Acta Geographica Sinica ›› 2009, Vol. 64 ›› Issue (5): 581-591.

The Climate Characteristics and Changing Trends over the Nujiang River Basin in Tibet from 1971 to 2008

DU Jun1,2, WENG Haiqing3, YUAN Lei2, MA Pengfei2, LHAK Pa2

1. 1. Institute of Plateau Meteorology,China Meteorological Administration,Chengdu 610071,China;
2. Tibet Climatic Centre,Lhasa 850001,China;
3. Tibet Meteorological Bureau,Lhasa 850001,China
• Received:2008-12-28 Revised:2009-03-15 Online:2009-05-25 Published:2009-05-25
• Supported by:

National Natural Science Foundation of China,No.40865008;Open Lab Foundation of Institute of Plateau Meteorology,CMA,Chengdu,No. LPM2008010

Abstract:

This paper studies the changing trend of annual and seasonal mean temperature, maximum temperature, minimum temperature, precipitation and sunshine duration etc. by using the observational data of 9 meteorological stations over the Nujiang River Basin in Tibet from 1971 to 2008. It also analyzes the variation trend of meteorological elements by climatic linear trend methods, and discusses the correlation between the linear trend of elements and latitude, altitude and longitude. The results show that the annual mean temperature has increased over the Nujiang River Basin with a rate of 0.26 oC/10a during the past 40 years, which is lower than that in Northeast China and Northwest China, and is higher than that in the Huaihe River basin and South China, and similar to that over the Qinghai-Xizang Plateau. The trends of mean maximum and minimum temperatures are increasing, the trend of diurnal temperature range is significantly decreasing at a rate of (-0. 13~-0.57) oC/10a. The annual precipitation increases significantly and the linear increasing rate is 21.0mm/10a, while that in all seasons increases. The annual sunshine duration decreases over the Nujiang River Basin with a rate of -31.7 h/10a, and the maximum decrease is in summer, and the rate of decrease is greater than that in the Huanghe River basin and eastern margin of the Qinghai-Xizang Plateau. In addition, the variation of maximum frozen soil depth shows a significant declining trend over the upper reaches of the Nujiang River Basin in Tibet, resulting from the increasing soil temperature, especially in Amdo. Correlation analysis demonstrates that sunshine duration is significantly negative with precipitation (all seasons) and surface vapor pressure (in summer and autumn). Results indicate that the principal causes for the decrease of sunshine duration are the significant increase of surface vapor pressure and precipitation in most parts of the Nujiang River Basin. The correlation between total cloud amount and diurnal temperature range is negative significantly, and is positive evidently with precipitation in summer, hence the relative humidity is not the main affecting factor with the decrease of total cloud amount. The amplification of annual temperature and precipitation became greater with the increase of altitude and latitude. The linear trend of sunshine duration is positively related with longitude, and the decreasing amplitude of sunshine duration in summer and winter decreases with increasing longitude.