Based on data from automatic station,Doppler weather radar,wind profiler,and ERA5 reanalysis data,an extreme short-term heavy rainfall event under the background of a southward-moving cold vortex in southern Jiangsu on August 17,2023 was analyzed,and its formation mechanism and mesoscale evolution characteristics were revealed.The results showed that:1)This extreme short-term heavy rainfall event was classified as convective weather type of the northwest flow in the back of cold vortex,with the cold vortex moving southward rapidly and the strong northwest flow in the back of the vortex providing unstable stratification conditions for the development of convection.2)High Convective Available Potential Energy(CAPE),a thick warm cloud layer,and a large specific humidity area near the surface layer were the key environmental factors for the formation of extreme short-term heavy rainfall.The total precipitable water exceeding 50 kg/m2,along with the wind direction convergence in north-south direction and wind speed convergence in east-west direction near the surface layer jointly provided favorable water vapor and initial dynamic conditions for the generation of heavy rainfall.3)Two types of strong pre-cipitation echoes were observed in southern Jiangsu:continental strong convection and tropical maritime convection.The"train effect"and"merging effect"jointly led to the"double-peak"structure of extreme single-point heavy rainfall,while some local-ized echoes showed characteristics similar to a supcrccll storm structure.4)Prior to the occurrence of heavy rainfall,the down-ward propagation of momentum from the high-level north winds changed the direction and speed of winds in the mid-levels,while the northeast wind speed near the surface increased rapidly.The combined effects of the two factors intensified the verti-cal wind shear,thereby enhancing the instability of stratification.
关键词
短时强降水/冷涡/大气可降水量/成因机理/中尺度演变
Key words
short-term heavy rainfall/cold vortex/total precipitable water/formation mechanism/mesoscale evolution
维普
万方数据