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."
"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.
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."
"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."
"36678135100;7003637266;","A semi-implicit non-hydrostatic dynamical kernel using finite elements in the vertical discretization",2012,"10.1002/qj.952","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84859772046&doi=10.1002%2fqj.952&partnerID=40&md5=e21df961a7535d0759189e13303fe36e","This work is a first step in the direction of implementing a high-order finite-element discretization in the vertical in the non-hydrostatic version of the HARMONIE model. The present dynamical core of the HARMONIE model is shared with the ECMWF and the ALADIN models and uses a horizontal spectral discretization and a semi-implicit semi-Lagrangian time stepping scheme, all of which are maintained in this work. Trying to implement a finite-element discretization in the non-hydrostatic version of the HARMONIE model has been found to be very difficult due to the set of prognostic variables used and the mass-based vertical coordinate. A different set of prognostic variables and a hybrid vertical coordinate based on height are tested here on a vertical slice non-hydrostatic kernel. A stability analysis of the linear model has been done. To evaluate the model stability and accuracy, a set of test cases from the literature are presented in the linear and nonlinear regimes, with and without orography. An iterative centred-implicit scheme can be applied to avoid instability related to steep orography, although this reduces the efficiency of the model. The novel aspects with respect to existing non-hydrostatic model kernels are the use of cubic finite elements in the vertical discretization, the use of a height-based vertical coordinate in conjunction with a spectral discretization in the horizontal, and the coordinate-independent formulation of each element of the model including the semi-Lagrangian advection. © 2011 Royal Meteorological Society."
"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)."
"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."
"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."
"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."
"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."
"56973805300;7005561589;","Why do similar patterns of tropical convection yield extratropical circulation anomalies of opposite sign?",2017,"10.1175/JAS-D-16-0067.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011661518&doi=10.1175%2fJAS-D-16-0067.1&partnerID=40&md5=22b03ff730fd01281f2aaa67d9d5326d","Tropical precipitation anomalies associated with El Niño and Madden-Julian oscillation (MJO) phase 1 (La Niña and MJO phase 5) are characterized by a tripole, with positive (negative) centers over the Indian Ocean and central Pacific and a negative (positive) center over the warm pool region. However, their midlatitude circulation responses over the North Pacific and North America tend to be of opposite sign. To investigate these differences in the extratropical response to tropical convection, the dynamical core of a climate model is used, with boreal winter climatology as the initial flow. The model is run using the full heating field for the above four cases, and with heating restricted to each of seven small domains located near or over the equator, to investigate which convective anomalies may be responsible for the different extratropical responses. An analogous observational study is also performed. For both studies, it is found that, despite having a similar tropical convective anomaly spatial pattern, the extratropical response to El Niño and MJO phase 1 (La Niña and MJO phase 5) is quite different. Most notably, responses with opposite-signed upper-tropospheric geopotential height anomalies are found over the eastern North Pacific, northwestern North America, and the southeastern United States. The extratropical response for each convective case most closely resembles that for the domain associated with the largest-amplitude precipitation anomaly: the central equatorial Pacific for El Niño and La Niña and the warm pool region for MJO phases 1 and 5. © 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."
"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."
"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."
"7406354393;7005087624;7103211168;","Impact of a semi-Lagrangian and an Eulerian dynamical core on climate simulations",1997,"10.1175/1520-0442(1997)010<2374:IOASLA>2.0.CO;2","https://www.scopus.com/inward/record.uri?eid=2-s2.0-5844382008&doi=10.1175%2f1520-0442%281997%29010%3c2374%3aIOASLA%3e2.0.CO%3b2&partnerID=40&md5=cfa5866fd91d8c5beff7be92a9b44c5b","To assess the impact of dynamical formulation on climate simulations, a semi-Lagrangian and an Eulerian dynamical core have been used for 5-yr climate simulations with the same physical parameterizations. The comparison of the climate simulations is focused on various eddy statistics (the study of time-mean states from the simulations has been published in a previous paper). Significant differences between the two simulations are evident. Generally, the stationary eddy variances are stronger in the semi-Lagrangian simulation while the transient eddy variances are stronger in the Eulerian simulation. Compared to the data assimilated by the Goddard Earth Observing System data assimilation system, the semi-Lagrangian simulation is closer to the assimilation in many aspects than the Eulerian simulation, even though the Eulerian model was used in the data assimilation. The paper shows that rather than corrupting the ability to diagnose model performance with a parallel data assimilation, quantitative rigor can be advanced because the model environment is more controlled. The two dynamical cores have been run for the idealized Held-Suarez tests to help understand the differences found in the climate simulations. The eddy statistics from the Held-Suarez tests are weaker and more diffused in the semi-Lagrangian than the Eulerian core. The transformed Eulerian mean diagnostics reveal that less wave activity propagates from the lower and middle troposphere into the upper troposphere in the semi-Lagrangian core. The residual circulation driven by eddy forcing is weaker in the semi-Lagrangian core than in the Eulerian core. Consequently, the semi-Lagrangian simulation is closer to the radiative equilibrium state than the Eulerian simulation. These diagnostics show that the different treatment of small-scale processes in the model (e.g., diffusion) profoundly impacts the simulation of the general circulation."
"56094958100;57203084853;55829903800;","A barotropic mechanism for the response of Jet Stream variability to arctic amplification and sea ice loss",2018,"10.1175/JCLI-D-17-0778.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052831498&doi=10.1175%2fJCLI-D-17-0778.1&partnerID=40&md5=9f023619d82f5b26f10cba264044d7eb","Previous studies have found that the most consistent response of the eddy-driven jet to sea ice loss and Arctic amplification in fully coupled general circulation models (GCMs) is a broad region of anomalous easterlies on the poleward flank. In this study, a similar response is noted in a dry dynamical core GCM with imposed surface heating at the pole, and it is shown that in both a fully coupled GCM's North Atlantic basin and the dry dynamical core, the anomalous easterlies cause an asymmetrical narrowing of the jet on the poleward flank of the climatological jet. A suite of barotropic model simulations run with polar forcing shows decreased jet positional variability consistent with a narrowing of the jet profile, and it is proposed that this narrowing decreases the distance Rossby waves can propagate away from the jet core, which drives changes in jet variability. Since Rossby wave propagation and dissipation is intrinsic to the development and maintenance of the eddy-driven jet, and is tightly coupled to a jet's variability, this acts as a meridional constraint on waves' ability to propagate outside of the jet core, leading to the decreased variability in zonal-mean jet position. The results from all three models demonstrates that this relationship is present across a model hierarchy. © 2018 American Meteorological Society."
"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."
"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."
"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."
"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."
"6603845748;","Is interleaving in the Agulhas Current driven by near-inertial velocity perturbations?",2007,"10.1175/JPO3040.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-34249108866&doi=10.1175%2fJPO3040.1&partnerID=40&md5=852e4c9fa7ff1e06ef723f5919e36e69","Recent observations taken at a number of latitudes in the Agulhas Current reveal that the water mass structure on either side of its dynamical core is distinctly different. Moreover, interleaving of these distinct water masses is observed at over 80% of the stations occupied in the current, particularly within the subsurface density layer between tropical surface water and subtropical surface water masses, and within the intermediate layer between the Antarctic Intermediate Water and Red Sea water masses. Direct velocity measurements allow for a comparison between the characteristic vertical length scales of the Agulhas intrusions and those of velocity perturbations found throughout the current. It is found that the interleaving scales match those of the velocity perturbations, which are manifest as high-wavenumber vertical shear layers and are identified as near-inertial oscillations. Furthermore, the properties of the intrusions indicate that double diffusion is not an important process in their development: they are generally not associated with a density anomaly, their slope and thickness fall outside the predicted maxima for instability, and a strong horizontal shear field acts to separate water parcels more quickly than intrusions would be able to grow by double-diffusive processes. Instead, the position, thickness, and slope of Agulhas intrusions relative to the background salinity and density field suggest that they are forced by rotating inertial velocities, with subsequent growth possibly driven by small-scale baroclinic instabilities. However, not all the evidence points conclusively toward advectively driven intrusions. For instance, there is a discrepancy between the observed salinity anomaly amplitude and the predicted inertial displacement given the background salinity gradient, which deserves further examination. Hence, there is a future need for more pointed observations and perhaps the development of an analytical or numerical model to understand the exact nature of Agulhas intrusions. © 2007 American 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.
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.
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."
"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."
"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."
"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."
"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)."
