青藏高原东坡两次暖区强降水的对比分析

利用常规观测资料、加密自动站降水资料和NCEP 1°×1°再分析资料对比分析了2010年8月12～13日(简称“8·12”过程)和2012年8月16～17日(简称“8·16”过程)青藏高原东坡发生的两次暖区强降水过程,探讨两次暖区强降水发生发展的天气学异同条件。结果表明:两次暖区强降水发生前及过程中均受副高的影响,地面有热低压发展和维持,利于能量的积累、不稳定层结和非绝热加热形成,进而引起上升运动;过程期间低层均有垂直于青藏高原东坡的偏东南气流的建立与增强,地形强迫上升运动和低层暖平流引起的上升运动增大和维持。主要差异在于,“8·16”过程中台风“启德”外围的偏东南风持续时间更长,影响区域更偏北,其降水持续时间更长,累计雨量更大。两次暖区强降水过程显示,低层垂直于青藏高原东坡地形的偏东南气流的建立、增强、持续及减弱在此类暖区强降水发生、发展及消亡过程起中着关键性作用。 

Comparison Analysis of Two Warm Sector Torrential Rain Weathers on the East Side of Tibetan Plateau

Two warm sector torrential rain processes in 12 ~ 13 Aug,2010(“8 · 12 ”) and 16 ~ 17 Aug,2012(“8·16”) between the east side of Tibetan Plateau and the Sichuan Basin are analysed based on the conventional observation data,precipitation data of automatic weather stations and NCEP 1°×1° reanalysis data. The similar and different features of weather conditions are compared. The results indicate that there is no cold air but warm low pressure near the surface and West Pacific subtropical high at 500 h Pa before the two torrential rains occur and also in the process,the atmospheric were have unstable stratification and high energy. Two processes have the same trigger mechanisms,which includes the diabatic heating at complex terrain,the warm advection in the lower in the Sichuan Basin and orography dynamic lifting. Meanwhile,the main difference between two warm sector processes is the southeast wind in the lower. In the “8 ·16 ”process the southeast wind comes from the northeastern of Typhoon KAITAK,which have longer influence time and more northward than “8 · 12 ”process. The warm advection in the lower,orography dynamic lifting and torrential rain have the same Characteristics of the southeast wind. Analyzing those two processes,it is found the key point to the warm sector torrential rain systems between the east side of Tibetan Plateau and the Sichuan Basin lie in the building,enhancement and maintaining of the southeast wind in the lower.