Satellite observations of aerosol surface area and volume densities at upper troposphere and lower stratosphere from 1985 to 1999

In a recent paper by Yue [1999], a new method to retrieve aerosol size distributions and integral properties from SAGE II aerosol extinction spectra was proposed. In this method, the aerosol number density, as well as the surface area and volume densities, are expressed as a linear combination of the SAGE II aerosol extinctions at four or fewer wavelengths. It was found that when all four aerosol extinctions are available for retrieval, the retrieval errors for surface area and volume densities are less than about 20 and 10%, respectively. At lower altitudes where less than four aerosol extinctions are measured, the retrieval errors are slightly higher. The proposed linear minimizing error method was applied to retrieve aerosol surface area and volume densities in the upper troposphere and lower stratosphere from 1985 to 1999. The deduced aerosol properties are presented. Preliminary analysis of the data indicates an increase of aerosol surface area and volume densities in both the upper troposphere and lower stratosphere each time after a major volcanic eruption. The decay of aerosol integral properties after volcanic eruption and the hemispheric asymmetry of aerosol properties are discussed.