyclones over Bay of Bengal",2017,"10.1016/j.dynatmoce.2017.04.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85017464002&doi=10.1016%2fj.dynatmoce.2017.04.001&partnerID=40&md5=57d6cd2263e1d575196f97553c268206","The global UK Met office Unified Model (UM) is currently operational at National Centre for Medium Range Weather Forecasting (NCMRWF), the global model named as NCUM. An inter-comparison of two different versions of NCUM has been carried out for simulating the track and intensity of Tropical Cyclones (TCs), which formed over the Bay of Bengal (BoB). For this purpose, two series of numerical experiments named as NCUM25 (New Dynamical core with NCUM N512 resolution) and NCUM17 (ENDGame core with NCUM N768 resolution and upgraded physics and data assimilation scheme) are carried out with seven different initial conditions (ICs) for two TCs. The results suggested that the location, intensity, and vertical structure of the TCs are reasonably well predicted by the NCUM17 over the NCUM25. The Direct Position Error (DPE) and landfall error of TCs are reduced in the NCUM17 in comparison to the NCUM25 for all initial conditions. The mean DPEs and intensity error are reduced by 21–41% and 18–21% in NCUM17 over NCUM25 in both the cases respectively. Improvements in mean landfall position errors are shown to range from 43 to 65% in the NCUM17 as compared to the NCUM25. The mean statistical skill scores for rainfall are considerably improved in NCUM17. © 2017 Elsevier B.V."
"56524037000;7102315560;","Dynamics of the perfect storms: La Niña and Australia’s extreme rainfall and floods of 1974 and 2011",2017,"10.1007/s00382-016-3312-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84992723819&doi=10.1007%2fs00382-016-3312-3&partnerID=40&md5=8f186edc3e4fa76d02f2a4d8d71f2593","An ensemble of general circulation model simulations and dynamical mode analyses of important weather systems contributing to Australia’s severe rainfall and flooding events, in January 1974 and January 2011, are described. Dispersion relation techniques have also been used to extract the leading weather systems in observations and general circulation model (GCM) simulations, including Kelvin waves and intraseasonal oscillations. We find that the severe rainfall and flooding events over northern Australia in January 1974 and January 2011 coincided with significant intraseasonal oscillation and Kelvin wave activity that constructively interfered on the critical days of very high rainfall. The CSIRO Mk3L spectral GCM has been used to simulate both events. Particular simulations from 1870 to 2011, forced by observed SSTs and increasing CO2, agree well with observations in both the timing and patterns of these disturbances. The growth and structures of the leading dynamical normal modes have also been determined within a two-level primitive equation instability model. Our results show explosively growing intraseasonal oscillations and atmospheric Kelvin waves convectively coupled in the Australian monsoonal region. Monsoon disturbances, associated blocking over the Tasman Sea, and tropical–extratropical interactions also significantly contributed to the heavy rainfall. Model simulations and analyses of the dynamical modes are consistent with the synoptic situation seen in observational data for both severe precipitation events, and provide a more complete description of the reasons for the extreme impact of both events. © 2016, Springer-Verlag Berlin Heidelberg."
"35300998400;6602356321;7005859152;7103313971;7003310695;6602085180;8527475000;","The role of rough topography in mediating impacts of bottom drag in eddying ocean circulation models",2017,"10.1175/JPO-D-16-0229.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027470128&doi=10.1175%2fJPO-D-16-0229.1&partnerID=40&md5=4562d4ad51408fc55590f08a17186723","Motivated by the substantial sensitivity of eddies in two-layer quasigeostrophic (QG) turbulence models to the strength of bottom drag, this study explores the sensitivity of eddies in more realistic ocean general circulation model (OGCM) simulations to bottom drag strength. The OGCM results are interpreted using previous results from horizontally homogeneous, two-layer, flat-bottom, f-plane, doubly periodic QG turbulence simulations and new results from two-layer, β-plane QG turbulence simulations run in a basin geometry with both flat and rough bottoms. Baroclinicity in all of the simulations varies greatly with drag strength, with weak drag corresponding to more barotropic flow and strong drag corresponding to more baroclinic flow. The sensitivity of the baroclinicity in the QG basin simulations to bottom drag is considerably reduced, however, when rough topography is used in lieu of a flat bottom. Rough topography reduces the sensitivity of the eddy kinetic energy amplitude and horizontal length scales in the QG basin simulations to bottom drag to an even greater degree. The OGCM simulation behavior is qualitatively similar to that in the QG rough-bottom basin simulations, in that baroclinicity is more sensitive to bottom drag strength than are eddy amplitudes or horizontal length scales. Rough topography therefore appears to mediate the sensitivity of eddies in models to the strength of bottom drag. The sensitivity of eddies to parameterized topographic internal lee wave drag, which has recently been introduced into some OGCMs, is also briefly discussed. Wave drag acts like a strong bottom drag in that it increases the baroclinicity of the flow, without strongly affecting eddy horizontal length scales. © 2017 American Meteorological Society."
"23090137200;7006069664;7102572692;","Development of tropical cyclone wind field for simulation of storm surge/sea surface height using numerical ocean model",2016,"10.1007/s40808-015-0067-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85023632776&doi=10.1007%2fs40808-015-0067-5&partnerID=40&md5=f113b40b0047573cf477270248cef87d","Coupled ocean-atmospheric phenomenon such as tropical cyclones (TC’s) is governed by geophysical fluid dynamics. TC associated strong wind stress transfer momentum energy to the ocean surface that acts as the prime mechanism in modulating the sea surface and in generating the storm surge. A primitive equation, Princeton ocean model (POM) with free surface, sigma (terrain-following) coordinates and realistic bottom topography is configured in Bay of Bengal (BoB) to simulate the storm surge/sea surface height (SSH) and surface currents during a super cyclone TC05B 1999. TC wind fields are developed by adopting a suitable formulation based on partial conservation of angular momentum. Modeled TC wind fields are superimposed with QuikSCAT Satellite/National Centre for Environmental Prediction (QSCAT/NCEP) blended ocean surface winds to drive the three-dimensional ocean model. Model simulated storm surge and SSH are compared with limited available surge estimates/observations and multi-satellite observed AVISO (Archive, Validation and Interpolation of Satellite Oceanography) SSH, respectively to evaluate its performance. © 2015, Springer International Publishing Switzerland."
"7404358451;55542200200;","A doubly blended model for multiscale atmospheric dynamics",2016,"10.1175/JAS-D-15-0323.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84962326937&doi=10.1175%2fJAS-D-15-0323.1&partnerID=40&md5=90d9e9a0921b94d06a7e4d8116261c79","The compressible flow equations for a moist, multicomponent fluid constitute the most comprehensive description of atmospheric dynamics used in meteorological practice. Yet, compressibility effects are often considered weak and acoustic waves outright unimportant in the atmosphere, except possibly for Lamb waves on very large scales. This has led to the development of ""soundproof"" models, which suppress sound waves entirely and provide good approximations for small-scale to mesoscale motions. Most global flow models are based instead on the hydrostatic primitive equations that only suppress vertically propagating acoustic modes and are applicable to relatively large-scale motions. Generalized models have been proposed that combine the advantages of the hydrostatic primitive and the soundproof equation sets. In this note, the authors reveal close relationships between the compressible, pseudoincompressible (soundproof), hydrostatic primitive, and the Arakawa and Konor unified model equations by introducing a continuous two-parameter (i.e., ""doubly blended"") family of models that defaults to either of these limiting cases for particular parameter constellations. © 2016 American Meteorological Society."
"57198906958;15765007300;7103282616;6507115777;7003489919;31067496800;","Analyzing the adaptive mesh refinement (AMR) characteristics of a high-order 2D cubed-sphere shallow-water model",2016,"10.1175/MWR-D-16-0197.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84996671275&doi=10.1175%2fMWR-D-16-0197.1&partnerID=40&md5=a3fae86c4f463ac70d756c3c36421f8e","Adaptive mesh refinement (AMR) is a technique that has been featured only sporadically in atmospheric science literature. This paper aims to demonstrate the utility of AMR for simulating atmospheric flows. Several test cases are implemented in a 2D shallow-water model on the sphere using the Chombo-AMR dynamical core. This high-order finite-volume model implements adaptive refinement in both space and time on a cubed-sphere grid using a mapped-multiblock mesh technique. The tests consist of the passive advection of a tracer around moving vortices, a steady-state geostrophic flow, an unsteady solid-body rotation, a gravity wave impinging on a mountain, and the interaction of binary vortices. Both static and dynamic refinements are analyzed to determine the strengths and weaknesses of AMR in both complex flows with small-scale features and large-scale smooth flows. The different test cases required different AMR criteria, such as vorticity or height-gradient based thresholds, in order to achieve the best accuracy for cost. The simulations show that the model can accurately resolve key local features without requiring global high-resolution grids. The adaptive grids are able to track features of interest reliably without inducing noise or visible distortions at the coarse-fine interfaces. Furthermore, the AMR grids keep any degradations of the large-scale smooth flows to a minimum. © 2016 American Meteorological Society."
"35570389600;8724963200;54416512600;56428830000;6506539438;","IGCM4: A fast, parallel and flexible intermediate climate model",2015,"10.5194/gmd-8-1157-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84928753040&doi=10.5194%2fgmd-8-1157-2015&partnerID=40&md5=2527afab8e23162e8ea3b3da0b6c7c28","The IGCM4 (Intermediate Global Circulation Model version 4) is a global spectral primitive equation climate model whose predecessors have extensively been used in areas such as climate research, process modelling and atmospheric dynamics. The IGCM4's niche and utility lies in its speed and flexibility allied with the complexity of a primitive equation climate model. Moist processes such as clouds, evaporation, atmospheric radiation and soil moisture are simulated in the model, though in a simplified manner compared to state-of-the-art global circulation models (GCMs). IGCM4 is a parallelised model, enabling both very long integrations to be conducted and the effects of higher resolutions to be explored. It has also undergone changes such as alterations to the cloud and surface processes and the addition of gravity wave drag. These changes have resulted in a significant improvement to the IGCM's representation of the mean climate as well as its representation of stratospheric processes such as sudden stratospheric warmings. The IGCM4's physical changes and climatology are described in this paper. © 2015 Author(s). CC Attribution 3.0 License."
"36961431600;7004093651;42662276700;26323138400;","A semi-implicit version of the MPAS-atmosphere dynamical core",2015,"10.1175/MWR-D-15-0059.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945157078&doi=10.1175%2fMWR-D-15-0059.1&partnerID=40&md5=a70d84ac60c235794d4978c275f9dc6b","An important question for atmospheric modeling is the viability of semi-implicit time integration schemes on massively parallel computing architectures. Semi-implicit schemes can provide increased stability and accuracy. However, they require the solution of an elliptic problem at each time step, creating concerns about their parallel efficiency and scalability. Here, a semi-implicit (SI) version of the Model for Prediction Across Scales (MPAS) is developed and compared with the original model version, which uses a split Runge-Kutta (SRK3) time integration scheme. The SI scheme is based on a quasi-Newton iteration toward a Crank-Nicolson scheme. Each Newton iteration requires the solution of a Helmholtz problem; here, the Helmholtz problem is derived, and its solution using a geometric multigrid method is described. On two standard test cases, a midlatitude baroclinic wave and a small-planet nonhydrostatic gravity wave, the SI and SRK3 versions produce almost identical results. On the baroclinic wave test, the SI version can use somewhat larger time steps (about 60%) than the SRK3 version before losing stability. The SI version costs 10%-20% more per step than the SRK3 version, and the weak and strong scalability characteristics of the two versions are very similar for the processor configurations the authors have been able to test (up to 1920 processors). Because of the spatial discretization of the pressure gradient in the lowest model layer, the SI version becomes unstable in the presence of realistic orography. Some further work will be needed to demonstrate the viability of the SI scheme in this case. © 2015 American Meteorological Society."
"7402739568;7202885713;","The stratospheric wintertime response to applied extratropical torques and its relationship with the annular mode",2015,"10.1007/s00382-014-2359-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925541023&doi=10.1007%2fs00382-014-2359-2&partnerID=40&md5=111900aeaea5c4cca7b94b8872190ade","The response of the wintertime Northern Hemisphere (NH) stratosphere to applied extratropical zonally symmetric zonal torques, simulated by a primitive equation model of the middle atmosphere, is presented. This is relevant to understanding the effect of gravity wave drag (GWD) in models and the influence of natural forcings such as the quasi-biennial oscillation (QBO), El Ninõ-Southern Oscillation (ENSO), solar cycle and volcanic eruptions on the polar vortex. There is a strong feedback due to planetary waves, which approximately cancels the direct effect of the torque on the zonal acceleration in the steady state and leads to an EP flux convergence response above the torque’s location. The residual circulation response is very different to that predicted assuming wave feedbacks are negligible. The results are consistent with the predictions of ray theory, with applied westerly torques increasing the meridional potential vorticity gradient, thus encouraging greater upward planetary wave propagation into the stratosphere. The steady state circulation response to torques applied at high latitudes closely resembles the Northern annular mode (NAM) in perpetual January simulations. This behaviour is analogous to that shown by the Lorenz system and tropospheric models. Imposed westerly high-latitude torques lead counter-intuitively to an easterly zonal mean zonal wind (Formula Presented.) response at high latitudes, due to the wave feedbacks. However, in simulations with a seasonal cycle, the feedbacks are qualitatively similar but weaker, and the long-term response is less NAM-like and no longer easterly at high latitudes. This is consistent with ray theory and differences in climatological (Formula Presented.) between the two types of simulations. The response to a tropospheric wave forcing perturbation is also NAM-like. These results suggest that dynamical feedbacks tend to make the long-term NH extratropical stratospheric response to arbitrary external forcings NAM-like, but only if the feedbacks are sufficiently strong. This may explain why the observed polar vortex responses to natural forcings such as the QBO and ENSO are NAM-like. The results imply that wave feedbacks must be understood and accurately modelled in order to understand and predict the influence of GWD and other external forcings on the polar vortex, and that biases in a model’s climatology will cause biases in these feedbacks. © 2014, The Author(s)."
"57212026560;57212023632;57212025648;23768265300;57212025878;","Sensitivity of Precipitation in Aqua-Planet Experiments with an AGCM",2014,"10.3878/j.issn.1674-2834.13.0033","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075735986&doi=10.3878%2fj.issn.1674-2834.13.0033&partnerID=40&md5=d4d1c5b98add90ab69e6777899484800","The sensitivity of precipitation was studied by conducting control aqua-planet experiments (APEs) with a model to determine atmospheric general circulation. The model includes two versions: that with a spectral dynamical core (SAMIL) and that with a finite-volume dynamical core (FAMIL). Three factors were investigated including dynamical core, time-step length, and horizontal resolution. Numerical results show that the dynamical core significantly affects the structure of zonal averaged precipitation. FAMIL exhibited an equatorial precipitation belt with a single narrow peak, and SAMIL showed a broader belt with double peaks. Moreover, the time step of the model physics is shown to affect the zonal-averaged tropical convective precipitation ratio such that a longer time step leads to more production and consumption of convective available potential energy and convection initiated away from the equator, which corresponds to equatorial double peaks of precipitation. Further, precipitation is determined to be sensitive to horizontal resolution such that higher horizontal resolution allows for more small-scale kinetic energy to be resolved and leads to a broader probability distribution of low-level vertical velocity. This process results in heavier rainfall and convective precipitation extremes in the tropics. © 2014, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"7004978125;6507400558;54585176800;","Effects of rotation and mid-troposphere moisture on organized convection and convectively coupled gravity waves",2014,"10.1007/s00382-014-2222-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84939890232&doi=10.1007%2fs00382-014-2222-5&partnerID=40&md5=f3f7446413bba9c929beb08c67a361e6","Atmospheric convection has the striking capability to organize itself into a hierarchy of cloud clusters and super-clusters on scales ranging from the convective cell of a few kilometres to planetary scale disturbances such as the Madden–Julian oscillation. It is widely accepted that this phenomenon is due in large part to the two-way coupling between convective processes and equatorially trapped waves and planetary scale flows in general. However, the physical mechanisms responsible for this multiscale organization and the associated across-scale interactions are poorly understood. The two main peculiarities of the tropics are the vanishing of the Coriolis force at the equator and the abundance of mid-level moisture. Here we test the effect of these two physical properties on the organization of convection and its interaction with gravity waves in a simplified primitive equation model for flows parallel to the equator. Convection is represented by deterministic as well as stochastic multicloud models that are known to represent organized convection and convectively coupled waves quite well. It is found here that both planetary rotation and mid-troposphere moisture are important players in the diminishing of organized convection and convectively coupled gravity wave activity in the subtropics and mid-latitudes. The meridional mean circulation increases with latitude while the mean zonal circulation is much shallower and is dominated by mid-level jets, reminiscent of a second baroclinic mode circulation associated with a congestus mode instability in the model. This is consistent with the observed shallow Hadley and Walker circulations accompanied by congestus cloud decks in the higher latitude tropics and sub-tropics. Moreover, deep convection activity in the stochastic model simulations becomes very patchy and unorganized as the computational domain is pushed towards the subtropics and mid-latitudes. This is consistent with previous work based on cloud resolving modeling simulations on smaller domains. © 2014, Springer-Verlag Berlin Heidelberg."
"24451556500;7005087624;","An object-based approach for quantification of GCM biases of the simulation of orographic precipitation. Part I: Idealized simulations",2014,"10.1175/JCLI-D-14-00051.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84919741160&doi=10.1175%2fJCLI-D-14-00051.1&partnerID=40&md5=a69bde0ab51040dcb36ecf4c961b8b77","An object-based evaluation method to quantify biases of general circulation models (GCMs) is introduced using the National Center of Atmospheric Research (NCAR) Community Atmosphere Model (CAM). Idealized experiments with different topography are designed to reproduce the spatial characteristics of precipitation biases that were present in Atmospheric Model Intercomparison Project simulations using the CAMfinite volume (FV) andCAMEulerian spectral dynamical cores. Precipitation features are identified as ""objects"" to understand the causes of the differences between CAM FV and CAM Eulerian spectral dynamical cores. Three different mechanisms of precipitation were simulated in idealized experiments: stable upslope ascent, local surface fluxes, and resolved downstream waves. The results indicated stronger sensitivity of theCAMEulerian spectral dynamical core to resolution. The application of spectral filtering to topography is shown to have a large effect on the CAM Eulerian spectral model simulation. The removal of filtering improved the results when the scales of the topography were resolvable. However, it reduced the simulation capability of the CAM Eulerian spectral dynamical core because of Gibbs oscillations, leading to unusable results. A clear perspective about models biases is provided from the quantitative evaluation of objects extracted from these simulations and will be further discussed in part II of this study. © 2014 American Meteorological Society."
"7201554561;7004468723;24511929800;","Extratropical summertime response to tropical interannual variability in an idealized GCM",2013,"10.1175/JCLI-D-12-00461.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884258352&doi=10.1175%2fJCLI-D-12-00461.1&partnerID=40&md5=efed2a77bf7350b60f0ca54fd93f5ba8","A primitive equation model is used to investigate the role of the tropics in generating seasonal-mean anomalies in the extratropics. A nudging technique is applied to guide selected tropical regions toward 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and the National Centers for Environmental Prediction (NCEP)/Department of Energy Reanalysis (NCEP-2). The timeindependent linear response to these tropical anomalies is calculated for extratropical basic states taken from reanalysis climatologies and also from the climatological states of Action de Recherche Petite Echelle Grande Echelle (ARPEGE) and Laboratoire de Météorologie Dynamique (LMDZ) general circulation model simulations. For summer case studies, time-independent linear solutions show that some seasonal anomalies can be attributed to linear wave propagation from the tropics, especially for lower extratropical latitudes. If nudging is applied to the anomaly part of the tropical flow, the linear response shows little dependence on the basic state. Regional tropical nudging experiments display a global extratropical response. The persistent European summer anomaly in 2003 is partly attributable to a linear response to both Central American and West African monsoon circulations. The African region also triggers a wave train along the Asian subtropical jet. The model is then used in ""simple GCM"" mode to obtain extratropical responses that include a contribution from transient eddies. Tropical nudging improves the simple GCM's stationary wave climatology, and transient eddy forcing can produce substantial seasonal anomalies at high latitudes with better correspondence to some observed cases, especially in the Western Hemisphere, with stronger communication between the Asian monsoon and North America. © 2013 American Meteorological Society."
"55836373400;7405763496;34881832200;7102495827;","A double fourier series (DFS) dynamical core in a global atmospheric model with full physics",2013,"10.1175/MWR-D-12-00270.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882612828&doi=10.1175%2fMWR-D-12-00270.1&partnerID=40&md5=97cd8d669c434f4feea4ea0325890361","This study describes an application of the double Fourier series (DFS) spectral method developed by Cheong as an alternative dynamical option in a model system that was ported into the Global/Regional Integrated Model System(GRIMs).Amessage passing interface (MPI) for amassive parallel-processor cluster computer devised for the DFS dynamical core is also presented. The new dynamical core with full physics was evaluated against a conventional spherical harmonics (SPH) dynamical core in terms of short-range forecast capability for a heavy rainfall event and seasonal simulation framework.Comparison of the two dynamical cores demonstrates that the new DFS dynamical core exhibits performance comparable to the SPH in terms of simulated climatology accuracy and the forecast of a heavy rainfall event. Most importantly, theDFS algorithm guarantees improved computational efficiency in the cluster computer as the model resolution increases, which is consistent with theoretical values computed from a dry primitive equation model framework. The current study shows that, at higher resolutions, theDFS approach can be a competitive dynamical core because theDFS algorithm provides the advantages of both the spectral method for high numerical accuracy and the gridpoint method for high performance computing in the aspect of computational cost."
"34881832200;7405763496;","Double Fourier series dynamical core with hybrid sigma-pressure vertical coordinate",2013,"10.3402/tellusa.v65i0.19851","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882698871&doi=10.3402%2ftellusa.v65i0.19851&partnerID=40&md5=7446a2a68be8f2509f5928fed78dfa87","The hybrid sigma-pressure vertical coordinate is implemented into the double Fourier series (DFS) dynamical core of the Global/Regional Integrated Model system (GRIMs). Using traditional verification metrics, the model is quantitatively compared to a model that uses the terrain-following sigma coordinate. The distribution and skill scores for precipitation simulated with the hybrid coordinate are not significantly different from those found using the sigma coordinate. The hybrid coordinate has a positive effect on medium-range forecast skill in terms of geopotential height and temperature, especially in the tropics and upper layers of the atmosphere. Furthermore, the root-mean-squared error for relative humidity is significantly reduced near 100 hPa in the Northern (Southern) Hemisphere for a boreal summer (winter). The effect of the hybrid coordinate is found to be almost the same in the GRIMs-spherical harmonics (SPH) dynamical core. For the GRIMs-DFS dynamical core, the hybrid coordinate is insensitive to the abrupt transition of diffusivity at approximately 100 hPa, where numerical diffusion errors occur with the sigma coordinate. This suggests that the hybrid coordinate is necessary for the unique horizontal diffusion method of the GRIMs-DFS dynamical core. © 2013 M.-S. Koo and S.-Y. Hong."
"51360903200;36077992900;","Tropical/extratropical forcing on wintertime variability of the extratropical temperature and circulation",2013,"10.1007/s00382-012-1367-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874309735&doi=10.1007%2fs00382-012-1367-3&partnerID=40&md5=cfe65fc6b2bba151ebabb5a7e42ec178","The secular trends and interannual variability of wintertime temperatures over northern extratropical lands and circulations over the northern hemisphere are examined using the NCEP/NCAR reanalysis from 1961 to 2010. A primitive equation dry atmospheric model, driven by time-averaged forcing in each winter diagnosed from the NCEP reanalysis, is then employed to investigate the influences of tropical and extratropical forcing on the temperature and circulation variability. The model has no topography and the forcing is thus model specific. The dynamic and thermodynamic maintenances of the circulation and temperature anomalies are also diagnosed. Distinct surface temperature trends over 1961-1990 and 1991-2010 are found over most of the extratropical lands. The trend is stronger in the last two decades than that before 1990, particularly over eastern Canadian Arctic, Greenland, and Asia. The exchange of midlatitude and polar air supports the temperature trends. Both the diagnosed extratropical and tropical forcings contribute to the temperature and circulation trends over 1961-1990, while the extratropical forcing dominates tropical forcing for the trends over 1991-2010. The contribution of the tropical forcing to the trends is sensitive to the period considered. The temperature and circulation responses to the diagnosed tropical and extratropical forcings are approximately additive and partially offsetting. Covariances between the interannual surface temperature and 500-hPa geopotential anomalies for the NCEP reanalysis from 1961 to 2010 are dominated by two leading modes associated with the North Atlantic Oscillation (NAO) and Pacific-North American (PNA) teleconnection patterns. The diagnosed extratropical forcing accounts for a significant part of the NAO and PNA associated variability, including the interannual variability of stationary wave anomalies, as well as dynamically and thermodynamically synoptic eddy feedbacks over the North Atlantic and North Pacific. The tropical forcing contributes to the PNA related temperature and circulation variability, but has a small contribution to the NAO associated variability. Additionally, relative contributions of tropical Indian and Pacific forcings are also assessed. © 2012 Her Majesty the queen in the Right of Canada as represented by the Minister of the Environment."
"52263850600;15765007300;36154754400;7005087624;","Assessing tracer transport algorithms and the impact of vertical resolution in a finite-volume dynamical core",2012,"10.1175/MWR-D-11-00150.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864957857&doi=10.1175%2fMWR-D-11-00150.1&partnerID=40&md5=b2579c5fe14513d95306fee275c00295","Modeling the transport of trace gases is an essential part of any atmospheric model. The tracer transport scheme in the Community Atmosphere Model finite-volume dynamical core (CAM-FV), which is part of the National Center for Atmospheric Research's (NCAR's) Community Earth System Model (CESM1), is investigated using multidimensional idealized advection tests. CAM-FV's tracer transport algorithm makes use of one-dimensional monotonic limiters. The Colella-Sekora limiter, which is applied to increase accuracy where the data are smooth, is implemented into the CAM-FV framework, and compared with the more traditional monotonic limiter of the piecewise parabolic method (the default limiter). For 2D flow, CAM-FV splits dimensions, allowing overshoots and undershoots, with the Colella-Sekora limiter producing larger overshoots than the default limiter. The impact of vertical resolution is also explored. A vertical Lagrangian coordinate is used in CAM-FV, and is periodically remapped back to a fixed Eulerian grid. For purely vertical motion, it is found that lessfrequent remapping of the Lagrangian coordinate in CAM-FV improves results. For full 3D tests, the vertical component of the tracer transport dominates the error and limits the overall accuracy. If the vertical resolution is inadequate, increasing the horizontal resolution has almost no effect on accuracy. This is because the vertical resolution currently used in CAM version 5 may not be sufficiently fine enough to resolve some atmospheric tracers and provide accurate vertical advection. Idealized tests using tracers in a gravity wave agree with these results. © 2012 American Meteorological Society."
"56057021000;","An explicit time-difference scheme with an Adams-Bashforth predictor and a trapezoidal corrector",2012,"10.1175/MWR-D-10-05066.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84855771912&doi=10.1175%2fMWR-D-10-05066.1&partnerID=40&md5=bfcaccb2736cebf898415e250b7cc1ba","A new predictor-corrector time-difference scheme that employs a second-order Adams-Bashforth scheme for the predictor and a trapezoidal scheme for the corrector is introduced. The von Neumann stability properties of the proposed Adams-Bashforth trapezoidal scheme are determined for the oscillation and friction equations. Effectiveness of the scheme is demonstrated through a number of time integrations using finite-difference numerical models of varying complexities in one and two spatial dimensions. The proposed scheme has useful implications for the fully implicit schemes currently employed in some semi-Lagrangian models of the atmosphere. © 2012 American Meteorological Society."
"7007039835;","A multiconserving discretization with enthalpy as a thermodynamic prognostic variable in generalized hybrid vertical coordinates for the NCEP global forecast system",2011,"10.1175/2010MWR3295.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79958736421&doi=10.1175%2f2010MWR3295.1&partnerID=40&md5=379690ef29ce87431a51d46aedffa3f2","A new vertical discretization used in the atmospheric dynamics of the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) is illustrated, with enthalpy as the thermodynamic prognostic variable to reduce computation in thermodynamic equations while concerning all gas tracers in the model. Mass, energy, entropy, and angular momentum conservations are utilized as constraints to discretize the vertical integration with a finite-difference scheme. A specific definition of a generalized hybrid vertical coordinate, including sigma, isobaric, and isentropic surfaces, is introduced to define pressure at the model levels. Vertical fluxes are obtained by the equation of local changes in variables defined for vertical coordinates at all model layers. The forward-weighting semi-implicit time scheme is utilized to eliminate computational noise for stable integration. Because of time splitting between the dynamic and physics processes, the vertical advection is required both in the model dynamics and model physics, and the semi-implicit time scheme is used both in dynamics and after physics computation. Three configurations-sigma, sigma pressure, and sigma entropy-from the specific hybrid vertical coordinates with layer definition similar to NCEP operational GFS have been implemented in the NCEP GFS. Results from the sigma-isentropic coordinate show the largest anomaly correlation and the smallest root-mean-square error in tropical wind among all results at all layers, especially the upper layers. The scores from a period of daily forecast up to 5 days with the sigma-isentropic coordinate show the same level of skill as compared to the NCEP operational GFS. The results from the hurricane tracks for the fall of 2005 with sigma-isentropic coordinates show better scores compared with the operational GFS. © 2011 American Meteorological Society."
"7004183097;25960444600;6504060153;6504384499;","Low-level wind field climatology over the La Plata River region obtained with a mesoscale atmospheric boundary layer model forced with local weather observations",2010,"10.1175/2010JAMC2370.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955520427&doi=10.1175%2f2010JAMC2370.1&partnerID=40&md5=2481f41971484aeba118e63f2b7b41c2","A primitive equation, dry, hydrostatic, and incompressible mesoscale boundary layer model is used to simulate the high-horizontal-resolution low-level wind field ""climatology"" over the La Plata River region in South America. The horizontal model domain has 79 × 58 points (350 km × 316 km), with a horizontal resolution of 0.05°. The model climatological field is the ensemble result of a series of daily forecasts obtained by forcing the model with limited local observations. Each ensemble member produces a daily forecast that participates in the definition of the wind climatology with a probability calculated with the local observations. The upper boundary condition is taken from the only local radiosonde observation, and the lower boundary condition consists of a surface heating function calculated with the temperature observations of the surface weather stations in the region. The study, conducted during the period of 1959-84, reveals an overall good agreement between the observed and the modeled surface wind climatological fields at five weather stations in the region. The model represents very well the differences in the wind speed magnitudes and predominant wind direction sectors throughout a region that displays a strong sea-land-breeze daily cycle. The average root-mean-square value of the model relative error is 31% for wind direction and 23% for wind speed. Model errors vary throughout the day with the minimum in the morning and afternoon and the maximum at night. The seasonal climatology shows the minimum wind direction error in winter and the maximum error in summer, whereas the wind speed errors reveal no seasonality. The annual wind direction error is very similar to the winter minimum error. The conclusion of the study is that the proposed ensemble mean method is useful for synthesizing high-resolution climatological low-level wind fields over regions with a strong diurnal cycle of surface thermal contrasts and a limited number of available weather stations. © 2010 American Meteorological Society."
"9250477900;7201439545;","A semi-geostrophic model incorporating well-mixed boundary layers",2010,"10.1002/qj.612","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77954461628&doi=10.1002%2fqj.612&partnerID=40&md5=695bdc050d67865c0bbef5ed2036a41d","Semi-geostrophic theory has proved a powerful framework for understanding the dynamics of mid-latitude weather systems. However, one limitation is the lack of a realistic boundary-layer representation. Semi-geostrophic theory can be modified to include an atmospheric boundary layer by replacing the geostrophic wind with the 'geotriptic' (or Ekman-balanced) value in the substantive derivative and appropriately approximating the momentum diffusion term-the so-called semi-geotriptic theory. However, until now, solutions of the semi-geotriptic equations using predictor-corrector methods have not been possible for the important case of well-mixed boundary layers. Existing predictor-corrector methods require a Brunt-Vaisala frequency greater than zero to be solvable. Here we describe a method of incorporating well-mixed boundary layers into semi-geotriptic theory. We modify the hydrostatic relationship by including a small horizontal diffusion of vertical velocity. This enables the formation of a well-posed predictor-corrector method. Given well-mixed boundary layers are a ubiquitous feature of the lower atmosphere, the modification increases the usability of the model. Calculations are also performed at much higher vertical resolution than before. The revised semi-geotriptic model is compared with a hydrostatic primitive-equation model for a test case of a two-dimensional idealized diurnal cycle of a sea breeze. The performance of the revised semi-geotriptic model in the growth phase of the sea breeze is improved, as a well-mixed boundary layer is now permitted. The additional vertical resolution captures the capping inversion and the sea-breeze circulation better. The hydrostatic primitive-equation model is shown to produce inertial oscillations that persist beyond the evening decay of the boundary layer until the following morning. In contrast, the semi-geotriptic model decays following the boundary-layer state in a more realistic way. The semi-geotriptic model thus demonstrates its usefulness as a critical tool in understanding boundary-layer dynamics coupling issues in operational models. © 2010 Royal Meteorological Society and Crown Copyright."
"7102315560;7004010406;52464182600;","Seasonal ensemble prediction with a coupled ocean-atmosphere model",2010,"10.22499/2.5901.007","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80054970272&doi=10.22499%2f2.5901.007&partnerID=40&md5=37f2945c72455be6e38e48b044d6dfcd","Ensemble prediction methods, in which the control initial conditions are perturbed by coupled ocean-atmosphere non-linear instabilities obtained by a breeding method, have been applied within a coupled ocean-atmosphere model with prognostic primitive equation atmospheric and oceanic components. The bred vectors have a distinct annual cycle of growth rates with the maximum occurring during boreal winter and a minimum during boreal summer. Bred vector amplitudes peak in boreal spring and have a minimum in boreal autumn. The leading empirical orthogonal functions of the 50 m ocean temperature of bred vectors have maxima in the equatorial Pacific between 120-150°W, as well as in the western Pacific, while the associated 500 hPa streamfunction fields have large-scale wave-trains in extratropical regions that are strongly influenced by ENSO. Coupled control and ensemble forecasts for one year have been initiated on the first day of each month during a period in the 1990s to examine the sensitivity of enhanced ensemble mean skill, compared with the control, on the number and type of ensemble perturbations. The focus has been on the skill of predicting the 50 m ocean temperature in the equatorial region. For forecasts longer than about two months the root mean square errors in the ensemble mean forecasts are smaller than for the control based on averages over all the forecasts. There is considerable variability in the skill of both control and ensemble forecasts during the 1990s. In particular, forecasts through the 1997 El Niño and 1998 La Niña regime transitions tend to be less skilful than in more quiescent periods. Forecast errors tend to increase with time as expected and there are peaks in error amplitudes for forecasts verifying in boreal spring. Forecast skill increases with increasing numbers of bred vectors but saturates with little additional gain in using 64 members compared with 32. Ensemble forecasts with cyclic mode perturbations, the non-linear generalisations of finite time normal modes, are found to be more skilful than bred vectors, with eight cyclic modes producing similar error reduction in three to nine-month forecasts as 32 to 64 bred vectors. Our results suggest that a contributing cause of the boreal spring predictability barrier is the fact that large-scale atmospheric teleconnection patterns and instabilities peak in boreal spring and in turn couple to the ocean."
"6701776710;","The frontogenetical forcing of secondary circulations. Part II: Properties of Q vectors in exact linear solutions",2009,"10.1175/2008JAS2803.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65549114593&doi=10.1175%2f2008JAS2803.1&partnerID=40&md5=1727ea5f7038c68487e8c25590536cb3","An exact solution of the primitive equations (PEs) and the corresponding exact solutions of the alternative balance (AB), geostrophic momentum (GM), and quasigeostrophic (QG) equations are presented. The PE solution illustrates how the temperature and horizontal vorticity fields evolve in a linear horizontal flow with constant deformation and vertical vorticity when the initial temperature field is also linear, as well as how ageostrophic circulations are produced. The other exact solutions show the errors produced by the various approximations and confirm that the AB solution is more accurate than the GM one and that the QG solution is almost always the most inexact. The utility of the Q vector and similar vectors is examined for each solution. The PE solution verifies that in a hyperbolic wind field (i) the isotherms eventually parallel the outflow axis, (ii) the ageostrophic circulation ultimately becomes normal to the outflow axis, (iii) thermal-wind balance becomes established in the direction normal to the isotherms, and (iv) the rotational component of the vector frontogenetical function decays. © 2009 American Meteorological Society."
"56318016000;55786890800;","On the existence of atmospheric attractors",2008,"10.1007/s11430-007-0103-z","https://www.scopus.com/inward/record.uri?eid=2-s2.0-40349114240&doi=10.1007%2fs11430-007-0103-z&partnerID=40&md5=c133edcc15f190eb69747643f01c3dad","In this paper, we consider the long-time dynamics for the primitive equations of large-scale dry atmosphere. First, by energy methods, we obtain the existence and uniqueness of global strong solutions of the problem. Second, by studying the long-time behavior of strong solutions, we construct a global attractor which captures all the trajectories. © Science in China Press 2008."
"35460698500;35477562700;","A study on the stability of a baroclinic flow in cyclostrophic balance on the sphere",2006,"10.1029/2006GL026200","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845657711&doi=10.1029%2f2006GL026200&partnerID=40&md5=7ceab24365e38003e72db3334cb714c6","A three-dimensional primitive equation model on a sphere is constructed to investigate stability of a baroclinic flow in cyclostrophic balance and structures of the unstable modes. When the Richardson number is large, the baroclinic instability appears for sufficiently small values of the Rossby number. As the Rossby number increases, only the large scale modes remain unstable and amplitude of these modes becomes confined to the lower layer. When the Richardson number is small, the symmetric instability 1 predominates, while the baroclinic instability modes also exist in a certain parameter range. Unlike the baroclinic instability mode, the amplitude of the symmetric instability mode is confined to low latitudes in the upper layer. Since the Richardson number is small in the Venus cloud layer, it is predicted that the baroclinic instability is suppressed in the midlatitudes, and the symmetric instability appears in the low latitudes. Copyright 2006 by the American Geophysical Union."
"23034217100;56206644300;8287002900;","FoSSI: The family of simplified solver interfaces for the rapid development of parallel numerical atmosphere and ocean models",2005,"10.1016/j.ocemod.2004.06.004","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14744283845&doi=10.1016%2fj.ocemod.2004.06.004&partnerID=40&md5=980a9bc3c155ec67affe98bd2d6ae921","The portable software FoSSI is introduced that - In combination with additional free solver software packages - Allows for an efficient and scalable parallel solution of large sparse linear equations systems arising in finite element model codes. FoSSI is intended to support rapid model code development, completely hiding the complexity of the underlying solver packages. In particular, the model developer need not be an expert in parallelization and is yet free to switch between different solver packages by simple modifications of the interface call. FoSSI offers an efficient and easy, yet flexible interface to several p arallel solvers, most of them available on the web, such as PETSC, AZTEC, MUMPS, PILUT and HYPRE. FoSSI makes use of the concept of handles for vectors, matrices, preconditioners and solvers, that is frequently used in solver libraries. Hence, FoSSI allows for a flexible treatment of several linear equations systems and associated preconditioners at the same time, even in parallel on separate MPI-communicators. The second special feature in FoSSI is the task specifier, being a combination of keywords, each configuring a certain phase in the solver setup. This enables the user to control a solver over one unique subroutine. Furthermore, FoSSI has rather similar features for all solvers, making a fast solver intercomparison or exchange an easy task. FoSSI is a community software, proven in an adaptive 2D-atmosphere model and a 3D-primitive equation ocean model, both formulated in finite elements. The present paper discusses perspectives of an OpenMP-impleme ntation of parallel iterative solvers based on domain decomposition methods. This approach to OpenMP solvers is rather attractive, as the code for domain-local operations of factorization, preconditioning and matrix-vector product can be readily taken from a sequential implementation that is also suitable to be used in an MPI-variant. Code development in this direction is in an advanced state under the name ScOPES: The Scalable Open Parallel sparse linear Equations Solver. © 2004 Elsevier Ltd. All rights reserved."
"6603435381;7006901882;24449910400;","Developing a dynamically based assimilation method for targeted and standard observations",2005,"10.5194/npg-12-149-2005","https://www.scopus.com/inward/record.uri?eid=2-s2.0-14944345965&doi=10.5194%2fnpg-12-149-2005&partnerID=40&md5=8464cd8ad4bd6dec1b382411db00c48e","In a recent study, a new method for assimilating observations has been proposed and applied to a small size nonlinear model. The assimilation is obtained by confining the analysis increment in the unstable subspace of the Observation-Analysis-Forecast (OAF) cycle system, in order to systematically eliminate the dynamically unstable components, present in the forecast error, which are responsible for error growth. Based on the same ideas, applications to more complex models and different, standard and adaptive, observation networks are in progress. Observing System Simulation Experiments (OSSE), performed with an atmospheric quasi-geostrophic model, with a restricted ""land"" area where vertical profiles are systematically observed, and a wider ""ocean"" area where a single supplementary observation is taken at each analysis time, are reviewed. The adaptive observation is assimilated either with the proposed method or, for comparison, with a 3-D VAR scheme. The performance of the dynamic assimilation is very good: a reduction of the error of almost an order of magnitude is obtained in the data void region. The same method is applied to a primitive equation ocean model, where ""satellite altimetry"" observations are assimilated. In this standard observational configuration, preliminary results show a less spectacular but significant improvement obtained by the introduction of the dynamical assimilation. European Geosciences Union © 2005 Authors(s). This work is licensed under a Creative Commons License."
"8750834400;7006421134;7005759537;","The lateral transport of zonal momentum due to Kelvin waves in a meridional circulation",2004,"10.1175/1520-0469(2004)061<1966:TLTOZM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4344580704&doi=10.1175%2f1520-0469%282004%29061%3c1966%3aTLTOZM%3e2.0.CO%3b2&partnerID=40&md5=c15fef3d9a12559362b84aaf8f10d50b","A modified, equatorial Kelvin wave solution is obtained in the presence of the zonal-mean meridional circulation. The modified Kelvin wave solution, which is obtained via a perturbation expansion of the linearized, primitive equations on an equatorial β plane, possesses a nonzero meridional wind component. This meridional wind component is absent when the background flow is at rest. The combination of the meridional and zonal winds induces a meridional flux of zonal momentum in the upstream direction of the background north-south flow. This flux is divergent in latitude and produces a nonzero wave-induced force even though the waves are linear, steady, and conservative. It is shown that, although such a force violates the traditional nonacceleration theorem in which the mean meridional circulation is negligible at leading order, the result is in accord with a more general nonacceleration theorem obtained from the exact generalized Lagrangian-mean theory in which the mean meridional circulation is nonzero. The meridional circulation, in effect, attempts to advect wave pseudomomentum off the equator, resulting in a nonzero acceleration in the Eulerian reference frame. The meridional flux of momentum for any equatorially trapped mode is derived from the generalized Lagrangian-mean theory. Those modes with eastward (westward) intrinsic phase velocity transport eastward (westward) zonal momentum in the upstream direction of the background meridional flow in the neighborhood of the equator. It is also shown that the vertical flux of zonal momentum is not constant with altitude in a steady vertical flow since diabatic heating/cooling is needed to sustain the vertical wind. Implications of the results for the terrestrial and Venusian atmospheres are discussed. © 2004 American Meteorological Society."
"7003893628;7004069241;","A problem with the Robert-Asselin time filter for three-time-level semi-implicit semi-lagrangian discretizations",2004,"10.1175/1520-0493(2004)132<0600:APWTRT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1542750992&doi=10.1175%2f1520-0493%282004%29132%3c0600%3aAPWTRT%3e2.0.CO%3b2&partnerID=40&md5=d678f72f5f44c9021e5a15f330e2e7d5","Three-time-level schemes for first-order differential equations are affected by the existence of computational modes. The Robert-Asselin filter was developed in an Eulerian context to selectively damp such modes while leaving the physical solution virtually untouched. Here previous analysis of this time filter for simple equation sets is extended to three-time-level semi-implicit semi-Lagrangian discretizations of the hydrostatic primitive equations. For Contain numbers greater than one-half, a surprising loss of selectivity is found when compared to that previously observed in the fully Eulerian context. Not only can the physical solution be undesirably more damped than the computational one, it can be significantly more damped. This problem is particularly serious in polar regions of a global gridpoint model due to the convergence of the meridians, although its severity might be reduced by using horizontal diffusion or spatial filtering to make the flow field more isotropic. (It is, however, no more serious there than elsewhere for a triangularly truncated spectral model because of its isotropic representation.) The problem's source is attributed to the current practice of integrating the equations along the trajectories but time filtering at grid points. Although time filtering along a trajectory would mitigate the problem, it would be costly in practice because of the additional computations required."
"7103321545;16312087900;36842329100;55619302013;35776608800;","Synoptic- and meso-α-scale variations of the Baiu front simulated in an AGCM",2003,"10.2151/jmsj.81.1387","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842634948&doi=10.2151%2fjmsj.81.1387&partnerID=40&md5=4b1b69687c2004a47788ba0dce2ca368","The present paper studies features of the Baiu front and associated precipitation systems simulated in the climatological SST run by an AGCM T106L52 (primitive equation spectral model, the maximum wave-number of 106, with 52 vertical levels) in comparison with the features found in observational studies. The Baiu front is properly simulated in 1-20 June Y07 (the 7th year after the spin-up integration). In this ""Baiu phase"", the large-scale circulation systems, such as the upper cold lows and blocking ridge in the northern latitudes, westward extending Pacific subtropical anticyclone, monsoon westerly, and subtropical jet stream, are simultaneously maintained. Under this condition, the synoptic- and meso-α-scale variations of the Baiu front are simulated. The southward shift of the front occurs when a synoptic-scale cyclone develops in association with a westerly trough. When westerly troughs are inactive, weak subsynoptic-scale depression is formed in the frontal zone. A few meso-α-scale precipitation systems are generated in the trailing portion of the preceding depression, and form a ""Baiu precipitation system family"" with a length of ∼2000 km. This indicates that the simulation of the realistic Baiu front depends on the maintenance of proper large- and synoptic-scale circulation systems. However, the Baiu precipitation zone disappears in the early July, as the west-east elongating barotropic anticyclone, which is usually seen over Japan in August in the real atmosphere, is situated over ∼37°N. © 2003, Meteorological Society of Japan."
"6701776280;7005720566;7005874502;7006595183;","Empirical normal mode diagnostic study of the GEM model's dynamical core",2002,"10.1175/1520-0469(2002)059<2498:ENMDSO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0037104131&doi=10.1175%2f1520-0469%282002%29059%3c2498%3aENMDSO%3e2.0.CO%3b2&partnerID=40&md5=a37e8d51907fc85f88517de388c2cf84","An algorithm based on the empirical normal mode analysis is used in a comparative study of the climatology and variability in dynamical-core experiments of the Global Environmental Multiscale model. The algorithm is proposed as a means to assess properties of the model's dynamical core and to establish objective criteria for model intercomparison studies. In this paper, the analysis is restricted to the upper troposphere and lower stratosphere. Two dynamical-core experiments are considered: one with the forcing proposed by Held and Suarez, later modified by Williamson et al. (called HSW experiment), and the other with a forcing inspired by the prescriptions of Boer and Denis (BD). Results are also compared with those of an earlier diagnosis of NCEP reanalysis. Normal modes and wave-activity spectra are similar to those found in the reanalysis data, although details depend on the forcing. For instance, wave-energy amplitudes are higher with the BD forcing, and an approximate energy equipartition is observed in the spectrum of wavenumber-1 modes in the NCEP data and the BD experiment but not in the HSW experiment. The HSW forcing has a relatively strong relaxation acting on the complete temperature field, whereas the BD forcing only acts on the zonal-mean temperature, letting the internal dynamics alone drive the wave-activity spectral cascade. This difference may explain why the BD forcing is more successful in reproducing the observed wave activity in the upper troposphere and lower stratosphere."
"6507033325;6603628691;6701603958;7003758326;57211197739;","Four-dimensional variational assimilation of SSM/I precipitable water content data",1998,"10.1256/smsqj.54917","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031734883&doi=10.1256%2fsmsqj.54917&partnerID=40&md5=98c28ec8351353887549d5d4edc5b242","Satellite microwave radiometers provide measurements of precipitable water content (PWC) over the oceans, with a horizontal resolution of a few tens of kilometres. These data represent the water vapour content integrated over the atmospheric column. We assess the value of this source of information for numerical weather prediction systems. We used the European Centre for Medium-Range Weather Forecasts Integrated Forecasting System with a four-dimensional variational method to assimulate the Special Sensor Microwave/Imager (SSM/I) PWC data over a 24-hour period. Our experiments use an incremental variational method. Comparison with observations is made using a multi-level global primitive-equation T106 spectral model with physical parametrizations. Minimization is performed using a T63 adiabatic dynamics model which includes only simplified physics (horizontal diffusion, a simple surface drag and a vertical diffusion scheme). Comparing the control and assimilation experiments with aircraft and other data shows that the use of PWC data from SSM/I improves the analysis. We also obtain a slight improvement in short-range forecasts of almost all parameters when SSM/I-PWC data are used in the assimilation."
"7801573573;8278450600;","Real-time predictions of surge propagation",1997,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031312376&partnerID=40&md5=3374fc5c014c0e440f79f6a580320e53","This paper describes the development and implementation of a procedure for forecasting the propagation of a hurricane surge. The approach requires the successive application of three components. The first is an interactive input interface in which the user obtains an updated marine advisory forecast from web site locations such as that of the National Hurricane Center. The known and projected locations of the storm are then used to define input to the second component of the procedure, a Planetary Boundary Layer (PBL) hurricane model. The PBL model employs the vertically-averaged primitive equations of motion for predicting hurricane-generated wind and atmospheric pressure fields which are computed at each node in a translating uniform grid and interpolates them onto the computational grid of the third component of the procedure, the depth-integrated finite element long-wave hydrodynamic ADvanced CIRCulation (ADCIRC) model. The PBL-based wind and pressure fields are input to the ADCIRC model to compute the propagating storm surge over the documented and projected track of the storm. Surface elevation and currents corresponding to the last known location of the hurricane eye are archived in 'hot start' files. Projected track information are then used to estimate surge propagation from the last known location of the eye. New simulations can then made for each updated forecast."
"7103180783;7102367341;","The effect of barotropic shear on baroclinic instability Part II: The initial value problem",1997,"10.1016/S0377-0265(96)00472-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030948915&doi=10.1016%2fS0377-0265%2896%2900472-1&partnerID=40&md5=61070ee99bc8da378186cdeb5e550de3","The effect of barotropic shear on baroclinic instability has been investigated using both a linear quasi-geostrophic β-plane channel model and a multilevel primitive equation model on the sphere when a nonmodal disturbance is used as the initial perturbation condition. The analysis of the initial value problem has demonstrated the existence of a rapid transient growth phase of the most unstable mode. The inclusion of a linear barotropic shear reduces initial rapid transient growth, although at intermediate times the transient growth rates of the sheared cases can be larger than in the unsheared case owing to downgradient eddy momentum fluxes. Certain disturbances can amplify by factors of 4.5-60 times (for the L2 norm), or 3-30 times (for the perturbation amplitude maximum), as large as disturbances based on the linear normal modes. However, linear horizontal shear always reduces the amplification factors. The mechanism is that the shear confines the disturbance meridionally and therefore limits the energy conversion from the zonal available potential energy to eddy energy. The effect of barotropic shear on the transient growth is not changed much in the presence of either thermal damping or Ekman pumping. Nonmodal integrations of baroclinic wave lifecycles show that the energy level reached by eddies is not very sensitive to the structure of the initial disturbance if the amplitude of the initial disturbance is small. Although in some cases the eddy kinetic energy level reached by the wave integrated from nonmodal disturbance can be 25-150% larger than the normal mode integrations, barotropic shear, characterized by large shear vorticity with small horizontal curvature, always reduces the eddy kinetic energy level reached by the wave, confirming the results of normal mode studies."
"7401559815;7405584618;57202302285;","Large scale dynamics associated with super cloud cluster organization over the tropical western pacific",1994,"10.2151/jmsj1965.72.4_481","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016865069&doi=10.2151%2fjmsj1965.72.4_481&partnerID=40&md5=9cfaee10262180e065d1bc82bb6ca0da","Using a nonlinear primitive equation model of the tropical atmosphere, we have studied the large scale dynamics associated with the organization of super-cloud clusters (SCC) and the effect of nonlinear mean flow interaction and lateral forcing on the evolution of SCC and the Madden and Julian Oscillation (MJO) over the tropical western Pacific. It is found that the nonlinear interaction between convection and the large scale circulation associated with the organization of SCC can excite a variety of symmetric divergent motions along the equator and rotational motions away from the equator. The former can be identified as eastward propagating moist Kelvin waves and westward propagating inertia-gravity waves and the latter as Rossby waves. The interaction between the SCC and a basic flow induced by a northern wintertime heat source distribution gives rise to quasi-stationary modes over the western Pacific which may be identified with mixed Rossby-gravity wave. Westerly vertical wind shear over the western Pacific modifies the vertical tilt of the MJO and favors its growth. During the northern winter, cold surges from the East Asian continent exert strong control on the development of SCC in the equatorial regions by inducing pressure differential across the maritime continent and the western Pacific, leading to enhancement of surface wind convergence. When the influence of the subsidence motion associated with a pre-existing SCC/MJO is weakened, the cold surge-induced pressure anomaly can lead to the development of new SCC with intermediate time scales. The time interval between intermediate SCCs is about 8-10 days which is approximately the transit time of the MJO across the span of the warm pool of the western Pacific. During the northern summer, the SCCs in the equatorial region are much less organized with mixed eastward and westward propagating signals. In the northern subtropics (15°N-20°N), westward propagating synoptic scale waves are found in regions with strong westerly shear. These waves grow by latent heating as well as by extracting wave energy from the mean westerly vertical shear in the lower troposphere. Overall, the results suggest that the organization and location of SCC and the associated multi-scale motions are strongly dependent on the evolving seasonal mean flow. © 1994, Meteorological Society of Japan."
"7409731826;","An air-sea interaction model for cold-air outbreaks",1992,"10.1175/1520-0485(1992)022<0821:aasimf>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027072603&doi=10.1175%2f1520-0485%281992%29022%3c0821%3aaasimf%3e2.0.co%3b2&partnerID=40&md5=b29d523e5312408b9fc094e1e54f51d5","A two-dimensional dry model for the atmosphere is coupled with a two-dimensional primitive equation model for the ocean to investigate how cold fronts interact with the Gulf Stream and its adjacent waters during cold-air outbreaks. The development of a cross-stream frontal circulation under the influence of the ocean surface heating and its impact on the ocean circulation are determined for various frontal and synoptic conditions. The diabatic heating under an offshore wind is shown to generate a convective boundary layer over the ocean, which deepens seaward. The interaction of the convective boundary layer and the seaward-moving cold front decreases the speed of the frontal propagation and induces a downdraft behind the front and an updraft near the nose of the front. -from Author"
"7101633281;","Simulations of cold surges over oceans with application to AMTEX '75.",1985,"10.1175/1520-0469(1985)042<0135:SOCSOO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022266210&doi=10.1175%2f1520-0469%281985%29042%3c0135%3aSOCSOO%3e2.0.CO%3b2&partnerID=40&md5=2ebde0697d3ebc388ed2aca6769ba288","Comparative numerical experiments and observational verifications for cold surges over the ocean are conducted using a primitive equation planetary boundary layer (PBL) model. A simulation of an intense cold air outbreak observed during the Air Mass Transformation Experiment, 1975 (AMTEX '75) is performed. Downwind variations of dynamic and thermodynamic PBL properties and cloud distribution and type are well reproduced. -from Author"
"57206313116;7202741460;","Axisymmetric, primitive equation, spectral tropical cyclone model. Part II: normal mode initialization.",1985,"10.1175/1520-0469(1985)042<1225:APESTC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022264260&doi=10.1175%2f1520-0469%281985%29042%3c1225%3aAPESTC%3e2.0.CO%3b2&partnerID=40&md5=f4ad23a137cfb600943c441de981e56d","The model is solved using a spectral method with normal mode basis functions. Results from a six-day tropical cyclone simulation are used as initial data to test the NNMI. It is shown that Machenhauer's NNMI scheme converges rapidly under tropical cyclone conditions when the dissipative and convective terms are not included in the nonlinear forcing (adiabatic initialization). When these terms are included (diabatic initialization), Machenhauer's scheme no longer converges, but can still reduce the initial gravity mode time tendencies to an acceptable level. -from Authors"
"7402093416;55924208000;","The importance of nonlinear wave processes in a quiescent winter stratosphere",1984,"10.1002/qj.49711046402","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84987059652&doi=10.1002%2fqj.49711046402&partnerID=40&md5=b11bd4af4bca8a78117130048d5e6815","Linear wave modelling about a zonally symmetric state is often assumed to be able to simulate accurately time‐averaged planetary wave geopotential heights in the stratosphere during quiescent winter periods. We test this linear assumption by using a time‐dependent three‐dimensional primitive equation model of the stratosphere and mesosphere to simulate the quiescent winter stratospheric circulation during December 1980. The results from this simulation, together with two other idealized integrations, indicate that nonlinear wave interactions were crucial in accounting for the observed monthly mean wavenumber‐1 planetary wave amplitude, particularly in the upper stratosphere. Our results suggest that, in general, such interactions cannot be ignored for quantitatively accurate simulations of the middle atmosphere. Copyright © 1984 Royal Meteorological Society"
"35330117400;6507993862;","Orthogonal vertical normal modes of a vertically staggered discretized atmospheric model.",1983,"10.1175/1520-0493(1983)111<1724:OVNMOA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020947493&doi=10.1175%2f1520-0493%281983%29111%3c1724%3aOVNMOA%3e2.0.CO%3b2&partnerID=40&md5=e64155993cabff6c9acafa043ebe8c3c","In the formulation of nonlinear normal mode initialization (NNMI), we apply the separation of variables to a primitive equation model which is linearized about a basic state at rest. This results in the vertical and horizontal structure equations from which normal mode functions are constructed as their solutions. This paper is concerned with the property of the vertical normal mode functions. -from Authors"
"6506337175;","A numerical simulation of an observed lake breeze over Southern Lake Ontario",1982,"10.1007/BF00121122","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0004956141&doi=10.1007%2fBF00121122&partnerID=40&md5=44da6217450d7ff26d7a74c8917023cc","A time-dependent, two-dimensional primitive-equation atmospheric boundary-layer model has been applied to the South shore of Lake Ontario, using data obtained by Estoque et al. (1976). The model has correctly predicted the times of onset, maximum intensity and disappearance of the lake breeze. However, it underestimated the maximum inland penetration of the lake breeze, probably due to the fact that horizontal variations of surface potential temperature over the land had not been taken into account. © 1982 D. Reidel Publishing Co."
