GOME data analysis and ground-based observations in the Mediterranean area during Etna volcano activity D. Bortoli (1) , G. Giovanelli (1) , F. Ravegnani (1) , I. Kostadinov (1) , A. Petritoli (1) , T. Caltabiano (2) and J. P. Burrows (3) (1) Institute of Atmospheric and Oceanic Sciences-ISAO-CNR Via Gobetti, 101- 40129, Bologna, Italy; Email: d.bortoli@isao.bo.cnr.it (2) International Institute of Vulcanology IIV-CNR Piazza Roma, 2 – 95123, Catania, Italy; Email: tommaso@iiv.ct.cnr.it (3) Institute of Environmental Physics University of Bremen, FB1, Postfach 330440 . D-28334 Bremen Germany Email: burrows@gome5.physik.uni-bremen.de ABSTRACT The ozone decline at mid-latitude could be explained by three different and concomitant mechanisms: - O 3 loss inside the arctic vortex and subsequent transport of low-level ozone air masses to mid latitudes, - local process, - chlorine activation due to extra-vortices heterogeneous reactions. A collaborative study is started with the aim to address the first two questions by means of analysis of satellite (GOME) data, integrated by ground-based measurements. Furthermore we are verifying the use of GOME data for measuring volcanic (and possibly anthropogenic) emission of SO 2 in Mediterranean area, in order to estimate climatic impact of volcanic emission and monitor potentially dangerous eruptive activity. The preliminary results are presented. INTRODUCTION In the last thirty years the stratospheric ozone at the mid-latitudes of the North Hemisphere (NH) has suffered a meaningful decreasing. The results analysis of data obtained by the TOMS (Total Ozone Mapping Spectrometer), installed on the Nimbus 7 satellite, underline the decrements of different points percentages in ozone total column also before the Pinatubo eruption. In the eighties, studies on ozone profiles temporal series in the NH show that the annual average ozone concentration increase in troposphere and decrease in the low stratosphere [1]. Other authors confirm these results [2,3], underlining that, for the South Europe, the values of the stratospheric ozone trend per decade are higher than those found in the United States, also considering areas at the same latitudes and with equal values of superficial nitrogen oxides. Comparisons on the observations results, obtained for both the hemispheres lead to the conclusion that ozone loss is smaller at high north latitudes than the Antarctic depletion phenomena. At the mid- latitudes this difference is recovered with equivalent values between 5% and 8% per decade [4], but it would seems greater in the NH. Nevertheless, the physical processes that can justify these losses in the ozone budget of the north mid-latitude, is not completely explained. The hypothesis of the air masses transport (filaments) from the polar vortex for the South Hemisphere (SH) can not be completely applied for the NH. In fact, Arctic regions shows very different meteorological conditions as higher average temperature that not favourite the PSC formation. On the other hand the less polar vortex strength allows losing its shape causing air masses intrusions until the mid-latitude. For some years the nitrogen compounds were thought to be the greatest responsible of the ozone catalytic destruction. The understanding of the dynamical processes, chemical and photochemical reactions involving nitrogen compounds in the stratosphere has improved. The existence of a winter drop in NO 2 total column at high latitude has been explained