The Impact of Observed Drag Reduction Over Land on Typhoon Forecasting.

The surface drag coefficient plays a crucial role in determining the momentum exchange between the Earth's surface and the atmosphere. Previous studies have observed a tendency for the drag coefficient to decrease at high wind speeds over land, primarily due to the inverse energy cascade. This study aims to examine the impacts of the reduced drag coefficient on the typhoon forecasting skills in terms of the track, the central pressure, and the 10‐m maximum wind speed. Drag reduction is approached through the logarithmic wind profile and a new formula that considers the reduction in roughness length. The results show that the track and the 10‐m maximum wind speed forecasts are improved, but these improvements are primarily evident over plain areas, as the typhoon structure is significantly disrupted by the topography over mountainous areas. Additionally, the reduced drag coefficient results in less dissipation of the typhoon's wind fields over land. As the wind speeds at coastal areas are enhanced compared with those in operational model, the changes in the Coriolis force are responsible for the track prediction improvement. These findings highlight the importance of parameterizing coherent processes in current numerical models. Plain Language Summary: Momentum transport efficiency directly determines the energy dissipation of weather systems. Recently the reduced momentum transport efficiency in typhoon high wind conditions over land surface has been documented. Our objective is to comprehend the impact of this reduced efficiency on numerical simulations of typhoons over land. The results show that considering the reduced momentum transport efficiency yields improved typhoon prediction skills in terms of the track and the 10‐m maximum wind speed, over plain areas. Due to the reduced drag coefficient causing the less dissipation of wind fields at the coastal areas, it is found that the changes in the Coriolis force contribute to the track prediction improvement. Key Points: The consideration of drag reduction over land improves the typhoon forecasting skills in terms of the track and the 10‐m maximum wind speedThe improvement of typhoon forecasts is mainly evident over plains, as the topography disrupts the typhoon structure over mountainous areasThe track prediction improvement can be attributed to the changes in Coriolis force [ABSTRACT FROM AUTHOR]