"57212941289;","A transformed isentropic coordinate and its use in an atmospheric model.",1981,"10.1175/1520-0493(1981)109<2029:ATICAI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019653731&doi=10.1175%2f1520-0493%281981%29109%3c2029%3aATICAI%3e2.0.CO%3b2&partnerID=40&md5=88578a6f7a38ffd8e3b4352134016ba8","A primitive equation numerical model utilizing normalized potential temperature as the vertical coordinate is described. This coordinate system enables an easier approach to the treatment of the lower boundary condition in comparison to the ordinary potential temperature coordinate. For the case of a baroclinically unstable atmosphere, the model has been implemented successfully.-Author"
"6701807580;","Cyclone development along weak thermal fronts.",1979,"10.1175/1520-0469(1979)036<2049:CDAWTF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0018704804&doi=10.1175%2f1520-0469%281979%29036%3c2049%3aCDAWTF%3e2.0.CO%3b2&partnerID=40&md5=6ca131dde886cdc04196f30f13112047","The properties of wavelike eddies imbedded in zonal flows containing vertical and horizontal shear are examined via an analytical model of a midlatitude cyclone. The model and extends some work by several previous investigators, Perturbation methods are used to formulate and solve this model. A transformation to geostropic coordinates is employed that includes some ageostrophic effects and additional ageostrophic terms are retained after scaling the primitive equations. The zonal flows are chosen to model conditions observed in the atmosphere during incipent wave-cyclone development. Solutions grow due to barotropic and (primarily) baroclinic instability of the zonal flow. -from Author"
"6602242999;","Numerical simulation studies of oceanic anomalies in the North Pacific basin. 1: The ocean model and the long-term mean state.",1978,"10.1175/1520-0485(1978)008<0755:nssooa>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0017859056&doi=10.1175%2f1520-0485%281978%29008%3c0755%3anssooa%3e2.0.co%3b2&partnerID=40&md5=53486ba3c7a57629fc1b4fa7c7068a4c","A three-dimensional, prognostic numerical model of the North Pacific Ocean, possessing an actual coastal configuration and ten layers (but constant depth), has been developed in order to show the physical nature of large-scale normal and abnormal characteristics of this ocean in response to various normal and anomalous seasonal meteorological conditions. Based on the simulated energetics, emphasis is given to the identification of the major physical processes and essential dynamic mechanisms responsible for the generation, evolution and dissipation of large-scale an omalies in the North Pacific Ocean. The model is based on time integrations of the finite-difference forms of the primitive equations. The oceanic circulation is driven by atmospheric forcing, namely, the surface wind stresses and the differential heating over the ocean. The flux form of numerical scheme for energy conservation and the rigid-lid approximation for filtering out the external inertia-gravity wave are used in the formulation. The model was spun-up for more than 60 years with the annual mean atmospheric data as the forcing boundary conditions. The long-term mean state in the model reveals the large-scale features of the circulation patterns and distributions in the North Pacific Ocean. Three tyres, one large anticyclonic in the subtropical region and two smaller ones in the subarctic and in the tropic regions, are well developed. The total transport near the western boundary reached 56 x 10SUB6mSUB3sSUB1SUB1, which agrees reasonably well with the observed mean transport in the Kuroshio Current south of Japan. The equatorial currents, the Oyashio Current, the North Pacific Current, the Alaska Current and the California Current are simulated roughly in the model. There is upwelling along both the equator and the western boundary. Temperature and salinity distributions, except in high latitudes, compare well with observational data. (A)"
"57193919486;7201425334;","Interaction of the westerlies with the Tibetan Plateau in determining the Mei-Yu termination",2020,"10.1175/JCLI-D-19-0319.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079888584&doi=10.1175%2fJCLI-D-19-0319.1&partnerID=40&md5=9bdded65d2cd3ce6fe9c68eacb15f7b7","This study explores how the termination of the mei-yu is dynamically linked to the westerlies impinging on the Tibetan Plateau. It is found that the mei-yu stage terminates when the maximum upper-tropospheric westerlies shift beyond the northern edge of the plateau, around 408N. This termination is accompanied by the disappearance of tropospheric northerlies over northeastern China. The link between the transit of the jet axis across the northern edge of the plateau, the disappearance of northerlies, and termination of the mei-yu holds on a range of time scales from interannual through seasonal and pentad. Diagnostic analysis indicates that the weakening of the meridional moisture contrast and meridional wind convergence, mainly resulting from the disappearance of northerlies, causes the demise of the mei-yu front. The authors propose that the westerlies migrating north of the plateau and consequent weakening of the extratropical northerlies triggers the mei-yu termination. Model simulations are employed to test the causality between the jet and the orographic downstream northerlies by repositioning the northern edge of the plateau. As the plateau edge extends northward, orographic forcing on the westerlies strengthens, leading to persistent strong downstream northerlies and a prolonged mei-yu. Idealized simulations with a dry dynamical core further demonstrate the dynamical link between the weakening of orographically forced downstream northerlies with the positioning of the jet from south to north of the plateau. Changes in the magnitude of orographically forced stationary waves are proposed to explain why the downstream northerlies disappear when the jet axis migrates beyond the northern edge of the plateau. © 2019 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"34770453800;7003670680;57196214814;57210998695;57203659066;7402332362;56587953600;","Future Directions for Whole Atmosphere Modeling: Developments in the Context of Space Weather",2019,"10.1029/2019SW002267","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85072185784&doi=10.1029%2f2019SW002267&partnerID=40&md5=9fa6e21a18ad5130277ab978bc08b61a","Coupled Sun-to-Earth models represent a key part of the future development of space weather forecasting. With respect to predicting the state of the thermosphere and ionosphere, there has been a recent paradigm shift; it is now clear that any self-respecting model of this region needs to include some representation of forcing from the lower atmosphere, as well as solar and geomagnetic forcing. Here we assess existing modeling capability and set out a road map for the important next steps needed to ensure further advances. These steps include a model verification strategy, analysis of the impact of nonhydrostatic dynamical cores, and a cost-benefit analysis of model chemistry for weather and climate applications. ©2019. American Geophysical Union. All Rights Reserved."
"7401436524;57207473157;7701329716;55899884100;25226875800;21734155600;26423472100;","Recent Progress in Numerical Atmospheric Modeling in China",2019,"10.1007/s00376-019-8203-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068705703&doi=10.1007%2fs00376-019-8203-1&partnerID=40&md5=d09503f0b7179c1b87df9ff8d0b4966f","This review summarizes the scientific and technical progress in atmospheric modeling in China since 2011, including the dynamical core, model physics, data assimilation, ensemble forecasting, and model evaluation strategies. In terms of the dynamical core, important efforts have been made in the improvement of the existing model formulations and in exploring new modeling approaches that can better adapt to massively parallel computers and global multiscale modeling. With regard to model physics, various achievements in physical representations have been made, especially a trend toward scale-aware parameterization for accommodating the increase of model resolution. In the field of data assimilation, a 4D-Var system has been developed and is operationally used by the National Meteorological Center of China, and its performance is promising. Furthermore, ensemble forecasting has played a more important role in operational forecast systems and progressed in many fundamental techniques. Model evaluation strategies, including key performance metrics and standardized experimental protocols, have been proposed and widely applied to better understand the strengths and weaknesses of the systems, offering key routes for model improvement. The paper concludes with a concise summary of the status quo and a brief outlook in terms of future development. © 2019, Institute of Atmospheric Physics/Chinese Academy of Sciences, and Science Press and Springer-Verlag GmbH Germany, part of Springer Nature."
"13406399300;7402435469;","A Total Energy Error Analysis of Dynamical Cores and Physics-Dynamics Coupling in the Community Atmosphere Model (CAM)",2019,"10.1029/2018MS001549","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065667470&doi=10.1029%2f2018MS001549&partnerID=40&md5=6998f096f575aec3a23a0655a2875b31","A closed total energy (TE) budget is of utmost importance in coupled climate system modeling; in particular, the dynamical core or physics-dynamics coupling should ideally not lead to spurious TE sources/sinks. To assess this in a global climate model, a detailed analysis of the spurious sources/sinks of TE in National Center for Atmospheric Research's Community Atmosphere Model (CAM) is given. This includes spurious sources/sinks associated with the parameterization suite, the dynamical core, TE definition discrepancies, and physics-dynamics coupling. The latter leads to a detailed discussion of the pros and cons of various physics-dynamics coupling methods commonly used in climate/weather modeling. ©2019. The Authors."
"23501789500;7202447177;7801332133;7003888687;","A new dynamical core of the Global Environmental Multiscale (GEM) model with a height-based terrain-following vertical coordinate",2019,"10.1175/MWR-D-18-0438.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073885304&doi=10.1175%2fMWR-D-18-0438.1&partnerID=40&md5=436acb55ab255e6bfe0f5fc00ebac20b","A new dynamical core of Environment and Climate Change Canada's Global Environmental Multiscale (GEM) atmospheric model is presented. Unlike the existing log-hydrostatic-pressure-type terrainfollowing vertical coordinate, the proposed core adopts a height-based approach. The move to a heightbased vertical coordinate is motivated by its potential for improving model stability over steep terrain, which is expected to become more prevalent with the increasing demand for very high-resolution forecasting systems. A dynamical core with height-based vertical coordinate generally requires an iterative solution approach. In addition to a three-dimensional iterative solver, a simplified approach has been devised allowing the use of a direct solver for the new dynamical core that separates a threedimensional elliptic boundary value problem into a set of two-dimensional independent Helmholtz problems. The issue of dynamics-physics coupling has also been studied, and incorporating the physics tendencies within the discretized dynamical equations is found to be the most acceptable approach for the height-based vertical coordinate. The new dynamical core is evaluated using numerical experiments that include two-dimensional nonhydrostatic theoretical cases as well as 25-km resolution global forecasts. For a wide range of horizontal grid resolutions-from a few meters to up to 25 km-the results from the direct solution approach are found to be equivalent to the iterative approach for the new dynamical core. Furthermore, results from the different numerical experiments confirm that the new height-based dynamical core is equivalent to the existing pressure-based core in terms of solution accuracy. © 2019 American Meteorological Society."
"57159176000;6701588197;55597097400;6602533026;","Ocean modelling and altimeter data reveal the possible occurrence of intrinsic low-frequency variability of the Kuroshio Extension",2018,"10.1016/j.ocemod.2018.08.006","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052466761&doi=10.1016%2fj.ocemod.2018.08.006&partnerID=40&md5=ad4e284d1202b64dfcdd4a11babfab85","In this paper the combined use of model simulations and altimeter data suggests that, during the interval 1998–2006, the Kuroshio Extension (KE) low-frequency variability was mainly of intrinsic origin. The model is based on the primitive equations for a reduced-gravity ocean, is eddy-permitting and relatively idealized, but it includes essential elements of realism and is driven by a time-independent climatological wind field, so that the modelled variability is necessarily of intrinsic oceanic origin. The altimeter data are provided by AVISO and include all the data available to date. A new composite index Λ[Φ] specifically conceived for the KE is used in the analysis of both model and altimeter data (Φ gives the mean latitudinal position of the KE jet and Λ is a measure of the high-frequency variability of the KE path). A set of sensitivity numerical experiments shows that the frontal dynamics is extremely sensitive to the horizontal eddy viscosity. A self-sustained relaxation oscillation emerging from a reference simulation is represented by a loop in the (Λ Φ)-plane and is characterized by four phases, each one being controlled by a specific dynamical mechanism. An interval ranging from January 1998 to March 2006 is identified in the altimeter data, during which the altimeter-derived index is very similar to the modelled one. A detailed analysis based also on sea surface height maps shows that the real KE evolution possesses four phases characterized by basically the same dynamical behaviour recognized in the model loop. The conclusion is that, during that interval, the KE dynamics was controlled by an oceanic intrinsic mode of low-frequency variability and that the directly driven dynamics and ocean-atmosphere coupled modes of variability did not overshadow the intrinsic evolution. The self-sustained vs excited character of the relaxation oscillation is finally discussed. © 2018 Elsevier Ltd"
"57203042083;6506238357;","Towards a More Earth-Like Circulation in Idealized Models",2018,"10.1029/2018MS001356","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050357638&doi=10.1029%2f2018MS001356&partnerID=40&md5=19746a90c17f6f1a17845699bc251733","Idealized models are useful for the investigation of dynamical phenomena in which physical processes play a secondary role. Typically, such models employ highly idealized topography and zonally symmetric equilibrium temperatures as forcings. However, these simplifications are somewhat unrealistic and make these models unfit for investigations in which similarity with the real atmosphere is crucial. In this study, we present a new idealized model of the stratosphere-troposphere system which has a more Earth-like circulation than previous models. We accomplish this by introducing into the dry dynamical core of the Geophysical Fluid Dynamics Laboratory realistic topography and equilibrium temperatures with zonal asymmetries. We then explore the model's sensitivity to the prescribed strength of the surface momentum drag. We find improvements in the model's circulation when validating against reanalysis. Most notably, the strength and structure of the winds, the spectrum of planetary waves, and the frequency of stratospheric sudden warming events are more realistic than in traditional idealized models. In the extratropics, the diagnosed diabatic forcing of the model also compares favorably against the observations. We further find that variations in the surface momentum damping exert an important control on the model's circulation, including the frequency of stratospheric sudden warming events. We believe that the new model reduces the gap between traditional idealized models and full models and that it is useful for the investigation of phenomena in which greater similarity with the real system is needed. The code for the new model and its equilibrium temperature data set is published on GitHub. ©2018. The Authors."
"6507253177;7005808242;","The finite-amplitude evolution of mixed Kelvin-Rossby wave instability and equatorial superrotation in a shallow-water model and an idealized GCM",2018,"10.1175/JAS-D-17-0386.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85049789855&doi=10.1175%2fJAS-D-17-0386.1&partnerID=40&md5=8cf8845c74763721a900294e6e78fd51","An instability involving the resonant interaction of a Rossby wave and a Kelvin wave has been proposed to drive equatorial superrotation in planetary atmospheres with a substantially smaller radius or a smaller rotation rate than Earth, that is, with a large thermal Rossby number. To pursue this idea, this paper investigates the equilibration mechanism of Kelvin-Rossby instability by simulating the unforced initial-value problem in a shallow-water model and in a multilevel primitive equation model. Although the instability produces equatorward momentum fluxes in both models, only the multilevel model is found to superrotate. It is argued that the shortcoming of the shallow-water model is due to its difficulty in representing Kelvin wave breaking and dissipation, which is crucial for accelerating the flow in the tropics. In the absence of dissipation, the zonal momentum fluxed into the tropics is contained in the eddy contribution to the mass-weighted zonal wind rather than the zonal-mean zonal flow itself. In the shallow-water model, the zonal-mean zonal flow is only changed by the eddy potential vorticity flux, which is very small in our flow in the tropics and can only decelerate the flow in the absence of external vorticity stirring. © 2018 American Meteorological Society."
"56079004000;57203479688;","On the local view of atmospheric available potential energy",2018,"10.1175/JAS-D-17-0330.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85048388378&doi=10.1175%2fJAS-D-17-0330.1&partnerID=40&md5=e483f36ba63d0902eb21fc7fd6e1f79d","The possibility of constructing Lorenz's concept of available potential energy (APE) from a local principle has been known for some time, but it has received very little attention so far. Yet the local APE density framework offers the advantage of providing a positive-definite local form of potential energy, which, like kinetic energy, can be transported, converted, and created or dissipated locally. In contrast to Lorenz's definition, which relies on the exact from of potential energy, the local APE density theory uses the particular form of potential energy appropriate to the approximations considered. In this paper, this idea is illustrated for the dry hydrostatic primitive equations, whose relevant form of potential energy is the specific enthalpy. The local APE density is nonquadratic in general but can nevertheless be partitioned exactly into mean and eddy components regardless of the Reynolds averaging operator used. This paper introduces a new form of the local APE density that is easily computable from atmospheric datasets. The advantages of using the local APE density over the classical Lorenz APE are highlighted. The paper also presents the first calculation of the three-dimensional local APE density in observation-based atmospheric data. Finally, it illustrates how the eddy and mean components of the local APE density can be used to study regional and temporal variability in the large-scale circulation. It is revealed that advection from high latitudes is necessary to supply APE into the storm-track regions, and that Greenland and the Ross Sea, which have suffered from rapid land ice and sea ice loss in recent decades, are particularly susceptible to APE variability. © 2018 American Meteorological Society."
"56973805300;7005561589;","Testing the sensitivity of the extratropical response to the location, amplitude, and propagation speed of tropical convection",2018,"10.1175/JAS-D-17-0132.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042236532&doi=10.1175%2fJAS-D-17-0132.1&partnerID=40&md5=4703896e714bed784d455a1d02d2a90d","The dynamical core of a dry global model is used to investigate the role of central Pacific versus warm pool tropical convection on the extratropical response over the North Pacific and North America. A series of model runs is performed in which the amplitude of the warm pool (WP) and central Pacific (CP) heating anomalies associated with the MJO and El Niño-Southern Oscillation (ENSO) is systematically varied. In addition, model calculations based on each of the eight MJO phases are performed, first using stationary heating, and then with heating corresponding to a 48-day MJO cycle and to a 32-day MJO cycle. In all model runs, the extratropical response to tropical convection occurs within 7-10 days of the convective heating. The response is very sensitive to the relative amplitude of the heating anomalies. For example, when heating anomalies in the WP and CP have similar amplitude but opposite sign, the amplitude of the extratropical response is much weaker than is typical for the MJO and ENSO. For the MJO, when the WP heating anomaly is much stronger than the CP heating anomaly (vice versa for ENSO), the extratropical response is amplified. For the MJO heating, it is found that the extratropical responses to phases 4 and 8 are most distinct. A likely factor contributing to this distinctiveness involves the relative amplitude of the two heating anomalies. The stationary and moving (48- and 32-day) heating responses are very similar, revealing a lack of sensitivity to the MJO phase speed. © 2018 American Meteorological Society."
"55622685700;7201784177;","Dynamics of extreme stratospheric negative heat flux events in an idealized model",2018,"10.1175/JAS-D-17-0263.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062152576&doi=10.1175%2fJAS-D-17-0263.1&partnerID=40&md5=a9ebafcf6d3dd85c58167d6576a897ad","Recent work has shown that extreme stratospheric wave-1 negative heat flux events couple with the troposphere via an anomalous wave-1 signal. Here, a dry dynamical core model is used to investigate the dynamical mechanisms underlying the events. Ensemble spectral nudging experiments are used to isolate the role of specific dynamical components: 1) the wave-1 precursor, 2) the stratospheric zonal-mean flow, and 3) the higher-order wavenumbers. The negative events are partially reproduced when nudging the wave-1 precursor and the zonal-mean flow whereas they are not reproduced when nudging either separately. Nudging the wave-1 precursor and the higher-order wavenumbers reproduces the events, including the evolution of the stratospheric zonal-mean flow. Mechanism denial experiments, whereby one component is fixed to the climatology and others are nudged to the event evolution, suggest higher-order wavenumbers play a role by modifying the zonal-mean flow and through stratospheric wave-wave interaction. Nudging all tropospheric wave precursors (wave-1 and higher-order wavenumbers) confirms they are the source of the stratospheric waves. Nudging all stratospheric waves reproduces the tropospheric wave-1 signal. Taken together, the experiments suggest the events are consistent with downward wave propagation from the stratosphere to the troposphere and highlight the key role of higher-order wavenumbers. © 2018 American Meteorological Society."
"57196214814;7004093651;","Numerical effects on vertical wave propagation in deep-atmosphere models",2018,"10.1002/qj.3229","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044418166&doi=10.1002%2fqj.3229&partnerID=40&md5=4efec63dee314eb4ef445c5200df7337","Ray-tracing techniques have been used to investigate numerical effects on the propagation of acoustic and gravity waves in a non-hydrostatic dynamical core discretized using an Arakawa C-grid horizontal staggering of variables and a Charney–Phillips vertical staggering of variables with a semi-implicit timestepping scheme. The space discretization places limits on resolvable wavenumbers, and redirects the group velocity and the propagation of wave energy towards the vertical. The time discretization slows the wave propagation while maintaining the group velocity direction. Wave amplitudes grow exponentially with height due to the decrease in the background density, which can cause instabilities in whole-atmosphere models. Although molecular viscosity effectively damps the exponential growth of waves above about 150 km, additional numerical damping might be needed to prevent instabilities in the lowermost thermosphere. These results are relevant to the Met Office Unified Model, and provide insight into how the stability of the model may be improved as the model's upper boundary is raised into the thermosphere. © 2017 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"56082999200;7801685612;8356333900;28267547300;","Western boundary upwelling dynamics off Oman",2017,"10.1007/s10236-017-1044-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016616734&doi=10.1007%2fs10236-017-1044-5&partnerID=40&md5=526704db4ea93d517390397c7fca7e98","Despite its climatic and ecosystemic significance, the coastal upwelling that takes place off Oman is not well understood. A primitive-equation, regional model forced by climatological wind stress is used to investigate its dynamics and to compare it with the better-known Eastern Boundary Upwellings (EBUs). The solution compares favorably with existing observations, simulating well the seasonal cycles of thermal structure, surface circulation (mean and turbulent), and sea-surface temperature (SST). There is a 1.5-month lag between the maximum of the upwelling-favorable wind-stress-curl forcing and the oceanic response (minima in sea-surface height and SST), which we attribute to onshore-propagating Rossby waves. A southwestward-flowing undercurrent (opposite to the direction of the near-surface flow) is also simulated with a core depth of 1000 m, much deeper than found in EBUs (150–200 m). An EKE budget reveals that, in contrast to EBUs, the upwelling jet is more prone to barotropic than baroclinic instability and the contribution of locally-generated instabilities to EKE is higher by an order of magnitude. Advection and redistribution of EKE by standing mesoscale features also play a significant role in EKE budget. © 2017, The Author(s)."
"56583515100;8922308700;15848674200;15755995900;","Evaluation of tropical channel refinement using MPAS-A aquaplanet simulations",2015,"10.1002/2015MS000470","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945464868&doi=10.1002%2f2015MS000470&partnerID=40&md5=da964f61366c173061ee6a0f6f552bd5","Climate models with variable-resolution grids offer a computationally less expensive way to provide more detailed information and increased accuracy by resolving processes that cannot be adequately represented by a coarser grid. This study uses the Model for Prediction Across Scales-Atmosphere (MPAS-A), consisting of a nonhydrostatic dynamical core and a subset of Weather Research and Forecasting (WRF) model physics, to investigate the potential benefits of using tropical channel refinement. The simulations are performed with an idealized aquaplanet configuration using 30 and 240 km global grid spacing, and two variable-resolution grids spanning the same grid spacing range; one with a narrow (20S-20N) and one with a wide (30S-30N) tropical channel refinement. Increasing resolution in the tropics impacts both the tropical and extratropical circulation. Compared to the 30 km global grid, both refined channel simulations exhibit slightly stronger updrafts inside the Hadley cell resulting in more resolved precipitation. Using a wider tropical refinement leads to a closer correspondence with the global high-resolution grid. While different grid spacings produce similar cloud size distributions that are consistent with observations, the dependence of precipitation rate on cloud size varies among simulations. The refined channel simulations show improved tropical and extratropical precipitation relative to the global coarse simulation. All simulations show a single precipitation peak centered on the equator. Although the results show that tropical refinement is an effective method for avoiding artifacts due to grid resolution sensitivities seen in earlier studies that only refined a portion of the tropics, some biases remain well inside of the refinement region. © 2015. The Authors."
"56555746000;56283067400;56225695300;56555539800;","Implementation of a GPS-RO data processing system for the KIAPS-LETKF data assimilation system",2015,"10.5194/amt-8-1259-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924984376&doi=10.5194%2famt-8-1259-2015&partnerID=40&md5=a8266cdb079a248e923c564b11d8fb29","The Korea Institute of Atmospheric Prediction Systems (KIAPS) has been developing a new global numerical weather prediction model and an advanced data assimilation system. As part of the KIAPS package for observation processing (KPOP) system for data assimilation, preprocessing, and quality control modules for bending-angle measurements of global positioning system radio occultation (GPS-RO) data have been implemented and examined. The GPS-RO data processing system is composed of several steps for checking observation locations, missing values, physical values for Earth radius of curvature, and geoid undulation. An observation-minus-background check is implemented by use of a one-dimensional observational bending-angle operator, and tangent point drift is also considered in the quality control process. We have tested GPS-RO observations utilized by the Korean Meteorological Administration (KMA) within KPOP, based on both the KMA global model and the National Center for Atmospheric Research Community Atmosphere Model with Spectral Element dynamical core (CAM-SE) as a model background. Background fields from the CAM-SE model are incorporated for the preparation of assimilation experiments with the KIAPS local ensemble transform Kalman filter (LETKF) data assimilation system, which has been successfully implemented to a cubed-sphere model with unstructured quadrilateral meshes. As a result of data processing, the bending-angle departure statistics between observation and background show significant improvement. Also, the first experiment in assimilating GPS-RO bending angle from KPOP within KIAPS-LETKF shows encouraging results. © 2015 Author(s)."
"36098236100;7201356364;15044268700;","Algorithmically scalable block preconditioner for fully implicit shallow-water equations in CAM-SE",2015,"10.1007/s10596-014-9447-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940007142&doi=10.1007%2fs10596-014-9447-6&partnerID=40&md5=93aae6499705cb6a6bfa3057a550fb6c","Performing accurate and efficient numerical simulation of global atmospheric climate models is challenging due to the disparate length and time scales over which physical processes interact. Implicit solvers enable the physical system to be integrated with a time step commensurate with processes being studied. The dominant cost of an implicit time step is the ancillary linear system solves, so we have developed a preconditioner aimed at improving the efficiency of these linear system solves. Our preconditioner is based on an approximate block factorization of the linearized shallow-water equations and has been implemented within the spectral element dynamical core within the Community Atmospheric Model (CAM-SE). In this paper, we discuss the development and scalability of the preconditioner for a suite of test cases with the implicit shallow-water solver within CAM-SE. © 2014, Springer International Publishing Switzerland."
"36701354800;56202321100;56883413400;","Improve the simulations of near-inertial internal waves in the ocean general circulation models",2015,"10.1175/JTECH-D-15-0046.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946543812&doi=10.1175%2fJTECH-D-15-0046.1&partnerID=40&md5=999ae3b108e2c3cb8de81f4965198d08","The near-inertial wind work and near-inertial internal waves (NIWs) in the ocean have been extensively studied using ocean general circulation models (OGCMs) forced by 6-hourly winds or wind stress obtained from atmospheric reanalysis data. However, the OGCMs interpolate the reanalysis winds or wind stress linearly onto each time step, which partially filters out the wind stress variance in the near-inertial band. In this study, the influence of the linear interpolation on the near-inertial wind work and NIWs is quantified using an eddy-resolving (1/10°) primitive equation ocean model. In addition, a new interpolation method is proposed-the sinc-function interpolation-that overcomes the shortages of the linear interpolation. It is found that the linear interpolation of 6-hourly winds significantly underestimates the near-inertial wind work and NIWs at the midlatitudes. The underestimation of the near-inertial wind work and near-inertial kinetic energy is proportional to the loss of near-inertial wind stress variance due to the linear interpolation. This further weakens the diapycnal mixing in the ocean due to the reduced near-inertial shear variance. Compared to the linear interpolation, the sinc-function interpolation retains all the wind stress variance in the near-inertial band and yields correct magnitudes for the near-inertial wind work and NIWs at the midlatitudes. © 2015 American Meteorological Society."
"35267848800;25625063100;6507331574;55945888500;28267547300;","Cyclones and anticyclones in seismic imaging",2015,"10.1175/JPO-D-15-0066.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945950250&doi=10.1175%2fJPO-D-15-0066.1&partnerID=40&md5=9ec04c635c35e5a25ec5a34ed3f81c93","Nearly all the subsurface eddies detected in seismic imaging of sections in the northeast Atlantic have been assumed to be anticyclones containing Mediterranean Water (MW). Fewer MWcyclones have been observed and studied. In this study, the work of previous numerical studies is extended to investigate some characteristics of layering surrounding MW cyclones, using a primitive equation model with equal diffusivities for salinity and temperature to suppress the effects of double diffusion. It is shown that, after a stable state is reached, both anticyclones and cyclones display similar patterns of layering: stacked thin layers of high acoustic reflectivity located above and below the core of each vortex, which do not match isopycnals. The authors conclude that it should not be possible to distinguish betweenMWcyclones and anticyclones based on their signature in seismic imaging alone. Complementary information is needed to determine the sense of rotation. © 2015 American Meteorological Society."
"36088682200;6603822174;","Inherently mass-conservative version of the semi-Lagrangian absolute vorticity (SL-AV) atmospheric model dynamical core",2014,"10.5194/gmd-7-407-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897589923&doi=10.5194%2fgmd-7-407-2014&partnerID=40&md5=4fa160d11461af2eff76ea756fcea6fe","The semi-Lagrangian absolute vorticity (SL-AV) atmospheric model is the global semi-Lagrangian hydrostatic model used for operational medium-range and seasonal forecasts at the Hydrometeorological Centre of Russia. The distinct feature of the SL-AV dynamical core is the semi-implicit, semi-Lagrangian vorticity-divergence formulation on the unstaggered grid. A semi-implicit, semi-Lagrangian approach allows for long time steps but violates the global and local mass conservation. In particular, the total mass in simulations with semi-Lagrangian models can drift significantly if no a posteriori mass-fixing algorithm is applied. However, the global mass-fixing algorithms degrade the local mass conservation. <br><br> The new inherently mass-conservative version of the SL-AV model dynamical core presented here ensures global and local mass conservation without mass-fixing algorithms. The mass conservation is achieved with the introduction of the finite-volume, semi-Lagrangian discretization for a continuity equation based on the 3-D extension of the conservative cascade semi-Lagrangian transport scheme (CCS). Numerical experiments show that the new version of the SL-AV dynamical core presented combines the accuracy and stability of the standard SL-AV dynamical core with the mass-conservation properties. The results of the mountain-induced Rossby-wave test and baroclinic instability test for the mass-conservative dynamical core are found to be in agreement with the results available in the literature. © Author(s) 2014. CC Attribution 3.0 License."
"7402435469;","Dependence of APE simulations on vertical resolution with the community atmospheric model, version 3",2013,"10.2151/jmsj.2013-A08","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880671824&doi=10.2151%2fjmsj.2013-A08&partnerID=40&md5=eb27c43e7e8fb627268642f54280538e","The convergence of the zonal averaged equatorial precipitation with increasing vertical resolution in simulations with Community Atmosphere Model (CAM3) Eulerian spectral transform and finite volume dynamical cores is considered. The cores are both coupled to the standard CAM3 parameterization package. With the standard CAM3 26 level grid, the two versions converge to different states when the horizontal resolution alone is refined; the spectral transform to a single precipitation maximum and the finite volume to a double. With increasing vertical resolution both converge to a double structure. However, in the subsidence regions the high vertical resolution simulations have a very different climate balance and parameterized forcing than the lower resolution simulations and thus they do not represent the expected climate associated with the lower resolution dynamical cores. The cause of the different parameterized forcing is studied by considering the evolution of the 60-level model starting from a state created by the 26-level model. The cause is shown to be the discrete approximations in the shallow convection. When the 60-level model is presented with an initial state interpolated from a 26-level model state, the columns are stable by the discrete test in the shallow convection, even though they are unstable when the discrete calculation is based on the coarser 26-level grid. The Planetary Boundary Layer parameterization pumps water vapor into the lower troposphere, low clouds increase to unrealistic levels and force strong longwave radiative cooling. This destabilizes the column until the discrete test is satisfied on the 60-level grid and the shallow convection becomes active again. However the simulated state is by then very different and unlike the earth's atmosphere. Similar unrealistic behavior has been seen in earth-like simulations. © 2013, Meteorological Society of Japan."
"55349512400;6504676673;55817344400;","How accurately are climatological characteristics and surface water and energy balances represented for the Colombian Caribbean Catchment Basin?",2013,"10.1007/s00382-013-1685-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84884701628&doi=10.1007%2fs00382-013-1685-0&partnerID=40&md5=bd4f32565d0df5a6822bc5a62de4cdc7","In Colombia, the access to climate related observational data is restricted and their quantity is limited. But information about the current climate is fundamental for studies on present and future climate changes and their impacts. In this respect, this information is especially important over the Colombian Caribbean Catchment Basin (CCCB) that comprises over 80 % of the population of Colombia and produces about 85 % of its GDP. Consequently, an ensemble of several datasets has been evaluated and compared with respect to their capability to represent the climate over the CCCB. The comparison includes observations, reconstructed data (CPC, Delaware), reanalyses (ERA-40, NCEP/NCAR), and simulated data produced with the regional climate model REMO. The capabilities to represent the average annual state, the seasonal cycle, and the interannual variability are investigated. The analyses focus on surface air temperature and precipitation as well as on surface water and energy balances. On one hand the CCCB characteristics poses some difficulties to the datasets as the CCCB includes a mountainous region with three mountain ranges, where the dynamical core of models and model parameterizations can fail. On the other hand, it has the most dense network of stations, with the longest records, in the country. The results can be summarised as follows: all of the datasets demonstrate a cold bias in the average temperature of CCCB. However, the variability of the average temperature of CCCB is most poorly represented by the NCEP/NCAR dataset. The average precipitation in CCCB is overestimated by all datasets. For the ERA-40, NCEP/NCAR, and REMO datasets, the amplitude of the annual cycle is extremely high. The variability of the average precipitation in CCCB is better represented by the reconstructed data of CPC and Delaware, as well as by NCEP/NCAR. Regarding the capability to represent the spatial behaviour of CCCB, temperature is better represented by Delaware and REMO, while precipitation is better represented by Delaware. Among the three datasets that permit an analysis of surface water and energy balances (REMO, ERA-40, and NCEP/NCAR), REMO best demonstrates the closure property of the surface water balance within the basin, while NCEP/NCAR does not demonstrate this property well. The three datasets represent the energy balance fairly well, although some inconsistencies were found in the individual balance components for NCEP/NCAR. © 2013 Springer-Verlag Berlin Heidelberg."
"55802056700;15765007300;","Spontaneous QBO-like oscillations in an atmospheric model dynamical core",2013,"10.1002/grl.50723","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880639960&doi=10.1002%2fgrl.50723&partnerID=40&md5=bcc843de40bea31d20ecfbe30c5e3b65","The ability of general circulation models (GCMs) to simulate the quasi-biennial oscillation (QBO) is an important model characteristic. Typically, the moist convective parameterization is believed to be the key GCM component that triggers tropical waves, thereby forcing wave-mean flow interactions. We show that QBO-like oscillations can also be simulated in a dry dynamical core driven by the Held-Suarez forcing. No gravity wave drag parameterization is applied. The simulations utilize the semi-Lagrangian spectral transform dynamical core of National Center for Atmospheric Research's Community Atmosphere Model. The QBO-like signal has a long period between 42-45 months and occurs in the upper stratosphere; different from observations. However, the amplitudes, asymmetries, and meridional extent closely resemble the observed QBO. Wave-number frequency analysis shows that resolved equatorially trapped waves are abundant despite the absence of cumulus convection. A Transformed Eulerian-Mean analysis suggests that the divergence of the Eliassen-Palm flux and vertical advection provide most of the forcing counteracted by diffusion. © 2013. American Geophysical Union. All Rights Reserved."
"7004069241;57193921169;","Exact axisymmetric solutions of the deep- and shallow-atmosphere Euler equations in curvilinear and plane geometries",2013,"10.1002/qj.2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879232310&doi=10.1002%2fqj.2018&partnerID=40&md5=d4bf1e6b0d11b328bb8da83934bc6591","A wide family of exact closed-form axisymmetric solutions to the deep- and shallow-atmosphere Euler equations is derived. These solutions are not only valid in general curvilinear geometry, but also in beta-plane and beta-gamma-plane geometries. A further generalisation of the generalised thermal wind equation is also derived. The enhanced generality of the exact solutions developed herein provides more flexibility in the specification of initial conditions for numerical model validation. This permits the construction not only of more challenging, balanced, shallow- and deep-atmosphere solutions than has hitherto been possible, but also of more elaborate tests of the baroclinic wave type. © 2012 British Crown copyright, the Met Office. Published by John Wiley & Sons Ltd.."
"55574123301;6506900387;35767429400;","On imbalance generated by vortical flows in a two-layer spherical boussinesq primitive equation model",2012,"10.1175/JAS-D-11-0318.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84867946383&doi=10.1175%2fJAS-D-11-0318.1&partnerID=40&md5=fe7c77ebfedba4bc7a9c822f3b4b603b","The spontaneous adjustment emission of inertia-gravity waves is investigated by examining the amount of imbalance generated during the evolution of unstable jets in an isentropic two-layer primitive equation model on the sphere. To determine the balance and thus the imbalance, potential vorticity (PV) inversion by means of the first-, second-, and third-order plain-δδ, plain-δγ, and plain-γγ balance relations, as well as the Bolin-Charney balance relations, is applied. Five sets of experiments are carried out by (i) changing the upper-layer potential temperature with a fixed initial jet speed and (ii) changing the initial jet speed with a fixed upper-layer potential temperature. For each set, the relation between the optimal measure of imbalance with the corresponding measure of balanced vortical flow is sought at the peak of instability. The minimal imbalance obtained by 1 of the above 10 PV inversion procedures is considered as the optimal. The focus herein is on the magnitude of imbalance and its scaling with various measures of balanced flow. It is shown that for the magnitude of imbalance it is always possible to find the proper measure with an exponentially small scaling. For the imbalance-to-balance ratio, however, a power law is obtained when either the jet or the stratification is weak. The latter difference in scaling behavior of the imbalance and imbalance-tobalance ratio may be an artifact of the inevitable numerical errors whose effects are felt more strongly when the signature of vortical flow is weak. © 2012 American Meteorological Society."
"24503245200;57197636789;6602418877;","Testing the anelastic nonhydrostatic model EULAG as a prospective dynamical core of a numerical weather prediction model Part I: Dry benchmarks",2011,"10.2478/s11600-011-0041-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053560316&doi=10.2478%2fs11600-011-0041-1&partnerID=40&md5=c76e8b2c49542bec6be21cc7e27012fc","In this paper, a feasibility of anelastic approach for numerical weather prediction (NWP) is examined. The study concerns the anelastic nonhydrostatic model EULAG as a prospective candidate for the new dynamical core of a high-resolution NWP model. Such an application requires a series of benchmark tests to be performed. The study presents the results of dry idealized two-dimensional linear and non-linear tests. They include evolution of cold and warm density currents in neutrally stratified atmosphere, inertia-gravity waves in short and long channels, as well as mountain gravity waves for a set of different flow regimes. Detailed comparison of the results with the reference solutions, based mainly on the results of compressible models, indicates a high level of conformity for all of the experiments. It verifies the anelastic approach as strongly consistent with the compressible one for a broad class of atmospheric problems. It also corroborates the robustness of EULAG numerics, an essential requirement of dynamical core of NWP model. © 2011 Versita Warsaw and Springer-Verlag Wien."
"7402725328;7406243250;7202192265;6603753099;6701357023;","Performance of the HOMME dynamical core in the aqua-planet configuration of NCAR CAM4: Equatorial waves",2011,"10.5194/angeo-29-221-2011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79551706505&doi=10.5194%2fangeo-29-221-2011&partnerID=40&md5=c070fb69b36088b3930a8a2cab11334b","A new atmospheric dynamical core, named the High Order Method Modeling Environment (HOMME), has been recently included in the NCAR-Community Climate System Model version 4 (CCSM4). It is a petascale capable high-order element-based conservative dynamical core developed on a cubed-sphere grid. We have examined the model simulations with HOMME using the aqua-planet mode of CAM4 (atmospheric component of CCSM4) and evaluated its performance in simulating the equatorial waves, considered a crucial element of climate variability. For this we compared the results with two other established models in CAM4 framework, which are the finite-volume (FV) and Eulerian spectral (EUL) dynamical cores. Although the gross features seem to be comparable, important differences have been found among the three dynamical cores. The phase speed of Kelvin waves in HOMME is faster and more satisfactory than those in FV and EUL. The higher phase speed is attributed to an increased large-scale precipitation in the upper troposphere and a more top-heavy heating structure. The variance of the n=1 equatorial Rossby waves is underestimated by all three of them, but comparatively HOMME simulations are more reasonable. For the n=0 eastward inertio-gravity waves, the variances are weak and phase speeds are too slow, scaled to shallow equivalent depths. However, the variance in HOMME is relatively more compared to the two other dynamical cores. The mixed Rossby-gravity waves are feeble in all the three cases. In summary, model simulations using HOMME are reasonably good, with some improvement relative to FV and EUL in capturing some of the important characteristics associated with equatorial waves. © Author(s) 2011."
"8618667100;6603137309;","Interaction of equatorial waves through resonance with the diurnal cycle of tropical heating",2010,"10.1111/j.1600-0870.2010.00463.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957165271&doi=10.1111%2fj.1600-0870.2010.00463.x&partnerID=40&md5=c8afcd37e0ae31e0eba7d23858648007","In this work, a new theoretical mechanism is presented in which equatorial Rossby and inertio-gravity wave modes may interact with each other through resonance with the diurnal cycle of tropical deep convection. We have adopted the two-layer incompressible equatorial primitive equations forced by a parametric heating that roughly represents deep convection activity in the tropical atmosphere. The heat source was parametrized in the simplest way according to the hypothesis that it is proportional to the lower-troposphere moisture convergence, with the background moisture state function mimicking the structure of the ITCZ. In this context, we have investigated the possibility of resonant interaction between equatorially trapped Rossby and inertio-gravity modes through the diurnal cycle of the background moisture state function. The reduced dynamics of a single resonant duo shows that when this diurnal variation is considered, a Rossby wave mode can undergo significant amplitude modulations when interacting with an inertio-gravity wave mode, which is not possible in the context of the resonant triad non-linear interaction. Therefore, the results suggest that the diurnal variation of the ITCZ can be a possible dynamical mechanism that leads the Rossby waves to be significantly affected by high frequency modes. ©2010 The Authors Tellus A © 2010 International Meteorological Institute in Stockholm."
"6701783232;7202358048;","Generation of infrasound by evaporating hydrometeors in a cloud model",2010,"10.1175/2009JAMC2226.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77955578251&doi=10.1175%2f2009JAMC2226.1&partnerID=40&md5=dc93dec2edb320286a2bd7d2a6b60875","The dynamical core of the Regional Atmospheric Modeling System has been tailored to simulate the infrasound of vortex motions and diabatic cloud processes in a convective storm. Earlier studies have shown that the customized model (c-RAMS) adequately simulates the infrasonic emissions of generic vortex oscillations. This paper provides evidence that c-RAMS accurately simulates the infrasound associated with parameterized phase transitions of cloud moisture. Specifically, analytical expressions are derived for the infrasonic emissions of evaporating water droplets in dry and humid environments. The dry analysis considers two single-moment parameterizations of the microphysics, which have distinguishable acoustic signatures. In general, the analytical results agree with the numerical output of the model. An appendix briefly demonstrates the ability of c-RAMS to accurately simulate the infrasound of the entropy and mass sources generated by an equilibrating cloud of icy hydrometeors. © 2010 American Meteorological Society."
"8699212900;13007677000;7102969748;56056796100;","Coupling a two-way nested primitive equation model and a statistical SST predictor of the Ligurian Sea via data assimilation",2006,"10.1016/j.ocemod.2006.02.003","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33646026723&doi=10.1016%2fj.ocemod.2006.02.003&partnerID=40&md5=b0e1f7813e55881114e8878eb054a668","A primitive equation model and a statistical predictor are coupled by data assimilation in order to combine the strength of both approaches. In this work, the system of two-way nested models centred in the Ligurian Sea and the satellite-based ocean forecasting (SOFT) system predicting the sea surface temperature (SST) are used. The data assimilation scheme is a simplified reduced order Kalman filter based on a constant error space. The assimilation of predicted SST improves the forecast of the hydrodynamic model compared to the forecast obtained by assimilating past SST observations used by the statistical predictor. This study shows that the SST of the SOFT predictor can be used to correct atmospheric heat fluxes. Traditionally this is done by relaxing the model SST towards the climatological SST. Therefore, the assimilation of SOFT SST and climatological SST are also compared. © 2006 Elsevier Ltd. All rights reserved."
"55740245100;8972513400;","Analysis of recent extreme events measured by the barotropic component of the atmosphere",2004,"10.2151/jmsj.2004.1281","https://www.scopus.com/inward/record.uri?eid=2-s2.0-11244343979&doi=10.2151%2fjmsj.2004.1281&partnerID=40&md5=b559f1373e19788071fc78145d1d94fb","In this study, recent extreme events over the Northern Hemisphere are quantified in terms of an energy norm of the anomaly of the state variables. Since persistent low-frequency variabilities are characterized, in most cases, by their barotropic structure, the energy norm of the anomaly is measured for the barotropic component of the atmosphere. The norm is then normalized by its climatology to assess the abnormality of the extreme events. In this study the norm is evaluated in the framework of the 3-D spectral primitive equation model to assess the external forcing as well as the state variabiles. According to the analysis of the monthly mean anomaly data for 50 years from 1953 to 2002, the most abnormal months appear to be Apr. 1997, Jan. 1963, Jan. 1977, Mar. 1983, Apr. 1967, Feb. 1989, and Jan. 1989. Those are well known abnormal months in the past studies. In this study, the top 3% of the extreme events are listed as the abnormal months. The quantification of the abnormality is further extended to the external forcing of the barotropic component of the atmosphere and also to the SST anomaly. It is found that only 3 cases of the abnormal months (Jan. 1963, Feb. 1989 and Jan. 1989) are associated with the abnormal external forcing, and the rest of the abnormal months are associated with the non-abnormal external forcing. Likewise, it is found that most of the abnormal external forcing result in a non-abnormal month. The SST forcing anomaly is not directly related to the external forcing. It is concluded from the result that more than 80% of the abnormal months are induced by the natural variability of the barotropic component of the atmosphere under the non-abnormal external forcing for the last 50 years. For the monthly time scale, the chaotic nonlinear behavior is quantitatively larger than a linear response to the external forcing or that to the SST anomaly. © 2004, Meteorological Society of Japan."
"6602147826;54903097700;7005793728;","Pacific Ocean forecasts",2004,"10.1016/j.jmarsys.2003.11.010","https://www.scopus.com/inward/record.uri?eid=2-s2.0-1542349983&doi=10.1016%2fj.jmarsys.2003.11.010&partnerID=40&md5=42fe016b3fcf732847a84615e1496af4","A primitive equation Pacific Ocean model forced by wind stresses and heat fluxes is used to obtain uncoupled forecasts of sea surface temperature (SST), heat storage (upper 400 m), and surface currents. The forecasts are displayed in real-time on the web http://ecpc.ucsd.edu) and are compared against observations obtained from the Reynolds (SST) and Joint Environmental Data Analysis Center, JEDAC http://jedac.ucsd.edu), (0- to 400-m temperature) data sets. The resulting forecast skill, for both total and anomalous fields, are reasonably good given the simplicity of our methodology and the fact that feedback processes between ocean and atmosphere are absent. SST forecasts are equal and even superior to anomaly persistence forecasts in some regions during some seasons. Given this skill, which depends both on model performance and on quality and sampling density of the observations, we are beginning to develop various applications for these experimental forecasts. © 2004 Elsevier B.V. All rights reserved."
"7601317381;55951683800;","The Antarctic Circumpolar Wave in a global, high-resolution, coupled ice-ocean model",2001,"10.3189/172756401781818644","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035652507&doi=10.3189%2f172756401781818644&partnerID=40&md5=a0c40edb94115c941842bff1f21f2e90","The Antarctic Circumpolar Wave (ACW) is identified by White and Peterson (1996) as anomalies in sea-level pressure, meridional wind stress (MWS), sea-surface temperature (SST) and sea-ice extent (SIE) propagating eastward over the Southern Ocean. In this study, the ACW is examined using a global coupled ice-ocean model with an average horizontal grid size of 1/4°. The model is forced with 1979-93 daily average atmospheric data from the European Centre for Medium-range Weather Forecasts (ECMWF) re-analysis (ERA). The sea-ice model includes both dynamics and thermodynamics, and the ocean model is a primitive-equation, free-surface, z-coordinate model. Both standing and propagating oscillations are present in ERA surface net heat-flux (NHF) and MWS anomalies. The ocean and ice respond to such atmospheric forcing with similar standing and propagating oscillations. For the propagating mode, SIE, SST and sea-surface salinity anomalies propagate eastward with a period of about 4-5 years and take about 8-9 years to encircle the Antarctic continent. Thus, the simulated ACW is a wavenumber-2 phenomenon which agrees with the ACW identified by White and Peterson (1996). The correctly simulated strength of the Antarctic Circumpolar Current, which governs the phase speed of oceanic anomalies, in our high-resolution model is essential for obtaining the observed wavenumber-2 ACW mode in the ocean. The ACW signature is also present in ocean temperature and salinity anomalies down to about 1000 m depth with similar eastward-propagating speed. The anomalies in the interior ocean are more coherent and intense over the Pacific and Atlantic sectors than over the Indian sector. Northward (southward) MWS anomalies, northward (southward) SIE anomalies, cold (warm) SST anomalies and saltier (fresher) than normal salinity anomalies are in phase, while less (more) than normal NHF is 90° out of phase with them, indicating the ACW in sea ice and ocean is a response to that in the atmosphere."
"7006236576;","Linear evolution of baroclinic waves in saturated air",1999,"10.1256/smsqj.55507","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032787250&doi=10.1256%2fsmsqj.55507&partnerID=40&md5=194cea4b1b711248752c247de09e2a2c","A primitive-equation model which includes a moisture parametrization that assumes that ascending air is always saturated, has been used to study the characteristics of moist baroclinic waves, exploring their dependence on the Richardson number, besides zonal and meridional wavelength. Growth rates are shown to increase, in consequence of latent-heat release, in a larger measure for the meridionally structured waves than for the two-dimensional ones. Approximate analytic relationships for the normal-modes growth rates, based on the concept of a weighted average of dry and saturated parameters, compare favourably with the numerical results. Asymmetric horizontal structures, previously obtained in quasi-geostrophic approximation, are shown to be consistent with potential-vorticity generation by diabatic heating in the updraught."
"57215451474;22836973600;7101978698;","Stratospheric flow during two recent winters simulated by a mechanistic model",1998,"10.1175/1520-0493(1998)126<1655:SFDTRW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032444458&doi=10.1175%2f1520-0493%281998%29126%3c1655%3aSFDTRW%3e2.0.CO%3b2&partnerID=40&md5=ad5dcc146e1f1c5c3f14ae00cba0359a","The authors have used a spectral, primitive equation mechanistic model of the stratosphere and mesosphere to simulate observed stratospheric flow through the winters of 1991-92 and 1994-95 by forcing the model at 100 hPa with observed geopotential height. The authors assess the model's performance quantitatively by comparing the simulations with the United Kingdom Meteorological Office (UKMO) assimilated stratospheretroposphere data. Time-mean, zonal-mean temperatures are generally within 5 K and winds within 5 m s-1; transient features, such as wave growth, are mostly simulated well. The phase accuracy of planetary-scale waves declines with altitude and wavenumber, and the model has difficulty correctly simulating traveling anticyclones in the upper stratosphere. The authors examine the minor warming of January 1995 which was unusual in its depth and development and which the model simulated fairly well. The authors also examine the minor warming of January 1992, which the model missed, and a major warming in February 1992 that occurred in the model but not in the observations."
"7102366816;7102835431;7004332887;57204410953;","Upper ocean modeling in a coastal bay",1995,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029505311&partnerID=40&md5=299a93eda72d6b85ed06061d9b03a1fe","A numerical model of the upper ocean is developed to study the dynamics and thermodynamics of the Baie des Chaleurs (Gulf of St. Lawrence, Canada). The model has primitive equation dynamics with two active layers embedded with a Niiler-Kraus type mixed layer model at the top. Forced by observed wind, atmospheric heat fluxes, river runoff, and appropriate remote forcing (in particular, the Gaspe Current, (GC)), the model demonstrates that the mean cyclonic general circulation pattern in the bay is a consequence of the intrusion of the GC. The strength of the circulation depends on the resultant stress of prevailing westerly winds and the opposing GC intrusion. -from Authors"
"7004424878;6603206828;","Ocean winds for marine modelling",1992,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027009928&partnerID=40&md5=4b1a5e2acae2082fe3f5f529f3620e8b","A method is described for calculating ocean wind fields as required by wave and circulation models. Winds at the standard height of ten metres are derived from the Australian region primitive equation atmospheric model using a parametric boundary-layer model. The boundary-layer model consists of an outer similarity layer coupled with a logarithmic surface layer. The model is steady state, horizontally homogeneous and barotropic, but includes a stability-dependent correction to both wind speed and direction. Surface winds derived in this way compare very well with ship observations in the southeast Australian region. -from Authors"
"24787174200;57190935343;","Non-Acceleration theorem in a primitive equation system: I. Acceleration of zonal mean flow",1989,"10.1007/BF02656914","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649152510&doi=10.1007%2fBF02656914&partnerID=40&md5=6f365286d50a84d02de101d6bc011ef1","Non-acceleration theorem in a primitive equation system is developed to investigate the influences of waves on the mean flow variation against external forcing. Numerical results show that mechanical forcing overwhelms thermal forcing in maintaining the mean flow in which the internal mechanical forcing associated with horizontal eddy flux of momentum plays the most important roles. Both internal forcing and external forcing are shown to be active and at the first place for the mean flow variations, whereas the forcing-induced mean meridional circulation is passive and secondary. It is also shown that the effects on mean flow of external mechanical forcing are concentrated in the lower troposphere, whereas those due to wave-mean flow interaction are more important in the upper troposphere. These act together and result in the vertically easterly shear in low latitudes and westerly shear in mid-latitudes. This vertical shear of mean flow is to some extent weakened by thermal forcing. © 1989 Advances in Atmospheric Sciences."
"24786836200;57216056744;6506339216;","Sensitivity experiments on summer monsoon circulation cell in east asia",1989,"10.1007/BF02656923","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51249170965&doi=10.1007%2fBF02656923&partnerID=40&md5=b3a800c0e1ca901a08feb0182f8bf838","The East-Asian summer monsoon meridional circulation (SMMC) cell is simulated together with two vigorous rainbands in terms of a primitive-equation model including in itself a variety of diabatic heating, frictional dissipation and moist processes under the condition of mountains available. Results are comparable to observations. Also, performed are experiments with the reduction of water content, and exclusion of the cumulus convective process and mountain effect. Contrast analyses indicate that the cell is strongly sensitive to the condition of the humidity field in the atmosphere, more intensely at 120° than at 100 ° E, and the presence (absence) of the cumulus convection has considerable effect on the intensification(weakening) of the cell, with the mountain ranges exhibiting more influence upon the cell at 100° than 120° E. This may suggest that a great difference lies in the cause of the cell for the two meridions. © 1989 Advances in Atmospheric Sciences."
"7402035094;16459738800;57217887696;","Accurate pressure gradient calculations in hydrostatic atmospheric models",1987,"10.1007/BF00120437","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0023504226&doi=10.1007%2fBF00120437&partnerID=40&md5=d89e58036faaec40f16138d8088d4446","Most models of atmospheric flow which use the primitive equations require a diagnostic equation to determine local total pressure. In hydrostatic models, this equation is the vertically integrated hydrostatic equation. A frequently used approximation to this integration is to hold the temperature constant within model layers yielding a linear proportionality between δp or δπ (Exner's function) and δz. This procedure yields static pressures with errors on the order of 10-3mb. If terrain following coordinates are used, terms arise in the horizontal momentum equations involving the gradient of total pressure along the coordinate surface, less a correction for the variation of the hydrostatic pressure along a sloped surface. Erroneous horizontal accelerations are common in these models which result from spurious pressure gradients that are due to inaccurate computation of the static pressure. This error may be amplified if the computation of the slope correction term of the horizontal pressure gradient is not consistent with the method of calculating the total pressure. We derive a methodology to be used in the vertical pressure integrations that is exact if the potential temperature lapse rate is constant between integration limits. The method is applied to both the integration of the hydrostatic equation and the computation of the slope correction term in the horizontal pressure gradient. The method employs a fixed vertical grid and a dynamic one defined by the significant levels in the vertical temperature distribution. With this methodology, the error in calculation of the horizontal pressure gradient acceleration is greatly reduced, especially in situations where the isothermal surfaces are not parallel to the vertical coordinate surfaces. The problem of aliasing and the treatment of significant temperature levels is described. © 1987 D. Reidel Publishing Company."
"6603137309;7006117817;","Vertical mode decomposition and model resolution",1986,"10.1111/j.1600-0870.1986.tb00466.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977710486&doi=10.1111%2fj.1600-0870.1986.tb00466.x&partnerID=40&md5=5162e4a3b2215ffeec1cac0ac6ecb68b","The sensitivity of the vertical mode expansion to the location of the upper boundary of the model atmosphere and to the vertical resolution is studied. The vertical modes are determined using s̀ o‐coordinate linearized primitive equation model with basic state at rest. The s̀‐levels are defined at standard pressure levels so as to avoid interpolation influence on the results. Two basic sets of experiments are performed: (a) varying the top pressure where s̀ is zero while maintaining the vertical resolution in the interior unchanged: (b) fixing the top pressure and varying the vertical resolution. The results are analysed in terms of the energetics of the projection of gridded FGGE level III‐b data at one particular grid point over tropical South America during the summer. It is found that the peak energy which occurs at an equivalent depth of the order of 220 m is approximately invariant with respect to experiments a and b. 1986 Blackwell Munksgaard"
"6701349610;7401571939;","The dynamical response of the lower atmosphere to upper atmosphere forcing and the sun-weather problem",1983,"10.1007/BF02266973","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020897730&doi=10.1007%2fBF02266973&partnerID=40&md5=05fb38d95f9d1b4170e94c0b45293739","A time-dependent, primitive-equation numerical model is used to test the hypothesis that solar variations induce changes in the distributions of basic state variables at high levels in the atmosphere, and thus induce changes in planetary-scale wave structure at lower atmospheric levels. This mechanism was proposed to explain apparent atmospheric responses to solar activity. The changes are brought about in the model by a diabatic heat source, which is taken to be a simple representation of Joule dissipative heating. Lower atmospheric wave structure is found to be insensitive to solar-induced changes in the upper atmosphere. Such changes as do occur are limited to within 25 to 40 km below the level of maximum heating, and are also quite short-lived. © 1983 Springer-Verlag."
"56135602500;57189088969;","Simulation and verification of Lake Ontario's mean state.",1981,"10.1175/1520-0485(1981)011<1548:savolo>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019385993&doi=10.1175%2f1520-0485%281981%29011%3c1548%3asavolo%3e2.0.co%3b2&partnerID=40&md5=200fe4fdba37a6fb8387c1df11494df4","A numerical dynamic model based on primitive equations, with all major current generating mechanisms taken into account, was developed for hindcasting the mean state in Lake Ontario during 1972. Two simulations, one under the respective monthly mean steady forcing and the other under the respective hourly, time-dependent atmospheric forcing, were carried out in both July and December, as representations of summer and winter. An extra run under the daily time-dependent forcing conditions of December reveals only minor deviations in model results (mostly in transient current magnitudes and phases) from those of the hourly forcing. The paper briefly describes the numerical model, summarises major current generating mechanisms in a homogeneous and in a stratified lake and shows analyses and comparisons with the observations of two December and two July simulations, one each under steady, constant atmospheric forcing, and the others under time dependent, variable atmospheric forcing. (A.B.)"
"7101980330;6701762060;","A model for computing small-scale wind variations over a water surface",1978,"10.1007/BF00123988","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0004944131&doi=10.1007%2fBF00123988&partnerID=40&md5=65f257dc4c1ea777846668493e2fdb76","Based on the primitive equations, a one-level model is described for computing surface winds under the meso-scale influences of orography, friction and heating. The effects of atmospheric stability and land-water contrasts are examined in detail. Results of testing the model with data collected during the International Field Year for the Great Lakes (IFYGL) in 1972 are given. The model is able to simulate land and lake breezes as well as meso-scale effects due to gradients in surface water temperature. Compared to simple methods of computing surface winds, use of the model reduces the vector error in estimates of surface winds by about 1.25 m s-1 on the average. © 1978 D. Reidel Publishing Company."
"57195931430;55172038400;57208086041;28267547300;55815222000;6603309733;","Life cycle of mesoscale eddies in the Gulf of Aden",2020,"10.1080/03091929.2019.1708348","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078060699&doi=10.1080%2f03091929.2019.1708348&partnerID=40&md5=6d6177372632813b880eb779f03ab6e2","The Red Sea Water is a warm and salty water produced in the Red Sea by evaporation induced by strong solar radiation. This dense water mass exits the Red Sea through the Strait of Bab El Mandeb, and enters the Gulf of Aden as a density current between 400 and 1000 metre depth. In the Gulf of Aden, in situ and satellites observations have shown the impact of the deeply reaching eddies dominating the mesoscale dynamics, on the spreading of the Red Sea Water. In this paper, we study the life cycle of these mesoscale eddies in the Gulf of Aden by using a regional primitive equation model at mesoscale resolution, and an eddy-tracking algorithm. The mesoscale anticyclonic eddies are formed at the mouth of the Gulf of Aden, and subsequently drift westward into the gulf. Mesoscale anticyclones are long-lived compared to the cyclones. The cyclones result from the interaction of anticyclones with the coast and the sloping topography. The wind stress, the bathymetry and the surrounding eddy field drive the life cycle of eddies. Finally, Kelvin and internal waves are triggered along the northern and southern coasts. © 2020 Informa UK Limited, trading as Taylor & Francis Group."
