Mountain waves, polar stratospheric clouds, and the ozone depletion over Antarctica

We report observations of ozone column and clouds at typically stratospheric altitudes, obtained during the 1987 Airbone Antarctic Experiment from the TIROS Operational Vertical Sounder (TOVS)/High-Resolution Infrared Sounder (HIRS 2) instrument on the National Oceanic and Atmospheric Administration NOAA 10 satellite. Cloud formation occurs mainly along the coast of Antarctica when strong tropospheric winds blow from the ocean to the continent. The period of September 2–9 provides a good example of the formation of localized high-altitude clouds over the Palmer Peninsula and the Weddell Sea. The appearance of these clouds (a subset of the more prevalent polar stratospheric clouds (PSCs)) is consistent with the presence of a strong tropospheric jet over the elevated topography of the peninsula. Mountain waves and their associated high-altitude adiabatic cooling are the driving mechanism for the cloud formation. On the basis of the cloud area coverage and wind analyses, we estimate that in the altitude range 14–18 km the air within the polar vortex has spent 5% of its time inside these clouds from early August to late September. The importance of this observation for springtime ozone depletion mechanisms is discussed. It is also concluded that the TOVS data set recorded during the past decade would be suitable to search for a possible trend in the cloud amount. Such a trend could be relevant to the rate of the Antarctic ozone depletion.

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