摘要:利用ERA-Interim再分析资料、常规气象观测资料、CMORPH（CPC MORPHing technique）融合降水资料以及WRF（Weather Research and Forecasting）高分辨率数值模拟结果，对2017年7月13～14日吉林地区的极端降水天气过程的环流背景和触发机制进行了分析。结果表明：（1）东北冷涡环流控制下，副高北抬与中纬度锋区形成了有利的大尺度环流背景。降水发生在冷涡底部与副高之间的平直纬向环流中，东北冷涡南部的低槽、低空切变线、高低空急流是影响此次降水的重要天气系统；（2）在高层辐散低层辐合的有利动力条件下，极端的水汽输送与吉林地区西低东高地形的阻挡和强迫抬升是极端降水产生的重要原因；（3）中高层有干冷空气入侵，伴随高空动量下传至低空，加强了低空急流发展，低空急流发展至地面附近产生超低空急流后，加强了上升运动。南北经向动量输送交汇加强了低层风辐合切变，切变线上对流发展与永吉附近小地形的抬升作用，诱导永吉县产生极端降水。
关键词:东北冷涡/
极端降水/
高低空急流/
动量
Abstract:The analysis of circulation background and trigger mechanism of an extreme precipitation weather process was carried out in the Jilin area on July 13?14, 2017 using the ERA-Interim reanalysis data, conventional meteorological observation data, CMORPH (CPC MORPHing technique) fusion precipitation data, and high-resolution numerical simulation results of WRF (Weather Research and Forecasting). The observed results are as follows: (1) The large-scale circulation background of precipitation was found in the northward movement of the subtropical high- and cold vortex over Northeast China and mid-latitude front zone. Precipitation occurred between the bottom of the cold vortex and the subtropical high in the straight zonal circulation. Clod trough, low-level shear line, upper-level jet stream, and low-level jet stream are all critical weather systems that influence precipitation. (2) Extreme water vapor transport, blocking, and forced uplift of the low west and east high terrain in the Jilin area are the factors that cause extreme precipitation in the context of high-level divergence and low-level convergence. (3) Dry and cold air intruded into the middle and upper levels, and high-level momentum was transmitted to the low altitude. Thus, the low-level jet was strengthened, which generated an ultra-low-level jet near the surface, enhancing the vertical ascent movement. The intersection of north-south meridional momentum transport strengthened low-level wind convergence shear. The development of convection along the shear line and the uplift of nearby small terrain led to extreme precipitation in Yongji County.
Key words:Cold vortex over Northeast China/
Extreme precipitation/
High-level and low-level jet/
Momentum
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