"55047044700;56593154300;6701596624;","University of Warsaw Lagrangian cloud model (UWLCM) 1.0: A modern large-eddy simulation tool for warm cloud modeling with Lagrangian microphysics",2019,"10.5194/gmd-12-2587-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068466870&doi=10.5194%2fgmd-12-2587-2019&partnerID=40&md5=1e0e0a4ac39b173ba5cbe4dc4f314084","A new anelastic large-eddy simulation (LES) model with an Eulerian dynamical core and Lagrangian particle-based microphysics is presented. The dynamical core uses the multidimensional positive-definite advection transport algorithm (MPDATA) advection scheme and the generalized conjugate residual pressure solver, whereas the microphysics scheme is based on the super-droplet method. Algorithms for coupling of Lagrangian microphysics with Eulerian dynamics are presented, including spatial and temporal discretizations and a condensation substepping algorithm. The model is free of numerical diffusion in the droplet size spectrum. Activation of droplets is modeled explicitly, making the model less sensitive to local supersaturation maxima than models in which activation is parameterized. Simulations of a drizzling marine stratocumulus give results in agreement with other LES models. It is shown that in the super-droplet method a relatively low number of computational particles is sufficient to obtain correct averaged properties of a cloud, but condensation and collision-coalescence have to be modeled with a time step of the order of 0.1. Such short time steps are achieved by substepping, as the model time step is typically around 1s. Simulations with and without an explicit subgrid-scale turbulence model are compared. Effects of modeling subgrid-scale motion of super-droplets are investigated. The model achieves high computational performance by using graphics processing unit (GPU) accelerators. © 2019 Author(s)."
"57204549008;56479267200;6701413579;","West African Monsoon: current state and future projections in a high-resolution AGCM",2019,"10.1007/s00382-018-4522-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056114128&doi=10.1007%2fs00382-018-4522-7&partnerID=40&md5=5a1cc143ca23ed985ef221276e59528b","The West African Monsoon (WAM) involves the interaction of multi-scale processes ranging from planetary to cumulus scales, which makes it challenging for coarse resolution General Circulation Models to accurately simulate WAM. The present study evaluates the ability of the high-resolution (∼ 25 km) Atmospheric General Circulation Model HiRAM to simulate the WAM and to analyze its future projections by the end of the 21st century. For the historical period, two AMIP-type simulations were conducted, one forced with observed SST from Hadley Center Sea Ice and Sea Surface Temperature dataset and the other forced with SST from the coarse resolution Earth System Model (ESM2M), which is the parent model of HiRAM, i.e. both models have the same dynamical core and similar physical parameterizations. The future projection, using the Representative Concentration Pathway 8.5 and SST from ESM2M is also conducted. A process-based evaluation is carried out to elucidate HiRAM’s ability to represent the key processes and multiscale dynamic features those define the WAM circulation. Compared to ESM2M, HiRAM better represents most of the key circulation elements at different scales, and thus more accurately represents the intensity and spatial distribution of the WAM rainfall. The position of the African easterly jet is considerably improved in HiRAM simulations, leading to the improved positioning of the WAM rainbelt and the two-cell structure of convection. The future projection of the WAM exhibits warming over the entire domain, decreasing precipitation over the southern Sahel, and increase of precipitation over the western Sahara. © 2018, The Author(s)."
"11939480800;57195351789;7402333662;7003465848;","Estimating Subseasonal Variability and Trends in Global Atmosphere Using Reanalysis Data",2018,"10.1029/2018GL080051","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058036654&doi=10.1029%2f2018GL080051&partnerID=40&md5=035e7f1ef82c0ef781a4df6a052fbd60","A new measure of subseasonal variability is introduced that provides a scale-dependent estimation of vertically and meridionally integrated atmospheric variability in terms of the normal modes of linearized primitive equations. Applied to the ERA-Interim data, the new measure shows that subseasonal variability decreases for larger zonal wave numbers. Most of variability is due to balanced (Rossby mode) dynamics but the portion associated with the inertio-gravity (IG) modes increases as the scale reduces. Time series of globally integrated variability anomalies in ERA-Interim show an increase in variability after year 2000. In recent years the anomalies have been about 2% above the 1981–2010 average. The relative increase in variability projecting on the IG modes is larger and more persistent than for the Rossby modes. Although the IG part is a small component of the subseasonal variability, it is an important effect likely reflecting the observed increase in the tropical precipitation variability. ©2018. The Authors."
"57204950288;57208122763;55910431900;","Local finite-amplitude wave activity as a diagnostic for Rossby Wave Packets",2018,"10.1175/MWR-D-18-0068.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058069247&doi=10.1175%2fMWR-D-18-0068.1&partnerID=40&md5=1c7ad945317c8f08c8a878df2e8dbfdc","Upper-tropospheric Rossby wave packets (RWPs) are important dynamical features, because they are often associated with weather systems and sometimes act as precursors to high-impact weather. The present work introduces a novel diagnostic to identify RWPs and to quantify their amplitude. It is based on the local finite-amplitude wave activity (LWA) of Huang and Nakamura, which is generalized to the primitive equations in isentropic coordinates. The new diagnostic is applied to a specific episode containing large-amplitude RWPs and compared with a more traditional diagnostic based on the envelope of the meridional wind. In this case, LWA provides a more coherent picture of the RWPs and their zonal propagation. This difference in performance is demonstrated more explicitly in the framework of an idealized barotropic model simulation, where LWAis able to follow an RWP into its fully nonlinear stage, including cutoff formation and wave breaking, while the envelope diagnostic yields reduced amplitudes in such situations. © 2018 American Meteorological Society."
"55847195100;6701653847;7202974045;7003838625;","Dispersal of Hydrothermal Vent Larvae at East Pacific Rise 9–10°N Segment",2018,"10.1029/2018JC014290","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056113941&doi=10.1029%2f2018JC014290&partnerID=40&md5=cc90908df4029ac7809ed8fbcadf83e4","A three-dimensional, primitive-equation, ocean circulation model coupled with a Lagrangian particle-tracking algorithm is used to investigate the dispersal and settlement of planktonic larvae released from discrete hydrothermal habitats on the East Pacific Rise segment at 9–10°N. Model outputs show that mean circulation is anticyclonic around the ridge segment, which consists of a northward flow along the western flank and a southward flow along the eastern flank. Those flank jets are dispersal expressways for the along-ridge larval transport and strongly affect its overall direction and spatial-temporal variations. It is evident from model results that the transform faults bounding the ridge segment and off axis topography (the Lamont Seamount Chain) act as topographic barriers to larval dispersal in the along-ridge direction. Furthermore, the presence of an overlapping spreading center and an adjacent local topographic high impedes the southward along-ridge larval transport. The model results suggest that larval recolonization within ridge-crest habitats is enhanced by the anticyclonic circulation around the ridge segment, and the overall recolonization rate is higher for larvae having a short precompetency period and an altitude above the bottom sufficient to avoid influence by the near-bottom currents Surprisingly, for larvae having a long precompetency period (>10 days), the prolonged travel time allowed some of those larvae to return to their natal vent clusters, which results in an unexpected increase in connectivity among natal and neighboring sites. Overall, model-based predictions of connectivity are highly sensitive to the larval precompetency period and vertical position in the water column. ©2018. American Geophysical Union. All Rights Reserved."
"57200001700;8285351400;","Diurnal evolution of submesoscale front and filament circulations",2018,"10.1175/JPO-D-18-0143.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055703309&doi=10.1175%2fJPO-D-18-0143.1&partnerID=40&md5=b15a44e43f83b3946cfec7e55b7ae8eb","The local circulation of submesoscale fronts and filaments can be partly understood through a horizontal momentum balance of Coriolis, a horizontal pressure gradient, and vertical diffusivity in a turbulent boundary layer, known as the turbulent thermal wind balance (TTW or T2W). T2W often reproduces the instantaneous relative vorticity and divergence of submesoscale circulations in open-ocean and shelf settings. However, a diurnal cycle in submesoscale vorticity and divergence is characterized by a non-T2W phasing: a maximum in divergence magnitude lags the maximum in vertical diffusivity (with vorticity lagging divergence). Here, an idealized model is used to solve the transient turbulent thermal wind (T3W) equations and to investigate the diurnal evolution of front and filament circulation in a 2D plane. Relative to a steady-state circulation, transient evolution can cause both instantaneous strengthening and a weaker diurnal average of the secondary circulation. The primary mechanisms controlling the diurnal variability exist in a 1D Ekman layer that imprints onto the 2D circulation. In midlatitudes, acceleration during separate phases of the diurnal cycle (from night to day and from day to night) is dominated by distinct inertial oscillation and vertically diffusive mechanisms, respectively. However, the manifestation of these dual accelerations is sensitive to latitude, boundary layer depth, and the strength of the forcing. A simple 1D model predicts the diurnal phasing of submesoscale divergence and vorticity in realistic primitive equation simulations of the southwestern Pacific and coastal California. © 2018 American Meteorological Society."
"57201901086;57203052274;46261034500;","The importance of vertical resolution in the free troposphere for modeling intercontinental plumes",2018,"10.5194/acp-18-6039-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046417138&doi=10.5194%2facp-18-6039-2018&partnerID=40&md5=d937b5c1d6a1c640584be96cf9e7c971","Chemical plumes in the free troposphere can preserve their identity for more than a week as they are transported on intercontinental scales. Current global models cannot reproduce this transport. The plumes dilute far too rapidly due to numerical diffusion in sheared flow. We show how model accuracy can be limited by either horizontal resolution (Δx) or vertical resolution (Δz). Balancing horizontal and vertical numerical diffusion, and weighing computational cost, implies an optimal grid resolution ratio (Δx/Δz)opt∼ 1000 for simulating the plumes. This is considerably higher than current global models (Δx/Δz∼ 20) and explains the rapid plume dilution in the models as caused by insufficient vertical resolution. Plume simulations with the Geophysical Fluid Dynamics Laboratory Finite-Volume Cubed-Sphere Dynamical Core (GFDL-FV3) over a range of horizontal and vertical grid resolutions confirm this limiting behavior. Our highest-resolution simulation (Δx ≈ 25km, Δz ≈ 80m) preserves the maximum mixing ratio in the plume to within 35% after 8 days in strongly sheared flow, a drastic improvement over current models. Adding free tropospheric vertical levels in global models is computationally inexpensive and would also improve the simulation of water vapor. © Author(s) 2018."
"56434851400;7004978125;","Upscale impact of mesoscale disturbances of tropical convection on convectively coupled Kelvin waves",2018,"10.1175/JAS-D-17-0178.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040930944&doi=10.1175%2fJAS-D-17-0178.1&partnerID=40&md5=a9bb6238a2ef43069f2800228e5d6567","Tropical convection associated with convectively coupled Kelvin waves (CCKWs) is typically organized by an eastward-moving synoptic-scale convective envelope with numerous embedded westward-moving mesoscale disturbances. Such a multiscale structure of tropical convection is a challenge for present-day cloud-resolving simulations and its representation in global climate models. It is of central importance to assess the upscale impact of mesoscale disturbances on CCKWs as mesoscale disturbances propagate at various tilt angles and speeds. Besides, it is still poorly understood whether the front-to-rear-tilted vertical structure of CCKWs can be induced by the upscale impact of mesoscale disturbances in the presence of upright mean heating. Here, a simple multiscale model is used to capture this multiscale structure, where mesoscale fluctuations are directly driven by mesoscale heating and synoptic-scale circulation is forced by mean heating and eddy transfer of momentum and temperature. The results show that the upscale impact of mesoscale disturbances that propagate at tilt angles of 110°-250° induces negative lower-tropospheric potential temperature anomalies in the leading edge, providing favorable conditions for shallow convection in a moist environment, while the remaining tilt-angle cases have opposite effects. Even in the presence of upright mean heating, the front-to-rear-tilted synoptic-scale circulation can still be induced by eddy terms at tilt angles of 120°-240°. In the case with fast-propagating mesoscale heating, positive potential temperature anomalies are induced in the lower troposphere, suppressing convection in a moist environment. This simple model also reproduces convective momentum transport and CCKWs in agreement with results from a recent cloud-resolving simulation. © 2018 American Meteorological Society."
"35742922300;7404678955;16177522400;12761291000;7801532509;6507671561;23981063100;36187387300;","Examining the West African Monsoon circulation response to atmospheric heating in a GCM dynamical core",2017,"10.1002/2016MS000728","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85018193135&doi=10.1002%2f2016MS000728&partnerID=40&md5=76000b0205ea81f83648c3f321866989","Diabatic heating plays a crucial role in the formation and maintenance of the West African Monsoon. A dynamical core configuration of a General Circulation Model (GCM) is used to test the influence of diabatic heating from different sources and regions on the strength and northward penetration of the monsoon circulation. The dynamical core is able to capture the main features of the monsoon flow, and when forced with heating tendencies from various different GCMs it recreates many of the differences seen between the full GCM monsoon circulations. Differences in atmospheric short-wave absorption over the Sahara and Sahel regions are a key driver of variation in the models' monsoon circulations, and this is likely to be linked to how aerosols, clouds and surface albedo are represented across the models. The magnitude of short-wave absorption also appears to affect the strength and position of the African easterly jet (AEJ), but not that of the tropical easterly jet (TEJ). The dynamical core is also used here to understand circulation changes that occur during the ongoing model development process that occurs at each modeling centre, providing the potential to trace these changes to specific alterations in model physics. © 2016. The Authors."
"57197636789;55341702500;6602418877;24503245200;57210010133;","Convection-permitting regional weather modeling with COSMO-EULAG: Compressible and anelastic solutions for a typical westerly flow over the alps",2016,"10.1175/MWR-D-15-0264.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84966417215&doi=10.1175%2fMWR-D-15-0264.1&partnerID=40&md5=2442e7d0bfb9ad99a2f7af5fc6039d95","A comparison between anelastic and compressible convection-permitting weather forecasts for the Alpine region is presented. This involves mesoscale simulation of a typical westerly flow accompanied by a passage of frontal systems as well as intense airmass convection and orographic convection. The limited-area model employing a 2.2-km horizontal grid length is driven by time-dependent boundary conditions from a coarse-resolution model. The results obtained with the anelastic and the compressible model versions show good agreement. Validations of the 10-m wind, 2-m temperature, 2-m dewpoint temperature, total cloud cover, and surface precipitation against observations for a seven-member forecast ensemble reveal only minor differences between the two configurations. The sensitivity study demonstrates only a small impact of realistic pressure perturbations (about a reference profile) on the solutions. Overall, anelastic approximation proves remarkably accurate in simulating moist mesoscale dynamics. The study has been conducted using a newly developed hybrid limited-area nonhydrostatic version of the Consortium for Small-Scale Modeling (COSMO) model. This version facilitates the use of two alternative dynamical cores: compressible (original) and anelastic (new). The new dynamical core, which is based on the Euler-Lagrangian (EULAG) solver, aims at integrating atmospheric flow equations at resolutions higher than O(1) km for steep orography. A coupler has been developed to merge the EULAG dynamical core with the COSMO numerical weather prediction framework. © 2016 American Meteorological Society."
"57203075024;7103338041;55708368700;8706262900;","On the polarization relations of diurnal and semidiurnal tide in the mesopause region",2016,"10.1016/j.jastp.2016.02.024","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84960156259&doi=10.1016%2fj.jastp.2016.02.024&partnerID=40&md5=ac0cdd7a4504e07ee673fe4fe7cec245","The polarization relations for gravity waves are well known and have proven to be very powerful for the investigation of their dynamics. Though tides are sometimes regarded as low-frequency gravity waves, their polarization relations are hardly considered. We derive the polarization relationships of tides from the primitive equations for perturbations of a dissipation-less atmosphere. The vertical wind tide is found to relate directly to temperature tide, independent of tidal structure and geometric location. On the other hand, the relation between meridional wind tide and zonal wind tide is found to depend on the horizontal derivatives of the associated geopotential perturbation, thus depending on tidal structure and geometric location. Lidar observed tides at a local station (tidal period perturbations) in the midlatitude mesopause region (80-105 km) and the Climatological Tidal Model of the Thermosphere (CTMT) based on Hough Mode Extension (HME) technique at the lidar site, both of which include the effect of dissipation, are then compared. These tidal amplitudes and phases are employed to discuss the results and implications of the derived tidal wave polarization relations. The dominance of the migrating tide follows from the phase relationship between zonal and meridional wind tides. By comparing the observed and derived vertical wind tides, we reveal qualitatively the altitude dependence of tidal wave dissipation. © 2016 Elsevier Ltd."
"57201880425;31067496800;36992744000;15765007300;7202192265;6603753099;","Dynamical Core Model Intercomparison Project (DCMIP) tracer transport test results for CAM-SE",2016,"10.1002/qj.2761","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84971519417&doi=10.1002%2fqj.2761&partnerID=40&md5=c25f07ae6455863e5673ce6e062c8721","The Dynamical Core Model Intercomparison Project (DCMIP) provides a set of tests and procedures designed to facilitate development and intercomparison of atmospheric dynamical cores in general circulation models (GCMs). Test category 1 examines the advective transport of passive tracers by three-dimensional prescribed wind velocity fields, on the sphere. These tests are applied to the Spectral Element (SE) dynamical core of the Community Atmosphere Model (CAM), the default for high-resolution simulations in the Community Earth System Model (CESM). Test case results are compared with results from the CAM-FV (Finite Volume) and MCore models where possible. This analysis serves both to evaluate the performance of CAM-SE's spectral-element tracer transport routines as well as to provide a baseline for comparison with other atmospheric dynamical cores and f or future improvements to CAM-SE itself. © 2016 Royal Meteorological Society."
"55836759700;7405763496;","Comparison of nonhydrostatic and hydrostatic dynamical cores in two regional models using the spectral and finite difference methods: dry atmosphere simulation",2016,"10.1007/s00703-015-0412-2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945143776&doi=10.1007%2fs00703-015-0412-2&partnerID=40&md5=d3c390ec001d2881560387edd1368ca8","The spectral method is generally assumed to provide better numerical accuracy than the finite difference method. However, the majority of regional models use finite discretization methods due to the difficulty of specifying time-dependent lateral boundary conditions in spectral models. This study evaluates the behavior of nonhydrostatic dynamics with a spectral discretization. To this end, Juang’s nonhydrostatic dynamical core for the National Centers for Environmental Prediction (NCEP) regional spectral model has been implemented into the Regional Model Program (RMP) of the Global/Regional Integrated Model system (GRIMs). The behavior of the nonhydrostatic RMP is validated, and compared with that of the hydrostatic core in 2-D idealized experiments: the mountain wave, rising thermal bubble, and density current experiments. The nonhydrostatic effect in the RMP is further validated in comparison with the results from the Weather Research and Forecasting (WRF) model, which uses a finite difference method. The analyses of the experimental results from the RMP generally follow the characteristics found in previous studies without any discernible difference. For example, in both the RMP and the WRF model, the eastward-tilted propagation of mountain waves is very similar in the nonhydrostatic core experiments. Both nonhydrostatic models also efficiently reproduce the motion and deformation of the warm and cold bubbles, but the RMP results contain more small-scale noise. In a 1-km real-case simulation testbed, the lee waves that originate over the eastern flank of the Korean peninsula travel further eastward in the WRF model than in the RMP. It is found that differences of small-scale wave characteristics between the RMP and WRF model are mainly from the numerical techniques used, such as the accuracy of the advection scheme and the magnitude of the numerical diffusion, rather than from discrepancies in the spatial discretization. © 2015, Springer-Verlag Wien."
"55836759700;7405763496;","Comparison of simulated precipitation over East Asia in two regional models with hydrostatic and nonhydrostatic dynamical cores",2016,"10.1175/MWR-D-15-0428.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84994171976&doi=10.1175%2fMWR-D-15-0428.1&partnerID=40&md5=cd6a2a54cc5fabf31699fb5873a2d290","This study examines the characteristics of a nonhydrostatic dynamical core compared to a corresponding hydrostatic dynamical core in the Regional Model Program (RMP) of the Global/Regional Integrated Model system (GRIMs), a spectral model for regional forecasts, focusing on simulated precipitation over Korea. This kind of comparison is also executed in the Weather Research and Forecasting (WRF) finite-difference model with the same physics package used in the RMP. Overall, it is found that the nonhydrostatic dynamical core experiment accurately reproduces the heavy rainfall near Seoul, South Korea, on a 3-km grid, relative to the results from the hydrostatic dynamical core in both models. However, the characteristics of nonhydrostatic effects on the simulated precipitation differ between the RMP and WRF Model. The RMP with the nonhydrostatic dynamical core improves the local maximum, which is exaggerated in the hydrostatic simulation. The hydrostatic simulation of the WRF Model displaces the major precipitation area toward the mountainous region along the east coast of the peninsula, which is shifted into the observed area in the nonhydrostatic simulation. In the simulation of a summer monsoonal rainfall, these nonhydrostatic effects are negligible in the RMP, but the simulated monsoonal rainfall is still influenced by the dynamical core in the WRF Model even at a 27-km grid spacing. One of the reasons for the smaller dynamical core effect in the RMP seems to be the relatively strong horizontal diffusion, resulting in a smaller grid size of the hydrostatic limit. © 2016 American Meteorological Society."
"57190230567;7404085513;55712683400;","Mechanism governing the size change of tropical cyclone-like vortices",2016,"10.2151/jmsj.2016-012","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978472780&doi=10.2151%2fjmsj.2016-012&partnerID=40&md5=46aa182488bf47ef50ea8be10f5d4fa4","To understand the basic mechanism governing the size evolution of tropical cyclones (TCs), we systematically perform numerical experiments using the primitive equation system on an f-plane. A simplified, TC-like vortex is initially given and an external forcing mimicking cumulus heating is applied to an annular region at a prescribed distance from the vortex center. Moist process and surface friction are excluded for simplification. We focus on the sensitivity of size evolution to the location of the forcing. The vortex size is defined as the radius of 15 m s–1 lowest-level wind speed (R15). The evolution of R15 depends on the forcing location, and its dependence can be understood by considering radial transport of the absolute angular momentum (AAM) at R15 due to the heat-induced secondary circulation (SC), whose structure is governed by the distribution of inertial stability. When the forcing is applied to the outer part of a vortex but still inside R15, where inertial stability is weak, the SC extends to the outside of R15 and carries AAM inward. Thus, R15 increases. Conversely, when the forcing is applied near the center of the vortex, where inertial stability is strong, the SC closes inside R15 and R15 hardly increases. These results indicate that extension of the heat-induced SC to the outside of R15 is important for the evolution of the vortex size. Moreover, the further beyond R15 the SC extends, the more the vortex size increases. This relationship is consistent with the result of the parcel trajectory analysis; the larger the extent of SC, the longer distances the parcels cover, conserving larger AAM. Finally, when the forcing is applied to the outside of R15, smaller AAM is carried outward by the SC on the inward side of the heating location, resulting in the decrease of R15. © 2016, Meteorological Society of Japan."
"7403011977;","Influence of atmospheric waves on the formation and the maintenance of the subtropical jet during the Northern Hemisphere winter-A newmethod for analyzing the responses to specific forcings",2016,"10.1002/2015JD024592","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84970028402&doi=10.1002%2f2015JD024592&partnerID=40&md5=95f47c55ee98329b2c9ad15452dafa0f","This paper introduces a new analysis method that can isolate the responses to specific forcings within meteorological data. By using the zonal mean primitive equations on the sphere, it is possible to break down the meridional circulation, the acceleration of zonal wind, temperature change, and surface pressure change into their individual contributions, which are directly associated with various forcings. This analysis technique can be applied to a wide range of problems relating to climate and its variability. To demonstrate the application of the technique, the formation andmaintenance of the subtropical jet during the Northern Hemisphere winter are examined. It is found that atmospheric waves play a crucial role in both the climatological maintenance and the day-to-day (and month-to-month) variabilities of the jet. While stationary waves are the dominant catalyst for maintaining the jet in its climatological state, synoptic waves play an important role in generating the month-to-month variability of the jet. © 2016. American Geophysical Union. All rights reserved."
"7004069241;7404187480;","The shallow-water equations in non-spherical geometry with latitudinal variation of gravity",2015,"10.1002/qj.2394","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924614567&doi=10.1002%2fqj.2394&partnerID=40&md5=6626e50d1100cb304cd68a9caadda670","The shallow-water equations in spherical geometry are well known. They are derived as a constant-density, constant-gravity specialization of the hydrostatic primitive equations for a thin layer of fluid, bounded below by topography and above by a free surface. It is shown herein that it is possible to derive an analogous set of shallow-water equations in non-spherical (but zonally symmetric) geometry using orthogonal curvilinear coordinates. This equation set is dynamically consistent, possessing conservation principles for mass, axial angular momentum, energy and potential vorticity. Furthermore, gravity is allowed to vary, as it does physically, as a function of latitude. This prepares the way for performing sensitivity tests, in an idealized framework, to assess the possible impact of latitudinal variation of gravity. Illustrative examples of models of gravity and specific non-spherical coordinate systems are given. © 2014 Royal Meteorological Society."
"55437527200;57213514245;6602084752;24478214200;57207510696;6701574871;","Importance of temporal symmetry in spatial discretization for geostrophic adjustment in semi-implicit Z-grid schemes",2015,"10.1002/qj.2344","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922789684&doi=10.1002%2fqj.2344&partnerID=40&md5=2bf6c7db21289cd509b5040ebde1d53b","Among the dynamical cores of numerical weather prediction communities, many different discretization methods can be distinguished to solve the equations governing the motions in the atmosphere numerically. One of them, the Z-grid approach, is based on solving the equations formulated in terms of divergence and vorticity on an Arakawa A-grid, a grid where all the variables are defined at the same grid points. To permit an efficient semi-implicit (SI) treatment, Z-grid schemes were proposed in the literature that first perform SI time discretization on the momentum equations formulated in terms of velocity components in order to construct from this a discretized divergence equation. This publication shows that a careful formulation of such SI Z-grid schemes is required to conserve appropriate dispersion relations for inertia-gravity, inertia-Lamb and Rossby waves. It is proven analytically for a two time-level (2TL) SI Z-grid scheme of the 1D shallow-water equations that the spatial discretization must respect temporal symmetry, meaning that the spatial discretization must be identical in the implicit and explicit parts of the scheme. If not, the discretized waves are damped or amplified and their phase and group velocity may be seriously distorted. These findings are discussed in detail and both 1D and 2D numerical tests are carried out to demonstrate that a symmetric formulation is an important modelling constraint in order to obtain an appropriate geostrophic adjustment. © 2014 Royal Meteorological Society."
"57214576588;16242524600;53980793000;","An analytical solution for linear gravity and sound waves on the sphere as a test for compressible, non-hydrostatic numerical models",2014,"10.1002/qj.2277","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908879423&doi=10.1002%2fqj.2277&partnerID=40&md5=2000e38d3c8c53acc6b2bd74377339fb","An analytical solution for the expansion of gravity and sound waves for the linearized form of the fully compressible, non-hydrostatic, shallow atmosphere Euler equations on the sphere is derived. The waves are generated by a weak initial temperature and density perturbation of an isothermal atmosphere. The derived analytical solution can be used as a benchmark to assess dynamical cores of global models based on the above-mentioned (in general nonlinear) equation system. Three different test configurations, with or without Coriolis force or additional advection, are discussed. Convergence studies of the newly developed ICOsahedral Non-hydrostatic global model (ICON) against this solution are performed. © 2013 Royal Meteorological Society."
"7004696243;7005258733;7003608266;16312087900;55712772000;16025236700;55578808274;","Theoretical aspects of variability and predictability in weather and climate systems",2014,"10.1175/BAMS-D-14-00009.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940312347&doi=10.1175%2fBAMS-D-14-00009.1&partnerID=40&md5=5f6f8d9bbc088cb092d8fce76b7c2ee5","The Research Institute for Mathematical Sciences (RIMS) of Kyoto University is one of the participants in MPE2013. This conference builds on the 50-yr history of innovative mathematical research on atmospheric predictability. Its main objectives were to review recent progress in our understanding of the variability and predictability of weather and climate systems, to enrich the exchange of information within the communities of atmospheric and climate sciences, and to attract researchers with a wide range of expertise in mathematical sciences. Several remaining challenges in the predictability of weather and climate were presented in this session, including the formulation of dynamical cores and physics schemes in global convection-permitting models, the prediction of severe weather events on global and regional scales, and forecasting on monthly to decadal time scales."
"8705630200;7006068670;23013377000;","Topographic enhancement of long waves generated by an idealized moving pressure system [Amplificación topográfica de ondas largas generadas por una perturbación atmosférica viajando]",2011,"10.3989/scimar.2011.75n3595","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960807648&doi=10.3989%2fscimar.2011.75n3595&partnerID=40&md5=012384f9084ec3dfc17941c129fa3d5f","We studied the influence of the topography on the oceanic response to a traveling atmospheric disturbance and the relevance of its propagation direction on the generation of seiche oscillations. A primitive equation ocean model was used to analyze the response of two harbors located in insular systems to a pressure disturbance. The spectral component at the frequency of fundamental harbor resonance was determined from these data for different propagation directions of the incoming atmospheric disturbance. A conceptual model of interferences of resonantly generated ocean waves was introduced in order to explain energy maxima obtained by the numerical model close to the most affected areas."
"7402725328;","Sensitivity of the Indian summer monsoon rainfall and its interannual variation to model time step",2011,"10.1016/j.atmosres.2011.01.011","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79957962715&doi=10.1016%2fj.atmosres.2011.01.011&partnerID=40&md5=66e3cc8cf59ef43c820650fe29123859","The sensitivity of the Indian summer monsoon rainfall (ISMR) and its interannual variation (IAV) to model time step is investigated using NCAR-Community Atmosphere Model version 3 (CAM3). A set of multiyear numerical experiments is performed using the atmospheric model inter-comparison project (AMIP) protocol with observed sea surface temperature (SST). The default value of time step for 64 × 128 horizontal resolution with semi-Lagrangian dynamical core is 60. min. The model overestimates the mean and underestimates the standard deviation. The mean and standard deviation of ISMR systematically decrease with decrease of time step size. With respect to observations, the mean becomes more reasonable but standard deviation becomes less reasonable. There is a decrease in precipitation over the Saudi Arabia, Maritime Continent, and northwestern Arabian Sea with decrease in time step, while over the Eastern Indian Ocean, Eastern Arabian Sea, and Eastern Bay of Bengal there is an increase in precipitation. The pattern correlation of precipitation with observation systematically increases with decrease of time step. In regard to the IAV of ISMR, simulation with 20. min time step outperforms the other time steps i.e. 60, 40, 30, and 05. min. When it is decreased to 20. min, the model bias in precipitation climatology is reduced and the low-level westerly jet over the Indian peninsular becomes more realistic. There is an overall improvement in the climatology of rainfall and winds in the vicinity of Indian summer monsoon region with 20. min time step. © 2011 Elsevier B.V."
"6603178923;7004529398;","Modeling the global circulation response and the regional response of the Arctic Ocean to the external forcing anomalies",2010,"10.1134/S0001437010060020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-78650627247&doi=10.1134%2fS0001437010060020&partnerID=40&md5=fd497a437aa0b958779176164143dbec","The problem of numerical modeling and analysis of the large-scale World Ocean circulation variability under variations of the external forcing is considered. A numerical model was developed in the INM RAS and is based on the primitive equations of the ocean circulation written in a spherical generalized σ-coordinate system. The model's equations are approximated on a grid with resolution of 2.5° × 2° × 33, and the North Pole is displaced to the continental point (60°E, 60.5°N). There are two stages for the numerical experiments. The quasi-equilibrium circulation of the World Ocean under the climatological atmospheric forcing is simulated at the first stage. The run is carried out over a period of 3000 years during which a quasi-equilibrium model regime is formed. At the second stage, the sensitivity of the model ocean circulation to the atmospheric forcing perturbations in the Southern Hemisphere is studied. According to the results, the strongest regional changes in the hydrography take place in the Arctic Ocean. Substantial changes of sea's surface height and local anomalies of the temperature and salinity are formed there. © 2010 Pleiades Publishing, Ltd."
"8205917100;6701652354;7201600456;7102023422;","Correcting for surface pressure background bias in ensemble-based analyses",2009,"10.1175/2008MWR2787.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350345429&doi=10.1175%2f2008MWR2787.1&partnerID=40&md5=4f5709457e1e794c9d8fd14714a212fe","Model error is the component of the forecast error that is due to the difference between the dynamics of the atmosphere and the dynamics of the numerical prediction model. The systematic, slowly varying part of the model error is called model bias. This paper evaluates three different ensemble-based strategies to account for the surface pressure model bias in the analysis scheme. These strategies are based on modifying the observation operator for the surface pressure observations by the addition of a bias-correction term. One estimates the correction term adaptively, while another uses the hydrostatic balance equation to obtain the correction term. The third strategy combines an adaptively estimated correction term and the hydrostatic-balance-based correction term. Numerical experiments are carried out in an idealized setting, where the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) model is integrated at resolution T62L28 to simulate the evolution of the atmosphere and the T30L7 resolution Simplified Parameterization Primitive Equation Dynamics (SPEEDY) model is used for data assimilation. The results suggest that the adaptive bias-correction term is effective in correcting the bias in the data-rich regions, while the hydrostatic-balance-based approach is effective in data-sparse regions. The adaptive bias-correction approach also has the benefit that it leads to a significant improvement of the temperature and wind analysis at the higher model levels. The best results are obtained when the two bias-correction approaches are combined. © 2009 American Meteorological Society."
"55640299900;7401594160;56804710300;6504577351;57205291254;8353015000;15119874600;","Impact of coupled nonhydrostatic atmosphere-ocean-land model with high resolution",2008,"10.1007/978-0-387-49791-4_15","https://www.scopus.com/inward/record.uri?eid=2-s2.0-82055189461&doi=10.1007%2f978-0-387-49791-4_15&partnerID=40&md5=63c3537d6083056c6c00478f2badddcc","This chapter presents basic formulation of Multi-Scale Simulator for the Geoenvironment (MSSG) which is a coupled non-hydrostatic AGCM-OGCM developed in Earth Simulator Center. MSSG is characterized by Yin-Yang grid system for both of the components, computational schemes with high accuracy in the dynamical core and high computational performance on the Earth Simulator. In particular some preliminary results from 120-h forecast experiments with MSSG are presented. © 2008 Springer-Verlag New York."
"7404187480;7004069241;","A generalized thermal wind equation and some non-separable exact solutions of the flow equations for three-dimensional spherical atmospheres",2008,"10.1002/qj.323","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57349160806&doi=10.1002%2fqj.323&partnerID=40&md5=ed371ff809331c4b660fe15b7fbd5a2d","Steady axisymmetric flows in geostrophic and cyclostrophic balance under gravity are considered for the three-dimensional Euler equations (with the spherical geopotential approximation but without the shallow-atmosphere and 'traditional' approximations). The key to analytical specification of these flows is a compatibility condition involving the zonal flow and temperature fields. This condition is a generalization of the thermal wind equation for balanced zonal flow governed by the hydrostatic primitive equations. Two examples are presented in which the temperature field is specified as non-separable two-parameter functions of latitude and height, and corresponding zonal flows are derived analytically. Such flows extend the class of known analytical solutions of the governing equations, and their usefulness in numerical model development and testing is the focus of this study. © Crown Copyright 2008."
"57213026343;7402899368;6701387222;","Genesis of the northeast Brazil upper-tropospheric cyclonic vortex: A primitive equation barotropic instability study",2007,"10.1175/JAS3893.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34247627427&doi=10.1175%2fJAS3893.1&partnerID=40&md5=f8f2f66567b82f186c80e54eccd4a604","The primitive equation barotropic unstable linear normal modes are computed using an eigenvalue approach for daily latitudinal profiles of zonal flow in the upper-tropospheric layer of 100-350 hPa before and after formation of cyclonic vortices during January 1993 and November 2001 off the coast of northeast Brazil. The wave kinetic energy equation for u- and v-motion is presented. Equations are derived to isolate the contribution of divergence and other dynamical processes in the movement and growth of unstable modes. Numerical accuracy and physical nature of unstable modes are tested. In a short span of 2-3 days, prior to formation of vortices, a progressive and a sharp intensification of the basic flow shear zone and its barotropic instability are seen with time. The horizontal structure, momentum transport, and zonal and meridional scales of the most unstable normalized wave are obtained and compared with the vortex extracted from the 200-hPa observed winds using a bandpass smoother. A close agreement is found between them. It is shown that the zonal and meridional scales of the preferred wave are related to the length scale of the shear zone. The wave is confined to the shear zone and its maximum amplitude is located at the latitude of maximum β - ūyy. The role of divergence in the movement and growth of the wave is investigated. The energetics of the unstable wave u- and v-motion is computed, and it is inferred that the energy source for the growth of wave u- (v-) motion is the energy conversion (work done by pressure force), which lies in the shear zone. It is emphasized that a deeper insight regarding the genesis of the cyclonic vortex can be gained on the basis of stability analysis of daily observed zonal flow profiles, which may not be possible using idealized or mean profiles. An explanation for nonmanifestation of the instability in the monthly mean flow is provided. © 2007 American Meteorological Society."
"12767129100;7103030382;7006094506;57189312722;","On the use of a deep pressure gradient constraint for estimating the steady state ocean circulation from hydrographic data",2006,"10.1029/2005GL024716","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33644785200&doi=10.1029%2f2005GL024716&partnerID=40&md5=086326b2090b16b0e99c0abea15bdfd4","Estimating unobserved quantities such as velocities and transport indirectly from temperature and salinity measurements is one of the best studied problems in physical oceanography. It is ill posed. The ill posedness is traditionally removed by adding prior information such as a level of no motion or a set of conservation principles. We propose to use the deep pressure gradient taken from a prognostic integration of an ocean general circulation model in primitive equations as a weak constraint when using the stationary inverse of the same model to derive transports. First results for the western boundary currents in the North Atlantic compare well with previous estimates from several studies including direct measurements. Copyright 2006 by the American Geophysical Union."
"7003626343;","Agradient velocity, vortical motion and gravity waves in a rotating shallow-water model",2004,"10.1256/qj.03.54","https://www.scopus.com/inward/record.uri?eid=2-s2.0-4844227847&doi=10.1256%2fqj.03.54&partnerID=40&md5=812da76b6980a26c18b94f21c002074f","A new approach to modelling slow vortical motion and fast inertia-gravity waves is suggested within the rotating shallow-water primitive equations with arbitrary topography. The velocity is exactly expressed as a sum of the gradient wind, described by the Bernoulli function, B, and the remaining agradient part, proportional to the velocity tendency. Then the equation for inverse potential vorticity, Q, as well as momentum equations for agradient velocity include the same source of intrinsic flow evolution expressed as a single term J(B, Q), where J is the Jacobian operator (for any steady state J(B, Q) = 0). Two components of agradient velocity are responsible for the fast inertia-gravity wave propagation similar to the traditionally used divergence and ageostrophic vorticity. This approach allows for the construction of balance relations for vortical dynamics and potential vorticity inversion schemes even for moderate Rossby and Froude numbers assuming the characteristic value of |J(B, Q)| = ε to be small. The components of agradient velocity are used as the fast variables slaved to potential vorticity that allows for diagnostic estimates of the velocity tendency, the direct potential vorticity inversion with the accuracy of ε2 and the corresponding potential vorticity-conserving agradient velocity balance model (AVBM). The ultimate limitations of constructing the balance are revealed in the form of the ellipticity condition for balanced tendency of the Bernoulli function which incorporates both known criteria of the formal stability: the gradient wind modified by the characteristic vortical Rossby wave phase speed should be subcritical. The accuracy of the AVBM is illustrated by considering the linear normal modes and coastal Kelvin waves in the f-plane channel with topography. © Royal Meteorological Society, 2004."
"7103321545;36842329100;55619302013;35776608800;55910202200;","Polar low genesis over the east coast of the Asian Continent simulated in an AGCM",2003,"10.2151/jmsj.81.697","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344035337&doi=10.2151%2fjmsj.81.697&partnerID=40&md5=a670e86596b9d9d23829256e28920309","This report shows genesis of a polar low by an AGCM without specialized initial condition. A case of polar low genesis over the eastern coast of the Asian Continent, simulated in the seasonally varying climatological SST run by an AGCM (T42L52, primitive equation spectral model with 42 wave-number and 52 layers), is presented. A polar low simulated in January 22-23 of the fourth year (Y04) integration after the 10-year period of the spin-up is studied in comparison with polar lows described in several observational studies. In January Y04, large-scale circulation systems, such as Asian winter monsoon, extratropical cyclones and upper cold lows are reasonably simulated. A typical polar low is formed in January 22 over the coastal sea area ∼1500 km west of the major extratropical cyclone that developed over the Northwestern Pacific Ocean, under the influence of a short wave trough, which propagates along the rim of an upper cold low. The polar low genesis takes place first in connection with a deepening of the surface trough, which extends westward from the major cyclone. The deepening of the surface trough in the zone of strong low-level thermal gradient over the coastal sea area suggests the important role of the low-level baroclinicity for the polar low genesis. The strong heating due to the energy supply from the sea surface contributes for the genesis of the polar low through the decreasing of the vertical stability, and the sustaining thermal gradient. Meanwhile, the heating around 700 hPa associated with the precipitation concentrated within the polar low indicates the influence of the condensation heating for the development of the polar low. Aforementioned various processes contribute together to generate and develop the polar low. The structure and the evolution process of the simulated polar low are consistent with those of the observed polar lows. It is concluded that the realistic polar low genesis takes place in the model, when the large-scale phenomena such as the upper cold low, the short-wave trough, parent major cyclone and polar air outbreak are reasonably simulated. The present study is significant in presenting an AGCM simulation of a polar low for the first time."
"6506746279;6603452175;6603414847;7102367341;","Atmosphere-sea-ice low-frequency variability with a simple model of the southern hemisphere",2003,"10.1256/qj.02.70","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0043128693&doi=10.1256%2fqj.02.70&partnerID=40&md5=7e374c14daaac0fe495c946d3991f527","A simple primitive-equation general circulation model (SGCM) is used as a representation of an 'aquaplanet' (with no orography) to model constant southern-hemisphere-winter conditions. The statistical significance of the decadal and quasi-biennial variability is first assessed in a long-time SGCM run by means of a frequency-domain statistical decomposition. The modelled long-wave atmospheric pattern is then associated with the observed southern-hemisphere 'annular mode', as suggested by previous studies using the same SGCM. A simple linear relationship between the low-level wind and the ice velocity is then introduced into the SGCM to investigate the feedbacks between the sea-ice cover and the baroclinic waves. The zonal mean state reached by the sea-ice cover in a long coupled run (a few hundred years) exhibits characteristics similar to the observations. Investigation of the low-frequency variability in the coupled simulation leads to the following results: (1) statistically significant variability is observed on interdecadal, decadal, interannual and quasi-biennial time-scales; (2) interdecadal, decadal and quasi-biennial signals are associated with the atmospheric annular mode that forces changes in the northward extent of the sea-ice cover at all Southern Ocean longitudes; (3) the interannual signal (3-6 year period) exhibits spatio-temporal patterns and propagation speed similar to the well-known 'Antarctic circumpolar wave'."
"57054407300;7004643321;","Numerical simulation of the Gulf Stream System: The Loop Current and the deep circulation",1998,"10.1029/2001JC001074","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957577500&doi=10.1029%2f2001JC001074&partnerID=40&md5=67035de30b85ebc279ad1aa28ad42060","The Loop Current and the deep circulation in the Gulf of Mexico are numerically investigated by a primitive equation, sigma coordinate ocean model with realistic surface fluxes obtained from an atmospheric forecast model. A deep cyclonic circulation, bounded by the deep basin in the eastern Gulf of Mexico, is spun up by the Loop Current; the deep cyclonic circulation is coincident with a southward current of the Loop Current eastern limb and weakens after Loop Current ring separation and cessation of the southward current. The anticyclonic, semienclosed Loop Current also induces anticyclonic lower layer columnar eddies in the eastern gulf. These lower layer eddies decouple from the upper layer Loop Current. The westward translation speed of a Loop Current ring is about 2.16-5.18 km d-1; the lower layer eddies have a higher speed and lead the rings into the central gulf. The time-averaged surface circulation of the Gulf of Mexico basin is anticyclonic, mainly because of the transport of anticyclonic vorticity by Loop Current rings in the surface layer an average lower layer cyclonic circulation occurs along the continental slope of the basin. © Copyright 2003 by the American Geophysical Union."
"6701387222;11440653000;7402899368;","A parameterization of radiative fluxes suitable for use in a statistical-dynamical model",1998,"10.1007/BF01025181","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0040757478&doi=10.1007%2fBF01025181&partnerID=40&md5=c87d2e12e9855531f1ee89c3463b7b5c","A parameterization of shortwave and longwave radiation fluxes derived from detailed radiative transfer models is included in a global primitive equation statistical-dynamical model (SDM) with two hulk atmospheric layers. The model is validated comparing the model simulations with the observed mean annual and seasonal zonally averaged climate. The results show that the simulation of the shortwave and longwave radiation fluxes matches well with the observations. The SDM variables such as surface and 500hPa temperatures, zonal winds at 250hPa and 750hPa, vertical velocity at 500hPa and precipitation are also in good agreement with the observations. A comparison between the results obtained with the present SDM and those with the previous version of the model indicates that the model results improved when the parameterization of the radiative fluxes based on detailed radiative transfer models are included into the SDM. The SDM is used to investigate its response to the greenhouse effect. Sensitivity experiments regarding the doubling of CO2 and the changing of the cloud amount and height are performed. In the case 2×CO2 the model results are consistent with those obtained from GCMs, showing a warming of the climate system. An enhancement of the greenhouse effect is also noted when the cloud layer is higher. However, an increase of the cloud amount in all the latitude belts provokes an increase of the surface temperature near poles and a decrease in all the other regions. This suggests that the greenhouse effect overcomes the albedo effect in the polar latitudes and the opposite occurs in other regions. In all the experiments the changes in the surface temperature are larger near poles, mainly in the Southern Hemisphere."
"56250448700;35330117400;6602098446;","Impacts of diabatic initialization and cumulus parameterization on numerical typhoon prediction",1998,"10.2151/jmsj1965.76.6_889","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0040427814&doi=10.2151%2fjmsj1965.76.6_889&partnerID=40&md5=8c4472513ae04fd773ccade8780030f0","Numerical experiments were conducted with a regional atmospheric model to investigate the suitability of the model for simulation/prediction of tropical cyclones (TCs). The model uses primitive equations and is similar in construction to a regional atmospheric model, called RegCM, which has been used extensively for regional climate modeling. The suitability of the model for TC study was tested in the mode of short-range forecasts to find out how well the model can reproduce TC behaviors with a special attention on their genesis and development. Objective analysis data for typhoons Ed (9018) and Flo (9019) in September 1990 were used as the input data. In addition, observed precipitation (PR) rates estimated from hourly infrared satellite measurements were used. In the prediction experiments, we focused on two aspects: One was to study the impact of data initialization. The other was to examine the sensitivity of forecast depending on the choice of two cumulus parameterizations, Kuo and relaxed Arakawa-Schubert (RAS) schemes. The initialization to the input data was done through the combination of diabatic nonlinear normal mode initialization for dynamical fields and cumulus initialization for moisture. The diabatic heating rate was determined from radiative and condensation heating rates using the input data, including observed PR rates. The initialization of moisture was done through the inversion of cumulus scheme for a specified PR rate. Positive impacts of the initialization on reproducing the behaviors of both typhoons are clearly demonstrated in the use of both cumulus schemes. In particular, the initialization results in successful simulations of initial PR field without spinup problems. Thus, the positive impact is greatest in the case of TC genesis. The reproducibility of PR by the model with RAS scheme is superior, and the RAS scheme appears more suitable than the Kuo scheme for the intensity prediction of developing typhoons. However, the use of the Kuo scheme produces better scores in mean displacement errors."
"7404976222;55505433500;56327244000;","Conservation of moist potential vorticity and down-sliding slantwise vorticity development",1996,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030391069&partnerID=40&md5=28b399d54b96a033aea61ce4b01aff3a","An accurate form of the moist potential vorticity (MPV) equation was deduced from a complete set of primitive equations. It was shown that motion in a saturated atmosphere without diabatic heating and friction conserves moist potential vorticity. This property was then used to investigate the development of vertical vorticity in moist baroclinic processes. Results show that in the framework of moist isentropic coordinate, vorticity development can result from reduction of convective stability, or convergence, or latent heat release at isentropic surfaces. However, the application of the usual analysis of moist isentropic potential vorticity is limited due to the declination of moist isentropic surfaces, and a theory of development based on z-coordinate and p-coordinate was then proposed. According to this theory, whether the atmosphere is moist-symmetrically stable or unstable, or convective stable or unstable, the reduction of convective stability, the increase of the vertical shear of horizontal wind or moist baroclinity may result in the increase of vertical vorticity, so long as the moist isentropic surface is slantwise. The larger the declination of the moist isentropic surface, the more vigorous the development of vertical vorticity. In a region with a monsoon front to the north and the warm and moist air to the south, or by the north of the front, the moist isentropes are very steep. The is the region most favorable for development of vorticities and formation of torrential rain. For a case of persistent torrential rain occurring in the middle and lower reaches of the Changjiang and Huaihe Rivers in June 11-15, 1991, moist potential vorticity analysis, especially the isobaric analysis of its vertical and horizontal components, i. e. MPV1 and MPV2, respectively, is effective for identifying synoptic systems not only in middle and high latitudes, but also in low latitudes and in the lower troposphere. It can serve as a powerful tool for the diagnosis and prediction of torrential rain."
"24786836200;57220028887;24784631000;","Numerical study of ural blocking high's effect upon Asian summer monsoon circulation and East China flood and drought",1995,"10.1007/BF02656985","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51249168180&doi=10.1007%2fBF02656985&partnerID=40&md5=ce354aa99d438cb2f9e7c76614e880f1","In terms of Kuo-Qian p-sigma incorporated coordinate five-level primitive equation spheric band (70°N-30°S) model with the Ural high's effect introduced into it as initial and boundary conditions, study is made of the high's influence on Asian summer monsoon circulation and dryness/wetness of eastern China based on case contrast and control experiments. Rusults show that as an excitation source, the blocking high produces a SE-NW stationary wavetrain with its upper-air atnicyclonic divergent circulation (just over a lower-level trough zone) precisely over the middle to lower reaches of the Changjiang River, enhancing East Asian westerly jet, a situation that contributes to perturbation growth, causing an additional secondary meridional circulation at the jet entrance, which intensifies the updraft in the monsoon area. As such, the high's presence and its excited steady wavetrain represent the large-scale key factors and acting mechanisms for the rainstorm over the Changjiang-Huaihe River catchment in the eastern part of the land. © 1995 Advances in Atmospheric Sciences."
"55740245100;","A life-cycle of nonlinear baroclinic waves represented by a simple 3- D spectral model",1995,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029414231&partnerID=40&md5=d5d89857fb81c01d5bbc0b3840ddd3f4","In this study, a life-cycle experiment for baroclinic disturbances is carried out for Simmons and Hoskins' 45° jet by integrating a three-dimensional spectral primitive equation model. The utility of the spectral representation in the vertical direction is examined for a fully nonlinear well-established phenomenon. The energy evolution and corresponding energy transformation are analyzed in the framework of the baroclinic-barotropic decomposition of atmospheric energy. It is found by this study that the important baroclinic-barotropic interactions are coupled with baroclinic instability rather than the barotropic conversion. -from Author"
"7102201685;7401581934;","Incorporating topography into the multiscale systems for the atmosphere and oceans",1993,"10.1016/0377-0265(93)90008-U","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027789901&doi=10.1016%2f0377-0265%2893%2990008-U&partnerID=40&md5=43e4949c0c9b66069c1b72726e74b2d5","Recently, new hyperbolic systems of equations that can be used to describe smooth flows accurately in both the atmosphere and oceans have been developed. These 'approximate systems' are derived by slowing down the speed of the fast waves instead of increasing their speed to infinity as in the primitive equations. The approximate systems have a number of theoretical advantages over the traditional systems. The practical implications of some of these advantages have already been demonstrated for the oceanic case. There is another advantage of the new systems that has not been discussed extensively. A model based on either of the new systems can be used to describe different scales of motion, e.g. the large, medium, or small scale. In addition, a mechanism is provided for a smooth transition between these scales. The incorporation of topography into the approximate systems has also not been discussed. To demonstrate the multiscale nature of the transformed systems in the presence of topography, numerical results from a model based on the approximate system for meteorology are compared with analytic solutions for three topographic scales. Removing the horizontal means of the density and pressure, which was necessary to obtain the proper scaling of the equations in the original papers, reduces the truncation error associated with a transformed system near steep mountains. For example, in the atmospheric case a second-order method requires only approximately 10 points across the base of the mountain to achieve a 1% relative error for any of the three topographic solutions during the relevant time scale of the associated motion. © 1993."
"6506755141;","Wintertime stratospheric anomalies- Part II: Sudden warmings",1992,"10.1007/BF02656941","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649142221&doi=10.1007%2fBF02656941&partnerID=40&md5=1d8ef2db0b2f41576e87a51df6c3d82f","The process of stratospheric sudden warmings from development of planetary waves to the sudden cooling after reversal of mean zonal circulation will be studied with the primitive equations of heat and momentum balances. It will be explained that the sudden warmings may occur only in the polar regions of winter stratosphere where zonal mean temperature decreases poleward. The heating rate in the order of major warmings is produced by developed planetary waves in the stratospheric breaking layers. The particular perturbation structure characterized by large amplitude of wave 1 together with minimum of wave 2 discovered by Labitzke (1977) is crucial for initiation of major warmings. The cooling by the same mechanism can be produced in the regions with reversed mean temperature gradient. © 1992 Advances in Atmospheric Sciences."
"7102296517;","Meridional oscillations in an idealized ocean-atmosphere system, Part I: uncoupled modes",1991,"10.1007/BF00210582","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026311797&doi=10.1007%2fBF00210582&partnerID=40&md5=4b48d367f33aefd91fbcd0951c05f181","Meridional, linear, and free modes of global, primitive-equation, ocean-atmosphere models were analyzed to see if they contain multi-year, especially decadal (∼ 10-30 years), oscillation time scale modes. A two-layer model of the global ocean and a two-level model of the global atmosphere were formulated. Both models were linearized around axially-symmetric basic states containing mean meridional circulations. The linearized perturbation system was solved as an eigenvalue problem. The operator matrix was discretized in the north-south direction with centered finite differences. Uncoupled, meridional modes of oscillation of the ocean and the atmosphere models were calculated. Calculations were performed at three grid spacings (5°, 2.5° and 1.25°) and for two types of basic states (symmetric and asymmetric). Uncoupled, free oceanic modes in the presence of mean meridional circulations have oscillation time scales ranging from two years to several centuries. Such low frequency meridional modes do not exist in the ocean model if there are no mean meridional circulations. A large number of oceanic modes are grouped around decadal oscillation time scales. All the oceanic modes have neutral growth rates. The spatial structures of some of the oceanic modes are comparable to observed spatial structures of sea surface temperature variations in the Pacific Ocean. Most years to decades variability of meridional modes of the ocean model is contained in tropical and midlatitude modes. Some oceanic modes with years to decades periods have standing oscillations in the tropics and poleward propagation of zonal velocity and layer thickness outside the tropics. Uncoupled, free atmospheric modes in the presence of mean meridional circulations have oscillation time scales ranging from a week to several decades. Such low-frequency meridional modes do not exist in the atmospere model if there are no mean meridional circulations. A large number of modes are grouped around intraseasonal time scales. Unlike the oceanic modes, the atmospheric modes are weakly unstable. Most of the intraseasonal variability of atmospheric modes is contained in tropical, midlatitude, and polar modes. Atmospheric modes with oscillation periods longer than about one year have global extent. Meridional ocean-atmospheric modes exist in the models wherever there are mean meridional circulations, i.e., tropical, midlatitude, polar, and global. Oceanic and atmospheric eigenvectors have symmetric (assymetric) latitudinal structures if their basic states are symmetric (asymmetric) around the equator. For both models, models calculated at coarser than 2.5° grid spacing do not accurately represent low-frequency variability. Scale analysis shows taht advection by tge basic state meridional velocities is the primary cause of the meridional oscillations on time scales longer than two years in the ocean model and longer than a few weeks in the atmosphere model. Meridional modes of the coupled ocean-atmosphere models are the subject of a subsequent paper. © 1991 Springer-Verlag."
"7202583200;","The atmosphere's response to the ice sheets of the Last Glacial Maximum",1990,"10.1017/s0260305500008211","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025585712&doi=10.1017%2fs0260305500008211&partnerID=40&md5=d0456bd820f4e9389def348e7360d198","A linearized, steady-state, primitive equation model can give a reasonable simulation of the GCM's stationary waves forced by the Laurentide ice sheet. The linear model analysis suggests that the mechanical effect of the changed slope of the surface, and not changes in the diabatic heating (eg the high surface albedos) or time-dependent transports that necessarily accompany the ice sheet in the GCM, is largely responsible for the ice sheet's influence. Since the meridional temperature gradient is more closely related to the surface albedo (ice extent) than to the ice volume, this suggests a mechanism by which changes in the stationary waves and, therefore, their cooling influence at low levels over the North Atlantic Ocean, can occur on time scales faster than those associated with large changes in continental ice volume. -from Authors"
"7102011703;16643212300;57217496314;","Cyclogenesis and frontogenesis",1990,"10.3402/tellusa.v42i1.11855","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025257707&doi=10.3402%2ftellusa.v42i1.11855&partnerID=40&md5=462a1de76b6fa83bccd6595e9dedf93a","Detailed linear analysis of the stability of realistic atmospheric frontal structures using the full hydrostatic primitive equations has demonstrated that such localized baroclinic zones support instability at two distinct and well-separated length scales, even when the frontal mean states have uniform potential vorticity. The first scale is associated with the well-known Charney-Eady mode of baroclinic instability with a wavelength of 3000-4000 km. The second scale has a wavelength near 1000 km and is boundary confined. The most important characteristic of the second mode is that it is completely filtered by both the quasi-geostrophic and semi-geostrophic approximations to the equations of motion. Analysis of a specific case of polar low development shows that this new mode is an important actor in at least one recurrent atmospheric dynamical process. -from Authors"
"7409687962;6602104873;","Dynamics of frontal discontinuities in the semigeostrophic theory",1989,"10.1175/1520-0469(1989)046<2166:dofdit>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024850993&doi=10.1175%2f1520-0469%281989%29046%3c2166%3adofdit%3e2.0.co%3b2&partnerID=40&md5=40ee1a7d1e3156215923069846220828","A deformation-forced, semigeostrophic (SG) frontogenesis model is extended in time to include frontal evolution after the initial formation of a discontinuity at the surface. The dynamical fields associated with the frontogenesis (eg, along front, cross front and vertical winds, Richardson number) are calculated and compare favorably to the qualitative features of atmospheric cold fronts. In particular, a strong vertical velocity jet exists at the position of the surface front in agreement with observational studies. Results from primitive equation models which include thermal and momentum diffusion are compared to the results presented here in order to assert the validity of the semigeostrophic approximation and to examine the effect of neglecting friction and mixing processes on our model. -Authors"
"6701762060;","On the sensitivity of predictions of maritime cyclogenesis to convective precipitation and sea temperature",1986,"10.1080/07055900.1986.9649240","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5544299216&doi=10.1080%2f07055900.1986.9649240&partnerID=40&md5=a59520a5c85fdb23a09209e2a06f91a6","The influences of surface fluxes and convective precipitation are investigated for two 36‐h periods of cyclogenesis over the northeastern Pacific Ocean. Three methods are tested of specifying the fraction of moisture supply that produces convective precipitation in a modified form of Kuo's (1974) parametrization scheme using an 8‐level primitive equations model.When convection is included, precipitation amounts are greater and the cyclone deepening is better predicted than when convection is not included. Predicted cyclogenesis is very sensitive to sea temperature. As the low moves over warmer water, the effect of sensible heating is to increase the moisture convergence in the atmospheric boundary layer. This increases the precipitation rates and accelerates deepening. It is concluded that the CISK mechanism plays an important role in extratropical cyclogenesis. © Taylor & Francis Group, LLC."
"57216265542;","The stratospheric winter polar vortex simulated as a material entity",1986,"10.1016/0021-9169(86)90039-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-38249039884&doi=10.1016%2f0021-9169%2886%2990039-5&partnerID=40&md5=53d7c63e2e162cff425aa229bb5283d8","In a simple 3 dimensional mechanistic primitive equation model the breakdown of the winter polar vortex is simulated. With the aid of an additional continuity equation for an inert tracer, the vortex is diagnosed as a material entity which is eroded and finally split in the course of the event. During the simulation steep gradients of mixing ratio appear, a feature observed in the real atmosphere as well. The ageostrophic flow is an essential tool for diagnosing the evolution of the polar vortex as a material entity. © 1986."
