考虑飞沫影响的拖曳系数方案对台风条件下上层海洋海温数值模拟的影响

The influence of a new drag coefficient scheme considering sea spay on numerical simulation of upper-ocean temperature response to tropical cyclone

为了提高对上层海洋的模式模拟准确性,为台风海气耦合模式提供更加合理的动量交换耦合方案,文章应用一个分粒径段的海洋飞沫函数给出一个新的海面拖曳系数CD计算方案,它体现了台风高海况条件下海洋飞沫层使海面拖曳系数数值减小特点。论文以2014年第15号台风"海鸥"经过南海强化观测区域时段作为个例,应用POM(Princeton Ocean Model)三维海洋环流模式进行数值模拟试验,结果发现低风速情况下,考虑海洋飞沫因素后的CD与传统计算方案数值相近,在高风速情况下,考虑海洋飞沫因素后的CD方案与模式传统计算方案不同,表现出随风速增长趋缓,直至随风速略有下降现象。与传统拖曳系数方案相比,采用新的拖曳系数方案后,模拟的台风条件下上层海洋的温度降温幅度、混合层深度加深幅度、温跃层强度减弱程度都略有减弱,这些模拟特征与观测事实更加接近。

To improve model forecast of upper ocean and offer a more proper momentum exchange scheme for an air-seacoupling model,a new drag coefficient scheme of CD considering sea spay layer on the surface is established and is used in thethree-dimensional oceanic circulation model of the Princeton Ocean Model(POM).A case of tropical cyclone Kalmaegi in2014is selected,which passed through the center of a buoys array set up by our field experiment in the northern South ChinaSea.Observation data were collected for both atmosphere and ocean in the process,and are used to verify the modelsimulation.It is found that the drag coefficient CD under low wind condition is consistent with the traditional CD scheme.However,they are different from each other under high wind condition with CD increasing slowly,even decreasing slightly,ifsea spay process is considered by the new CD scheme.Furthermore,numerical experiments are conducted using the POM.Theresults show that the responses of upper ocean on temperature are more reasonable with a weaker cooling rate of oceantemperature and thermocline strength,and smaller deepening of mixed layer depth in the upper ocean if the new dragcoefficient scheme is used.