庆阳市连续2天短时暴雨特征及成因分析

Abstract

利用Micaps常规资料以及区域气象站降水观测资料，对2016年7月9~11日庆阳市短时暴雨天气过程的环流背景、中尺度特征及物理指数进行了分析。结果表明：1) 连续2天短时暴雨发生在稳定的大陆高压脊中。低槽切变线形成中低层辐合，东部型南亚高压前部急流形成高空强辐散，高、低空系统耦合使暴雨区有较强上升运动。台风“尼伯特”和副热带高压作用下，庆阳市水汽辐合，湿层明显增厚，切变线触发高温高湿能量，造成暴雨天气。2) 地面中尺度辐合线是触发暴雨的重要因子，其与强降水有很好的对应关系。3) “7.9”过程为中小尺度对流云团在降水区的更替造成，中高层 “干侵入”、低层暖平流明显，降水强度大。“7.10”过程为中小尺度对流云团合并为中尺度对流云带经过降水区造成，强降水影响范围广，持续时间长。4) 通过分析两次过程, 发现高层显著冷平流，中低层暖平流环境，以及稳定增强的高湿高能和上干下湿的不稳定层结均有利于庆阳短时暴雨的产生。 Using the Micaps conventional data and regional meteorological stations precipitation observa-tions, the author analyzed circulation background, mesoscale characteristics and physical index of short-time rainstorm in Qingyang from 9 to 11 July 2016. The results are as follows: 1) The short-time rainstorm on 2 consecutive days occurred in the stable continental anticyclone. A convergence at mid-low level was formed by the trough shear line, and a strong divergence in the upper was formed by jet on the eastern of South Asia High, and an ascend movement was formed over the rainstorm area by coupling of high-low system. The water vapor convergence and wet layer obviously thickened in Qingyang under the interaction of Typhoon Nepartak and the subtropical high, and the shear line triggered high temperature and high humidity energy, and caused rainstorm weather. 2) The surface mesoscale convergence line was an important factor in triggering rainstorm that corresponded well with short-time strong rainfall. 3) “7.9” rainstorm was caused by mesoscale convective cloud clusters replacement in the precipitation area. Dry intrusion in middle-high level and warm advection at low level were obvious, so that stronger precipitation intensity formed. “7.10” rainstorm was caused by mesoscale convective cloud clusters that were merged into the mesoscale convective cloud zone through precipitation area, so that it had wider range of influence and longer time duration. 4) Through two analysis processes, the author found upper significant cold advection, warm advection at lower environment, stably enhanced high humidity energy, dry and caused unstable stratification were advantageous to short-time rainstorm in Qingyang.