The WAM6-GPU: an OpenACC version of the third-generation spectral wave model WAM (Cycle 6)

The code package WAM6-GPU is accelerated by OpenACC based on the WAM Cycle 6 (refer to as WAM6 hereafter), a third-generation spectral ocean wave model extensively used across the EU states. The original source code is maintained by Dr. Arno Behrens (Helmholtz-Zentrum Hereon). Please refer to https://github.com/mywave/WAM for technical manual, usage and compiling instructions.

version 1.0: Details about the WAM6-GPU v1.0 can be referred to https://egusphere.copernicus.org/preprints/2024/egusphere-2024-169/, as well as README_WAM6-GPU_compilation_usage.pdf.

Version 1.1: Include OpenACC support for nesting and single-point wave output. Now the WAM6-GPU can using executable 'ptime' to output integrated parameters at a list of output points using GPU version. Nesting cases can run on multiple GPUs. 

Version 1.2: Improvement on SNONLIN_OPENACC nonlinear wave interaction. an subroutine SNONLIN_OPENACCv4 is used to further lower the time usage; Fixed some OpenACC coding bugs, especially some indexes errors, wind-swell separation, and radiation stress computation; bug fix in  subroutine mpi_gather_spp_openacc: collapse (2) => collapse(3)

Version 1.3: When modeling typhoon waves, wave height close to the typhoon center is much higher than observations. In analogy with ECWAM, the maximum spectral steepness is manipulated by imposing a limitation to the high frequency part of the spectrum based on a limiting Phillips spectrum. Refer to IFS documentation Cy46r1 PART VII: ECMWF WAVE MODEL Page22, Section 3.2.7 for detail. ALPHAPMAX = 0.031 in wam_source_model.F90 is tunable for this overestimation. Smaller values, higher wave height. Generally, for WAM6 simulation is sensitive to parameters such as taushelter, betamax, and ALPHAPMAX. 

A global test case can only be found in version 1.0 tarfiles, as the bathymetry and wind fields are large.