Impact of subgrid scale orographic effects on offshore sea surface wind simulation in WRF

Turbulent scale orographic form drag (TOFD) and gravity wave drag (GWD) play an essential role for the surface wind simulation over complex terrain regions. In this study, we compared the effects of TOFD and GWD around the East Sea, the leeward side of complex terrain and mountains. Using the weather research and forecasting model, the sensitivity experiments were designed with different combination of parameter schemes: TOFD_GWD (with both TOFD and GWD scheme), TOFD_only, GWD_only, and control simulation (with no scheme). Four simulations with different selections of TOFD and the GWD were compared to the near surface wind at 10 m observed by buoy and AWS. The experiment and comparison periods were selected in February 2022, when wind speed was strong and westerly wind prevailed. Compared with AWS observation, TOFD_only simulation reduces root mean square error (RMSE) substantially; however, TOFD_only experiment increases RMSE in all buoy stations in East Sea. Over the ocean, the TOFD_GWD simulation reduces RMSE significantly, but it shows no significant change at most AWS stations. The positive effect of the TOFD around mountain region is already shown in previous study; however, the impact of GWD on mountain downstream near shore ocean is new finding in this study. These results highlight the role of GWD improving the prediction skill of sea surface wind on the leeward side of complex terrain and mountains.