"6602960153;7403362745;19337661700;","Exploiting an ensemble of regional climate models to provide robust estimates of projected changes in monthly temperature and precipitation probability distribution functions",2009,"10.1111/j.1600-0870.2008.00374.x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-58049121762&doi=10.1111%2fj.1600-0870.2008.00374.x&partnerID=40&md5=52de9de95632cb13c4f458133ea9f219","Regional climate models (RCMs) are dynamical downscaling tools aimed to improve the modelling of local physical processes. Ensembles of RCMs are widely used to improve the coarse-grain estimates of global climate models (GCMs) since the use of several RCMs helps to palliate uncertainties arising from different dynamical cores and numerical schemes methods. In this paper, we analyse the differences and similarities in the climate change response for an ensemble of heterogeneous RCMs forced by one GCM (HadAM3H), and one emissions scenario (IPCC's SRES-A2 scenario). As a difference with previous approaches using PRUDENCE database, the statistical description of climate characteristics is made through the spatial and temporal aggregation of the RCMs outputs into probability distribution functions (PDF) of monthly values. This procedure is a complementary approach to conventional seasonal analyses. Our results provide new, stronger evidence on expected marked regional differences in Europe in the A2 scenario in terms of precipitation and temperature changes. While we found an overall increase in the mean temperature and extreme values, we also found mixed regional differences for precipitation. © Journal compilation © 2009 Blackwell Munksgaard."
"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."
"6603841948;55973787900;23485724500;7103030382;16040423200;25641111100;8278514200;55952803900;","FESOM-C v.2: Coastal dynamics on hybrid unstructured meshes",2019,"10.5194/gmd-12-1009-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85063284390&doi=10.5194%2fgmd-12-1009-2019&partnerID=40&md5=488e38cb6f51903f024dc04ce40e872a","We describe FESOM-C, the coastal branch of the Finite-volumE Sea ice-Ocean Model (FESOM2), which shares with FESOM2 many numerical aspects, in particular its finite-volume cell-vertex discretization. Its dynamical core differs in the implementation of time stepping, the use of a terrain-following vertical coordinate, and the formulation for hybrid meshes composed of triangles and quads. The first two distinctions were critical for coding FESOM-C as an independent branch. The hybrid mesh capability improves numerical efficiency, since quadrilateral cells have fewer edges than triangular cells. They do not suffer from spurious inertial modes of the triangular cell-vertex discretization and need less dissipation. The hybrid mesh capability allows one to use quasi-quadrilateral unstructured meshes, with triangular cells included only to join quadrilateral patches of different resolution or instead of strongly deformed quadrilateral cells. The description of the model numerical part is complemented by test cases illustrating the model performance. © 2019 Author(s)."
"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."
"55747696500;7201972249;57195587405;11939929300;57208455668;","2017 Atlantic Hurricane Forecasts from a high-resolution version of the GFDL fvGFS Model: Evaluation of track, intensity, and structure",2018,"10.1175/WAF-D-18-0056.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062151931&doi=10.1175%2fWAF-D-18-0056.1&partnerID=40&md5=c961a909cb7e9a252ef3fcfeb3dba0c1","The 2017 Atlantic hurricane season had several high-impact tropical cyclones (TCs), including multiple cases of rapid intensification (RI). A high-resolution nested version of the GFDL finite-volume dynamical core (FV3) with GFS physics (fvGFS) model (HifvGFS) was used to conduct hindcasts of all Atlantic TCs between 7 August and 15 October. HifvGFS showed promising track forecast performance, with similar error patterns and skill compared to the operational GFS and HWRF models. Some of the larger track forecast errors were associated with the erratic tracks of TCs Jose and Lee.Acase study of Hurricane Maria found that although the track forecasts were generally skillful, a right-of-track bias was noted in some cases associated with initialization and prediction of ridging north of the storm. The intensity forecasts showed large improvement over the GFS and global fvGFS models but were somewhat less skillful than HWRF. The largest negative intensity forecast errors were associated with the RI of TCs Irma, Lee, and Maria, while the largest positive errors were found with recurving cases that were generally weakening. The structure forecasts were also compared with observations, and HifvGFS was found to generally have wind radii larger than the observations. Detailed examination of the forecasts of Hurricanes Harvey and Maria showed that HifvGFS was able to predict the structural evolution leading to RI in some cases but was not as skillful with other RI cases. One case study of Maria suggested that the inclusion of ocean coupling could significantly reduce the positive bias seen during and after recurvature. © 2018 American Meteorological Society."
"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."
"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."
"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."
"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."
"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"
"57188966058;7202048112;57111001300;7406589460;6506328135;36908840200;55731303900;","Exploring the effects of a nonhydrostatic dynamical core in high-resolution aquaplanet simulations",2017,"10.1002/2016JD025287","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016310152&doi=10.1002%2f2016JD025287&partnerID=40&md5=6c783661bb7ee6f825d7071ff674baf1","This study explores the impact of a nonhydrostatic dynamical core in high-resolution regional climate simulations using an aquaplanet framework. The Weather Research and Forecasting (WRF) model is used to conduct simulations with both hydrostatic (H) and nonhydrostatic (NH) solvers at horizontal grid spacings (Δx) of 36, 12, and 4 km. The differences between the H and NH simulated precipitation (ΔP) are notable even at Δx = 12 km in the intertropical convergence zone and the transition region to the drier subtropics. At gray zone grid spacing (12 km and 4 km) over the tropics, ΔP is sensitive to whether a cumulus parameterization scheme is used or not. With an idealized Witch of Agnesi land mountain, differences in the precipitation and circulation (vertical velocity) between the H and NH simulations are significant even at Δx = 36 km in the tropics due largely to the strong feedbacks related to moist processes. The differences increase as the model grid spacing and mountain half width (a) are reduced, accompanied by a shift toward a more nonhydrostatic flow regime at a = 24 km. Latent heat release drastically enhances the differences between the NH and H simulations and extends the effect of nonhydrostatic dynamics to a broader region over the mountain and downstream over the tropics. Overall, differences exist between H and NH simulations even at resolutions between 12 and 36 km, but the differences are sensitive to the representations of moist physics and other features such as horizontal diffusion used in the WRF model. © 2017. American Geophysical Union. All Rights Reserved."
"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."
"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."
"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."
"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."
"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."
"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."
"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."
"56991181200;12767129100;6701350155;7004309320;","A skill assessment of the biogeochemical model REcoM2 coupled to the finite element sea ice-ocean model (FESOM 1.3)",2014,"10.5194/gmd-7-2769-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949134636&doi=10.5194%2fgmd-7-2769-2014&partnerID=40&md5=0749ee0b74447943d14d975aecb77271","In coupled biogeochmical-ocean models, the choice of numerical schemes in the ocean circulation component can have a large influence on the distribution of the biological tracers. Biogeochemical models are traditionally coupled to ocean general circulation models (OGCMs), which are based on dynamical cores employing quasiregular meshes, and therefore utilize limited spatial resolution in a global setting. An alternative approach is to use an unstructured-mesh ocean model, which allows variable mesh resolution. Here, we present initial results of a coupling between the Finite Element Sea Ice-Ocean Model (FESOM) and the biogeochemical model REcoM2 (Regulated Ecosystem Model 2), with special focus on the Southern Ocean. Surface fields of nutrients, chlorophyll a and net primary production (NPP) were compared to available data sets with a focus on spatial distribution and seasonal cycle. The model produces realistic spatial distributions, especially regarding NPP and chlorophyll a, whereas the iron concentration becomes too low in the Pacific Ocean. The modelled NPP is 32.5 Pg C yr-1 and the export production 6.1 Pg C yr-1, which is lower than satellite-based estimates, mainly due to excessive iron limitation in the Pacific along with too little coastal production. The model performs well in the Southern Ocean, though the assessment here is hindered by the lower availability of observations. The modelled NPP is 3.1 Pg C yr-1 in the Southern Ocean and the export production 1.1 Pg C yr-1. All in all, the combination of a circulation model on an unstructured grid with a biogeochemical-ocean model shows similar performance to other models at non-eddy-permitting resolution. It is well suited for studies of the Southern Ocean, but on the global scale deficiencies in the Pacific Ocean would have to be taken into account. © Author(s) 2014."
"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."
