Seasonal start of the Antarctic ozone hole derived from observations with Dobson spectrophotometers

Abstract

The Antarctic ozone hole appears in the Antarctic spring, just after the polar night period when sunlight is not available on the surface. Because it is not possible to have a large solar elevation angle in the Antarctic winter and spring, it is hard to make observations of total ozone amounts with TOMS or Dobson spectrophotometers using sunlight. Because of this there is not enough information about the total ozone amounts over the Antarctic just before and after the seasonal appearance of the Antarctic ozone hole. We have made an analysis of the total ozone amounts with a Dobson spectrophotometer, using moonlight as well as sunlight at the three Antarctic stations and Macquarie Island. The results derived from the analysis are as follows: (1) The decrease of the total ozone amounts leading to the Antarctic ozone hole started at the beginning of August at around 69° south and then took place at the higher latitudes later in the period from 1993 to 2005: (2) The total ozone amounts at the higher latitudes in the Antarctic show the smaller value as a latitudinal gradient of about 1.6 DU per degree in the period from 1993 to 2005. The author hopes that these results will be useful for better understanding of the Antarctic ozone hole.

Acknowledgements

The author is thankful to the members of the Japanese Antarctic Research expedition who conducted the ozone observation at Syowa Station, Antarctica. The author is also thankful to Y Sato and M. Deushi of Meteorological Research Institute, JMA and K. Miyagawa of the Aerological Observatory, JMA for their comments and advices.