"7202162591;57212891405;","Low-order intermediate models: bifurcation, recurrence and solvability.",1986,"10.1175/1520-0469(1986)043<2360:LOIMBR>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022823250&doi=10.1175%2f1520-0469%281986%29043%3c2360%3aLOIMBR%3e2.0.CO%3b2&partnerID=40&md5=a0eadc0f07bc13514a9695ca4cf4065f","Intermediate models have played and continue to play a fundamental role in the atmospheric sciences. Recently, Gent and McWilliams have extended the study of intermediate models to include low-order models. Their models were specifically introduced to eliminate gravity wave oscillations. This article is concerned with the bifurcations present in low-order intermediate models. We discover that all of the intermediate models exhibit the same sequence of bifurcations. The information to support our claim is necessarily finite but we believe it to be definitive. Further, all intermediate models, because of the form of their underlying evolution equations, have solvability surfaces. The solvability surfaces and bifurcations define limits of model validity. In general, the models considered here do not conserve energy and therefore have unbounded solutions. For a large range of parameter values, however, all solutions remain in a finite region of phase space inside the central core of the solvability surface. Prior to the systems having solvability difficulties, a new 'chaotic attractor' appears in the phase space of all of the models. This new chaotic attractor appears in the balance equation model for parameter values which are within a few percent of those parameter values for which the gravity wave attractor appears in the primitive equation low-order model of Lorenz. In the other models, this new attractor is also present and has a very similar structure.-Authors"
"55665411300;7801439941;","Nonlinear forcing of planetary scale waves by amplifying unstable baroclinic eddies generated in the troposphere.",1985,"10.1175/1520-0469(1985)042<1991:NFOPSW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022266331&doi=10.1175%2f1520-0469%281985%29042%3c1991%3aNFOPSW%3e2.0.CO%3b2&partnerID=40&md5=dbb6a73e6feae0de4de5b9a73941a298","A global, spectral, primitive equation circulation model is used to study this phenomenon for two initial mean zonal wind fields having idealized meridional distributions, but realistic vertical variations. For the cases treated here, both the direct transfer of kinetic energy from intermediate scales of motion, and baroclinic conversion of available potential energy to kinetic energy within a given planetary wave, are important. It appears that direct kinetic energy transfer to the long waves can be inhibited by heat transport. Planetary wave amplitudes are considerably enhanced by wave-wave coupling over what they would be due to baroclinic instability of the zonally averaged state to planetary wave disturbances. Nonlinear forcing in the troposphere may be an important mechanism for generating eastward propagating planetary waves observed in the Southern Hemisphere. The planetary wave forcing terms have relative maxima near the tropopause. Such nonlinear forcing near the tropopause may explain the lack of coherence between the troposphere and stratosphere observed in eastward traveling waves with zonal wavenumbers 1 and 2. -from Authors"
"7003796057;6603732209;7404556964;","The response of a nonlinear, time‐dependent, baroclinic model of the atmosphere to tropical thermal forcing",1984,"10.1002/qj.49711046611","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021567922&doi=10.1002%2fqj.49711046611&partnerID=40&md5=24317df229aa73bfb4e084981e3c805f","A multi‐level, sigma coordinate, primitive equation atmospheric model has been utilized to study both the tropical and extratropical response to an isolated region of steady thermal forcing in the tropics. The nonlinear response during the first 28 days of the simulation is described. The response can be generally characterized by two distinct components. The first component is a quasi‐stationary disturbance which extends eastward and poleward away from the source region along a ‘great circle’ path. The structure of this disturbance is essentially barotropic away from the source region. The second component is a growing baroclinic wave propagating zonally at mid‐latitudes. Significantly, this disturbance is apparently the result of baroclinic instability induced by the quasi‐stationary wavetrain. The discussion is predominantly heuristic in form and relies heavily on graphical presentation and quasi‐geostrophic theory to interpret the response and individual components of the thermodynamic energy and momentum equations. Copyright © 1984 Royal Meteorological Society"
"7005793728;","Linear and nonlinear aspects of snow albedo feedbacks in atmospheric models ( North America).",1981,"10.1029/JC086iC08p07411","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019685784&doi=10.1029%2fJC086iC08p07411&partnerID=40&md5=08bd30626b8aad2f6b4cae19d6a9402a","Namias' hypothesis, that anomalous snowcover on the eastern side of the North American continent can generate an anomalous east coast low pressure system and an anomalous inland high pressure system, is consistent with the time-averaged anomalous response from a nonlinear, primitive equation channel model with an idealized, flat land-sea arrangement. An attempt to understand and describe this anomalous response in the nonlinear model as a linear response to anomalous diabatic heating was largely unsuccessful, primarily because the anomalous eddy fluxes were also important. -from Author"
"56434129200;56856305600;57214576588;7404732357;53980793000;16242524600;","The upper-atmosphere extension of the ICON general circulation model (version: Ua-icon-1.0)",2019,"10.5194/gmd-12-3541-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070814371&doi=10.5194%2fgmd-12-3541-2019&partnerID=40&md5=8ec9ff91a5ebc3239145965e2bb0f215","How the upper-atmosphere branch of the circulation contributes to and interacts with the circulation of the middle and lower atmosphere is a research area with many open questions. Inertia-gravity waves, for instance, have moved in the focus of research as they are suspected to be key features in driving and shaping the circulation. Numerical atmospheric models are an important pillar for this research. We use the ICOsahedral Non-hydrostatic (ICON) general circulation model, which is a joint development of the Max Planck Institute for Meteorology (MPI-M) and the German Weather Service (DWD), and provides, e.g., local mass conservation, a flexible grid nesting option, and a non-hydrostatic dynamical core formulated on an icosahedral-triangular grid. We extended ICON to the upper atmosphere and present here the two main components of this new configuration named UA-ICON: an extension of the dynamical core from shallow- to deep-atmosphere dynamics and the implementation of an upper-atmosphere physics package. A series of idealized test cases and climatological simulations is performed in order to evaluate the upper-atmosphere extension of ICON. © Author(s) 2019."
"56196768100;7003991093;","The effects of gravity on the climate and circulation of a terrestrial planet",2019,"10.1002/qj.3582","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071829376&doi=10.1002%2fqj.3582&partnerID=40&md5=3a64cc716e139889f2fa8cf1822e4129","The climate and circulation of a terrestrial planet are governed by, among other things, the distance to its host star, its size, rotation rate, obliquity, atmospheric composition and gravity. Here we explore the effects of the last of these, the Newtonian gravitational acceleration, on its atmosphere and climate. We first demonstrate that, if the atmosphere obeys the hydrostatic primitive equations, which are a very good approximation for most terrestrial atmospheres, and if the radiative forcing is unaltered, changes in gravity have no effect at all on the circulation except for a vertical rescaling. That is to say, the effects of gravity may be completely scaled away and the circulation is unaltered. However, if the atmosphere contains a dilute condensible that is radiatively active, such as water or methane, then an increase in gravity will generally lead to a cooling of the planet because the total path length of the condensible will be reduced as gravity increases, leading to a reduction in the greenhouse effect. Furthermore, the specific humidity will decrease, leading to changes in the moist adiabatic lapse rate, in the Equator-to-Pole heat transport, and in the surface energy balance because of changes in the sensible and latent fluxes. These effects are all demonstrated both by theoretical arguments and by numerical simulations with moist and dry general circulation models. © 2019 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"55358305000;7402270607;57003957600;6602628253;57205512050;","Dynamical downscaling the impact of spring Western US land surface temperature on the 2015 flood extremes at the Southern Great Plains: effect of domain choice, dynamic cores and land surface parameterization",2019,"10.1007/s00382-019-04630-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060330331&doi=10.1007%2fs00382-019-04630-6&partnerID=40&md5=b00c651ef072b76326392153038663c5","Recent studies have shown that spring land surface temperature (LST) and subsurface temperature (SUBT) over the high elevation areas in the western US (WUS) have significant impacts on the downstream summer droughts/floods in North America. In this paper, both the National Centers for Environmental Prediction—Global Forecast System (NCEP-GFS) general circulation model (GCM) and the weather research and forecasting (WRF) regional climate model (RCM) are employed, where RCM scenarios utilized initial and lateral boundary conditions derived from the corresponding NCEP-GFS scenarios. Here we use a late spring flood in the US Southern Great Plains (SGP) case to examine whether simulation of the LST/SUBT downstream effects is sensitive to the domain size choice, change in dynamical cores within the same model, as well as to the representation of surface processes parameterizations. Although all RCM experiments with different settings simulate reasonably geographical patterns of observed LST and precipitation anomalies, we found that the choice of the domain size is crucial for proper downscaling the LST/SUBT downstream effects to accurately produce the observed precipitation/LST anomalies over the SGP/WUS, respectively, along with the associated large-scale features. The southern boundary location has been identified to be crucial in producing the SGP Low Level Jet strength, which in turn brings more moisture from the Gulf of Mexico to the SGP and thereby resulting in a better simulation of the precipitation anomaly in that area. The sensitivity of the simulation of the LST/SUBT downstream effect to dynamical cores is assessed by inter-comparing the Non-hydrostatic Mesoscale Model (NMM) and the Advanced Research WRF dynamic cores. We find NMM was better at generating the large-scale eastward wave train, a crucial process associated with the LST/SUBT downstream effect. Meanwhile, this study also shows that the LST/SUBT downstream effects were not significantly dependent on the surface process parameterizations, although the Simplified Simple Biosphere model version 3 (SSiB3) highlighted a better performance over SSiB2. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature."
"24492504500;57208347885;","Numerical solution of the conditionally averaged equations for representing net mass flux due to convection",2019,"10.1002/qj.3490","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064556816&doi=10.1002%2fqj.3490&partnerID=40&md5=a7fb98dff40fa071ff980181d0020c3d","The representation of subgrid-scale convection is a weak aspect of weather and climate prediction models and the assumption that no net mass is transported by convection in parametrizations is increasingly unrealistic as models enter the grey zone, partially resolving convection. The solution of conditionally averaged equations of motion (multifluid equations) is proposed in order to avoid this assumption. Separate continuity, temperature, and momentum equations are solved for inside and outside convective plumes, which interact via mass-transfer terms, drag, and by a common pressure. This is not a convection scheme that can be used with an existing dynamical core—this requires a whole new model. This article presents stable numerical methods for solving the multifluid equations, including large transfer terms between the environment and plume fluids. Without transfer terms, the two fluids are not sufficiently coupled and solutions diverge. Two transfer terms are presented, which couple the fluids together in order to stabilize the model: diffusion of mass between the fluids (similar to turbulent entrainment) and drag between the fluids. Transfer terms are also proposed to move buoyant air into the plume fluid and vice versa as would be needed to represent initialization and termination of subgrid-scale convection. The transfer terms are limited (clipped in size) and solved implicitly in order to achieve bounded, stable solutions. Results are presented for a well-resolved warm bubble with rising air being transferred to the plume fluid. For stability, equations are formulated in advective rather than flux form and solved using bounded finite-volume methods. Discretization choices are made to preserve boundedness and conservation of momentum and energy when mass is transferred between fluids. The formulation of transfer terms in order to represent subgrid convection is the subject of future work. © 2019 Royal Meteorological Society"
"36179077700;15765007300;52263850600;13406399300;7202192265;36992744000;31067496800;57201880425;57202522440;6603565405;6602230359;6603218374;7202208382;57192468922;11939929300;6603247427;16242524600;23967739600;7004134577;36762751600;7801332133;6701339411;25647939800;56520853700;55622628300;55189671700;7004676489;6701335949;","DCMIP2016: The splitting supercell test case",2019,"10.5194/gmd-12-879-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062564133&doi=10.5194%2fgmd-12-879-2019&partnerID=40&md5=cc51204206970141879920c99135375a","This paper describes the splitting supercell idealized test case used in the 2016 Dynamical Core Model Intercomparison Project (DCMIP2016). These storms are useful test beds for global atmospheric models because the horizontal scale of convective plumes is O(1 km), emphasizing non-hydrostatic dynamics. The test case simulates a supercell on a reduced-radius sphere with nominal resolutions ranging from 4 to 0.5 km and is based on the work of Klemp et al. (2015). Models are initialized with an atmospheric environment conducive to supercell formation and forced with a small thermal perturbation. A simplified Kessler microphysics scheme is coupled to the dynamical core to represent moist processes. Reference solutions for DCMIP2016 models are presented. Storm evolution is broadly similar between models, although differences in the final solution exist. These differences are hypothesized to result from different numerical discretizations, physics-dynamics coupling, and numerical diffusion. Intramodel solutions generally converge as models approach 0.5 km resolution, although exploratory simulations at 0.25 km imply some dynamical cores require more refinement to fully converge. These results can be used as a reference for future dynamical core evaluation, particularly with the development of non-hydrostatic global models intended to be used in convective-permitting regimes. © 2019 Author(s)."
"6506756436;7003554893;","The coupling of deep convection with the resolved flow via the divergence of mass flux in the IFS",2019,"10.1002/qj.3528","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064715568&doi=10.1002%2fqj.3528&partnerID=40&md5=b3d7e4841404fb2404d95cc2182d7c6d","The resolution of the European Centre for Medium-range Weather Forecast (ECMWF) integrated forecast system (IFS) is expected to reach 5 km in the coming decade. Assumptions in the parametrization of deep convection, such as that all of the compensating environmental flow occurs in the grid column, i.e. the convective and environmental mass fluxes cancel each other in term of mass transport, have to be challenged. In this paper, we further develop the original concept of separating the convective updraught from the subsiding branch of the overturning convective circulation and apply it to the global hydrostatic equations of the IFS. In practice, this constitutes a revised convection–dynamics coupling where the mass flux subsidence of the dynamical variables is not computed locally by the convection scheme, but instead is recomputed from the revised continuity equation and is effective through the semi-Lagrangian advection of the dynamical core. Therefore horizontal divergence/convergence is also generated in the dynamics at the top/bottom of the convective columns, thus adding to the representation of deep convection a three-dimensional character which is not present in traditional schemes. The proposed physics–dynamics coupling is intended to be applicable to any mass flux convection scheme and within any regional or global model. We first demonstrate the accuracy of the revised physics–dynamics coupling in terms of global temperature and moisture budgets. The potential impact of the coupling on the convective organization is demonstrated for an idealized squall line case at high horizontal resolution using the small planet testbed. Model reforecasts at 9 km and 5 km resolution confirm the viability of the method in terms of forecast skill and model climate. However, the model impacts are limited as the main factor that still determines the convective stabilization and organization is the current conceptual model of subgrid mass flux which, actually, remains unchanged. © 2019 Royal Meteorological Society"
"57192468922;57212665260;11939929300;","Towards an Unstaggered Finite-Volume Dynamical Core With a Fast Riemann Solver: 1-D Linearized Analysis of Dissipation, Dispersion, and Noise Control",2018,"10.1029/2018MS001361","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054398864&doi=10.1029%2f2018MS001361&partnerID=40&md5=a7052f8d3cecb11f3f32cb884417154a","Many computational fluid dynamics codes use Riemann solvers on an unstaggered grid for finite volume methods, but this approach is computationally expensive compared to existing atmospheric dynamical cores equipped with hyper-diffusion or other similar relatively simple diffusion forms. We present a simplified Low Mach number Approximate Riemann Solver (LMARS), made computationally efficient through assumptions appropriate for atmospheric flows: low Mach number, weak discontinuities, and locally uniform sound speed. This work will examine the dissipative and dispersive properties of LMARS using Von Neumann linearized analysis to the one-dimensional linearized shallow water equations. We extend these analyses to higher-order methods by numerically solving the Fourier-transformed equations. It is found that the pros and cons due to grid staggering choices diminish with high-order schemes. The linearized analysis is limited to modal, smooth solutions using simple numerical schemes, and cannot analyze solutions with discontinuities. To address this problem, this work presents a new idealized test of a discontinuous wave packet, a single Fourier mode modulated by a discontinuous square wave. The experiments include studies of well-resolved and (near) grid-scale wave profiles, as well as the representation of discontinuous features and the results are validated against the Von Neumann analysis. We find the higher-order LMARS produces much less numerical noise than do inviscid unstaggered and especially staggered schemes while retaining accuracy for better-resolved modes. ©2018. The Authors."
"16042493100;7004093651;","A Lagrangian vertical coordinate version of the ENDGame dynamical core. Part I: Formulation, remapping strategies, and robustness",2018,"10.1002/qj.3368","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054480602&doi=10.1002%2fqj.3368&partnerID=40&md5=b8b7779a98bb47e2156c12ebc67904b6","Previous work provides evidence that Lagrangian conservation and related properties of a numerical model dynamical core can be improved by the use of a Lagrangian or quasi-Lagrangian vertical coordinate (LVC). Most previous model developments based on this idea have made the hydrostatic approximation. Here the LVC is implemented in a non-hydrostatic compressible Euler equation dynamical core using almost identical numerical methods to ENDGame, the operational dynamical core of the Met Office atmospheric Unified Model. This enables a clean comparison of LVC and height-coordinate versions of the dynamical core using numerical methods that are as similar as possible. Since Lagrangian surfaces distort over time, model level heights are continually reset to certain “target levels” and the values of model fields are remapped onto their new locations. Different choices for these target levels are discussed, along with remapping strategies that focus on different conservation or balance properties. Sample results from a baroclinic instability test case are presented. The LVC formulation is found to be rather less robust than the height-coordinate version; some reasons for this are discussed. © 2018 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"55973319300;57203084853;","Quantifying isentropic mixing linked to Rossby wave breaking in a modified Lagrangian coordinate",2018,"10.1175/JAS-D-17-0204.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044671121&doi=10.1175%2fJAS-D-17-0204.1&partnerID=40&md5=fce309b62bb43bf104ee2762d5b61508","Isentropic mixing is an important process for the distribution of chemical constituents in the mid- to high latitudes. A modified Lagrangian framework is applied to quantify the mixing associated with two distinct types of Rossby wave breaking (i.e., cyclonic and anticyclonic). In idealized numerical simulations, cyclonic wave breaking (CWB) exhibits either comparable or stronger mixing than anticyclonic wave breaking (AWB). Although the frequencies of AWB and CWB both have robust relationships with the jet position, this asymmetry leads to CWB dominating mixing variability related to the jet shifting. In particular, when the jet shifts poleward the mixing strength decreases in areas of the midlatitude troposphere and also decreases on the poleward side of the jet. This is due to decreasing CWB occurrence with a poleward shift of the jet. Across the tropopause, equatorward of the jet, where AWB mostly occurs and CWB rarely occurs, the mixing strength increases as AWB occurs more frequently with a poleward shift of the jet. The dynamical relationship above is expected to be relevant both for internal climate variability, such as the El Niño-Southern Oscillation (ENSO) and the annular modes, and for future climate change that may drive changes in the jet position. © 2018 American Meteorological Society."
"57196369879;7004372110;55641786300;6602410438;57195422828;55916149100;25027021800;","The dynamical core of the Aeolus 1.0 statistical-dynamical atmosphere model: Validation and parameter optimization",2018,"10.5194/gmd-11-665-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042672779&doi=10.5194%2fgmd-11-665-2018&partnerID=40&md5=df1836f81d88ba0b4d8852eff55b9878","We present and validate a set of equations for representing the atmosphere's large-scale general circulation in an Earth system model of intermediate complexity (EMIC). These dynamical equations have been implemented in Aeolus 1.0, which is a statistical-dynamical atmosphere model (SDAM) and includes radiative transfer and cloud modules (Coumou et al., 2011; Eliseev et al., 2013). The statistical dynamical approach is computationally efficient and thus enables us to perform climate simulations at multimillennia timescales, which is a prime aim of our model development. Further, this computational efficiency enables us to scan large and high-dimensional parameter space to tune the model parameters, e.g., for sensitivity studies.<br><br>Here, we present novel equations for the large-scale zonal-mean wind as well as those for planetary waves. Together with synoptic parameterization (as presented by Coumou et al., 2011), these form the mathematical description of the dynamical core of Aeolus 1.0.<br><br>We optimize the dynamical core parameter values by tuning all relevant dynamical fields to ERA-Interim reanalysis data (1983-2009) forcing the dynamical core with prescribed surface temperature, surface humidity and cumulus cloud fraction. We test the model's performance in reproducing the seasonal cycle and the influence of the El Niño-Southern Oscillation (ENSO). We use a simulated annealing optimization algorithm, which approximates the global minimum of a high-dimensional function.<br><br>With non-tuned parameter values, the model performs reasonably in terms of its representation of zonal-mean circulation, planetary waves and storm tracks. The simulated annealing optimization improves in particular the model's representation of the Northern Hemisphere jet stream and storm tracks as well as the Hadley circulation.<br><br>The regions of high azonal wind velocities (planetary waves) are accurately captured for all validation experiments. The zonal-mean zonal wind and the integrated lower troposphere mass flux show good results in particular in the Northern Hemisphere. In the Southern Hemisphere, the model tends to produce too-weak zonal-mean zonal winds and a too-narrow Hadley circulation. We discuss possible reasons for these model biases as well as planned future model improvements and applications. © Author(s) 2018."
"7003532926;56828803500;6602333928;6602387822;55015342700;","Reproduction of World Ocean Circulation by the CORE-II Scenario with the Models INMOM and INMIO",2018,"10.1134/S0001433817060123","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042484217&doi=10.1134%2fS0001433817060123&partnerID=40&md5=694e52f07cc93143f0d39d6184024101","The results of simulations performed by the CORE-II scenario using the two Russian OGCMs, INMOM and INMIO, are presented. The models use different coordinate systems in the basic set of primitive equations and different numerical techniques. Both models are used as oceanic components of the INM RAS coupled models. Simulations have shown that reproducing ocean circulation using both models agrees with observations and simulations by other models. In general, the INMOM slightly underestimates the meridional heat transport in the ocean when compared to the INMIO model and climatic estimations. However, the INMIO yields a higher bias in temperature than the INMOM. © 2018, Pleiades Publishing, Ltd."
"57200333124;57192983332;7006399667;15724418700;","The emergence of shallow easterly jets within QBO westerlies",2018,"10.1175/JAS-D-17-0108.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040933805&doi=10.1175%2fJAS-D-17-0108.1&partnerID=40&md5=53e106f032d7c8c2498fea3b666a4a37","A configuration of an idealized general circulation model has been obtained in which a deep, stratospheric, equatorial, westerly jet is established that is spontaneously and quasi-periodically disrupted by shallow easterly jets. Similar to the disruption of the quasi-biennial oscillation (QBO) observed in early 2016, meridional fluxes of wave activity are found to play a central role. The possible relevance of two feedback mechanisms to these disruptions is considered. The first involves the secondary circulation produced in the shear zones on the upper and lower flanks of the easterly jet. This is found to play a role in maintaining the aspect ratio of the emerging easterly jet. The second involves the organization of the eddy fluxes by the mean flow: the presence of a weak easterly anomaly within a tall, tropical, westerly jet is demonstrated to produce enhanced and highly focused wave activity fluxes that reinforce and strengthen the easterly anomalies. The eddies appear to be organized by the formation of strong potential vorticity gradients on the subtropical flanks of the easterly anomaly. Similar wave activity and potential vorticity structures are found in the ERA-Interim for the observed QBO disruption, indicating this second feedback was active then. © 2018 American Meteorological Society."
"55940118700;28267547300;57204402515;6602252279;8295005100;37037577800;56209544000;7003993113;","Surface signature of Mediterranean water eddies in a long-term high-resolution simulation",2017,"10.1016/j.dsr.2017.10.001","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85035090411&doi=10.1016%2fj.dsr.2017.10.001&partnerID=40&md5=2c8241844fcf02c11c500a3673b9d999","We study the surface signatures of Mediterranean water eddies (Meddies) in the context of a regional, primitive equations model simulation (using the Regional Oceanic Modeling System, ROMS). This model simulation was previously performed to study the mean characteristics and pathways of Meddies during their evolution in the Atlantic Ocean. The advantage of our approach is to take into account different physical mechanisms acting on the evolution of Meddies and their surface signature, having full information on the 3D distribution of all physical variables of interest. The evolution of around 90 long-lived Meddies (whose lifetimes exceeded one year) was investigated. In particular, their surface signature was determined in sea-surface height, temperature and salinity. The Meddy-induced anomalies were studied as a function of the Meddy structure and of the oceanic background. We show that the Meddies can generate positive anomalies in the elevation of the oceanic free-surface and that these anomalies are principally related to the Meddies potential vorticity structure at depth (around 1000 m below the sea-surface). On the contrary, the Meddies thermohaline surface signatures proved to be mostly dominated by local surface conditions and little correlated to the Meddy structure at depth. This work essentially points out that satellite altimetry is the most suitable approach to track subsurface vortices from observations of the sea-surface. © 2017 Elsevier Ltd"
"56828803500;6603178923;57208310824;","Technique for Simulation of Black Sea Circulation with Increased Resolution in the Area of the IO RAS Polygon",2017,"10.1134/S0001437017060054","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85043991337&doi=10.1134%2fS0001437017060054&partnerID=40&md5=219c39cdfaa02bc49d0609ceb75b4a51","A numerical technique is presented for simulating the hydrophysical fields of the Black Sea on a variable-step grid with refinement in the area of IO RAS polygon. Model primitive equations are written in spherical coordinates with an arbitrary arrangement of poles. In order to increase the horizontal resolution of the coastal zone in the area of the IO RAS polygon in the northeastern part of the sea near Gelendzhik, one of the poles is placed at a land point (38.35° E, 44.75° N). The model horizontal resolution varies from 150 m in the area of the IO RAS polygon to 4.6 km in the southwestern part of the Black Sea. The numerical technique makes it possible to simulate a large-scale structure of Black Sea circulation as well as the meso- and submesoscale dynamics of the coastal zone. In order to compute the atmospheric forcing, the results of the regional climate model WRF with a resolution of about 10 km in space and 1 h in time are used. In order to demonstrate the technique, Black Sea hydrophysical fields for 2011–2012 and a passive tracer transport representing self-cleaning of Gelendzhik Bay in July 2012 are simulated. © 2017, Pleiades Publishing, Inc."
"57195219580;7102132806;7202619752;","Variability of precipitation along cold fronts in idealized baroclinic waves",2017,"10.1175/MWR-D-16-0409.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026317328&doi=10.1175%2fMWR-D-16-0409.1&partnerID=40&md5=56b7dd8a5137552670df04a71915d953","Precipitation patterns along cold fronts can exhibit a variety of morphologies including narrow cold-frontal rainbands and core-and-gap structures. A three-dimensional primitive equation model is used to investigate alongfront variability of precipitation in an idealized baroclinic wave. Along the poleward part of the cold front, a narrow line of precipitation develops. Along the equatorward part of the cold front, precipitation cores and gaps form. The difference between the two evolutions is due to differences in the orientation of vertical shear near the front in the lower troposphere: at the poleward end the along-frontal shear is dominant and the front is in near-thermal wind balance, while at the equatorward end the cross-frontal shear is almost as large. At the poleward end, the thermal structure remains erect with the front well defined up to the midtroposphere, hence updrafts remain erect and precipitation falls in a continuous line along the front. At the equatorward end, the cores form as undulations appear in both the prefrontal and postfrontal lighter precipitation, associated with vorticity maxima moving along the front on either side. Cross-frontal winds aloft tilt updrafts, so that some precipitation falls ahead of the surface cold front, forming the cores. Sensitivity simulations are also presented in which SST and roughness length are varied between simulations. Larger SST reduces cross-frontal winds aloft and leads to a more continuous rainband. Larger roughness length destroys the surface wind shift and thermal gradient, allowing mesovortices to dominate the precipitation distribution, leading to distinctive and irregularly shaped, quasi-regularly spaced precipitation maxima. © 2017 American Meteorological Society."
"52263850600;15765007300;7004093651;57193921169;","An energy-conserving restoration scheme for the shallow-water equations",2016,"10.1002/qj.2713","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957659906&doi=10.1002%2fqj.2713&partnerID=40&md5=0e6542573f6dd67f0e6699b77c3e1387","The numerical methods that solve the governing equations in an atmospheric dynamical core are designed to dissipate potential enstrophy and prevent the build-up of kinetic energy at the grid scale. A side-effect of this is the dissipation of total energy which should be conserved. Energy fixers are used in climate models to replace the dissipated energy by modifying the temperature in the thermodynamic equation, and stochastic backscatter schemes have also been developed for use in weather prediction models. Here, we present the first steps towards designing a deterministic energy-conserving restoration scheme that considers the conversion of kinetic energy to heat, replacing kinetic energy lost due to model error, and the backscatter of kinetic energy. The energy-conserving restoration scheme (ECRS) is presented in the context of the shallow-water equations on the sphere. It is designed to be used with any existing shallow-water equation scheme (called the preliminary scheme) which can adequately dissipate potential enstrophy, and in this article we use a semi-implicit semi-Lagrangian (SISL) scheme. For each prognostic variable, a spatial pattern is chosen; this is added to the preliminary scheme solution, and the amount added is calculated to ensure energy conservation. Results from short-term test cases show that ECRS and SISL have very similar error norms. For long-term simulations, ECRS conserves energy to a good approximation whereas SISL dissipates energy. © 2016 Royal Meteorological Society."
"56900391700;6701718281;36179077700;15765007300;","A balanced tropical cyclone test case for AGCMs with background vertical wind shear",2015,"10.1175/MWR-D-14-00366.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84944128063&doi=10.1175%2fMWR-D-14-00366.1&partnerID=40&md5=f69c85d5cefe0b9c002fd9fdc0341060","This paper presents a balanced tropical cyclone (TC) test case designed to improve current understanding of how atmospheric general circulation model (AGCM) configurations affect simulated TC development and behavior. It consists of an analytic initial condition comprising two independently balanced components. The first provides a vortical TC seed, while the second adds a planetary-scale zonal flow with height-dependent velocity and imposes background vertical wind shear (VWS) on the TC seed. The environmental flow satisfies the steady-state hydrostatic primitive equations in spherical coordinates and is in balance with other background field variables (e.g., temperature, surface geopotential). The evolution of idealized TCs in the test case framework is illustrated in 10-day simulations performed with the Community Atmosphere Model, version 5.1.1 (CAM 5.1.1). Environmental wind profiles with different magnitudes, directions, and vertical inflection points are applied to ensure that the technique is robust to changes in the VWS characteristics. The well-known shear-induced intensity change and structural asymmetry in tropical cyclones are well captured. Sensitivity of TC evolution to small perturbations in the initial vortex is also quantitatively addressed to validate the numerical robustness of the technique. It is concluded that the enhanced TC test case can be used to evaluate the impact of model choice (e.g., resolution, physical parameterizations) on the simulation and representation of TC-like vortices in AGCMs. © 2015 American Meteorological Society."
"36637539100;9244992800;","Formation and maintenance of the tropical cold-point tropopause in a dry dynamic-core GCM",2015,"10.1175/JAS-D-14-0338.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943404079&doi=10.1175%2fJAS-D-14-0338.1&partnerID=40&md5=758958328da65067faefc45b7ea160ef","The formation of the tropical cold-point tropopause (CPT) is examined using a dry primitive equation model driven by the Held-Suarez forcing. Without moist and realistic radiative processes, the dry model successfully reproduces the zonal-mean structure of the CPT. The modeled CPT is appreciably colder (~10 K) than the prescribed equilibrium temperature, and it is maintained by upwelling in the tropical upper troposphere and lower stratosphere (UTLS). A transient simulation starting from an axisymmetric steady state without the CPT shows that the evolution and maintenance of the CPT are closely related to the zonal-mean-flow response to wave driving in the stratosphere. The transformed Eulerian-mean analysis indicates that the wave driving is mostly due to convergence of synoptic-scale waves originating from the midlatitude troposphere and propagating into the subtropical UTLS in this model simulation. The modeled CPT also shows a large sensitivity to increased baroclinicity in the equilibrium temperature. Although planetary-scale waves are not considered in this simulation, the result confirms that wave-driven upwelling in the tropical UTLS is a crucial process for the formation and maintenance of the CPT. In addition, it also implies that synoptic-scale waves may play a nonnegligible role in this mechanism, particularly in the seasons when planetary-scale wave activity in the lower stratosphere is weak. © 2015 American Meteorological Society."
"56478591100;7004696243;","Regime diagrams of solutions in an idealized quasi-axisymmetric model for superrotation of planetary atmospheres",2015,"10.2151/jmsj.2015-017","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84929315062&doi=10.2151%2fjmsj.2015-017&partnerID=40&md5=f0ec0cedf4b0f91f24a12f078bd1fbfe","This paper presents regime diagrams illustrating the parametric dependence of dynamical balance in a superrotating atmosphere produced in a quasi-axisymmetric idealized system with strong horizontal diffusion studied previously by the present authors. In this system, the superrotation is maintained by the Gierasch mechanism, which possibly explains the four-day circulation in the atmosphere of Venus. Our previous paper developed a theoretical model of this system to estimate the superrotation strength and showed that the parametric dependence of the superrotation strength can be consolidated into three non-dimensional external parameters. The present study analyzes the theoretical model to determine boundaries of the regimes based on the dynamical balance and plots theoretical regime diagrams, which are important to understand the non-linear dynamical system and are useful to clearly describe the parametric dependence. Further, a parametric limit of the theoretical model is also estimated and included in the diagrams. The parametric limit shows both a lower limit for the horizontal diffusion and an upper limit of the superrotation strength in the Gierasch mechanism. The regime diagram demonstrates that the superrotation in the cyclostrophic balance is realized when the horizontal Ekman number is in a certain range whose width is mainly controlled by the vertical Ekman number. Numerical solutions covering a vast region in the parameter space are obtained by time-integrations of the primitive equations, and the dynamical regimes in the numerical solutions are compared with the theoretical regime diagrams. The theoretical regime diagrams agree well with the numerical results in most regions, confirming the validity of the theoretical model. Multiple equilibrium solutions are obtained when the horizontal Ekman number is lower than the theoretical limit. Moreover, they show that the Gierasch mechanism can maintain the superrotation even with the horizontal diffusion weaker than the predicted lower limit, but cannot generate superrotation from a motionless state. © 2015, Meteorological Society of Japan."
"55628570879;7004696243;","Theoretical estimation of the superrotation strength in an idealized quasi-axisymmetric model of planetary atmospheres",2013,"10.2151/jmsj.2013-203","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878205518&doi=10.2151%2fjmsj.2013-203&partnerID=40&md5=9c1042511e4fa535d7cad2a232375720","This paper presents a theoretical estimation of the strength of equatorial superrotation in planetary atmospheres by exploring a quasi-axisymmetric system that is zonally averaged primitive equations for a dry Boussinesqfluid on a rotating hemisphere with the effects of nonaxisymmetric eddies parameterized by eddy diffusion. The fluid is forced by Newtonian heating and cooling, and the horizontal eddy diffusion of momentum is assumed to be much stronger than the vertical one. In this system, the superrotation is maintained by the Gierasch mechanism, which possibly explains the superrotation of the Venus atmosphere by angular momentum transport due to the mean meridional circulation and horizontal diffusion. For the estimation, a quintic equation for a scalar measure of the superrotation strength is developed from the primitive equations. The quintic equation estimates the superrotation strength by its unique positive solution, which depends only on three nondimensional parameters: the external thermal Rossby number, the ratio of the radiative relaxation time to the timescale for the vertical diffusion, and the ratio of the planetary rotation period to the geometric mean of the timescales for the horizontal and vertical diffusion. The parameter dependence of the dominant dynamical balance is also investigated. The balance is a cyclostrophic, geostrophic, or horizontal diffusion balance, and in each balance, the equator-to-pole temperature difference is either nearly equal to that in the radiative-convective equilibrium state or signifficantly reduced by thermal advection. Steady-state or statistically steady-state solutions of the primitive equations are obtained by numerical timeintegrations for a wide parameter range covering many orders of magnitude. The numerical solutions show that the theoretical estimates have a relative error of less than 50%, which is very small compared with the superrotation strength varying five orders depending on the external parameters, and show that the estimation is valid. © 2013, Meteorological Society of Japan."
"55740245100;55747266100;","Development of a three-dimensional spectral linear baroclinic model and its application to the baroclinic instability associated with positive and negative arctic oscillation indices",2013,"10.2151/jmsj.2013-207","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84878184183&doi=10.2151%2fjmsj.2013-207&partnerID=40&md5=e510b30b450cea931fbebe629af505cb","In this study, a linear baroclinic model (LBM) is developed from athree-dimensiona l (3D) spectral primitive equation model. With this LBM, we investigate the linear stability problem for various zonally varying basic states on a sphere. For a zonal climate basic state, we confirm that the traditional Charney and dipole Charney modes appear as the most dominant unstable modes in the synoptic to planetary scales. For a zonally varying basic state, we find that these unstable modes are modified by the regionality of the local baroclinicity of the basic state. Given the zonally varying barotropic basic state, we find that the barotropically most unstable standing mode appears to be the Arctic Oscillation (AO) mode. In this study, the eigensolution of the LBM is regarded as a generalized extension at the 3D normal mode at the motionless atmosphere to those of an arbitrary climate basic state. As an application of the LBM, various zonally varying basic states associated with the positive and negative AO indices are substituted into the LBM to find the response of the baroclinic eddies. According to the result, the positive feedback dominates in the Atlantic sector for positive AO index because of the presence of enhanced double-jet structure. When the AO index is negative, the eddy momentum flux converges in the mid-latitudes to shift the subtropical jet poleward in the Atlantic and Pacific sectors because of the intensified baroclinic instability. The positive feedback operates in a different way in the Atlantic and Pacific sectors depending on their double or single westerly jets. It is concluded that the baroclinically unstable modes are modified by the positive/negative AO index, so that the induced local eddy momentum flux shows a positive feedback to the AO. © 2013, Meteorological Society of Japan."
"57200319057;7006705919;","Climate simulations with an isentropic finite-volume dynamical core",2012,"10.1175/2011JCLI4184.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859947788&doi=10.1175%2f2011JCLI4184.1&partnerID=40&md5=ea314bafaf1253fd027bdea5506a66cf","This paper discusses the impact of changing the vertical coordinate from a hybrid pressure to a hybridisentropic coordinate within the finite-volume (FV) dynamical core of the Community Atmosphere Model (CAM). Results from a 20-yr climate simulation using the new model coordinate configuration are compared to control simulations produced by the Eulerian spectral and FV dynamical cores of CAM, which both use a pressure-based (δ - P) coordinate. The same physical parameterization package is employed in all three dynamical cores. The isentropic modeling framework significantly alters the simulated climatology and has several desirable features. The revised model produces a better representation of heat transport processes in the atmosphere leading to much improved atmospheric temperatures. The authors show that the isentropic model is very effective in reducing the long-standing cold temperature bias in the upper troposphere and lower stratosphere, a deficiency shared among most climate models. The warmer upper troposphere and stratosphere seen in the isentropic model reduces the global coverage of high clouds, which is in better agreement with observations. The isentropic model also shows improvements in the simulated wintertime mean sea level pressure field in the Northern Hemisphere. © 2012 American Meteorological Society."
"56875897900;57202240753;","Comparison of different order Adams-Bashforth methods in an atmospheric general circulation model",2011,"10.1007/s13351-011-0606-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863282570&doi=10.1007%2fs13351-011-0606-6&partnerID=40&md5=927896707abe5d7c10f61cec6a12b68a","The Asselin-Robert time filter used in the leapfrog scheme does degrade the accuracy of calculations. As an attractive alternative to leapfrog time differencing, the second-order Adams-Bashforth method is not subject to time splitting instability and keeps excellent calculation accuracy. A second-order Adams- Bashforth model has been developed, which represents better stability, excellent convergence and improved simulation of prognostic variables. Based on these results, the higher-order Adams-Bashforth methods are developed on the basis of NCAR (National Center for Atmospheric Research) CAM 3.1 (Community Atmosphere Model 3.1) and the characteristics of dynamical cores are analyzed in this paper. By using Lorenz nonlinear convective equations, the filtered leapfrog scheme shows an excellent pattern for eliminating 2Δt wave solutions after 20 steps but represents less computational solution accuracy. The fourth-order Adams- Bashforth method is closely converged to the exact solution and provides a reference against which other methods may be compared. Thus, the Adams-Bashforth methods produce more accurate and convergent solution with differencing order increasing. The Held-Suarez idealized test is carried out to demonstrate that all methods have similar climate states to the results of many other global models for long-term integration. Besides, higher-order methods perform better in mass conservation and exhibit improvement in simulating tropospheric westerly jets, which is likely equivalent to the advantages of increasing horizontal resolutions. Based on the idealized baroclinic wave test, a better capability of the higher-order method in maintaining simulation stability is convinced. Furthermore, after the baroclinic wave is triggered through overlaying the steady-state initial conditions with the zonal perturbation, the higher-order method has a better ability in the simulation of baroclinic wave perturbation. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2011."
"7103321545;10144503600;36842329100;","Differences between the intense precipitation associated with subsynoptic-scale Baiu frontal depression simulated by an AGCM and described in observational studies",2008,"10.2151/jmsj.86.563","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049106860&doi=10.2151%2fjmsj.86.563&partnerID=40&md5=d1fd77da01471b80d03f83cdf4d82ff0","We compared features of the precipitation associated with subsynoptic-scale Baiu frontal depression simulated by an atmospheric general circulation model (AGCM; T106L56: a spectral primitive-equation model with 56 σ levels and triangular spectral truncation at zonal wavenumber 106) with the features had been described in observational studies. The 21-year model integration from 1979 to 1999 was constrained by observed sea-surface temperature and sea-ice distribution. As typical examples, this paper examines simulation cases for June 1991. Comparisons with past observational results showed that the AGCM properly simulated the Baiu front and the Baiu frontal precipitation in the averaged fields for a 15-day period in June 1991. However, the area of the largest 1-hour precipitation is simulated at about 500 km northeastward from the area of the largest averaged precipitation. We also found significant differences between the simulations and the observations when we examined the daily precipitation and the maximum 1-hour precipitation for each day simulated by the model. While precipitation associated with subsynoptic-scale Baiu frontal depressions was relatively well simulated, intense precipitation in the trailing portion of these depressions was significantly underestimated. The result of the present study indicates that the ability of the AGCM to reproduce such extreme precipitation events must be examined in detail by comparing simulated daily and hourly precipitation with observational studies as well as by statistical analyses. © 2008, Meteorological Society of Japan."
"35608102200;8204579300;","The use of digital filter initialization to diagnose the mesoscale circulation and vertical motion in the California coastal transition zone",2001,"10.1016/S0924-7963(01)00023-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034963501&doi=10.1016%2fS0924-7963%2801%2900023-9&partnerID=40&md5=4e7c955b0189e6e001dac539414e08cb","A dynamical method of initializing the primitive equations is tested and used to diagnose the three-dimensional circulation associated with jets and eddies as found in the California coastal transition zone (CTZ). The initialization method, referred to as digital filter initialization (DFI), was recently developed by [Monthly Weather Review 120 (1992) 1019] for use in an intermittent data assimilation system in the atmosphere. The ability of DFI to recover the mesoscale ageostrophic circulation associated with finite amplitude jets and eddies in the ocean is first demonstrated using control data produced by simulations with a primitive equation model. The DFI method is then applied to synoptic hydrographic data collected during several California CTZ surveys in the summer of 1988. The diagnostic results indicate the existence of jets, eddies, and filaments in the CTZ domain with maximum horizontal currents of the order of 0.6 m/s at the surface. Currents associated with such jets and filaments are coherent to a depth of over 500 m. The surface currents associated with a prominent cool filament are generally confluent, and weakly convergent on average, along the 270 km offshore extent of the filament. Meanders in the jet display convergence and downwelling upstream of pressure troughs and divergence and upwelling downstream of the troughs. Maximum vertical velocities at 100 m are of the order of 10 m/day. This result is consistent with independent estimates of subduction rates made from biological studies in this and similar coastal filaments in the CTZ program."
"56424145700;7402681796;","Impacts of shortwave radiation forcing on ENSO: A study with a coupled tropical ocean-atmosphere model",2000,"10.1007/s003820000072","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033819196&doi=10.1007%2fs003820000072&partnerID=40&md5=9ec7c9a2cb38b935cdbf3ee21d6b4e98","We describe a coupled tropical ocean-atmosphere model that represents a new class of models that fill the gap between anomaly coupled models and fully coupled general circulation models. Both the atmosphere and ocean are described by two and half layer primitive equation models, which emphasize the physical processes in the oceanic mixed layer and atmospheric boundary layer. Ocean and atmosphere are coupled through both momentum and heat flux exchanges without explicit flux correction. The coupled model, driven by solar radiation, reproduces a realistic annual cycle and El Nino-Southern Oscillation (ENSO). In the presence of annual mean shortwave radiation forcing, the model exhibits an intrinsic mode of ENSO. The oscillation period depends on the mean forcing that determines the coupled mean state. A perpetual April (October) mean forcing prolongs (shortens) the oscillation period through weakening (enhancing) the mean upwelling and mean vertical temperature gradients. The annual cycle of the solar forcing is shown to have fundamental impacts on the behavior of ENSO cycles through establishing a coupled annual cycle that interacts with the ENSO mode. Due to the annual cycle solar forcing, the single spectral peak of the intrinsic ENSO mode becomes a double peak with a quasi-biennial and a low-frequency (4-5 years) component; the evolution of ENSO becomes phase-locked to the annual cycle; and the amplitude and frequency of ENSO become variable on an interdecadal time scale due to interactions of the mean state and the two ENSO components. The western Pacific monsoon (the annual shortwave radiation forcing in the western Pacific) is primarily responsible for the generation of the two ENSO components. The annual march of the eastern Pacific ITCZ tends to lock ENSO phases to the annual cycle. The model's deficiencies, limitations, and future work are also discussed."
"7006236576;","Evolution of moist-baroclinic normal modes in the nonlinear regime",1999,"10.1175/1520-0469(1999)056<3161:EOMBNM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033372616&doi=10.1175%2f1520-0469%281999%29056%3c3161%3aEOMBNM%3e2.0.CO%3b2&partnerID=40&md5=a3a7fae06cac48981ea0c96e99ce5b68","A primitive equation model, in which latent heat release is represented by a small static stability for all ascending air, is used to examine the early stages of nonlinear evolution of moist baroclinic waves, before finite amplitude equilibration sets in. The results here obtained improve previous quasigeostrophic work with regard to the structure of the solutions and reveal the incorrectness of a quasigeostrophic result concerning meridional displacement, which does not occur in the primitive equation model. Approximate formulations of perturbation buoyancy are tested and generally found inappropriate, revealing a high sensitivity of the results to this term.A primitive equation model, in which latent heat release is represented by a small static stability for all ascending air, is used to examine the early stages of nonlinear evolution of moist baroclinic waves, before finite amplitude equilibration sets in. The results here obtained improve previous quasigeostrophic work with regard to the structure of the solutions and reveal the incorrectness of a quasigeostrophic result concerning meridional displacement, which does not occur in the primitive equation model. Approximate formulations of perturbation buoyancy are tested and generally found inappropriate, revealing a high sensitivity of the results to this term."
"57197065577;6602155874;","Evaluation of subtidal water level in NOAA's coastal ocean forecast system for the U.S. East Coast",1997,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031315360&partnerID=40&md5=80d5a7f5837f62ecac1521d7b5d3cc8b","A three-dimensional, baroclinic, primitive-equation ocean model is used to make 24-h forecasts of coastal water level along the East Coast of the United States. The model has 6 to 10 km horizontal resolution in the near-coastal ocean and is driven by forecast momentum, heat, and moisture fluxes derived from NOAA's 80 km resolution atmospheric Eta model. The model results are compared to observations of water level from NOAA's coastal water level gauges. For subtidal water level in the synoptic-band (2-10 days), from Portland, ME to St. Augustine, FL, the coherence-squared between model and data is above 0.75. On average, the subtidal root-mean-square difference between forecasts and data is ≈. 11 m and the forecasts have an approximate 66% success rate at predicting high and low water events greater than one standard deviation."
"7403601558;7103232081;55745955800;","Generalization of the effect of vertical shear of mean zonal flow on tropical CISK-wave excitation",1996,"10.1175/1520-0469(1996)053<2166:GOTEOV>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030407665&doi=10.1175%2f1520-0469%281996%29053%3c2166%3aGOTEOV%3e2.0.CO%3b2&partnerID=40&md5=8bc9e6542adcafec2523df13e9ee844b","This paper investigates the effects of vertical shear of the mean zonal flow on CISK waves in a spherical geometry. A linearized primitive equation model, including mean zonal flow, on a sphere is designed to generalize the previous results about the effects of the vertical shear of the mean zonal flow on the excitation of fast tropical waves with periods shorter than 20 days. In the case of linear CISK heating, the eastward propagating Kelvin waves are most unstable when the vertical shear of the mean zonal flow is easterly with height, and the westward propagating gravity waves (not mixed Rossby-gravity waves) are preferentially excited when the vertical shear of the mean zonal flow is westerly. The vertical structure of these unstable waves is in agreement with the previous results. In the troposphere, both the temperature and vertical velocity fields of the unstable waves tilt backward with height, and the tilt is smaller for the vertical velocity field than for the temperature field. In contrast, forward phase tilts are found above the troposphere, consistent with upward propagation of wave energy. In the case of positive-only (nonlinear) CISK heating, antisymmetric waves (with zonal wind antisymmetric about the equator) are suppressed, and an eastward propagating symmetric nondispersive wave packet with negligible meridional wind is excited. This unstable wave packet not only has zonally asymmetric structure but also has a change of zonal scale with height. Unlike in the linear case, the vertical shear of the mean zonal flow is unable to excite westward propagating gravity waves, but it does affect the instability of the wave packet in the same way as in the linear heating case. As was found for a single wave in the linear heating case, the unstable wave packet is shown to have a backward phase lilt with height in the troposphere. However, the effect of the vertical shear of the mean zonal flow on the wave packet works not by changing its phase tilt but by changing its zonal scale."
"7102366816;7102835431;7004332887;","Sensitivity study of an upper ocean model in a coastal bay",1996,"10.1016/0924-7963(95)00004-6","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029775272&doi=10.1016%2f0924-7963%2895%2900004-6&partnerID=40&md5=7eea6810c8e5b8ef246f921526b93429","An upper layer ocean model, with primitive equation dynamics and embedded with a mixed layer model at the top, is developed. Entrainment and detrainment in the mixed layer are determined from wind and buoyancy turbulent kinetic energy, as well as the effect of shear instability at the base of the mixed layer. The model parameterised the processes of convection and deep ocean diffusion, as well as mass entrainment at a subsurface layer due to strong upwelling. It was applied to the Baie des Chaleurs (Gulf of St. Lawrence, Canada). The model was forced by observed winds, atmospheric heat fluxes, river runoff and a remote coastal jet. The simulations in the main run reproduced well the observational fields in both time and space. Sensitivity runs are conducted to study the effects of external forcing, important physical processes and the internal physical parameterisation on the model results and to compare these with the main run. © 1996 Elsevier Science B.V. All rights reserved."
"7409802289;7004332887;8430069100;","The sensitivity of an eddy-resolving model to the surface thermal boundary conditions",1995,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029506673&partnerID=40&md5=bb64ad162705ca267bb2c2abcc01c5dc","We compare the effect of using four different formulations for the surface thermal boundary condition on a primitive equation eddy-resolving model. The first formulation is the conventional restoring boundary condition. The second formulation calculates the surface heat flux interactively by coupling the ocean model to a simple atmospheric model. The third formulation is a simplified energy balance model without atmospheric heat transport. The fourth formulation is a linearized energy balance model with atmospheric heat transport parameterized as a diffusion term. -from Authors"
"7005132811;7004691135;7401804956;6603829010;7004013012;7006385223;6701647898;7102403008;","Climatology and variability in the ECHO coupled GCM",1994,"10.1034/j.1600-0870.1994.t01-3-00003.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981583605&doi=10.1034%2fj.1600-0870.1994.t01-3-00003.x&partnerID=40&md5=83138f8f5e248c8410ec7bafc4e3d257","ECHO is a new global coupled ocean‐atmosphere general circulation model (GCM), consisting of the Hamburg version of the European Centre atmospheric GCM (ECHAM) and the Hamburg Primitive Equation ocean GCM (HOPE). We performed a 20‐year integration with ECHO. Climate drift is significant, but typical annual mean errors in sea surface temperature (SST) do not exceed 2° in the open oceans. Near the boundaries, however, SST errors are considerably larger. The coupled model simulates an irregular ENSO cycle in the tropical Pacific, with spatial patterns similar to those observed. The variability, however, is somewhat weaker relative to observations. ECHO also simulates significant interannual variability in mid‐latitudes. Consistent with observations, variability over the North Pacific can be partly attributed to remote forcing from the tropics. In contrast, the interannual variability over the North Atlantic appears to be generated locally. Copyright © 1994, Wiley Blackwell. All rights reserved"
"57198050391;25930906600;","Climate simulations using the GCRC 2-D zonally averaged statistical dynamical climate model",1994,"10.1016/0045-6535(94)90066-3","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028670032&doi=10.1016%2f0045-6535%2894%2990066-3&partnerID=40&md5=089365ffd3fe00bad7bc69da131e661d","The two-dimensional statistical dynamical climate model, recently developed at the Global Change Research Center (GCRC 2D climate model) is presented and discussed. The model solves the 2-D primitive equations in finite difference form (mass continuity, Newton's second law, and the first law of thermodynamics) for the prognostic variables zonal mean density, zonal mean zonal velocity, zonal mean meridional velocity, and zonal mean temperature on a grid that has 18 nodes in latitude and 9 vertical nodes (plus the surface). The equation of state, p = ρRT and an assumed hydrostatic atmosphere, δp = -ρgδz, are used to diagnostically calculate the zonal mean pressure and vertical velocity for each grid node, and the moisture balance equation is used to estimate the precipitation rate. The performance of the model at simulating the two-dimensional temperature, zonal winds, and mass stream function is discussed here. The strengths and weaknesses of the model are highlighted and plans for future model experiments and improvements are given. The parameterization of the transient eddy fluxes of heat and momentum developed by Stone and Yao (1987 and 1990) are used with small modifications. These modifications are shown to improve the performance of the model at simulating the observed climate system as well as increase the model's computational stability. © 1994."
"57196263802;7201654861;","A global model with overlapping mercator and stereographic grids",1986,"10.1007/BF02678651","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649156697&doi=10.1007%2fBF02678651&partnerID=40&md5=a97717978720de1af6dc56797ecc7b09","A global nine-layer primitive equation model is developed to investigate the dynamic and thermodynamic influences of plateaus and high mountains on the atmospheric circulation. Besides topography, the effects of solar radiation, longwave radiation, large-scale condensation, cumulus convection and surface fluxes of heat momentum are also included in the model. In order that the finite-difference approximations represent fairly accurately the circulation in both higher and lower latitudes, we use Mercator projection in lower latitudes and Stereographic projection in higher latitudes. The simulated sea level pressure, wind field, precipitation distribution and vertical circulation in summer and winter are given, respectively, and they are compared with the observations. © 1986 Advances in Atmospheric Sciences."
"7102201685;7003496841;","Scaling and computation of smooth atmospheric motions",1986,"10.1111/j.1600-0870.1986.tb00417.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977726524&doi=10.1111%2fj.1600-0870.1986.tb00417.x&partnerID=40&md5=d1dc123623ab26ffc902955628a6404a","We introduce a general scaling of the inviscid Eulerian equations which is satisfied by all members of the set of adiabatic smooth stratified atmospheric motions. Then we categorize the members into mutually exclusive subsets. By applying the bounded derivative principle to each of the subsets, we determine the specific scaling satisfied by that subset. One subset is midlatitude motion which is hydrostatic and has equal horizontal length scales. Traditionally, the primitive equations have been used to describe these motions. However it is well known that the use of the primitive equations for a limited area forecast of these motions leads to an ill‐posed initial‐boundary value problem. We introduce an alternate system which accurately describes this type of motion and can be used to form a well‐posed initial‐boundary value problem. We prove that the new system can also be used for any adiabatic or diabatic smooth stratified flow. Finally, we present supporting numerical results. 1986 Blackwell Munksgaard"
"36471711600;7201377982;7202935726;","The numerical experiments on dynamic forcing by the Tibetan Plateau for various zonal flows",1985,"10.1007/BF03179751","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956558911&doi=10.1007%2fBF03179751&partnerID=40&md5=31b0862caa0e8077ebc17bacb78746aa","In this paper, the dynamic disturbances to various basic zonal currents caused by the Tibetan Plateau are simulated by means of a three-level primitive equation model, in which σ is used as the vertical coordinate. Four types of currents have been used, i. e. the barotropic homogeneous current, barotropic jet stream, baroclinic current and the zonal mean current in summer. The results are helpful to understand the dynamic effects of the Tibetan Plateau on the general circulation over East Asia. © 1985 Advances in Atmospheric Sciences."
"7202891697;36472812100;55715215300;","The dynamic effect of the Tibetan Plateau on the formation of zonal type circulation over East Asia",1985,"10.1007/BF03179748","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956558568&doi=10.1007%2fBF03179748&partnerID=40&md5=64f8147c5381c0cb463dcc5d14d5d0c6","From a statistical study of the atmospheric circulation types over the Northern Hemisphere it is found that the zonal type circulation predominates in East Asia. From a three-layer primitive equation model in σ-coordinate, the orographic effect on a westerly current over the Northern Hemisphere is studied. A distinguished deepening trough is observed in the lee-side slope of the Rocky Mountains. But a pronounced trough is over the East Asia coast far from the Tibetan Plateau. In a case of 48 h numerical forecast, it is found that the effect of the Tibetan Plateau tends to build up a rather zonal type circulation, which is consistent with the observations. These may be partly explained by the topographic effect of the north slope of the Tibetan Plateau in a simple geostrophic theory. © 1985 Advances in Atmospheric Sciences."
"6604010263;7101630970;","Orographically induced Rossby wave instabilities.",1984,"10.1175/1520-0469(1984)041<0051:OIRWI>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021639728&doi=10.1175%2f1520-0469%281984%29041%3c0051%3aOIRWI%3e2.0.CO%3b2&partnerID=40&md5=9d0a22c2d78669c83d30e56e32fdaa40","An extension is made to a five-layer, sigma-coordinate, primitive equation model on the sphere, using more degrees of freedom. Taking as the basic state the Northern Hemisphere winter zonal mean flow, orographically unstable modes are found. In all but one case, the associated growth rates are much smaller than those corresponding to baroclinic instability, even for rather larger mountains. -from Authors"
"7004451085;","Numerical studies of transient planetary circulations in a wind-driven ocean",1972,"10.1007/BF00875275","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250475617&doi=10.1007%2fBF00875275&partnerID=40&md5=b5a8a60d09f0df83b2b76417316e4ea4","The time-dependent primitive equations for a shallow homogeneous ocean with a free surface are solved for a bounded basin on the sphere, driven by a steady zonal wind stress and subject to lateral viscous dissipation. These are the vertically integrated equations for a free-surface model, and are integrated to 60 days from an initial state of rest by an explicit centered-difference method with zero-slip lateral boundary conditions. In a series of comparative numerical solutions it is shown that at least a 2-deg resolution is needed to resolve the western boundary currents adequately and to avoid undue distortion of the transient (Rossby waves. The β-plane formulation is shown to be an adequate approximation for the mean circulation in the lower and middle latitudes, but noticeably intensifies the transports poleward of about 50 deg and both slows and distorts the transients in the central basin. The influence of the (southern) zonal boundary on the transport solutions is confined to the southernmost gyre, except in the region of the western boundary currents where its influence spreads to the northern edge of the basin by 30 days. The total boundary current transport is shown to be approximately proportional to the zonal width of the basin and independent of the basin's (uniform) depth, while the elevation of the free water surface is inversely proportional to the basin depth, in accordance with linear theory. The introduction of bottom friction has a marked damping effect on the transient Rossby waves, and also reduces the maximum boundary-current transport. The solutions throughout are approximately geostrophic and are only slightly nonlinear. The root-mean-square (rms) transport variability during the period 30 to 60 days is concentrated in the southwest portion of the basin through the reflection of the transient Rossby waves from the western shore and has a maximum corresponding to an rms current variability of about 3 cm sec-1. The transport variabilities are about 10 percent of the mean zonal transport and more than 100 percent of the mean meridional transport over a considerable region of the western basin (outside the western boundary current regime). Some 99 percent of the total kinetic energy is associated with the zonal mean and standing zonal waves, which are also responsible for the bulk of the meridional transport of zonal angular momentum. Although the transient Rossby waves systematically produce a momentum flux convergence at the latitude of the maximum eastward current, much in the manner of their atmospheric counterparts, this is only a relatively small contribution to the zonal oceanic momentum balance; the bulk of the mean zonal stress is here balanced by a nearly stationary net pressure torque exerted against the meridional boundaries by the wind-raised water. In an ocean without such boundaries the role of the transient circulations may be somewhat more important. © 1972 Birkhäuser Verlag."
