黄海及周边地区α中尺度对流系统发生的环境条件

ENVIRONMENT OF MESO α- SCALE CONVECTIVE SYSTEM DEVELOPMENT IN YELLOW SEA REGION

使用日本GMS - 5静止卫星红外云图普查了 1993年 7、8月份黄海及周边地区α中尺度对流系统 (MαCS)的发生情况 ,并用合成和客观分析诊断的方法考察MαCS两个活跃期和两个静寂期的大尺度环境场的热力和动力条件。结果表明 ,MαCS活跃期和静寂期的合成诊断场有显著的不同 ,从而揭示了黄海地区发生MαCS的环境条件主要为 :①低层为高相当位温的暖湿空气 ;②中低层的条件性不稳定的大气层结及暖平流 ;③强而稳定的西南低空急流 ;④低层的辐合及中层不太强的上升运动 ;⑤副热带西风急流出口区右侧的高层辐散。

Based on the GMS-5 satellite IR images, the meso α-scale convective systems (MαCS) were investigated in July and August 1993. The composite synoptic environment was examined for two active-MαCS periods and two null MαCS Periods in 1993 to diagnose the large-scale dynamical and thermal conditions for the development of MαCS over the Yellow Sea region. The distinct contrasts were revealed in the composite diagnostic fields between the active-and null-MαCS periods. The large-scale environment favorable for the MαCS development in the Yellow Sea region was obtained as follows: the low-level air with the high equivalent potential temperature, the conditionally unstable atmospheric stratification, the large amount of water vapor conveyed into the MαCS active region by the intense and steady low-level southerly jet stream, the mild ascending motion accompanied by the lower-tropospheric warm advection, and the upper-level divergence related to the diffluent flow on the right side of the exit of the subtropical jet.