Spectroscopic measurements of the 8- to 13-micrometer transmission of the upper atmosphere following the El Chichon eruptions

Infrared transmission spectra of the atmosphere above 11-km altitude were obtained at latitudes from 2 deg S to 50 deg N in December 1982. A circular variable-interference filter spectrometer mounted in a Convair 990 (the Galileo II) aircraft was used to obtain spectra of the sun through different air masses. Comparisons of spectra through different air masses provide atmospheric transmission measurements that show not only normal absorption features, such as those from CO2 and O3, but also additional absorption near 8.5 microns consistent with H2SO4 aerosols. The average fractional absorption from latitude 10 deg N to 41 deg N at 8.5 microns was 0.02/air mass, half of which was attributable to aerosols.