关键词: 地形作用, 冷空气回流, 锢囚锋, 低涡降水

Abstract:

Based on the conventional observation data, automatic weather precipitation data, Doppler radar data and NCEP reanalysis data with 1°×1° spatial resolution, the formation mechanism of the low vortex on the north side of Guizhou Plateau under influence of north path cold air on May 22, 2017 was discussed. The results were as follows: (1) The terrain led to the cold air return and formed an occluded front. There was a low vortex between the surface and 800 hPa, which formed above the occlusion front, it  belonged to warm and shallow meso-β-scale vortex system. (2) The low vortex maintained for 2 days, the precipitation occurred near the center of the vortex and its intensity was not strong. (3) The development of the vorticity and maintenance of low-level vortex system were associated with fluctuation in the middle and upper atmosphere. When it turned to the northwest airflow on the upper layer, the development of vorticity was suppressed and the cold air invasion made the low vortex weaken and dissipate. (4) The evolution process of the vortex could be divided into three stages: terrain backflow, occlusion development, weakening and demise. There were significant differences between this vortex and southwest low vortex ,frontal cyclone in the formation mechanism, rainfall area and intensity.

Key words:  terrain effect, cold air return, occluded front, low vortex precipitation