Improved Experiment Of Aerosol Optical Depth Retrieval Over Lanzhou Area By6S Model

The study of atmospheric aerosols is an important subdiscipline of atmospheric sciences.With more and more concern about the Global Climate Change, more attention to the role of aerosols in Climate Change have been paid. Atmospheric aerosol particles are important component of the atmospheric environment, which are widely distributed in atmosphere. The atmospheric Aerosol Optical Depth(AOD) is an important physical variable of the characterization of atmospheric turbidity and one of the most important aerosol parameters.In this paper, high spatial resolution (2.5km×2.5km) AOD at550nm wavelength over Lanzhou area are retrieved by the6S Radiative Transfer Model with Kaufman’s extended dark target method. A revision experiment of the MODIS data by Walthall BRDF model has been taken and a user-defined localized aerosol model was employed in order to improve retrieved accuracy of the AOD over Lanzhou. A case study was explored under the condition of dust event. The inter-comparison were conducted between the inversion results and the ground-based observations(CE-318) at SACOL and the AOD product of NASA mod04. Preliminary test of the effects of both the surface bidirectional reflectance properties(BRDF) and self-defined aerosol model were processed for the retrieval accuracy of AOD over Lanzhou area. The main results are as follows:1) The results of AOD retrieved over Lanzhou area show that, there are some high centers of AOD over Lanzhou city and the surrounding areas, which is well coincide with the actual distribution of aerosols.2) The results of improved experiment with Walthall BRDF model show that surface bidirectional property has an important impact on surface reflectance’s accurate estimate. Significant improvements have taken place with the Walthall BRDF model over the water surface, to some extent.3) The inversion results with self-defined aerosol model indicate that the custom and localized aerosol model can be used for the improvement of the accuracy of retrieve aerosol optical depth. 4) The experiment in dust days retreive the AOD, using the surface reflectance on background days, show that the inversion accuracy is higher than that in the direct retrieval results.