From the afternoon to night on 5 July 2021, severe convective weather including short-time heavy precipitation, thunderstorm wind and small hail occurred in the central region of Beijing-Tianjin-Hebei. The atmospheric environmental conditions and mesoscale characteristics of the formation of this weather process were analyzed by using the data of egional automatic meteorological station, Doppler radar, FY-2G meteorological satellite and microwave radiometer, and the fifth generation atmospheric reanalysis ERA5 from European Centre for Medium-Range Weather Forecasts. The results show that favourable water vapor conditions appeared before the occurrence of the severe convective weather including heavy precipitation, thunderstorm winds and local hail. Strong convergence of water vapor fluxes in lower and middle layers occurred 1 to 2 hours earlier than precipitation. The whole layer atmospheric precipitable water had accumulated continuously under strong uplift. The heat and power unstable environment of severe convection breaking out was created by formation of vertical θ_se energy frontal zone, maintenance of "upper dry and lower wet" unstable stratification, establishment of strong vertical wind shear from 0 to 6 km and enhancement of CAPE, K and SI indexes. Unstable stratification formed by eastward movement of the upper though carrying dry and cold air southward and low warm tongue, which had provided synoptic-scale upward movement for the occurrence of severe convection. The strong convective happening released more energy in the afternoon than in the evening. Heavy rainfall caused the local temperature to drop significantly and cold pool effect was more significant, which corresponded to the heavy precipitation area during the southward movement process. The surface convergence line at the cold pool boundary was the mesoscale trigger system. The cloud base height dropped and infrared brightness temperature increased rapidly, which indicated the formation of strong convective cloud cluster. The clear shadow at the southeast boundary of cloud body indicated the strong development of cumulonimbus cloud. Under the background of large-scale weather system, the important characteristic indexes obtained from in-depth analysis of mesoscale system can be used for the short term forecast and warning of severe convective weather.

Due to the low accuracy rate of maximum temperature prediction in Guizhou Province, the refined guidance forecast SCMOC data and meteorological observations data from 2013 to 2018 were used to study maximum temperature forecast for 24-72 hours of 85 stations in Guizhou. The horizontal prediction model (F1), the vertical forecast model (F2) and the combination model with F1 and F2 (Fzh) were established to forecast daily maximum temperature in Guizhou. The results show that Fzh took a best performance among three models, and for these three models, both mean root-mean-square error (RMSE) and accuracy rate were improved to varying degrees. Compared with SCMOC, the forecast results of F1 in spring and summer were better than that in autumn and winter, and the improvement in the northern areas of Guizhou Province was more obvious than southern areas. The forecast results of F2 were improved all the year round, and the overall improvement was relatively stable. The forecast accuracy rate of Fzh was obviously better than F1 and F2, and RMSE decreased significantly, the mean RMSE decreased 1.0 to 2.0 ℃, the accuracy rate increased by 11% to 13%.

The climate change trend was simulated in the last 50 years, and predicted in the next 10 years in Northwest China by using the global ocean-atmosphere land surface system model  developed by the State Key Laboratory of Numerical Modeling for Atmospheric Science and Geophysical Fluid Dynamics/Institute of Atmospheric Physics (IAP/LASG GOALS), which had been run under greenhouse gas emission scenarios provided by IPCC. The results show that the warming started at the end of the 1970s in Northwest China, but temperature increasing was small, and obvious warming began in the middle of the1980s. The climate features was simulated better in the past 50 years over Northwest China. In the future 10 years, the annual average temperature would increase by about 1.67 ℃ in Northeast China. The largest temperature rise would occur in the west, followed by the east of Northwest China, and the smallest temperature rise would occur in the north. The spatial and temporal distribution of precipitation would be complex. However, the precipitation would increase in the west of Northwest China. The precipitation would relatively reduce in the east of Northwest China, and the drought would aggravate.

 Based on the cloud-to-ground flashes data obtained by lightning location system from Gansu and Zhejiang, the temporal and spatial distrbution features of lightning activities have been analyzed respectively. In addition, by using ground and sounding data in lightning activity processes, the ralationship between lightning activity and atmospheric instability parameters is analyzed in the paper. The results indicated that the relative humidity of surface, SI, convective available potential energy(CAPE) and convective inhibition energy(CIN) were all impact factors of lightning activities, but the CIN has a greater impact on the lightning activities in Hangzhou and the relative humidity of the surface play a decisive role in Lanzhou.

The yearly rainy days with different rainfall level and annual precipitation were obtained by using the daily precipitation data (1960-2004) of 17 stations in the Qilian Mountain. By means of EOF and REOF analysis on normalized annual precipitation, the abnormal spatial distribution and the time evolvement of annual precipitation there were investigated. Results show that the climate average distributions of annual precipitation and different level rainy days were similarity in geographical distribution. Both the annual precipitation and the different level rainy days were evidently more in the west side than that in the east side of the same latitude area, and more in the east section than that in the west section of the Qilian Mountain, and the isoline presented the direction of northwest to southeast. The spatial anomaly of the annual precipitation  characterized the coincident variability in the whole area at first, and then the adverse trends in the east and the west part. The rotated loading vectors reflected 4 anomaly modes of the north slope of the west section, the east section, the south slope of the west and middle section, and the north slope of the middle section of the Qilian Mountain. In recent 45 years, the decadal change in precipitation was obvious in the north slope of the west section and relatively small in the other three areas. Wavelet analysis shows that the precipitation period changes were different in four areas, and that means the complexity of the annual total precipitation over the Qilian Mountain.