During the past several years, several authors have published results of the annual and seasonal trends depicted in the total ozone data from both satellite and ground-based observations. The examination of the vertical profile data available from the balloon ozonesonde and Umkehr observations, however, has been generally restricted to limited periods and to nonseasonal trend calculations. Within this study, we have examined the nonseasonal and the seasonal trend behavior of the ozone profile data from both ozonesonde and Umkehr measurements in a consistent manner, covering the same extended time period, 1968–1991, thus providing the first overall comparison of results. Our results reaffirm the observation of significant negative ozone trends in both the lower stratosphere (15–20 km), about −6% per decade, and upper stratosphere (35–50 km), about −6% per decade, separated by a nodal point in the region of 25–30 km. The upper stratosphere decrease is, apparently, associated with the classic gas phase chemical effect of the chlorofluorocarbons, whereas the cause of the lower stratospheric decline is still under investigation, but may well be associated with the chlorine and bromine chemistry in this region.
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