基于MODIS数据的城市气溶胶光学厚度反演方法

遥感的方法为大面积获取气溶胶光学厚度提供了手段。目前使用MODIS(中分辨率成像光谱仪)数据反演气溶胶光学厚度常用的是暗像素方法以及对比法。由于城市地区符合暗像素标准的像素较少,而且城市地区的气溶胶成分复杂,难以确定其具体成分,所以暗像素方法会产生较大误差。根据MODIS第7、3、1波段对气溶胶的不同响应,以三者的反射率为自变量,结合地面实地观测数据,给出了计算北京地区气溶胶光学厚度的计算公式,误差分析表明该方法更适合城市地区。

Urban Aerosol Optical Thickness Retrieval from MODIS Data

Aerosol plays an important role in global climate change and remote sense provides a better
method to retrieve aerosol optical thickness (AOT) at large scale. Currently dark object subtraction and
contrast reduction method are two widely used methods for MODIS data to get AOT. Due to the facts that
there are few pixels whose reflectance in urban area are not small enough, the urban aerosols are from
multi-sources and their components are difficult to verify, dark object method may lead to big errors if it is
used in urban area. Here the different response of MODIS band 7, 3, 1 to aerosol are used together with
the ground based measurements, a formula is put forward asτ= 4.4376×ρ7+50.5579×ρ3-24.3317×ρ1
-3.5575 to calculate AOT in urban area. The error analysis shows that the error of 81% results is less
than 10% and 61% is less than 6%. This formula is derived from the data observed in one day. The more
accurate result can be derived from the meteorological data provied by hundreds of weather sations.