"6603218374;","Design of a dynamical core based on the nonhydrostatic ""unified system"" of equations",2014,"10.1175/MWR-D-13-00187.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84892467486&doi=10.1175%2fMWR-D-13-00187.1&partnerID=40&md5=23d8e4aa2428a1e4c2808a0470659687","This paper presents the design of a dry dynamical core based on the nonhydrostatic ''unified system'' of equations. The unified system filters vertically propagating acoustic waves. The dynamical core predicts the potential temperature and horizontal momentum. It uses the predicted potential temperature to determine the quasi-hydrostatic components of the Exner pressure and density. The continuity equation is diagnostic (and used to determine the verticalmass flux) because the time derivative of the quasi-hydrostatic density is obtained fromthe predicted potential temperature. The nonhydrostatic component of the Exner pressure is obtained from an elliptic equation. The main focus of this paper is on the integration procedure used with this unique dynamical core. In the implementation described in this paper, height is used as the vertical coordinate, and the equations are vertically discretized on a Lorenz-type grid. Cartesian horizontal coordinates are used along with an Arakawa C grid. A detailed description of the discrete equations is presented in the supplementary material, along with the rationale behind the decisions made during the discretization process. Only a short description is given here. To demonstrate that the model is capable of simulating a wide range of dynamical scales, the results from cyclone- and cloud-scale simulations are presented. The solutions obtained for the selected cloud-scale simulations are compared to those from a fully compressible, anelastic, and pseudo-incompressible models that (as far as possible) uses the same schemes used in the unified dynamical core. The results show that the unified dynamical core performs reasonably well in all these experiments. © 2014 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."
"6602418877;57197636789;57210010133;24503245200;6506144245;","Toward very high horizontal resolution NWP over the alps: Influence of increasing model resolution on the flow pattern",2011,"10.2478/s11600-011-0054-9","https://www.scopus.com/inward/record.uri?eid=2-s2.0-80053569007&doi=10.2478%2fs11600-011-0054-9&partnerID=40&md5=d2daec02ac92ac6fd409dafe65f2dedb","The increasing resolution of contemporary regional numerical weather prediction (NWP) models, reaching horizontal grid sizes of O(1 km), requires robust and reliable dynamical cores, working well beyond the approximation of quasi-horizontal flows. That stimulates an interest in an application for NWP purposes of dynamical cores based on the anelastic, or - more generally - sound-proof flow equations, and characterized by appropriate robustness and reliability. The paper presents results from testing the dynamical core of EULAG, the anelastic research model for multi-scale flows, as a prospective NWP dynamical core. The model simulates the semi-realistic frictionless and adiabatic flow over realistic steep Alpine topographies, employing horizontal grid sizes of 2.2, 1.1, and 0.55 km. The paper demonstrates not only the numerical robustness of EULAG, but also studies the influence of the varying horizontal resolution on the simulated flow. Results show that the increased horizontal resolution increases orographic drag on the flow. While the general flow pattern remains the same, increased resolution influences the flow on scales from hundreds of kilometers to meso-gamma scales. The differences are especially apparent in the near-surface layer of 1.5 to 3 km deep, and in the distribution and amplitudes of the orographically-induced gravity waves. © 2011 Versita Warsaw and Springer-Verlag Wien."
"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."
"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."
"8870155900;57030797300;9244992800;36637539100;","Lower-Stratospheric Control of the Frequency of Sudden Stratospheric Warming Events",2018,"10.1002/2017JD027648","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85044500795&doi=10.1002%2f2017JD027648&partnerID=40&md5=30f9a3b39b233f0f6f00ff54f218e53d","The sensitivity of stratospheric polar vortex variability to the basic-state stratospheric temperature profile is investigated by performing a parameter sweep experiment with a dry dynamical core general circulation model where the equilibrium temperature profiles in the polar lower and upper stratosphere are systematically varied. It is found that stratospheric variability is more sensitive to the temperature distribution in the lower stratosphere than in the upper stratosphere. In particular, a cold lower stratosphere favors a strong time-mean polar vortex with a large daily variability, promoting frequent sudden stratospheric warming events in the model runs forced with both wavenumber-1 and wavenumber-2 topographies. This sensitivity is explained by the control exerted by the lower-stratospheric basic state onto fluxes of planetary-scale wave activity from the troposphere to the stratosphere, confirming that the lower stratosphere can act like a valve for the upward propagation of wave activity. It is further shown that with optimal model parameters, stratospheric polar vortex climatology and variability mimicking Southern and Northern Hemisphere conditions are obtained with both wavenumber-1 and wavenumber-2 topographies. ©2018. American Geophysical Union. All Rights Reserved."
"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."
"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."
"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."
"6602131529;26536512300;6603177647;","Numerical simulations of internal solitary waves interacting with uniform slopes using an adaptive model",2009,"10.1016/j.ocemod.2009.05.008","https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650609831&doi=10.1016%2fj.ocemod.2009.05.008&partnerID=40&md5=f546e06f209a6627464c2ef5abeafbaa","Two-dimensional, non-linear, Boussinesq, non-hydrostatic simulations of internal solitary waves breaking and running up uniform slopes have been performed using an adaptive, finite volume fluid code ""Gerris"". It is demonstrated that the Gerris dynamical core performs well in this specific but important geophysical context. The ""semi-structured"" nature of Gerris is exploited to enhance model resolution along the slope where wave breaking and run-up occur. Comparison with laboratory experiments reveals that the generation of single and multiple turbulent surges (""boluses"") as a function of slope angle is consistently reproduced by the model, comparable with observations and previous numerical simulations, suggesting aspects of the dynamical energy transfers are being represented by the model in two dimensions. Adaptivity is used to explore model convergence of the wave breaking dynamics, and it is shown that significant cpu memory and time savings are possible with adaptivity. © 2009 Elsevier Ltd. All rights reserved."
"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."
"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 frictionalmodel 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."
"14020255000;37861012100;35316923500;7005565819;54894233700;56893485300;57132461500;7006030430;13407050600;6503890088;57205299261;7006429360;11939929300;8382949200;57205302128;35812541300;7402627827;57203579757;57193856591;56842269600;","Systematic comparison of convection-allowing models during the 2017 NOAA HWT spring forecasting experiment",2019,"10.1175/WAF-D-19-0056.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85074169053&doi=10.1175%2fWAF-D-19-0056.1&partnerID=40&md5=ee28bf88bdd919e43a92961f4feeec20","The 2016–18 NOAA Hazardous Weather Testbed (HWT) Spring Forecasting Experiments (SFE) featured the Community Leveraged Unified Ensemble (CLUE), a coordinated convection-allowing model (CAM) ensemble framework designed to provide empirical guidance for development of operational CAM systems. The 2017 CLUE included 81 members that all used 3-km horizontal grid spacing over the CONUS, enabling direct comparison of forecasts generated using different dynamical cores, physics schemes, and initialization procedures. This study uses forecasts from several of the 2017 CLUE members and one operational model to evaluate and compare CAM representation and next-day prediction of thunderstorms. The analysis utilizes existing techniques and novel, object-based techniques that distill important information about modeled and observed storms from many cases. The National Severe Storms Laboratory Multi-Radar Multi-Sensor product suite is used to verify model forecasts and climatologies of observed variables. Unobserved model fields are also examined to further illuminate important intermodel differences in storms and near-storm environments. No single model performed better than the others in all respects. However, there were many systematic intermodel and intercore differences in specific forecast metrics and model fields. Some of these differences can be confidently attributed to particular differences in model design. Model intercomparison studies similar to the one presented here are important to better understand the impacts of model and ensemble configurations on storm forecasts and to help optimize future operational CAM systems. © 2019 American Meteorological Society."
"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."
"30767858100;7101928629;7202954964;","Numerical Convergence of Shallow Convection Cloud Field Simulations: Comparison Between Double-Moment Eulerian and Particle-Based Lagrangian Microphysics Coupled to the Same Dynamical Core",2018,"10.1029/2018MS001285","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050876441&doi=10.1029%2f2018MS001285&partnerID=40&md5=66f7b0c8509fb595a4a423c0ccc21d66","The sensitivity of simulated nonprecipitating cumulus clouds to grid length was investigated using a large-eddy simulation model coupled to a particle-based Lagrangian cloud microphysical model (LCM) and an Eulerian cloud microphysical model (ECM). For the sensitivity experiment, the horizontal/vertical grid length was decreased from 100/80 m to 6.25/5 m. The results of the sensitivity experiment indicated a similar dependency of cloud cover (CC) on the grid length in the LCM and ECM, which is critical for the radiative properties of clouds. CC increased with a shorter grid length, and numerically converged with a horizontal/vertical grid length of 12.5/10 m, although the three-dimensional cloud field and turbulence properties in the cloud layer did not numerically converge and the cloud fields simulated by the LCM and ECM differed. The dependency of CC on grid length originated from the dependency of the turbulence structure in the subcloud layer. Roll convection was clearly simulated in the subcloud layer using a short grid length, but it was gradually obscured with increasing grid length. With a long grid length, the shear production term of turbulent kinetic energy near the surface, which is critical for dominating roll convection, was not simulated because of insufficient vertical layers near the surface. On the other hand, with a short grid length, the number of layers close to the surface was sufficient to reproduce the shear production term, and roll convection was clearly reproduced. ©2018. The Authors."
"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."
"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."
"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."
"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."
"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."
"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."
