Lagrangian estimation of ozone loss in the core and edge region of the Arctic polar vortex 1995/1995: Model results and observations.

Lukyanov A., Nakane H., Yushkov V.,

Journal of Atmospheric Chemistry. v 44, pp 191-210, 2003.


Abstract

Ozone evolution and diabatic descent in the Arctic polar vortex in winter 1995/1996 was studied with a newly developed diabatic trajectory–chemistry model (DTCM). To study the chemical and dynamic evolution of the species in the polar vortex, 400 diabatic trajectories were calculated in the vortex core and edge region by using three-dimensional (3-D) wind data provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). The averaged diabatic descending motion and ozone behavior were obtained for particles started from the core and from the edge region of the vortex. The difference in ozone-loss rates as well as the difference in descending rates between the vortex core and the vortex-edge region was not statistically significant. The average cumulative ozone loss of 65 % in the vortex core obtained from the model calculations was consistent with the estimates obtained with a different method (Match experiment).
The model results for the vortex core were compared with those obtained using trajectories with the vertical winds calculated on the basis of radiative cooling rates as used by the SLIMCAT 3-D chemical transport model. Although the trajectories based on cooling rates exhibited lower descending rates than those based on 3-D analyzed wind data, the ozone behavior was similar for both types of trajectory. Ozonesonde data from two stations (Ny-Alesund in the vortex core and Yakutsk in the vortex edge) were compared with the model results. For Lagrangian estimation of the ozone loss at these stations, the descending rates obtained by the diabatic trajectory calculations were used. Good agreements were obtained between the model results and observations for both the vortex core and edge region. These results suggest that strong ozone depletion occurred not only in the core, but also in the edge region of the vortex, and that air masses from the mid-latitudes did not appreciably affect the degree of ozone depletion in this winter–spring period. The sensitivity of the model to different descending rates and to the presence of large nitric acid trihydrate (NAT) particles was also examined.