台湾地区中尺度试验期间梅雨锋及其对流云团的研究

本文对台湾地区中尺度试验(TAMEX)中的两次IOP(加密观测期)过程进行了诊断研究,结果表明: (1)1987年5月13日至17日,台湾地区的对流系统活跃.究其原因,主要系两次锋面过境所致.这两条锋面的温度梯度比长江流域一般的梅雨锋要强.梅雨锋上的对流云团与降水直接有关. (2)高空东移短波槽与梅雨锋的有利配合,是造成台湾地区出现较大降水的重要原因、IOP2有高空短波槽配合,因而降水比IOP1大、槽与锋面的配合,使对流层中低层正涡度区加强,这与华南前汛期暴雨的特征有某些相似之处。 (3)由每小时一次的GMS卫星云图上发现,在此期间台湾地区发展的对流云团与大陆的系统联系密切.此外,NCAR飞机落仪探测资料表明,与环境相比,云团内部有较深厚的湿层;时空加密探空资料的计算结果显示,700hPa以下的水汽主要来自水平方向的辐合,而在高层主要来自垂直输送.对于活跃的云团而言,上述特征更加明显.

A Study of Meiyu (Baiu) Front and Convective Cloud Clusters during TAMEX

In this paper, two processes of Meiyu fronts during TAMEX are diagnosed. The results show that:(1) The convective systems in Taiwan area during IOP1 and IOP2 are related to the passages of the Meiyu fronts . Temperature gradient of the fronts in these cases is stronger than that over the Yangtze River in summer.(2) The analysis of dropsonde data reveals that a deep moist layer existed inside the cloud clusters, and meanwhile, the computation of radiosonde data of denser network shows that the moisture below 700 hPa is associated with horizontal convergence and that in upper la -yers depends on the vertical advection.(3) The coupling between the trough at upper levels and the front at lower levels contrib-.utes to the maintenance and intensification of the positive vorticity near the Taiwan island. It isone of the important factors that cause or intensify the rainfall. It's similar to the heavy rain during pre-rain season in the mainland.