Based on daily precipitation data from 44 national meteorological stations in the southern Xinjiang and the NCEP/NCAR reanalysis data from May to September (warm season) during 1961-2020, the spatial and temporal variation characteristics of rainstorm and large-scale circulation anomalies under different decades and climatic background (warm-dry period and warm-wet period) in the southern Xinjiang were analyzed. The results show that the cumulative rainstorm days, rainstorm stations and rainstorm rainfall in the warm season of the southern Xinjiang has been increasing since 1961, but the variation trend of rainstorm intensity and the proportion of rainstorm rainfall in total precipitation was not obvious. The cumulative rainstorm days, rainstorm stations and rainstorm rainfall in the warm-wet period in the southern Xinjiang were significantly more than those in the warm-dry period, and the rainstorm intensity and the proportion of rainstorm rainfall in the total precipitation had little difference in the warm-wet period and the warm-dry period. After entering the warm-wet period, the rainstorm days and rainstorm rainfall amount increased in most stations in the southern Xinjiang (the most obvious increase was at southwest stations), but the increase extent in mountain area was smaller than that in plain. The central Asian trough, central Asian vortex and Tarim easterly low level jet were the main influencing systems for the heavy rain in the warm season in the southern Xinjiang. The heavy rain in the warm season in the southern Xinjiang was dominated by low vortex type in the warm-dry periods, and low trough type in the warm-wet periods. The easterly flow 850 hPa extended westward more obviously in the low vortex rainstorm than in the low trough rainstorm. In the circulation difference field between the warm-wet periods and the warm-dry period, the circulation anomaly in the high latitude area of the low trough rainstorm and the low vortex rainstorm showed reverse change characteristics.

Based on the observation data of daily maximum temperature from 105 national meteorological stations in Xinjiang and the NCEP/NCAR reanalysis data from May to September during 1981-2019, the spatial and temporal characteristics and circulation types of regional high temperature weather processes in Xinjiang were analyzed. The results are as follows: (1) During 1981-2019, there were 100 regional high temperature weather processes in Xinjiang, concentrating in the Yili valley plain, the southern edge of Junggar basin in northern Xinjiang, Tarim basin in southern Xinjiang and the plain area in eastern Xinjiang, which mainly occurred from June to August, with the most in July, the second in August and the least in June. (2) Since the 21st century, the number of high temperature weather processes showed an increasing trend and the intensity of the processes obviously enhanced. The start time of the processes showed an advance trend, while the end time pushed. In addition, the duration days of the processes showed a phased trend of “increase, decrease, increase”. (3) The circulation situation at 500 hPa geopotential height field causing the regional high temperature weather processes in Xinjiang could be divided into four types, namely the eastward extension of Iranian subtropical high type (accounting for 54.0%), the superposition type (accounting for 32.0%), the Xinjiang high pressure ridge type (accounting for 12.0%), and the westward extension of western Pacific subtropical high type (accounting for 2.0%).

 Based on the hourly precipitation data of 10 national meteorological stations from 2012 to 2019, the diurnal variation characteristics of precipitation in different seasons in the Yili River Valley of Xinjiang were analyzed. The results are as follows: (1) The diurnal variation characteristics of cumulative hourly precipitation in the Yili River Valley showed a single peak in spring, summer and winter, and a double peak in autumn. The low value period of diurnal accumulated hourly precipitation in four seasons appeared in the afternoon (15:00-19:00), the high value period appeared in the morning (10:00-12:00) in spring, autumn and winter, and in the first half of the night in summer (22:00). (2) The diurnal variation characteristics of cumulative precipitation frequency and cumulative precipitation in the same season were similar. There were significant regional differences in spatial distribution of hourly average precipitation and peak precipitation frequency. (3) Shortduration precipitation events were the main events in four seasons in the Yili River Valley, with the highest proportion (89%) in summer and the lowest proportion (70%) in winter. Short duration precipitation events were the main contributors to total precipitation in summer, while long duration precipitation events were the main contributors to total precipitation in winter. (4) There was a close relationship between the daily circulation of precipitation and the persistence of precipitation in four seasons in the Yili River Valley. The precipitation events lasting for 2-8 hours and 1-4 hours were the main contributors to the diurnal variation of precipitation in spring and summer. Three types of precipitation events with different durations had roughly equal contributions to the diurnal variation peaks of precipitation in autumn and winter in the Yili River Valley.