[The retrieval of fine and coarse aerosol from MODIS]

Generally, aerosols over land are composed of fine and coarse aerosols, which have different optical properties. How to derive the fine mode and coarse mode aerosols from satellite observations is an important issue in the aerosol retrieving. In the present paper, information of aerosol models (including refractive index and size distribution function) was retrieved from the ground-based measurement of the AERONET/PHOTONS site in Beijing. The retrievals indicate that, aerosols over Beijing have a bi-model distribution, and the optical properties of fine and coarse aerosols are distinct. Based on the dark dense vegetation (DDV) method, optical depth of the fine, coarse and total aerosols were derived from MODIS data over Beijing area in 2007. The validation of these satellite retrievals shows that from MODIS data, the optical depth of fine and total aerosols can be retrieved well (with correlation coefficients greater than 0.8), and so can the Angstrom exponent (having a correlation coefficient of 0.517). However, relatively poor results were obtained when retrieving the optical depth of coarse aerosols.