"6602624225;26431637400;55793350400;55737616800;","The impact of noisy physics on the stability and accuracy of physics-dynamics coupling",2013,"10.1175/MWR-D-13-00035.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84897007983&doi=10.1175%2fMWR-D-13-00035.1&partnerID=40&md5=cbfc2938983f472725c2eeab7e045dc1","The coupling of the dynamical core of a numerical weather prediction model to the physical parameterizations is an important component of model design. This coupling between the physics and the dynamics is explored here from the perspective of stochastic differential equations (SDEs). It will be shown that the basic properties of the impact of noisy physics on the stability and accuracy of common numerical methods may be obtained through the application of the basic principles of SDEs. A conceptual model setting is used that allows the study of the impact of noise whose character may be tuned to be either very red (smooth) or white (noisy). The change in the stability and accuracy of common numerical methods as the character of the noise changes is then studied. Distinct differences are found between the ability of multistage (Runge-Kutta) schemes as compared with multistep (Adams-Bashforth/leapfrog) schemes to handle noise of various characters. These differences will be shown to be attributable to the basic philosophy used to design the scheme. Additional experiments using the decentering of the noisy physics will also be shown to lead to strong sensitivity to the quality of the noise. As an example, the authors find the novel result that noise of a diffusive character may lead to instability when the scheme is decentered toward greater implicitness. These results are confirmed in a nonlinear shear layer simulation using a subgrid-scale mixing parameterization. This subgridscale mixing parameterization is modified stochastically and shown to reproduce the basic principles found here, including the notion that decentering toward implicitness may lead to instability."
"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."
"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."
"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."
"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."
"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."
"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."
"6701500839;8696068200;56460283800;","Adaptive wavelet simulation of global ocean dynamics using a new Brinkman volume penalization",2015,"10.5194/gmd-8-3891-2015","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84949659307&doi=10.5194%2fgmd-8-3891-2015&partnerID=40&md5=519aa2ccd8edc64f387f40ebc77f3ad3","In order to easily enforce solid-wall boundary conditions in the presence of complex coastlines, we propose a new mass and energy conserving Brinkman penalization for the rotating shallow water equations. This penalization does not lead to higher wave speeds in the solid region. The error estimates for the penalization are derived analytically and verified numerically for linearized one-dimensional equations. The penalization is implemented in a conservative dynamically adaptive wavelet method for the rotating shallow water equations on the sphere with bathymetry and coastline data from NOAA's ETOPO1 database. This code could form the dynamical core for a future global ocean model. The potential of the dynamically adaptive ocean model is illustrated by using it to simulate the 2004 Indonesian tsunami and wind-driven gyres. © 2015 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."
"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.
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.."
"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."
"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."
"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)."
"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."
"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."
"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."
"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."
"24802214200;37122980800;55713442200;55797316500;7406671641;","Mitigation of coupled model biases induced by dynamical core misfitting through parameter optimization: Simulation with a simple pycnocline prediction model",2014,"10.5194/npg-21-357-2014","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896742133&doi=10.5194%2fnpg-21-357-2014&partnerID=40&md5=965138e691bbb2b9064669df7ba74382","Imperfect dynamical core is an important source of model biases that adversely impact on the model simulation and predictability of a coupled system. With a simple pycnocline prediction model, in this study, we show the mitigation of model biases through parameter optimization when the assimilation model consists of a ""biased"" time-differencing. Here, the ""biased"" time-differencing is defined by a different time-differencing scheme from the ""truth"" model that is used to produce ""observations"", which generates different mean values, climatology and variability of the assimilation model from the ""truth"" model. A series of assimilation experiments is performed to explore the impact of parameter optimization on model bias mitigation and climate estimation, as well as the role of different media parameter estimations. While the stochastic ""physics"" implemented by perturbing parameters can enhance the ensemble spread significantly and improve the representation of the model ensemble, signal-enhanced parameter estimation is able to mitigate the model biases on mean values and climatology, thus further improving the accuracy of estimated climate states, especially for the low-frequency signals. In addition, in a multiple timescale coupled system, parameters pertinent to low-frequency components have more impact on climate signals. Results also suggest that deep ocean observations may be indispensable for improving the accuracy of climate estimation, especially for low-frequency signals. © 2014 Author(s)."
"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."
"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."
"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."
"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."
"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."
"7409321916;57202980005;56567092700;57192944066;","A Simple Method to Find a Neighboring Grid Point on the Cubed-sphere",2018,"10.1007/s13143-018-0027-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050162546&doi=10.1007%2fs13143-018-0027-x&partnerID=40&md5=727f2b9bb79b903ebde03ed09541f9b9","Recently, there has been increasing interest in the use of cubed-sphere geometry in the geoscientific modeling community. For diverse numerical operations such as remapping and parallel communications, the search of neighbor elements or points is required. Here, we propose a novel and simple method to find a neighboring element or point on the cubed-sphere. This new method can be universally used for any types of cubed-sphere, for example, equi-angular, conformal, uniform-jacobian cubed-sphere etc. Key points to simplify the search algorithm are the definition of rotation counts of panels neighboring the centered panel, and the use of operations to obtain integer quotient and remainder given an index interval from the source point. Along with the introduction of the methodology, some examples using this method is described in this article. © 2018, Korean Meteorological Society and Springer Nature B.V."
"55394412800;55542200200;7004093651;7003595038;","Choice of function spaces for thermodynamic variables in mixed finite-element methods",2018,"10.1002/qj.3268","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052511087&doi=10.1002%2fqj.3268&partnerID=40&md5=ac62783ef858409d5c498faeff6dc279","We study the dispersion properties of three choices for the buoyancy space in a mixed finite-element discretization of geophysical fluid flow equations. The problem is analogous to that of the staggering of the buoyancy variable in finite-difference discretizations. Discrete dispersion relations of the two-dimensional linear gravity wave equations are computed. By comparison with the analytical result, the best choice for the buoyancy space basis functions is found to be the horizontally discontinuous, vertically continuous option. This is also the space used for the vertical component of the velocity. At lowest polynomial order, this arrangement mirrors the Charney–Phillips vertical staggering known to have good dispersion properties in finite-difference models. A fully discontinuous space for the buoyancy corresponding to the Lorenz finite-difference staggering at lowest order gives zero phase velocity for high vertical wavenumber modes. A fully continuous space, the natural choice for scalar variables in a mixed finite-element framework, with degrees of freedom of buoyancy and vertical velocity horizontally staggered at lowest order, is found to entail zero phase velocity modes at the large horizontal wavenumber end of the spectrum. Corroborating the theoretical insights, numerical results obtained on gravity wave propagation with fully continuous buoyancy highlight the presence of a computational mode in the poorly resolved part of the spectrum that fails to propagate horizontally. The spurious signal is not removed in test runs with higher-order polynomial basis functions. Runs at higher order also highlight additional oscillations, an issue that is shown to be mitigated by partial mass-lumping. In light of the findings and with a view to coupling the dynamical core to physical parametrizations that often force near the horizontal grid scale, the use of the fully continuous space should be avoided in favour of the horizontally discontinuous, vertically continuous space. © 2018 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal 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.
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.
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.
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.
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."
"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."
"35485250000;16025236700;","A Bayesian optimization approach to multimodel ensemble kalman filter with a low-order model",2015,"10.1175/MWR-D-14-00148.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84943373265&doi=10.1175%2fMWR-D-14-00148.1&partnerID=40&md5=d7e4dae7b5d0f254d3706791e1f645e0","Multimodel ensemble data assimilation may account for uncertainties of numerical models due to different dynamical cores and physics parameterizations. In the previous studies, the ensemble sizes for each model are prescribed subjectively, for example, uniformly distributed to each model. In this study, a Bayesian filter approach to a multimodel ensemble Kalman filter is adopted to objectively estimate the optimal combination of ensemble sizes for each model. An effective inflation method to make the discrete Bayesian filter work without converging to a single imperfect model was developed. As a first step, the proposed approach was tested with the 40-variable Lorenz-96 model. Different values of the model parameter F are used to mimic the multimodel ensemble. The true F is first chosen to be F = 8, and the observations are generated by adding independent Gaussian noise to the true time series. When the multimodel ensemble consists of F = 6, 7, 8, 9, and 10, the Bayesian filter finds the true model and converges to F = 8 quickly. When, F = 6, 7, 9, and 10, the closest two models, F = 7 and F = 9, are selected. When the true F has a periodic variation about F = 8 with a time scale much longer than the observation frequency, the proposed system follows the temporal change, and the error becomes less than that of the time-invariant optimal combination. Sensitivities to several parameters in the proposed system were also investigated, and the system was found to show improvements in a wide range of parameters. © 2015 American Meteorological Society."
"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."