"43361238200;56402758400;57217492108;56414357900;57061487100;23989037500;","THOR 2.0: Major Improvements to the Open-source General Circulation Model",2020,"10.3847/1538-4365/ab930e","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087298421&doi=10.3847%2f1538-4365%2fab930e&partnerID=40&md5=befe8b175f645c651a0a44189879fc5d","THOR is the first open-source general circulation model (GCM) developed from scratch to study the atmospheres and climates of exoplanets, free from Earth- or solar-system-centric tunings. It solves the general nonhydrostatic Euler equations (instead of the primitive equations) on a sphere using the icosahedral grid. In the current study, we report major upgrades to THOR, building on the work of Mendonça et al. First, while the horizontally explicit and vertically implicit integration scheme is the same as that described in Mendonça et al., we provide a clearer description of the scheme and improve its implementation in the code. The differences in implementation between the hydrostatic shallow, quasi-hydrostatic deep, and nonhydrostatic deep treatments are fully detailed. Second, standard physics modules are added: two-stream, double-gray radiative transfer and dry convective adjustment. Third, THOR is tested on additional benchmarks: tidally locked Earth, deep hot Jupiter, acoustic wave, and gravity wave. Fourth, we report that differences between the hydrostatic and nonhydrostatic simulations are negligible in the Earth case but pronounced in the hot Jupiter case. Finally, the effects of the so-called ""sponge layer,"" a form of drag implemented in most GCMs to provide numerical stability, are examined. Overall, these upgrades have improved the flexibility, user-friendliness, and stability of THOR. © 2020. The Author(s). Published by the American Astronomical Society."
"55747696500;36741042500;7103126833;6505623124;7102369927;16246800500;","High-resolution ensemble HFV3 forecasts of Hurricane Michael (2018): Rapid intensification in shear",2020,"10.1175/MWR-D-19-0275.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085140776&doi=10.1175%2fMWR-D-19-0275.1&partnerID=40&md5=bda75fe3263854a6fd95c3c975bdf393","The FV3GFS is the current operational Global Forecast System (GFS) at the National Centers for Environmental Prediction (NCEP), which combines a finite-volume cubed sphere dynamical core (FV3) and GFS physics. In this study, FV3GFS is used to gain understanding of rapid intensification (RI) of tropical cyclones (TCs) in shear. The analysis demonstrates the importance of TC structure in a complex system like Hurricane Michael, which intensified to a category 5 hurricane over the Gulf of Mexico despite over 20 kt (10 m s21) of vertical wind shear. Michael's RI is examined using a global-nest FV3GFS ensemble with the nest at 3-km resolution. The ensemble shows a range of peak intensities from 77 to 159 kt (40-82 m s21). Precipitation symmetry, vortex tilt, moisture, and other aspects of Michael's evolution are compared through composites of stronger and weaker members. The 850-200-hPa vertical shear is 22 kt (11 m s21) in the mean of both strong and weak members during the early stage. Tilt and moisture are two distinguishing factors between strong and weak members. The relationship between vortex tilt and humidification is complex, and other studies have shown both are important for sheared intensification. Here, it is shown that tilt reduction leads to upshear humidification and is thus a driving factor for intensification. A stronger initial vortex and early evolution of the vortex also appear to be the key to members that are able to resist the sheared environment. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"56403217500;21734716100;46461225600;55325748100;57213387166;","Skill and uncertainty in surface wind fields from general circulation models: Intercomparison of bias between AGCM, AOGCM and ESM global simulations",2020,"10.1002/joc.6357","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075448074&doi=10.1002%2fjoc.6357&partnerID=40&md5=99fd30eb57314362ab42341972fa9fb3","Understanding the reliability of global climate models (GCMs) to reproduce the historical surface wind fields is integral part of building robust projections of surface wind-climate, and other wind-dependent geophysical climatic variables. Understanding the skill of atmosphere-only models (AGCM), coupled atmosphere–ocean models (AOGCM) and fully coupled earth system models (ESM) is likewise paramount to assess any systematic model improvements. In this paper, we systematically assess whether surface wind fields obtained from 28 CMIP5 GCMs can represent large-scale spatial patterns and temporal variability of historical surface winds. We show that inter-model uncertainty is typically 2–4 times larger than the uncertainty associated with GCM internal variability, although the latter can be significant within specific regions. We also find that CMIP5 models are typically capable of reliably reproducing large-scale spatial patterns of historical near-surface winds, but considerable uncertainty lies within the CMIP5 ensemble with strong latitudinal dependence. CMIP5 models show limitations in their ability to reliably represent inter-annual and inter-seasonal variability particularly within tropical-cyclone-affected regions. In further analysis, we quantify and intercompare historical wind bias from different types of models with different dynamical cores, based on multiple CMIP5 diagnostic experiments. We find that bias in surface wind fields are largely intrinsic to the atmospheric components of the models, and that the inclusion of carbon-cycle dynamics has insignificant effect on simulated surface winds (at decadal time-scales). Inconsistencies between AGCM and AOGCM simulations are largely driven by errors in sea surface temperatures (SST); though such differences are not statistically significant relative to the inter-model uncertainty within the CMIP5 ensemble. These results show that the dominant source of bias in simulated wind fields lies in the underlying physics of the atmospheric component of the models. © 2019 Royal Meteorological Society"
"56585403700;7103106329;6701469233;","A very high-resolution assessment and modelling of urban air quality",2020,"10.5194/acp-20-625-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078402771&doi=10.5194%2facp-20-625-2020&partnerID=40&md5=65e5c86a58729a95ee0255fb0557b6f7","Urban air quality is one of the most prominent environmental concerns for modern city residents and authorities. Accurate monitoring of air quality is difficult due to intrinsic urban landscape heterogeneity and superposition of multiple polluting sources. Existing approaches often do not provide the necessary spatial details and peak concentrations of pollutants, especially at larger distances from monitoring stations. A more advanced integrated approach is needed. This study presents a very high-resolution air quality assessment with the Parallelized Large-Eddy Simulation Model (PALM), capitalising on local measurements. This fully three-dimensional primitive-equation hydrodynamical model resolves both structural details of the complex urban surface and turbulent eddies larger than 10 m in size. We ran a set of 27 meteorological weather scenarios in order to assess the dispersion of pollutants in Bergen, a middle-sized Norwegian city embedded in a coastal valley. This set of scenarios represents typically observed weather conditions with high air pollution from nitrogen dioxide (NO2) and particulate matter (PM2:5). The modelling methodology helped to identify pathways and patterns of air pollution caused by the three main local air pollution sources in the city. These are road vehicle traffic, domestic house heating with woodburning fireplaces and ships docked in the harbour area next to the city centre. The study produced vulnerability maps, highlighting the most impacted districts for each weather and emission scenario. Overall, the largest contribution to air pollution over inhabited areas in Bergen was caused by road traffic emissions for NO2 and wood-burning fireplaces for PM2:5 pollution. The effect of emission from ships in the port was mostly restricted to the areas close to the harbour and moderate in comparison. However, the results have contributed to implementation of measures to reduce emissions from ships in Bergen harbour, including provision of shore power. © 2020 Author(s)."
"57211499736;14018910800;8957645200;8361740900;","Combined use of volume radar observations and high-resolution numerical weather predictions to estimate precipitation at the ground: Methodology and proof of concept",2019,"10.5194/amt-12-5669-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068832182&doi=10.5194%2famt-12-5669-2019&partnerID=40&md5=39b0cfbd799521e7cfc7ce6b76479f5d","The extrapolation of the precipitation to the ground from radar reflectivities measured at the beam altitude is one of the most delicate phases of radar data processing for producing quantitative precipitation estimations (QPEs) and remains a major scientific issue. In many operational meteorological services such as Météo-France, a vertical profile of reflectivity (VPR) correction is uniformly applied over a large part or the entire radar domain. This method is computationally efficient, and the overall bias induced by the bright band is most of the time well corrected. However, this way of proceeding is questionable in situations with high spatial and vertical variability of precipitation (during the passage of a cold front or in a complex terrain, for example). This study initiates from two statements: first, radars provide information on precipitation with a high spatio-temporal resolution but still require VPR corrections to extrapolate rain rates at the ground level. Second, the horizontal resolution of some numerical weather prediction (NWP) models is now comparable with the radar one, and their dynamical core and microphysics schemes allow the production of realistic simulations of VPRs. The present paper proposes a new approach to assess surface rainfall from radar reflectivity aloft by exploiting simulated VPRs and rainfall forecasts from the high-resolution NWP model AROME-NWC. To our knowledge, this is the first time that simulated precipitation profiles from an NWP model are used to derive radar QPEs. The implementation of the new method on two stratiform situations provided significant improvements on the hourly and 6&thinsp;h accumulations compared to the operational QPEs, showing the relevance of this new approach. © 2019 Institute of Electrical and Electronics Engineers Inc.. All rights reserved."
"55796391600;57196090861;56193847400;57191637376;55709136700;55200900200;","A modified nonhydrostatic moist global spectral dynamical core using a dry-mass vertical coordinate",2019,"10.1002/qj.3574","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068403345&doi=10.1002%2fqj.3574&partnerID=40&md5=14882278697cf1316aae14dee2594e0b","Most global models employ a vertical coordinate based on the moist hydrostatic pressure, and therefore do not conserve dry air mass. Such an issue should be taken seriously into account, especially in developing global high-resolution atmospheric models to address nonhydrostatic motions explicitly. In this article, we present a modified nonhydrostatic moist global spectral dynamical core using a dry-mass vertical coordinate, which conserves the mass of dry air naturally. In addition to the vertical coordinate, the modified dynamical core differs from the original Aladin-NH like dynamical kernel in the state variables employed. Specifically, a new temperature variable is introduced to formulate the governing equations and the mass continuity equation is expressed in terms of the dry air density. To assess its performance, an idealized splitting supercell test is conducted. Simulation results from both the modified and original dynamical cores are presented and compared. The results indicate that only the modified dynamic core is able to simulate the splitting supercell with good accuracy comparable to reference solutions from the Model for Prediction Across Scales (MPAS). © 2019 Royal Meteorological Society"
"7201554561;23485958100;6602469258;","Transient contributions to the forcing of the atmospheric annual cycle: A diagnostic study with the DREAM model",2019,"10.1007/s00382-018-4539-y","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056706103&doi=10.1007%2fs00382-018-4539-y&partnerID=40&md5=173f5af270f70b357363b0117ac87a74","The forcing of the global circulation is examined using a primitive equation model and a 38-year reanalysis dataset. One-timestep integrations are initialised with selected sets of initial conditions, and the forcing budget for the mean annual cycle is deduced. This budget consists of sources and sinks of momentum, temperature and humidity which are balanced by dynamical terms. The associated timescale interactions are examined in detail. The time-mean forcing is balanced by time-mean fluxes, annual cycle interactions and transient fluxes. The annual cycle of the forcing is balanced by the interaction of annual cycle anomalies with the time-mean flow and with themselves (this latter cycle-cycle interaction term is found to be important for the moisture supply over West Africa). Transient interactions on other timescales also contribute to the forcing of the annual cycle, but the interaction term between the annual cycle and other timescales is small, as is the storage term associated with seasonal tendencies. This objectively derived empirical forcing is then used to drive the dynamical model. The resulting simple GCM is called DREAM (Dynamical Research Empirical Atmospheric Model). This is the first time this approach has been used with an annual cycle. The systematic errors of DREAM compared to the reanalysis chiefly concern the momentum balance in the southern hemisphere jet. Perpetual season simulations are similar to individual seasons from the annual cycle run, consistent with the small seasonal tendency term in the forcing. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature."
"55500860200;","The long- And short-lived North Atlantic oscillation events in a simplified atmospheric model",2019,"10.1175/JAS-D-18-0288.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075631041&doi=10.1175%2fJAS-D-18-0288.1&partnerID=40&md5=a87af68d92bc2851040800d8a3b34941","This study investigates the North Atlantic Oscillation (NAO) events with relatively long and short lifetimes based on an 8000-day perpetual-boreal-winter [December–February (DJF)] run result of the idealized Geophysical Fluid Dynamics Laboratory (GFDL) dynamical core atmospheric model. We identify the so-called long- and short-lived positive and negative NAO events from the 8000-day model output. The composite 300-hPa geopotential height anomalies show that the spatial patterns of the composite long-lived NAO events closely resemble the Northern Hemisphere annular mode (NAM) because the NAO dipole is accompanied with a statistically significant North Pacific meridional dipole (NPMD) at similar latitudes as that of the NAO dipole. The composite short-lived NAO events exhibit the locally confined canonical NAO. Twelve sets of modified initial-value experiments indicate that an absence (a presence) of the NPMD-type perturbations at the early stage of the long (short)-lived NAO events will decrease (increase) their intensities and naturally shorten (lengthen) their lifetimes. Thus, the preceding NPMD is an early factor that is conducive to the emergence of the long-lived NAO events in the model. We argue that through directly modulating the synoptic eddy forcing over the North Atlantic region, the preceding NPMD can gradually arouse the NAO-like circulation anomalies on the following days. That is the reason why the preceding NPMD can modulate the intensities and lifetimes of the NAO events. © 2019 American Meteorological Society"
"57210265433;55600504900;8152726300;","Noninstantaneous wave-CISK for the interaction between convective heating and low-level moisture convergence in the tropics",2019,"10.1175/JAS-D-19-0003.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85070098704&doi=10.1175%2fJAS-D-19-0003.1&partnerID=40&md5=e90db18784c36e010b1a7b174ee07cd8","The interaction between tropical convective heating and thermally forced circulation is investigated using a global dry primitive-equation model with the parameterization of wave-conditional instability of the second kind (CISK). It is demonstrated that deep convective heating can hardly sustain itself through the moisture convergence at low levels regardless of the fraction of immediate consumption of converged moisture. In contrast, when the fraction is large, shallow convective heating and its forced circulation exhibit preferred growth of small scales. As the ""CISK catastrophe"" mainly comes from the instantaneous characters of moisture-convection feedback in the conventional wave-CISK, a noninstantaneous wave-CISK is proposed, which highlights the accumulation-consumption (AC) time scale for the convective heating accumulation and/or the converged moisture consumption. In the new wave-CISK, once moisture is converged, the release of latent heat takes place gradually within an AC time scale. In this sense, convective heating is not only related to the instantaneous moisture convergence at the current time, but also to that which occurred in the past period of the AC time scale. The noninstantaneous wave-CISK could guarantee the occurrence of convective heating and/or moisture convergence at larger scales, and then favor the growth of long waves, and thus solve the problem of CISK catastrophe. With the new wave-CISK and AC time scale of 2 days, the simulated convective heating-driven system bears a large similarity to that of the observed convectively coupled Kelvin wave. © 2019 American Meteorological Society."
"36644095800;13406399300;36992744000;57002623400;7102645933;","Exploring a Lower-Resolution Physics Grid in CAM-SE-CSLAM",2019,"10.1029/2019MS001684","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068505909&doi=10.1029%2f2019MS001684&partnerID=40&md5=f587faa431cd1f1a33ecd22b48162c02","This paper describes the implementation of a coarser-resolution physics grid into the Community Atmosphere Model (CAM), containing (Formula presented.) fewer grid columns than the dynamics grid. The dry dynamics is represented by the spectral element dynamical core, and tracer transport is computed using the Conservative Semi-Lagrangian Finite Volume Method (CAM-SE-CSLAM). Algorithms are presented that map fields between the dynamics and physics grids while maintaining numerical properties ideal for atmospheric simulations such as mass conservation and mixing ratio shape and linear-correlation preservation. The results of experiments using the lower-resolution physics grid are compared to the conventional method in which the physics and dynamical grids coincide. The lower-resolution physics grid provides a volume mean state to the physics computed from an equal sampling of the different types of nodal solutions arising in the spectral-element method and effectively mitigates grid imprinting in regions with steep topography. The impact of the coarser-resolution physics grid on the resolved scales of motion is analyzed in an aquaplanet configuration, across a range of dynamical core grid resolutions. The results suggest that the effective resolution of the model is not degraded through the use of a coarser-resolution physics grid. Since the physics makes up about half the computational cost of the conventional CAM-SE-CSLAM configuration, the coarser physics grid may allow for significant cost savings with little to no downside. ©2019. The Authors."
"57205116284;35434835300;55479166700;57205119614;35215221100;36171552900;","Comparison of simulated tropical cyclone intensity and structures using the WRF with hydrostatic and nonhydrostatic dynamical cores",2018,"10.3390/atmos9120483","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85058642431&doi=10.3390%2fatmos9120483&partnerID=40&md5=1c02bd2355cb413ac8f3805eca4bd476","This study explored the influence of choosing a nonhydrostatic dynamical core or a hydrostatic dynamical core in the weather research and forecasting (WRF) model on the intensity and structure of simulated tropical cyclones (TCs). A comparison of cloud-resolving simulations using each core revealed significant differences in the TC simulations. In comparison with the nonhydrostatic simulation, the hydrostatic simulation produced a stronger and larger TC, associated with stronger convective activity. A budget analysis of the vertical momentum equation was conducted to investigate the underlying mechanisms. Although the hydrostatic dynamical core was used, the vertical motion was not in strict hydrostatic balance because of the existence of the vertical perturbation pressure gradient force, local buoyancy force, water loading, and sum of the Coriolis and diffusion effects. The contribution of the enhanced vertical perturbation pressure gradient force was found to be more important for stronger upward acceleration in the eyewall in the hydrostatic simulation than in the nonhydrostatic simulation. This is because it leads to intensified convection in the eyewall that releases more latent heat, which induces a larger low-level radial pressure gradient and inflow motion, and eventually leads to a stronger storm. © 2018 by the authors."
"55500860200;","Understanding anomalous synoptic eddy vorticity forcing in Pacific-North American teleconnection pattern events",2018,"10.1175/JAS-D-18-0071.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059255142&doi=10.1175%2fJAS-D-18-0071.1&partnerID=40&md5=b43d2b50e0c58cb02dde9c4f12ba258b","Utilizing a decomposition of anomalous eddy vorticity forcing (EVF) proposed by Song in 2016 and a modified Geophysical Fluid Dynamics Laboratory (GFDL) dynamical core atmospheric model, this study provides a different understanding of physical mechanisms that are responsible for the formation of the anomalous synoptic EVF (SEVF) associated with Pacific-North American teleconnection pattern (PNA) events. A series of short-term control experiments (CEs) and initial-value modified experiments (IVMEs) is conducted. In each case of CEs, there are no obvious PNA-like circulation anomalies. IVMEs are exactly the same as CEs except that appropriate small perturbations are introduced into the initial-value fields of CEs. The modified initial-value fields led to a gradual development of the PNA-like flow anomalies in IVMEs. Based on these numerical results, deformations of the synoptic eddy ψ' D due to the emergence of the PNA pattern can be easily acquired by subtracting the synoptic eddy in CEs ψ' C from the synoptic eddy in IVMEs ψ' 1 . The anomalous SEVF associated with the PNA events in the model can be decomposed into ensembles of two linear ψ' C and ψ' D interaction terms (EVF1 and EVF2) and a nonlinear ψ' D self-interaction term (EVF3). It is demonstrated that the physical essence of the anomalous SEVF associated with the PNA events is a competition result between EVF1 plus EVF2 and EVF3. Results also indicate that the different signs of SEVF associated with the positive and negative PNA events are not necessarily related to the different tilts of the synoptic eddy. © 2018 American Meteorological Society."
"56541813000;7401594160;","Long-Term Integration of a Global Non-Hydrostatic Atmospheric Model on an Aqua Planet",2018,"10.1007/s13351-018-8016-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052706577&doi=10.1007%2fs13351-018-8016-7&partnerID=40&md5=e193a0bf05fbb8266304203abbb1ed05","A global non-hydrostatic atmospheric model, i.e., GRAPES_YY (Global/Regional Assimilation and Prediction System on the Yin–Yang grid), with a semi-implicit semi-Lagrangian (SISL) dynamical core developed on the Yin–Yang grid was coupled with the physical parameterization package of the operational version of GRAPES. A 3.5-yr integration was carried out on an aqua planet to assess the numerical performance of this non-hydrostatic model relative to other models. Specific aspects of precipitation and general circulation under two different sea surface temperature (SST) conditions (CONTROL and FLAT) were analyzed. The CONTROL SST peaked at the equator. The FLAT SST had its maximum gradient at about 20° latitude, giving a broad equatorial SST maximum in the tropics and flat profile approaching the equator. The tropical precipitation showed different propagation features in the CONTROL and FLAT simulations. The CONTROL showed tropical precipitation bands moving eastward with some envelopes of westward convective-scale disturbance. Less organized westward-propagating rainfall cells and bands were seen in the FLAT and the propagation of the tropical wave varied with the SST gradient. The Inter Tropical Convergence Zone (ITCZ), Hadley cell, and westerly jet core were weaker and more poleward as the SST profile flattened from the CONTROL to FLAT. The climatological structures simulated by GRAPES_YY, such as the distribution of precipitation and the large-scale circulation, fell within the bounds from other models. The stronger ITCZ precipitation, accompanied with stronger Hadley cells and convective heating in the CONTROL simulation, may be summed up as a result of stronger parameterized convection and the non-hydrostatic effects in GRAPES_YY. In addition, mechanism of the zonal mean circulation maintaining is analyzed for the different SST patterns referring the transient eddy flux. © 2018, The Chinese Meteorological Society and Springer-Verlag GmbH Germany, part of Springer Nature."
"56893786200;7005808242;6507253177;55851081200;","Lower-tropospheric eddy momentum fluxes in idealized models and reanalysis data",2017,"10.1175/JAS-D-17-0099.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85034785857&doi=10.1175%2fJAS-D-17-0099.1&partnerID=40&md5=db73da7f3b470d0fa50a8594f53b8850","In Earth's atmosphere eddy momentum fluxes (EMFs) are largest in the upper troposphere, but EMFs in the lower troposphere, although modest in amplitude, have an intriguing structure. To document this structure, the EMFs in the lower tropospheres of a two-layer quasigeostrophic model, a primitive equation model, and the Southern Hemisphere of a reanalysis dataset are investigated. The lower-tropospheric EMFs are very similar in the cores of the jets in both models and the reanalysis data, with EMF divergence (opposing the upper-tropospheric convergence) due to relatively long waves with slow eastward phase speeds and EMF divergence (as in the upper troposphere) due to shorter waves with faster eastward phase speeds. As the two-layer model is able to capture the EMF divergence by long waves, a qualitative picture of the underlying dynamics is proposed that relies on the negative potential vorticity gradient in the lower layer of the model. Eddies excited by baroclinic instability mix efficiently through a wide region in the lower layer, centered on the latitude of maximum westerlies and encompassing the lower-layer critical latitudes. Near these critical latitudes, the mixing is enhanced, resulting in increased EMF convergence, with compensating EMF divergence in the center of the jet. The EMF convergence at faster phase speeds is due to deep eddies that propagate on the upper-tropospheric potential vorticity gradient. © 2017 American Meteorological Society."
"57192200896;7005087624;","A decision tree algorithm for investigation of model biases related to dynamical cores and physical parameterizations",2016,"10.1002/2016MS000657","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85000714749&doi=10.1002%2f2016MS000657&partnerID=40&md5=43d418853e9696f5e63379d835db540a","An object-based evaluation method using a pattern recognition algorithm (i.e., classification trees) is applied to the simulated orographic precipitation for idealized experimental setups using the National Center of Atmospheric Research (NCAR) Community Atmosphere Model (CAM) with the finite volume (FV) and the Eulerian spectral transform dynamical cores with varying resolutions. Daily simulations were analyzed and three different types of precipitation features were identified by the classification tree algorithm. The statistical characteristics of these features (i.e., maximum value, mean value, and variance) were calculated to quantify the difference between the dynamical cores and changing resolutions. Even with the simple and smooth topography in the idealized setups, complexity in the precipitation fields simulated by the models develops quickly. The classification tree algorithm using objective thresholding successfully detected different types of precipitation features even as the complexity of the precipitation field increased. The results show that the complexity and the bias introduced in small-scale phenomena due to the spectral transform method of CAM Eulerian spectral dynamical core is prominent, and is an important reason for its dissimilarity from the FV dynamical core. The resolvable scales, both in horizontal and vertical dimensions, have significant effect on the simulation of precipitation. The results of this study also suggest that an efficient and informative study about the biases produced by GCMs should involve daily (or even hourly) output (rather than monthly mean) analysis over local scales. © 2016. The Authors."
"56256258400;26430995400;7003991093;","Equilibration of a baroclinic planetary atmosphere toward the limit of vanishing bottom friction",2016,"10.1175/JAS-D-15-0329.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982262176&doi=10.1175%2fJAS-D-15-0329.1&partnerID=40&md5=720e5568bd992ca6d5cd05255923fedb","This paper discusses whether and how a baroclinic atmosphere can equilibrate with very small bottom friction in a dry primitive equation general circulation model. The model is forced by a Newtonian relaxation of temperature to a prescribed temperature profile, and it is damped by a linear friction near the lower boundary. When friction is decreased by four orders of magnitude, kinetic energy dissipation by friction gradually becomes negligible, while ""energy recycling"" becomes dominant. In this limit kinetic energy is converted back into potential energy at the largest scales, thus closing the energy cycle without significant frictional dissipation. The momentum fluxes are of opposite sign in the upper and lower atmosphere: In the upper atmosphere, eddies converge momentum into the westerly jets; however, in the lower atmosphere, the eddies diverge momentum out of the westerly jets. The secondary circulation driven by the meridional eddy momentum fluxes thus acts to increase the baroclinicity of the westerly jet. This regime may be relevant for the Jovian atmosphere, where the frictional time scale may be much larger than the radiative damping time scale. © 2016 American Meteorological Society."
"16311654700;57203831571;","Adjoint sensitivity study on idealized explosive cyclogenesis",2016,"10.1007/s13351-016-5261-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84983670608&doi=10.1007%2fs13351-016-5261-5&partnerID=40&md5=f241a75a4137f3ea52730bed5da9d9a6","The adjoint sensitivity related to explosive cyclogenesis in a conditionally unstable atmosphere is investigated in this study. The PSU/NCAR limited-area, nonhydrostatic primitive equation numerical model MM5 and its adjoint system are employed for numerical simulation and adjoint computation, respectively. To ensure the explosive development of a baroclinic wave, the forecast model is initialized with an idealized condition including an idealized two-dimensional baroclinic jet with a balanced three-dimensional moderate-amplitude disturbance, derived from a potential vorticity inversion technique. Firstly, the validity period of the tangent linear model for this idealized baroclinic wave case is discussed, considering different initial moisture distributions and a dry condition. Secondly, the 48-h forecast surface pressure center and the vertical component of the relative vorticity of the cyclone are selected as the response functions for adjoint computation in a dry and moist environment, respectively. The preliminary results show that the validity of the tangent linear assumption for this idealized baroclinic wave case can extend to 48 h with intense moist convection, and the validity period can last even longer in the dry adjoint integration. Adjoint sensitivity analysis indicates that the rapid development of the idealized baroclinic wave is sensitive to the initial wind and temperature perturbations around the steering level in the upstream. Moreover, the moist adjoint sensitivity can capture a secondary high sensitivity center in the upper troposphere, which cannot be depicted in the dry adjoint run. © 2016, The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg."
"11939480800;7402669723;35330117400;6701357023;6701346187;55740245100;35572026100;","Normal modes of atmospheric variability in observations, numerical weather prediction, and climate models",2016,"10.1175/BAMS-D-15-00325.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978077091&doi=10.1175%2fBAMS-D-15-00325.1&partnerID=40&md5=a5d3c577bc5f77f4b44dcb418cb362ba","The workshop has seen extensive presentations on the normal-mode decomposition of data, wave analysis, as well as associated theoretical and observational studies. In particular, a significant contribution of the IG modes in atmospheric variability is established in the NWP models, in reanalysis datasets, and in climate simulations. As the tropics are a problematic area in many climate models, validation of simulated atmospheric variability in terms of NMFs is likely to provide useful information about model deficiencies. However, the role of IG modes in atmospheric circulations is still to be clearly identified: does it demonstrate an importance of linear IG waves in many atmospheric scales or that the IG modes are required in order to maintain a nonlinear balance? The NMFs may be seen as complementary to other orthogonal representations of modes of the atmospheric variability such as empirical orthogonal functions (EOFs). However, the NMF decomposition extracts physical wave modes that constitute solutions to the global linear primitive equation system. This makes the use of NMFs advantageous for diagnostic purposes, for isolating NWP issues, and the potential for improved prediction skill (e.g., the MJO). The use of the NMF decomposition is straightforward once we have the normal-mode solutions in hand. A part of the goal of the aforementioned MODES software was to overcome this last obstacle so that the normal-mode approach can be more extensively and widely exploited in the atmospheric and climate communities. We see potentials for more objective validations of the climate models under the normal-mode approach. More information about the meeting can be found on the workshop web page, where a majority of the presented talks have been published (https://www2.cgd.ucar.edu/sections/amp/events/20150826/presentations-posters). ©2016 American Meteorological Society."
"55914539400;7006460542;7202208382;7006173068;","Advances towards the development of a cloud-resolving model in South Africa",2014,"10.1590/sajs.2014/20130133","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988603091&doi=10.1590%2fsajs.2014%2f20130133&partnerID=40&md5=7eb9262194aacc3e6bea4c93bd6878ce","Recent advances in supercomputing have made feasible the numerical integration of high-resolution cloud-resolving models (CRMs). CRMs are being used increasingly for high-resolution operational numerical weather prediction and for research purposes. We report on the development of a new CRM in South Africa. Two bulk microphysics parameterisation schemes were introduced to a dynamical core of a two-dimensional Non-hydrostatic σ-coordinate Model (NSM) developed in South Africa. The resulting CRM was used to simulate two 12-day periods and an 8-day period observed during the Tropical Oceans Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. The response of the NSM to the large-scale forcing which occurred over the three periods, and which included both suppressed and active convection, was examined. The NSM is shown to be able to capture the differences in the three experiments and responds correctly to the large-scale forcing (i.e. it is able to distinguish between suppressed and active regimes). However, the model simulations are cooler and drier than the observations. We demonstrate progress made in the development of a CRM in South Africa, which can be used to study the attributes of convective rainfall over the region. © 2014. The Authors."
"36889113900;6507994779;","The sensitivity of characteristics of large scale baroclinic unstable waves in southern hemisphere to the underlying climate",2013,"10.1155/2013/981271","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84893656225&doi=10.1155%2f2013%2f981271&partnerID=40&md5=cd947162d51f4b903793824e1dc98cfd","The sensitivity of the main characteristics of baroclinically unstable waves with respect to fundamental parameters of the atmosphere (the static stability parameter σ 0 and vertical shear of a zonal wind Λ) is theoretically explored. Two types of waves are considered: synoptic scale waves and planetary scale (ultralong) waves based on an Eady-type model and model with vertically averaged primitive equations. Sensitivity functions are obtained that estimate the impact of variations in σ 0 and Λ on the growth rate and other characteristics of unstable waves and demonstrate that waves belonging to the short-wave part of the spectrum of unstable waves are more sensitive to changes in the static stability parameter than waves belonging to the long-wave part of the spectrum. The obtained theoretical results show that the increase of the static stability and decrease of the meridional temperature gradient in midlatitude baroclinic zones in some areas of the southern hemisphere lead to a slowing of the growth rate of baroclinic unstable waves and an increasing wavelength of baroclinic unstable wave maximum growth rate, that is, a spectrum shift of unstable waves towards longer wavelengths. These might affect the favorable conditions for the development of baroclinic instability and, therefore, the intensity of cyclone generation activity. © 2013 Sergei Soldatenko and Chris Tingwell."
"7005131869;","The diabatic pressure difference: A new diagnostic for the analysis of valley winds",2012,"10.1175/MWR-D-11-00128.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857097163&doi=10.1175%2fMWR-D-11-00128.1&partnerID=40&md5=9313a362ff7c09a324c841560c3cc58f","The purpose of this article is to introduce a new diagnostic measure of the time-integrated diabatic (thermal) forcing of a valley-plain system. This measure can be used to synchronize the evolution of thermally induced valley winds with respect to their forcing. Differences among numerical models or model configurations originating from diabatic forcing versus those originating from the model dynamics (e.g., turbulence scheme, dynamical core, etc.) can then be distinguished. © 2012 American Meteorological Society."
"6701807580;37019381400;6701357023;","CAM3 bias over the Arctic region during northern winter studied with a linear stationary model",2011,"10.1007/s00382-011-1033-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-79960981811&doi=10.1007%2fs00382-011-1033-1&partnerID=40&md5=bbc43d76bc5afc1df85d3f5acf6d9265","This study builds upon two prior papers, which examine Arctic region bias of CAM3 (NCAR Community Atmosphere Model version 3) simulations during winter. CAM3 output is compared with ECMWF (European Centre for Medium-Range Weather Forecasts) 40 year reanalysis (ERA-40) data. Our prior papers considered the temperature and the vorticity equation terms and demonstrated that diabatic, transient, and linear terms dominate nonlinear bias terms over most areas of interest. Accordingly, this paper uses a linearized form of the model's dynamical core equations to study aspects of the forcing that lead to the CAM3 biases. We treat the model's long term winter bias as a solution to a linear stationary wave model (LSWM). Key features of the bias in the vorticity, temperature, and ln of surface pressure (=q) fields are shown at medium resolution. The important features found at medium resolution are captured at the much lower LSWM resolution. The Arctic q bias has two key features: excess q over the Barents Sea and a missing Beaufort High (negative maximum q bias) to the north of Alaska and eastern Siberia. The forcing fields are calculated by the LSWM. Horizontal advection tends to create multi-polar combinations of negative and positive extrema in the forcing. The positive and negative areas of forcing approximately match corresponding areas in the bias. There is a broad relation between cold bias with elevated q bias, as expected from classical theory. Forcing in related quantities: near surface vorticity and surface pressure combine to produce the sea level pressure bias. © 2011 The Author(s)."
"7006695342;","Contributions from the second and third internal gravity modes for the vertical motion response",2008,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-57649140444&partnerID=40&md5=55fe52f322a66fe6b8815131484c0da6","In earlier papers of a series of real data integrations of the National Center for Atmospheric Research Community Climate Model with tropical heat anomalies display regions of pronounced subsidence and drying located several thousand kilometers westward poleward of the heating for cases of tropical Atlantic heating and tropical east Pacific heating. This highly predictable sinking response is established within the first five days of these integrations. The normal-modes of a set of adiabatic primitive equations linearized about a basic state at rest are used to partition model response into gravity-inertia and Rossby modes. The most important contribution for the vertical motion response comes from the gravity modes added for all vertical modes. The principal emphasis is given upon the contributions of the second and third internal vertical modes (with equivalent depths on the order of a fews hundred meters) for the vertical motion response."
"7202343918;16242027100;","A godunov-type finite volume scheme for meso- and micro-scale flows in three dimensions",2008,"10.1007/s00024-008-0402-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58149089150&doi=10.1007%2fs00024-008-0402-0&partnerID=40&md5=6f9cdd091b04c7243241dce560170aa5","This short note reports the extension of the f-waves approximate Riemann solver (Ahmad and Lindeman, 2007; LeVeque, 2002; Bale et al., 2002) for three-dimensional meso- and micro-scale atmospheric flows. The Riemann solver employs flux-based wave decomposition for the calculation of Godunov fluxes and does not require the explicit definition of the Roe matrix to enforce conservation. The other important feature of the Riemann solver is its ability to incorporate source term due to gravity without introducing discretization errors. The resulting finite volume scheme is second-order accurate in space and time. The finite-difference schemes currently used in atmospheric flow models are neither conservative nor able to resolve regions of sharp gradients. The finite volume scheme described in this paper is fully conservative and has the ability to resolve regions of sharp gradients without introducing spurious oscillations in the solution. The scheme shows promise in accurately resolving flows on the meso- and micro-scales and should be considered for implementation in the dynamical cores of next generation meso- and micro-scale atmospheric flow models. © Birkhaueser 2008."
"6603638928;7004274115;","An Atmospheric Model of Intermediate Complexity for data assimilation studies",2008,"10.1002/qj.329","https://www.scopus.com/inward/record.uri?eid=2-s2.0-57349145469&doi=10.1002%2fqj.329&partnerID=40&md5=032603b0bad5be24bdc58d0858c05d74","Atmospheric models of intermediate complexity play an important role when studying atmospheric phenomena. Their complexity is between highly truncated low-dimensional 'toy' models and modern general circulation or numerical weather prediction models. By design, computational cost associated with intermediate models is much reduced while at the same time some important aspects of atmospheric behaviour are still reasonably realistically described. Performing numerical experimentation with such models in the contexts of data assimilation, predictability, and atmospheric dynamics can produce informative results regarding those aspects for comparatively low cost. Nevertheless, as with any model-based study, the degree to which results so obtained may be generalized to more realistic conditions remains somewhat uncertain and dependent on the specific questions being considered. An intermediate-complexity model, named AMIC (Atmospheric Model of Intermediate Complexity) based on the nonlinear quasi-geostrophic potential vorticity equation is presented. This global model uses a spectral dynamical core, and contains 'physical processes', such as climatological forcing, diffusion, and damping, designed to reasonably match AMIC's behaviour with observed atmospheric properties. While AMIC has variable horizontal and vertical resolution, the properties of AMIC are studied here for two specific resolutions (T45L6 and T106L9) and these are compared against atmospheric properties in terms of energy spectra, time-mean and transient behaviour, and singular-vector perturbation growth. The model's behaviour is reasonably realistic, except for its transient activity being somewhat weak, especially in the southern (summer) hemisphere. AMIC is also suited for some data assimilation and predictability studies since it contains complete tangent-linear and adjoint models. Copyright © 2008 Royal Meteorological Society."
"56099025500;56962915800;7406308680;57202299549;15839397900;","Comparison between GAMIL, and CAM2 on interannual variability simulation",2007,"10.1007/s00376-007-0082-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846783258&doi=10.1007%2fs00376-007-0082-1&partnerID=40&md5=13455ee2b36d5bb90c7453ab653ce2fd","Recently, a new atmospheric general circulation model (GAMIL: Grid-point Atmospheric Model of IAP LASG) has been developed at the Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS), which is based on the Community Atmospheric Model Version 2 (CAM2) of the National Center for Atmospheric Research (NCAR). Since the two models have the same physical processes but different dynamical cores, the interannual variability simulation performances of the two models are compared. The ensemble approach is used to reduce model internal variability. In general, the simulation performances of the two models are similar. Both models have good performance in simulating total space-time variability and the Southern Oscillation Index. GAMIL performs better in the Eastern Asian winter circulation simulation than CAM2, and the model internal variability of GAMIL has a better response to external forcing than that of CAM2. These indicate that the improvement of the dynamic core is very important. It is also verified that there is less predictability in the middle and high latitudes than in the low latitudes."
"6603638928;","A vector derivation of the semigeostrophic potential vorticity equation",2004,"10.1175/1520-0469(2004)061<1461:AVDOTS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-3242713282&doi=10.1175%2f1520-0469%282004%29061%3c1461%3aAVDOTS%3e2.0.CO%3b2&partnerID=40&md5=fc3f992dfbf631d807db9f94ccf47c57","The semigeostrophic potential vorticity equation is derived in a vector-based notation for the shallow-water and primitive equations, as models for atmospheric flow. The derivation proceeds from knowledge of the functional form of potential vorticity and starts directly from a vector form of the governing equations. The method makes use of highly involved vector identities and provides for a clearer picture of the nature of the final result, as compared to a component-based derivation. It is, however, limited by the need to know a priori the appropriate functional vector form of the dynamically relevant quantity, such as potential vorticity. © 2004 American Meteorological Society."
"6602418877;7102836087;","Nonlinear balanced simulation of a baroclinic wave",2002,"10.1256/003590002320603458","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0036653897&doi=10.1256%2f003590002320603458&partnerID=40&md5=cfefe87b697da674a949a617c8f8ce91","The nonlinear balanced time integration of a baroclinic wave with a model applicable for synoptic and mesoscale weather systems and based on the conservation of the Ertel-Rossby potential vorticity (PV) is presented. The simulation is performed for a realistic, but idealized, atmospheric configuration involving troposphere, stratosphere and flexible tropopause. The balanced model, compared with the primitive equation (PE) one, proves to be highly accurate. The balanced integration allowed strict implementation of the conservation of PV for the simulation of frontal processes, without generation of spurious low-level PV anomalies, which emerge in PE simulations of baroclinic waves in the region of frontal collapse. Also, a hypothesis is formulated on the substantial role of these PV anomalies in the baroclinic amplification of the modelled PE baroclinic wave at advanced stages of its evolution."
"7402899368;7404574877;6701387222;","Monsoonlike circulations in a zonally averaged numerical model with topography",2000,"10.1175/1520-0493(2000)128<0779:MCIAZA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5544312277&doi=10.1175%2f1520-0493%282000%29128%3c0779%3aMCIAZA%3e2.0.CO%3b2&partnerID=40&md5=f290cab31dee21b3596cdec35e26257e","A primitive equation global zonally averaged general circulation model is used to study the effects of the topography on the atmospheric annual cycle. A smoothed zonally averaged topography that has a form similar to that observed was used. The control experiment showed that the model was capable of capturing the zonally averaged behavior of the annual cycle. The model is able to capture some characteristics of the monsoonlike circulation such as the seasonal wind reversal and the easterly jet in the boreal summer. Even in the absence of topography the model was able to reproduce the monsoonlike features. However, the circulation was weak and the position of its components was altered. This suggests that the topography has an important role in modifying the intensity and position of the monsoon circulation. Sensitivity tests were made in order to investigate the effects of high elevation and its steep southern slope. Two experiments were performed: 1) increasing the elevation of orography without changing the steepness of the slope, and 2) increasing both the elevation and the steepness of the slope. The results indicated that the steepness of the southern slope seems to control the monsoonlike flow in the model. The model was also capable of reproducing a monsoonlike response to changed external conditions. When the values of the earth's orbital parameters (precession, obliquity, and eccentricity) were changed to those of 9000 yr BP, the precipitation and circulation intensified, which seems to agree with paleoclimatic evidence."
"6603615408;","On the vertical velocity in an isentropic layer",2000,"10.1002/qj.49712656213","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034077223&doi=10.1002%2fqj.49712656213&partnerID=40&md5=63b9c7990a07fa7ff7b942f79e09be95","We investigate the dynamics of an isentropic layer of air, governed by the hydrostatic primitive equations. In such a layer the horizontal velocity is independent of height if this is assumed to be the case at some initial time. From the mass-conservation equation in pressure coordinates it follows that ω, the material derivative of the pressure, varies linearly with pressure. From the mass-conservation equation in height coordinates the vertical velocity w is obtained. The resulting expression is shown to be in accordance with Richardson's equation for the vertical velocity in a general hydrostatic atmosphere, when particularized to an isentropic layer."
"23020888000;7103002829;6602280557;","On the variety of cold fronts: Two-dimensional numerical simulations",1997,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031421690&partnerID=40&md5=7a05d2a45bb352309ed14978654fecee","This paper demonstrates the large variety of cold front structure patterns in contrast to the simple conceptional two-type system of ana-cold fronts and kata-cold fronts. It also pleads for thinking in hydrodynamical terms such as frontal gradients (instead of materialized air-mass boundaries), along-frontal jets (instead of two-dimensional conveyor belts) and ageostrophic cross-frontal circulations (instead of e.g. cold air wedge movements) as the main causes for the development of clouds and precipitation. The large variety of cold front structure patterns is investigated by means of a two-dimensional model based on the primitive equations and taking into account moisture and turbulence processes. The cases studied are purely synthetic, which allows for a clear separation of different sources of influence on frontal structure and weather events. Precipitation structure and weather events are strongly linked to the ageostrophic cross-frontal circulation, which shows an immense variety due to different basic frontal temperature fields (e.g. shallow or deep cold fronts), the kind of synoptic-scale forcing (e.g. deformation or shear), instabilities and friction and diabatic effects. The latter are linked to boundary-layer processes to a high degree, and partly depend on the energy balance and thus on the net radiation and the turbulent fluxes of sensible and latent heat at the earth's surface, which all reveal a large daily variation; the ratio of the turbulent fluxes appears to be strongly linked to whether the surface is wet or dry. Additional effects stem from along-front inhomogeneities, as for example of atmospheric humidity. In this paper selected simulations try to systematically present all these influences in their role of structuring the frontal patterns."
"55698113600;7402872647;","Effects of Land-Sea Distribution, Topography and Diurnal Change on Summer Monsoon Modeling",1996,"10.1007/bf02656867","https://www.scopus.com/inward/record.uri?eid=2-s2.0-2742579325&doi=10.1007%2fbf02656867&partnerID=40&md5=612f92796f083b11a4a7a6f3fe39b4b8","The effects of the land-sea distribution, the topography and the diurnal change of the solar radiation on the summer monsoon modelings are studied by use of a coupled modeling system with a 5-layer primitive equation model of the atmosphere and a 2-layer soil or ocean thermodynamic model which are all solved in a zonal model domain between 60°S and 60°N. The results of numerical simulations show that the quasi-stationary patterns of the mean monsoon circulations are mainly affected by the land-sea distribution and the topography, the effect of the diurnal change is the secondary. However, the inclusion of the diurnal change into the model system may improve the intensity of the simulated monsoon circulation, it can influence the distributive pattern of precipitation to a larger extent, without the diurnal change precipitation in the interior of land would decrease and in the coastal regions it would increase."
"6603340584;7406423941;","On the use of the Boussinesq equations, the reduced system, and the primitive equations for the computation of geophysical flows",1996,"10.1016/0377-0265(95)00466-1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030468766&doi=10.1016%2f0377-0265%2895%2900466-1&partnerID=40&md5=c3e2a066b7655650ac1a56b011d56a52","Motivated in part by the mathematical problems associated with the application of open boundary conditions to the hydrostatic primitive equations (PE), Browning et al. (1990, Dyn. Atmos. Oceans, 14: 303-332) proposed the use of the reduced system (RS) of equations to replace PE for oceanographic problems. The RS are essentially the Boussinesq equations (BO) with the non-hydrostatic terms in the vertical momentum equation multiplied by a constant δ2 ≫ 1. This artificially alters the physics (e.g. changing the internal-inertial wave properties) to facilitate numerical integration, but the changes are assumed to have negligible effects on the dynamics of interest. We assess the accuracy and utility of the RS (following the guidelines for the choice of δ) by comparing numerical finite difference solutions of RS, PE and BO for initial-value problems involving three-dimensional instability of an ocean front and atmospheric frontal development in a two-dimensional Eady wave. Both explicit (BO, PE) and semi-implicit (BOSI, PESI) time-difference schemes are used for the Boussinesq and primitive equations. For RS, the same explicit scheme as for BO is used where δ ≫ 1 allows larger time steps than with the other explicit models. It is found that relative to BO solutions, the errors for RS are small but increase rapidly and monotonically with increasing δ (over a range consistent with the guidelines) and are greater than the errors for the other models. The use of BOSI allows time steps at least as large as those for RS and results in smaller errors than RS. For these problems, BOSI is the preferable model to replace PE."
"57196965502;36892259600;","Relationships between heat fluxes and temperature gradients in a global spectral model",1996,"10.1175/1520-0469(1996)053<3653:RBHFAT>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030323904&doi=10.1175%2f1520-0469%281996%29053%3c3653%3aRBHFAT%3e2.0.CO%3b2&partnerID=40&md5=0bd134e6203dfec320dcef6341a64771","Two conceptual paradigms have been used in the past to interpret the observed strength and structure of eddy heat fluxes in the atmosphere. One is the idea of 'adjustment', whereby the eddies respond efficiently to changes in forcing to maintain the mean isentropic slope. The other is a 'diffusive' paradigm, which assumes that eddy fluxes can be parameterized in terms of the mean flow. The relative merits of these two approaches are examined here with the aid of a two-level primitive equations model in a sphere. Experiments show that, while the dynamical fluxes adjust to the forcing quickly and efficiently to balance the heat budget, the mean temperature gradients can continue to slowly evolve. The model exhibits elements of both baroclinic adjustment and diffusive behavior. Adjustment operates in the sense that isentropic slopes are relatively independent of the forcing and depend only weakly on the fluxes. Diffusion works in the sense that apparently unique flux-temperature gradient relationships eventually assert themselves, however slowly. Eddy heat flux sensitivity to mean temperature gradients is in broad agreement with recent parameterization theory, given the constraints inherent in the two-level model and the structure of the forcing used in the experiments."
"7401945370;","Hadley circulations and large-scale motions of moist convection in the two-dimensional numerical model",1995,"10.2151/jmsj1965.73.6_1059","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21344465814&doi=10.2151%2fjmsj1965.73.6_1059&partnerID=40&md5=2f3105367955331f5080f20dc8593cd5","As a tool for understanding the meridional circulation of the atmosphere, a two-dimensional (latitude-height) numerical model is used to clarify the relationship between the Hadley circulation and large-scale motions associated with moist convection. The model is based on the primitive equations including the moist process, and two kinds of coordinates are used: the spherical coordinate and the Cartesian coordinate with a uniform rotation. The surface temperature is externally fixed and the troposphere is cooled by the radiation; unstable stratification generates large-scale convective motions. Dependencies on the surface temperature difference from north to south 4TS are investigated. The numerical results show that a systematic multi-cell structure exists in every experiment. If the surface temperature is constant (δ Ts=0), convective motions are organized on the scale of the Rossby deformation radius and their precipitation patterns have a periodicity of the advective time TD. As δTs becomes larger, the organized convective system tends to propagate toward warmer regions. The convective cells calculated in the Cartesian coordinate model are very similar to those of the mid-latitudes in the spherical coordinate model. As the convective cells approach the equator, their cell scales become larger. In particular, in the case of the symmetric condition about the equator, the Hadley cell can be regarded as one of the convective cells which exists at the equator. © 1995, Meteorological Society of Japan."
"7102366816;7102835431;7004332887;57204410953;","Upper ocean modeling in a coastal bay",1995,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-19244371163&partnerID=40&md5=26ae84b6107cda6d07098536eea9fb2a","A numerical model of the upper ocean is developed to study the dynamics and thermodynamics of the Baie des Chaleurs (Gulf of St. Lawrence, Canada). The model has primitive equation dynamics with two active layers embedded with a Niiler-Kraus (Niller and Kraus, 1977) type mixed layer model at the top. The model is eddy-permitting, with a horizontal grid spacing at 2 X 4 km. Forced by observed wind, atmospheric heat fluxes, river runoff, and appropriate remote forcing (in particular, the Gaspe Current, (GC)), the model demonstrates that the mean cyclonic general circulation pattern in the bay is a consequence of the intrusion of the GC. The local mixed layer fluctuations are controlled by wind and GC induced divergence. The entrainment (and its corresponding heat flux) is important at the western part of the bay and changes the mean mixed layer depth on a timescale of more than a week. (from Authors)"
"7202643047;","Tropical storm motion and structure in a fine mesh primitive equation model",1992,"10.1007/BF01025509","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249832622&doi=10.1007%2fBF01025509&partnerID=40&md5=1bd52f14989539089acfac452a0391cc","Convective to planetary scale processes govern the motion and structure of tropical storms. A model with a high resolution and a large domain is required for accurate prediction of a storm's track and intensity. A series of integrations are performed using a primitive equation model and an initial state that defines a tropical storm that later developed into a hurricane in the real atmosphere. Increasing the horizontal resolution or domain of the model improves the forecast track. However only the increase in the horizontal resolution produces a better hurricane structure. Banded structure in the vertical motion field, asymmetries in the low tropospheric winds similar to those observed and upper tropospheric cyclonic outflow develop in high horizontal resolution experiments. It is shown that horizontal advection and pressure gradient terms produce wind tendencies in the low troposphere that displace the vortex in the observed direction. A high pressure area surrounding the central low pressure area appears in the upper troposphere. Around this high pressure area large pressure gradients develop that induce outflow winds in the distal storm area. © 1992 Springer-Verlag."
"7006245928;7102486629;","Predictability of the tropical Atlantic Ocean",1991,"10.1016/0924-7963(91)90035-S","https://www.scopus.com/inward/record.uri?eid=2-s2.0-27744464070&doi=10.1016%2f0924-7963%2891%2990035-S&partnerID=40&md5=0694f729505a39990a4f4a139bf004d0","We have used a primitive equation multi-level model of the tropical Atlantic Ocean to calculate the time evolution of sea surface temperature and ocean circulation due to a prescribed surface stress forcing for a given year. We have then repeated the model integration starting from the same initial oceanic state as the first integration but with quite different surface stress forcing given by atmospheric observations from another year. We have examined the rate at which the differences between the two model-simulated ocean states grow with time and find that it takes only about three months for the differences to grow from zero to their saturation value. We have also examined the time growth of differences between two ocean model simulations for which the atmospheric forcing of surface stress was identical but the initial ocean states were quite different. In this case also, we find that it takes only about three months for the initial large differences to decay to their minimum value. The results of these experiments lead to the following conclusions: (1) In the absence of accurate surface forcing, an accurate estimate of the ocean circulation at some initial time will lead to a reasonable estimate of circulation for only a few months. (2) Given accurate surface forcing, errors in the thermal and velocity structure of the ocean decrease rapidly within a few months. However some residual error will remain. © 1991."
"6506028155;","Numerical experiments of the effects of initial desert moisture on the climate change",1991,"10.1007/BF02919268","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0010817795&doi=10.1007%2fBF02919268&partnerID=40&md5=8abfa5dc7d92fde4653066122d41c791","A numerical model with the p-sigma incorporated coordinate system and primitive equations is used to simulate the effect of initial soil moisture in desert areas on the climate change. The results show that the present deserts have a tendency to expand. When the initial soil moisture in the desert regions increases, the desert areas will shrink but can not disappear. The small deserts may not remain any longer when there are sources of water vapour around. Both the land-sea contrast and the topography are the background conditions of the present desert distribution through the mechanism of the downdrafts and the rare precipitation over the desert regions. The increase of the initial desert soil moisture will weaken the summer monsoon circulation and, consequently, the monsoonal precipitation. © 1990, Advances in Atmospheric Sciences. All rights reserved."
"57203088316;7203088566;","A multi‐level limited‐area slow‐equation model: Application to initialization",1990,"10.1002/qj.49711649305","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025634691&doi=10.1002%2fqj.49711649305&partnerID=40&md5=9aaf1e0af6f63e5e67d9c75db548d1a7","A multi‐level limited‐area model based on the slow equations is formulated, and applied to the problem of initializing data for a primitive‐equation forecast. the slow equations comprise a filtered system whose linear solutions correspond to the low‐frequency atmospheric motions. There are no solutions corresponding to the high‐frequency gravity‐wave solutions of the primitive equations. The model is used to initialize data for a primitive‐equation forecast. It is successful in eliminating high‐frequency noise without causing any significant changes in the forecast. the method converges well even when all vertical modes are initialized. Copyright © 1990 Royal Meteorological Society"
"57192504085;7401806579;24786064000;","Nonlinear baroclinic haurwitz waves",1986,"10.1007/BF02678653","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649152488&doi=10.1007%2fBF02678653&partnerID=40&md5=2abb76ca3b41b71ffe946f147d1b3f3b","A family of nonlinear wave solutions, with Haurwitz waves as their zero-order approximations, to the baroclinic primitive equations is derived and the corresponding calculating system is presented. Numerical experiments with a two-level global model developed by ourselves confirm the validity of the theoretical results to a great extent. © 1986 Advances in Atmospheric Sciences."
"7004274115;","The statistical equilibrium solution of a primitive‐equation model",1984,"10.1111/j.1600-0870.1984.tb00221.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977722063&doi=10.1111%2fj.1600-0870.1984.tb00221.x&partnerID=40&md5=e936670ae5f8f0c86bcfad7f8d64b882","The statistical equilibrium solution of an f‐plane, primitive‐equation model with a single quadratic energy invariant is determined by numerical integration. The initial condition resembles the atmosphere in terms of the shape and magnitude of its energy spectrum. The equilibrium solution is one in which energy is equipartitioned among all the linearly independent modes of the system. This state is attained after two simulated years. The approach to equilibrium is explored in detail. It is characterized by (at least) two stages. The first is dominated by quasi‐geostrophic dynamics and nonlinear balances. The approximate conservation of quasi‐geostrophic potential enstrophy is important during this stage, so that the solution initially tends to the equilibrium solution of a quasi‐geostrophic form of the model. The second stage is characterized by a very slow transfer of energy from geostrophic modes to inertial‐gravity waves. The rate of transfer of energy during this stage is shown to be very sensitive to initial conditions. 1984 Blackwell Munksgaard"
"7409883762;7409892653;","Numerical experiments on nonlinear waves in barotropic atmosphere.",1983,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020860632&partnerID=40&md5=b72947a752966ec59a8ff8a2b4c0c00f","The existence of nonlinear non-dispersive wave solutions to the barotropic primitive equations is confirmed by using numerical experiments. The general characters of this family of waves are also investigated.-Authors"
"6507963425;","STUDY OF THE ADEQUACY OF QUASI-GEOSTROPHIC DYNAMICS FOR MODELING THE EFFECT OF CYCLONE WAVES ON THE LARGER SCALE FLOW.",1982,"10.1175/1520-0469(1982)039<2414:ASOTAO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020203640&doi=10.1175%2f1520-0469%281982%29039%3c2414%3aASOTAO%3e2.0.CO%3b2&partnerID=40&md5=7557f7da4a252a5fa27de1987b952e1c","The development of long-range ″climate forecast″ models depends, in part, on the ability to simulate the effect upon the surrounding atmosphere of the day-to-day evolution of cyclone waves. The purpose of this work is to study the evolution of cyclone waves to see how well a set of quasi-geostrophic (QG) equations can reproduce the behavior of more complete primitive equations (PE). The effect of the cyclone life cycle on the surrounding atmospheric temperature structure is examined. No attempt is made to develop a ″climate forecast″ model."
"57192748880;","Numerical Experiments of Orographic Effect on the Large Scale Motion of the Atmosphere",1976,"10.2467/mripapers1950.27.1_1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85007857542&doi=10.2467%2fmripapers1950.27.1_1&partnerID=40&md5=f5c9b9dec32e7011712550ed350eee7a","The numerical experiments of the orographic-dynamic effects upon the large scale motion of the atmosphere are made by use of the 3-level primitive equation model, in which the pressure coordinate system is adopted for the vertical. The experiments for the simple flows result in good agreement with the theoretical linear solutions, when the relatively low mountains are included. However, the results in cases where the high mountains are included, show that the flows eventually turn around the obstacles rather than pass over them, resulting in relatively small amplitudes. Other experiments are made for the baroclinic flows and the various mountains. From these, it is seen that a stationary trough appears on the lee side of the mountains in connection with relatively strong winds over the high and wide mountain barriers. © 1976, Japan Meteorological Agency. All rights reserved."
"57190242570;6603867727;","A pressure oscillation in a 10‐level atmospheric model",1968,"10.1002/qj.49709440002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978549736&doi=10.1002%2fqj.49709440002&partnerID=40&md5=36aba82c28b4443de5c43615a94c2e06","A pressure oscillation in the 10‐level primitive equation model of Bushby and Timpson (1967) has been diagnosed as a standing inertio‐gravitational wave in the external mode. A small modification to the linearized balance equation used to define the initial state has resulted in its elimination. Although the broad development of the pressure field is unaffected, significant changes have appeared in the rainfall. The speed of propagation of external gravity waves in the model is about 285 m/s, substantially less than for a comparable continuous atmosphere. Copyright © 1968 Royal Meteorological Society"
"57205834261;57192343476;","Numerical Test of the Finite-Difference form of the Primitive Equations for a Barotropic Model Including Orography",1963,"10.2467/mripapers1950.14.1_1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84932391589&doi=10.2467%2fmripapers1950.14.1_1&partnerID=40&md5=46eaa8477a9663960d7d4c58603b8982","The finite-difference scheme of the primitive equations was derived and tested in the so-called x, y, σ-coordinate system which contains the ground as a coordinate surface. The system is suitable for taking into consideration the effect of orography upon the atmospheric motion. The numerical test was attempted for the flow against the bellshaped mountain in a homogeneous and incompressible atmosphere. The results showed the reasonable patterns of pressure and wind, that is, the configuration of trough, ridge, jet core, divergence and vorticity as expected. According to the numerical solution we obtained, our finite-difference scheme seems to be computationally stable and there appears no trouble through 48-hour forecast. Besides, the conservation of the total energy in the forecasting domain was satisfied so accurately that it varied within the range less than 0.03% of the initial value at 48-hour forecast. © 1963, Japan Meteorological Agency. All rights reserved."
