Record ozone minimum over middle and high latitudes of the northern hemisphere during the winter-spring seasons 1991/92 and 1992/93
Bojkov, R. D., C. S. Zerefos, D. S. Balis, I. C. Ziomas, A. F. Bais
[abstract] The last two winter-spring seasons (DJFM) distinguished themselves by being with the lowest ever total ozone over all three continental size regions between 45-degrees-N and 65-degrees-N of North America, Europe and Siberia. The total ozone deficiencies for the entire season over all of the above mentioned regions were about 11% and 13% below the long-term normal during the two consecutive years (1991/92 and 1992/93 respectively). This helped to pull down the cumulative ozone decline since the winter-spring of 1969/70 to be about 14% in the latitude belt of the 45-degrees-N- 65-degrees-N. Frequencies of days with ozone values deviating below the long-term mean by more than 2sigma have been ten times higher than their 35-year average. There are evidences deduced from trajectories on potential temperature surfaces that transport of poor in ozone air masses forced in addition by vertical motions, could account for a number of the extreme cases. There is also evidence that cold air, known to have excess ClO content, has moved over the sun lighted latitudes on many occasions, when chemical ozone destruction could have been favored. These ozone deficiencies do not have similar rates of decline and did not reach even close to the extreme low values regularly observed during the Antarctic-spring ozone hole phenomena.
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