"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"
"57202522440;26633770700;56607014000;31067496800;57201880425;57214596418;","An Energy Consistent Discretization of the Nonhydrostatic Equations in Primitive Variables",2020,"10.1029/2019MS001783","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078830310&doi=10.1029%2f2019MS001783&partnerID=40&md5=585097bc73d528514a7c9de95daf9136","We derive a formulation of the nonhydrostatic equations in spherical geometry with a Lorenz staggered vertical discretization. The combination conserves a discrete energy in exact time integration when coupled with a mimetic horizontal discretization. The formulation is a version of Dubos and Tort (2014, https://doi.org/10.1175/MWR-D-14-00069.1) rewritten in terms of primitive variables. It is valid for terrain following mass or height coordinates and for both Eulerian or vertically Lagrangian discretizations. The discretization relies on an extension to Simmons and Burridge (1981, https://doi.org/10.1175/1520-0493(1981)109<0758:AEAAMC>2.0.CO;2) vertical differencing, which we show obeys a discrete derivative product rule. This product rule allows us to simplify the treatment of the vertical transport terms. Energy conservation is obtained via a term-by-term balance in the kinetic, internal, and potential energy budgets, ensuring an energy-consistent discretization up to time truncation error with no spurious sources of energy. We demonstrate convergence with respect to time truncation error in a spectral element code with a horizontal explicit vertically implicit implicit-explicit time stepping algorithm. ©2019. The Authors."
"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 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"
"24341333600;7004276350;6507628238;55504578600;8947115400;","Advancing dynamical cores of oceanic models across all scales",2019,"10.1175/BAMS-D-18-0303.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85065985181&doi=10.1175%2fBAMS-D-18-0303.1&partnerID=40&md5=de7c7229c38fa3193abf43009de1ad33",[No abstract available]
"36987319800;6603218374;7202208382;","Implementation of the Vector Vorticity Dynamical Core on Cubed Sphere for Use in the Quasi-3-D Multiscale Modeling Framework",2019,"10.1029/2018MS001517","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062373617&doi=10.1029%2f2018MS001517&partnerID=40&md5=1177b89e025f6b2b6a869dbcfdde5a69","The dynamical core that predicts the three-dimensional vorticity rather than the momentum, which is called Vector-Vorticity Model (VVM), is implemented on a cubed sphere. Its horizontal coordinate system is not restricted to orthogonal, while the vertical coordinate is orthogonal to the horizontal surface. Accordingly, all the governing equations of the VVM, which are originally developed with Cartesian coordinates, are rewritten in terms of general curvilinear coordinates. The local coordinates on each cube surface are constructed with the gnomonic equiangular projection. Using global channel domains, the VVM on the cubed sphere has been evaluated by (1) advecting a passive tracer with a bell-shaped initial perturbation along an east-west latitude circle and along a north-south meridional circle and (2) simulating the evolution of barotropic and baroclinic instabilities. The simulated results with the cubed-sphere grids are compared to analytic solutions or those with the regular longitude-latitude grids. The convergence with increasing spatial resolution is also quantified using standard error norms. The comparison shows that the solutions with the cubed-sphere grids are quite reasonable for both linear and nonlinear problems when high resolutions are used. With coarse resolution, degeneracy appears in the solutions of the nonlinear problems such as spurious wave growth; however, it is effectively reduced with increased resolution. Based on the encouraging results in this study, we intend to use this model as the cloud-resolving component in a global Quasi-Three-Dimensional Multiscale Modeling Framework. ©2019. The Authors."
"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"
"36624257700;55764588400;54879515900;55924208000;","A stochastic representation of subgrid uncertainty for dynamical core development",2019,"10.1175/BAMS-D-17-0040.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85069158751&doi=10.1175%2fBAMS-D-17-0040.1&partnerID=40&md5=cdf0ab76e97dcf4fe1672e604e366a72",[No abstract available]
"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."
"16042493100;7004093651;","A Lagrangian vertical coordinate version of the ENDGame dynamical core. Part II: Evaluation of Lagrangian conservation properties",2018,"10.1002/qj.3375","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85054515382&doi=10.1002%2fqj.3375&partnerID=40&md5=90d4d3bf4dd2f81164e26f3128fa17b2","A baroclinic instability test case is used to compare the Lagrangian conservation properties of three versions of a semi-implicit semi-Lagrangian dynamical core: one using a height-based vertical coordinate and two using a Lagrangian vertical coordinate. The Lagrangian coordinate versions differ in the choice of target levels to which model levels are reset after each step—the first uses the initial model level heights while the second uses quasi-Lagrangian target levels. A range of diagnostics related to Lagrangian conservation are computed, including global entropy, unavailable energy, cross-isentrope mass flux, and consistency of potential temperature and potential vorticity with passive tracers and parcel trajectories. The global entropy, unavailable energy, and cross-isentrope fluxes do not suggest any clear advantage or disadvantage from the use of a Lagrangian vertical coordinate, though the cross-isentrope flux reveals a flaw in the formulation of the remapping of potential temperature in the Lagrangian coordinate model at the top boundary. The use of a Lagrangian vertical coordinate with quasi-Lagrangian target levels improves the consistency among potential temperature as a dynamical variable, potential temperature as a tracer and potential temperature on Lagrangian particle trajectories. It also improves consistency between a potential vorticity tracer and potential vorticity on Lagrangian particle trajectories. However, it degrades the consistency between model and tracer potential vorticity, as well as between model potential vorticity and potential vorticity on Lagrangian trajectories. This degradation appears to be related to the slopes of model levels, which are greater in the version with quasi-Lagrangian target levels. © 2018 Crown Copyright, Met Office. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal 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."
"42961592400;6603724340;","A nestable, multigrid-friendly grid on a sphere for global spectral models based on Clenshaw–Curtis quadrature",2018,"10.1002/qj.3282","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052942019&doi=10.1002%2fqj.3282&partnerID=40&md5=7a1a20511d8d0c6dc995c81755c861af","A new grid system on a sphere is proposed which allows for straightforward implementation of both spherical-harmonics-based spectral methods and gridpoint-based multigrid methods. The latitudinal gridpoints in the new grid are equidistant and spectral transforms in the latitudinal direction are performed using Clenshaw–Curtis quadrature. The spectral transforms with this new grid and quadrature are shown to be exact within machine precision provided that the grid truncation is such that there are at least 2N + 1 latitudinal gridpoints for the total truncation wavenumber of N. The new grid and quadrature is implemented and tested on a shallow-water equations model and the hydrostatic dry dynamical core of the global NWP model JMA-GSM. The integration results obtained with the new quadrature are shown to be almost identical to those obtained with the conventional Gaussian quadrature on a Gaussian grid. Only minor code changes are required to adapt any Gaussian-based spectral models to employ the proposed quadrature. © 2018 Royal Meteorological Society"
"56293796000;16636807900;11939929300;7005808242;","Sensitivity of Radiative-Convection Equilibrium to Divergence Damping in GFDL-FV3-Based Cloud-Resolving Model Simulations",2018,"10.1029/2017MS001225","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050931187&doi=10.1029%2f2017MS001225&partnerID=40&md5=74ac62e131175619909f001bdcb709c6","Using a nonhydrostatic model based on a version of Geophysical Fluid Dynamics Laboratory's FV3 dynamical core at a cloud-resolving resolution in radiative-convective equilibrium (RCE) configuration, the sensitivity of the mean RCE climate to the magnitude and scale-selectivity of the divergence damping is explored. Divergence damping is used to reduce small-scale noise in more realistic configurations of this model. This sensitivity is tied to the strength (and width) of the convective updrafts, which decreases (increases) with increased damping and acts to organize the convection, dramatically drying out the troposphere and increasing the outgoing longwave radiation. Increased damping also results in a much-broadened precipitation probability distribution and larger extreme values, as well as reduction in cloud fraction, which correspondingly decreases the magnitude of shortwave and longwave cloud radiative effects. Solutions exhibit a monotonic dependence on the strength of the damping and asymptotically converge to the inviscid limit. While the potential dependence of RCE simulations on resolution and microphysical assumptions are generally appreciated, these results highlight the potential significance of the choice of subgrid numerical diffusion in the dynamical core. ©2018. The Authors."
"6602718555;8589549500;36678135100;","Finite elements used in the vertical discretization of the fully compressible core of the ALADIN system",2018,"10.1175/MWR-D-18-0043.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062150855&doi=10.1175%2fMWR-D-18-0043.1&partnerID=40&md5=631a8a91655920401e004f2f6a7fdb96","The finite-element method with B splines is used for definition of vertical operators in the nonhydrostatic fully compressible dynamical core of the ALADIN system. It represents a generalization of the same method used in the hydrostatic dynamical core shared by the ALADIN system and the global forecast system ARPEGE/IFS. The method is shown to be robust enough in idealized academic tests and real simulations. Its theoretical superiority is shown when compared with the finitedifference method. © 2018 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."
