Characteristics of Drag Coefficient in Different Coastal Regions of the South China Sea Under Tropical Cyclones–An Observational Study

IF 1.5 4区 地球科学 Q4 METEOROLOGY & ATMOSPHERIC SCIENCES
Yu Jinnan, Song Li-li, Chen Wen-chao, Zhi Shi-qun, Bian Xueyan, Liu Chun-xia, Huangfu Hui-jun
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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 CD may be used in high-resolution numerical models for landfalling TC forecast.
热带气旋作用下南海不同沿海地区阻力系数特征的观测研究
为了研究热带气旋影响下南海不同沿海地区10-m阻力系数(CD)的变化,本文利用南海不同沿海地区4座塔6次热带气旋通过的观测资料,采用涡旋相关方差法和通量剖面法。足迹分析表明,直仔岛(ZZI)、三角岛(SJI)和东海岛(DHI)的通量主要受海洋的影响,上阳镇(SYT)的通量主要受陆地的影响。结果表明,在TCs的影响下,4个不同沿海地区的CD对10 m风速(U10)的依赖关系不同。随着U10的增加,ZZI和SJI的CD先升高后降低,与海洋上空的模式相似。ZZI和SJI的CD分别代表海水深度为~7 m和~2 m的浅水上的值。在沿海地区,随着海水深度变浅,CD达到峰值的临界风速逐渐降低。随着U10的增加,DHI和SYT的CD单调降低,与陆地上的模式相似。DHI和SYT的CD分别代表浅水和沿海过渡带的CD值和CD值。同时,比较了涡动相关法和通量剖面法在齐、西两处的变化。结果表明,两种方法所得的CD值接近。最后,给出了在大风影响下四个不同沿海地区观测到的u*和CD随U10的函数的参数化。观测到的CD的这些参数化可以用于高分辨率的数值模式,用于预报TC的着陆。
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来源期刊
热带气象学报
热带气象学报 METEOROLOGY & ATMOSPHERIC SCIENCES-
CiteScore
1.80
自引率
8.30%
发文量
2793
审稿时长
6-12 weeks
期刊介绍: Information not localized
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