Abstract
Abstract. Vertical profiles of the rate of linear change (trend) in the altitude range 15–50 km are determined from decadal O3 time series obtained from SCIAMACHY1/ENVISAT2 measurements in limb-viewing geometry. The trends are calculated by using a multivariate linear regression. Seasonal variations, the quasi-biennial oscillation, signatures of the solar cycle and the El Niño–Southern Oscillation are accounted for in the regression. The time range of trend calculation is August 2002–April 2012. A focus for analysis are the zonal bands of 20° N–20° S (tropics), 60–50° N, and 50–60° S (midlatitudes). In the tropics, positive trends of up to 5% per decade between 20 and 30 km and negative trends of up to 10% per decade between 30 and 38 km are identified. Positive O3 trends of around 5% per decade are found in the upper stratosphere in the tropics and at midlatitudes. Comparisons between SCIAMACHY and EOS MLS3 show reasonable agreement both in the tropics and at midlatitudes for most altitudes. In the tropics, measurements from OSIRIS4/Odin and SHADOZ5 are also analysed. These yield rates of linear change of O3 similar to those from SCIAMACHY. However, the trends from SCIAMACHY near 34 km in the tropics are larger than MLS and OSIRIS by a factor of around two. 1 SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY 2 European environmental research satellite 3 Earth Observing System (EOS) Microwave Limb Sounder (MLS) 4 Optical Spectrograph and InfraRed Imager System 5 Southern Hemisphere ADditional OZonesondes
Highlights
The stratospheric O3 layer shields the Earth from UVB and UVC radiation in the 240–320 nm range
Rates of linear change or trends were determined for stratospheric O3 in the 15–50 km range for the time range August 2002 to April 2012
In the tropics (20◦ N–20◦ S), the O3 trends from SCIAMACHY are found to be positive in the lower stratosphere and negative in the middle stratosphere
Summary
The stratospheric O3 layer shields the Earth from UVB and UVC radiation in the 240–320 nm range. Gebhardt et al.: Stratospheric ozone trends and variability as seen by SCIAMACHY shield (WMO, 2007, 2011) The majority of these trend assessments agreed that the present stage of stratospheric O3 is somewhere between the rate of depletion slowing down and a subsequent turnaround phase, expected as a result of the measures implemented within the Montreal Protocol and its amendments. This manuscript contributes to our knowledge of stratospheric O3 and its changes during the period following the turnaround in stratospheric halogens in the late 1990s, where the halogen load, still high, is slowly declining.
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