| Characteristics of Drag Coefficient in Different Coastal Regions of the South China Sea Under Tropical Cyclones–An Observational Study |
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| 引用本文： | 袁金南,宋丽莉,陈雯超,植石群,毕雪岩,刘春霞,黄辉军. Characteristics of Drag Coefficient in Different Coastal Regions of the South China Sea Under Tropical Cyclones–An Observational Study[J]. 热带气象学报(英文版), 2020, 26(4): 417-427. DOI: 10.46267/j.1006-8775.2020.036 |
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| 作者姓名： | 袁金南 宋丽莉 陈雯超 植石群 毕雪岩 刘春霞 黄辉军 |
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| 摘 要： | To investigate the values of 10-m drag coefficient (CD) in different coastal areas under the influence of tropical cyclones, the present study used the observational data from four towers in different coastal areas of the South China Sea (SCS) during six tropical cyclone (TC) passages, and employed the eddy covariance method and the flux profile method. The analysis of footprint showed that the fluxes at Zhizai Island (ZZI), Sanjiao Island (SJI) and Donghai Island (DHI) were influenced basically by the ocean, and the flux at Shangyang Town (SYT) was influenced mainly by the land. The results showed that the dependence relationships of CD on 10-m wind speed (U10) in four different coastal areas under the influence of TCs were different. CD at ZZI and SJI initially increased and then decreased as U10 increased, similar to the pattern over the ocean. CD at ZZI and SJI represented the values over shallow water with seawater depths of ~7 m and ~2 m, respectively. Moreover, the critical wind speed at which CD peaked gradually decreased as the seawater depth became shallower in the coastal areas. CD at DHI and SYT decreased monotonously as U10 increased, similar to the pattern over the land. CD at DHI represented the value over the transition zone from shallow water to coastal land, and CD at SYT represented the value over the coastal land. Meanwhile, the eddy covariance method and the flux profile method were compared at ZZI and SYT during TC passages. It was found that their CD values obtained by the two methods were close. Finally, the parameterizations of observed u* and CD as a function of U10 over four different coastal areas were given under the influence of high winds. These parameterizations of observed C may be used in high-resolution numerical models for landfalling TC forecast.
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| 关 键 词： | high winds drag coefficient eddy covariance flux profile coastal areas |
| 收稿时间： | 2020-05-27 |
Characteristics of Drag Coefficient in Different Coastal Regions of the South China Sea Under Tropical Cyclones-An Observational Study |
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| YUAN Jin-nan,SONG Li-li,CHEN Wen-chao,ZHI Shi-qun,BI Xue-yan,LIU Chun-xia and HUANG Hui-jun. Characteristics of Drag Coefficient in Different Coastal Regions of the South China Sea Under Tropical Cyclones-An Observational Study[J]. Journal of Tropical Meteorology, 2020, 26(4): 417-427. DOI: 10.46267/j.1006-8775.2020.036 |
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| Authors: | YUAN Jin-nan SONG Li-li CHEN Wen-chao ZHI Shi-qun BI Xue-yan LIU Chun-xia HUANG Hui-jun |
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| Affiliation: | 1. Guangzhou Institute of Tropical and Marine Meteorology, CMA, Guangzhou 510641 China; 2. Public Meteorological Service Center, CMA, Beijing 100081 China; 3. Guangdong Climate Center, Guangzhou 510641 China |
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| Abstract: | To investigate the values of 10-m drag coefficient (CD) in different coastal areas under the influence of tropical cyclones, the present study used the observational data from four towers in different coastal areas of the South China Sea (SCS) during six tropical cyclone (TC) passages, and employed the eddy covariance method and the flux profile method. The analysis of footprint showed that the fluxes at Zhizai Island (ZZI), Sanjiao Island (SJI) and Donghai Island (DHI) were influenced basically by the ocean, and the flux at Shangyang Town (SYT) was influenced mainly by the land. The results showed that the dependence relationships of CD on 10-m wind speed (U10) in four different coastal areas under the influence of TCs were different. CD at ZZI and SJI initially increased and then decreased as U10 increased, similar to the pattern over the ocean. CD at ZZI and SJI represented the values over shallow water with seawater depths of ~7 m and ~2 m, respectively. Moreover, the critical wind speed at which CD peaked gradually decreased as the seawater depth became shallower in the coastal areas. CD at DHI and SYT decreased monotonously as U10 increased, similar to the pattern over the land. CD at DHI represented the value over the transition zone from shallow water to coastal land, and CD at SYT represented the value over the coastal land. Meanwhile, the eddy covariance method and the flux profile method were compared at ZZI and SYT during TC passages. It was found that their CD values obtained by the two methods were close. Finally, the parameterizations of observed u* and CD as a function of U10 over four different coastal areas were given under the influence of high winds. These parameterizations of observed C may be used in high-resolution numerical models for landfalling TC forecast. |
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| Keywords: | high winds drag coefficient eddy covariance flux profile coastal areas |
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