Abstract
In this study, the accuracy of the WRF (the Weather Research and Forecasting model)-simulated horizontal gradient of offshore wind speed near a coastline is evaluated using in-situ measurements and Envisat/ASAR (Advanced Synthetic Aperture Rader) images. The WRF simulation is conducted for the coastal waters off Shirahama in Wakayama Prefecture and the accuracy is examined in comparison with in-situ measurements from the offshore platform of Shirahama Oceanographic Observatory (referred to as Shirahama) and the Wakayama Southwest buoy (SW-buoy). It is found that WRF overestimates wind speed at Shirahama through the year, while it underestimates wind speed at SW-buoy only for northwesterly winds, which are predominant through the year. For these reasons, WRF tends to have a weaker horizontal gradient of wind speed between these two sites. Compared with wind speed fields obtained from ASAR, it is found that the underestimation at SW-buoy is partly due to the offshore shift of a strong wind zone, formed by the speed-up effect from two upstream strains, in the WRF simulation.
