关键词: 积雪覆盖率, 时空分布, MODIS, 地形, 西藏高原

Abstract:

Snow cover on the Tibet is a vital water source in western China and Himalayan regions. In addition, it is very sensitive to climate change and closely related to hydrological processes in the Tibet and downstream areas. Understanding snow cover dynamics and spatial distribution pattern is very important for regional water resources, environment management and climate change. Therefore, in this study, the spatial and temporal distribution patterns of snow cover and the impact of topography (elevation, aspect and slope) on snow cover distribution of the Tibet are analyzed based on snow cover fraction (SCF) derived from MODIS 8-day snow cover product （MOD10A2） from 2000 to 2014 and digital elevation model (DEM) using GIS spatial analysis and statistic methods. Results are as follows: (1) the spatial distribution of snow cover on the Tibet is spatially uneven, which is generally characterized by rich snow and high SCF on Nyainqentanglha Mountain ranges and surrounding high mountains and less snow and low SCF in southern valley and middle part of northern Tibet. Annual mean SCF is 16%, with 22% of SCF in spring and winter, 16% in autumn and 5% in summer. (2) Snow cover on the Tibet presents that the higher altitude the higher the SCF and the longer the snow cover duration and the more stable in intra-annual variations. Average SCF below 2000 m above sea level (masl) is less than 4% while it reaches to 75% above 6000 masl. (3) Intra-annual snow cover distribution below 4000 masl is characterized by unimodal patterns with the higher the altitude the more obvious single-peak type. Above 4000 masl, it is characterized by bimodal patterns with the higher altitude the more obvious double-peak types. The lowest SCF below 6000 masl occurs in summer while above 6000 m which occurs in winter. (4) For different slopes, monthly mean snow cover presents bimodal patterns with generally the higher slope the higher SCF. (5) For different aspects, SCF is highest in north aspect and lowest in south aspect, and is between the two of them in east and west aspects. The distribution pattern of intra-annual snow cover in different aspects is double-peak type, whereas it is single-peak type in flat terrain and its SCF is less than that in mountains with aspects.

Key words: snow cover fraction, spatio-temporal distribution, MODIS, DEM, Tibet