Satellite aerosol retrieval using dark target algorithm by coupling BRDF effect over AERONET site

Leiku Yang; Yong Xue; Jie Guang; Chi Li

doi:10.1117/12.977186

13 November 2012 Satellite aerosol retrieval using dark target algorithm by coupling BRDF effect over AERONET site

Leiku Yang, Yong Xue, Jie Guang, Chi Li

Proceedings Volume 8523, Remote Sensing of the Atmosphere, Clouds, and Precipitation IV; 85231J (2012) https://doi.org/10.1117/12.977186
Event: SPIE Asia-Pacific Remote Sensing, 2012, Kyoto, Japan

Abstract

For most satellite aerosol retrieval algorithms even for multi-angle instrument, the simple forward model (FM) based on Lambertian surface assumption is employed to simulate top of the atmosphere (TOA) spectral reflectance, which does not fully consider the surface bi-directional reflectance functions (BRDF) effect. The approximating forward model largely simplifies the radiative transfer model, reduces the size of the look-up tables, and creates faster algorithm. At the same time, it creates systematic biases in the aerosol optical depth (AOD) retrieval. AOD product from the Moderate Resolution Imaging Spectro-radiometer (MODIS) data based on the dark target algorithm is considered as one of accurate satellite aerosol products at present. Though it performs well at a global scale, uncertainties are still found on regional in a lot of studies. The Lambertian surface assumpiton employed in the retrieving algorithm may be one of the uncertain factors. In this study, we first use radiative transfer simulations over dark target to assess the uncertainty to what extent is introduced from the Lambertian surface assumption. The result shows that the uncertainties of AOD retrieval could reach up to ±0.3. Then the Lambertian FM (L_FM) and the BRDF FM (BRDF_FM) are respectively employed in AOD retrieval using dark target algorithm from MODARNSS (MODIS/Terra and MODIS/Aqua Atmosphere Aeronet Subsetting Product) data over Beijing AERONET site. The validation shows that accuracy in AOD retrieval has been improved by employing the BRDF_FM accounting for the surface BRDF effect, the regression slope of scatter plots with retrieved AOD against AEROENET AOD increases from 0.7163 (for L_FM) to 0.7776 (for BRDF_FM) and the intercept decreases from 0.0778 (for L_FM) to 0.0627 (for BRDF_FM).

Citation Download Citation

Leiku Yang, Yong Xue, Jie Guang, and Chi Li "Satellite aerosol retrieval using dark target algorithm by coupling BRDF effect over AERONET site", Proc. SPIE 8523, Remote Sensing of the Atmosphere, Clouds, and Precipitation IV, 85231J (13 November 2012); https://doi.org/10.1117/12.977186

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