一次江淮气旋大暴雨的诊断分析和数值模拟

利用ERA Interim Daily的0.5°×0.5°资料对2011年6月9—10日的一次江淮气旋大暴雨天气过程进行天气学分析。结果表明:江淮气旋和低空急流是本次大暴雨过程的主要影响系统;高空200 hPa西风急流右侧的上升支和锋面的抬升作用提供了动力条件;低空西南急流提供了水汽条件,此次过程对流条件较好,具有较大的对流有效位能(Convective Available Potential Energy, CAPE);大气的对流不稳定性远大于斜压性,强降水发生在湿位涡正负值过渡的等值线密集带附近。过程最强降水时段由一次长生命史的中尺度飑线过程导致,利用WRF v3.9可以进行较好地模拟。研究飑线的环境条件和结构特征发现,环境大气具有较大的CAPE值和较小的对流抑制能(Convective Inhibition Energy,CIN),有利于对流的触发;较强的0~3 km垂直风切变,有利于飑线的维持;尽管冷池较浅薄,但冷池出流的抬升作用有利于对流的触发和飑线的维持。

Diagnostic analysis and numerical simulation of a heavy rainstorm associated with the Jianghuai cyclone

Based on the ERA Interim Daily data, a heavy rainstorm associated with the Jianghuai cyclone occurred during 9 to 10 in June 2011 was analyzed. Results show that the Jianghuai cyclone and the jet stream at high and low levels are the main influencing systems of the heavy rainstorm. The upward motion on the right side of the west jet stream at 200 hPa and frontal lifting provides uplift conditions for the occurrence of heavy rainfall; the low-level southwest jet stream transports water vapor. The convection condition of this event is good with a large CAPE value; the convective instability of atmosphere is far greater than the baroclinic instability and the strong precipitation occurrs in the vicinity of the dense zone of positive and negative values of MPV. The period of maximum precipitation in this process is caused by a long-lasting mesoscale squall line well reproduced by the WRF v3.9 numerical model. The environmental conditions and structural features of the squall line were analyzed,and the results show that the atmospheric environment has large Convective Available Potential Energy(CAPE) and small Convective Inhibition Energy(CIN), which is conducive to the triggering of convection; the atmospheric environment also has a strong vertical wind shear between 0-3 km, which is advantageous to the maintenance of squall line; although the cold pool of squall line was fairly shallow, the uplift by the cold pool is conducive to the triggering of convection and hence the maintenance of squall line.