"6506900387;6503946355;7003871651;","Toward a PV-based algorithm for the dynamical core of hydrostatic global models",2016,"10.1175/MWR-D-15-0379.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84978036339&doi=10.1175%2fMWR-D-15-0379.1&partnerID=40&md5=e25f4ecc5f1a6a7b0d31b446535d1d26","The diabatic contour-advective semi-Lagrangian (DCASL) algorithms previously constructed for the shallow-water and multilayer Boussinesq primitive equations are extended to multilayer non-Boussinesq equations on the sphere using a hybrid terrain-following-isentropic (σ-δ) vertical coordinate. It is shown that the DCASL algorithms face challenges beyond more conventional algorithms in that various types of damping, filtering, and regularization are required for computational stability, and the nonlinearity of the hydrostatic equation in the σ-δ coordinate causes convergence problems with setting up a semi-implicit time-stepping scheme to reduce computational cost. The prognostic variables are an approximation to the Rossby-Ertel potential vorticity Q, a scaled pressure thickness, the horizontal divergence, and the surface potential temperature. Results from the DCASL algorithm in two formulations of the σ-δ coordinate, differing only in the rate at which the vertical coordinate tends to δ with increasing height, are assessed using the baroclinic instability test case introduced by Jablonowski and Williamson in 2006. The assessment is based on comparisons with available reference solutions as well as results from two other algorithms derived from the DCASL algorithm: One with a semi-Lagrangian solution for Q and another with an Eulerian grid-based solution procedure with relative vorticity replacing Q as the prognostic variable. It is shown that at intermediate resolutions, results comparable to the reference solutions can be obtained. © 2016 American Meteorological Society."
"24399144800;6603315146;","A layered model approach for simulating high river discharge events from land to the ocean",2015,"10.1007/s10872-014-0254-4","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84925487820&doi=10.1007%2fs10872-014-0254-4&partnerID=40&md5=1b2f70bb81224d9bc8781534e0beaead","This study presents a new approach for simulating surface runoff, river flow, and oceanic flow. Hydrological-ocean coupled models often stitch the two models at the river mouth because they typically differ in formulation, dynamically and dimensionally. An isopycnal-layered model is shown to naturally couple hydrological and oceanic processes seamlessly with the use of a single dynamical core. Numerical experiments show the high discharge event of the Abukuma River in Japan during Typhoon Roke with realistic river flows and freshwater plumes in the ocean. The time series of the river discharge rates also match well with observations from upstream to downstream. © 2014, The Oceanographic Society of Japan and Springer Japan."
"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."
"36678135100;8727832400;23013377000;","A non-hydrostatic global spectral dynamical core using a height-based vertical coordinate",2013,"10.3402/tellusa.v65i0.20270","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84882712095&doi=10.3402%2ftellusa.v65i0.20270&partnerID=40&md5=31cc0516fec7ef9ce6a7cf118e653a92","Most of the dynamical cores of operational global models can be broadly classified according to the spatial discretisation into two categories: spectral models with mass-based vertical coordinate and grid point models with height-based vertical coordinate. This article describes a new non-hydrostatic dynamical core for a global model that uses the spectral transform method for the horizontal directions and a height-based vertical coordinate. Velocity is expressed in the contravariant basis (instead of the geographical orthonormal basis pointing to the East, North and Zenith directions) so that the expressions of the boundary conditions and the divergence of the velocity are simpler. Prognostic variables in our model are the contravariant components of the velocity, the logarithm of pressure and the logarithm of temperature. Covariant tensor analysis is used to derive the differential operators of the prognostic equations, such as the curl, gradient, divergence and covariant derivative of the contravariant velocity. A Lorenz type grid is used in the vertical direction, with the vertical contravariant velocity staggered with respect to the other prognostic variables. High-order vertical operators are constructed following the finite difference technique. Time stepping is semi-implicit because it allows for long time steps that compensates the cost of the spectral transformations. A set of experiments reported in the literature is implemented so as to confirm the accuracy and efficiency of the new dynamical core. © 2013 J. Simarro et al."
"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)."
"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."
"7202866440;7201507999;7201816774;7203015939;6507492100;7004829880;","A massively parallel dynamical core for continental- to global-scale river transport",2007,,"https://www.scopus.com/inward/record.uri?eid=2-s2.0-80052932693&partnerID=40&md5=7f1755f768e48968acdaa1308da952de",[No abstract available]
"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."
"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.."
"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."
"40761500800;57203288317;55338676800;10039602000;7102450474;57202522440;7202048112;23991212200;6701835010;57215343134;55351266200;57214597285;","Initial Results From the Super-Parameterized E3SM",2020,"10.1029/2019MS001863","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85078860810&doi=10.1029%2f2019MS001863&partnerID=40&md5=d29f000771284c1ae63f32fd8f3232eb","Results from the new Department of Energy super-parameterized (SP) Energy Exascale Earth System Model (SP-E3SM) are analyzed and compared to the traditionally parameterized E3SMv1 and previous studies using SP models. SP-E3SM is unique in that it utilizes Graphics Processing Unit hardware acceleration, cloud resolving model mean-state acceleration, and reduced radiation to dramatically increase the model throughput and allow decadal experiments at 100-km external resolution. It also differs from other SP models by using a spectral element dynamical core on a cubed-sphere grid and a finer vertical grid with a higher model top. Despite these differences, SP-E3SM generally reproduces the behavior of other SP models. Tropical wave variability is improved relative to E3SM, including the emergence of a Madden-Julian Oscillation and a realistic slowdown of Moist Kelvin Waves. However, the distribution of precipitation exhibits indicates an overly frequent occurrence of rain rates less than 1 mm day-1, and while the timing of diurnal rainfall shows modest improvements the signal is not as coherent as observations. A notable grid imprinting bias is identified in the precipitation field and attributed to a unique feedback associated with the interactions between the explicit cloud resolving model convection and the spectral element grid structure. Spurious zonal mean column water tendencies due to grid imprinting are quantified—while negligible for the conventionally parameterized E3SM, they become large with super-parameterization, approaching 10% of the physical tendencies. The implication is that finding a remedy to grid imprinting will become especially important as spectral element dynamical cores begin to be combined with explicitly resolved convection. ©2020. The Authors."
"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."
"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."
"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."
"16479703400;57219865812;57188955794;15724418700;","Extending the modular earth submodel system (messy v2.54) model hierarchy: The echam/messy idealized (emil) model setup",2020,"10.5194/gmd-13-5229-2020","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85095808000&doi=10.5194%2fgmd-13-5229-2020&partnerID=40&md5=60ed585b755fbb3099b5990b83099f98","As models of the Earth system grow in complexity, a need emerges to connect them with simplified systems through model hierarchies in order to improve process understanding. The Modular Earth Submodel System (MESSy) was developed to incorporate chemical processes into an Earth System model. It provides an environment to allow for model configurations and setups of varying complexity, and as of now the hierarchy ranges from a chemical box model to a fully coupled chemistry climate model. Here, we present a newly implemented dry dynamical core model setup within the MESSy framework, denoted as ECHAM/MESSy IdeaLized (EMIL) model setup. EMIL is developed with the aim to provide an easily accessible idealized model setup that is consistently integrated in the MESSy model hierarchy. The implementation in MESSy further enables the utilization of diagnostic chemical tracers. The setup is achieved by the implementation of a new submodel for relaxation of temperature and horizontal winds to given background values, which replaces all other ""physics"" submodels in the EMIL setup. The submodel incorporates options to set the needed parameters (e.g., equilibrium temperature, relaxation time and damping coefficient) to functions used frequently in the past. This study consists of three parts. In the first part, test simulations with the EMIL model setup are shown to reproduce benchmarks provided by earlier dry dynamical core studies. In the second part, the sensitivity of the coupled troposphere stratosphere dynamics to various modifications of the setup is studied. We find a non-linear response of the polar vortex strength to the prescribed meridional temperature gradient in the extratropical stratosphere that is indicative of a regime transition. In agreement with earlier studies, we find that the tropospheric jet moves poleward in response to the increase in the polar vortex strength but at a rate that strongly depends on the specifics of the setup. When replacing the idealized topography to generate planetary waves by mid-Tropospheric wave-like heating, the response of the tropospheric jet to changes in the polar vortex is strongly damped in the free troposphere. However, near the surface, the jet shifts poleward at a higher rate than in the topographically forced simulations. Those results indicate that the wave-like heating might have to be used with care when studying troposphere stratosphere coupling. In the third part, examples for possible applications of the model system are presented. The first example involves simulations with simplified chemistry to study the impact of dynamical variability and idealized changes on tracer transport, and the second example involves simulations of idealized monsoon circulations forced by localized heating. The ability to incorporate passive and chemically active tracers in the EMIL setup demonstrates the potential for future studies of tracer transport in the idealized dynamical model. © 2020 BMJ Publishing Group. All rights reserved."
