The spatiotemporal distribution and environmental parameter characteristics of short-duration heavy rain in Liaoning under the background of Cold Vortex from 2017 to 2021

Based on hourly precipitation data from automatic weather stations in Liaoning Province and ERA5 reanalysis data from 2017 to 2021,the short-duration heavy rain (CV_SDHR) with hourly rainfall no less than 20 mm under the background of the Cold Vortex (CV) was selected and divided into different quadrants based on the relative position of the automatic weather stations and the 500 hPa potential height center of the CV.The highest occurrence frequency of CV centers lies between the eastern Inner Mongolia (110°～124°E) and the northern Heilongjiang(48°N),up to 58°N when CV_SDHR occurs.The spatiotemporal distribution and environmental parameter characteristics of SDHR in different quadrants were compared.The results show that CV_SDHR accounts for 35.7% of the total SDHR.The proportion of CV_SDHR in different quadrants decreases in the following order:southeast (SE_SDHR),southwest (SW_SDHR),northeast,and northwest quadrants.CV_SDHR with large hourly rainfall and wide impact range is mainly concentrated in the southeast and southwest quadrants of CV.The central and northern parts of Liaoning is a high-risk area for CV_SDHR.The stations dominated by SE_SDHR cover the Liaohe River Basin and coastal areas,while the stations dominated by SW_SDHR are concentrated in northern part of Liaoning.CV_SDHR exhibits monthly and daily variation characteristics with unimodal distribution.It mainly appears in the afternoon to evening from July to August,but with variations in different quadrants regarding the peak proportion,occurrence time,and duration.The similarity of CV_SDHR in different quadrants is that the temperature and humidity profiles are closer,the CAPE is narrower,and the wind field is conducive to the formation of vertical wind shear.The difference is that SE_SDHR often occurs in warmer and wetter environments,and has stronger and vertical wind shear,which is more conducive to the occurrence of stronger and larger range of CV_SDHR.The SW_SDHR appears in environments with dry water vapor,strong static instability,and lower relative humidity near the ground,making it more conducive to the simultaneous occurrence of multiple severe convective weathers.