横断山脉南侧“春汛”期2次强降水天气过程对比分析

Comparative Analysis of Two Heavy Precipitation Processes of "Spring Flood" Period in the South Side of the Hengduan Mountains

利用NCEP/NCAR(1°×1°)再分析资料和云南省怒江州105个自动站常规降水资料,从大尺度环流背景、水汽条件、动力条件和地形影响方面,对怒江州2016年"春汛"期2月21—22日和4月12日的2次强降水天气过程进行综合分析。结果表明,这2次强降水过程均由小波动东移造成,500 hPa西风气流强劲,700 hPa滇缅间形成强烈风速辐合,"0221"过程小波动移速缓慢,500 hPa风速和700 hPa辐合也比"0412"过程强,因此造成的降水强度更强,范围更广,影响更大。在2次强降水过程中,怒江北部一直都处于强水汽辐合带内,水汽条件较好,且在降水区对应低层为辐合、高层为强辐散,上升运动强烈,有利于强降水的发生和维持。怒江州处于滇缅过渡的迎风坡地带,怒江北部又处于青藏高原和云贵高原结合部的"喇叭口"地形底部,西移的系统和暖湿气流在"喇叭口"的引导下经迎风坡地形强迫抬升形成强降水,地形在这2次降水过程中均起到了至关重要的作用。

Using NCEP/NCAR（1°×1°） reanalysis data and the conventional precipitation data of 105 automatic stations in Nujiang Prefecture,the two heavy precipitation processes in February 21-22 and April 12 in the ＂Spring flood＂ period of the Nujiang Prefecture in 2016 were comprehensively analyzed from the large scale circulation background,water vapor condition,dynamic conditions and terrain influence.The results showed that the two strong precipitation processes were caused by small fluctuations eastward movement,west wind flow on 500 hPa was strong,a strong wind speed convergence on 700 hPa between Yunnan and Burma was formed.The small fluctuation of ＂0221＂ process was moving slowly,then the wind on 500 hPa and the convergence situation on 700 hPa were more obvious than ＂0412＂process.Therefore,the precipitation intensity was stronger,the scope was wider,and the influence was bigger.During the two heavy rainfall processes,north of Nujiang had been in the a strong water vapor convergence zone,water vapor condition was very abundant.And corresponding to the precipitation area,the low level was convergent,the upper level was divergent strongly,upward movement was strong,it was conducive to the occurrence and maintenance of heavy rainfall.Nujiang is located in the windward slope zone which is on the transition of Yunnan and Burma.The north of Nujiang is in the bottom of ＂labakou＂ terrain which was located in the Qinghai Tibet Plateau and Yunnan Guizhou Plateau junction.Systems and warm moist air westward flow in the ＂labakou＂ under the guidance of the windward slope topography uplift formed strong precipitation.The terrain plays an important role in these two precipitation processes.