高亚洲积雪监测

Monitoring Snow Cover on the High-Asia

使用SMMR微波候积雪深度资料(1978～1987),NOAA可见光周积雪面积资料(1966～1989),以及60个基本气象台站逐日雪深、密度和月积雪日数资料(1957～1992)通过平均图与距平图分析,揭示出高亚洲积雪地理分布、季节变化与年际波动特征,并进行了积雪区划。使用统计模式,用平均差值法、最小二乘法以及自回归滑动平均3种趋势估计方法计算了积雪变化趋势。高亚洲积雪空间分布以四周,特别是东西两侧多雪,广大腹地少雪为特征,冬季积雪鼎盛时期,积雪也仅覆盖着不足79％的地面,平均雪深18.5cm,积雪贮量(水当量)115.0km^3。高亚洲积雪年际变化十分显著,以冬季积雪年变率最高,其年际波动主导着全年积雪的年际变化,东西两侧多雪区年际波动位相相反,西藏东部为欧亚大陆积雪年际变化最突出的地区。积雪变化与北半球冬季气温呈正相关,随着全球变暖,积雪量呈普遍增加趋势。

The snow cover in central High Asia has been the focus of climatologists interests for many decades. In this paper three complete High-Asia snow cover data sets consisting of SMMR microwave pentad snow depth maps covering the period 1978-1987, operational NOAA weekly snow cover extent charts during the period between 1966-1989, and daily snow depth, density, as well as number of snow cover days records at 60 primary weather stations over the 36-year period 1957-1992 are used to investigate the spatial patterns, seasonal cycle, and year-to-year variation of snow cover over the High-Asia. The regionolization of snow cover is also briefly discussed.An empirical analysis is applied to examine typical spatial pattern and variation of snow cover, and a statictical model consisting of a trend plus serialy correlated noice is fitted to the area and point time series data to test for trends in snow cover variation.The spatial pattern is characterized by unpervasive feature, even a deapth of snow in the vast interior of the High-Asia. Only in the western and eastern parts of the High-Asia is some appreciable and persistent snow cover noted. On average, below 79% of entire High-Asia area is snow covered during the winter snow maxima with the mean snow depth being 18.5 cm or snow water equivalent as much as 115.0 km3. The large interannual variability of snow cover over the High-Asia is the most striking feature and winter (D.J.F) variance in snow mass is more significant than other seasons. The eastern Tibet is affected by most substantial year-to-year variation in snow mass. Three trend estimates imply that the increase in annual snow depth is a systematic development and almost omnipresent over the High-Asia. Further examination reveals a positive relationship between High-Asia snow cover and surface air temperature in winter time over the Northern Hemisphere.