西藏地区1971——2008年台站观测总云量的变化特征

Characteristics of Total Cloud Amount over Tibet in 1971-2008

利用1971—2008年西藏地区22个台站观测的总云量资料,初步分析研究了西藏地区总云量的变化趋势。结果表明:西藏大部分区域年总云量呈显著减少的趋势,其中那曲中西部的减幅最大,达2.32%/10a,而南部边缘年总云量减少的趋势不显著。总云量与降水、相对湿度呈正相关,与日照时数、平均气温及气温日较差呈负相关。总云量的Hurst指数表明,西藏大部分地区总云量呈减少的趋势,未来这种减少的趋势将持续,短时期内不会发生逆转。

By using the data of total cloud amount at 22 stations over Tibet in 1971-2008, the change trends of total cloud amount were analyzed. The results show that the annual average total cloud amount decreased remarkably in most parts of Tibet, especially in the mid-west of Naqu where the trend was -2.32%/10a; but over the southern edge of the Tibetan Plateau, the reducing trend was not significant. Correlation analysis demonstrates that total cloud amount was correlated positively with precipitation and relative humidity, and negatively with sunshine duration, average temperature and diurnal range of temperature. The Hurst index of total cloud amount shows that the total cloud amount had a decreasing trend in most parts of Tibet; this trend will continue, and will not change in a short period of time.