中文摘要：

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。

英文摘要：

Based on the datasets from NCEP and the South China Sea（SCS） air-sea flux measurement which was carried out from April,2008,the air-sea fluxes were calculated with COARE3.0 algorithm,and the characteristics of the weather and how the air-sea fluxes varied with the variations of atmosphere and ocean elements before and during the onset of the SCS monsoon were discussed.The results indicated that,the onset of the SCS monsoon in the 2008 appeared firstly in the southern part of SCS at early May,and then owing to influence of a tropical cyclone the onset of monsoon in the northern part of SCS was remitted to 18th May.Influence of the onset of monsoon and tropical cyclone activity on wind speed and air-sea fluxes was remarkable.By comparison,influence of the tropical cyclone activity on air-sea fluxes was stronger.Before the tropical cyclone,the latent heat flux and sensible heat flux and momentum flux were quite low.During the tropical cyclone and the onset of SCS monsoon,the latent heat flux and momentum flux increased greatly because of the strong wind while the sensible heat flux increased in the days when it rained.The momentum flux maximized during the tropical cyclone and was twice bigger than that before the onset of SCS monsoon.The latent heat flux was sixteen times as much as the sensible heat flux during the entire observation.In different types of weather,the latent heat flux had similar diurnal distribution while the sensible heat flux varied a lot.Besides,the close correlation between the transfer coefficients and wind speed was found.