Near-surface wind field in coastal mountain terrain under typhoon influence

Abstract The near-surface wind field during typhoon landfall is significantly influenced by terrain, particularly in coastal mountainous regions. Based on the WRF model, the near-surface wind field in coastal mountain terrain under typhoon influence is studied by using the simulation results of Typhoon Dujuan (1521). A sensitivity analysis was conducted to determine the suitable simulation period (60 h before landfall to 12 h after landfall) and the appropriate physical schemes (Medium-Range Forecast boundary layer scheme and Betts-Miller-Janjic cumulus convection scheme) for Typhoon Dujuan. The comparison between simulated and observed data revealed a high correlation, with a Pearson correlation coefficient of 0.91 during the wind speed mutation period. A comprehensive analysis was then performed, combining horizontal and vertical wind fields, wind speed, and wind direction, with respect to the terrain. This analysis explored phenomena such as wind speed mutations at the station, the stable position of maximum wind speed, and alternating high-low wind speeds in the horizontal wind field. Results indicate that the initial simulation time significantly impacts the typhoon path in complex geographic areas. Selecting an appropriate simulation period effectively reduces terrain-induced interference on the typhoon trajectory. Wind speed mutations during landfall are primarily driven by dynamic changes in the typhoon circulation, highlighting the close relationship between typhoon weakening and these mutations. Mountainous terrain notably alters the near-surface wind field, especially when the typhoon structure interacts with elevated terrain, causing pronounced alternating high-low wind speed patterns. Additionally, during landfall, the typhoon vertical structure becomes unbalanced, further contributing to its weakening. Through a thorough analysis of the near-surface wind field and mountainous terrain, a better understanding of wind speed variations during typhoon landfall is achieved. These findings provide a theoretical foundation for enhancing the accuracy of typhoon predictions in complex terrain conditions, thereby improving the reliability of typhoon path and intensity forecasts.