"57218511333;23092896500;","Sensitivity of simulated temperature, precipitation, and global radiation to different WRF configurations over the Carpathian Basin for regional climate applications",2020,"10.1007/s00382-020-05416-x","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089387478&doi=10.1007%2fs00382-020-05416-x&partnerID=40&md5=a39959c7b7a3bd17f94ef9f4a3805052","In this study, the Weather Research and Forecasting (WRF) model is used to produce short-term regional climate simulations with several configurations for the Carpathian Basin region. The goal is to evaluate the performance of the model and analyze its sensitivity to different physical and dynamical settings, and input data. Fifteen experiments were conducted with WRF at 10 km resolution for the year 2013. The simulations differ in terms of configuration options such as the parameterization schemes, the hydrostatic and non-hydrostatic dynamical cores, the initial and boundary conditions (ERA5 and ERA-Interim reanalyses), the number of vertical levels, and the length of the spin-up period. E-OBS dataset 2 m temperature, total precipitation, and global radiation are used for validation. Temperature underestimation reaches 4–7 °C for some experiments and can be reduced by certain physics scheme combinations. The cold bias in winter and spring is mainly caused by excessive snowfall and too persistent snow cover, as revealed by comparison with satellite-based observations and a test simulation without snow on the surface. Annual precipitation is overestimated by 0.6–3.8 mm day−1, with biases mainly accumulating in the period driven by large-scale weather processes. Downward shortwave radiation is underestimated all year except in the months dominated by locally forced phenomena (May to August) when a positive bias prevails. The incorporation of downward shortwave radiation to the validation variables increased the understanding of underlying problems with the parameterization schemes and highlighted false model error compensations. © 2020, The Author(s)."
"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)."
"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."
"57203166383;35739529800;7004060399;","Non-Additivity of the Midlatitude Circulation Response to Regional Arctic Temperature Anomalies: The Role of the Stratosphere",2020,"10.1029/2020GL088057","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089947080&doi=10.1029%2f2020GL088057&partnerID=40&md5=84ffd522988aecaa5d1f7a5c592f2601","Previous studies have documented the impact of the Arctic sea ice loss and associated warming on the midlatitude weather and climate, especially the influence of sea ice retreat over the Barents-Kara Sea on the North Atlantic and Europe regions. However, less attention has been given to other geographical locations over the Arctic, and to the linear additivity of the circulation response to regional Arctic sea ice loss and temperature anomalies. Using a simplified dry dynamical core model, we demonstrate that responses to regional Arctic temperature anomalies over the Barents-Kara Sea, Baffin Bay-Davis Strait-Labrador Sea, and East Siberia-Chukchi Sea, separately, cause similar equatorward shift of the tropospheric jet, but different stratospheric polar vortex responses. Furthermore, responses to regional Arctic temperature anomalies are not linearly additive, and the residual resembles a positive Northern Annular Mode-like structure. Additional targeted experiments highlight the stratospheric influence in the non-additivity of the midlatitude tropospheric response. ©2020. American Geophysical Union. All Rights Reserved."
"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."
"8713807600;55723773500;55119602800;24481728600;57218196866;55621952600;57208455668;","Multiple hydrometeors all-sky microwave radiance assimilation in FV3GFS",2020,"10.1175/MWR-D-19-0231.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088229375&doi=10.1175%2fMWR-D-19-0231.1&partnerID=40&md5=74f65bb8b95b0a987f665e547237d8c4","Motivated by the use of the GFDL microphysics scheme in the Finite-Volume Cubed-Sphere Dynamical Core Global Forecast System (FV3GFS), the all-sky radiance assimilation framework has been expanded to include precipitating hydrometeors. Adding precipitating hydrometeors allows the assimilation of precipitation-affected radiance in addition to cloudy radiance. In this upgraded all-sky framework, the five hydrometeors, including cloud liquid water, cloud ice, rain, snow, and graupel, are the new control variables, replacing the original cloud water control variable. The Community Radiative Transfer Model (CRTM) was interfaced with the newly added precipitating hydrometeors. Subgrid cloud variability was considered by using the average cloud overlap scheme. Multiple scattering radiative transfer was activated in the upgraded framework. Radiance observations from the Advanced Microwave Sounding Unit-A (AMSU-A) and the Advanced Technology Microwave Sounder (ATMS) over ocean were assimilated in all-sky approach. This new constructed all-sky framework shows neutral to positive impact on overall forecast skill. Improvement was found in 500-hPa geopotential height forecast in both Northern and Southern Hemispheres. Temperature forecast was also improved at 850 hPa in the Southern Hemisphere and the tropics. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"57207473157;55899884100;7401436524;57209413320;57209422031;57218196192;8905764300;","A multiscale dynamical model in a dry-mass coordinate for weather and climate modeling: Moist dynamics and its coupling to physics",2020,"10.1175/MWR-D-19-0305.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088227551&doi=10.1175%2fMWR-D-19-0305.1&partnerID=40&md5=05c2146b5812eb182b47ae9fbd0c8cbb","A multiscale dynamical model for weather forecasting and climate modeling is developed and evaluated in this study. It extends a previously established layer-averaged, unstructured-mesh nonhydrostatic dynamical core (dycore) to moist dynamics and parameterized physics in a dry-mass vertical coordinate. The dycore and tracer transport components are coupled in a mass-consistent manner, with the dycore providing time-averaged horizontal mass fluxes to passive transport, and tracer transport feeding back to the dycore with updated moisture constraints. The vertical mass flux in the tracer transport is obtained by reevaluating the mass continuity equation to ensure compatibility. A general physics-dynamics coupling workflow is established, and a dycore-tracer-physics splitting strategy is designed to couple these components in a flexible and efficient manner. In this context, two major physics-dynamics coupling strategies are examined. Simple-physics packages from the 2016 Dynamical Core Model Intercomparison Project (DCMIP2016) experimental protocols are used to facilitate the investigation of the model behaviors in idealized moist-physics configurations, including cloud-scale modeling, weather forecasting, and climate modeling, and in a real-world test-case setup. Performance evaluation demonstrates that the model is able to produce reasonable sensitivity and variability at various spatiotemporal scales. The consideration and implications of different physics-dynamics coupling options are discussed within this context. The appendix provides discussion on the energetics in the continuous- and discrete-form equations of motion. © 2020 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)."
"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."
"55622685700;7201784177;","Dynamics of anomalous stratospheric eddy heat flux events in an idealized model",2020,"10.1175/JAS-D-19-0231.1","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091554147&doi=10.1175%2fJAS-D-19-0231.1&partnerID=40&md5=232d9856ca17371a2585c8c93919f311","Extreme stratospheric eddy and sudden stratospheric warming (SSW) events both involve anomalous stratospheric eddy heat flux. The cause of the anomaly has been hypothesized to be due to tropospheric or stratospheric dynamics. Here, ensemble spectral nudging experiments in a dry dynamical-core model are used to quantify the role of the troposphere versus the stratosphere. The experiments focus on the wavenumber-1 heat flux since it dominates the anomalous stratospheric eddy heat flux during both events. Nudging the stratospheric zonal-mean flow does not account for the anomalous stratospheric wave-1 heat flux. Nudging either tropospheric wave-1 or higher-order wavenumbers (k ≥ 2) accounts for a large fraction of the anomalous stratospheric wave-1 heat flux. Mechanism denial experiments, whereby tropospheric eddies (wave 1 or k ≥ 2) are nudged and the zonal-mean flow is fixed to climatology, suggest the climatological stratospheric zonal-mean flow is sufficient to account for the anomalous stratospheric wave-1 heat flux and wave-wave interaction plays a role in generating the anomalous tropospheric wave-1 source. Taken together, the experiments suggest the troposphere dominates the anomalous stratospheric eddy heat flux during extreme stratospheric eddy and SSW events while the stratospheric zonal-mean flow plays secondary role. © 2020 American Meteorological Society. All rights reserved."
"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."
