The influence of polar vortex ozone depletion on NH mid-latitude ozone trends in spring S. B. Andersen and B. M. Knudsen Department of Research and Development, Danish Meteorological Institute, Lyngbyvej 100, 2100 Copenhagen Ø, Denmark
Abstract. Reverse domain-filling trajectory calculations have been performed for the
years 1993, 1995, 1996, 1997, and 2000 to calculate the spreading of ozone
depleted air from the polar vortex to midlatitudes in spring. We find that
for these years with massive Arctic ozone depletion the zonal mean total
ozone column at midlatitudes is reduced with between 7 and 12 DU in the
April-May period. The polar vortex and remnants have preferred locations
which leads to longitudinal differences in the midlatitude ozone trends.
Together with decadal variations in circulation the dilution of ozone depleted
air may explain the major fraction of longitudinal differences in midlatitude
ozone trends. For the period 1979–1997 the dilution may explain 50% of the
longitudinal differences in ozone trends and for the period 1979–2002 it may
explain 45%. The dilution also has a significant impact on the zonal mean
ozone trends in the April-May period. Although uncertainties are large due to
uncertainties in the ozone depletion values and neglect of ozone depletion in
other years than 1993, 1995, 1996, 1997, and 2000 we have tried to calculate
the size of this effect. We estimate that dilution may
explain 29% of the trend in the period 1979–1997 and 33% of the trend in
the period 1979–2002 as a lower limit.
Citation: Andersen, S. B. and Knudsen, B. M.: The influence of polar vortex ozone depletion on NH mid-latitude ozone trends in spring, Atmos. Chem. Phys., 6, 2837-2845, doi:10.5194/acp-6-2837-2006, 2006.