"57146578400;26023688200;","The FastEddy® Resident-GPU Accelerated Large-Eddy Simulation Framework: Model Formulation, Dynamical-Core Validation and Performance Benchmarks",2020,"10.1029/2020MS002100","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096422541&doi=10.1029%2f2020MS002100&partnerID=40&md5=308afcb9e08f325f90077b91ff968100","This paper introduces a new large-eddy simulation model, FastEddy®, purpose built for leveraging the accelerated and more power-efficient computing capacity of graphics processing units (GPUs) toward adopting microscale turbulence-resolving atmospheric boundary layer simulations into future numerical weather prediction activities. Here a basis for future endeavors with the FastEddy® model is provided by describing the model dry dynamics formulation and investigating several validation scenarios that establish a baseline of model predictive skill for canonical neutral, convective, and stable boundary layer regimes, along with boundary layer flow over heterogeneous terrain. The current FastEddy® GPU performance and efficiency gains versus similarly formulated, state-of-the-art CPU-based models is determined through scaling tests as 1 GPU to 256 CPU cores. At this ratio of GPUs to CPU cores, FastEddy® achieves 6 times faster prediction rate than commensurate CPU models under equivalent power consumption. Alternatively, FastEddy® uses 8 times less power at this ratio under equivalent CPU/GPU prediction rate. The accelerated performance and efficiency gains of the FastEddy® model permit more broad application of large-eddy simulation to emerging atmospheric boundary layer research topics through substantial reduction of computational resource requirements and increase in model prediction rate. ©2020. The Authors."
"57202299549;7201356364;57211514968;36620610200;8643534400;56494048400;7006705919;57217344414;7005920812;55544607500;","Improving Time Step Convergence in an Atmosphere Model With Simplified Physics: The Impacts of Closure Assumption and Process Coupling",2020,"10.1029/2019MS001982","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094099626&doi=10.1029%2f2019MS001982&partnerID=40&md5=5cadd6beb1bf6fa7720325cef076c245","Convergence testing is a common practice in the development of dynamical cores of atmospheric models but is not as often exercised for the parameterization of subgrid physics. An earlier study revealed that the stratiform cloud parameterizations in several predecessors of the Energy Exascale Earth System Model (E3SM) showed strong time step sensitivity and slower-than-expected convergence when the model's time step was systematically refined. In this work, a simplified atmosphere model is configured that consists of the spectral-element dynamical core of the E3SM atmosphere model coupled with a large-scale condensation parameterization based on commonly used assumptions. This simplified model also resembles E3SM and its predecessors in the numerical implementation of process coupling and shows poor time step convergence in short ensemble tests. We present a formal error analysis to reveal the expected time step convergence rate and the conditions for obtaining such convergence. Numerical experiments are conducted to investigate the root causes of convergence problems. We show that revisions in the process coupling and closure assumption help to improve convergence in short simulations using the simplified model; the same revisions applied to a full atmosphere model lead to significant changes in the simulated long-term climate. This work demonstrates that causes of convergence issues in atmospheric simulations can be understood by combining analyses from physical and mathematical perspectives. Addressing convergence issues can help to obtain a discrete model that is more consistent with the intended representation of the physical phenomena. © 2020. The Authors."
"57219232158;57219227529;38863214100;","Small Sensitivity of the Simulated Climate of Tidally Locked Aquaplanets to Model Resolution",2020,"10.3847/1538-4357/ab9b83","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091750027&doi=10.3847%2f1538-4357%2fab9b83&partnerID=40&md5=9bf100e7be0424f5f28469af1aa9f26d","Tidally locked terrestrial planets around low-mass stars are the prime targets of finding potentially habitable exoplanets. Several atmospheric general circulation models have been employed to simulate their possible climates; however, model intercomparisons showed that there are large differences in the results of the models even when they are forced with the same boundary conditions. In this paper, we examine whether model resolution contributes to the differences. Using the atmospheric general circulation model ExoCAM coupled to a 50 m slab ocean, we examine three different horizontal resolutions (440 km × 550 km, 210 km × 280 km, and 50 km × 70 km in latitude and longitude) and three different vertical resolutions (26, 51, and 74 levels) under the same dynamical core and the same schemes of radiation, convection, and clouds. Among the experiments, the differences are within 5 K in global-mean surface temperature and within 0.007 in planetary albedo. These differences are from cloud feedback, water vapor feedback, and the decreasing trend of relative humidity with increasing resolution. Relatively small-scale downdrafts between upwelling columns over the substellar region are better resolved and the mixing between dry and wet air parcels and between anvil clouds and their environment are enhanced as the resolution is increased. These reduce atmospheric relative humidity and high-level cloud fraction, causing a lower clear-sky greenhouse effect, a weaker cloud longwave radiation effect, and subsequently a cooler climate with increasing model resolution. Overall, the sensitivity of the simulated climate of tidally locked aquaplanets to model resolution is small. © 2020. The American Astronomical Society. All rights reserved.."
"44561454300;56322979700;","Spontaneous inertia-gravity wave emission from a nonlinear critical layer in the stratosphere",2020,"10.1002/qj.3750","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85079893995&doi=10.1002%2fqj.3750&partnerID=40&md5=07a85aabc057ffd5d22536265b9fec63","Using a nonlinear global primitive equation model, spontaneous inertia-gravity wave (IGW) emission is investigated in an idealized representation of the stratospheric polar night. It is shown that IGWs are spontaneously emitted in the interior of the fluid in a jet exit region that develops around a nonlinear Rossby wave critical layer. Two key ingredients for the generation are identified: the presence of a Rossby wave guide on the polar night jet; and a zero wind line on the jet flank that gives rise to nonlinear Rossby wave breaking and strong distortion of the flow. The emission of IGWs appears here as a quasi-steady process that begins at a well-defined time when the flow deformation becomes large enough. Part of the emitted IGWs undergoes wave capture by the cat's-eye flow in a Rossby wave critical layer. Another part – in the form of a well-defined IGW packet – escapes the wave capture limit, and propagates away into the far field. The propagating wave packet is numerically well-converged to increases in both vertical and horizontal resolution and thus provides an ideal test bed for understanding IGW emission and informing non-orographic gravity wave drag parametrization design. © 2020 Royal Meteorological Society"
"57030797300;57204109988;57111001300;","Sensitivity of the Latitude of the Westerly Jet Stream to Climate Forcing",2020,"10.1029/2019GL086563","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081076388&doi=10.1029%2f2019GL086563&partnerID=40&md5=be64f6136d8f52f68655fb5f4703890b","The latitude of the westerly jet stream is influenced by a variety of climate forcings, but their effects on the jet latitude often manifest as a tug of war between tropical forcing (e.g., tropical upper-tropospheric warming) and polar forcing (e.g., Antarctic stratospheric cooling or Arctic amplification). Here we present a unified forcing-feedback framework relating different climate forcings to their forced jet changes, in which the interactions between the westerly jet and synoptic eddies are synthesized by a zonal advection feedback, analogous to the feedback framework for assessing climate sensitivity. This framework is supported by a prototype feedback analysis in the atmospheric dynamical core of a climate model with diverse thermal and mechanical forcings. Our analysis indicates that the latitude of a westerly jet is most sensitive to the climate change-induced jet speed changes near the tropopause. The equatorward jet shift also displays a larger deviation from linearity than the poleward counterpart. ©2020. American Geophysical Union. All Rights Reserved."
"56452114900;7203047936;","Development of the tangent linear and adjoint models of the MPAS-Atmosphere dynamic core and applications in adjoint relative sensitivity studies",2020,"10.1080/16000870.2020.1814602","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091144166&doi=10.1080%2f16000870.2020.1814602&partnerID=40&md5=c6360f5328f92a5895182903ec446d37","This study develops and tests a version of the Python-driven, non-hydrostatic Model for Prediction Across Scales–Atmosphere (MPAS-A) dynamic model, as well as its tangent linear and adjoint models. The non-linear, non-hydrostatic dynamic core of the MPAS-A is restructured to have a Python driver for the convenience of parsing namelists, manipulating matrices, controlling simulation time flows, reading model inputs, and writing outputs, while the heavy-duty mediation and model layers are retained in Fortran for computational efficiency. Under the same Python-driving structure, developed are the tangent linear and adjoint models for the dynamic core of the MPAS-A model with verified correctness. The case of Jablonowski and Williamson’s baroclinic wave is used for demonstrating the approximation accuracy of the MPAS-A tangent linear model and the applicability of the MPAS-A adjoint model to relative sensitivity studies. Numerical experimental results show that the tangent linear model can well approximate the temporal evolutions of non-linear model perturbations for all model variables over a four-day forecast period. Employing the MPAS-A adjoint model, it is shown that the most sensitive regions of the 24-h forecast of surface pressure are weather dependent. An interesting westward vertical tilting is also found in the relative sensitivity results of a 24-h forecast of surface pressure at a point located within a trough to model initial conditions. This functionality of the MPAS-A adjoint model is highly essential in understanding dynamics and variational data assimilation. Plain Language Summary The MPAS-A is an advanced global numerical weather prediction model with a hexagonal mesh that can be compressed for higher resolutions in some targeted regions of interest and smoothly transitioned to coarse resolutions in others. In this study, a Python-driven MPAS-A model is first developed, combining a flexible Python driver and Fortran’s fast computation, making the MPAS-A model exceedingly user- and platform-friendly. The tangent linear and adjoint models of the MPAS-A dynamical core are then developed, both of which are required for various sensitivity studies. They are also indispensable components of a future MPAS-based global four-dimensional variational (4D-Var) data assimilation system. Finally, the relative sensitivity of a baroclinic instability wave development is obtained and shown using the MPAS-A adjoint model. © Tellus A: 2020. © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group."
"37124192900;7006328089;57203056581;","Atmospheric bistability and abrupt transitions to superrotation: Wave–jet resonance and Hadley cell feedbacks",2020,"10.1175/JAS-D-19-0089.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081554790&doi=10.1175%2fJAS-D-19-0089.1&partnerID=40&md5=46fc87ea6dfe4c2ef8dd074138cf4f29","Strong eastward jets at the equator have been observed in many planetary atmospheres and simulated in numerical models of varying complexity. However, the nature of the transition from a conventional state of the general circulation, with easterlies or weak westerlies in the tropics, to such a superrotating state remains unclear. Is it abrupt or continuous? This question may have far-reaching consequences, as it may provide a mechanism for abrupt climate change in a planetary atmosphere, both through the loss of stability of the conventional circulation and through potential noise-induced transitions in the bistability range. We study two previously suggested feedbacks that may lead to bistability between a conventional and a superrotating state: the Hadley cell feedback and a wave–jet resonance feedback. We delineate the regime of applicability of these two mechanisms in a simple model of zonal acceleration budget at the equator. Then we show using numerical simulations of the axisymmetric primitive equations that the wave–jet resonance feedback indeed leads to robust bistability, while the bistability governed by the Hadley cell feedback, although observed in our numerical simulations, is much more fragile in a multilevel model. © 2019 American Meteorological Society."
"6602940687;","Spectral characteristics of strain-dependent eddy viscosity",2020,"10.1175/1520-0469(1977)034<1816:scosde>2.0.co;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0013723422&doi=10.1175%2f1520-0469%281977%29034%3c1816%3ascosde%3e2.0.co%3b2&partnerID=40&md5=0385bed0a7b0cb77521c78e9247cc55f","The spectral dependence and numerically estimated values of Kraichnan's numerically determined effective eddy viscosity in a test field model of two- and three-dimensional isotropic flow are compared to those of a strain-dependent eddy viscosity formula suggested by Smagorinsky (1963) and frequently used in spatially differenced primitive equation models of the atmosphere. The effective eddy viscosities are said to be in general agreement in the three- dimensional case. (based on Author's abstract)"
"36620610200;56607014000;7401431508;31067496800;7201356364;","Evaluation of Implicit-Explicit Additive Runge-Kutta Integrators for the HOMME-NH Dynamical Core",2019,"10.1029/2019MS001700","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076367905&doi=10.1029%2f2019MS001700&partnerID=40&md5=425f179041ead7c1fdc4ce253423d94a","The nonhydrostatic High-Order Method Modeling Environment (HOMME-NH) atmospheric dynamical core supports acoustic waves that propagate significantly faster than the advective wind speed, thus greatly limiting the time step size that can be used with standard explicit time integration methods. Resolving acoustic waves is unnecessary for accurate climate and weather prediction. This numerical stiffness is addressed herein by considering implicit-explicit additive Runge-Kutta (ARK IMEX) methods that can treat the acoustic waves in a stable manner without requiring implicit treatment of nonstiff modes. Various ARK IMEX methods are evaluated for their efficiency in producing accurate solutions, ability to take large time step sizes, and sensitivity to grid cell length ratio. Both the gravity wave test and baroclinic instability test from the 2012 Dynamical Core Model Intercomparison Project are used to recommend 5 of the 27 ARK IMEX methods tested for use in HOMME-NH. ©2019. The Authors."
"6603724340;42961592400;","Elimination of spectral blocking by ensuring rotation-free property of discretized pressure gradient within a spectral semi-implicit semi-Lagrangian global atmospheric model",2019,"10.1002/qj.3636","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071607705&doi=10.1002%2fqj.3636&partnerID=40&md5=69c144e575e00620e0c818ac07e6d324","The widely-adopted discretization of the horizontal pressure gradient term formulated by Simmons and Burridge for atmospheric models on σ-p hybrid vertical coordinate is found to incur spectral blocking for rotational wind components at high vertical levels when used in a spectral semi-Lagrangian model run on a linear grid. A remedy to this issue is proposed and tested using a spectral semi-implicit semi-Lagrangian hydrostatic primitive equations model. The proposed method removes aliasing errors at high wave-numbers by ensuring that the rotation-free property of the pressure gradient term on the isobaric surface, a feature possessed by the continuous system, is preserved in the discretized system, which highlights the significance of mimetic discretization within the context of numerical weather prediction models. © 2019 Royal Meteorological Society"
"57202452734;23479549200;55823600500;57075971600;7004662136;","Simulating the Antarctic stratospheric vortex transport barrier: comparing the Unified Model to reanalysis",2019,"10.1007/s00382-018-4593-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059512317&doi=10.1007%2fs00382-018-4593-5&partnerID=40&md5=9bcf126e394a880e6c6c8d527cfbc865","An assessment has been made of the ability of the UK Met Office Unified Model (UM) to simulate the Antarctic stratospheric circumpolar vortex and, in particular, the extent to which the vortex acts as a barrier to meridional transport. It is important that models simulate this barrier well as it determines spatial gradients in radiatively active gases, such as ozone, which then determine the spatial morphology of the radiative forcing field. The assessment was made by comparing metrics of meridional impermeability calculated from dynamical fields extracted from UM simulations and from analogous fields obtained from NCEP-CFSR reanalysis. Two different UM configurations were assessed: global atmosphere 3.0 (GA3.0) using the New Dynamics dynamical core, and GA7.0 using the newer ENDGame dynamical core, with both versions run at N96 resolution (1.25∘ latitude by 1.875∘ longitude). The GA7.0 configuration appears to better simulate the dynamical isolation of the Antarctic stratospheric vortex in the lower stratosphere up to about 600 K, while GA3.0 provides a better simulation in the upper stratosphere. However, neither UM configuration simulates the same degree of dynamical isolation suggested by the reanalysis. In particular the UM configurations produce a wider and more poleward meridional band of high wind-speed and steep PV gradients when compared with the NCEP-CFSR reanalysis, leading to a stronger barrier in GA7.0 and a weaker barrier in GA3.0. Possible causes of discrepancies between model simulations and reanalysis and between the two model configurations are discussed. It is pointed out that further work is needed to identify ways of resolving these discrepancies in model simulations. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature."
"11939929300;57075896200;57195587405;55119602800;7103366892;","Explicit Prediction of Continental Convection in a Skillful Variable-Resolution Global Model",2019,"10.1029/2018MS001542","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068150812&doi=10.1029%2f2018MS001542&partnerID=40&md5=247c2b9969a55478b1c716f258923807","We present a new global-to-regional model, cfvGFS, able to explicitly (without parameterization) represent convection over part of the Earth. This model couples the Geophysical Fluid Dynamics Laboratory Finite-Volume Cubed-Sphere Dynamical Core (FV3) to the Global Forecast System physics and initial conditions, augmented with a six-category microphysics and a modified planetary boundary layer scheme. We examine the characteristics of cfvGFS on a 3-km continental U. S. domain nested within a 13-km global model. The nested cfvGFS still has good hemispheric skill comparable to or better than the operational Global Forecast System, while supercell thunderstorms, squall lines, and derechos are explicitly represented over the refined region. In particular, cfvGFS has excellent representations of fine-scale updraft helicity fields, an important proxy for severe weather forecasting. Precipitation biases are found to be smaller than in uniform-resolution global models and competitive with operational regional models; the 3-km domain also improves upon the global models in 2-m temperature and humidity skill. We discuss further development of cfvGFS and the prospects for a unified global-to-regional prediction system. ©2019. The Authors."
"57197707922;55500860200;55211425200;","The lagged connection of the positive NAO with the MJO phase 3 in a simplified atmospheric model",2019,"10.1007/s00704-018-2425-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045063904&doi=10.1007%2fs00704-018-2425-5&partnerID=40&md5=148207eb9ef0b26ec2a6ed3c6e8f3927","Based on a simplified nonlinear model and reanalysis data, the lagged connection of the North Atlantic Oscillation (NAO) with the Madden–Julian Oscillation (MJO) in boreal winters is investigated. The positive NAO is observed to occur more frequently about 8–20 days after the onset of the MJO phase 3. A series of heating forcing experiments and initial-value experiments are conducted by utilizing the Geophysical Fluid Dynamics Laboratory (GFDL) dynamical core atmospheric model. The extratropical responses to the tropical heating associated with the MJO phase 3 are characterized by a wave train over the Pacific–North American region with an anticyclone anomaly over the northeastern Pacific and then followed by a positive-NAO-like pattern over the North Atlantic sector. These circulation anomalies generally match the observed lagged-connection well. At the earlier stage, the Rossby wave train excited by the MJO convection propagates into the North Atlantic, leading to a planetary wave anomaly with a low-over-high dipole prior to the positive NAO. At the later stage, the anomalous synoptic eddy vorticity forcing (EVF) streamfunction tendency has a negative-over-positive dipole, which plays a key role in the development of the positive NAO. Further analysis of the initial-value experiments indicates that, for the subsequent formation of the positive NAO, the anomalous circulation over the Indian Ocean aroused by the MJO phase 3 is more crucial than that over the northeastern Pacific. © 2018, Springer-Verlag GmbH Austria, part of Springer Nature."
"57198906958;15765007300;7103282616;","Assessing adaptive mesh refinement (AMR) in a forced shallow-water model with moisture",2019,"10.1175/MWR-D-18-0392.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075575326&doi=10.1175%2fMWR-D-18-0392.1&partnerID=40&md5=469b7c95fbe999b9f948b75cf4c8731d","Two forced shallow-water flow scenarios are explored in a 2D fourth-order finite-volume dynamical core with adaptive mesh refinement (AMR) to investigate AMR’s ability to track and resolve complex evolving features. Traditional shallow-water test cases are mainly characterized by large-scale smooth flows that do not effectively test the multiscale abilities of variable-resolution and AMR models to resolve sharp gradients and small-scale flow filaments. Therefore, adding forcing mechanisms to the shallow-water system to model key atmospheric processes adds complexity and creates small-scale phenomena. These can serve as foci for dynamic grid refinement while remaining simple enough to study the numerical design of a model’s dynamical core. The first shallow-water flow scenario represents a strengthening, tropical cyclone–like, vortex that is driven by a Betts–Miller-like convection scheme. The second shallow-water test is built upon a barotropically unstable jet with an added Kessler-like warm rain scheme that leads to precipitating frontal zones. The key feature of both tests is that there is significant sensitivity to the model grid while converging (structurally) at high resolution. Both test cases are investigated for a series of uniform resolutions and a variety of AMR tagging criteria. The AMR simulations demonstrate that grid refinement can resolve local features without requiring global high-resolution meshes. However, the results are sensitive to the refinement criteria. Criteria that trigger refinement early in a simulation reproduce the uniform-resolution reference solutions most reliably. In contrast, AMR criteria that delay refinement for several days require careful tuning of the AMR thresholds to improve results compared with uniform-resolution simulations. © 2019 American Meteorological Society."
"55829903800;7005702722;","Quantifying the annular mode dynamics in an idealized atmosphere",2019,"10.1175/JAS-D-18-0268.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074985614&doi=10.1175%2fJAS-D-18-0268.1&partnerID=40&md5=c66dd92532589d0b7dda432a01451c5b","The linear response function (LRF) of an idealized GCM, the dry dynamical core with Held-Suarez physics, is used to accurately compute how eddy momentum and heat fluxes change in response to the zonal wind and temperature anomalies of the annular mode at the quasi-steady limit. Using these results and knowing the parameterizations of surface friction and thermal radiation in Held-Suarez physics, the contribution of each physical process (meridional and vertical eddy fluxes, surface friction, thermal radiation, and meridional advection) to the annular mode dynamics is quantified. Examining the quasigeostrophic potential vorticity balance, it is shown that the eddy feedback is positive and increases the persistence of the annular mode by a factor of more than 2. Furthermore, how eddy fluxes change in response to only the barotropic component of the annular mode, that is, vertically averaged zonal wind (and no temperature) anomaly, is also calculated similarly. The response of eddy fluxes to the barotropic-only component of the annular mode is found to be drastically different from the response to the full (i.e., barotropic 1 baroclinic) annular mode anomaly. In the former, the eddy generation is significantly suppressed, leading to a negative eddy feedback that decreases the persistence of the annular mode by nearly a factor of 3. These results suggest that the baroclinic component of the annular mode anomaly, that is, the increased low-level baroclinicity, is essential for the persistence of the annular mode, consistent with the baroclinic mechanism but not the barotropic mechanism proposed in the previous studies. © 2019 American Meteorological Society."
"57189986903;55598938800;55885662200;6504572295;7003501766;","The impact of precipitation evaporation on the atmospheric aerosol distribution in EC-Earth v3.2.0",2018,"10.5194/gmd-11-1443-2018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85045583984&doi=10.5194%2fgmd-11-1443-2018&partnerID=40&md5=d1db562e89b6870692a63fa473219d6f","The representation of aerosol-cloud interaction in global climate models (GCMs) remains a large source of uncertainty in climate projections. Due to its complexity, precipitation evaporation is either ignored or taken into account in a simplified manner in GCMs. This research explores various ways to treat aerosol resuspension and determines the possible impact of precipitation evaporation and subsequent aerosol resuspension on global aerosol burdens and distribution. The representation of aerosol wet deposition by large-scale precipitation in the EC-Earth model has been improved by utilising additional precipitation-related 3- D fields from the dynamical core, the Integrated Forecasting System (IFS) general circulation model, in the chemistry and aerosol module Tracer Model, version 5 (TM5). A simple approach of scaling aerosol release with evaporated precipitation fraction leads to an increase in the global aerosol burden (+7.8 to +15% for different aerosol species). However, when taking into account the different sizes and evaporation rate of raindrops following Gong et al. (2006), the release of aerosols is strongly reduced, and the total aerosol burden decreases by -3.0 to -8.5 %. Moreover, inclusion of cloud processing based on observations by Mitra et al. (1992) transforms scavenged small aerosol to coarse particles, which enhances removal by sedimentation and hence leads to a -10 to -11% lower aerosol burden. Finally, when these two effects are combined, the global aerosol burden decreases by -11 to -19 %. Compared to the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations, aerosol optical depth (AOD) is generally underestimated in most parts of the world in all configurations of the TM5 model and although the representation is now physically more realistic, global AOD shows no large improvements in spatial patterns. Similarly, the agreement of the vertical profile with Cloud- Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite measurements does not improve significantly. We show, however, that aerosol resuspension has a considerable impact on the modelled aerosol distribution and needs to be taken into account. © Author(s) 2018."
"43561261500;56006103500;36015299300;","Dynamical Core in Atmospheric Model Does Matter in the Simulation of Arctic Climate",2018,"10.1002/2018GL077478","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044401493&doi=10.1002%2f2018GL077478&partnerID=40&md5=6ef0eb5a16e708802b30ddc07e1fb420","Climate models using different dynamical cores can simulate significantly different winter Arctic climates even if equipped with virtually the same physics schemes. Current climate simulated by the global climate model using cubed-sphere grid with spectral element method (SE core) exhibited significantly warmer Arctic surface air temperature compared to that using latitude-longitude grid with finite volume method core. Compared to the finite volume method core, SE core simulated additional adiabatic warming in the Arctic lower atmosphere, and this was consistent with the eddy-forced secondary circulation. Downward longwave radiation further enhanced Arctic near-surface warming with a higher surface air temperature of about 1.9 K. Furthermore, in the atmospheric response to the reduced sea ice conditions with the same physical settings, only the SE core showed a robust cooling response over North America. We emphasize that special attention is needed in selecting the dynamical core of climate models in the simulation of the Arctic climate and associated teleconnection patterns. ©2018. American Geophysical Union. All Rights Reserved."
"54879515900;57192157322;","An approach to secure weather and climate models against hardware faults",2017,"10.1002/2016MS000816","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013478425&doi=10.1002%2f2016MS000816&partnerID=40&md5=212a1e337e3ee0c860520bd343d58b2a","Enabling Earth System models to run efficiently on future supercomputers is a serious challenge for model development. Many publications study efficient parallelization to allow better scaling of performance on an increasing number of computing cores. However, one of the most alarming threats for weather and climate predictions on future high performance computing architectures is widely ignored: the presence of hardware faults that will frequently hit large applications as we approach exascale supercomputing. Changes in the structure of weather and climate models that would allow them to be resilient against hardware faults are hardly discussed in the model development community. In this paper, we present an approach to secure the dynamical core of weather and climate models against hardware faults using a backup system that stores coarse resolution copies of prognostic variables. Frequent checks of the model fields on the backup grid allow the detection of severe hardware faults, and prognostic variables that are changed by hardware faults on the model grid can be restored from the backup grid to continue model simulations with no significant delay. To justify the approach, we perform model simulations with a C-grid shallow water model in the presence of frequent hardware faults. As long as the backup system is used, simulations do not crash and a high level of model quality can be maintained. The overhead due to the backup system is reasonable and additional storage requirements are small. Runtime is increased by only 13 % for the shallow water model. © 2017. The Authors."
"55802056700;15765007300;","The impact of GCM dynamical cores on idealized sudden stratospheric warmings and their QBO interactions",2016,"10.1175/JAS-D-15-0242.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84988346519&doi=10.1175%2fJAS-D-15-0242.1&partnerID=40&md5=8f0fd2213fd8b50744d151266c75856c","The paper demonstrates that sudden stratospheric warmings (SSWs) can be simulated in an ensemble of dry dynamical cores that miss the typical SSW forcing mechanisms like moist processes, land-sea contrasts, or topography. These idealized general circulation model (GCM) simulations are driven by a simple Held-Suarez-Williamson (HSW) temperature relaxation and low-level Rayleigh friction. In particular, the four dynamical cores of NCAR's Community Atmosphere Model, version 5 (CAM5), are used, which are the semi-Lagrangian (SLD) and Eulerian (EUL) spectral-transform models and the finite-volume (FV) and the spectral element (SE) models. Three research themes are discussed. First, it is shown that SSW events in such idealized simulations have very realistic flow characteristics that are analyzed via the SLD model. A single vortex-split event is highlighted that is driven by wavenumber-1 and -2 wave-mean flow interactions. Second, the SLD simulations are compared to the EUL, FV, and SE dynamical cores, which sheds light on the impact of the numerical schemes on the circulation. Only SLD produces major SSWs, while others only exhibit minor stratospheric warmings. These differences are caused by SLD's more vigorous wave-mean flow interactions in addition to a warm pole bias, which leads to relatively weak polar jets in SLD. Third, it is shown that tropical quasi-biennial oscillation (QBO)-like oscillations and SSWs can coexist in such idealized HSW simulations. They are present in the SLD dynamical core that is used to analyze the QBO-SSW interactions via a transformed Eulerian-mean (TEM) analysis. The TEM results provide support for the Holton-Tan effect. © 2016 American Meteorological Society."
"7202192265;55973531200;16043815300;57190426088;","A high-order multiscale global atmospheric model",2016,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84979935485&partnerID=40&md5=0e524e46f71dfbda9ac6080afbfdc79a","The High-Order Method Modeling Environment (HOMME), developed at NCAR, is a petascale hydrostatic framework, which employs the cubed-sphere grid system and high- order continuous or discontinuous Galerkin (DG) methods. Recently, the HOMME frame- work is being extended to a non-hydrostatic dynamical core, named as the High-Order Multiscale Atmospheric Model (HOMAM). The spatial discretization is based on DG or high-order finite-volume methods. Orography is handled by the terrain-following height- based coordinate system. To alleviate the stringent CFL stability requirement resulting from the vertical aspects of the dynamics, an operator-splitting time integration scheme based on the horizontally explicit and vertically implicit (HEVI) philosophy is adopted for HOMAM. Preliminary results with the benchmark test cases proposed in the Dynamical Core Model Intercomparison project (DCMIP) test-suite are encouraging. © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA."
"55187262300;55612096100;56918729900;57001642200;55729544100;57211219633;","A dynamical-statistical forecasting model of the western pacific subtropical high area index based on an improved self-memorization principle",2015,"10.1175/MWR-D-15-0181.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949742488&doi=10.1175%2fMWR-D-15-0181.1&partnerID=40&md5=63454b3cdd736fdbbc79d650d7d3b5d8","A new dynamical-statistical forecasting model of the western Pacific subtropical high (WPSH) area index (AI) was developed, based on dynamical model reconstruction and improved self-memorization, in order to address the inaccuracy of long-term WPSH forecasts. To overcome the problem of single initial prediction values, the self-memorization function was introduced to improve the traditional reconstruction model, thereby making it more effective for describing chaotic systems, such as WPSH. Processing actual data, the reconstruction equation was used as a dynamical core to overcome the problem of employing a simple core. The resulting dynamical-statistical forecasting model for AI was used to predict the strength of long-term WPSH forecasting. Based on 17 experiments with the WPSH during normal and abnormal years, forecast results for a period of 25 days were found to be good, with a correlation coefficient of ;0.80 and a mean absolute percentage error of ,8%, showing that the improved model produced satisfactory long-term forecasting results. Additional experiments for predicting the ridgeline index (RI) and the west ridge-point index (WI) were also performed to demonstrate that the developed model was effective for the complete prediction of the WPSH. Compared with the authors' previous models and other established models of reasonable complexity, the current model shows better long-term WPSH forecasting ability than do other models, meaning that the aberrations of the subtropical high could be defined and forecast by the model. © 2015 American Meteorological Society."
"56227383700;16309282700;56225695300;","Development of a tangent linear model (version 1.0) for the High-Order Method Modeling Environment dynamical core",2014,"10.5194/gmd-7-1175-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84903134494&doi=10.5194%2fgmd-7-1175-2014&partnerID=40&md5=38f4644831e77f308c9c828367d80859","We describe development and validation of a tangent linear model for the High-Order Method Modeling Environment, the default dynamical core in the Community Atmosphere Model and the Community Earth System Model that solves a primitive hydrostatic equation using a spectral element method. A tangent linear model is primarily intended to approximate the evolution of perturbations generated by a nonlinear model, provides a computationally efficient way to calculate a nonlinear model trajectory for a short time range, and serves as an intermediate step to write and test adjoint models, as the forward model in the incremental approach to four-dimensional variational data assimilation, and as a tool for stability analysis. Each module in the tangent linear model (version 1.0) is linearized by hands-on derivations, and is validated by the Taylor-Lagrange formula. The linearity checks confirm all modules correctly developed, and the field results of the tangent linear modules converge to the difference field of two nonlinear modules as the magnitude of the initial perturbation is sequentially reduced. Also, experiments for stable integration of the tangent linear model (version 1.0) show that the linear model is also suitable with an extended time step size compared to the time step of the nonlinear model without reducing spatial resolution, or increasing further computational cost. Although the scope of the current implementation leaves room for a set of natural extensions, the results and diagnostic tools presented here should provide guidance for further development of the next generation of the tangent linear model, the corresponding adjoint model, and four-dimensional variational data assimilation, with respect to resolution changes and improvements in linearized physics and dynamics. © Author(s) 2014."
"57212000962;57212003533;57212001530;","Analysis of Pseudomomentum Wave-Activity Density in a Heavy Rainfall Event in East China",2014,"10.3878/j.issn.1674-2834.13.0055","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85068131071&doi=10.3878%2fj.issn.1674-2834.13.0055&partnerID=40&md5=9e05b18709cfced7a0bc1cc13b5f2364","Taking into account moisture in virtue of general potential temperature, the author derive a three-dimensional (3D) pseudomomentum wave-activity relation for the moist atmosphere from the primitive equations in Cartesian coordinates using the Momentum-Casimir method. Since the wave-activity relation is constructed in an ageostrophic and non-hydrostatic dynamical framework, it may be applicable to diagnosing the evolution and propagation of mesoscale systems leading to heavy rainfall. The theoretical analysis shows that, besides the local change of wave-activity flux divergence and source or sink, the wave-activity relation includes two additional forcing terms. The first is the zonal gradient of difference between general potential temperature and potential temperature perturbations, and the second is the covariance of the solenoid and gradient of water vapor, denoting the direct influence of moisture on wave-activity density. The wave-activity density was applied to a heavy precipitation event occurring in the Jianghuai region of China. The calculation showed that the wave-activity density was consistent with 6-h accumulated precipitation observations, in terms of both spatial distribution and temporal tendency. This suggested that the disturbance represented by wave-activity density was closely related to the heavy precipitation. Although the wave-activity flux divergence and the covariance of the solenoid and gradient of water vapor made the primary contribution to the local change of wave-activity density, the covariance was more remarkable. The zonal gradient of difference between general potential temperature and potential temperature perturbations made a weaker contribution to the wave-activity density. © 2014, © Institute of Atmospheric Physics, Chinese Academy of Sciences."
"55265710100;32867786300;","Isentropic primitive equations for the moist troposphere",2014,"10.1002/qj.2312","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922891016&doi=10.1002%2fqj.2312&partnerID=40&md5=0bddeb3af80f6d60b6f435387b342229","Despite the knowledge that the potential temperature of an air parcel has a dependence on its water vapour content, potential temperature is often still calculated as if the parcel were dry, assuming that this moisture dependence is negligible. We show that such a dry potential temperature approximation is not suitable for tropical regions. Moisture gradient terms are seen in the isentropic primitive equations when Exner and Montgomery functions are generalised with moist specific heat capacities, forming a contribution to the horizontal momentum tendency comparable to that by the Montgomery function. This reflects how local horizontal gradients in potential temperature created by inhomogeneous water vapour distribution are relatively significant compared to gradients created by inhomogeneous temperature, in a large-scale background of weak horizontal temperature gradient. In such an environment, water plays an active role in tropical atmospheric dynamics without the uptake or release of latent heat during phase changes. Hence, we suggest that the tropical troposphere is a place where the atmosphere can behave dynamically as a binary-component fluid at local and regional scales. © 2013 Royal Meteorological Society."
"7006432091;","Atmospheric dynamics",2014,"10.1016/B978-0-12-374266-7.00002-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904015657&doi=10.1016%2fB978-0-12-374266-7.00002-0&partnerID=40&md5=43e61551b82a099963dd0f62165cf31e","This chapter reviews the basic dynamic, thermodynamic, and water-continuity relationships required to read the literature on cloud dynamics. The force balances and instabilities that affect clouds are reviewed. The primitive equations are presented and their Boussinesq and anelastic forms are presented. Horizontal and vertical vorticity equations are presented. Absolute and potential vorticity are discussed. Linearization, perturbation forms of the equations, eddy fluxes, and turbulence terms are discussed. The Ekman layer is defined and discussed. The basics of hydrostatic, geostrophic, semigeostrophic, cyclostrophic, and gradient-wind balance are described. Thermal wind for both geostrophic and gradient-wind conditions is presented. Angular momentum is discussed. Buoyancy, conditional instability, inertial instability, potential instability, symmetric instability, and Kelvin-Helmholtz instability are defined and discussed. Gravity waves and geostrophic and gradient-wind adjustment are reviewed. © 2014 Elsevier Inc."
"16038583700;","An application of sequential variational method without tangent linear and adjoint model integrations",2013,"10.1175/MWR-D-11-00012.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84874871627&doi=10.1175%2fMWR-D-11-00012.1&partnerID=40&md5=dd06756bf14f24e74909e948562b6075","The sequential variational (SVAR)method minimizes the weakly constrained four-dimensional cost function by splitting it into a set of smaller cost functions. This study shows howit is possible to applySVARin practice by reducing the computational effort required by the algorithm. A major finding of the study is that, instead of using tangent linear and adjoint models, it is possible to estimate the largest eigenvalues and the corresponding eigenvectors of the evolution of the background error covariances only by applying successive nonlinear model integrations. Anothermajor finding is that the impact of future observations on previous state estimatesmay be obtained in an accurate and numerically stable way by using suitably defined cost functions and control space transformations without any additional model integrations. The new method is applied in a realistic data assimilation experiment with a primitive equations ocean model. © 2013 American Meteorological Society."
"55715268900;36077992900;48361451800;","Global response to tropical diabatic heating variability in boreal winter",2012,"10.1007/s00376-011-1049-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863180975&doi=10.1007%2fs00376-011-1049-9&partnerID=40&md5=5e668e24934a9f63970fce980aa90812","Global teleconnections associated with tropical convective activities were investigated, based on monthly data of 29 Northern Hemisphere winters: December, January, February, and March (DJFM). First, EOF analyses were performed on the outgoing long-wave radiation (OLR) data to characterize the convective activity variability in the tropical Indian Ocean and the western Pacific. The first EOF mode of the convective activity was highly correlated with the ENSO. The second EOF mode had an east-west dipole structure, and the third EOF mode had three convective activity centers. Two distinct teleconnection patterns were identified that were associated, respectively, with the second and third EOF modes. A global primitive equation model was used to investigate the physical mechanism that causes the global circulation anomalies. The model responses to anomalous tropical thermal forcings that mimic the EOF patterns matched the general features of the observed circulation anomalies well, and they were mainly controlled by linear processes. The importance of convective activities in the tropical Indian Ocean and western Pacific to the extended and long-range forecasting capability in the extratropics is discussed. © 2012 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg."
"8080847900;55928817500;26531118000;6603439625;7006005916;7003936713;55293073600;37007098900;","The NMMB/BSC-CTM: A multiscale online chemical weather prediction system",2011,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84905351515&partnerID=40&md5=7e495ecaeb9adf3c44133844a9c3d4d4","The model NMMB/BSC-CTM is a new fully on-line chemical weather prediction system under development at the Earth Sciences Department of the Barcelona Supercomputing Center in collaboration with several research institutions. The basis of the development is the NCEP new global/regional Nonhydrostatic Multiscale Model on the B grid (NMMB). Its unified nonhydrostatic dynamical core allows regional and global simulations and forecasts. A mineral dust module has been coupled within the NMMB. The new system, NMMB/BSCDUST, simulates the atmospheric life cycle of the eroded desert dust. The main characteristics are its on-line coupling of the dust scheme with the meteorological driver, the wide range of applications from meso to global scales, and the dust shortwave and longwave radiative feedbacks on meteorology. In order to complement such development, the BSC works also in the implementation of a fully on-line gas-phase chemical mechanism. Chemical species are advected and mixed at the corresponding time steps of the meteorological tracers using the same numerical scheme of the NMMB. Advection is Eulerian, positive definite and monotone. The final objective of the work is to develop a fully chemical weather prediction system, namely NMMB/BSC-CTM, able to resolve gas-aerosol-meteorology interactions from global to local scales. Future efforts will be oriented to incorporate a multi-component aerosol module within the system with the aim to solve the life-cycle of relevant aerosols at global scale (dust, sea salt, sulfate, black carbon and organic carbon). In the present contribution we describe the status of development of the system and first evaluation results of the gas-phase chemistry."
"7101807288;35301118900;6506610507;56170018500;8605365200;35300921900;7405450855;57218242071;35298413500;","A method of upgrading a hydrostatic model to a nonhydrostatic model",2009,"10.3319/TAO.2008.09.24.01(A)","https://www.scopus.com/inward/record.uri?eid=2-s2.0-72149094337&doi=10.3319%2fTAO.2008.09.24.01%28A%29&partnerID=40&md5=c2671013a5e318bc5b5591dd5e5e4735","As the sigma-p coordinate under hydrostatic approximation can be interpreted as the mass coordinate without the hydrostatic approximation, we propose a method that upgrades a hydrostatic model to a nonhydrostatic model with relatively less effort. The method adds to the primitive equations the extra terms omitted by the hydrostatic approximation and two prognostic equations for vertical speed w and nonhydrostatic part pressure p'. With properly formulated governing equations, at each time step, the dynamic part of the model is first integrated as that for the original hydrostatic model and then nonhydrostatic contributions are added as corrections to the hydrostatic solutions. In applying physical parameterizations after the dynamic part integration, all physics packages of the original hydrostatic model can be directly used in the nonhydrostatic model, since the upgraded nonhydrostatic model shares the same vertical coordinates with the original hydrostatic model. In this way, the majority codes of the nonhydrostatic model come from the original hydrostatic model. The extra codes are only needed for the calculation additional to the primitive equations. In order to handle sound waves, we use smaller time steps in the nonhydrostatic part dynamic time integration with a split-explicit scheme for horizontal momentum and temperature and a semi-implicit scheme for w and p'. Simulations of 2-dimensional mountain waves and density flows associated with a cold bubble have been used to test the method. The idealized case tests demonstrate that the proposed method realistically simulates the nonhydrostatic effects on different atmospheric circulations that are revealed in theoretical solutions and simulations from other nonhydrostatic models. This method can be used in upgrading any global or mesoscale models from a hydrostatic to nonhydrostatic model."
"6505569858;16241942600;6508060859;7003930724;7004109472;","Process-oriented statistical-dynamical evaluation of LM precipitation forecasts",2008,"10.5194/adgeo-16-33-2008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-42149093245&doi=10.5194%2fadgeo-16-33-2008&partnerID=40&md5=d06a0e54ffb2eb29b6dc9687f4c55152","The objective of this study is the scale dependent evaluation of precipitation forecasts of the Lokal-Modell (LM) from the German Weather Service in relation to dynamical and cloud parameters. For this purpose the newly designed Dynamic State Index (DSI) is correlated with clouds and precipitation. The DSI quantitatively describes the deviation and relative distance from a stationary and adiabatic solution of the primitive equations. A case study and statistical analysis of clouds and precipitation demonstrates the availability of the DSI as a dynamical threshold parameter. This confirms the importance of imbalances of the atmospheric flow field, which dynamically induce the generation of rainfall."
"7004014731;6507866629;7103342287;","Global Kelvin waves in the upper atmosphere excited by tropospheric forcing at midlatitudes",2007,"10.1029/2006JD007235","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249745058&doi=10.1029%2f2006JD007235&partnerID=40&md5=b9b1240b463f651da42b35a82e432a32","Nonlinear integrations with a 3-D primitive equation model of the middle and upper atmosphere reveal global-scale Kelvin waves. Owing to their meridional extent, these eastward propagating disturbances can be excited by tropospheric fluctuations over much of the globe. Stochastic forcing in the midlatitude troposphere produces an eastward response that involves the Kelvin normal mode, with barotropic vertical structure, as well as a continuum of vertically propagating Kelvin waves. Having periods of order a day and shorter, those disturbances are all global. Transient fluctuations representative of midlatitude weather systems reproduce observed Kelvin structure and amplitude near the tropopause. Vertical amplification then leads to wind fluctuations at mesospheric and thermospheric altitudes of 5-15 m/s. Approaching tidal amplitudes, global Kelvin waves should therefore represent a measurable if not prominent feature at those altitude. Copyright 2007 by the American Geophysical Union."
"7401699378;56098717400;","A tropical storm: Self-organization and complexity",2007,"10.1029/2006GL028612","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249891901&doi=10.1029%2f2006GL028612&partnerID=40&md5=1e60c18f7b8464ca3c60d085adad074a","This paper is aimed at investigating the interaction between a tropical storm (TS) and its adjacent mesoscale convective vortices (MCVs) using a barotropic primitive equation model. The results show that the interaction may result in vortex self-organization. Compared with the case without MCVs, the quasi-final state vortex becomes stronger with the increased kinetic energy and lower value of height at the vortex centre owing to the extra vorticity supplied by the MCVs. The intensity of the initial TS controls the complexity of the self-organization process and determines whether the vorticity of MCVs is either fully or partially absorbed. The quasi-final state vortex will either keep the intensity the initial TS has or decay dependently on the intensity or number of the MCVs, exhibiting the complexity of the characteristics of the organized quasi-final state vortex. Copyright 2007 by the American Geophysical Union."
"55427274600;7003329743;24783722000;7003710826;","Monitoring atmospheric gravity waves by means of SAR, MODIS imagery and high-resolution ETA atmospheric model: A case study",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749187452&partnerID=40&md5=ac21e1a528e117d089266e1b88e4fe65","A study aimed at retrieving sea surface wind fields of semi-enclosed basins from combined use of SAR imagery and a high resolution mesoscale numerical atmospheric model, is presented. Two consecutive ERS-2 SAR frames and a set of NOAA/AVHRR and MODIS images acquired over the North Tyrrhenian Sea on March 30, 2000 were used for the analysis. SAR wind speeds and directions at 10 m above the sea surface were retrieved using the semi-empirical backscatter model CMOD4. Surface wind vectors predicted by the meteorological ETA model were exploited as guess input to SAR wind inversion procedure. ETA is a three-dimensional, primitive equation, grid-point model currently operational at the National Centers for Environmental Prediction of the U.S. National Weather Service. The model was adapted to run with a resolution up to about 4.0 Km. It was found that the inversion methodology was not able to resolve wind speed modulations due to the action of an atmospheric gravity wave, called ""lee wave"", which occurred in the analyzed area. A simple atmospheric wave propagation model was thus used to account for the SAR observed surface wind speed modulation. Synergy with ETA model outputs was further exploited in simulations where atmospheric parameters up-wind the atmospheric wave were provided as input to the lee wave propagation model."
"7202055345;6507982342;","Energy conservation for a general vertical coordinate - a reexamination of unsimplified forms",1999,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032945826&partnerID=40&md5=327883d4abc3f2443b1ec23f5caa0be0","Based on a previous reexamination of virtually unsimplified dynamical equations for a general (monotone) vertical coordinate, a systematic approach to energy-consistent omission of terms in dynamical modelling is presented. Unsimplified expressions are given for the rate of change of (integrated) total energy, as well as the Gauss divergence theorem with the upper and lower boundary conditions, all for a general vertical coordinate. Individual components of the energy rate of change are evaluated with the aid of the unsimplified basic dynamical equations with the simplest physics (dry, adiabatic and frictionless), and for various formulations of these equations the integrated expression is shown to vanish, thus confirming energy conservation. Different forms of the thermodynamic equation are used, and the horizontal equation of motion is used in undifferentiated and differentiated forms, with a discussion of consistency problems. The procedure highlights the identification of groupings of terms that vanish together, either by direct cancellation or by integration and application of the boundary conditions. Labelling of terms facilitates the identification of such linkages. A main outcome of the study is a series of lists of labels reflecting linkages between terms, meaning that linked terms have to be omitted or retained together for energy consistency. Naturally these lists vary with the forms of the equations chosen in the derivation of energy conservation, and significantly the identification of linkages and conversion terms is not unique. Graphical representation of the lists assists in characterising the differences between them. The methodology can aid in designing energy consistent model equations through the omission of terms, or in investigating the energy properties of already simplified sets of model equations. It paves the way on the one hand for confirming and possibly extending the range of filtered and balanced models, and on the other hand, in the light of the growing interest in nonhydrostatic forms in numerical weather prediction, for a reexamination of the approximations traditionally made in arriving at the primitive equations."
"36830895200;","The formulation of fidelity schemes of physical conservation laws and improvements on a traditional spectral model of baroclinic primitive equations for numerical prediction",1999,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032766761&partnerID=40&md5=79e88e7a294e0a508d84fd76250cc71a","In this paper, two formulation theorems of time-difference fidelity schemes for general quadratic and cubic physical conservation laws are respectively constructed and proved, with earlier major conserving time-discretized schemes given as special cases. These two theorems can provide new mathematical basis for solving basic formulation problems of more types of conservative time-discrete fidelity schemes, and even for formulating conservative temporal-spatial discrete fidelity schemes by combining existing instantly conserving space-discretized schemes. Besides, the two theorems can also solve two large categories of problems about linear and nonlinear computational instability. The traditional global spectral-vertical finite-difference semi-implicit model for baroclinic primitive equations is currently used in many countries in the world for operational weather forecast and numerical simulations of general circulation. The present work, however, based on Theorem 2 formulated in this paper, develops and realizes a high-order total energy conserving semi-implicit time-difference fidelity scheme for global spectral-vertical finite-difference model of baroclinic primitive equations. Prior to this, such a basic formulation problem remains unsolved for long, whether in terms of theory or practice. The total energy conserving semi-implicit scheme formulated here is applicable to real data long-term numerical integration. The experiment of thirteen FGGE data 30-day numerical integration indicates that the new type of total energy conserving semi-implicit fidelity scheme can surely modify the systematic deviation of energy and mass conserving of the traditional scheme. It should be particularly noted that, under the experiment conditions of the present work, the systematic errors induced by the violation of physical laws of conservation in the time-discretized process regarding the traditional scheme designs (called type Z errors for short) can contribute up to one-third of the total systematic root-mean-square (RMS) error at the end of second week of the integration and exceed one half of the total amount four weeks afterwards. In contrast, by realizing a total energy conserving semi-implicit fidelity scheme and thereby eliminating corresponding type Z errors, roughly an average of one-fourth of the RMS errors in the traditional forecast cases can be reduced at the end of second week of the integration, and averagely more than one-third reduced at integral time of four weeks afterwards. In addition, experiment results also reveal that, in a sense, the effects of type Z errors are no less great than that of the real topographic forcing of the model. The prospects of the new type of total energy conserving fidelity schemes are very encouraging."
"6506510748;6603734346;","The instability of upper tropospheric shear lines",1998,"10.1016/S1352-2310(98)00103-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032169466&doi=10.1016%2fS1352-2310%2898%2900103-4&partnerID=40&md5=aeb2fac0a237150698d7d71f7fcfc070","Shear lines in the upper troposphere are created when strips of cold polar air are advected into midlatitudes. The subsequent dynamical evolution has potentially significant impact on the mixing of stratospheric and tropospheric air. The instability of idealized shear lines with varying Rossby numbers are studied with a primitive equation model. The results are compared with earlier quasigeostrophic solutions. There is good agreement in the range of Rossby numbers investigated (up to 1.5).Shear lines in the upper troposphere are created when strips of cold polar air are advected into midlatitudes. The subsequent dynamical evolution has potentially significant impact on the mixing of stratospheric and tropospheric air. The instability of idealized shear lines with varying Rossby numbers are studied with a primitive equation model. The results are compared with earlier quasigeostrophic solutions. There is good agreement in the range of Rossby numbers investigated (up to 1.5)."
"7202026750;7402639527;","Design of a three-dimensional global adiabatic spectral primitive equation model",1997,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031395802&partnerID=40&md5=3596d81b138c1218f39f3f6daf89b585","A three-dimensional (3D) global adiabatic spectral primitive equation model has been designed. The main features are as follows. (1) Adoption of spherical harmonics and Tschebyscheff polynomials as the basis functions in the horizontal and vertical respectively, but the unknowns in the spectral equations are two-dimensional; (2) Inclusion of the tropopause, which may vary with time and space; (3) Suggestion of a spectral method for representing the vertical structure of the atmosphere applicable to the unsmoothed profile case: (4) In consideration of nonlinear vertical aliasing a technique is proposed to avoid it and nonlinear computational instability. Based on real data forecasts up to 48 hours have been performed. The results show that the statistical verifications with the model are superior on the average to those with the T42L9 used operationally before 1995 at NMC of China at the same mean resolution."
"7004247643;6603432771;","Using the adjoint method with the ocean component of coupled ocean-atmosphere models",1997,"10.2151/jmsj1965.75.1B_463","https://www.scopus.com/inward/record.uri?eid=2-s2.0-22444455075&doi=10.2151%2fjmsj1965.75.1B_463&partnerID=40&md5=aed524db6a5344730ed4933d9f77e683","A Primitive Equation Ocean General Circulation Model (PE OGCM) in a global configuration similar to that used in coupled ocean-atmosphere models is fitted to climatological data using the adjoint method. The ultimate objective is the use of data assimilation for the improvement of the ocean component of coupled models, and for the calculation of initial conditions for initializing coupled model integrations. We argue that ocean models that are used for coupled climate studies are an especially appropriate target for data assimilation using the adjoint method. © 1997, Meteorological Society of Japan."
"7201653018;7201483914;7006069664;6701636478;","The role of radiative transfer in maintaining the Indian summer monsoon circulation",1997,"10.1007/s000240050043","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0031285295&doi=10.1007%2fs000240050043&partnerID=40&md5=4b03f3aa50bc3ca6007d84d5292cd6ab","The radiative-convective feedback and land-sea thermal forcing play significant roles in maintenance of the summer monsoon circulation over the Indian sub-continent. In this study, the role of radiative transfer in maintaining the monsoon circulation is examined with numerical sensitivity experiments. For this purpose, a sixteen layer primitive equation limited area model is used to perform numerical simulations with and without atmospheric radiative transfer processes parameterized in the model. The initial values and boundary conditions for the numerical integrations of the model are derived from operational analyses of the ECMWF, UK. The results show that the radiative transfer is essential in maintaining the intensity of the low level Somali Jet as well as the upper level Tropical Easterly Jet (TEJ) over the Indian sub-continent and adjoining seas. The meridional circulation over the region is also well simulated. As a result, enough moisture transports from the warm equatorial region to simulate more realistic orographic precipitation in the windward side of the mountains along the West coast of India. Without radiative transfer processes in the model atmosphere the simulated monsoon circulation weakens, moisture transport decreases and the precipitation lessens."
"6603432771;7004247643;7005960075;","Combining data and a global primitive equation ocean general circulation model using the adjoint method",1996,"10.1016/S0422-9894(96)80008-0","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956732949&doi=10.1016%2fS0422-9894%2896%2980008-0&partnerID=40&md5=a8c01c0ae9442249af77acb3546aaef8","A Primitive Equation Ocean General Circulation Model (PE OGCM) in a global configuration similar to that used in coupled ocean-atmosphere models is fitted to climatological data using the adjoint method. The ultimate objective is the use of data assimilation for the improvement of the ocean component of coupled models, and for the calculation of initial conditions for initializing coupled model integrations. It is argued that oceanic models that are used for coupled climate studies are an especially appropriate target for data assimilation using the adjoint method. It is demonstrated that a successful assimilating of data into a fully complex PE OGCM critically depends on a very careful choice of the surface boundary condition formulation, on the optimization problem formulation, and on the initial guess for the optimization solution. The use of restoring rather than fixed surface-flux boundary conditions for the temperature seems to result in significantly improved model results as compared with previous studies using fixed surface-flux boundary conditions. The convergence of the optimization seems very sensitive to the cost formulation in a PE model, and a successful cost formulation is discussed and demonstrated. Finally, the use of simple, suboptimal, assimilation schemes for obtaining an initial guess for the adjoint optimization is advocated and demonstrated. © 1996 Elsevier B.V. All rights reserved."
"55740245100;55464843300;57211223914;","Time spectral analysis for the natural variability of the barotropic model atmosphere with annual cycle forcing",1996,"10.2151/jmsj1965.74.6_909","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0040455237&doi=10.2151%2fjmsj1965.74.6_909&partnerID=40&md5=4ac82497e66646229ca74d6d5b173693","In this study, a long-term (1000 years) integration of a simple barotropic primitive equation model was carried out to investigate the typical magnitude and spectral features of natural variability of the model atmosphere. The first experiment without an annual-cycle forcing shows no noticeable ultra-low-frequency variability. The frequency spectrum of the model atmosphere is characterized as a white noise for the low-frequency range beyond the period about 50 days. The spectrum then shifts sharply to a red noise for the period shorter than 50 days, indicating a characteristic -3 power slope over the frequency domain. Although no noticeable spectral peak is detected, we can find intraseasonal variability with a period of about 50 days in the time series of the model atmosphere as a result from the sharp transition from the red to white noise. Since the sole energy source of the system is a parameterized baroclinic instability of frequency about (5-day)-1, we must have a reverse energy cascade from higher-to lower-frequency ranges along the -3 power slope of the red noise spectrum. It is discussed in this study that the spectrum tends to be red over the high-frequency range beyond (50-day)-1 where a linear relation holds between life-time and spatial scales for prominent atmospheric phenomena. Beyond this period, the internal non-linear dynamics of the primitive equation can not sustain large energy because the spatial scale of the Earth is finite. As a result, the very-low-frequency variability results in the white noise spectrum. Next, the same simple model is integrated with an annual-cycle forcing for 100 years to investigate the excitation of harmonics and subharmonics expected by the non-linear dynamic modulation of the annual-cycle forcing. The results show, however, that the spectral features are not altered by the inclusion of the annual cycle, except for the isolated spectral peak associated with the annual-cycle forcing. We suggest from the results of this study that the harmonics and subharmonics, such as semiannual and biennial oscillations, are not excited solely by the non-linear dynamic modulation of the forced annual cycle in the atmosphere."
"35477562700;","The linear response of a slowly-rotating atmosphere to mobile heating",1995,"10.2151/jmsj1965.73.6_1181","https://www.scopus.com/inward/record.uri?eid=2-s2.0-21344468351&doi=10.2151%2fjmsj1965.73.6_1181&partnerID=40&md5=35a534559a73150a265e5c691cfd6a77","The three-dimensional response of a slowly-rotating atmosphere to mobile heating is investigated byusing linearized primitive equations. The primitive equations are separated into the horizontal and vertical structure equations. The Hough functions are used in the numerical treatment of the horizontal equations.The velocity of planetary rotation and that of solar heating are fixed at the values for Venus. The responses are obtained for various values of the atmospheric stability and damping rate. For the largedamping rate, a direct circulation between the day and night sides is obtained, while for small damping rates the zonal winds predominate and the geostrophic relation is established in the extratropics. © 1995, Meteorological Society of Japan."
"7401804956;","Ocean modelling efforts in the global climate system",1994,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028684140&partnerID=40&md5=d796f8777831c5cb96171c933bfab550","In this paper I will try to give an overview of ocean models which have been used to explain and elucidate the role of the oceans in different frequency ranges of the climate variability spectrum. Modelling of such a diverse range of scales in space and time can only be performed today with restrictions in the spatial resolution or integration length. Because the deep ocean adjusts to different surface forcing characteristics on time-scales of millennia, an equilibrium cannot be reached with current computer resources. The importance of the mesoscale eddy field in the dynamical and thermodynamical balance of the Southern Ocean and its effect on property transports in this region has recently been the subject of much controversial discussion. Multi-level primitive equation modelling of the global ocean circulation in eddy-resolution is a major computational task which has just been started. -from Author"
"7004345429;","The birth of numerical weather prediction",1991,"10.1034/j.1600-0870.1991.t01-2-00006.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981633379&doi=10.1034%2fj.1600-0870.1991.t01-2-00006.x&partnerID=40&md5=cdaab6d641e1c8c924008df00444e69c","The paper describes the major events leading gradually to operational, numerical, short‐range predictions for the large‐scale atmospheric flow. The theoretical foundation starting with Rossby's studies of the linearized, barotropic equation and ending a decade and a half later with the general formulation of the quasi‐geostrophic, baroclinic model by Charney and Phillips is described. The problems connected with the very long waves and the inconsistences of the geostrophic approximation which were major obstacles in the first experimental forecasts are discussed. The resulting changes to divergent barotropic and baroclinic models and to the use of the balance equation are described. After the discussion of the theoretical foundation, the paper describes the major developments leading to the Meteorology Project at the Institute for Advanced Studied under the leadership of John von Neumann and Jule Charney followed by the establishment of the Joint Numerical Weather Prediction Unit in Suitland, Maryland. The interconnected developments in Europe, taking place more‐or‐less at the same time, are described by concentrating on the activities in Stockholm where the barotropic model was used in many experiments leading also to operational forecasts. The further developments resulting in the use of the primitive equations and the formulation of medium‐range forecasting models are not included in the paper. Copyright © 1991, Wiley Blackwell. All rights reserved"
"24785650500;24785047800;","The impact of soil moisture availability upon the partition of net radiation into sensible and latent heat fluxes",1991,"10.1007/BF02919616","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84875014301&doi=10.1007%2fBF02919616&partnerID=40&md5=0be5bd614584cdf11ae3750cee5647e9","The impact of soil moisture availability on the Bowen ratio and on the partition of net radiation flux into sensible, latent and soil heat fluxes was investigated by using one-dimensional primitive equations with a refined soil parameterization scheme. Simulation results presented that as soil moisture availability increases, the Bowen ratio and the partition of net radiation flux into sensible and soil heat fluxes decrease. The partition of net radiation flux in to latent heat flux, however, increases. Quantitative relationships between Bowen ratio and the partitions with soil moisture availability were also given in this study. © 1990, Advances in Atmospheric Sciences. All rights reserved."
