TROPOSPHERIC OZONE DEPLETION IN POLAR-REGIONS - A COMPARISON OF OBSERVATIONS IN THE ARCTIC AND ANTARCTIC

The dynamics of tropospheric ozone variations in the Arctic (Ny-Alesun d, Spitsbergen, 79 degrees N, 12 degrees E) and in Antarctica (Neumaye r-Station, 70 degrees S, 8 degrees W) were investigated for the period January 1993 to June 1994. Continuous surface ozone measurements, ver tical profiles of tropospheric ozone by ECC-sondes, meteorological par ameters, trajectories as well as ice charts were available for analysi s. Information about the origins of the advected air masses were deriv ed from 5-days back-trajectory analyses. Seven tropospheric ozone mini ma were observed at Ny-Alesund in the period from March to June 1994, during which the surface ozone mixing ratios decreased from typical ba ckground concentrations around 40 ppbv to values between 1 ppbv and 17 ppbv (1 ppbv O-3 corresponds to one part of O-3 in 10(9) parts of amb ient air by volume). Four surface ozone minima were detected in August and September 1993 at Neumayer-Station with absolute ozone mixing rat ios between 8 ppbv and 14 ppbv throughout the minima. At both measurin g stations, the ozone minima were detected during polar spring. They c overed periods between 1 and 4 days (Arctic) and 1 and 2 days (Antarct ica), respectively. Furthermore, it was found that in both polar regio ns, the ozone depletion events were confined to the planetary boundary layer with a capping temperature inversion at the upper limit of the ozone poor air mass. Inside this ozone-poor layer, a stable stratifica tion was obvious. Back-trajectory analyses revealed that the ozone-dep leted air masses were transported across the marine, ice-covered regio ns of the central Arctic and the South Atlantic Ocean. These comparabl e observations in both polar regions suggest a similar ozone destructi on mechanism which is responsible for an efficient ozone decay. Nevert heless, distinct differences could be found regarding the vertical str ucture of the ozone depleted layers. In the Arctic, the ozone-poor lay er developed from the surface up to a temperature inversion, whereas i n the Antarctic, elevated ozone-depleted air masses due to the influen ce of catabatic surface winds, were observed.