Assessment of Surface Drag Coefficient Parametrizations based on Observation and WRF Model Simulation

Funing Li, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China, Jinbao Song, Zhejiang University, Ocean College, Zhoushan, China, Hailun He, Second Institute of Oceanography, State Oceanographic Administration of China, Hangzhou, China, Shuang Li, Ocean College, Zhejiang University, Institute of Physical Oceanography, Zhoushan, China and Shoude Guan, Institute of Oceanology, Chinese Academy of Sciences, Key Laboratory of Ocean Circulation and Waves (KLOCAW), Qingdao, China
Abstract:
Characteristics of the drag coefficient with surface wind speed in eight different parametrized schemes selected from issued papers are comparied with observational data and examined in numerical simulations of two super typhoons using the Weather Research and Forecasting (WRF) model. Four parametrized results are consistent with field and laboratory data, reveal that the drag coefficient increases with wind speed but levels off even drops above approximately 30 ms-1 wind speed. The modeling results indicate that the choise of the scheme has almost no impact on typhoon tracks, but affects the intensity (maximum 10-m wind speed, minimum sea level pressure, and power dissipation index), the size (radius of maximum surface winds and average radius of 35kts winds), the structure (surface pressure-wind relationship, and middle and high level wind field), and the precipitation of simulated typhoons. A wave age related parametrization, shows greater improvement in simulations than others, suggests that the influences of wave and sea spray on air–sea flux of momentum should be considered in future work.
Back to: Understanding Air-Sea Coupling in Tropical Cyclones for Improving Model Intensity Forecasts I