CLIMATE CHANGES OF CHINA′S MAINLAND OVER THE PAST HALF CENTURY

A data set of mean temperature, precipitation and other climate parameters for 740 stations across China′s Mainland was used to analyze climate change in mainland China. The data set has been processed more carefully, and the main in homogeneities existing in the monthly mean temperature data have been checked and corrected. The widely accepted procedures for creating area-averaged climatic time series and for calculating linear trend have been used. Analyses have been made for annual and monthly mean temperature, precipitation, pan evaporation, sunshine duration, wind speed, and the maximum depth of snow cover.The analyses show that annual mean surface air temperature in China′s Mainland as a whole rose by about 1.1 ℃ for the last 50 years, with a warming rate of about 0.22 ℃/10 a. The warming in the later half 20th century is more rapid than the average values of the world and the Northern Hemisphere. The most evident warming occurred in winter and spring as expected. Northeast China, North China and Northwest China experienced more significant warming in terms of annual mean temperature, while a cooling trend reported in earlier studies is still continuing. Summer mean temperature in the middle and lower reaches of the Yangtze River also decreased in the last 50 years. No significant long term change in the countryaveraged annual precipitation was seen for both the past 50 years. However, an obvious tendency of drying in the Yellow River Basin and the North China Plain in terms of precipitation has been found, and the largest drop in precipitation occurred in Shandong Province. Meanwhile, an insignificant wetting trend in the Yangtze River Basin and most parts of western China could be detectable. For the Yangtze River Basin, the increased annual precipitation mainly resulted from the significant rising of summer rainfall, though winter precipitation also tended to increase.Since 1956, the country veraged pan evaporation has had a significant trend to decrease, with a changing rate of -34.5 mm/10a. The most significant decreaseoccurred in spring and summer in the North China Plain and the lower reach of the Yangtze River. The largest decrease in Pan evaporation in terms of absolute values is in northwestern China. It is worth to note that average sunshine duration and wind speed are also experiencing a tremendous drop in most regions of the country during the past 50 years, and they usually bear a similarity with pan evaporation in spatial pattern of the tendencies. In parts of the North China Plain,annual sunshine duration in the recent years is almost 500 hours fewer than that of 50 years ago. We have also tentatively analyzed the possible causes for the observed changes. However, it is be premature at this moment to give a definite conclusion.