Based on the monthly hail days data,data of three sounding stations and ERA5 hourly reanalysis data of 31 meteorological stations in the western Sichuan Plateau from 2001 to 2016,the temporal and spatial distribution characteristics,the weather background and environmental conditions of hail were analyzed.The results showed that:(1)The hail frequency distribution curve in the west Sichuan Plateau from March to November showed a bimodal skew pattern,and the peak value of hail occurred in May and September in Aba,and in June and September in Ganzi.In recent 16 years,the number of hail days in western Sichuan Plateau showed a decreasing trend.Hail fell more frequently in high altitude areas than that in lower altitude areas.Hail occurred mainly from 11:00 to 21:00 in the west Sichuan Plateau,accounting for 95.5％.(2)The occurrence of continuous hail weather was usually accompanied by the eastward shift of plateau low value system and the shear effect on the west side of Huang-Huai low vortex,which was a weather system that could not be ignored in Aba area in summer.The large hail weather in the north of Aba in different seasons all occurred under the influence of the plateau low value system.The large hail in spring and summer were affected by obvious cold air or cold advection.(3)No matter in spring,summer or autumn,the temperature difference(T600～400 hPa)in the middle and low levels of the large hail case in Hongyuan was≥21℃ and the vertical wind shear at 600～400 hPa reached 15～21 m·s-1,which was conducive to the formation of highly organized convective storms.The height of-20℃ layer was 7.2～8.6 km,the height of 0℃ layer was about 4 km from the ground,and the CAPE≥980 J·kg-1.
HailTemporal and spatial distrbutionCirculation situationPhysical quantity characteristics
NETL
NSTL
万方数据
