选取2007年和2009年发生的4个季风低压个例,利用FNL资料和CMORPH卫星反演的降水资料,采用多尺度环流分析法,对西北太平洋季风环流的多尺度特征进行了分析,研究季风低压对台风生成的可能影响。分析发现:季风低压生成于季风槽中,其天气尺度波列的气旋性环流中。虽然以季风槽为特点的低频环流为台风生成提供大尺度气候条件,但是季风低压通过进一步提供较大的正相对涡度,可以有效减小Rossby变形半径,促进热带低压中中尺度对流系统的相互作用和合并,有利于台风的生成。
By using the FNL data and CMORPH precipitation data and based on the multiscale circulation analysis,four monsoon depressions in 2007 and 2009 were selected to analyze the multiscale characteristics of monsoon circulation in Northwest Pacific. Moreover,the possible effects of monsoon depression on tropical cyclogenesis were also explored. Results show that the monsoon depressions usually develop in the cyclonic circulation with synoptic-scale wave trains originated from the monsoonal confluence zone of the monsoon trough. Although the low-frequent circulation characterized by monsoon trough provides large-scale climatic conditions for tropical cyclones genesis,the monsoon depression contributes additional positive vorticity to enhance the merger of mesoscale convective systems by reducing the Rossby radius of deformation.