三江源地表反照率时空变化及其与气候因子的关系

Spatial-temporal Changes of Surface Albedo and Its Relationship with Climate Factors in the Source of Three Rivers Region

基于2001-2010年的MODIS地表反照率产品（MCD43A3），分析三江源地区地表反照率的空间格局和变化规律，并结合该地区14个气象站点的气温和降水数据，探讨地表反照率与气候因子的相关关系。结果表明：三江源地区地表反照率在空间上呈西高东低的分布特征，与该地区高程变化的趋势基本一致；10a问平均地表反照率为0．209，集中分布在0．15～0．25。从年际变化来看，研究区地表反照率整体呈增加趋势，但变化不显著；地表反照率的季节变化较为明显，从冬季到夏季逐渐减小，从夏季到冬季逐渐增加，低值时段为6-9月，变化近似于“u”字形。温度和降水能够通过影响植物的生长和土壤表层含水量进而影响地表反照率；在季节尺度上，地表反照率受春季和秋季气候条件的影响最为显著，二者存在显著的负相关关系，而在冬夏两季地表反照率与气候因子在空间上具有正相关和负相关共存的现象。

Surface albedo, the fraction of surface incident solar radiation that is reflected back to space, which controls surface energy balance and affects the microclimate conditions of ecosystems, is a critical physical variable affecting the Earth＇s climate. In this study, the MODIS albedo products （MCD43A3） from 2001 to 2010 were a- dopted to investigate the surface albedo temporal and spatial changes in the Source of Three Rivers Region （STRR）. The results indicated that the surface albedo decreased from the west to in the east in general in the re- gion. During 2001 -2010, the mean surface albedo of STRR was 0. 209, and mostly ranged from 0.15 to 0.25. The interannual variability of the surface albedo showed a moderate increase trend over the study period while the seasonal changes of the surface albedo seasonal cycle presents a“U” shape, which obviously decreased from winter to summer and then increased from summer to winter, with the lowest value appeared in Jun to September. Based on the meteorological data from fourteen climatic stations, the surface albedo had varied correlation relationships with the climate factors, such as temperatures and precipitations, in seasonal time scales rather than in annual time scales. The surface albedo had a significant and negative correlation with the climate factors in spring and autumn but had both positive and negative correlation coexisted in summer and winter. In conclusion, changes in tempera- ture and precipitation can influence the vegetation cover as well as the soil moisture, which therefore affect the sur- face albedo.