Decreasing cloudiness over China: An updated analysis examining additional variables

Abstract

Trends in Chinese total cloud amount, surface air pressure, surface water vapor pressure, and surface relative humidity were analyzed for the period 1954–1994. The data were obtained from a database of 6‐hourly weather observations provided by the China Meteorological Administration. Seasonal and annual means of all four variables were computed for each of 196 stations and for China as a whole. Linear regression analysis was used to characterize seasonal and annual trends in these variables from 1954–1994, with the cloud amount record also extended through 1996 using a newly compiled global cloudiness database. Decreasing cloud amount trends are observed over much of China, as are increasing trends in surface air pressure. The spatial pattern of observed trends in water vapor pressure and relative humidity are more complex; a few scattered regions of China show increasing surface water vapor pressure, whereas surface relative humidity is found to increase in northwestern China and decrease in northeastern China (where the largest decreases in cloud amount are observed). The all‐China time series of total cloud amount (surface air pressure) shows a remarkable drop‐off (upswing) beginning in 1978.