VERY IMPORTANT: Wind Minus Current revisited during ESMF coupling

[arango]

The ROMS and WRF NUOPC cap modules were updated to exchange surface current (Usur, Vsur) between ocean and atmosphere couple components.

We are currently using the WRF code from ​https://github.com/myroms, which we applied a couple of corrections to the code submitted to its developers and will appear in future releases. As before, there will be no need to patch WRF for each release version.

Test Case

The Hurricane IRENE application has a new test case in the IRENE/Coupling/data_wrf_roms_wmc subdirectory. For more details, please check the link to the roms_test repository inGitHub for detailed information and instructions:

​https://github.com/myroms/roms_test/blob/main/IRENE/Coupling/data_wrf_roms_wmc/Readme.md

The ROMS and WRF grids are incongruent in this test case. Since ROMS doesn't cover all the ocean points in the WRF grid (red domain below), a DATA component is used to supply such values from the 3-hour HyCOM dataset. ROMS and DATA components export surface ocean current at the cell center (RHO-points). Then, the ocean currents from DATA and ROMS are melded smoothly using the appropriate weights.

Surface Ocean U-velocity	Surface Ocean V-velocity

The meldes surface currents are imported by WRF into variables grid%uoce and grid%voce. We will continue exploring WRF internal parameters to study the effects of the surface currents on the winds and wind stress. As shown by Renault et al. (2016), the feedback from surface ocean currents to the atmosphere is an eddy-killing effect stabilizing the Gulf Stream separation at Cape Hatteras in WRF-ROMS fully coupled applications. The result is around 0.3 N/m² weaker surface wind stress in the core of the Gulf Stream.