| Snow is an indicator of climate change, and its changes have a profound effect on the energy and radiation balance and water cycle. Thus, it is the best empirical demonstration of regional response to climate change to study the relationship between snow and climate change, terrain. The Tibetan Plateau is the biggest and highest snow-covered region in the mid-latitude in the North Hemisphere. Changes of snow over the Tibetan have important effects on the synoptic climate in China, thus, to reveal the variations of snow and analyze the main causes are undoubtedly crucial to climate predictions. Using MODIS Snow Cover from March2000to February2011, the daily dataset of snow depth during1979-2010based on passive microwave remote sensing, MODIS Surface Temperature product from March2000to February2011, DEM and climate data of surface meteorological stations with the help of Mann-Kendall and spatial and statistics analysis function of GIS, the temporal and spatial variation regularity of snow depth, snow cover and snow line of Tibet Plateau and its response to climate change were analyzed and studied. It will provide important references for other studies, such as the simulation of snowmelt runoff and the spatiotemporal dynamics of snow and its driving factors. The main conclusions are as follows:The results showed that, during the period from1979to2010, the snow depth increased obviously and significantly with the rate0.26cm/(10a) in the Tibetan Plateau, and especially the snow depth of the Alpine desert zone in Kunlun increased most obviously with the rate0.73cm/(10a), and it decreased most clearly with the rate-0.34cm/(10a) in the montane evergreen broad-leaved forest in south side of eastern Himalayas. The snow depth gradually increased from the1980s to1990s, while it changed stably in the early21th century. From the perspective of seasons, the snow depth rose, particularly in winter with the rate0.57cm/(10a), and increased most obviously in Ali, north of Kunlun and the Alpine desert zone in Kunlun. As far as the spatial distribution is concerned, the deeper snow depth lied in the southeast, the western and southern areas of the Tibetan Plateau.The results of regression analysis indicated that the area of snow depth with an annual upward trend accounted for67.1%, of which91.3%is the mild and moderate increase which mainly occurred in the north and west Tibetan Plateau; moreover, the maximum snow depth varied between-0.1and0.1cm/a, which was on the rise in the north wing of the Kunlun, Qaidam and south of Qiangtang Plateau where the snow depth mildly increased; the sensitive areas of distribution anomaly of snow depth were in the alpine shrub of Guoluo and Naqu, south Qinghai and Qiangtang Plateau.The snow cover in the Tibet Plateau generally have been decreasing from2001to2010with linear trend rate-38900km2/10a.There were still large areas of perennial snow cover in July and August. Among the four seasons, snow coverage of spring is the largest. The results indicated that there were significant spatial differences of the Tibetan snow cover which showed the patch shape distribution.In the peripheral high mountains snow depth distributed extensively and had a long duration, but in the vast interior it was rare or even thin.The results indicated that snow line showed a stable and small downward trend over Tibetan in recent10years, but in all different natural divisions the trends were rather obvious during2006～2010. The snow line in the montane evergreen broad-leaved forest in south side of eastern Himalayas and the north wing of the Kunlun had a obvious decline trend, while the others showed a sharp rise. Snow line of Tibetan Plateau was under distribution of escalating from the southeast to the northwest, while the distribution of snow line was dense and complicated in the southeast and northwest of Tibetan, furthermore, high and low areas respectively corresponded to mountains and valleys.There is a clear correlation between snow parameters and climate factors over the Qinghai-Tibet Plateau. The results of statistical analysis indicated that, in spring, wind speed was the main impacting factor of snow depth and snow cover, while in winter, the change of snow depth was more sensitive to wind speed, by contrast, the snow cover area was mainly affected by the combination of rainfall and temperature. At the same time, the snow line of summer in the Tibetan was influenced by wind speed. There was significant negative correlation between snow depth, snow cover and surface temperature. The correlation coefficients of snow depth, snow cover and surface temperature, were-0.909and-0.580, respectively, while surface temperature was nearly6℃over snow cover area short of that on no snow area. The distribution of snow was significantly affected by the terrain, changed, and moved to high phase with increasing altitude and month lapse. The maximum snow depth kept increasing with the increment of elevation and slope, while the spatial heterogeneity decreased with the increment of elevation but increased with the decrement of slope. From October to May, the average snow depth at elevation from82to2482meter and from6082to7682meter affected by slope and aspect was slightly larger than that at elevation from2482to6082meter. The results of multiple regression analysis showed that the distribution of snow depth over the Tibetan was influenced by elevation and slope, furthermore, spatial differences of slope at elevation of82～3282meter had significant positive effect on the spatial variability of average snow depth, but elevation was the main limiting factor of the average snow depth. |
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