Comparing Aerosol Microphysical Properties Measured by SAGE II and III

The Stratospheric Aerosol and Gas Experiment (SAGE) II and III are two satellite experiments designed to monitor aerosol and trace gases in the atmosphere using the solar and/or lunar occultation technique. The objective of this study is to retrieve and compare microphysical properties of aerosol particles in the upper troposphere and lower stratosphere measured by both experiments between 2002 and 2005. In these years stratospheric aerosols are regarded as "background," because their mass loading was at a minimum level and continued to remain almost at the same level for a couple of years. The microphysical properties under investigation are the aerosol composition and mass density. The size distribution of background aerosol particles is assumed to be lognormal with a single mode. The parameters in the lognormal expression are retrieved by applying the Linear Minimizing Error (LME) technique. The aerosol particles are assumed to be sulfuric acid droplets with partial water vapor pressure in equilibrium with the ambient value. The global distributions of aerosol composition and mass density for different seasons are presented and discussed. In some high latitudes of both hemispheres when SAGE II and SAGE III conducted measurements, there are opportunities for comparison study. We assume there is a coincidence when measurements were conducted on the same day and the latitudinal and longitudinal differences were less than 2o and 5o, respectively. It was found that the aerosol compostion measured by both experiments are in good agreement, but the mass densities meausred by SAGE III are in generla, about 10 to 20% higher than the corresponding SAGE II values.