Assessment of surface drag coefficient parametrizations based on observations and simulations using the Weather Research and Forecasting model

Abstract

The drag coefficient is important in meteorological studies of the boundary layer because it describes the air–sea momentum flux. Eight drag coefficient schemes were assessed. These parametrizations were compared taking into account data from in situ and laboratory observations. The drag coefficients determined using three schemes were consistent with the level-off phenomenon, supported by the results of laboratory studies. The drag coefficient determined using one scheme decreased at wind speeds higher than approximately 30 m s−1, in agreement with indirect measurements under typhoon conditions. In contrast, the drag coefficients determined using the other four schemes increased with wind speed, even under high wind regimes. Sensitivity tests were performed using simulations of two super typhoons in the Weather Research and Forecasting model. While the typhoon tracks were negligibly sensitive to the parametrization used, the typhoon intensities (the maximum 10-m wind speed and the minimum sea level pressure), sizes, and structure, were very sensitive to it.