Acta Geographica Sinica ›› 2007, Vol. 62 ›› Issue (9): 959-969.doi: 10.11821/xb200709007

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Variation of Total Cloud Amount and Its Possible Causes over the Qinghai- Xizang Plateau during 1971-2004

ZHANG Xueqin1, PENG Lili1,2, ZHENG Du1, TAO Jie1,2   

  1. 1. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China;
    2. Graduate University of the Chinese Academy of Sciences, Beijing 100029, China
  • Received:2007-05-16 Revised:2007-06-15 Online:2007-09-25 Published:2007-09-25
  • Supported by:

    National Natural Science Foundation of China, No.40331006; National Basic Research Program of China, No.2005CB422006; Knowledge Innovation Project of CAS, No.KZCX2-YW-310; No.CXIOG-A04-03

Abstract:

The Qinghai-Xizang (Tibet) Plateau plays a crucial role in global change and the climate of East Asia. It is indispensable to analyze the characteristic of cloudiness variation over the Plateau, which will promote the understanding of climatic change and of cloud-radiation feedback mechanisms in climate models. With EOF and trend analysis method adopted, the spatio-temporal variation of total cloud amount is analyzed for 75 stations over the Plateau during the period of 1971-2004. Analysis indicates that the distribution of total cloud amount is characterized by remarkable regional features, which decreases from the southeast to the northwest of the Plateau. In addition, the annual and seasonal variation of total cloud amount shows a declining tendency over the past decades. Correlation analysis demonstrates that total cloud amount is negative with sunshine duration and diurnal temperature range (DTR), and is positive with precipitation and relative humidity, respectively. The negative correlation is consistent with the radiative effect of cloud, while the positive correlation between total cloud amount and precipitation is obscured because of topographic factor. Discussion implies that the decrease of total cloud amount is possibly due to the variation of atmospheric aerosol content and ozone concentration over the Plateau, although it is difficult to quantify the driving forcing mechanism up to now.

Key words: Qinghai-Xizang (Tibet) Plateau, total cloud amount, spatio-temporal variation, forcing