The influence of polar vortex ozone depletion on NH mid-latitude ozone trends in spring

[摘要] Reverse domain-filling trajectory calculations have been performed for theyears 1993, 1995, 1996, 1997, and 2000 to calculate the spreading of ozonedepleted air from the polar vortex to midlatitudes in spring. We find thatfor these years with massive Arctic ozone depletion the zonal mean totalozone column at midlatitudes is reduced with between 7 and 12DU in theApril-May period. The polar vortex and remnants have preferred locationswhich leads to longitudinal differences in the midlatitude ozone trends.Together with decadal variations in circulation the dilution of ozone depletedair may explain the major fraction of longitudinal differences in midlatitudeozone trends. For the period 1979–1997 the dilution may explain 50% of thelongitudinal differences in ozone trends and for the period 1979–2002 it mayexplain 45%. The dilution also has a significant impact on the zonal meanozone trends in the April-May period. Although uncertainties are large due touncertainties in the ozone depletion values and neglect of ozone depletion inother years than 1993, 1995, 1996, 1997, and 2000 we have tried to calculatethe size of this effect. We estimate that dilution mayexplain 29% of the trend in the period 1979–1997 and 33% of the trend inthe period 1979–2002 as a lower limit.

[学科分类] 大气科学