基于MODIS数据反演高反射率地区气溶胶光学厚度的方法研究

Retrieval of Aerosol Optical Thickness over Bright Surface Areas Using MODIS Data

针对高反射率地区地表反射率难以确定的难点,假设在不同年间同一天相同地物的两个不同波段的比值近似相等的前提下,借助几何光学模型理论,应用MODIS历史产品和数据,即MODIS地表反射率产品(MOD09)、历史MODIS图像第七波段的地表反射率和待反演地区的MODIS第七波段的地表反射率数据计算出待反演地区的MODIS其他波段的地表反射率,然后结合利用6S辐射传输模式计算建立的查找表,可实现待反演区域的气溶胶光学厚度的反演。以北京市区为例,应用该方法实现了北京市区的气溶胶光学厚度反演,并把反演结果与AERONET观测站的结果进行了对比,对比发现该反演方法对亮区域有效,其误差在30%以内。

It is difficult to determine surface reflectance over bright surface. Based on the geometric optics model theory, it can be assumed that on the same day on the same ground two different band ratio ap- proximately equal in different years. According to the history of the MOD09 blue band surface reflectance, the MOD02 seventh band surface reflectance and the MOD02 seventh band surface reflectivity, the surface reflectance of retrieval region can be obtained, and 6S radiation transmission is combined to build look-up table, to retrieve aerosol optical thickness of Beijing Area. Beijing AERONET site observations data is used to verify the outcome, the results have a good consistency with AERONET data over bright surface, and the error is less than 30%.