A case study of the low total ozone event over Europe on 14 February 2001

Abstract

A low total ozone event was observed over the Baltic Sea on 14 February 2001. This was of interest because the polar vortex in the stratosphere associated with this event moved eastward and covered Japan several days later. The central location of the observed low total ozone event on 14 February 2001 was around 59° N 23° E. Over this location, the total ozone amount was at the lowest (225 DU (Dobson units)) on 14 February. Correlation analyses were conducted on the isentropic surfaces of Central Europe in order to ascertain the mechanism of this event. It was found that there was an uplift of the isentropic surface between 330 K and 750 K and a downward shift of the 300 K isentropic surface associated with this event. It was also found associated with this event, that the ozone mixing ratio decreased on almost all the isentropic surfaces except over 400 K and 450 K. It is noted that the region between the 300 K and 350 K isentropic surfaces was filled by the air mass from lower latitudes, and that the 450 750 K isentropic surfaces were covered with the air mass from higher latitudes. It is demonstrated that the chemical effects caused by low temperature were so small for the total ozone loss event on 14 February 2001. Hence, it is suggested that the primary reason for the low total ozone event on 14 February 2001 is a dynamical one.

Acknowledgements

The authors would like to thank M. Hirota of the Aerological Observatory, Japan for his encouragement and discussions. They also would like to thank O. Arakawa and I. Takayabu of the Meteorological Research Institute (MRI) Japan for their advice. The authors are indebted to K. Rajendran of the MRI for critical reading of the manuscript. TOMS (version 8) data were obtained from the TOMS web page of NASA. Ozone sonde data were obtained from the WOUDC web page of the Meteorological Service of Canada.