Based on the daily precipitation data at 18 meteorological stations of Hainan Island from 1969 to 2018, the spatio-temporal change characteristics of precipitation randomness were analyzed by using information entropy method, Mann-Kendall trend test and spatial interpolation technique of inverse distance weight. The results show that the uneveness of monthly apportionment of annual precipitation and precipitation days increased from east to west of Hainan Island. In recent 50 years, the monthly apportionment unevenness of annual precipitation and precipitation days showed an increasing trend in northern and western areas and part areas of southern Hainan Island, while it showed a decreasing trend in the rest areas on the whole. The spatial distribution of randomness of daily precipitation was significantly different in the whole year and four seasons in Hainan Island, and they were significantly and positively correlated with the proportion of rainstorm and above rainfall days. In terms of time, the randomness of daily precipitation in the whole year and four seasons increased in most cities (counties) of Hainan Island from 1969 to 2018, especially the probability of strong precipitation increased in four seasons. The rainstorms to torrential rains in central, northwestern, eastern and eastern Hainan Island should be paid enough attention in spring, summer, autumn and winter, respectively.

Based on the precipitation data at regional automatic stations and conventional weather stations of Hunan Province, NCEP/NCAR reanalysis data, JRA-55 reanalysis data and the forecast products of atmospheric river (AR) from Hunan Provincial Meteorological Observatory, the characteristics of heavy rainfall and abnormal water vapor transport of the flood-causing torrential rainfall in Hunan Province from 22 June to 2 July 2017 and the influence of AR water vapor transport on heavy rainfall were analyzed. And on this basis the water vapor budgets at each boundary over heavy rainfall area and the contributions of water vapor trajectories were analyzed quantitatively. The results show that the torrential rainfall process had three stages, the range and intensity of rainfall at the first and the third stages were significantly greater than those at the second stage. The stable circulation situation with ‘one trough and one ridge’ in middle and high latitudes of Asia and Europe, the relatively stable subtropical high in low latitude and its peripheral strong water vapor transport were weather background of the heavy rainfall. The horizontal and vertical distribution of physical quantities such as water vapor flux, water vapor flux divergence and specific humidity had great indication to the periodic characteristics and the change of location and intensity of rainfall. The intensity and location of water vapor transport from the Bay of Bengal, the South China Sea and the southwest side of the subtropical high were different at three stages of the heavy rainfall process, which caused the spatial difference of southerly abnormal water vapor transport to Hunan. The intensity of AR and its water vapor transport channels, the location of convergence zone and the net water vapor income at each boundary over heavy rainfall zone played a key role in the occurrence and development of the heavy rainfall. The southerly water vapor transport in low level was an important factor of the heavy rainfall lasting for a long time, while the invasion of dry and cold air from the north was beneficial to the enhancement of atmospheric baroclinicity and the maintenance of convection instability, which was another reason why the intensity of rainfall at the second stage was weaker than that at the first and third stages.

Based on aerological observations at the hail supp ression experimental stations of Yongdeng andMinxian counties of Gansu Province during 1979 - 1987, as well as surface meteorological observations at the same time, the upperwinds under the six different weather conditions of strong hailstorm, weak hailstorm, thunderstorm, shower, overcast and sunshine were analyzed. Results show that significant defference p rezented in low airwind direction shear, middle airwind velocity shear and jet in upper air before haill falling under the strong hailstorm weather condition compared with those of otherweather conditions, which is useful to forecast hailstorm and study its formation mechanism.

In this paper,.the spatial and temporal characteristics of drought in China are the analyzed. On the basis of the main factors of the influence of China climate anomaly .the causes of drought are also studied.  It is shown that the causes of formation are mostly the
global and regional climate warming .the inter一annual and decadal oscillation of the main factors.