Evolution of stratospheric ozone during winter 2002/2003 as observed by a ground-based millimetre wave radiometer at Kiruna, Sweden
[摘要] We present ozone measurements from the millimetre wave radiometerinstalled at the Swedish Institute of Space Physics (Institutetför rymdfysik, IRF) in Kiruna (67.8° N, 20.4° E,420 m asl).Nearly continuous operation in the winter of2002/2003 allows us to give an overview of ozone evolution in thestratosphere between 15 and 55 km.
In this study we present a detailed analysis of the Arctic winter2002/2003. By means of a methodology using equivalent latitudes weinvestigate the meteorological processes in the stratosphere duringthe entire winter/spring period. During the course of the winterstrong mixing into the vortex took place in the middle and upperstratosphere as a result of three minor and one major warming event,but no evidence was found for significant mixing in the lowerstratosphere.Ozone depletion in the lower stratosphere during this winter wasestimated by measurements on those days when Kiruna was well insidethe Arctic polar vortex. The days were carefully chosen using adefinition of the vortex edge based on equivalent latitudes. At the475 K isentropic level a cumulative ozone loss of about0.5 ppmv was found starting in January and lasting untilmid-March. The early ozone loss is probably a result of the verycold temperatures in the lower stratosphere in December and thegeographical extension of the vortex to lower latitudes where solarirradiation started photochemical ozone loss in the pre-processedair.In order to correct for dynamic effects of the ozone variation dueto diabatic subsidence of air masses inside the vortex, we usedN2O measurements from the Odin satellite for the same timeperiod. The derived ozone loss in the lower stratosphere betweenmid-December and mid-March varies between 1.1±0.1 ppmvon the 150 ppbv N2O isopleth and 1.7±0.1 ppmvon the 50 ppbv N2O isopleth.
