ANALYSIS OF 5-YEAR AEROSOL DATA FROM THE STRATOSPHERIC AEROSOL AND GAS EXPERIMENT-II

The Stratospheric Aerosol and Gas Experiment (SAGE) II measured aerosol extinction coefficients at 1.02-mu-m averaged over a 10-degrees latitude band and over short periods of nearly 5 days are used for latitudinal and seasonal studies. The most evident feature of the time series is the exponential decrease confirming the decay of El Chichon influence; in some latitude bands and at several height levels, small seasonal variations are superimposed. For latitudinal variations, extinction minima at 25-degrees/35-degrees in both hemispheres appear clearly. Using aerosol extinctions at 0.525, 0.453, and 0.385-mu-m together with the 1.02-mu-m data permits one to deduce one parameter of the size distribution, the particle effective radius. Seasonal variations of the deduced aerosol radius are not so obvious compared to the extinction data, but latitudinal variations of the radius do exhibit the same behavior as the extinction data, with minima at 25-degrees/35-degrees. This study also shows that SAGE II aerosol data can be used to detect volcanic eruption from extinction variations such as the Nevado del Ruiz and to determine the size of the injected particles.