TEMPORAL DEVELOPMENT OF OZONE WITHIN THE ARCTIC VORTEX DURING THE WINTER OF 1991 92/

In this study we address the question of temporal ozone trends on isen tropic surfaces within the Arctic polar vortex during EASOE. We have c ombined ozone sonde data from twelve campaign stations distributed thr oughout the European sector of the Arctic. The development of ozone at the 425, 475, 550 and 700K levels is presented, using analysed fields of isentropic potential vorticity and isentropic back-trajectories to separate inner vortex air from air staying outside the vortex. Vertic al N2O profiles measured in Kiruna have been used to obtain informatio n on the vertical movement of the polar air mass. Elimination of effec ts due to diabatic descent leads to a weak, yet significant, chemicall y induced loss of ozone at 475K. At 425K we observe a negative trend i n the ozone mixing ratio, but for this level it has not been possible to assess the influence of subsidence. Heterogeneous chemistry on aero sols of volcanic origin from the eruption of Mt. Pinatubo might have c ontributed to the negative ozone trends.