Spatial-temporal variation of snow depth in Tibet and its response to climatic change in the past 30 years

Abstract

Snow depth is an important parameter to characterize snow features,and is also one of the sensitive factors of regional response to climate change. Based on snow depth daily data and monthly temperature, precipitation,wind and sunshine hours data from meteorological stations during 1979 to 2010,the authors analyzed the spatial and temporal variation of snow depth in Tibetan Plateau and its response to climatic change by using methods of anomaly analysis,mutation analysis,spatial analysis and power spectral analysis. The results showed that,in the period from 1979 to 2010,the snow depth increased obviously and significantly with linear trend rate 0. 26 cm /10a,but there was a pronounced decrease phase from 1999 to 2010,thus forming the situation that the snow depth increased first and then decreased in general in Tibetan Plateau. In the four seasons,winter mean snow depth contributed most significantly to the annual situation,with the correlation coefficient between them up to 0. 88. The snow depth was extremely excessive in the 1990s but with no climate mutation. An analysis of power spectrum showed that the snow depth had quasi- periodic oscillation of 6- 7 years. The results indicated that there were significant spatial differences in the snow depth of Tibetan Plateau. In the peripheral high mountains,snow depth was distributed extensively and had a long duration,but in the vast interior it was rare or even thin. The snow depth was significantly affected by the altitude with a steep step effect. And most of linear trend rates of snow depth in Tibetan Plateau were between- 0. 08 and 0. 08 cm / a,with the percentage reaching 74. 6%. The results of regression analysis indicated that the increased area of snow depth accounted for 76. 9%,while the decreased area accounted for 23. 1%. There was obvious statistical and spatial correlation between snow depth and temperature, precipitation,wind speed and sunshine duration in general; there was negative correlation between snow depth and temperature,wind speed and sunshine duration,but positive correlation between snow depth and precipitation. The results of multiple regression analysis showed that,in spring and autumn,the correlation coefficients between simulated snow depth and observation data were both above 0. 6 and passed 0. 01 significance test,while they were only between 0. 4 and 0. 5 in summer and winter and didn't pass the 0. 05 significance test.