详细介绍了MODIS气溶胶C005产品算法的改进情况。选择北京、榆林为试验区, 利用AERONET地基观测的气溶胶光学厚度数据, 对比分析了上午星TERRA、下午星AQUA的MODIS气溶胶C004、C005新旧产品的精度, 评价了它们在中国北方地区的适用性。采用波长插值、时空匹配将地基数据和MODIS 气溶胶产品匹配在一起, 然后采用线性拟合的方法进行对比分析。文中就MODIS气溶胶产品和地基数据的时空匹配, 摒弃了NASA关于MODIS气溶胶产品在全球所采用的方法, 引入当地月平均风速, 提出了中国北方地区时空匹配尺度。对比分析以及评价结果表明: (1) C005产品算法的改进并没有提高北京站点气溶胶光学厚度的精度, 在AOT<0.8时反而是下降的; C004、C005产品在北京站点不具有显著适用性, 但C004比C005产品效果好。(2) 榆林站点, TERRA-MODIS C004产品能够达到需求标准, 而AQUA-MODIS C004精度有所下降; 两星的C005产品精度较C004有很大程度的改善, 470、550、660nm 3个波段的气溶胶光学厚度与AERONET地基观测数据的相关系数均高于0.9, 具有显著适用性。这说明了新算法所采用的确定地表反射率的方法在植被覆盖好的地区是可行的, 在高反射地区效果不好。

MODIS aerosol product Collection 005 (C005) is an upgrade of C004, and is introduced in detail in this paper. Through fitting with AERONET ground observation aerosol optical thickness (AOT), MODIS aerosol C004 and C005 products of TERRA and AQUA are compared and evaluated to analyze their applicability in the north of China at Beijing and Yulin sites. We match AERONET ground-based data with MODIS aerosol product by band interpolation and temporal-spatial matching, then compare and evaluate them by linear fitting. We conceive a scale of temporal-spatial matching in the north of China considering the local aerosol movement velocity of given sites. The results show that: (1) C005 product algorithm does not improve the accuracy of AOT at Beijing site, and the accuracy drops when AOT< 0.8; both C004 and C005 products do not have a significant application at Beijing site, but the C004 performs better than C005 products. (2) At Yulin site, TERRA-MODIS C004 product meets the demand, and the accuracy of AQUA-MODIS C004 product decreases. Compared with the C004 product, the accuracy of the C005 product improves greatly, and correlation coefficients between AOTs of three bands (470nm, 550nm, 660nm) and the AERONET ground observation data are all higher than 0.9. It could be concluded that the method of the surface reflectance determination used in the new algorithm is feasible for dark dense vegetation, but is not suitable for the bright surface.