川渝地区一次短时强降水天气的集合敏感性分析

为了加深对川渝地区短时强降水天气的认识，为提高业务预报技巧及改进数值模式提供参考，选取了川渝地区一次短时强降水天气过程，基于对流尺度集合预报系统，开展了目标区域平均降水量对模式初值的集合敏感性分析,并探讨了相应的动力学机制。主要结论如下：敏感区的分布与对目标区域降水起到关键影响作用的系统有较好的对应：850 hPa和700 hPa西南低涡周围的敏感区呈现出正负相间的分布特征，500hPa低压槽左（右）侧为负（正）敏感区，250 hPa高空西南急流区域（南侧）为正（负）敏感区，中低层与锋区前（后）部对应区域为正（负）敏感区。说明西南低涡周围负（正）敏感区的西北（东南）风越强,低压槽左（右）侧西北（东南）风越强，高空急流区域（南侧）西南（东北）风越强以及锋前（后）温度越高（低），则越有利于西南低涡内的辐合上升运动，500 hPa低压槽的加强，250 hPa高空辐散的加强，锋区温度梯度增大以及锋面抬升作用加强等并对目标区域的降水产生正面的影响。

Ensemble Sensitivity Analysis on a Short-Time Severe Rainfall Event Occurred in the Area of Sichuan and Chongqing

This article aims to understand the short-time severe rainfall events in the area of Sichuan and Chongqing more comprehensively, and provide references for improving operational forecast skills and numerical weather forecast skills. Based on a convection-scale ensemble forecast system, a short-time severe rainfall event that occurred in the area of Sichuan and Chongqing is selected, and then the ensemble sensitivity analyses of the average precipitation in the target region to the model initial values are carried out and the corresponding dynamic mechanisms are discussed. The results show that the distribution characteristics of sensitive areas correspond well with the synoptic systems that play a key role in the precipitation forecast of the target regions. The sensitive areas around the southwest vortex at 850 hPa and 700 hPa show positive and negative distribution characteristics, the left (right) side of the 500 hPa trough shows negative (positive) sensitive area, the high-level southwest jet area at 250 hPa (south side) shows positive (negative) sensitive area, and the corresponding areas corresponding with the front (back) of the front zone of the middle and low layers show positive (negative) sensitive area. These findings indicate that the stronger the northwest (southeast) wind in the negative (positive) sensitive area around the southwest vortex, the stronger the northwest (southeast) wind on the left (right) side of the trough, the stronger the southwest (northeast) wind in the upper jet stream zone (south), and the higher (lower) the pre-frontal (post-frontal) temperature is, the more favorable they are to the convergence upward movement in the southwest vortex, to the strengthening of the 500 hPa trough, to the strengthening of the 250 hPa divergence, to the increase of the temperature gradient in the frontal zone and to the strengthening of the frontal uplift, which finally result in positive impacts on the precipitation in the target regions.