夏季风系统影响下广西锋面型强暴雨动力及水汽输送特征

Dynamic and Moisture Characteristics of Frontal Heavy Rains under Summer Monsoon System over Guangxi

利用日本气象研究所高分辨TBB资料、美国环境预测中心（NCEP）再分析资料,对1980～2002年主汛期（5～7月）夏季风系统影响下的广西13次锋面型大范围暴雨过程,采用合成分析与个例探讨的方法,分析了暴雨期间东亚夏季风各系统（高空急流、低空急流、南亚高压等系统）的演变特点和强暴雨的动力及水汽特征.结果表明：大范围暴雨发生时,广西位于高空急流出口右侧正散度区和500 hPa强上升区内,同时还位于低空急流的左侧,高低空急流耦合是暴雨触发机制;对湿位涡的分析表明,当700 hPa附近的湿位涡垂直分量小于0同时湿位涡在等压面上的垂直分量大于0时较易产生大暴雨.

By means of high-resolution MRI TBB data and NCEP reanalyzed data, an analysis is made of 13 frontal large-scale rainstorm processes influenced by the summer monsoon system in flood season （May to July） from 1980 to 2002 in Guangxi Autonomous Region. Through composite analysis combining with case studies, the evolutionary characteristics of the influencing systems （upper-level jet, low-level jet, South Asia High, etc. ） and the dynamical and vapor characteristics of rainstorms are analyzed by using the high-resolution TBB data. The results indicate that Guangxi locates, during rainstorms, in the positive divergent area within the right exit region of the high-level jet, the intensive updraft region at 500 hPa, to the left side of the low-level jet ; the coupling between high-level and low-level jets is the trigger mechanism of rainstorms; further more, the analysis of wet potential vorticity indicates that heavy rainstorms are more likely to occur while the vertical component of moist potential vorticity being less than 0 and the vertical component of moist potential vorticity at the isobaric surface being greater than 0 near 700 hPa.