"24368716700;7003427380;","Sensitivity and realism of wind-driven tropical ocean models",1990,"10.1016/0924-7963(90)90170-F","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025584884&doi=10.1016%2f0924-7963%2890%2990170-F&partnerID=40&md5=220d28fa7970fb39f5abdcc42923dcdc","The degree of realism of several equatorial ocean models is investigated by comparing modeled and observed mean seasonal cycles in the tropical Atlantic for two variables that play a role in sea surface temperature dynamics: 0/400 db dynamic height and surface current. The model-reality intercomparisons are made using a multivariate statistical testing procedure that takes into account the uncertainties of the atmospheric and oceanic data. In particular, the uncertainties in the model response due to random errors in the wind forcing and its interannual variability are considered and the uncertainty in the bulk formulation for the wind stress is represented. Two simplified equatorial ocean models are considered: the linear multimode model of Cane (1984) and the two-layer primitive equation model of Andrich (1989). Some results are also given for the general circulation model of Philander and Pacanowski (1986), although the effect of forcing uncertainties could not be taken into account. It is found that the errors that were considered are unable to explain the large discrepancies between model simulations and observations. In general, models represent better the 0/400 db dynamic height than the surface currents and the seasonal variations than the yearly mean. There is no striking difference in the performance of the three models for the dynamic height, but the general circulation model is superior for the surface currents, in particular near the western boundary. Better parameter tuning should, however, improve the performances of the two-layer model. It is also found that the sensitivity to forcing uncertainties is very model-dependent. © 1990."
"24789217700;6701853567;7101825844;","The sensitivity of numerical simulation to orography specification in the low resolution spectral model-Part I: The effects of orography on the atmospheric general circulation",1987,"10.1007/BF02656657","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649147776&doi=10.1007%2fBF02656657&partnerID=40&md5=224368f4f04a206124b7dfc0e4d75a15","In order to identify the sensitivity of the numerical simulation to the orography specification in a low resolution spectral model, two sets of numerical experiments for full-mountain and no-mountain cases are performed. By comparing the results, it is possible to determine the eflects of mountains on the atmospheric general circulation. This is a global, spectral model incorporating the primitive equations sugmented by physical parameterization and mountains, with five equally-spaced sigma levels in the vertical ang a triangular truncation at wavenumber 10 in the horizontal. Analysis of results supports earlier work by demonstrating that the low resolution global spectral model is capable of simulating the major features of global general circulation and indicates that it is necessary to consider the effects of mouniains on stationary disturbances in the numerical simulation. The simulations show that topography plays an important role in intensifying heat sources for maintenance of disturbances. All the simulation tests indicate that orography has an important infiuence on the distribution of heat sources and sinks. It reflects that interaction and interrelation exist between the effects of orography and heat sources and the atmospheric circulhtion via the dynamical processes of atmosphere. This result confirms the view points proposed by Yeh and Zhu (1958), but differs from those by Kasahara and Washington (1971), Manabe and Terpstra (1974). © 1987 Advances in Atmospheric Sciences."
"7005256983;16470956100;7005291612;","Vertical structure of the wind field during the special observing period I of the global weather experiment",1986,"10.1007/BF01026171","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022854007&doi=10.1007%2fBF01026171&partnerID=40&md5=ce48ceec39c8f540779d9446372a33b0","The vertical structure of the global atmosphere is analyzed for selected periods of the Special Observing Period I (SOP-I) for the Global Weather Experiment (GWE). The analysis consists of projection of the streamfunction and velocity potential at 200 and 850 mb on spherical harmonics and of the wind and height fields on the normal modes of a linearized form of the primitive equations for a basic state at rest. The kinematic vertical structure is discussed in terms of correlation coefficients of the 200 mb and 850 mb winds and analysis of the internal and external normal modes of the primitive equations. The reliability of the results is checked by applying the same analysis methods to data sets obtained from three different institutions: Geophysical Fluid Dynamics Laboratory (GFDL), European Center for Medium Range Weather Forecasting (ECMWF), and Goddard Laboratory for the Atmospheres (GLA). It is found that, on a global basis, vertically reversing circulations are as important as the equivalent barotropic structures. For the vertically reversing components, the gravity and mixed Rossby-gravity modes have contributions of the same order of magnitude as those of the Rossby modes in tropical latitudes. © 1986 Springer-Verlag."
"7102543929;24789353800;","Numerical simulation of the generation of mesoscale convective systems in large-scale environment",1986,"10.1007/BF02678656","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51249175488&doi=10.1007%2fBF02678656&partnerID=40&md5=e4187584b9b45694848f829d69903cc5","The generation of mesoscale convective systems is simulated by a 7-level primitive equation model. The large-scale parts of observed data at 1200 Z June 11, 1983, which are obtained by low-pass filter, are used as the initial data. The results show that the generation of mesoscale convective systems can be simulated from fields of meteorological variables on the large-scale background. When the low-level southwest jet stream is very moist, mesoscale convective systems can develop ahead of the wind speed maximum in the warm sector of Jiang-Huai (Changjiang-Huaihe Rivers) cyclone, where the potential stability tends to remain negative. Furthermore, they are similar to the mesoscale convective complex (MCC), which appears frequently in the central part of the United States during the warm season (March to September), in dynamical and thermal structure, distribution of precipitation and the process of generation and development. © 1986 Advances in Atmospheric Sciences."
"57190531316;7801692389;7801647691;","Synoptic impacts of NOAA 6/TIROS N data on numerical circulation forecasts.",1986,"10.1029/JC091iC02p02249","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022829241&doi=10.1029%2fJC091iC02p02249&partnerID=40&md5=89f0d30b54f05512f29befda18ad769c","Profiles of retrieved satellite observed temperatures provided to the Israel Meteorological Service (IMS) by the National Environmental Satellite Data and Information Service were used to enhance the specification of atmospheric conditions during three winter periods. Introduction of the satellite data was via three alternative schemes, and the enhanced specifications were used to initialize 48-hour numerical forecasts with the IMS five-layer primitive equation model; control forecasts were run in parallel from initial conditions without the satellite data. The study selects one forecast from each period for which discernible impacts on forecast synoptic fields can be attributed to the different initializations. The first two case studies examine the results of only one assimilation scheme and the third relates to all three schemes. Verification of the prognostics show the positive impact of including satellite temperatures in the initialization, but there were also examples of negative impact. -Authors"
"24787735000;","Determination of the distance between two adjacent stations, the observational vertical increment and the observational time interval in optimum sense",1985,"10.1007/BF02677247","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649150223&doi=10.1007%2fBF02677247&partnerID=40&md5=effe93a41af9ad9739dbacaf96e70d20","Considering the observational error, the truncation error and the requirements of numerical weather prediction, three formulas for determining the distance between two adjacent stations d1, the observational vertical increment Δp1 and the observational time interval Δt1 in optimum sense, have been derived. Since they depend on the shortest wavelength concerned and the ratio of maximum observational error to wave amplitude, the results are quite different for different scale systems. For the filtered model the values of d1, Δp1, and Δt1 general come near those required in the MANUAL on the GOS published in 1980 by WMO. But for the primitive equation model the estimated value of Δt1 is much less than those required in the filtered model case. Therefore, it is improper to study the fast moving and developing processes of the atmospheric motion only on the basis of the conventional observations. It seems to be necessary to establish an optimum composite observational system including the surface-based system and the space-based system. © 1985 Advances in Atmospheric Sciences."
"57192504085;","The second order approximation to the nonlinear wave in barotropic atmosphere",1985,"10.1007/BF03179749","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956558182&doi=10.1007%2fBF03179749&partnerID=40&md5=53363ac73dc81524e40925ed0301cde7","A kind of technique of computer extension of perturbation series is presented and used in seeking for the second-order approximation to a large-scale travelling wave solution of the barotropic primitive equations. Numerical experiments show that the second-order approximation keeps major characters of the travelling wave solution and is indeed more exact than the zero-order and the first order approximations. © 1985 Advances in Atmospheric Sciences."
"7202741460;57206313116;","Axisymmetric, primitive equation, spectral tropical cyclone model. Part I: formulation.",1985,"10.1175/1520-0469(1985)042<1213:APESTC>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022264254&doi=10.1175%2f1520-0469%281985%29042%3c1213%3aAPESTC%3e2.0.CO%3b2&partnerID=40&md5=dccff9ccc81ea052ce0b26ec228542c1","The results illustrate the role of gravity-inertia waves in the forced transverse circulation and the quasi-gradient rotational flow. The model provides a simple framework in which to study the effects of friction and moist physics on nonlinear normal mode initialization procedures. -from Authors"
"7401571939;","Energy analysis of a recent approximation to the atmospheric primitive equations.",1984,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021560685&partnerID=40&md5=59db415b626240a0eceb559a28f986bc","An approximation to the thermodynamic equation was introduced by Holton which was motivated by an energy principle involving a quadratic expression in temperature deviation, which he identified as available potential energy. The approximation consists of neglecting the component of adiabatic warming/cooling due to the temporally and horizontally variable part of the specific volume on a constant pressure surface. If the approximation is made, the system lacks a total energy principle involving either total potential energy or available potential energy (except in one special case).-from Author"
"7202386372;","Evaluation of the synoptic and mesoscale predictive capabilities of a mesoscale atmospheric simulation system.",1983,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020895058&partnerID=40&md5=097b1678312b0098714f8b115971de80","The overall performance characteristics of a limited area, hydrostatic, fine (52 km) mesh, primitive equation, numerical weather prediction model are determined in anticipation of satellite data assimilations with the model. The synoptic and mesoscale predictive capabilities of version 2.0 of this model, the Mesoscale Atmospheric Simulation System, are evaluated. -from STAR, 21(14), 1983"
"57212642698;","A rapidly travelling planetary‐scale instability in the atmosphere",1983,"10.1029/GL010i012p01176","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020903783&doi=10.1029%2fGL010i012p01176&partnerID=40&md5=274845851e717d6fe7680554def191bc","The hydrodynamic instability of the zonally averaged circulation of the atmosphere is investigated using a primitive equation model on a global domain. The classical baroclinically unstable modes are examined and a new mode of instability is found. This mode has phase‐speed greater than the maximum zonal flow velocity (such a solution is impossible within the framework of quasi‐geostrophic theory). It draws energy from the mean flow in the troposphere through baroclinic conversion and it penetrates deeply into the middle atmosphere, its growth there being supported by convergence of vertical wave energy flux. With zonal wavenumber one it has a period of two days and an e‐folding time of six days. Such instabilities may play an important role in the dynamics of the middle atmosphere. Copyright 1983 by the American Geophysical Union."
"7004014731;","Global-scale disturbances and dynamic similarity.",1980,"10.1175/1520-0469(1980)037<0473:GSDADS>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0019144493&doi=10.1175%2f1520-0469%281980%29037%3c0473%3aGSDADS%3e2.0.CO%3b2&partnerID=40&md5=5a67ed9bd2b0a4c9143081549dd6b0c9","Terms in the linearized primitive equations for a generally baroclinic atmosphere are evaluated for their significance in maintaining balance for global-scale disturbances. The disturbance energy equation is developed for the general basic state, and the influence that the approximations have on its balance is evaluated. -from Author"
"16494243100;6701805170;","On the use of biorthogonalization for solving systems of linear equations in numerical weather forecasting",1979,"10.1007/BF01633918","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250272137&doi=10.1007%2fBF01633918&partnerID=40&md5=20354596e18868aa686eef023cea2a36","The paper deals with the solving of large systems of linear equations which are created when implicit and semi-implicit differential methods are used to solve the primitive equations of the atmosphere. Systems with similar properties are also created in solving boundary problems of multi-level filtered models. First, the specific properties of these systems, which are then used to construct an efficient method of solving them, are described. © 1979 ACADEMIA Publishing House of the Czechoslovak Academy of Sciences."
"6602961573;","A case study of frontal developments in the Alps region.",1978,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0018053979&partnerID=40&md5=00aee47565ecc6f1805f12083e9f0c9c","The development of a frontal zone over Alps, during the period 21-23 July 1973, is discussed. The basic characteristic of this situation is an approach of subtropical and polar atmosphere with their respective jet streams. The results of the numerical prediction are presented, using an eight level limited area primitive equation model with or without orography. It is suggested that orography modifies the flow pattern through the entire troposphere during the course of development, but the frontogenesis in a low tropospheric layer is not an oreigenic process. Orography also dictates the place of strongest frontal activity. -from STAR, 17(17) 1979"
"7101771345;16674888200;","Internal gravity waves in the atmosphere",1974,"10.1007/BF02346427","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250424564&doi=10.1007%2fBF02346427&partnerID=40&md5=9e61ed6571465abf4dfd738937a67529","One of the shortcomings of at least those lee-wave theories which are mathematically tractable with relative ease, is that they do not satisfy the perturbation energy equation. In this report we started from a simplified energy equation and by parameterizing certain terms using plausible assumptions, we arrived at a solution of the primitive equations for internal gravity waves. Several cases of lee waves near Boulder were compared with this solution and results are encouraging. The proposed internal gravity wave solution suggests that wave formations observed in the noctilucent cloud region are most likely generated in situ and not propagated upward from the troposphere. © 1974 Springer-Verlag."
"7202155374;","On the formulation of a nonlinear atmospheric tidal theory from the meteorological primitive equations",1969,"10.1007/BF00875704","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250499859&doi=10.1007%2fBF00875704&partnerID=40&md5=603e70f661a11a18af296c27ad88b26e","The theory of atmospheric tides is derived from the meteorological primitive equations by means of a perturbation expansion in Rossby number. Separation of the system for the first order variables into the standard horizontal and vertical structure equations of tidal theory is effected. © 1969 Birkhäuser-Verlag."
"11939929300;55119602800;57208455668;18435749300;57192468922;56415743000;57195587405;57075896200;57138736900;8713807600;12244212300;7201972249;55193344000;57219605363;57219596453;57219732416;55747696500;57205651955;57219598521;8733578200;6602793307;54992767300;7103366892;","GFDL SHiELD: A Unified System for Weather-to-Seasonal Prediction",2020,"10.1029/2020MS002223","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094142042&doi=10.1029%2f2020MS002223&partnerID=40&md5=e773310b65b888d827fe136e750c48a8","We present the System for High-resolution prediction on Earth-to-Local Domains (SHiELD), an atmosphere model developed by the Geophysical Fluid Dynamics Laboratory (GFDL) coupling the nonhydrostatic FV3 Dynamical Core to a physics suite originally taken from the Global Forecast System. SHiELD is designed to demonstrate new capabilities within its components, explore new model applications, and to answer scientific questions through these new functionalities. A variety of configurations are presented, including short-to-medium-range and subseasonal-to-seasonal prediction, global-to-regional convective-scale hurricane and contiguous U.S. precipitation forecasts, and global cloud-resolving modeling. Advances within SHiELD can be seamlessly transitioned into other Unified Forecast System or FV3-based models, including operational implementations of the Unified Forecast System. Continued development of SHiELD has shown improvement upon existing models. The flagship 13-km SHiELD demonstrates steadily improved large-scale prediction skill and precipitation prediction skill. SHiELD and the coarser-resolution S-SHiELD demonstrate a superior diurnal cycle compared to existing climate models; the latter also demonstrates 28 days of useful prediction skill for the Madden-Julian Oscillation. The global-to-regional nested configurations T-SHiELD (tropical Atlantic) and C-SHiELD (contiguous United States) show significant improvement in hurricane structure from a new tracer advection scheme and promise for medium-range prediction of convective storms. ©2020. The Authors."
"57075822300;23768134300;7201709645;15056344900;7402721790;","A two-stage fourth-order multimoment global shallow-water model on the cubed sphere",2020,"10.1175/MWR-D-20-0004.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85093119922&doi=10.1175%2fMWR-D-20-0004.1&partnerID=40&md5=97cb76f18d7db1b377570adc11867146","A new multimoment global shallow-water model on the cubed sphere is proposed by adopting a two-stage fourth-order Runge-Kutta time integration. Through calculating the values of predicted variables at half time step t 5 tn 1 (1/2)Dt by a second-order formulation, a fourth-order scheme can be derived using only two stages within one time step. This time integration method is implemented in our multimoment global shallow-water model to build and validate a new and more efficient numerical integration framework for dynamical cores. As the key task, the numerical formulation for evaluating the derivatives in time has been developed through the Cauchy-Kowalewski procedure and the spatial discretization of the multimoment finite-volume method, which ensures fourth-order accuracy in both time and space. Several major benchmark tests are used to verify the proposed numerical framework in comparison with the existing four-stage fourth-order Runge-Kutta method, which is based on the method of lines framework. The two-stage fourth-order scheme saves about 30% of the computational cost in comparison with the four-stage Runge-Kutta scheme for global advection and shallow-water models. The proposed two-stage fourth-order framework offers a new option to develop high-performance time marching strategy of practical significance in dynamical cores for atmospheric and oceanic models. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"55753690200;57218558822;55431249600;16025236700;","Weight structure of the Local Ensemble Transform Kalman Filter: A case with an intermediate atmospheric general circulation model",2020,"10.1002/qj.3852","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089536254&doi=10.1002%2fqj.3852&partnerID=40&md5=c35dffd51824e38a9fc8db6e0a05b8b1","The Local Ensemble Transform Kalman Filter (LETKF) computes analysis by using a weighted average of the first-guess ensemble with surrounding observations within a localization cut-off radius. Since overlapped observations are assimilated at neighbouring grid points, the LETKF results in spatially smooth weights. This study explores the spatial structure of the weights with the intermediate atmospheric model SPEEDY (Simplified Parameterizations, Primitive Equation Dynamics). Based on the characteristics of the weight structure, we also aim to improve the weight interpolation (WI) method, which we use to compute the weights at coarser reference points and interpolate the weights into higher-resolution model grid points. The results show that larger localization and sparser observations result in spatially smoother weights. WI is less detrimental when weight patterns are spatially smoother. An advanced WI method with observation-density-dependent reference points results in better forecasts than those with uniformly distributed reference points. This improvement may be due to the spatially inhomogeneous localization function realized by the WI method with observation-density-dependent reference points. The spatial distribution of the optimal localization scales shows that larger (smaller) localization is beneficial in sparsely (densely) observed regions. The WI method is computationally more efficient with larger ensembles since the additional computational cost for the WI is lower than that for the LETKF. © 2020 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"57189331899;57203956372;55319076200;7003595038;7801353107;","A compatible finite-element discretisation for the moist compressible Euler equations",2020,"10.1002/qj.3841","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088803419&doi=10.1002%2fqj.3841&partnerID=40&md5=b5609195909fabd57f0ac91813591c20","A promising development of the last decade in the numerical modelling of geophysical fluids has been the compatible finite-element framework. Indeed, this will form the basis for the next-generation dynamical core of the Met Office. For this framework to be useful for numerical weather prediction models, it must be able to handle descriptions of unresolved and diabatic processes. These processes offer a challenging test for any numerical discretisation, and have not yet been described within the compatible finite-element framework. The main contribution of this article is to extend a discretisation using this new framework to include moist thermodynamics. Our results demonstrate that discretisations within the compatible finite-element framework can be robust enough also to describe moist atmospheric processes. We describe our discretisation strategy, including treatment of moist processes, and present two configurations of the model using different sets of function spaces with different degrees of finite element. The performance of the model is demonstrated through several test cases. Two of these test cases are new cloudy-atmosphere variants of existing test cases: inertia–gravity waves in a two-dimensional vertical slice and a three-dimensional rising thermal. © 2020 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"55796391600;57191637376;56193847400;55709136700;57196090861;57209329062;","Towards a dry-mass conserving hydrostatic global spectral dynamical core in a general moist atmosphere",2020,"10.1002/qj.3842","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85087860719&doi=10.1002%2fqj.3842&partnerID=40&md5=62fdbb9548926e1d7259184548503b03","The aim of this article is to develop a dry-mass conserving hydrostatic global spectral dynamical core in a general moist atmosphere, which can be regarded as an alternative, improved version of that used in the current Integrated Forecast System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). In contrast to the original IFS-like core, the dry-mass vertical coordinate is employed and the mass continuity equation is expressed in terms of the dry air density, which ensures the inherent conservation of dry air mass. Meanwhile, the thermodynamic equation is reformulated with a modified temperature variable and the formula used to compute the full pressure vertical velocity is derived rigorously. To assess the performance of this new core, an idealized tropical cyclone (TC) test is conducted. Simulation results from both the new core and the original IFS-like dynamical core are presented and compared. The results show that the TC-like storm produced by the new dynamical core is more intense, more compact and more concentric, and is thus much more in line with previous results from other global models. In this new dynamical core, the diagnosed full pressure vertical velocity is decomposed into four components, of which the first component, the dry hydrostatic pressure vertical velocity, dominates. Sensitivity experiments imply that despite their small numerical value the other three components should not be neglected, especially for medium-range forecasts. © 2020 Royal Meteorological Society"
"6506848305;56763174500;36856321600;57217846978;8859530100;56290437400;","The E3SM version 1 single-column model",2020,"10.5194/gmd-13-4443-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85092269118&doi=10.5194%2fgmd-13-4443-2020&partnerID=40&md5=1fab423b81368149251b5e14c4ccee69","The single-column model (SCM) functionality of the Energy Exascale Earth System Model version 1 (E3SMv1) is described in this paper. The E3SM SCM was adopted from the SCM used in the Community Atmosphere Model (CAM) but has evolved significantly since then. We describe changes made to the aerosol specification in the SCM, idealizations, and developments made so that the SCM uses the same dynamical core as the full general circulation model (GCM) component. Based on these changes, we describe and demonstrate the seamless capability to ""replay""a GCM column using the SCM. We give an overview of the E3SM case library and briefly describe which cases may serve as useful proxies for replicating and investigate some long-standing biases in the full GCM runs while demonstrating that the E3SM SCM is an efficient tool for both model development and evaluation. © Author(s) 2020."
"10144282600;8687063000;57212215393;35228711600;7004713805;","Cascading Toward a Kilometer-Scale GCM: Impacts of a Scale-Aware Convection Parameterization in the Goddard Earth Observing System GCM",2020,"10.1029/2020GL087682","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85090845731&doi=10.1029%2f2020GL087682&partnerID=40&md5=087beac7578f8140724cf839ff6e657f","The National Aeronautics and Space Administration (NASA) Goddard Earth Observing System global circulation model (GCM) is evaluated through a cascade of simulations with increasing horizontal resolution. This model employs a nonhydrostatic dynamical core and includes a scale-aware, deep convection parameterization (DPCP). The 40-day simulations at six resolutions (100 km to 3 km) with unvarying model formulation were produced. At the highest resolution, extreme experiments were carried out: one with no DPCP and one with its scale awareness eliminated. Simulated precipitation, radiative balance, and atmospheric thermodynamic and dynamical variables are well reproduced with respect to both observational and reanalysis data. As model resolution increases, the convective precipitation smoothly transitions from being mostly produced by the convection parameterization to the cloud microphysics parameterization. However, contrary to current thought, these extreme cases argue for maintaining, to some extent, the scale-aware DPCP even at 3-km scale, as the run relying solely on explicit grid-scale production of rainfall performs more poorly at this resolution. ©2020. American Geophysical Union. All Rights Reserved. This article has been contributed to by US Government employees and their work is in the public domain in the USA."
"7102201685;","The unique, well posed reduced system for atmospheric flows: Robustness in the presence of small scale surface irregularities",2020,"10.1016/j.dynatmoce.2020.101143","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086598133&doi=10.1016%2fj.dynatmoce.2020.101143&partnerID=40&md5=d27f26b08e615cb0c6feddf0d9d90b82","It is well known that the primitive equations (the atmospheric equations of motion under the additional assumption of hydrostatic equilibrium for large scale motions) are ill posed when used in a limited area on the globe. Yet the atmospheric equations of motion for large scale motions are essentially a hyperbolic system that with appropriate boundary conditions should lead to a well posed system in a limited area. This apparent paradox was resolved by Kreiss through the introduction of the mathematical Bounded Derivative Theory (BDT) for any symmetric hyperbolic system with multiple time scales (as is the case for the atmospheric equations of motion). The BDT uses norm estimation techniques from the mathematical theory of symmetric hyperbolic systems to prove that if the norms of the spatial and temporal derivatives of the ensuing solution are independent of the fast time scales (thus the concept of bounded derivatives), then the subsequent solution will only evolve on the advective space and time scales (slowly evolving in time in BDT parlance) for a period of time. The requirement that the norm of the time derivatives of the ensuing solution be independent of the fast time scales leads to a number of elliptic equations that must be satisfied by the initial conditions and ensuing solution. In the atmospheric case this results in a 2D elliptic equation for the pressure and a 3D equation for the vertical component of the velocity. Utilizing those constraints with an equation for the slowly evolving in time vertical component of vorticity leads to a single time scale (reduced) system that accurately describes the slowly evolving in time solution of the atmospheric equations and is automatically well posed for a limited area domain. The 3D elliptic equation for the vertical component of velocity is not sensitive to small scale perturbations at the lower boundary so the equation can be used all of the way to the surface in the reduced system, eliminating the discontinuity between the equations for the boundary layer and troposphere and the problem of unrealistic growth in the horizontal velocity near the surface in the hydrostatic system. © 2020 Elsevier B.V."
"57218513329;57218512218;55272861800;","Analysis of and Solution to the Polar Numerical Noise Within the Shallow-Water Model on the Latitude-Longitude Grid",2020,"10.1029/2020MS002047","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089844656&doi=10.1029%2f2020MS002047&partnerID=40&md5=4e4d2909babf0216bfae3c056dbb3174","This study conducts an analysis of the polar numerical noise in the barotropic shallow-water version of the Grid-point Atmospheric Model of IAP LASG (GAMIL-SW) and provides a good solution to the problem. GAMIL-SW suffers from numerical noise in the polar region in some ideal test cases, which is likely to be detrimental to the full physical model. The noise is suspected to be related to the nonlinear advection term in the momentum equation. Thus, a new shallow-water model with a vector-invariant form of the momentum equation is developed on the latitude-longitude grid to analyze the polar noise. It is found that the version with meridional wind component staggered on the pole is free from noise, while the version with zonal wind component staggered on the pole is still contaminated. By redefining the polar relative vorticity, the polar noise is eliminated in the latter version, and the global conservation properties are maintained. In addition, the test cases demonstrate that the new shallow-water model maintains the properties of the original GAMIL-SW with respect to numerical accuracy and computational stability. This study helps to identify appropriate governing equations to further develop the next generation of GAMIL dynamical core. © 2020. The Authors."
"56541813000;7401594160;57207473157;","Investigation of the effect of the time step on the physics–dynamics interaction in CAM5 using an idealized tropical cyclone experiment",2020,"10.1007/s00382-020-05284-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084582636&doi=10.1007%2fs00382-020-05284-5&partnerID=40&md5=b40a99b897b37af350b55535c63e20b4","To understand the effect of the time step on the physics–dynamics interaction in a model, we used an idealized tropical cyclone test to evaluate the sensitivities to the physics time step in the Community Atmosphere Model Version 5 (CAM5). The investigated time steps were 450, 900 and 1800 s at a resolution of 1°, and 225, 450, 900 and 1800 s at a resolution of 0.25° in the corresponding ensemble simulations. We found that the intensity and precipitation of the simulated tropical cyclone and the physics parameterizations are fairly sensitive to the time step. These sensitivities are affected by the dynamical core and the physics–dynamics coupling strategy and vary with the horizontal resolution. In low-resolution runs, the intensity of the simulated tropical cyclone varies little with physics time step in the finite volume (FV) dynamical core, but it tends to weaken with decreasing time steps in the spectral element (SE) dynamical core. The horizontal circulation of the tropical cyclone in both the FV and SE simulations increases as the length of the time step decreases in high-resolution runs, where large-scale condensation dominates. The sensitivities in the physical parameterizations to time step play an important role in regulating the impact of time step on the physics–dynamics interaction, especially in high-resolution simulations. Compared with the sequential coupling approach (ftype1) with a sudden adjustment at each physics time step in the SE core, the dribbling coupling strategy (ftype0) that adjusts the state more gradually weakens the effect of the physical parameterizations. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature."
"57217098748;8876238100;7003814396;","Implementing the HYbrid MAss flux Convection Scheme (HYMACS) in ICON – First idealized tests and adaptions to the dynamical core for local mass sources",2020,"10.1002/qj.3812","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086244483&doi=10.1002%2fqj.3812&partnerID=40&md5=1db9731241d70e05178e276a22608531","In this study, the Hybrid MAss flux Convection Scheme (HYMACS) is implemented in the ICOsahedral Non-hydrostatic (ICON) weather prediction model. In contrast to conventional convection parametrization schemes, the convective up- and downdraughts are solely treated as subgrid-scale processes in HYMACS, whereas the environmental subsidence is passed to the grid-scale dynamics of the hosting model. It is shown that the operational anisotropic divergence damping in ICON distorts the grid-scale dynamical response on the net mass transport parametrized by HYMACS. Thus, a revised numerical filter configuration is developed which focuses on both the compatibility to local mass sources (sinks) and the effective suppression of numerical modes inherent from the model's triangular grid. Evaluation of Jablonowski–Williamson dynamical core experiments reveal that the combination of an isotropic second-order divergence damping with a modified version of the fourth-order divergence damping outperforms against numerical filters based on diffusion. The obtained results are similar to the operational set-up indicating just a minor effect on the properties of the dynamical core. Moreover, a series of dry mass lifting experiments with the revised numerical filter confirms its compatability with HYMACS. The distortion of the grid-scale circulation is removed while gravity waves are still retained despite the potentially degenerative effect of the fourth-order divergence damping. Analyses of kinetic energy spectra confirm the effective suppression of checkerboard noise for a wide range of different situations. The present study may be understood as a base for future applications of HYMACS with a full cloud model in real-case studies. © 2020 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"56915435100;57196718266;57205906385;7006069664;","Performance of hydrostatic and non-hydrostatic dynamical cores in RegCM4.6 for Indian summer monsoon simulation",2020,"10.1002/met.1915","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086993438&doi=10.1002%2fmet.1915&partnerID=40&md5=2274aac3a222aec057605dc110b42d0a","The efficacy of regional climate model RegCM4.6 using hydrostatic core resolutions at 36km (HY36) and 12km (HY12) and a non-hydrostatic core resolution at 12km (NH12) is investigated by simulating the normal, excess and deficit monsoon seasons. The ERA-Interim reanalysis data are used to drive the model and the India Meteorological Department (IMD) and modern-era retrospective analysis for research and applications (MERRA) rainfall data are used for precipitation verification. The heavy rainfall regions are well simulated in the high- compared with the coarse-resolution simulations, with the maximum in the NH12. The non-hydrostatic dynamics amalgamate the vertical acceleration with the orographic uplifting that causes more precipitation over hilly regions than that of the hydrostatic core. On the other hand, the lesser precipitation over northwest India is better portrayed in the HY12 than in the other two. Over central India, the HY36 performs better followed by the NH12; and the contrasting precipitation features are also well depicted in the HY36 and NH12. This is probably because of the better representation of large-scale monsoon features, such as a monsoon trough in the HY36 and local-scale convective activities in the NH12. Daily rainfall analysis also shows that the high-resolution model is capable of capturing the active and break phases during the El Niño and La Niña seasons. The non-hydrostatic model possesses good correlation co-efficients >0.5 over the hydrostatic model with co-efficients of 0.35. The analysis of upper air circulations and the derived parameters, including statistical tests, confirm that the RegCM4.6 with non-hydrostatics is useful for orographic regions, hydrostatic at a coarse resolution and non-hydrostatic at a finer resolution and could be suitable for plain regions. © 2020 The Authors. Meteorological Applications published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society."
"7103060756;","At the dawn of global climate modeling: The strange case of the Leith atmosphere model",2020,"10.5194/hgss-11-93-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084235227&doi=10.5194%2fhgss-11-93-2020&partnerID=40&md5=9c05725b592ed6c2c4a3d113e1afda85","A critical stage in the development of our ability to model and project climate change occurred in the late 1950s-early 1960s when the first primitive-equation atmospheric general circulation models (AGCMs) were created. A rather idiosyncratic project to develop an AGCM was conducted virtually alone by Cecil E. Leith starting near the end of the 1950s. The Leith atmospheric model (LAM) appears to have been the first primitive-equation AGCM with a hydrological cycle and the first with a vertical resolution extending above the tropopause. It was certainly the first AGCM with a diurnal cycle, the first with prognostic clouds, and the first to be used as the basis for computer animations of the results. The LAM project was abandoned in approximately 1965, and it left almost no trace in the journal literature. Remarkably, the recent internet posting of a half-century-old computer animation of LAM-simulated fields represents the first significant ""publication"" of results from this model. This paper summarizes what is known about the history of the LAM based on the limited published articles and reports as well as transcripts of interviews with Leith and others conducted in the 1990s and later. © 2019 BioMed Central Ltd.. All rights reserved."
"6507501796;6602624175;7102239370;7102645933;57199181531;57002623400;15765007300;13406399300;","Enforcing conservation of axial angular momentum in the atmospheric general circulation model CAM6",2020,"10.5194/gmd-13-685-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85080945422&doi=10.5194%2fgmd-13-685-2020&partnerID=40&md5=41e2519792e2da5ca3e96304d448272c","Numerical general circulation models of the atmosphere are generally required to conserve mass and energy for their application to climate studies. Here we draw attention to another conserved global integral, viz. the component of angular momentum (AM) along the Earth's axis of rotation, which tends to receive less consideration. We demonstrate the importance of global AM conservation in climate simulations with the example of the Community Atmosphere Model (CAM) with the finite-volume (FV) dynamical core, which produces a noticeable numerical sink of AM. We use a combination of mathematical analysis and numerical diagnostics to pinpoint the main source of AM non-conservation in CAM-FV. We then present a method to enforce global conservation of AM, and we discuss the results in a hierarchy of numerical simulations of the atmosphere of increasing complexity. In line with theoretical expectations, we show that even a crude, non-local enforcement of AM conservation in the simulations consistently results in the mitigation of certain persistent model biases. © 2020 Author(s)."
"57204950288;56416175400;56994000000;7006244721;55910431900;","A budget equation for the amplitude of Rossby wave packets based on finite-amplitude local wave activity",2020,"10.1175/JAS-D-19-0149.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85081612138&doi=10.1175%2fJAS-D-19-0149.1&partnerID=40&md5=4a9c3291b8501ff632a088d24b7d4937","Recently, the authors proposed a novel diagnostic to quantify the amplitude of Rossby wave packets. This diagnostic extends the local finite-amplitude wave activity (LWA) of N. Nakamura and collaborators to the primitive-equations framework and combines it with a zonal filter to remove the phase dependence. In the present work, this diagnostic is used to investigate the dynamics of upper-tropospheric Rossby wave packets, with a particular focus on distinguishing between conservative dynamics and nonconservative processes. For this purpose, a budget equation for filtered LWA is derived and its utility is tested in a hierarchy of models. Idealized simulations with a barotropic and a dry primitive-equation model confirm the ability of the LWA diagnostic to identify nonconservative local sources or sinks of wave activity. In addition, the LWA budget is applied to forecast data for an episode in which the amplitude of an upper-tropospheric Rossby wave packet was poorly represented. The analysis attributes deficiencies in the Rossby wave packet amplitude to the misrepresentation of diabatic processes and illuminates the importance of the upper-level divergent outflow as a source for the error in the wave packet amplitude. © 2019 American Meteorological Society."
"57209469769;","Balancing the Potential Vorticity Seesaw: The Bare Essentials of Baroclinic Instability",2019,"10.1007/s41748-019-00128-7","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074919696&doi=10.1007%2fs41748-019-00128-7&partnerID=40&md5=54394326e49ce1eddff33367e4337fa5","This paper bypasses the mathematical technicalities of baroclinic instability and tries to provide a more conceptual, mechanistic explanation for a phenomenon that is fundamentally important to the dynamics of the earth’s atmosphere and oceans. The standard conceptual picture of baroclinic instability is reviewed and stripped down to identify the most essential features. These are: (a) Regions with both positive and negative potential vorticity (PV) gradients, (b) separate Rossby wave perturbations in each region where PV gradients are of different signs, and (c) cooperative phase locking between Rossby waves in regions of opposite PV gradient, which renders them stationary, and allows them to amplify to reduce the background temperature gradient (or baroclinicity) while still conserving total PV. These three factors constitute the “counterpropagating Rossby wave” perspective, and suggest the heuristic picture of a “PV seesaw”, which remains balanced as the instabilities (i.e., the phase-locked PV wave perturbations) grow out along opposite limbs. After reviewing the key characteristics of PV and Rossby waves, the process is illustrated by the spontaneous onset of baroclinic instability during spin-up of the Held–Suarez dynamical core atmospheric model. © 2019, The Author(s)."
"57190741940;6508060859;","Using the concept of the dynamic state index for a scale-dependent analysis of atmospheric blocking",2019,"10.1127/metz/2019/0963","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078209122&doi=10.1127%2fmetz%2f2019%2f0963&partnerID=40&md5=537d3d72d9efe84bcc38c53fb70a7d85","The present study investigates the phenomenon of atmospheric blocking using a cascade of Dynamic State Indices. The different DSI variants signalize model dependent aspects of atmospheric blockings, which allows for a scale-dependent analysis of the corresponding flow pattern. Starting from the primitive equations, approximations lead to the reduced equations of the quasi-geostrophic model and the further approximated barotropic Rossby model. For each model a corresponding Dynamic State Index can be derived. All DSI variants underlie the same concept, such that the three variants capture the stationary and adiabatic state as well as their local deviations. The DSI variants are investigated in the framework of a case study of the atmospheric blocking phenomenon over the European part of Russia in summer 2010. Two main results are presented: (i) The anticyclone of the block is characterized by a large area with nearly vanishing DSI values in all three models. In contrast, the typical DSI dipoles along the jet that surrounds the block differ, dependent on the level of the model reduction, not only in the spatial extent but also in the amplitude. (ii) The DSI variants shows the difference of the impact of the diabatic processes related to precipitation concerning the back and front side of the high. The amplitudes of the negative mean of DSI values on the back side of the high, respectively the amplitudes of the positive DSI mean on the front side, is larger for the primitive equations than for the quasi-geostrophic model. Thus, the DSI is a unified concept for atmospheric dynamics designed to diagnose the scale-dependent footprints of the steady and adiabatic conditions as well as non-steady and diabatic processes depending on the level of the model reduction. © 2019 The authors"
"6603551529;","On material transport by shelf break eddies",2019,"10.1175/JPO-D-18-0166.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062534044&doi=10.1175%2fJPO-D-18-0166.1&partnerID=40&md5=39ecfc6839369f7ea57e730e8d0c5157","The Lagrangian motion in the eddy field produced from an unstable retrograde jet along the shelf break is studied from idealized numerical experiments with a primitive equation model. The jet is initially in thermal wind balance with a cross-isobath density gradient and is not subjected to any atmospheric forcing. Over the course of the model integration, the jet becomes unstable and produces a quasi-stationary eddy field over a 2-month period. During this period, the cross-slope flow at the shelf break is characterized by along-slope correlation scales ofO(10) km and temporal correlation scales of a few days. The relative dispersion of parcels across isobaths is found to increase with time as tb, where 1 &lt; b &lt; 2. This mixed diffusive-ballistic regime appears to reflect the combined effects of (i) the short length scales of velocity correlation at the shelf break and (ii) the seaward excursion of monopolar and dipolar vortices. Cross-slope dispersion is greater offshore of the front than inshore of the front, as offshore parcels are both subducted onshore below density surfaces and translated offshore with eddies. Nonetheless, the exchange of parcels across the jet remains very limited on the monthly time scale. Particles originating from the bottom experience upward displacements of a few tens of meters and seaward displacements of O(100) km, suggesting that the eddy activity engendered by an unstable along-slope jet provides another mechanism for bottom boundary layer detachment near the shelf edge. © 2019 American Meteorological Society."
"57203137607;55268383800;57211149275;7202297669;7501701685;57203972987;","Relationship between a function of the northward pressure gradient and the Pacific Equatorial Undercurrent",2018,"10.1007/s13131-018-1262-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85053849468&doi=10.1007%2fs13131-018-1262-9&partnerID=40&md5=964f9c8b9ac6f7ee83e6372f4868f89e","The Equatorial Undercurrent (EUC) plays an important role in ocean circulation and global climate change. Near the equator, as the Coriolis parameter goes to 0, equatorial currents cannot be described by geostrophy in which the pressure gradient force term is balanced by the Coriolis force term. Many previous studies focus on the relationships between the EUC and El Niño-Southern Oscillation (ENSO), the thermocline, sea surface topography, the distribution of equatorial wind stress and other atmosphere-ocean factors. However, little attention has been paid to the northward pressure gradient (NGT), which may also be important to the EUC. The pressure can be regarded as a complex nonlinear function of terms including temperature, salinity and density. This study attempts to reveal the connection between a function of the northward pressure gradient (FNP) and the EUC. The connection is derived from primitive equations, by simplifying the equations with using scaling analysis, and shows that the beta effect may be the main reason why the FNP is important to the EUC. The vertical structure of the EUC can be partially described by the FNP. The NGT has an obvious influence on the EUC while the eastward pressure gradient has a relatively smaller effect. © 2018, The Chinese Society of Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature."
"24172313200;55495632500;56182811900;36810780500;","A mechanism of the interdecadal changes of the global low-frequency oscillation",2018,"10.3390/atmos9080292","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054930328&doi=10.3390%2fatmos9080292&partnerID=40&md5=308df13fa9af2eec8dc195996e9d6fc8","Based on the National Center for Environmental Prediction/National Center for Atmospheric Research reanalysis dataset from 1948 to 2009, this study reveals that global low-frequency oscillation features two major temporal bands. One is a quasi-60-day period known as the intraseasonal oscillation (ISO), and the other is a quasi-15-day period known as the quasi-biweekly oscillation (QBWO). After the mid-1970s, both the ISO and QBWO become intensified and more active, and these changes are equivalently barotropic. The primitive barotropic equations are adopted to study the involved mechanism. It reveals that the e-folding time of the least stable modes of both the ISO and QWBO becomes shorter if the model is solved under the atmospheric basic state after the mid-1970s than if solved under the basic state before the mid-1970s. This result suggests that the atmospheric basic flow after the mid-1970s facilitates a more rapid growth of the ISO and QBWO, and thereby an intensification of the low-frequency oscillations at the two bands. © 2018 by the authors."
"36473238000;7102495827;","Effect of a high-order filter on a cubed-sphere spectral element dynamical core",2018,"10.1175/MWR-D-17-0226.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050147924&doi=10.1175%2fMWR-D-17-0226.1&partnerID=40&md5=c496454744eedff94b77c042c083cdc2","A high-order filter for a cubed-sphere spectral element model was implemented in a three-dimensional spectral element dry hydrostatic dynamical core. The dynamical core incorporated hybrid sigma-pressure vertical coordinates and a third-order Runge-Kutta time-differencing method. The global high-order filter and the local-domain high-order filter, requiring numerical operation with a huge sparse global matrix and a locally assembled matrix, respectively, were applied to the prognostic variables, except for surface pressure, at every time step. Performance of the high-order filter was evaluated using the baroclinic instability test and quiescent atmosphere with underlying topography test presented by the Dynamical Core Model Intercomparison Project. It was revealed that both the global and local-domain high-order filters could better control the numerical noise in the noisy circumstances than the explicit diffusion, which is widely used for the spectral element dynamical core. Furthermore, by adopting the high-order filter, the effective resolution of the dynamical core could be increased, without weakening the stability of the dynamical core. Computational efficiency of the high-order filter was demonstrated in terms of both the time step size and the wall-clock time. Because of the nature of an implicit diffusion, the dynamical core employing this filter can take a larger time step size, compared to that using the explicit diffusion. The local-domain high-order filter was computationally more efficient than the global high-order filter, but less efficient than the explicit diffusion. © 2018 American Meteorological Society."
"57189035823;57189266640;8284177100;6603178923;","Sub-inertial oscillations in the Black Sea generated by the semidiurnal tidal potential",2017,"10.1134/S000143381706007X","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85038098303&doi=10.1134%2fS000143381706007X&partnerID=40&md5=591247a3d3a7e50c8a9f8d01f925e3e3","The Black Sea shelf is a region of intense manifestation of various dynamical processes. Under the influence of different natural forces, eddy-wave phenomena develop here, which influence the general circulation of sea waters, biological productivity, and the condition of the engineering structures. Modern numerical models allow us to simulate and analyze the processes of the joint dynamics of marine circulation and large-scale waves. In this work, we study the spatiotemporal spectral characteristics of the sea level and velocity fluctuations formed due to atmospheric forcing and tidal potential. The hydrophysical fields are calculated using the Institute of Numerical Mathematics, Russian Academy of Sciences (INM RAS), σ model based on primitive equations. We use the CORE data as atmospheric forcing at the sea surface; the tidal potential is described by the semidiurnal lunar constituent M2. Analyzing the simulation results makes it possible to emphasize that accounting for the semidiurnal tidal potential not only improves the accuracy of the sea-level calculation at coastal stations, but also generates subinertial baroclinic oscillations previously found in the Black Sea from the data of in situ observations. © 2017, Pleiades Publishing, Ltd."
"57196214814;7004093651;","Numerical Effects on Wave Propagation in Atmospheric Models",2017,"10.1017/S1743921317007979","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062880221&doi=10.1017%2fS1743921317007979&partnerID=40&md5=3309faf9f90bddb3157312ab7fe6b2ed","Ray tracing techniques have been used to investigate numerical effects on the propagation of acoustic waves in a non-hydrostatic dynamical core discretised using an Arakawa C-grid horizontal staggering of variables (Arakawa & Lamb 1977) and a Charney-Phillips vertical staggering of variables (Charney & Phillips 1953) with a semi-implicit timestepping scheme. It is found that the space discretisation places limits on resolvable wavenumbers and redirects the group velocity of waves towards the vertical. Wave amplitudes grow exponentially with height due to the decrease in the background density, which can cause instabilities in whole-Atmosphere models. However, the inclusion of molecular viscosity and diffusion acts to damp the exponential growth of waves above about 150 km. This study aims to demonstrate the extent to which numerical wave propagation causes instabilities at high altitudes in atmosphere models, and how processes that damp the waves can improve these model's stability. Copyright © International Astronomical Union 2018."
"42961592400;26643566500;57189709466;","A semi-implicit modification to the Lorenz N-cycle scheme and its application for integration of meteorological equations",2016,"10.1175/MWR-D-15-0330.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84974792675&doi=10.1175%2fMWR-D-15-0330.1&partnerID=40&md5=abe670eafed48efd6855a1cb4c54c149","The Lorenz N-cycle is an economical time integration scheme that requires only one function evaluation per time step and a minimal memory footprint, but yet possesses a high order of accuracy. Despite these advantages, it has remained less commonly used in meteorological applications, partly because of its lack of semi-implicit formulation. In this paper, a novel semi-implicit modification to the LorenzN-cycle is proposed. The advantage of the proposed new scheme is that it preserves the economical memory use of the original explicit scheme. Unlike the traditional Robert-Asselin (RA) filtered semi-implicit leapfrog scheme whose formal accuracy is only of first order, the new scheme has second-order accuracy if it adopts the Crank-Nicolson scheme for the implicit part. A linear stability analysis based on a univariate split-frequency oscillation equation suggests that the 4-cycle is more stable than other choices of N. Numerical experiments performed using the dynamical core of the Simplified Parameterizations Primitive Equation Dynamics (SPEEDY) atmospheric general circulation model under the framework of the Jablonowski-Williamson baroclinic wave test case confirms that the new scheme in fact has second-order accuracy and is more accurate than the traditional RA-filtered leapfrog scheme. The experiments also give evidence for Lorenz's claim that the explicit 4-cycle scheme can be improved by running its two ""isomeric"" versions in alternating sequences. Unlike the explicit scheme, however, the proposed semi-implicit scheme is not improved by alternation of the two versions. © 2016 American Meteorological Society."
"55187262300;55612096100;56918729900;55435157400;35214175700;57211219633;","Reconstruction of a dynamical-statistical forecasting model of the ENSO index based on the improved self-memorization principle",2015,"10.1016/j.dsr.2015.03.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926361378&doi=10.1016%2fj.dsr.2015.03.002&partnerID=40&md5=286adf19ba60f494a19f4e58595c16a5","To address the inaccuracy of long-term El Niño-Southern Oscillation (ENSO) forecasts, a new dynamical-statistical forecasting model of the ENSO index was developed based on dynamical model reconstruction and improved self-memorization. To overcome the problem of single initial prediction values, the largest Lyapunov exponent was introduced to improve the traditional self-memorization function, thereby making it more effective for describing chaotic systems, such as ENSO. Equation reconstruction, based on actual data, was used as a dynamical core to overcome the problem of using a simple core. The developed dynamical-statistical forecasting model of the ENSO index is used to predict the sea surface temperature anomaly in the equatorial eastern Pacific and El Niño/La Niña events. The real-time predictive skills of the improved model were tested. The results show that our model predicted well within lead times of 12 months. Compared with six mature models, both temporal correlation and root mean square error of the improved model are slightly worse than those of the European Centre for Medium-Range Weather Forecasts model, but better than those of the other five models. Additionally, the margin between the forecast results in summer and those in winter is not great, which means that the improved model can overcome the ""spring predictability barrier"", to some extent. Finally, a real-time prediction experiment is carried out beginning in September 2014. Our model is a new exploration of the ENSO forecasting method. © 2015 Elsevier Ltd."
"56166045200;55115820600;6505525770;","The Plumes Influence on the General Circulation Along the Albanian Adriatic Region",2015,"10.1007/978-3-319-09300-0_76","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84945161491&doi=10.1007%2f978-3-319-09300-0_76&partnerID=40&md5=87b90a100174cc8ef04fda807b79729b","The plume structure is considered on the basis of simulations with a primitive equations model. In this scope, a σ-coordinate numerical model for the South-Eastern Adriatic Coast was configured to examine the dynamical properties under the winter wind, river, tidal, and atmospheric pressure forcing. The complex picture of the circulation is conjectured to be a balance between conventional forcing (tides, atmosphere and buoyancy) and the hitherto unknown effect of plumes as surface signatures of small scales instabilities in the sea regions of strong horizontal convergence. By using the plume as a new forcing mechanism, we obtain a general circulation pattern affected strongly by enhanced horizontal mixing. © Springer International Publishing Switzerland 2015."
"55656840900;15830929400;","Spectral atmospheric general circulation model version 2",2014,"10.1007/978-3-642-41801-3_1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028021428&doi=10.1007%2f978-3-642-41801-3_1&partnerID=40&md5=97e881705c1af77429b0c908334bb0c1","The spectral atmospheric general circulation model (AGCM) known as SAMIL2 is a 26-level rhombic truncated spectral model with a maximum wavenumber of 42. The dynamical core of SAMIL2contains two components. The first is a vertical hybrid coordinate, which combines the advantages of the pressure coordinate and orography-following coordinate. The other is a standard atmosphere subtraction scheme that reduces the truncation error of calculating the horizontal pressure gradient term over mountain slopes in lower model layers. The parameterization package of SAMIL2 covers the full physical processes in the atmosphere, including the revised K-distribution and two-stream radiation parameterization scheme, the nonlocal planet boundary layer scheme, multiple gravity wave drag parameterization, the revised cloud scheme, and three cumulus parameterization schemes. © Springer-Verlag Berlin Heidelberg 2014."
"56962915800;57218273453;56003637600;57217793376;57195425208;57195419512;55656353100;","Brief Introduction to the High-Resolution Grid-Point Atmospheric Model",2014,"10.1007/978-3-642-41801-3_39","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85028016841&doi=10.1007%2f978-3-642-41801-3_39&partnerID=40&md5=3066fc5573bdd1521317dc978699ae1e","In this study, a high-resolution grid-point atmospheric model (HGAM)has been developed on the basis of the dynamical core and physical package of the Grid-point Atmospheric Model of the National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics(LASG/IAP),version 2 (GAMIL2). The new model has threehorizontal resolution choices of 1° 9 1°, 0.5°9 0.5°, and 0.25° 9 0.25°, whereas its vertical layers are the same as those of GAMIL2. A 30-year integration of the Atmospheric Model Intercomparison Project (AMIP) is completed by using the 1° 9 1° version of HGAM; short-term integrations with the 0.5° 9 0.5° and 0.25° 9 0.25° versions are also conducted. The simulated results of precipitation by HGAM are shown as well as those by GAMIL2 for comparison. The geographical distribution of near-surface moisture by the 0.25° 9 0.25° version is also given."
"55901455800;57199726979;57198453689;","An integration method with fitting cubic spline functions to a numerical model of 2nd-order space-time differential remainder - For an ideal global simulation case with primitive atmospheric equations",2013,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886419958&partnerID=40&md5=b7d8dfd78bcbb4647f3d67bc6ead57e3","In this paper, the forecasting equations of a 2nd-order space-time differential remainder are deduced from the Navier-Stokes primitive equations and Eulerian operator by Taylor-series expansion. Here we introduce a cubic spline numerical model (Spline Model for short), which is with a quasi-Lagrangian time-split integration scheme of fitting cubic spline/ bicubic surface to all physical variable fields in the atmospheric equations on spherical discrete latitude-longitude mesh. A new algorithm of ""fitting cubic spline-time step integration-fitting cubic spline-......"" is developed to determine their first- and 2nd-order derivatives and their upstream points for time discrete integral to the governing equations in Spline Model. And the cubic spline function and its mathematical polarities are also discussed to understand the Spline Model's mathematical foundation of numerical analysis. It is pointed out that the Spline Model has mathematical laws of ""convergence"" of the cubic spline functions contracting to the original functions as well as its 1st-order and 2nd-order derivatives. The ""optimality"" of the 2nd-order derivative of the cubic spline functions is optimal approximation to that of the original functions. In addition, a Hermite bicubic patch is equivalent to operate on a grid for a 2nd-order derivative variable field. Besides, the slopes and curvatures of a central difference are identified respectively, with a smoothing coefficient of 1/3, three-point smoothing of that of a cubic spline. Then the slopes and curvatures of a central difference are calculated from the smoothing coefficient 1/3 and three-point smoothing of that of a cubic spline, respectively. Furthermore, a global simulation case of adiabatic, non-frictional and "" incompressible"" model atmosphere is shown with the quasi-Lagrangian time integration by using a global Spline Model, whose initial condition comes from the NCEP reanalysis data, along with quasi-uniform latitude-longitude grids and the so-called ""shallow atmosphere"" Navier-Stokes primitive equations in the spherical coordinates. The Spline Model, which adopted the Navier-Stokes primitive equations and quasi-Lagrangian time-split integration scheme, provides an initial ideal case of global atmospheric circulation. In addition, considering the essentially non-linear atmospheric motions, the Spline Model could judge reasonably well simple points of any smoothed variable field according to its fitting spline curvatures that must conform to its physical interpretation."
"56282183100;55740245100;","Comparison of the extended Kalman filter and the ensemble Kalman filter using the barotropic general circulation model",2009,"10.2151/jmsj.87.347","https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349596965&doi=10.2151%2fjmsj.87.347&partnerID=40&md5=08b0ba095dbb37c75c6ab8569b879096","In this study, we compare assimilation techniques of the full-rank extended Kalman filter (EKF) and the ensemble Kalman filter (EnKF), using a barotropic general circulation model, called barotropic S-model, under the perfect model configuration. We investigate the accuracy of the EnKF in reference to the direct computation of the EKF and examine the influence of the localization for EnKF. The barotropic S-model is based on the primitive equations and predicts the vertical mean state of the atmosphere. Although it has the predictability comparable to the operational prediction models, the direct computation of the EKF is possible. Therefore, we can assess the accuracy of the EnKF as a function of the ensemble members. In this study, the convergence of the EnKF to the EKF is examined using various ensemble members of 20, 50, 100, 410, and 1000. The EKF and EnKF directly assimilate the observation in the spectral space, and the observational elements are model variables. According to the result of the root mean square error (RMSE), the EnKF converges to the full-rank EKF filter when the ensemble member is increased to more than 50. It is demonstrated that the 20 ensemble members are insuffcient with respect to the convergence. An empirical orthogonal function (EOF) analysis is conducted using the covariance matrices of analysis error for both filters. The structure of the first EOF (EOF-1) indicates the characteristics of the baroclinic instability waves in mid-latitudes in both filters, showing the same geographical distributions when it has converged. Interestingly, another large analysis error is detected in the Arctic region. Furthermore, the influence of the localization is examined by introducing the local ensemble transform Kalman filter (LETKF), which assimilates the observations in the physical space. The observations which are assimilated by the LETKF are retrieved from the spectral space to the physical space. It is found that the analysis error of the non-localized EnKF in the spectral space is smaller than that of the LETKF in the physical space. It is concluded from the comparison of the RMSE that more than 50 ensemble members are required for the non-localized EnKF to converge to the full-rank EKF for the practical assimilation in the spectral space under the perfect model configuration of the barotropic general circulation model of the atmosphere. © 2009, Meteorological Society of Japan."
"35603331500;7005937197;","A first attempt at assimilating microwave-derived SST to improve the predictive capability of a coupled, high-resolution Eta-POM forecasting system",2009,"10.1080/01431160902842334","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77449118120&doi=10.1080%2f01431160902842334&partnerID=40&md5=d8763208add8ab54a1425b19dfc59e13","This study implements the assimilation of sea surface temperature (SST) data acquired by passive microwave remote sensing to a high-resolution, primitive-equation ocean model. The aim was to improve a forecasting tool capable of predicting the surface ocean processes linked to the air-sea interactions at sub-mesoscale level using one-way coupled, atmosphere-ocean modelling. An assimilation scheme based on a Newtonian relaxation scheme was fine-tuned to improve the forecasting skill of the ocean model. The ocean model was driven by predicted, synchronous air-sea fluxes derived by an overlying atmosphere model, remotely sensed SST and lateral boundary conditions derived from its previous run. The estimation of the model forecasting error was based on statistical and spatial comparison with remotely sensed observations. The optimal nudging coefficient was found to be 5 × 10-4 for 12 hours, giving a mean bias of -0.07°C. Forecast validation was done against calibrated AVHRR scenes using a new approach to calibrate region-specific scenes based on the split-window technique. This work demonstrates the benefit of using passive microwave remote sensing to improve high-resolution ocean forecasting systems. It also shows the high complementarity of infrared and passive microwave satellite sensors to provide information on the surface thermodynamics of the Ionian Sea. © 2009 Taylor &amp; Francis."
"22980035400;7005892157;","The efficacy of subsidence warming in tornadoes",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-36048981376&partnerID=40&md5=3459ae12cdb4647479b58251aa47cab7","Actual values of wind speed and pressure deficit of tornado and tornado-like vortices usually does not match the theoretical ones. To resolve the difference between the values obtained from observations and theory, the subsidence warming in the vortex core has been considered as a mechanism. This research provides the quantitative bounds on the efficacy of subsidence warming in idealized tornado-like vortices. The axisymmetric formulation of the incompressible primitive equations of motion was the basis for the model being used. This subsidence warming has small effect on the pressure deficit compared to other physical mechanisms and it does not have a significant impact on increasing the maximum wind speed."
"56247576300;","Information flow in ensemble weather predictions",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249015695&partnerID=40&md5=c11b6960f36e1ca17a9d354db95c4c68","Using several recent developments in information theory, uncertainty flow was explored using a moderate-resolution, primitive-equation atmospheric model with simplified physics. Consistent with operational experience in forecast centers and other methodologies explored in the literature, it was found that the midlatitude information flow is mainly in an easterly direction, although at low levels there is clear evidence that synoptic dynamics are important. To obtain reliable and stable results, rather large prediction ensembles were used. However, it was found that the basic qualitative results can be obtained with ensembles within present practical reach."
"14824964500;6603627138;6603393679;","Mapping the global structure of neutral mass density using data assimilation techniques",2006,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-33749361190&partnerID=40&md5=79a8834330e8875669cc5ed493e9b716","Thermospheric models are based on the ""primitive"" equations used routinely in lower atmosphere general circulation models for conventional weather forecasting. For the upper atmosphere, these equations are combined with the generalized diffusion equations to predict the total neutral mass density for satellite drag applications. Recently, the physical models have been combined with observations using data assimilation techniques in order to improve specification of density. The Kalman filter is well established but the challenge in the use of the physical model is in specifying the solar and geomagnetic driver. During the filter propagation step, incorrect drivers can push the state away from observations. The non-linear nature of the response renders the conventional linear methods inappropriate, more sophisticated tools are required including the ensemble Kalman filter."
