基于MODIS数据地表反照率时空变化特征及影响因子研究

地表反照率表征地球表面对太阳辐射的反射能力，是影响地表辐射能量收支平衡的关键参数。本文以淮河流域为例，利用MODIS（MODerate resolution Imaging Spectroradiometer）数据，采用网格趋势分析、异常变化分析、相关分析和灰色关联度分析等方法，分析了淮河流域2005～2015年地表反照率的时空变化规律，以及土地利用类型、地形因子、地表参数和气候等影响因子。结果表明:淮河流域年平均地表反照率整体呈“北高南低、东高西低”的空间分布规律，变化在0.043～0.223，平均值为 0.145。低值区主要集中于水体密集和山区丘陵地带，且标准差相对较小；高值区主要集中于流域中部及东部平原地带，且标准差较大。61.5%的区域地表反照率呈增加趋势，且存在季节性差异，夏季平均地表反照率最大，春季次之，秋季最小，冬季则由于降雪覆盖和农田利用的影响波动幅度较大。淮河流域地表反照率与归一化植被指数（Normalized Difference Vegetation Index，NDVI）、地表温度、气温和降水在大部分区域呈正相关，面积占比分别达到90.23%、82.32%、85.41%和93.70%。灰色关联度分析表明，不同土地利用类型（水体除外）下年均地表反照率受各因子影响排序为:NDVI>气温>地表温度>降水，空间变化受各因子影响排序为:NDVI>降水>地表温度>气温>高程。

Spatial and Temporal Variations of Land Surface Albedo and Its Influencing Factors Based on MODIS Data

The surface albedo represents the ability of the earth’s surface to reflect solar radiation and is a key parameter that affects the balance of surface radiation energy. Based on moderate resolution imaging spectroradiometer (MODIS) data, spatial and temporal variations of the land surface albedo and the influence of the types of land use, terrain, land surface parameters, and climate factors in the Huaihe River basin from 2005 to 2015 were analyzed using grid trend, abnormal change, correlation, and gray correlation analyses. The results show that the annual average land surface albedo of the Huaihe River basin displayed a spatial distribution pattern of “high in the north and east, low in the south and west”, varying from 0.043–0.223 with an average of 0.145. Low-value areas were mainly concentrated in regions where water is densely distributed, mountainous and hilly areas, and with a small standard deviation. High-value areas were mainly concentrated in the central and eastern plain of the basin with a relatively large standard deviation. The land surface albedo showed an increasing trend with seasonal differences in 61.5% of the area. The largest was in summer, followed by spring, and finally by autumn. In winter, the fluctuation range is larger owing to the impact of snow cover and farmland use mode. The land surface albedo positively correlated with the NDVI(Normalized Difference Vegetation Index), LST(Land Surface Temperature), air temperature, and precipitation in most areas of Huaihe River Basin, accounting for 90.23%, 82.32%, 85.41%, and 93.70%, respectively. Under different types of land use (except water), the order of the annual average gray correlation degree between the land surface albedo and the influencing factors are as follows: NDVI>air temperature>LST>precipitation, and the order of the spatial gray correlation degree is: NDVI> precipitation >LST> air temperature> elevation.