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基于2008年4至5月在南海西沙永兴岛进行的海气通量观测试验资料和NCEP资料,应用COARE3.0通量算法计算了海气通量,分析了季风爆发前后西沙海域天气变化特点和海气通量对南海季风爆发的响应。结果表明:2008年南海季风首先于5月第1候在南海南部爆发,受热带气旋等因素的影响,北部海区季风爆发推迟到5月18日。季风爆发和热带气旋活动对西沙海域的风速和海气通量影响较大,其中热带气旋的影响更强烈。热带气旋来临之前,潜热通量、感热通量以及动量通量均较小;在气旋活动及此后的季风爆发时期,大风使潜热通量和动量通量显著增强,感热通量则在降水期间变化明显;动量通量的最大值出现在热带气旋活动期间,其在此过程中的均值是观测初期均值的3倍以上。在整个观测过程中,潜热通量明显大于感热通量,后者是前者的16∶1。不同类型天气过程中,潜热通量的日变化相似,而感热通量的日变化有差异。湍流交换系数与风速有较好的相关关系。
Based on the air-sea flux observation data and NCEP data conducted at Yongxing Island, Xisha, South China Sea, from April to May 2008, the COARE3.0 flux algorithm was used to calculate the air-sea flux and the characteristics of the Xisha air before and after monsoon onset were analyzed And the response of sea-air flux to the onset of the South China Sea monsoon. The results show that in 2008, the monsoon of the South China Sea first broke out in the southern part of the South China Sea in the first part of May. Due to the influence of tropical cyclone and other factors, the monsoon onset in the northern sea area was postponed until May 18. The monsoon onset and the tropical cyclone activities have a great influence on the wind speed and the sea-air fluxes in the Xisha sea area, with the impact of the tropical cyclones being stronger. Before the advent of the tropical cyclone, the latent heat flux, the sensible heat flux and the momentum flux were all small. During the cyclone activity and subsequent monsoon onset period, the gale significantly increased the latent heat flux and momentum flux, while the sensible heat flux decreased with the precipitation During the period of tropical cyclone, the mean value of momentum flux appeared more than 3 times of the average value during the initial period of observation. In the whole process of observation, the latent heat flux is obviously greater than the sensible heat flux, which is 16: 1 of the former. In different types of weather, the diurnal variations of latent heat flux are similar, while the diurnal variations of sensible heat flux are different. Turbulent exchange coefficient and wind speed have a good correlation.