Comparison of trends in the tropospheric and stratospheric aerosol optical depths in the Antarctic

Abstract

Temporal variations of the aerosol optical depth of the Antarctic troposphere and stratosphere are considered on the basis of long‐term Sun photometer and actinometer measurements which have been made at Mirny and Georg Forster stations since 1956 and 1988, respectively. This data is supplemented by measurements of the stratospheric aerosol optical depth by the satellite‐borne stratospheric aerosol measurement II instrument. These observations indicate that under undisturbed conditions, the stratospheric aerosol optical depth represents approximately 25% of the total atmospheric aerosol optical depth. The aerosol optical depth in the Antarctic is most notably affected by volcanic eruptions, such as El Chichon in 1982 and Mount Pinatubo and Cerro Hudson in 1991, and by the occurrence of polar stratospheric clouds during Antarctic winter and spring. Apart from these episodic events, no long‐term trend in the aerosol optical depth can be discerned from the nearly 40‐year record.