Based on the high temporal and spatial resolution data of wind profile radar, the characteristics of the low-altitude wind field during the two rainstorm processes in Chengdu in July 2018 were analyzed. The results are as follows: (1) Before the start of heavy precipitation, the southward wind of 2-4 km strengthened and even reached the strength of jet stream. The peak value of jet index had a certain advance compared with the beginning time of short-term heavy precipitation. (2) When the short-time heavy precipitation started from the invasion of cold air in the middle and lower layer, the disturbance of wind field near the height of 0.5 km occured about 1 h earlier than the start time of heavy precipitation. (3) The two heavy precipitation processes showed that the strong vertical shear generated by strengthening of the south wind was conducive to the occurrence of heavy precipitation, while the strong shear generated by strengthening of the north wind weakened the precipitation.

From the view of single station and region, based on the daily average temperature and minimum temperature data at 5 meteorological stations in eastern Hexi Corridor of Gansu Province from 1960 to 2017, the temporal and spatial variation characteristics of cold waves frequency were analyzed statistically by using linear trend analysis, Mann-Kendall test and Morlet wavelet methods. The results show that the spatial distribution of cold waves frequency and intensity was obviously different at each station of eastern Hexi Corridor. The frequency of cold waves decreased gradually from north to south except for Wuwei station, while the intensity of cold wave was strong in the north and the south and weak in the middle. The single-station cold waves mainly occurred from September to next May, while the regional cold waves distributed from October to next May, and the single-station and regional cold waves tended to happen in spring, while the strongest was easily to occur in autumn. The frequency of cold waves mutated significantly from many to few at Minqin, Yongchang and Wuwei stations of eastern Hexi Corridor from 1960 to 2017, and the mutation occurred in 1973, 1973 and 2014, respectively. The frequency of cold waves existed 41 a periodic change at five stations of eastern Hexi Corridor. The frequency of regional cold waves appeared interdecadal variation in phase, it significantly decreased firstly and then slowly increased, but the mutation wasn’t significant, and there were 42 a, 15 a, 8 a and 4 a periodic changes. The current statistical standard of cold waves can’t fully reflect cold air activity with temperature slowly declining.