| We present ozone measurements from the millimetre wave radiometer
installed at the Swedish Institute of Space Physics (Institutet
för rymdfysik, IRF) in Kiruna (67.8° N, 20.4° E,
420 m asl). Nearly continuous operation in the winter of
2002/2003 allows us to give an overview of ozone evolution in the
stratosphere between 15 and 55 km.
In this study we present a detailed analysis of the Arctic winter
2002/2003. By means of a methodology using equivalent latitudes we
investigate the meteorological processes in the stratosphere during
the entire winter/spring period. During the course of the winter
strong mixing into the vortex took place in the middle and upper
stratosphere as a result of three minor and one major warming event,
but no evidence was found for significant mixing in the lower
stratosphere.
Ozone depletion in the lower stratosphere during this winter was
estimated by measurements on those days when Kiruna was well inside
the Arctic polar vortex. The days were carefully chosen using a
definition of the vortex edge based on equivalent latitudes. At the
475 K isentropic level a cumulative ozone loss of about
0.5 ppmv was found starting in January and lasting until
mid-March. The early ozone loss is probably a result of the very
cold temperatures in the lower stratosphere in December and the
geographical extension of the vortex to lower latitudes where solar
irradiation started photochemical ozone loss in the pre-processed
air.
In order to correct for dynamic effects of the ozone variation due
to diabatic subsidence of air masses inside the vortex, we used
N2O measurements from the Odin satellite for the same time
period. The derived ozone loss in the lower stratosphere between
mid-December and mid-March varies between 1.1±0.1 ppmv
on the 150 ppbv N2O isopleth and 1.7±0.1 ppmv
on the 50 ppbv N2O isopleth. |