STRATOSPHERIC AEROSOL ACIDITY, DENSITY, AND REFRACTIVE-INDEX DEDUCED FROM SAGE-II AND NMC TEMPERATURE DATA

Water vapor concentrations obtained by the Stratospheric Aerosol and G as Experiment II (SAGE II) and collocated temperatures provided by the National Meteorological Center from 1986 to 1990 are used to deduce s easonally and zonally averaged acidity, density, and refractive index of stratospheric aerosols. It is found that the weight percentage of s ulfuric acid in the aerosols increases from about 60 just above the tr opopause to about 86 at 35 km. The density increases from about 1.55 t o 1.85 g cm-3 between the same altitude limits. Some seasonal variatio ns of composition and density are evident at high latitudes. The refra ctive indices at 1.02, 0.694, and 0.532 mum increase, respectively, fr om about 1.425, 1.430, and 1.435 just above the tropopause to about 1. 445, 1.455, and 1.458 at altitudes above 27 km, depending on the seaso n and latitude. The aerosol properties presented can be used in models to study the effectiveness of heterogeneous chemistry, the mass loadi ng of stratospheric aerosols, and the extinction and backscatter of ae rosols at different wavelengths. Computed aerosol surface areas, rate coefficients for the heterogeneous reaction ClONO2 + H2O --> HOCl + HN O3 and aerosol mass concentrations before and after the Pinatubo erupt ion in June 1991 are shown as sample applications.