A Technique for Estimating Polar Ozone Loss: Results for the Northern 1991/92 Winter Using EASOE Data

In this paper we describe a technique for estimating chemical ozone loss in the Arctic vortex. Observed ozone and temperature profiles are combined with the model potential vorticity field to produce time series of vortex averaged ozone mixing ratios on chosen isentropic surfaces. Model-derived radiative heating rates and observed vertical gradients of ozone are then used to estimate the change in ozone that would occur due to diabatic descent. Discrepancies with the observed ozone are interpreted as being of chemical origin, assuming that there is negligible horizontal transport or mixing of air into the vortex. The technique is illustrated using ozone sonde measurements collected during the 1991/92 European Arctic Stratospheric Ozone Experiment (EASOE), meteorological analyses from the European Centre for Medium-range Weather Forecasts (ECMWF) and radiative heating rates extracted from the Global Atmospheric Modelling Programme (UGAMP) 3D General Circulation Model. Our results show that there was photochemical ozone destruction inside the Arctic vortex in early 1992 with a loss between 475 K and 550 K (around 20 km) of 0.32±0.15 ppmv in the first 20 days of January, equivalent to a rate of 0.51±0.24%/day (at the 95% confidence level).