"36608763800;44561454300;","Effects of Topography and Realistic Drag on the Southern Hemisphere Midlatitude Jet in a Dry Model",2020,"10.1029/2019MS001717","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85082170674&doi=10.1029%2f2019MS001717&partnerID=40&md5=cc77f2ba9d7c75d2d205b795e5fa13e7","Climate models have substantial biases in the climatological latitude of the Southern Hemisphere eddy-driven jet and the time scale of annular mode variability and disagree on the jet response to climate change. Zonally symmetric dry dynamical cores are often used for idealized modeling of the jet response to forcing and its sensitivity to model setup changes. The limits to which these models represent the key mechanisms that control the jet in complex models or the real world have not been systematically investigated. Here we show that substantial intermodel differences in jet latitude and strength can arise from differences in dynamical cores and resolved topography. Including topography and a more realistic surface drag in a dry model substantially alters the jet response to changes in drag strength. Using real-world maps, enhanced drag over land shifts the jet poleward, whereas enhanced drag over the ocean leads to an equatorward shift. No universal relationship between annular mode time scale and forced response emerges in the dry model with topography. These results suggest that zonally symmetric models with Rayleigh drag lack important mechanisms that control the behavior of the midlatitude jet in coupled climate models. A dry model with topography and quadratic surface drag can fill this gap in the model hierarchy. © 2020. The Authors."
"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)."
"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)."
"6701500839;8696068200;","WAVETRISK-1.0: An adaptive wavelet hydrostatic dynamical core",2019,"10.5194/gmd-12-4901-2019","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075823070&doi=10.5194%2fgmd-12-4901-2019&partnerID=40&md5=9f535908e59e0cb5f52657ffb9112ca9","This paper presents the new adaptive dynamical core wavetrisk. The fundamental features of the wavelet-based adaptivity were developed for the shallow water equation on the β plane and extended to the icosahedral grid on the sphere in previous work by the authors. The three-dimensional dynamical core solves the compressible hydrostatic multilayer rotating shallow water equations on a multiscale dynamically adapted grid. The equations are discretized using a Lagrangian vertical coordinate version of the dynamico model. The horizontal computational grid is adapted at each time step to ensure a user-specified relative error in either the tendencies or the solution. The Lagrangian vertical grid is remapped using an arbitrary Lagrangian-Eulerian (ALE) algorithm onto the initial hybrid σ-pressure-based coordinates as necessary. The resulting grid is adapted horizontally but uniform over all vertical layers. Thus, the three-dimensional grid is a set of columns of varying sizes. The code is parallelized by domain decomposition using mpi, and the variables are stored in a hybrid data structure of dyadic quad trees and patches. A low-storage explicit fourth-order Runge-Kutta scheme is used for time integration. Validation results are presented for three standard dynamical core test cases: mountain-induced Rossby wave train, baroclinic instability of a jet stream and the Held and Suarez simplified general circulation model. The results confirm good strong parallel scaling and demonstrate that wavetrisk can achieve grid compression ratios of several hundred times compared with an equivalent static grid model. © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License."
"57189843062;57189845715;7003986715;57210931383;57210932643;57210937545;","Impacts of different physical parameterization configurations on widespread heavy rain forecast over the northern area of Vietnam in wrf-arw model",2019,"10.1155/2019/1010858","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071915069&doi=10.1155%2f2019%2f1010858&partnerID=40&md5=8952bfe9e21078de07f09b09294b0fc8","This study investigates the impacts of different physical parameterization schemes in the Weather Research and Forecasting model with the ARW dynamical core (WRF-ARW model) on the forecasts of heavy rainfall over the northern part of Vietnam (Bac Bo area). Various physical model configurations generated from different typical cumulus, shortwave radiation, and boundary layer and from simple to complex cloud microphysics schemes are examined and verified for the cases of extreme heavy rainfall during 2012-2016. It is found that the most skilled forecasts come from the Kain-Fritsch (KF) scheme. However, relating to the different causes of the heavy rainfall events, the forecast cycles using the Betts-Miller-Janjic (BMJ) scheme show better skills for tropical cyclones or slowly moving surface low-pressure system situations compared to KF scheme experiments. Most of the sensitivities to KF scheme experiments are related to boundary layer schemes. Both configurations using KF or BMJ schemes show that more complex cloud microphysics schemes can also improve the heavy rain forecast with the WRF-ARW model for the Bac Bo area of Vietnam. © 2019 Tien Du Duc et al."
"56508170200;","A structure-preserving discretization of ocean parametrizations on unstructured grids",2018,"10.1016/j.ocemod.2018.10.002","https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055314432&doi=10.1016%2fj.ocemod.2018.10.002&partnerID=40&md5=005c8f90aed492db87fb2dee61ca098c","A structure-preserving discretization of the isoneutral diffusion of Redi and of the eddy induced skew diffusion scheme of Gent and McWilliams on unstructured grids is described. The discretization is based on a variational principle and its essential element is a construction of a discrete Hilbert space by means of admissible vector reconstructions. These reconstructions are applied to discretize the isoneutral slopes as the key component of the parametrizations. Through the discrete scalar product of the Hilbert space for the tracers we are able to represent isoneutral mixing tensor and eddy advection in weak form and to prove that the resulting discrete algorithm preserves essential physical properties of the continuous operator. The discretization follows in principle the established variational and skew-flux approach but implements these concepts via a natural extension of the discretization of the dynamical core of the unstructured grid ocean model ICON-O. The theoretical analysis is supplemented by numerical experiments that illustrate that the discretization indeed implements the functionality of isoneutral diffusion and skew diffusion as complementary parameterizations of unresolved mesoscale eddy effects. © 2018 Elsevier Ltd"
"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."
"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."
"35209486200;57188864543;7006211106;7401952672;","CariCOOS: Improving high-resolution numerical weather prediction for the northeast Caribbean region",2016,"10.23919/oceans.2015.7404498","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84963975898&doi=10.23919%2foceans.2015.7404498&partnerID=40&md5=faaf6de9901a8b9487d08b21a6f8176d","The northeast Caribbean as other insular regions lack reliable high-resolution weather forecast data of 10-meter winds to serve as the engine of numerical ocean models targeting high resolution waves and currents forecasts for nearshore areas. This issue is exacerbated due to the complex orographic features of the Antilles, which govern topographic shadowing and incoming solar radiation fields responsible for the diurnally forced convection typical of tropical island weather. A solution to this problem is currently under evaluation for the CariCOOS region. This solution employs both dynamical numerical solvers of the Weather Research and Forecasting (WRF) Model, which are referred to as the ARW (Advanced Research WRF), and the NMM (Non-hydrostatic Mesoscale Model) cores. CariCOOS research and development efforts are executed in collaboration with the National Weather Service Weather Forecast Office San Juan (NWS WFO SJU). CariCOOS current operational WRF model setups are based on the NMM core at resolutions of 6-km, 2-km, and 1-km. These models target short and medium range forecast; the latest experimental WRF model setup is based on the ARW with resolutions of up to 500-m. The WRF-ARW setup is currently under evaluation to improve very-short-term weather forecast, in support of maritime operations of high-traffic ports and harbors (Bay of San Juan, PR, and Port of Yabucoa, PR). Noteworthy improvement have been achieved as evidenced by model skill assessments of forecasted wind speed, and wind direction of these WRF model setups when compared to in-situ observations of CariCOOS assets (land base weather stations and coastal buoys). The numerical weather prediction forecasting improvements realized via the implementation of both WRF dynamical cores are primarily driven by the increase in horizontal resolution. The most prominent improvements in weather forecasts is were achieved for the leeward side of Puerto Rico and U.S. Virgin Islands and harbor regions when simulated at very fine horizontal grid spacing resolution (less than 1-km). Considering forecast lead time requirements of the NWS WFO SJU, CariCOOS researchers constantly strive to optimize WRF model setups to its limit. Details of the various CariCOOS WRF model setups and implementations will be presented in this paper along with validation statistics. © 2015 MTS."
"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."
"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."
"8080847900;55928817500;26531118000;6603439625;7006005916;7003936713;55293073600;37007098900;","Multiscale Air Quality with the NMMB/BSC Chemical Transport Model",2013,"10.1007/978-94-007-5577-2_53","https://www.scopus.com/inward/record.uri?eid=2-s2.0-84885413700&doi=10.1007%2f978-94-007-5577-2_53&partnerID=40&md5=4df33ea9795d58fd024bbbad0f9211b3","The NMMB/BSC Chemical Transport Model (NMMB/BSC-CTM) is a new air quality modeling system under development at the Earth Sciences Department of BSC in collaboration with several research institutions. It is an on-line model based on the NCEP new global/regional Nonhydrostatic Multiscale Model on the B grid (NMMB). NMMB is an evolution of the WRF-NMMe model extending from meso to global scales. Its unified nonhydrostatic dynamical core allows regional and global simulations and forecasts. NMMB/BSC-CTM incorporates an aerosol module that simulates the global life cycle of mineral dust, sea salt, black carbon and organic carbon, and sulfate. Additionally, a gas-phase chemistry module has been implemented. © Springer Science+Business Media Dordrecht 2014."
"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."