Trends in the ozone vertical distribution from the Umkehr observations at Belsk 1963–2007

Abstract

The Umkehr observations at Belsk (52° N, 21° E) are homogenized for the period 1963 to 2007, taking into account step changes in the R–N tables and re-evaluated total ozone values. Ozone content in the Umkehr layers is calculated by the newest retrieval (UMK04). Trends in the ozone content in the Umkehr layers are calculated in time series with the natural ozone fluctuations due to the 11 year solar activity and quasi-biennial oscillations removed. The negative trend in total ozone (∼3.5% per decade), found for the period 1980 to 1995, is due to the ozone depletion in the lower and mid-stratosphere (up to 23.5 km). Afterwards, the trends in total ozone and in lower and mid-stratospheric ozone are not statistically significant. In the upper stratosphere (> 37 km) the trends in the period 1996 to 2007 are positive and of ∼3–5% per decade. The occurrence of the positive trend after 1995 is in line with the Montreal Protocol regulations on ozone-depleting substances.