Based on meteorological observation data, Doppler weather radar observation data and ERA5 hourly reanalysis data, the heavy hail weathers in Tongwei County of Gansu Province on May 30 and 31, 2020 were analyzed. The results are as follows: (1) The hail process on May 30 was a dry hail process, while the process on May 31 was a mixed strong convection with wet hail process. (2) Both two processes occurred during developing and moving eastward of the same low-trough, and the difference of influence system at 700 hPa led to difference of water vapor and energy conditions in middle and low levels, which was the main reason for occurrence of dry and wet hail. (3) The diagnostic analysis of physical quantities showed that the energy on May 31 was higher, the water vapor condition was better, and the static instability and convective instability were stronger than those on May 30, so the hail diameter was larger and precipitation intensity was stronger. (4) On the radar PPI image of reflectivity，the meso-scale characteristics of the two processes were obviously different, which was very helpful for classification and identification of severe convective nearly warning.

Based on daily observation data and disaster data from automatic weather stations in Hedong region of Gansu Province from 2008 to 2017, the 75 hail cases were selected with some standards and divided into three types according to main weather influencing system of hail and mesoscale diagnostic method, including the northwestern airstream, the low trough and the low vortex types. Then statistical characteristics of radar products and radar echo feature under the three weather types of hail were compared, and the typical hail cases were chosen to verify the results. The results show that the maximum reflectivity (Z_max) and the height of maximum reflectivity ( H_{Z_{\mathrm{m}\mathrm{a}\mathrm{x}}}) had relatively little differences under the three weather types of hail, Z_max was above 50 dBZ and H_{Z_{\mathrm{m}\mathrm{a}\mathrm{x}}} was above 2.0 km. There were significant differences in echo top height (ET), core area thickness (H), center height of echo reflectivity above 45 dBZ (H_{45 dBZ}), the maximum height of storm body echo reflectivity equal to or more than 30 dBZ (TOP), vertically integrated liquid water content (VIL), and the density of vertically integrated liquid water content (VILD). The H, H_{45 dBZ}, TOP and VIL of the northwestern airstream type were significantly higher than those of other types, and ET of the low trough type and VILD of the low vortex type were lower. The frequencies of overhang echo for the three types of hail weather were all higher than 61.0%. The frequencies of three body scattering and side-lobe echo for the the low trough type were 35.5% and 48.4%, respectively, and the probability of bounded weak echo was 12.9%. The frequencies of bounded weak echo area for both of the northwestern airstream type and the low vortex type were higher than 38.5%. The indicators of three body scattering and side-lobe echo could predict the hail weather 18 to 30 minutes in advance, which had some significance in hail weather forecast.

Based on the hourly precipitation data from April to September during 1960-2019 at 9 national meteorological stations and 400 regional meteorological stations built year by year in Longnan of Gansu Province from 2008 to 2019, NCEP FNL 1°×1° reanalysis data and MICAPS data, the spatial-temporal distribution and mesoscale characteristics of short-time heavy precipitation in Longnan of Gansu Province were analyzed. The results are as follows: (1) The occurrence frequency of short-time heavy precipitation in Longnan became more from the northwest to the southeast, with two relatively concentrated areas. The short-time heavy precipitation with rainfall intensity greater than 50 mm·h^-1 occurred in Cheng county, Hui county and Kang county in the east of Longnan. The occurrence frequencies of short-time heavy precipitation and rainstorm were more in the southeast of Longnan, and for short-time heavy precipitation it was also relatively high in the mountainous areas in the northwest. (2) Since 1960, the stations occurring short-time heavy precipitation in Longnan increased slowly.The monthly variation showed a single-peak type, with the maximum in August and accounting for 37.5% of the total stations occurring short-time heavy precipitation. The ten-day variation presented a double-peak type, with two peaks in early July and early August, respectively. The stations occurring short-time heavy precipitation was the most from late July to mid-August, accounting for 47.2% of the total stations. Diurnal variation showed that there was more short-time heavy precipitation at night than in the day, there were multiple peaks. The stations occurring short-time heavy precipitation increased significantly since 15:00 BST. The diurnal peaks of short-time heavy precipitation occurred at 23:00 BST, accounting for 9.4% of the total stations. (3) The short-time heavy precipitation in Longnan was closely linked to rainstorms. The mesoscale concept modes of short-time heavy precipitation in Longnan mainly showed three types, including low vortex shear, northwest air flow following the trough moving eastward and the southwest air flow beside the sub-tropical high.