Analysis of laminated structure in ozone vertical profiles in central Europe

Abstract. Using statistical techniques, we study the relationship between the long-term changes in the laminar structure of the ozone vertical profile at two central-European stations - Hohenpeissenberg and Lindenberg - and other quantities potentially affecting the state of the lower stratosphere, and total-ozone content. We consider only positive laminae greater than 30 nbar. Laminae contribute non-negligibly to total ozone, and this contribution varies strongly with season. The maximum laminae-occurrence frequency in late winter/early spring is five-times higher than the minimum in early autumn. The main result of the paper is the discovery of a strong negative trend in the frequency of laminae occurrence, about –15% per decade, and even a slightly stronger negative trend in ozone content in laminae. Strong negative trends in laminae occurrence imply negative changes in total ozone as well. No pronounced effect of the quasi-biennial oscillation and solar cycle on laminae was found, whereas the 100-hPa temperature had a clear effect, and there was an indication of substantial effects of volcanic eruptions and El Niño southern oscillation events. Long-term changes in individual time series of meteorological parameters measured over Hohenpeissenberg do not indicate their significant role in the observed trend in laminae occurrence. On the other hand, there is some increase in the occurrence of very zonal circulation patterns, as well as slight decrease in very meridional circulation patterns. Together with other indications this allows us to say that dynamical effects are expected to be a principal contributor. Thus changes in laminae occurrence will probably be able to serve as an indicator/tracer of long-term changes in lower-stratospheric dynamics.