Variability in Antarctic ozone loss in the last decade (2004–2013): high-resolution simulations compared to Aura MLS observations

摘要

A detailed analysis of the polar ozone loss processes during 10 recentAntarctic winters is presented with high-resolution MIMOSA–CHIM (ModèleIsentrope du transport Méso-échelle de l'Ozone Stratosphériquepar Advection avec CHIMie) modelsimulations and high-frequencypolar vortex observations from the Aura microwave limb sounder (MLS)instrument. The high-frequency measurements and simulations help tocharacterize the winters and assist the interpretation of interannualvariability better than either data or simulations alone. Our model resultsfor the Antarctic winters of 2004–2013 show that chemical ozone loss startsin the edge region of the vortex at equivalent latitudes (EqLs) of65–67° S in mid-June–July. The loss progresses with time athigher EqLs and intensifies during August–September over the range400–600 K. The loss peaks in late September–early October, when allEqLs (65–83° S) show a similar loss and the maximum loss (>2 ppmv – parts per million by volume) is found over a broadvertical range of 475–550 K. In the lower stratosphere, most wintersshow similar ozone loss and production rates. In general, at 500 K,the loss rates are about 2–3 ppbv sh?1 (parts per billion by volumeper sunlit hour) in July and 4–5 ppbv sh?1 in August–mid-September,while they drop rapidly to 0 by mid-October. In the middlestratosphere, the loss rates are about 3–5 ppbv sh?1 in July–Augustand October at 675 K. On average, the MIMOSA–CHIM simulations showthat the very cold winters of 2005 and 2006 exhibit a maximum loss of~ 3.5 ppmv around 550 K or about 149–173 DU over350–850 K, and the warmer winters of 2004, 2010, and 2012 show aloss of ~ 2.6 ppmv around 475–500 K or131–154 DU over 350–850 K. The winters of 2007, 2008, and2011 were moderately cold, and thus both ozone loss and peak loss altitudesare between these two ranges (3 ppmv around 500 K or150 ± 10 DU). The modeled ozone loss values are in reasonably goodagreement with those estimated from Aura MLS measurements, but the modelunderestimates the observed ClO, largely due to the slower vertical descentin the model during spring.