中文摘要：

2010年8月10～13日，甘肃省河东出现了中到大雨，局地暴雨或大暴雨，是舟曲山洪地质灾害气象应急响应开始后迎来的第一场区域性暴雨过程，对前方救灾抢险工作造成严重威胁。利用实况观测资料和NCEP再分析资料对大暴雨过程的天气特征、水汽条件、动力条件、不稳定条件等进行综合分析，并总结了暴雨过程的中尺度云团特征及雷达回波特征。结果表明：此次暴雨过程持续时间较长，但大暴雨出现时段集中，雨强大，危害性强。副高强盛，北部冷空气分裂南下，青藏高原切变线活动频繁，是本次暴雨过程的主要环流特征。500hPa锋区和700hPa低涡切变线是造成暴雨天气的直接影响系统。低层正涡度区、水汽辐合、上升运动、正螺旋度中心以及层结不稳定等因素为暴雨产生创造了热力、动力和能量条件。此次暴雨的触发机制是低层中尺度切变线的发展和维持、偏南暖湿气流的增强，以及低层辐合高层辐散的大气上下层抽吸作用。多个中p尺度对流云团沿700hPa切变南侧发展东移，表明本次大暴雨过程中存在明显中小尺度系统，其中低层气旋式辐合、高层辐散流场的配置是降雨范围及强度增大的重要原因。

英文摘要：

The prediction for heavy rainfall in northeastern Tibetan Plateau is of vital importance in the work for disastrous weather forecast around northwest Region of China. There are many regional heavy rainfall and local severe convection in Gansu province which result in geological disasters in high frequency in early and middle August in 2010. The heaviest rainfall in flood season in 2010 was the one happened in 11 13 Aug in the east of the Yellow River in Gansu, which is famous for its intensity, coverage and duration. Several characteristics from different as pects of this heavy rainfall event were comprehensively analyzed based on the observed station data and NCEP re analysis data, such as precipitation condition, circulation background, moisture conditions, dynamic condition and convective instability factor. Besides, the characteristics of the mesoscale cloud cluster and the radar echoes were summarized. The results show that： （ 1 ） Even though the event lasted for a long time, the heaviest section just oc curred in a short time with a strong intensity and destructive damages. The main circulation background, which in cludes strong subtropical high, southward action of northern cold air and active Tibetan Plateau shear lines, is favor able for the formation of the rainfall. （2） The direct influence systems are the front at 500hPa and the low vortex with shear line at 700hPa. （3）The properly configuration of many factors provides a good condition for developing a rainfall in dynamic, thermodynamic and energetic environmental conditions, these factors include low level vortex maximum, water vapor convergence, ascending motion, positive helicity center and instable energy of stratification. （4）The trigger mechanism of the rainfall is the development of the mesoscale shear line on the low level, the quick strengthened warmmoist air from the southwest and the suction action of the atmosphere. During 02 - 08 on August 12, The shear line in the middlesouthern Gansu developed and then led to the h