Evaluation Of The Modis V5.2 Algorithm Over Land In China And Algorithm Research

Aerosol is a suspension of solid or liquid particles in a gas. Aerosol plays an important role in the earth-atmosphere radiation budget and global climate, either directly through their scattering and absorption of radiation, or as cloud condensation nuclei to affect micro-physical properties of clouds indirectly, thereby change the precipitation and cloud lifetime. Furthermore, aerosol also plays an important role in many geophysical and chemical processes. China has vast territory, complex surface conditions and diverse ecological types. The ground-based sites which observations aerosol in long-term are few in China. Therefore, Satellite remote sensing for aerosol has become the only mean to acquire the regional distribution of aerosol and improving the inversion accuracy of satellite remote sensing has become the current problem to be solved.In this paper, the research status in quo of remote sensing of aerosol has been systematic reviewed. We introduce the MODIS V5.2 algorithm for remote sensing of aerosol properties over land and summary the change between the MODIS V5.2 algorithm with the previous algorithm. On this basis, using part of the AERONET data (Level 2.0) did a detailed assessment for MODIS aerosol products's applicability and accuracy in the Chinese region. The results showed that the inversion accuracy of MODIS aerosol products in China has a great regional differences and seasonal changes.In order to reduce the regional differences and seasonal changes of aerosol retrieval products, this paper presents a fast algorithm for retrieval of aerosol optical thickness over land. This algorithm deal with the surface reflectance relationships is the same as MODIS V5.2 algorithm. Considering the fine structure of the aerosol size distribution has a little effect for satellite remote sensing of aerosol optical thickness, this algorithm using the Junge aerosol size distribution to approximate the aerosol size distribution in an actual atmosphere. The setting of optical properties of the aerosol model is different with MODIS algorithm parameters.This algorithm uses the MODIS 1B data at Taihu and Xianghe to inversion aerosol optical thickness. And this inversion results is compared with equivalent measurements from AERONET site (Level 2.0 data). This comparison result is used to test the accuracy and regional applicability of the algorithm. The results showed that this algorithm inversion results have good consistency with the sun photometer observational results at Taihu and Xianghe. The inversion algorithm is more accurate than the current MODIS aerosol algorithm and its inversion results are reasonable. These results indicate the new algorithm has higher inversion accuracy and better regional applicability. In addition, the settings for aerosol model and optical properties are simple and convenient in the new algorithm, which can effectively reduce the computational time for look-up table and iteration time for Solution of equation.