Very strong negative trends in laminae in ozone profiles

Abstract

A very strong negative trend in the overall ozone content in the positive laminae in ozone profiles, a decrease by 50% during about 20–25 years, was found in the 1970s, 1980s and early 1990s in data of eight Northern Hemisphere ozone sounding stations. They were located at high and middle latitudes in Europe, Canada and Japan. Only the station Wallops Island in US ( 38 ° N ) revealed much smaller reduction of ozone in laminae. This means among others that the negative trend is basically the same for Resolute Bay at 75 ° N and Tateno at 36 ° N in spite of twice as high ozone content in laminae at Resolute Bay. The trends have been broadly studied for large laminae with the peak ozone concentration higher by 40 nbar and more than the background ozone concentration. However, analyses of laminae with the peak ozone concentration higher than 30 or 20 nbar against background for a few stations revealed similar strong negative trends. The trends are almost height independent, but the contribution of laminae to overall ozone content clearly peaks in the lowermost stratosphere. The overall ozone content in laminae has a strong seasonal variation (factor 5 or even more) with a maximum in late winter/early spring, when the negative trend in laminae may be responsible for as much as one third of the observed ozone depletion in European middle latitudes. Laminae seem to contribute substantially to seasonal variation of trends in total ozone.