Major Results from Sage II

Abstract

The SAGE II (Stratospheric Aerosol and Gas Experiment II) sensor was launched into a 57° inclination orbit aboard the Earth Radiation Budget Satellite (ERBS) in October 1984. During each sunrise and sunset encountered by the orbiting spacecraft, the instrument (Mauldin et al., 1985) uses the solar occupation technique to measure attenuated solar radiation through the Earth’s limb in seven channels centered at wavelengths ranging from 0.385 to 1.02 μm. The exo-atmospheric solar irradiance is also measured in each channel during each event for use as a reference in determining limb transmittances. The transmittance measurements are inverted using the “onion-peeling” approach (Chu et al., 1989) to yield 1-km vertical resolution profiles of aerosol extinction (at 0.385, 0.453, 0.525, and 1.02 μm), ozone, nitrogen dioxide, and water vapor. The focus of the measurements is on the lower and middle stratosphere, although retrieved aerosol, water vapor, and ozone profiles often extend well into the troposphere under non-volcanic and cloud-free conditions. SAGE II was preceded into orbit by sister instruments SAM II (Stratospheric Aerosol Measurement II), which has been measuring 1.0-μm aerosol extinction in the polar regions since 1978, and SAGE I, which provided near global measurements of aerosol extinction (at 0.45 and 1.0 μm), ozone, and nitrogen dioxide from 1979–1981 (McCormick et al., 1979).