利用MODIS卫星资料对比反演兰州地区气溶胶光学厚度

The Aerosol Optical Depth over Lanzhou Area Retrieved with a Compared Method Using MODIS Data

Kaufman的暗像元方法是目前利用MODIS卫星资料反演气溶胶光学厚度的方法之一,但在获取可见光通道地表反射率时存在局限性。我们用一种对比方法进行了反演试验,研究了反演粒径较大的气溶胶光学厚度的可行性。用6S辐射传输模式模拟了两天的表观反射率差异对气溶胶光学厚度的敏感性;利用两天(“清洁日”和“污染日”)MODIS的红、蓝和近红外通道表观反射率资料,通过查算表反演了水面上空的气溶胶光学厚度和几何平均质量粒径;在此基础上反演了兰州地区气溶胶光学厚度的分布情况。反演结果与地面光度计观测作了比较,两者比较接近,说明反演方法是可行的。

The dark target method developed by Kaufman is one of methods to retrieve the aerosol optical depth using MODIS data. But there is limitation in getting the surface reflectivity of visible channel. In this paper we demonstrate an experiment with a compared method to study the feasibility of retrieving aerosol optical depth for large particle size. The sensitivity of two day＇s difference of apparent reflectivity to aerosol optical depth was simulated with 6S model. The aerosol optical depth and particle geometrical mean mass radius over water was retrieved with a LUT using two day＇s MODIS data. The aerosol optical depth over Lanzhou area was retrieved and the result is close to the sun photometer measurements on the ground, which indicates the method is feasible.