2017年7月吉林永吉两次极端强降水过程的对比分析

Comparative Analysis on Two Extreme Severe Precipitation Events in Yongji County, Jilin Province in July 2017

2017年7月13-14日和19-21日吉林省永吉县发生了两次极端强降水天气过程,为研究它们的影响机制及差异,采用ERA-Interim 0.5°×0.5°逐6 h再分析资料、常规气象观测资料、FY-2E卫星TBB资料,对大尺度环流背景、高低空急流的演变、物理量场的配置和TBB云图进行对比分析。结果表明:(1)第一次过程受西北气流与西南低空急流的强辐合影响,第二次过程受东北气流与西南低空急流的切变线影响。(2)第一次过程的低空急流更强,水汽含量更充沛,高空急流有较强的抽吸作用。(3)永吉县的最强降雨时段在第一次过程受低层暖湿空气加强与中层干冷空气发生作用的影响,在第二次过程受中层干冷空气向下侵入低层的影响。(4)永吉县的短时强降雨在第一次过程受TBB≤-50℃或-60℃的强对流云团影响,在第二次过程中,前期TBB≤-50℃,之后对流逐渐减弱。

Two extreme severe precipitation weather events happened in Yongji County, Jilin Province on 13-14 and 19-21 in July 2017. In order to research their influence mechanisms and differences, based on ERA-Interim 0.5°×0.5° 6 hourly reanalyzed data, the conventionally observed dataand FY-2 E satellite TBB data,analyzedthe largescale circulation background, the evolution of upper and lower-level jets, the configuration of physical quantities and TBB cloud images. The results show that:(1)The first eventwas influenced by the strong convergence of the northwest current and the southwest low-altitude jet stream.The second eventwas influenced by the shear line of the northeast current and the southwest low-altitude jet stream.(2)In the first event, the low-altitude jet stream was stronger, the water vapor was more abundantand the high-altitude jet stream had stronger suction effect on rainstorm area.(3)The period of maximum precipitation at Yongji County in the first event was influenced by the interactionbetween theenhancedwarm-wet air in the lower layer and dry and cold air in the middle layer.In the second event,it was influenced by the dry and cold air in the middle layer down into the lower layer.(4)The short-term strong precipitation in Yongji County were influenced by severe convective cloud cluster with TBB≤-50 ℃ or-60℃ in the first process, and in the second process, the early TBB≤-50 ℃,then the convection gradually weakened.