民勤春季强降水过程的气候特征及其成因

干旱区春季强降水对安排春耕播种生产、缓解风沙危害和春旱、净化空气质量、改善生态环境和促进农作物生长具有十分重要的意义。以1953-2015年民勤春季3-5月降水为背景，针对2001-2015年春季日降水量≥5 mm强降水天气过程，综合运用地面、高空和云图等气象资料，以及NCEP再分析资料，通过12个春季典型干湿年对比分析，得出春季强降水过程的气候特征和成因。1953-2015年民勤春季强降水日数和降水量呈增加趋势，过程特点是降水时间长，集中在上午，多为连续降水。新疆至河西冷空气东移南下，与青藏高原低值系统、深厚湿层共同影响，生成高原云系发展北抬造成民勤春季强降水。春季强降水的发生，与欧亚纬向气流、高原低槽和东亚大槽的强度密切相关。预报关注重点是西北冷空气、高原天气系统和云系、偏南气流水汽输送。

Climate Characteristics and Cause of Spring Strong Precipitation Processes in Minqin,Gansu, China

Strong rainfall in spring has very important significance for spring sowing arrangements, sandstorm and drought harm alleviation, air quality and ecological environment improvement and crop growth in arid areas. The strong precipitation processes with daily precipitation≥5 mm in spring in Minqin from 2001 to 2015 were studied based on the meteorological data of the ground, upper air and cloud, as well as NCEP reanalysis data. The number of strong rainfall days in spring and total precipitation showed increasing trends during 1953-2015 in Minqin, and the characteristics of processes were long precipitation time, high concentration in the morning and mostly continuous precipitation. The strong rainfall processes were caused by cold air moved eastward south from Xinjiang to the Qinghai Tibet Plateau, combined with low-pressure systems over the Qinghai-Tibet Plateau and deep moist layers, plateau clouds that developed northward. The occurrence of strong precipitation in spring is closely related to the Eurasian zonal flow, the intensities of the Qinghai-Tibet Plateau low trough and the East Asian trough. The weather forecast focus are cold air come from northwest of China, weather systems and clouds over the Qinghai-Tibet Plateau, southerly water vapor transportation.