OBSERVATIONS OF ABSORBING LAYERS IN THE ANTARCTIC STRATOSPHERE IN OCTOBER 1991

Measurements of the transmission of solar infrared radiation through the earth's atmosphere, by the HALOE experiment on the UARS spacecraft, were made at high southern latitudes during October 1991. These observations are direct measurements of atmospheric transmission, and do not need to be passed through a composition or temperature retrieval process; they are, therefore, amenable to direct interpretation. During October 1991 the profiles of transmittance versus height in the atmosphere show clear evidence for the arrival (from more northerly latitudes) of layers of some material which absorbs infrared radiation, at heights of up to 28 km. The spatial structure of the absorbing material shows considerable variability with longitude at a given latitude. The spectral properties of the detected absorption, measured at the various HALOE wavelengths, are consistent with absorption by sulphate aerosol, and clearly implicate the volcanic eruptions from Mts Pinatubo and Hudson during 1991. These results provide direct and detailed evidence for the arrival of layers of what appears to be sulphate aerosol during the 1991 southern spring, at latitudes as high as 80 degrees south.