PINATUBO AEROSOLS AND THE BEHAVIOR OF OZONE INFERRED FROM BACKSCATTERULTRAVIOLET MEASUREMENTS ON THE SPACE-SHUTTLE

Backscattered radiation measurements from the shuttle solar backscatte r ultraviolet spectral radiometer were used to examine aerosol optical properties and a possible ozone decrease in the tropical region after the eruption of Mt. Pinatubo. Observations made on two flights separa ted in time by 10 months show that backscattered ultraviolet radiation was greatly enhanced after the eruption as compared to the earlier me asurements. The enhancements in backscattered radiation exhibit a spec ial wavelength dependent signature. The peak percentage enhancement wa s found near 302 nm for solar zenith angles greater than 20 degrees, c orresponding to the latitude band 14 degrees S-14 degrees N. Radiative transfer calculations indicate that the wavelength dependence of the enhancement is consistent with an ozone decrease in the altitude regio n of the Pinatubo aerosol clouds. The Pinatubo aerosol optical depth w as found to vary in the range 0.07-0.53 in the ultraviolet region at t ropical latitudes. Furthermore, a 16-22 Dobson unit decrease of ozone in the altitude region occupied by the aerosol cloud is consistent wit h the spectral dependence of the enhanced backscattered radiance.