"8722708300;8574213500;","Structure and timing of recirculation around Georges Bank: An observational and modeling study at the Great South Channel: Part I - Ensemble smoother",2005,"10.1016/j.csr.2004.09.018","https://www.scopus.com/inward/record.uri?eid=2-s2.0-19444373047&doi=10.1016%2fj.csr.2004.09.018&partnerID=40&md5=4b1bebc9a3cd431121c2c969de566370","An ensemble smoother is used to assimilate moored temperature, salinity, and velocity data into a local area primitive equation model. The overall goal of the analysis is to estimate variability of Georges Bank recirculation, i.e., northward flow through the Great South channel in support of the US Global Ocean Ecosystem Dynamics (GLOBEC) Georges Bank experiment. Here, identical twin experiments are carried out to test the ensemble smoother with a finite-element circulation model of the Great South Channel, based on a previous formulation designated QUODDY. The ensemble smoother utilizes a finite number of Monte Carlo model simulations to estimate model error covariance. The prior distribution from which the ensemble members are simulated is implicitly defined by the forward model by adding spatially correlated Gaussian random variables to the initial conditions, and time-dependent boundary elevations. Atmospheric forcing (wind stress) is derived from buoy measurements and is assumed to be known with certainty. The accuracy of the estimator depends on the state space variable being estimated and proximity to the data. In these twin experiments the domain-wide mean error variance of temperature, salinity, and velocity were reduced 96%, 93%, and 89%, respectively. The prediction statistics for the estimate are accurate throughout the domain. Non-linearity of the forward model and subsequent skewness of the posterior probability density function (pdf) are investigated. It is found that the posterior distribution is sufficiently Gaussian to use Gaussian confidence intervals. These results give confidence for using the numerical formulation and ensemble smoother to examine variability in circulation at Great South Channel with available data. © 2004 Published by Elsevier Ltd."
"7003713361;","Numerical forecast of weather variations for one month ahead: A possible approach",2005,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-20344373397&partnerID=40&md5=f3fd91ec8c1545cb1f387db89c70626d","At the beginning of the 1980s, Lorenz analyzed the reliability of weather forecasts of the European Center for Medium-Range Weather Forecasts (ECMWF) and concluded that the limit for forecasting day-to-day weather variations can reach one month. This optimistic conclusion was, on the whole, subsequently confirmed in. However, present-day forecasting models based on the system of the atmospheric primitive equations have virtually exhausted their capacity to predict for one week ahead. The objective of the present paper is to indicate a possible method for the practical solution of this problem. Copyright © 2005 by Pleiades Publishing, Inc."
"6603615285;","Inverse ocean modeling with ADCIRC",2004,"10.1016/S0167-5648(04)80148-5","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80051582160&doi=10.1016%2fS0167-5648%2804%2980148-5&partnerID=40&md5=6caa53151209f6116037cc63989edd8b","A modular system for ocean data assimilation has recently been developed. It has already been implemented in an unsophisticated way with a variety of models of the ocean and the coupled ocean-atmosphere. The system is currently being enhanced with modern information technology to facilitate the application of the system to models of coastal oceans, ocean basins, and the global ocean. One of the several ocean models that will interface with this ""Inverse Ocean Modeling System"" (IOM) is ADCIRC, a finite element circulation model for shelves, coasts, and estuaries. First, several aspects of the IOM are explained, with emphasis on features that facilitate its implementation with a variety of models. Second, the unique challenges of interfacing ADCIRC with the IOM are described, including the development of the time-discrete cost functional that depends on the primitive equation residuals (rather than the wave continuity residuals). Then the derivation of the forward and adjoint generalized wave continuity equations from the primitive Euler-Lagrange equations will be described by example. © 2004 Elsevier B.V."
"7404805734;7201771183;24469939600;6505843428;","RUC short-range ensemble forecast system",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442551649&partnerID=40&md5=a3fe27289f40d93c563a422ce289ab24","Various features of the Rapid Update Cycle (RUC) short-range ensemble forecast (SREF) system were discussed. The RUC forecast system is a NOAA operational weather prediction system. One of the unique features of the RUC is that its dynamical core is based on a hybrid potential temperature/sigma vertical coordinate. The RUC SREF system includes and interpolation package which interpolates NCEP's regional breeding modes gridded data onto RUC hybrid-coordinate grids."
"7404805734;7201771183;24469939600;6505843428;","RUC short-range ensemble forecast system",2004,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-2442429218&partnerID=40&md5=47570aba2fea551155d03343ad5af09f","A short-range ensemble forecast (SREF) is developed based on the rapid update cycle (RUC) model targeting for both operations and development. The dynamical core of the RUC is based on a hybrid potential-temperature/sigma vertical coordinate which adds to the model diversity. The statistical verification scores show that RUC SREF forecasts compare well against Eta analysis and Eta 12-km operational runs. The RUC SREF system includes an interpolation package which interpolates NCEP's regional breeding modes grided data into RUC hybrid-coordinate grids and runs twice daily with a total of 10 members."
"6603854428;7203024042;36487019100;","Ocean prediction at the U.S. Naval Research Laboratory",2003,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-1542610228&partnerID=40&md5=fb4010ea65d294490a5dcbdc2d623d29","The Oceanography Division of the Naval Research Laboratory conducts a coordinated program of research and development (R&D) supporting Navy operational ocean nowcast and prediction. This R&D program covers domains from global scales down to local surf zone scales. Included in these efforts are sophisticated primitive equation ocean circulation models on global, basin, and regional domains run on high performance computing platforms at the Naval Oceanographic Office (NAVO) and at the Fleet Numerical Meteorology and Oceanography Center (FNMOC). These efforts combine primitive equation models with observations using various assimilation techniques such as optimal interpolation using both in situ and satellite temperature and altimetry data. In addition to large scale and computationally significant models run at the Navy's central sites are the operationally relevant models designed to run on workstations and personal computers at the Navy's regional Meteorology and Oceanography Centers (METOCCEN) as well as on-scene. These latter capabilities can run stand-alone but also are designed to accept initial and boundary conditions available from the central site products. This allows for rapid relocatability to provide local area nowcasts and forecasts of temperature, salinity, currents, tides aad surface waves for the METOCCEN and for on-scene applications. This paper provides an overview on the present NRL R&D nowcast and prediction capabilities from global to local scales."
"55743330600;","The structure of anomalous oceanic circulation in the Indian Ocean dipole",2001,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0035672438&partnerID=40&md5=1ffffd7a86d9e64951ce361647fc0de0","Using an Indian-Pacific Ocean Circulation Model with high resolution a simulation study on the Indian Ocean dipole (IOD) has been done. Forcing the model with monthly observational wind stress in 1990-1999 the main characteristics of sea temperature variations in the two IODs (in 1997 and 1994) have been reproduced well. The patterns and center positions of sea temperature anomalies in the tropical Indian Ocean surface and in the section of equator-depth during the IOD from the simulation are basically consistent with that from observation. The physical image of anomalous circulation during IOD is revealed from the simulation. We find that an anomalous easterly current along the equator in the upper layer of the eastern Indian Ocean during IOD period. It is very strong, narrow band and is divergent from equator to both sides. It represents a Rossby wave propagated westwards. During IOD phase there a significant anomalous current cell in the section of equator-depth: the easterly current in the upper layer; westerly compensated current below it; a strong upwelling to the east of 80° E; a weak downwelling to the west of 55° E. Meanwhile two anomalous meridian cells are in the both sides of equator in the eastern Indian Ocean. The common upwelling of them is near equator. The patterns of anomalous current in the out of IOD phase are basically opposite to that in the IOD phase, besides the absolute value of the anomalous current is weaker. Therefore the anomalous sea temperature in the tropical Indian Ocean during IOD could be interpreted with anomalous horizontal and vertical current, especially large-scale upwelling and downwelling."
"56057021000;7004327593;","A semi-Lagrangian and semi-implicit scheme on an unstaggered horizontal grid",2000,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034354337&partnerID=40&md5=8ceb5086229bbd838a00fb53187991c6","A two time-level, two-dimensional semi-Lagrangian and semi-implicit (SLSI) scheme based on an unstaggered horizontal grid is presented for limited-area grid-point models of the atmosphere. A Lorenz grid is used for the vertical discretisation. An isothermal reference atmosphere with surface topography is used for the semi-implicit linearisation of the governing moist, diabatic, hydrostatic primitive equations. The momentum equation is discretised in vector form. Semi-implicit treatment of the gravity wave terms and linear part of the Coriolis force terms followed by a vertical decoupling transformation, lead to a set of two-dimensional separable elliptic equations that are solved by an efficient iterative solver. The main original contribution of this paper is in the use of the unstaggered horizontal A grid to develop the 2D SLSI scheme. The scheme is implemented in the regional NWP model LAPS (Limited Area Prediction System) of the Australian Bureau of Meteorology. The currently operational LAPS is an Eulerian model with 19 σ-levels in the vertical and a uniform horizontal resolution of 0.75°. While the fully explicit Eulerian model employs a time step of 90 s for computational stability, the SLSI model can use a time step up to 30 min. Results from 48 hour forecasts using the two models show that the newly developed SLSI model provides a stable, accurate, and computationally efficient alternative to the Eulerian model."
"56455165800;7003440089;","A sensitivity study of the subtropical ocean surface energy balance to the parameterization of precipitation from stratocumulus clouds",2000,"10.1023/A:1002482230580","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034029273&doi=10.1023%2fA%3a1002482230580&partnerID=40&md5=aa35f4ad70955eb6adafa55852dc3037","In the 'First Lagrangian' of the Atlantic Stratocumulus Experiment (ASTEX), a cloudy air mass was tracked as it was advected by the trade winds toward higher sea surface temperatures. In this study, a full diurnal cycle observed during this experiment is simulated and the impact of the precipitation parameterization is examined. The model we use is the one dimensional version of the hydrostatic primitive equation model MAR (Modele Atmospherique Regional) developed at the Universite catholique de Louvain (UCL). It includes an E-ε turbulence closure, a wide-band formulation of the radiative transfer, and a parameterized microphysical scheme allowing partial condensation. The model realistically reproduces the diurnal clearing of the cloud layer as well as the formation of cumulus clouds under the stratocumulus deck. Nevertheless, as the surface warms and the boundary layer becomes more convective, the simulation progressively differs from the observed evolution. Further experiments are carried out with different precipitation parameterizations commonly used in mesoscale models and general circulation models (GCMs). A strong sensitivity of the simulated liquid water path evolution is found. The impact on the surface energy flux and the solar flux reflected by the cloud is also examined. For both fluxes averaged over 24 hours, differences as large as 20 W m-2 are obtained between the various simulations. Low cloudiness covers large areas over the ocean and such errors on the reflected solar flux may strongly affect the Earth's radiative budget in GCM simulations. We estimate that the impact on the globally averaged outgoing solar flux could be as large as 5 W m-2. Furthermore, when atmospheric models are coupled to ocean models, errors in the surface energy exchanges may induce significant drift in the simulated climate."
"55719290500;7501797728;55388515800;","Numerical investigation of QBO in ozone",1999,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033395299&partnerID=40&md5=5fbb238f8ac5efda3124960a2088c7f7","In this paper, a two-dimensional primitive equation model, coupling dynamical, radiative and photochemical processes, is used to simulate the quasi-biennial oscillation (QBO) in ozone. The QBO in total ozone has been successfully simulated when the forcing of equatorial stratospheric QBO in zonal wind is imposed. The simulated characters of QBO in ozone are in close agreement with those observed. We further analyzed the mechanism of formation and maintenance of QBO in ozone. In the different phases of QBO in equatorial stratospheric wind field, the global circulation has so great difference that it makes the effects of advection transfer and eddy transfer present a quasi-biennial periodical variation. Chemical effect and dynamical effect are basically out-of-phase. They together form and maintain the QBO in ozone. Total variation rate is a tiny difference of the two large amounts. At the lower level of middle-high latitudes, however, it has a phase difference of about 1-2 months between dynamical and negative chemical effects, where the dynamical effect is comparatively greater. QBO in ozone has no clear counter effects on atmospheric circulation. The experiment results show that the effects of QBO in ozone on temperature field and wind field are very small."
"7409534589;","POLES sea ice model forcing data set",1999,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0033380952&partnerID=40&md5=6eacc8d87bb8d9dd2a1e03b444623fb4","This data set provides atmospheric fields which can be used as forcing fields for driving dynamic/thermodynamic sea ice models of the Arctic Ocean. Geostrophic winds are calculated from the twice daily IABP sea-level pressures blended with the daily NCAR reanalysis sea level pressures. The thermal forcing is calculated based on Parkinson and Washington (1979) using IABP-POLES surface air temperature data provided by I. Rigor. Ocean velocity and heat flux are output from a coupled ice-ocean model. The sea ice model is a multi-category thickness distribution model and the ocean model is a 3D primitive equation model (see Zhang et al. 1998). There are two sets of files. One set contains the geostrophic winds, the other the thermal forcing data. If you are downloading the data, please send an e-mail to zhang@apl.washington.edu, so we can update you on changes, bugs etc. If you are using the data and plan to publish the results, please use references found at the following URL. The sea ice model forcing data set description and access page is located at http://psc.apl.washington.edu/POLES/model_forcings/ModelForcings.html (source: Global Change Master Directory, http://gcmd.nasa.gov)."
"7409115135;7404852746;55494187900;57206651454;","A study on the mesoscale atmospheric dispersion or radiological releases from nuclear power plant in a coastal region",1999,"10.1080/10934529909376888","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344417901&doi=10.1080%2f10934529909376888&partnerID=40&md5=b6f471c3604027bf3ed6b6f94560fb1e","A Lagrangian atmospheric dispersion model combining a three dimensional prognostic sea-land breeze model has been developed and applied to the analysis of mesoscale atmospheric dispersion of radiological releases from the nuclear power plants in mountainous coastal regions. The hydrostatic primitive equations in the terrain-following coordinate system were used in the sea-land breeze model, and a Markov chain process and a kernel density estimator were used in the Lagrangian particle dispersion model. In this study, the mesoscale atmospheric circulation and particle dispersion simulations around the Wolsung nuclear power site located on the east coastline of Korea were carried out for two synoptic weather conditions on a clear day in summer by using the developed models. The simulated results showed that the atmospheric dispersions were affected by wind directions of sea breeze and land breeze according to synoptic weather conditions. And the simulated results have very good agreement with the observations.A Lagrangian atmospheric dispersion model combining a three dimensional prognostic sea-land breeze model has been developed and applied to the analysis of mesoscale atmospheric dispersion of radiological releases from the nuclear power plants in mountainous coastal regions. The hydrostatic primitive equations in the terrain-following coordinate system were used in the sea-land breeze model, and a Markov chain process and a kernel density estimator were used in the Lagrangian particle dispersion model. In this study, the mesoscale atmospheric circulation and particle dispersion simulations around the Wolsung nuclear power site located on the east coastline of Korea were carried out for two synoptic weather conditions on a clear day in summer by using the developed models. The simulated results showed that the atmospheric dispersions were affected by wind directions of sea breeze and land breeze according to synoptic weather conditions. And the simulated results have very good agreement with the observations."
"6603456128;","Ocean-atmosphere interactions on decadal timescales",1999,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032897008&partnerID=40&md5=9c0dcc679ea6d1ec5b355a8bd9e367fa","In this thesis, different processes that might contribute to the generation of decadal climate variability were investigated using general circulation models (GCMs) of the atmosphere and the ocean. First, the sensitivity of the atmospheric circulation to decadal changes in the underlying sea surface temperatures (SSTs) was estimated from an ensemble of six integrations of the Hadley Centre atmospheric GCM HadAM1, all forced by observed SSTs and sea-ice extents for the period 1949-93. Using a novel approach to estimate the 'true' SST-forced atmospheric response in the presence of spatially correlated internal atmospheric variability, the decadal atmospheric variability was studied over the North Atlantic and North Pacific regions. After filtering out the atmospheric circulation changes associated with the El Nino - Southern Oscillation (ENSO) phenomenon, the dominant mode of forced variability over the North Atlantic exhibits a meridional dipole in the mean sea level pressure (MSLP) field and is related to a tripole in the anomalous North Atlantic SSTs. Over large parts of the North Atlantic region, however, the atmospheric response is not consistent enough to provide feedbacks to the underlying ocean that could cause self-sustained decadal oscillations. Over the North Pacific the atmospheric response is dominated by ENSO. In addition to the ENSO-related response an independent decadal atmospheric signal was detected. It consistently involves large-scale wind stress curl anomalies over the North Pacific region. The effect of such wind stress curl anomalies on the ocean was studied in the second part of this thesis using the Hamburg Ocean Primitive Equation model (HOPE). It is shown how the adjustment of the North Pacific gyre circulation to large-scale wind stress curl anomalies determines the decadal timescale and how it may be exploited for predictions of decadal upper-ocean temperature changes in the central North Pacific. The HOPE model was also used to investigate a mechanism for the generation of decadal climate variability in the tropical Pacific which relies on subduction of midlatitudinal North Pacific SST anomalies and their equatorward propagation within the oceanic thermocline. It is demonstrated that such a mechanism is unlikely to cause decadal climate variability in the tropical Pacific."
"7409869897;7409515049;7409537010;7409509160;7409533492;","Numerical sea ice forecast system for the Bohai Sea in China",1998,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0032293544&partnerID=40&md5=0815453e552e3dbb67f7de33834705eb","Exploratory drilling and planning for production and transportation for oil and gas in the Bohai Sea during winter have raised great demand for numerical forecast of sea ice. A dynamic-thermodynamic ice model with three levels, level ice, rubble and open water, for simulating the ice growth, decay and drift in the Bohai Sea is presented on the basis of a review of the climate and ice conditions in the Bohai Sea and earlier sea ice modelling studies (like as Hibler 1979). The ice model was coupled with a tidal current model for research on ice-tide interaction, and coupled with Blumberg-Mellor Ocean model for improving numerical sea ice forecast. In order to develop an operational numerical ice prediction system for the Bohai Sea, the ice model is linked to a 5-level primitive equation atmospheric model with an atmospheric boundary layer model, and the products of numerical weather prediction from and the outputs of T106 atmospheric model from NMC of China are also used in the prediction system. The system includes input of initial ice fields besides the above models. Initial ice thickness and compactness are obtained from composite analyses and ice velosity is got by initialization. An objective verification procedure, application of forecast outputs and service are one of important parts of the operational system. The ice models is described and the operational forecast system is outlined in this paper."
"7103205398;35477562700;","The nonlinear response of a slowly-rotating atmosphere to mobile heating: Numerical experiments of relevance to the venusian atmosphere",1998,"10.2151/jmsj1965.76.5_783","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0041175234&doi=10.2151%2fjmsj1965.76.5_783&partnerID=40&md5=09e4ea03f90fe0d3a17001b5a982e729","The three-dimensional response of a slowly-rotating atmosphere to mobile heating is investigated by using a multi-layer primitive equation model on the sphere. The velocity of planetary rotation and that of solar heating are fixed at the values of Venus. The global circulation is assumed to be induced only by the solar radiation absorbed by the ground. The global circulation induced in this way can produce an atmospheric stability by the upward heat transport. In order to examine this nonlinear effect, the model is numerically integrated from a state of neutral stratification. It is found that the direct circulation between the day and night sides predominates always for standard parameter values. The temperature maximum point on the equator is deviated from the subsolar point by 60°. The horizontal temperature contrast between the day and night sides is very small (0.16 K in the lowest layer). The atmospheric stratification produced by the global circulation is also too weak even in the night side. In the experiments with one solar day assumed to be 1/2 or 1/4 of Venus' solar day (117 days), the zonally uniform meridional circulation appears in place of the direct circulation."
"7801686786;","Forecast of operational forecast skill with the adjoint of a primitive equation model",1997,"10.1175/1520-0493(1997)125<2984:FOOFSW>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-9444299028&doi=10.1175%2f1520-0493%281997%29125%3c2984%3aFOOFSW%3e2.0.CO%3b2&partnerID=40&md5=57fd6e888674a4a0210055c964d95600","In this article the author demonstrates the feasibility of a local skill forecast system based on the use of the adjoint of the tangent linear equations. A six-level adiabatic primitive equations spectral model of the atmospheric circulation, truncated at T42, is used. Local skill forecast from 1 to 3 days ahead is computed for a 3-month period, using the T42 model and the adjoint of its tangent linear equations. To highlight the effect of model error, the trajectories required by the adjoint model are chosen in various ways. First, it is the result of the integration of the direct low-resolution model. The trajectory is then interpolated from the forecast of the operational 24-level T119 variable resolution model used at Météo-France. Finally, the trajectory is interpolated from successive analyses. The initial error covariance matrix is built from the analysis error produced by the operational optimal interpolation system used at Météo-France and a simple correlation function. The weaknesses of the method are discussed, in particular the weak day-to-day variability of these variances. The large day-to-day variability of the forecast error variances is shown, in connection to the characteristics of the flow. The impact (from 48 h ahead) of the trajectory used by the adjoint model is also shown. Finally, a large set of variances is produced. Statistical connections between predicted variances and the skill of the forecasts of the model are described. The results show the potential usefulness of this product to help the forecaster to predict the evolution of the flow."
"57190613121;","Application of the semi-lagrangian method to global spectral forecast models",1997,"10.1080/07055900.1997.9687360","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85024030972&doi=10.1080%2f07055900.1997.9687360&partnerID=40&md5=8a8253300f62cb0e5bb7048e909710e6","Since the original demonstration of the efficiency advantage of the semi-Lagrangian semi-implicit method over a decade ago by André Robert, this numerical integration scheme is being used in an increasing range of atmospheric models. Most of the applications have been in grid point models, where it has been shown that this method permits the use of time steps that are much larger than those permitted by the Courant-Friedrich-Levy (CFL) criterion for the corresponding Eulerian models. In this paper we concentrate on its application in spectral models. A review of the steps towards its operational implementation in global spectral forecast models is presented. Linear stability and geometric aspects are considered for the problem of simple advection on the Gaussian grid that is used in spectral models. Nonlinear stability, accuracy and efficiency of the approach are illustrated by its application to a spectral model of the shallow water equations. Application in multilevel spectral primitive equations models is demonstrated with the Canadian Global Spectral Forecast Model and a high resolution version of the ECMWF Forecast Model. © 1997 Taylor & Francis Group, LLC."
"7402872647;","A comparative study of the heating effects of the Tibetan Plateau and the western Pacific",1996,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030430769&partnerID=40&md5=cca01c187c3b53ecb57e4efce388db2c","A zonal domain primitive equation modeling system (ZDMS) is used to study the effects of the initial heating anomalies over the Tibetan Plateau and the western Pacific on the East Asian and the Chinese summer climate, the relative importance and the mechanisms are discussed. Results show that in spite of the different locations of the heating anomalies the influences of the two anomaly areas are much similar to each other when the scaling of the two areas is the same. The two areas of heating anomalies have their own affecting domains in which one is more important than the other. In the western Pacific the heating anomaly over the western Pacific is more evident and in the Tibetan Plateau area the heating anomaly over the Tibetan Plateau is more obvious. For the east part of China the effects of the two heating anomalies both exist and almost have the equal importance. The initial anomaly of the sea surface temperature (SST) over the western Pacific can be kept during the entire time integration while in the Tibetan Plateau it can not be maintained."
"36870160800;7202245915;7005705115;7201398027;7402452111;","Simulations of tropical cyclone Connie from the Australian Monsoon Experiment",1996,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0030163265&partnerID=40&md5=98ad0fde96e66ebf9727f89fcdf309dd","Simulations have been made of tropical cyclone Connie which developed during the Australian Monsoon Experiment (AMEX) Phase 2. The aims are to investigate factors which affected the cyclone's movement. Experiments were made using a primitive equation model with parametrised physical processes, which has been developed at JMA (Japan Meteorological Agency). Reprocessed objective analyses from the European Centre for Medium Range Weather Forecasts (ECMWF), and the JMA's typhoon implantation scheme were used to generate the initial conditions. Analysis of the vorticity equation using data from the 24-hour simulations shows that the horizontal advection of absolute vorticity and the divergence term were dominant effects on the motion. This suggests that the track was determined by (a) steering flow, (b) the beta effect and (c) lower layer convergence which was generated and intensified by parametrised condensational heating. With regard to the beta effect, we illustrate that the motion in the three-dimensional atmosphere had similar characteristics to the motion of a vortex in a nondivergent barotropic flow. That is, the track was sensitive to tropical cyclone size, but insensitive to its inner core structure. Further, the track differences simulated from initial data containing circulations of different size became larger with simulation time. We conclude that to a first approximation, tropical cyclone Connie moved in a similar way to a vortex in a nondivergent barotropic flow, but its movement was modified by condensational heating."
"7005677595;","Free and rigid boundary quasigeostrophic models in pressure coordinates",1996,"10.1175/1520-0469(1996)053<1496:FARBQM>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5944238520&doi=10.1175%2f1520-0469%281996%29053%3c1496%3aFARBQM%3e2.0.CO%3b2&partnerID=40&md5=b90807199591a29bae23635a8ffbb05c","Starting from the hydrostatic primitive equations in pressure coordinates, a quasigeostrophic (QG) model is derived with temperature and ground surface pressure (GSP) as the governing prognostic fields. In this model iwo different tendency equalions for the GSP exist: one expressing mass conservation, and the other the condition of zero vertical velocity at the ground in common physical space. Comparison of these equations leads to a diagnostic relationship that provides a boundary condition for the omega equation. Equivalence of the system of equations to the QG model that employs the potential vorticity equation is established. Introduction of the GSP as one of the main prognostic fields highlights the problem of the lower boundary condition in pressure coordinates. Two models are introduced and studied, and their main features are compared - the free surface (FS) and the rigid boundary (RB) models, the latter being most common in pressure coordinate QG studies. The choice has an effect on the boundary conditions for the omega equation and affects the physical qualities of the model. The model with the FS has additional energy, similar to the energy of an elastic membrane, which the RB model lacks. Both models give similar results for synoptic-scale processes but differ essentially for scales larger than the external Rossby deformation radius (∼3000 km). As the scale analysis shows, the FS model is accurate in this case, while the RB model, which filters mass fluctuations of vertical unit columns of the atmosphere, seriously distorts the phase speeds."
"55740245100;","A life‐cycle of nonlinear baroclinic waves represented by a simple 3‐D spectral model",1995,"10.1034/j.1600-0870.1995.00113.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981625728&doi=10.1034%2fj.1600-0870.1995.00113.x&partnerID=40&md5=dd43b55e83fe1082510a9ad982ac6770","In this study, a life‐cycle experiment for baroclinic disturbances is carried out for Simmons and Hoskins' 45° jet by integrating a three‐dimensional spectral primitive equation model. The utility of the spectral representation in the vertical direction is examined for a fully nonlinear well‐established phenomenon. The energy evolution and corresponding energy transformation are analyzed in the framework of the baroclinic‐barotropic decomposition of atmospheric energy. According to the result, the initial perturbations of n= 6 grow exponentially drawing zonal baroclinic energy. This early evolution is reasonably described by linear baroclinic instability of the 45° jet. Both of baroclinic energy and barotropic energy of n= 6 increase simultaneously since the unstable mode maintains its consistent structure to grow. The energy flow is characterized as from zonal baroclinic energy via eddy baroclinic energy to eddy barotropic energy. These energy transformations are also synchronized since they are proportional to the eddy energy levels in the linear framework. When the waves reach the finite amplitude, the barotropic conversion increases, tranferring eddy barotropic energy toward zonal barotropic energy. It is shown by the result that the zonal barotropic energy increases when the waves decay, and the zonal jet is accelerated so that the structure becomes more barotropic. It is found by this study that the important baroclinic–barotropic interactions are coupled with baroclinic instability rather than the barotropic conversion. The results are consistent with previous studies. Therefore, we confirm also that the vertical spectral representation is applicable to simulate the nonlinear phenomenon. Copyright © 1995, Wiley Blackwell. All rights reserved"
"7409904646;7409727851;7409675740;7409697258;","Diagnosis of NWP systematic forecast errors in zonal mean circulation",1995,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029474864&partnerID=40&md5=5e13d8b659ca7c820ae32a534bff69c1","It is proved in this paper that NWP systematic forecast errors in the zonal mean circulation are due to the difference in westerly acceleration process during the forecasting period between model and real atmospheres. Those forcing factors which evoke the zonal mean wind variation can be split into various linear terms according to the non-acceleration theorem in a primitive equation system. By applying this technique to the diagnosis of the forecast products of the T42L9 model in January 1992 and in July 1992, it is indicated that the model has the ability to forecast the zonal mean wind to a reasonable extent, but there are still some errors in several places, especially in the upper troposphere and lower stratosphere in the mid-latitude region as well as near the surface. -from Authors"
"6506028155;","The climatic effects of the stratospheric volcanic ash",1993,"10.1007/BF02919136","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77951509439&doi=10.1007%2fBF02919136&partnerID=40&md5=aee589700e748f244941471536bc7011","The climatic effects of the stratospheric volcanic ash are simulated. The model we used is a primitive equation model with the P-σ incorporated coordinate system. The model has 5 layers in the atmosphere and 2 layers in the soil. The volcanic ash is introduced to the first (highest) model layer with a fixed optical thickness of 0.1275. Two comparative numerical experiments with and without the volcanic ash are made. Results show that the effects of the stratospheric volcanic ash on the formations of the mean climatic fields are much smaller than those of the land-sea distribution and the large scale topography. However, it does have contributions to the anomalies of the basic climatic states. The direct effect of the volcanic ash is to increase the temperature in the stratosphere. It can also influence the temperature and the height fields of isobaric surfaces, horizontal and vertical motions, precipitation and the surface climate through dynamic and thermodynamic processes in the atmosphere. © 1993 Advances in Atmospheric Sciences."
"6506696258;6506606301;7004184326;8833354000;","Analysis-Prediction experiments over Indian region using primitive equation barotropic model",1992,"10.1007/BF02677080","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649143177&doi=10.1007%2fBF02677080&partnerID=40&md5=c033ec04d307dd7cbaec21619be70420","The impact of initial guess and grid resolutions on the analysis and prediction has been investigated over the Indian region. For this purpose, an univariate objective analysis scheme and a primitive equation barotropic model have been used. The impact of initial guess and the resolutions on analysis and prediction is discussed. © 1992 Advances in Atmospheric Sciences."
"36815483700;55704449100;56131278400;57198742888;","A fine-Mesh numerical model with detailed boundary layer parameterization",1992,"10.1007/BF02677079","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649134290&doi=10.1007%2fBF02677079&partnerID=40&md5=9a5494c1e60921f4dfcfad577812a943","A fine-mesh numerical model with thirteen-layer, three-dimensional primitive equation is designed, which has a relatively high vertical resolution in the boundary layer and detailed boundary parameterization. A strong cold frontal process is simulated by the model. Comparison of the simulated results of this process with different models shows that the result of this model is prior to that of others, and that it is necessary to increase the vertical resolution and to take account of the physical processes in the boundary layer. © 1992 Advances in Atmospheric Sciences."
"7202909955;","Split-explicit integration of primitive equation barotropic model for the prediction of movement of monsoon depression",1992,"10.1007/BF02656933","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649140908&doi=10.1007%2fBF02656933&partnerID=40&md5=5a65ec001c1cd67fb34faa5ffba61b75","The split-explicit version of a limited area primitive equation barotropic model is formulated and tested for the prediction of movement of monsoon depressions. The model is integrated up to 48 hours with split-explicit time integration scheme (Gadd, 1978a) using input of four synoptic cases. The model is also integrated explicitly. The forecast results obtained from both the versions are compared and discussed. The computational time in former version is less than half of the computational time needed in explicit version. © 1992 Advances in Atmospheric Sciences."
"7004345429;","The birth of numerical weather prediction",1991,"10.1034/j.1600-0889.1991.t01-3-00006.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982729035&doi=10.1034%2fj.1600-0889.1991.t01-3-00006.x&partnerID=40&md5=b450b3287dd7b9a5b8268672565e1e5f","The paper describes the major events leading gradually to operational, numerical, short‐range predictions for the large‐scale atmospheric flow. The theoretical foundation starting with Rossby's studies of the linearized, barotropic equation and ending a decade and a half later with the general formulation of the quasi‐geostrophic, baroclinic model by Charney and Phillips is described. The problems connected with the very long waves and the inconsistences of the geostrophic approximation which were major obstacles in the first experimental forecasts are discussed. The resulting changes to divergent barotropic and baroclinic models and to the use of the balance equation are described. After the discussion of the theoretical foundation, the paper describes the major developments leading to the Meteorology Project at the Institute for Advanced Studied under the leadership of John von Neumann and Jule Charney followed by the establishment of the Joint Numerical Weather Prediction Unit in Suitland, Maryland. The inter‐connected developments in Europe, taking place more‐or‐less at the same time, are described by concentrating on the activities in Stockholm where the barotropic model was used in many experiments leading also to operational forecasts. The further developments resulting in the use of the primitive equations and the formulation of medium‐range forecasting models are not included in the paper. Copyright © 1991, Wiley Blackwell. All rights reserved"
"7409928658;","Physical properties of the symmetric and anti-symmetric motions and related energy conversion",1991,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026305354&partnerID=40&md5=42e005826978c1968a7894784bb7861e","The physical properties of the symmetric and antisymmetric motions, such as the conservation of the absolute angular momentum, the mutual conversions between various forms of energy, have been analysed by using the sets of equation in p-coordinates controlling the motions in the primitive equation model atmosphere. The results show that only the symmetric component of zonal geopotential difference caused by orography and that of the zonal frictional torque, have contribution to the change of the global angular momentum, and that the mutual conversions between various forms of energy, in addition to those similar to the results in the classical case, include those associated with the symmetric and antisymmetric motions. -Author"
"7409540610;7409928658;","Numerical experiments in symmetric and asymmetric motions in the barotropic primitive equation model atmosphere",1991,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0026283696&partnerID=40&md5=06a925e802e6b7bb9a033fe879199371","Three numerical experiments have been carried out by using a spectral barotropic primitive equation model. It is found that the results obtained are quite similar to those with the barotropic filtered model. The main results read as follows: 1) In the case with symmetric orography or without orography, if the motion is symmetric (with respect to the equator, the same is true hereafter) at the initial instant, then it would be symmetric afterwards. 2) The antisymmetric orography distribution could cause antisymmetric motion, and the original symmetric motion might become asymmetric. -from Authors"
"56291425800;57207897678;","The impact of soil moisture on dispersion-related characteristics",1990,"10.1007/BF03008874","https://www.scopus.com/inward/record.uri?eid=2-s2.0-65749311632&doi=10.1007%2fBF03008874&partnerID=40&md5=34af470334ff0ad08e55059c88093147","This study investigates the impact of soil moisture availability on dispersion-related characteristics: surface friction velocity (u*), characteristic scales of temperature and humidity (T* and q*), the planetary boundary layer height (h) and atmospheric stability classified by Monin-Obukhov length (L), Kazanski-Monin parameter (μ) and convective velocity scale (w*) during daytime convective condition using a one-dimensional primitive equation with a refined soil model. © 1990 Advances in Atmospheric Sciences."
"7102011703;57193494348;57217496314;","Cyclogenesis and frontogenesis",1990,"10.1034/j.1600-0870.1990.00002.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981598923&doi=10.1034%2fj.1600-0870.1990.00002.x&partnerID=40&md5=bb0cd58c590691c74689e4c6710496f0","Detailed linear analysis of the stability of realistic atmospheric frontal structures using the full hydrostatic primitive equations has demonstrated that such localized baroclinic zones support instability at two distinct and well‐separated length scales, even when the frontal mean states have uniform potential vorticity. The first scale is associated with the well‐known Charney‐Eady mode of baroclinic instability with a wavelength of 3000–4000 km that is responsible for the generation of observed mid‐tropospheric long waves. The second scale is defined by an apparently new mode of baroclinic instability, that we have previously called the “cyclone mode”, which has a wavelength near 1000 km and is boundary confined rather than being troposphere filling as is the case of the Chamey‐Eady mode. The most important characteristic of the cyclone mode is that it is completely filtered by both the quasi‐geostrophic and semi‐geostrophic approximations to the equations of motion. In this paper, we demonstrate explicitly through the analysis of a specific case of polar low development that this new mode is an important actor in at least one recurrent atmospheric dynamical process. Besides reviewing and extending these linear stability analyses, we describe a number of rather interesting results that we have obtained from a new series of f‐plane analyses of the nonlinear life cycles of frontal baroclinic waves. These have already provided considerable new insight into the detailed dynamics of the processes through which frontal waves “break”. Copyright © 1990, Wiley Blackwell. All rights reserved"
"24786769900;","A regional spectral nested multilevel primitive equation model",1990,"10.1007/BF02919165","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84950384456&doi=10.1007%2fBF02919165&partnerID=40&md5=719d58b4716c77f3e89b4f83e0b57927","By means of vertical normal modes a regional nested multilevel primitive equation model can be reduced to several sets of shallow water equations characterized by various equivalent depths. Therefore, time integration of the model in spectral form can be performed in the manner similar to those used in the spectral nested shallow water equation model case. © 1990, Advances in Atmospheric Sciences. All rights reserved."
"7005890514;","On exact and approximate energy equations in pressure coordinates",1989,"10.1111/j.1600-0870.1989.tb00368.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981621750&doi=10.1111%2fj.1600-0870.1989.tb00368.x&partnerID=40&md5=4566a44d14412bbd7bd180c655bf6907","Studies of the atmospheric energy cycle have been common in meteorology since the modern formulation of the concept by Lorenz. Most of these studies have been based on the approximate version of the energy budget equations using pressure as the vertical coordinate given by Lorenz in the same paper. Inexactitude in the formulation of the energy budget equations in general and the isobaric coordinate version in particular arises from several sources: the neglect of topography in the definition of the reference state for available potential energy, the simplification of the lower boundary condition, the definition of mean and eddy components and in particular in the use of the Lorenz approximate equations. An exact version of the energy cycle equations in isobaric coordinates is derived. The equations are exact in the sense that they are derived from the hydrostatic primitive equations without further approximation. It is pointed out that results already obtained indicate that there is a non‐trivial difference between the exact and approximate versions of the energy budget equations. 1989 Blackwell Munksgaard"
"24789217700;24788222800;7101825844;","The effects of topography on the summer atmospheric energetics of the Northern Hemisphere in a low-resolution global spectral model",1988,"10.1007/BF02656780","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024257227&doi=10.1007%2fBF02656780&partnerID=40&md5=0f78a1636106dc7b47403e909c22a8e5","An analysis is made of the effects of topography on the summer atmospheric energetics of the Northern Hemisphere in a low-resolution global spectral model. The numerical mode! is a global, spectral, primitive equation model with five equally spaced sigma levels in the vertical and triangular truncation at wavenumber 10 in the horizontal. The model includes comparatively full physical processes. Each term of the energy budget equations is calculated in four specific latitudinal belts (81.11°S-11.53°S; 11.53°S-11.53°N; 11.53°N-46.24°N; 46.24°N-81.11°N) from a five-year simulation with mountains and a one-year simulation without mountains, respectively. Differences between them are compared and statistically tested. The results show that synoptical scale waves transport available potential energy and kinetic energy to long waves and increase conversion from available potential energy of the zonal flow to eddy's and from the eddy kinetic energy to the zonal kinetic energy in region 3 (11.53°N-46.24°N) due to mountains; topography intensifies the atmospheric baroclinity in region 3, consequently the baroclinic conversion of atmosphere energy is increased. The seasonal characteristics associated with the summer atmospheric energy source in region 3 are caused by seasonal variation of the solar radiation and the land-ocean contrasts and independent of topographic effects. The mechanism of topographic effects on the increase of long wave kinetic energy is also discussed. © 1988 Advances in Atmospheric Sciences."
"24788647100;7101771345;6701764745;56977620900;","On temperature initialization in primitive equation forecast models",1988,"10.1007/BF02656781","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024255311&doi=10.1007%2fBF02656781&partnerID=40&md5=007668562ab7b8aa31abac302f48cf15","Four procedures of specifying model initial temperature were described and tested in the present study. It was found that the use of observed temperatures along with a proper vertical interpolation scheme was not only acceptable, but produced less error than the use of temperatures derived from geopotential height through the hydrostatic equation did. Use of the difference form of the hydrostatic equation would produce unacceptable errors in the initial temperatures, unrealistic horizontal and vertical distribution of temperature, and these errors would influence the calculation of the pressure gradient force, resulting in substantial, artificial disturbances within the model domain. In addition, an approach to check the initial data was described. Taking advantage of the fact that the geostrophic wind in sigma coordinates should be nondivergent, geopotential height and temperature were used to calculate the pressure gradient force terms and an initial divergence of the geostrophic wind. This approach can be used for comparing different initialization schemes for identical input data. © 1988 Advances in Atmospheric Sciences."
"6603146916;6701469619;","Estimating lower tropospheric vertical motion from surface pressure and pressure tendency data alone",1988,"10.1175/1520-0493(1988)116<0795:ELTVMF>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024192656&doi=10.1175%2f1520-0493%281988%29116%3c0795%3aELTVMF%3e2.0.CO%3b2&partnerID=40&md5=e5cf09e188c34ec5a6cf04022f4bb7c6","In this paper a method is proposed which estimates vertical motion up to about 600 mb using only sea level pressure and pressure tendency data. The general approach is to integrate the continuity equation upward from the top of the planetary boundary layer where the vertical motion can, in theory, be estimated from surface data using simple Ekman theory. The free atmosphere divergence is then estimated by interpolating linearly from its surface quasi-geostrophic value, calculated through the quasi-geostrophic vorticity equation evaluated using surface pressure and pressure tendency data, and a zero value at the assumed level of nondivergence taken to be in the middle of the troposphere. As an example, the method was applied and partially tested in an atmosphere simulated by a primitive equations forecast model. -from Authors"
"24788208900;6503974564;57062902800;24788978000;","The effects of the Qinghai-Xizang Plateau on the mean summer circulation over east Asia",1986,"10.1007/BF02680046","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649153773&doi=10.1007%2fBF02680046&partnerID=40&md5=a28b143ae85c88da51b7ea6675bb8425","Four numerical experiments of simulation have been conducted in this paper by the use of a five-layer primitive equation numerical model with incorporated pressure-sigma vertical coordinate system. The initial fields are taken from the July zonal mean data of many years, while the heat sources and sinks are ideally specified according to the mean heating field over the East Asia calculated from the real data of July, 1979. On the basis of simulated results of temperature and geopotential height patterns we emphatically discuss the effects of the topography and the heating of the Qinghai-Xizang Platcau. From the analyses in this paper, it appears that the heating over the Bengal region makes a larger contribution to the middle and the south branches of the monsoon cell and is also the main cause for the existence of the southerly channel to the east of the Plateau, for the break of the subtropical anticyclone belt below the 500 hPa level and for the formation of the summer Asian anticyclone at the 300 hPa level, while the heating over the Plateau makes a larger contribution to the Plateau monsoon cell and to the anticyclone at the 100 hPa. © 1986 Advances in Atmospheric Sciences."
"7409521185;7409535441;7409589124;","A numerical experiment of the monsoon circulation influenced by the atmospheric heat source and its medium-range oscillation.",1986,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0022855816&partnerID=40&md5=4603e2f3173d34c90299266fb7d819d6","In this paper, a two-dimensional five-layer primitive equation (P.E.) model is used for numerical experiment with regard to the monsoon circulation influenced by the atmospheric heat sources and their medium-range oscillation. It is concluded that both the single heating source and the double heating centers can excite a monsoon circulation or a Walker circulation, that the change of vertical heating profile can influence the thickness of the monsoon cell, that the cooling sources over the Arabian Peninsula and the Mid-Pacific play an important role in forming a monsoon circulation, that the heating sources over the Bay of Bengal and the South China Sea and its medium-range oscillation are the main mechanism forming the monsoon circulation, and that a strengthened source might intensify a monsoon circulation while reducing its extent, conversely, the results would be opposite, so the effects of the two heat centers interact with each other.-Authors"
"56317807700;","Numerical experiment of six-level implicit primitive model",1985,"10.1007/BF03179750","https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956560889&doi=10.1007%2fBF03179750&partnerID=40&md5=ef10153ebc395128526ec8179aee26f4","In this paper, a numerical test is carried out by using a six-level implicit primitive equation model defined in a π coordinate. The model equations are solved with nonlinear iterated method, yielding fairly good results. However, it is time-consuming to solve the model with iterated method. Thus, this model is restored to the advective scheme and solved by means of a split method. Several actual examples are forecasted, which have yielded good results. © 1985 Advances in Atmospheric Sciences."
"6602920335;","Numerical studies of frontal dynamics.",1985,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-85040856806&partnerID=40&md5=d052dbc099fb84eb32ca65edd64e0910","Frontogenetical mechanisms of confluence (stretching deformation) and horizontal shear (shearing deformation) were incorporated into a mathematically consistent 2-dimensional formulation suitable for a cross-section primitive equation (PE) model. Accounting for the structural differences between surface cold and warm fronts and the development of a realistic tropopause fold during upper-level frontogenesis are addressed. The geostrophic adjustment characteristics of a statically stable rotating, compressible atmosphere to initial imbalance in frontal systems was determined. The outcome of this particular effort should serve as a basis for interpreting the results of initialization procedures developed for mesoscale PE models with sufficient resolution to resolve frontal-scale processes. Ageostrophic circulations in the PE frontal model is diagnosed. The applicability of filtered diagnostic approaches based upon the quasi and semigeostrophic theories, and a formulation based on the unfiltered primitive equations, will be tested using the model as a data source. The three diagnostic approaches are valuable for interpretation of the first objective, and the unfiltered version is useful in the analysis of the details of the geostrophic adjustment process in the PE model initialization experiments planned under the second objective.-from STAR, 23(15), 1985"
"24785881500;16744853100;24782844500;57215948671;24789725000;","An operational 5-layer primitive equation model for northern hemisphere prediction",1984,"10.1007/BF02678134","https://www.scopus.com/inward/record.uri?eid=2-s2.0-51649157753&doi=10.1007%2fBF02678134&partnerID=40&md5=215c4aa89cd7b68ab9df1ffec24b1a77","A 5-layer primitive equation Northern Hemisphere operational model in a modified σ-coordinate system is developed in BMC, NMB. Finite difference schemes are constructed to conserve the total energy without imposing any constraints on the difference scheme of hydrostatic equation and pressure gradient term. The physical factors of orography, friction, horizontal diffusion and various non-adiabatic heatings are included. The model has been under development since the beginning of 1980, and became operational in September 1981. Preliminary results for selected series of 40 prognosis are summarized and the verifications are encouraging. © 1984 Advances in Atmospheric Sciences."
"7401571939;","Energy analysis of a recent approximation to the atmospheric primitive equations",1984,"10.1111/j.1600-0870.1984.tb00260.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84977732831&doi=10.1111%2fj.1600-0870.1984.tb00260.x&partnerID=40&md5=f4630dbaeefb27796b06cdc47d3b7637","An approximation to the thermodynamic equation was introduced by Holton which was motivated by an energy principle involving a quadratic expression in temperature deviation, which he identified as available potential energy. The approximation consists of neglecting the component of adiabatic warming/cooling due to the temporally and horizontally variable part of the specific volume on a constant pressure surface, WKT*. If the approximation is made, the system lacks a total energy principle involving either total potential energy or available potential energy (except in one special case). Although this approximate form of the primitive equations does not cause substantial error in a numerical simulation of the annual cycle of a zonally‐symmetric circulation, there appears to be no significant advantage to its application. Use of the standard set of primitive equations is suggested. 1984 Blackwell Munksgaard"
"15031624900;","A numerical study of climatic oscillations using a coupled atmosphere-ocean primitive equation model.",1984,"10.1175/1520-0469(1984)041<0746:ANSOCO>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021640906&doi=10.1175%2f1520-0469%281984%29041%3c0746%3aANSOCO%3e2.0.CO%3b2&partnerID=40&md5=516bd6177a15842b8a233c09baac4c9a","In the lower layer of the atmosphere and the mixed layer of the ocean within the zonal belt of midlatitudes disturbances which are caused by the boundaries of the ocean become large-scale disturbances in both atmosphere and ocean, and the monthly mean anomalies of these large-scale disturbances lock together to produce a very stable coupled system to move westwards at a speed of 5000 km per year. The periods of climatic oscillations are about two years. The initial mixed-layer sea temperature anomaly in the equatorial region cannot last a long time but can influence the time evolution of monthly mean climatic anomalies in midlatitudes.-from Author"
"6508015013;","Horizontal energy propagation in a baroclinic atmosphere with meridional and zonal structure.",1984,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021557657&partnerID=40&md5=a9517ffecea80810b109076d1e41c6f2","A baroclinic model was developed. The model is linear, steady state, baroclinic (2 level) and based on the primitive equations. The thermal forcing is prescribed at the intermediate vertical level.-from STAR, 22(12), 1984"
"57196542737;","Climate sensitivity with a seasonal cycle energy balance model ( icecap).",1984,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021549247&partnerID=40&md5=6c7f5d370a6af4dc68a490beb9c3842f","The sensitivity of climate which may have a local maximum as the ice cap passes through a midlatitude region where the atmosphere's transport efficiency varies strongly with latitude is examined. This behavior, found in a two level primitive equations climate model forced with annual mean insolation, was reproduced in an energy balance model by making the diffusion coefficient a function of latitude.-from STAR, 22(12), 1984"
"7004427982;6701357023;","Filtering of gravity modes in atmospheric models.",1984,"10.1175/1520-0493(1984)112<0893:FOGMIA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-0021547717&doi=10.1175%2f1520-0493%281984%29112%3c0893%3aFOGMIA%3e2.0.CO%3b2&partnerID=40&md5=43eeb50b93e49046fdb1ee9d85d9bf9c","The impact of gravity modes in atmospheric model predictions is assessed quantitatively by comparing integrations with a normal mode initialized primitive equation model and its corresponding pseudogeostrophic form to document some generally accepted presumptions. Analysis with a linear system yields horizontally scale-dependent differences in the Rossby frequencies derived from the two conditions (initialized and geostrophic) as well as differences in the initial divergence required.-from Authors"
"7409633658;","Solitary internal gravity inertial wave in a stratified atmosphere and nonlinear processes for the formation of squall lines.",1983,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020871299&partnerID=40&md5=12d1bf01f023b7508874c1c68f665ee2","The KdV equation is derived from the 3-D primitive equations for a class of finite amplitude waves in a stratified basic flow. The solitary wave solution is given for a simple case where a constant and uniformly stratified basic flow is confined in a region bounded by solid walls with rectangular cross section. The properties of the solitary wave solution can give a possible explanation for the preferential occurrence of a squall line or storm cell train at the left side of a low level jet and the concurrent fluctuation in the low level jet. -from Author"
"6506096180;6603672935;","USE OF OBJECTIVE ANALYSIS FOR CALCULATING GRADIENTS IN THE LAGRANGIAN METHOD OF INTEGRATION OF PROGNOSTIC EQUATIONS.",1982,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0020306452&partnerID=40&md5=b1d3ffef70fac0cc54fb6a6159e10ab1","Problems related to numerical integration of prognostic equations by the Lagrangian method are discussed. It is suggested to use objective analysis procedures when approximating gradients not included in the total derivatives. This permits calculation directly over a time-varying irregular grid. Examples of calculations by means of a barotropic model of the atmosphere described by a system of primitive equations are given."
"6507416070;","Pressure wind adjustment relationships during a multilevel primitive equation prediction process using tropical atmospheric data",1979,"10.1007/BF00876066","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250266561&doi=10.1007%2fBF00876066&partnerID=40&md5=c536ea0c4353068d58b083ea407d0421","In numerical weather forecasting process, with primitive equations, the wind and pressure fields mutually adjust to each other until some form of balance is achieved. The type of balance so achieved by the mass and wind fields during the numerical integration of the primitive equations governing atmospheric motions is not known a priori. This is particularly so in the case of tropical regions where the pressure wind adjustment laws prevailing in a tropical atmosphere are not well understood. In this study we perform a systematic investigation of the pressure wind adjustment relations during a numerical integration of the primitive equations governing atmospheric motions in a tropical atmosphere. Therefore, a two-day prediction experiment is carried out using the Florida State University Tropical Prediction (FSU) Model (Krishnamurti, 1969;Krishnamurti, et al. 1973;Kanamitsu, 1975). The 200 mb predicted motion (u, v) and height (z) fields are then extracted at 0, 12, 24, 36 and 48 hours of forecast time. Using these motion (u, v) fields three other 200 mb height (z) fields were computed from the inverse nonlinear, linear and quasigeostrophic balance equations. Each of these three diagnostic heights for the 200 mb pressure surface were compared with the respective 200 mb heights obtained from the Florida State University Tropical Preciction Model. The comparison is done by computing the root-mean-square differences between the predicted 200 mb height fields and each of the three 200 mb heights obtained from the inverse non-linear, linear and quasigeostrophic balance equations. The results show that the root-meansquare differences between the z fields from the FSU model and those obtained from the non-linear and linear balance equations lie within the ranges 23 to 44 and 25 to 50 metres respectively. The root-mean-square differences between the predicted heights and the heights computed from the quasigeostrophic balance equation lie in the range 54 to 62 metres. These root-mean-square differences are of significant magnitude since large-scale disturbances in the tropical atmosphere are associated with rather small pressure changes. The variations of these root-mean-square differences as one moves from one forecast time to another exhibit no clear increasing or decreasing trend. In fact the variations appear somewhat random. This rather unsystematic time variation of the root-mean-square differences is a manifestation of the constant changes of the physics in the model as different weather systems evolve in the course of the forecasting process. It seems therefore that the pressure-wind adjustments that take place during a numerical integration of the model equations are of complex nature and cannot simply be approximated by simple diagnostic relations like the ones used in this study. © 1979 Birkhäuser Verlag."
"16511301800;","Dynamic initialization for barotropic flow crossing a barrier",1976,"10.1007/BF00875653","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250385834&doi=10.1007%2fBF00875653&partnerID=40&md5=4930b4005a61014faaa5e0174767fca0","A method to obtain balanced initial state in the presence of mountains is presented. Using a prescribed initial state the primitive equations are iterated forward and backward about the initial time, using an Euler-backward time integration scheme. During this iteration the mountains are built-up steadily. The method is tested against a steady-state analytical solution of the non-linear equations of the homogeneous atmosphere. The results of this test demonstrate that the method is capable of generating the theoretical steady-state numerical solution with a good degree of accuracy. © 1976 Birkhäuser Verlag."
"57192343476;7005471123;57192748880;","A Preliminary Report on Numerical Simulation of Synoptic Scale Atmospheric Motion and the Associated Sen Sible and Latent Heat Supplies from Sea Surface During the AMTEX '74 period",1974,"10.2467/mripapers1950.25.4_233","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85024269451&doi=10.2467%2fmripapers1950.25.4_233&partnerID=40&md5=3765bd56f07b7804d4dd3cbbc661045b","Using an operational numerical weather prediction model at the Japan Meteorological Agency, i.e., a 6-level, fine-mesh, limited area primitive equation model***, a preliminary study was made with regard to the numerical simulation of synoptic scale atmospheric motion during the AMTEX '74 period. As the first phase of the investigation, three cases are taken up for the case study. The first case (Case 1) shows the passage of a moving anticyclone and a cyclone over the East China Sea. The second case (Case 2) is the case of a front passage in the Okinawa area. The third case (Case 3) is featured by the predominant coverage of the whole AMTEX area by a cold air mass. Calculated patterns of the three cases show, in general, good agreement with observed patterns. The second phase of the investigation elaborates comparison of the synoptic scale sensible and latent heat supplies from the sea surface in the model atmosphere in the cases mentioned above. The bulk aerodynamic method is employed for the estimatin of the sensible and latent heat supplies which are quite sensitive to the synoptic situation. The model atmosphere also well simulates the day-to-day variation of the supplies. The hour-to-hour variation in the model atmosphere, however, is not moderate as in the case of the real atmosphere, but shows a sharp decrease in the intensity as time advances. This may be a deficiency of the model in responding to external heating. The calculated total quantity of heat supplies during 24 hours compares favorably with the preliminary calculation of heat supplies from the AMTEX '74 observation by J. KONDO (1974). A comparison is made between the 24-hour forecast with the normal sea 'surface temperature and that with the 8-day mean sea surface temperature of 87-28 February 1974. No appreciable difference is seen in prognostic patterns of meteorological variables such as pressure, wind velocity, temperature, humidity and quantity of precipitation as far as the 24-hour forecast is concerned. However, the distribution of sensible and latent heat supplies shows a significant discrepancy between the two cases. © 1974, Japan Meteorological Agency. All rights reserved."
"7006033615;","SPECTRAL REPRESENTATION OF HORIZONTAL WIND IN NUMERICAL MODELS OF THE ATMOSPHERE.",1974,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-0346398343&partnerID=40&md5=0c4f0affa211461f030f5f1ab25a2b27","USE OF THE PRIMITIVE EQUATIONS IN SPECTRAL MODELS OF THE ATMOSPHERE RAISES CERTAIN QUESTIONS ABOUT THE REPRESENTATION OF THE HORIZONTAL COMPONENTS OF VELOCITY THEREIN.A BARATROPIC MODEL IS CONSTRUCTED AND INTEGRATED USING TWO TYPES OF VELOCITY REPRESENTATION.IN THE FIRST, (U,V) ARE EXPANDED DIRECTLY IN SPHERICAL HARMONICS WHILE THE SECOND REPRESENTS (U COSGQ, V COSGQ) IN LIKE MANNER, WHERE GQ IS LATITUDE.THESE INTEGRATIONS ARE COMPARED AND IT IS CONCLUDED THAT THE DIRECT REPRESENTATION OF (U,V) IS AN ALLOWABLE PROCEDURE.(A)"
"6603354063;55454781100;","A note on the dependence of atmospheric predictability on baroclinic development",1971,"10.1002/qj.49709741207","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981650808&doi=10.1002%2fqj.49709741207&partnerID=40&md5=bfc184529944283ee0a9085581072ac2","A two‐level, quasi‐geostrophic model, described by Everson and Davies (1970), is used to study the dependence of duration of predictability (as defined by, e.g., Charney et al. 1966) on the phase, at some initial time in the integration, of global scale baroclinic development (expressed in the model in terms of fluctuations in eddy kinetic energy, K'). Using firstly an invariable subgrid scale coefficient in a control run of 120 days, sinusoidal perturbations, wave length approximately 6,000 km, of the geopotential heights are inserted at all the grid points at (a) day 72, corresponding to a maximum in model K', and (b) day 84, corresponding to a minimum in model K'. The consequent ‘perturbed’ integrations are compared to the control values by taking the r.m.s. of the difference in the 500 mb calculated temperature distributions, and determining the time taken for this to increase to the ‘persistence’ value, i.e. the maximum r.m.s. difference between two randomly selected model states. The doubling time of error in (a) was seen to be 12 days leading to a model predictability of 24 days, and in (b) it was seen to be 17 days, leading to a predictability of 34 days: these values are related to an initial perturbation amplitude of 1°C. These experiments were then repeated using a variable subgrid scale coefficient, depending on grid scale horizontal temperature gradient as described by Everson and Davies (1970). The results were; (a) working from a day of maximum K', the doubling time of error was reduced to 8 days, approaching the value obtained by primitive equation numerical models and corresponding to a predictability of 16 days; (b) working from a day of minimum K', the doubling time of error was 13 days, corresponding to a predictability of 26 days. The results in both cases show that predictability, as calculated from some initial phase of baroclinic development, is 50 per cent higher as measured from a maximum in K'compared with a minimum in K'. It also drops sharply with increase in the degree of model sophistication (expressed in the system discussed in this paper as variability of the subgrid scale coefficient). Copyright © 1971 Royal Meteorological Society"
"57214434210;","A numerical experiment to predict a mean meridional pressure profile ab initio by Lagrangian integration",1968,"10.1007/BF02247080","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250528562&doi=10.1007%2fBF02247080&partnerID=40&md5=e6a870bd19ed9930e4c137baf7d62de3","The question is posed: Consider an atmosphere initially at rest with a uniform mean sea level pressure field but possessing a mean baroclinicity defined by that which is observed during a selected month. How would this atmosphere readjust mass as a function of time and latitude as exhibited by the developing field of surface pressure if the initial pressure gradient field was maintained at all heights as input data and if baroclinic changes were ignored? To solve this question analytical solutions of the equations of motion were found in Lagrangian form. The equations are subjected to hourly iteration for successive values of the Coriolis parameter and the pressure gradient acceleration for a profile of pressure gradients averaged around parallels of latitude. Omega Values of the vertical velocity (ω) are computed from the equation of continuity for six layers and integrated with height from the surface to 100 millibars. The omega values are then averaged over ten degree belts of latitude and plotted as a function of time and latitude. Although the numerical values are much larger than those which would be expected to develop in nature or in a primitive equation model which incorporated feedback at the proper time interval of integration the patterns of the pressure profile which develop resemble those which exist in January and July in a most striking manner. © 1968 Springer-Verlag."