摘要
根据南海季风试验期间“科学１号”和“实验３号”在加密观测期间所得到的１天４次的探空观测资料，分析了南海季风爆发前后大气层结和混合层的演变特征。结果表明：（１）南海北部季风爆发的日期是５月１７日，而南海南部季风爆发的日期是５月月～２２日左右，季风爆发在南海北部表现出与南部明显不同的特征，其突然的爆发性更为显著。（２）南海季风爆发前后，混合层高度的变化在南海南部与南海北部有明显的不同。在季风爆发前，都存在着明显的混合层，但其厚度不同。南海南部混合层的高度变化在 ９３０～９７０ ｈＰａ范围内，而南海北部偏高，约为 ９００～９８０ ｈＰａ。随着季风的爆发，混合层厚度减小，甚至消失。（３）南海季风爆发前后对流层中低层表现出明显不同的层结结构。季风爆发前，空气比湿较小，大气稳定，混合层顶高度较高，在对流层中存在一个明显的干层。随着季风的爆发，干层逐渐减弱，或趋于消失。这主要是由于季风爆发后，西南季风把大量暖湿空气输送到南海地区，对流活动增强，大气呈现不稳定层结并伴有降水发生的结果。
Based on the sounding data four times a day observed on R / V 'Kexue 1' and R/ V 'Shiyan 3' during the South China Sea Monsoon Experiment (SCSMEX), the evolution of the atmospheric stratification and mixed layer before and after monsoon onset over the South China Sea (SCS) were analyzed. The results was as follows: (1) The date of monsoon onset over the northern SCS was on May 17, whereas the date over the southern SCS was on May 21 to 22 or so. The monsoon onset over the northern SCS was greatly different from the southern SCS and its abrupt onset was more prominent. (2) Before and after monsoon onset over the SCS, the height of the mixed layer over the southern SCS was obviously different from northern SCS. Before the monsoon onset, the mixed layer existed on both parts of the SCS, but the height was different. For the southern SCS, the mixed layer varied from 940 to 975 hPa, while for the northern SCS, the height of the mixed layer was a bit higher, about 900 to 980 hPa. With the monsoon onset, the height weakened and even disappeared. (3) Before and after monsoon onset over the SCS, the evident different stratification structure appeared in the middle and low troposphere. Before monsoon onset, the humidity of air was relatively low, the atmosphere was stable and the ceiling height of the mixed layer was relatively high, which suggested an obvious dry layer existed in the middle troposphere. With the monsoon onset, the dry layer gradually weakened or even tended to disappear. After the monsoon onset, the southwesterly monsoon transported the volume of warm and wet air to the SCS and the convection enhanced. So, the stratification was unstable and precipitation was also falling.
出处
《气候与环境研究》
CSCD
2000年第4期459-468,共10页
Climatic and Environmental Research
基金
国家科技部攀登项目A"南海季风试验研究"资助
