Based on NCEP reanalysis data and WRF model, circulation feature analysis and numerical simulations are carried out for the extreme torrential rain in Yunyang on 31 August 2014. Considering to the terrain in Chongqing area, three terrain sensitivity tests are designed. It is indicated that the accumulative instable energy in low-latitude region spreads northwards, with the vertical perturbations of terrain and jet, convection develops intensively, low-level jet at 850 hPa transports water vapor from the South China sea to Chongqing region, the suction caused by the structure of"high level divergence and low level convergence"lead to the vertical transportation of water vapor. With the reduction of the height of Daba mountains, the thickness of the instable energy region gets thinner, which weakens the intension of convection. The decrease of the mountain blocking goes against the convergence of water vapor in the heavy rain area. The decrease of the intension of water vapor convergence and divergence get weaker lessens the vertical transport of water vapor. With the reduction of the height of Qiyue mountains, the vertical perturbation which caused by the low-level jet moves southwards further, and the location of high energy tongue and convection are southward. The center of the water vapor transport moves southwards, water vapor channel gets wider, which decreases the water vapor transport over the rainstorm area. The location of low-level jet leans southwards, the water vapor convergence occurs later.%利用NCEP再分析资料和WRF模式,对2014年8月31日重庆市云阳县特大暴雨进行形势分析和数值模拟,针对重庆地区地形设计了三组地形敏感性试验,分析地形改变对暴雨过程热力条件和水汽条件的影响. 结果表明:低纬地区不稳定能量大量积聚并向北传播,在地形和急流的垂直扰动触发下,对流强烈发展;850 hPa低空急流将来自南海的水汽输送至重庆地区,水汽低层辐合、高层辐散形成的抽吸作用引发水汽的垂直输送. 大巴山高度降低后,不稳定厚度减小导致对流强度明显降低;阻挡作用降低不利于水汽在暴雨区的汇聚;水汽辐合、辐散的强度降低导致水汽的垂直输送强度明显减弱. 齐岳山高度降低后,低空急流所引起的垂直扰动位置偏南导致高能舌和对流活动位置偏南;水汽输送中心南压,水汽通道变宽导致暴雨区上空水汽输送减弱;低空急流位置偏南导致其所引起的水汽辐合时间偏晚.
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