Isolated convective cloud system is one of the important convective cloud forms in Hainan Island, it’s significant to study the evolution characteristics for identifying, tracking convective clouds and improving the efficiency of weather modification. Based on the S-band dual-polarization Doppler weather radar (CINRAD/SA-D) data of Hainan Island from 2015 to 2020, the dual-polarization characteristic of typical isolated convective clouds case and the evolution of isolated convective clouds over the island are analyzed. The results show that the radar data of the typical case of isolated convective clouds in Hainan Island (July 26, 2020) present obvious differential reflectivity (Z_DR) and specific differential phase shift (K_DP) column phenomena during the development phase, which means the convective motion in the clouds was strong. The total number of isolated convective clouds case in Hainan Island from 2015 to 2020 is 495 times, accounting for 11.82% of the total convective cloud cases (4 017 times). The southwest low pressure trough, the warming high pressure ridge and the southward cold front are three weather systems triggering isolated convective clouds easily. The isolated convective clouds from March to June are more, accounting for 76.84% of the total cases. It is significantly higher than that of other months. March is a high-incidence month for isolated convective clouds, in which isolated convective clouds account for 47.78% of the total cases. In one day, the period from 14:00 to 17:00 is the period of high occurrence of isolated convective clouds in Hainan Island, accounting for 72.84% of the total cases (475 times). The frequency of isolated convective clouds in southwestern and central mountainous areas in Hainan Island is higher, accounting for about 88.84% of the total cases (475 times). The movement direction of isolated convective clouds is mainly northeast and southeast, which is mainly affected by westerly and southerly winds. In addition, the movement speed of isolated convective clouds is mainly concentrated between 6 and 20 km·h^-1 and the movement distance of isolated convective clouds is mainly distributed between 6 and 20 km. More than half of isolated convective clouds in movement distance are less than 20 km.

Based on the hourly precipitation observation data of 105 national stations and 1240 regional stations and 8 Doppler weather radars data in Xinjiang from 2010 to 2018, from the perspective of operational forecasting, the definition of shortterm heavy precipitation process in Xinjiang was proposed and 468 shortterm heavy precipitation processes were selected, and circulation configuration of influence system and radar observation characteristics were analyzed. The results show that there were four kinds of influence systems including the central Asia trough (vortex), the west Siberian trough (vortex) and low level northwest jet stream. The convective storms resulting in shortterm heavy rainfall were combined enhancement type, train effect type and isolated convective cell type, and the combined enhancement type was 45.1%, isolated convective cell type was 34.8%, and the train effect type was 20.2%, respectively. The parameter thresholds of the maximum reflectivity factor intensity (Zmax), the maximum height of the strong echo (Dmax), the maximum height of the echo top (ET) and the maximum vertical accumulated liquid water content (VIL) observed by Doppler radar during shortterm heavy precipitation processes in southern Xinjiang were less than those in northern Xinjiang, and in Yili prefecture they were largest and in Aksu they were smallest. The shortterm heavy precipitation in Yili prefecture was dominated by low centroid echo, while in other regions it was dominated by low centroid and high centroid echo.

Based on the conventional observation data, Doppler radar products at Kashi station, FY-2D satellite cloud images and NCEP/NCAR reanalysis data, the formation mechanism and mesoscale weather system of four rainstorm processes under the anomalous circulation background in the west of Southern Xinjiang in August 2016 were analyzed comparatively. The results show that the more rainstorms in the western part of Southern Xinjiang in August 2016 occurred under the circulation background of the strong Ural Mountains high ridge on 500 hPa and Polar lows, anomalous water vapor convergence zone on 700 hPa over Tibetan Plateau and longitudinal oscillation of South Asia high. And the establishment, development and decline of the Ural Mountain high ridge on 500 hPa were closely related with rainstorms in the western part of Southern Xinjiang in August 2016. The intensity of rainstorm was closely related with 850 hPa warm ridge and temperature difference above 28 ℃ between 500 hPa and 850 hPa, while the differences of humidity layer thickness below 500 hPa, easterly airflow below 700 hPa, surface shear line and dry line resulted in different intensity, falling area and duration of rainstorm. The water vapor transport at the southern boundary was important source of rainstorm in the western part of Southern Xinjiang, while at the eastern boundary it was important supply of short-term heavy rainfall in the area. The humidity gradient on satellite images was conductive to the occurrence of convective weather, while the structures of the strong echo, low centroid and high cloud top of radar were beneficial to the occurrence of short-term heavy rainfall.