This paper addresses the spatial and temporal variation of cloud cover at different heights over southern China and its relationship with precipitation, which is useful for understanding the role of clouds in precipitation and feedback mechanisms as well as provides a basis and foundation for the development of cloud water resources. Based on 12 years (1998-2009) data from the D dataset of International Satellite Cloud Climatology Project (ISCCP), the temporal and spatial distribution characteristics of total cloud cover, low cloud cover, medium cloud cover and high cloud cover were analyzed over Southern China. And based on the CMORPH-AWS merged gridded precipitation product which combined National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC) morphing technique (CMORPH) with precipitation observations from automatic weather stations, the relationships between the cloud cover and precipitation intensity, precipitation frequency were analyzed over southern China. The results are as follows: (1) The spatial distribution of total cloud cover and medium cloud cover over southern China was similar. The high-value center was located over the junction of Sichuan Basin, Guizhou and Chongqing, while the low-value center was located in Yunnan. High clouds were distributed in the western part of southern China, and decreased from west to east. Low clouds were mainly distributed over the southeastern part of southern China. Overall, low cloud cover decreased from coastal area to inland area. (2) The seasonal variation of total cloud cover and high cloud cover was similar, with cloud cover more in summer and less in winter. Moreover, the high value center of total cloud cover shifted with the seasons. The high cloud cover changed seasonally. The moderate cloud cover and low cloud cover were more in winter and less in summer, with small seasonal changes. (3) With the increase of total cloud cover and high cloud cover, the precipitation intensity increased but the monthly precipitation frequency decreased. With the increase of medium cloud cover, the frequency of monthly precipitation increased, while effect on precipitation intensity varied little. (4) With the increase of cloud cover of stratocumulus and stratus clouds, precipitation intensity and monthly precipitation frequency decreased. With the increase of cloud cover of altocumulus, altostratus and deep convection clouds, precipitation intensity increased while monthly precipitation frequency decreased. In general, cloud cover and precipitation were closely related over southern China, especially total cloud cover and high cloud cover had a greater influence on precipitation intensity and precipitation frequency, while medium cloud cover only had a greater impact on precipitation frequency. The cloud cover of stratocumulus, stratus, altocumulus, altostratus, deep convection clouds had a greater influence on precipitation intensity and precipitation frequency, while cloud cover of cirrus and cirrostratus only had a greater impact on precipitation intensity.

Based on the monthly cloud dataset of ISCCP D2 from January 1994 to October 2009, the temporal and spatial distribution characteristics of total cloud amount, cloud water path and cloud optical depth over five regions of China were analyzed in detail. The results are as follows: (1) The most liquid-phase cloud distributed over Sichuan Basin to southeast coast of China, while the most ice-phase cloud distributed over northern China and Tibet Plateau. The coverage of cirrus was the widest, and its cloud amount was the biggest over China, followed by cirrostratus, liquid-phase altostratus, liquid-phase cumulus, and the low cloud with ice-phase was the smallest. (2) The total cloud amount, cloud water path and cloud optical depth of stratocumulus, nimbostratus with liquid-phase and deep convective cloud were bigger, which indicated that the cloud water contents were rich, their contributions were bigger to precipitation over Sichuan Basin to southeast coast. (3) The seasonal variations of total cloud amount with different types were obvious over China, and their performances were different over five regions of China. The total cloud amount of most liquid-phase clouds especially nimbostratus was more in summer and less in winter over northern China and Tibet Plateau, while it was less in summer and more in winter over southwestern China and southeastern China. However, the regional difference of cloud amount with ice-phase was little, and the cloud amount of ice-phase altocumulus and altostratus was more in winter and less in summer over most regions, while that of ice-phase cirrostratus and deep convective cloud was more in summer and less in winter, which indicated that the temperature declining and convection weakenning were benificial to gather of ice-phase clouds and development to medium and low layers in winter, while the temperature increasing and convection strengthening were benificial to gather of liquid-phase clouds and development to high layer in summer. (4) The cloud water path of liquid-phase stratus and nimbostratus had obvious seasonal variations over China, and the regional characteristics were obvious, especially the monthly distribution appearred double peaks pattern over southeastern China, the peaks were in February and November. However, the peak of cloud water path of ice-phase clouds occurred in summer over northern China and winter in southern China.