Long-term Ozone Trend Depicted by Ozonesonde Observations over Japan

The meridional cross section of the long-term ozone losses between the two periods 1968-1975 (pre-ozone hole era) and 1990-2002 (mature ozone hole era) are estimated by using operational ozonesonde observations over Japan. The results are projected on the bins defined by potential temperature (theta) and equivalent latitude (phi(eq)) coordinate system to estimate the midlatitude and polar ozone losses separately. The ozone decrease between the two periods are decomposed of 0.3 ppmv (similar to 5-20%) decline widely distributed in midlatitude stratosphere and 1.0 ppmv (similar to 30-50%) depletion in the focused region defined by 400 <= theta <= 500 K and phi(eq) > 70 degrees N during February-April season. The latter gives an estimate of the enhanced ozone loss in the Northern polar vortex, while the former represents general ozone loss in midlatitude lower stratosphere. Atmospheric circulation changes possibly induced by perturbed ozone are discussed in terms of mean phi(eq).