利用NCEP/NCAR再分析资料和中尺度模式MM5V3， 对2010年7月造成甘肃东部大暴雨过程的低涡系统进行了诊断分析和数值模拟。结果表明： (1) 在低涡发生\, 发展阶段， 假相当位温和比湿的垂直平流在视热源、 视水汽汇中占绝对优势， 说明垂直平流变化与低涡发生、 发展及强降水有很好的正相关； (2) 上升运动中心与视热源、 视水汽汇大致中心相对应， 变化趋势基本一致， 最强的凝结潜热加热发生在中层， 最强上升运动同样也出现在中层， 说明降水过程中大气加热与大气上升运动密切相关， 大气热源主要来自于水汽的凝结潜热； (3) 低涡发生\, 发展过程中伴随中低层有西南风急流、 强正涡度中心、 低层辐合、 高层辐散结构、 强上升运动及低层水汽通量辐合； (4) 低涡区上空对流层低层为对流不稳定层结， 中层至中高层为条件对称不稳定层结， 对流不稳定层结强度随时间变化不大， 而条件对称不稳定层结强度随时间有明显加强， 位势不稳定和条件性对称不稳定共存使得假相当位温高值区域的垂直上升运动得以产生和维持。

Using the water vapor budget method and numerical experiment, the low vortex system that resulted in a heavy rainstorm in Eastern of Gansu Province in July 2010 was analyzed. The result  show that:  (1) At development stage of the low vortex,  the vertical advection of potential pseudo-equivalent temperature and specific humidity have absolute advantage in the apparent heat source and apparent moist sink, it indicates  that  the vertical advection has positive correlation with the development of low vortex and heavy rainstorm. (2) The center of ascending motion is corresponding to the apparent heat source and apparent moist sink, and they have the same change trends, it indicates that  the atmospheric heating is closely related to ascending motion during process of precipitation，and the atmospheric heat source come from the condensation latent heat releasing. (3) The development of low vertex is accompanied with low-level southwest jet,  strong center of positive vorticity， low-level convergence, high-level divergence, strong ascending motion and low-level moisture flux convergence. (4) There are convectived instability at the low-level which has no significantly change with time, and conditional symmetric instability at the mid to mid-high level has significantly strengthen. Potential instability and conditional symmetrical instability result in the producing and maintain of the vertical ascending movement in big value area  of potential pseudo-equivalent temperature.