关键词: MODIS, 积雪反照率, 长江源, 温度

Abstract:

Albedo determines surface absorption capability for the solar radiation and impacts the surface radiation balance. The albedo on snow and ice is higher comparing other surfaces, and the absorption of energy from the sun is little on an ice or snow field. Monitoring and researching snow and ice albedo characteristics and variation are necessary to provide accurate data and the theoretical basis for hydrological process research of snow and ice. EOS-MODIS satellite data of snow albedo (MOD10A1 on Level3)were used in the article to analyze the regional and seasonal distribution of snow albedo, as well as the inter-annual trends in the source region of the Changjiang River from 2001 to 2010 using softwares such as ArcGIS and ENVI. Based on the meteorological data of 3 stations on the source region of the Changjiang River from 2000 to 2010, the basic features of temporal changes of temperature and precipitation were investigated. The results show that: 1) Snow albedo were different with space distribution in the snow season in the source region of the Yangtze River. The snow albedo was high on the northern source region of the Yangtze River and on the southwest of the source region of the Changjiang River with 0.67 to 0.91, respectively, whereas part of the east of the source region of the Changjiang River was low (0.15 to 0.48). The distribution of snow albedo closely related to spatial distribution of snow depth and effected by altitude. 2) The seasonal spatial distributions of snow albedo changed obviously in the source region of the Changjiang River. The snow albedo for the large proportion area of study area were 0.66-1, 0.4-0.57, 0-0.4 and 0.48-0.66 in winter, spring, summer, and autumn respectively. The variation of the seasonal snow albedo between spring and summer was the largest with difference of 0.3 to 0.5. In monthly scales, the mean snow albedo of the whole source region of the Changjiang River had the largest value in January (0.6), and the lower values in July (0.41) and August (0.42). 3) For the first decade in 21th century, mean annual snow albedo during the snow season had non-significant increasing trend in the most areas of the source region of the Changjiang River, whereas it increased significantly on the high altitude regions. The rate of regional snow albedo in the source region of the Changjiang River is 0.0002/a, but it was up to 0.0012/a on the glacier areas of the study area. There were statistical significantly positive correlations between snow albedo and snow cover and precipitation (snow fall) during the snow season. This suggests that snow albedo was sensitive to snow fall through the snow season. 4)The monthly snow albedo in summer on the source region of the Changjiang River showed a decreasing trend from 2000 to 2010, which is markedly affected by summer temperature, and there was a positive feedback relationship between them.

Key words: MODIS, snow albedo, the source region of the Changjiang River, temperature