Observation and numerical experiments for drag coefficient under typhoon wind forcing

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• 作者：Huiqiu Cao ; Liangming Zhou ; Shuiqing Li…
• 关键词：Key wordsdrag coefficient ; SWAN ; high wind speed ; typhoon
• 刊名：Journal of Ocean University of China
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：16
• 期：1
• 页码：35-41
• 全文大小：
• 刊物主题：Oceanography; Meteorology;
• 出版者：Science Press
• ISSN：1993-5021
• 卷排序：16

文摘

This paper presents a study on drag coefficients under typhoon wind forcing based on observations and numerical experiments. The friction velocity and wind speed are measured at a marine observation platform in the South China Sea. Three typhoons: SOULIK (2013), TRAMI (2013) and FITOW (2013) are observed at a buoy station in the northeast sea area of Pingtan Island. A new parameterization is formulated for the wind drag coefficient as a function of wind speed. It is found that the drag coefficient (C_d) increases linearly with the slope of 0.083×10−3 for wind speed less than 24 m s−1. To investigate the drag coefficient under higher wind conditions, three numerical experiments are implemented for these three typhoons using SWAN wave model. The wind input data are objective reanalysis datasets, which are assimilated with many sources and provided every six hours with the resolution of 0.125°×0.125°. The numerical simulation results show a good agreement with wave observation data under typhoon wind forcing. The results indicate that the drag coefficient levels off with the linear slope of 0.012×10−3 for higher wind speeds (less than 34 m s−1) and the new parameterization improvese the simulation accuracy compared with the Wu (1982) default used in SWAN.