冬季风期(11月-翌年3月)南海显著的气候特点是盛行东北季风并频繁地发生冷涌天气过程.使用2008年10月到2009年4月在西沙群岛永兴岛近海进行的海-气通量观测试验资料,分析了西沙海域冬季风期,尤其是冷涌时段的海-气通量交换和热量收支特征.结果表明:冬季风前期由于海-气温差增大,感热通量比西南季风期稍增加；潜热通量平均值与西南季风期接近；太阳总辐射明显降低,大气长波辐射减小,海洋热量净收入成为负值,使得秋季之后海面温度不断降低.冷涌期间海-气之间的感热通量高于冬季风期平均值,潜热通量大部分(1月份之前)也高于冬季风期平均值；由于潜热通量增大和太阳短波辐射减小,1月份之前的冷涌过程海洋热量净收支普遍出现较大负值,海洋失热量强于冬季风期,甚至强于2008年台风过程平均值.到了冬季后期太阳总辐射增强,海洋热量净收入转为正值,海水温度又逐渐升高.季节之间比较,观测区感热通量以冬季风期间最大,秋季次之,春季最小；而潜热通量夏季风期出现最大值,冬季次之,秋季最小.%The significant climate characteristic in the South China Sea (SCS) during winter monsoon is that northeast monsoon is the prevailing wind and cold surges frequently occur. The features of sea-air heat flux and budget during the winter monsoon, especially during the cold surges, were studied,based on the data collected from the sea-air flux experiment in Yongxing Island, SCS, from October 2008 to April 2009. The results showed that:the sensible heat (SH) flux slightly increased during the prophase of winter monsoon with the increase of temperature difference between air and sea s compared to that during summer (southwest) monsoon. The average latent heat (LH) flux during winter monsoon was almost equal to that during the summer (southwest) monsoon. The total solar radiation decreased significantly, and the long wave radiation of the atmosphere also decreased,as a result,the net heat budget of the sea became negative value, which caused the sea surface temperature (SST) dropping after autumn. The SH fluxes during the cold surges were higher than the average flux during the winter monsoon,and before January,most of the LH fluxes during the cold surge were also higher than the average flux of winter monsoon. Due to the increase of SH flux and the decrease of solar radiation,the net heat budgets of the sea,during the cold surges before January,generally turned into high negative value,which caused the sea losing more heat than during winter monsoon,and even more than the average heat loss of the typhoons in 2008. At the end of winter monsoon,while the total solar radiation increased,the net heat budget of the sea turned to positive,so the SST increased gradually. Among all seasons,the SH flux in winter monsoon was the largest,the second largest in autumn,and the minimum in spring. The LH flux was the largest during summer monsoon,the second largest in winter,and the minimum occurred in autumn.
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