Speaker
Mr
Carlo Arosio
(Institute of Environmental Physics, University of Bremen)
Description
A continuous monitoring of the stratospheric ozone layer over a global scale is done by means of several techniques. Observations in limb geometry from satellite platforms provide ozone profiles with a good vertical resolution, spatial and temporal coverage.
SCIAMACHY and OMPS-LP are two satellite instruments able to collect shortwave scattered radiance in limb geometry. Ozone profile data sets from SCIAMACHY (2002-2012) and OMPS-LP (2012-2018) were created at the University of Bremen using the same radiative transfer model, spectroscopic databases and a similar retrieval algorithm. The aim of this study is the merging of these data sets, to obtain a consistent time series of ozone global distributions. Since the two missions overlap only for 3 months, a transfer function is needed to overcome issues related to the sensors calibration. To this aim, we chose measurements performed by the MLS instrument as a reference.
Monthly latitude- and longitude-resolved time series of ozone profiles were calculated for the two instruments, exploiting the high spatial resolution of the data sets. Their merging has been then performed minimizing the differences between OMPS-LP and SCIAMACHY ozone number density profiles with respect to MLS values, for each latitude, longitude and altitude independently. The seasonal cycle was not subtracted, because it was found to be consistent enough among the three instruments. Short-term changes in ozone profiles were calculated over 2003-2018 using a multilinear regression (MLR) analysis, including fit proxies as QBO, ENSO and a solar forcing. Positive trends were detected between 35 and 45 km at mid-latitudes, with an increasing ozone concentration up to 2-3% per decade. Negative changes were found in the lower tropical stratosphere but, above 20 km, statistically non-significant. A comparison with short-term trends calculated over the SCIAMACHY time period has been done: while a general agreement is found, some discrepancies are seen in the tropical mid-stratosphere.
A merging with SAGE II ozone profiles was also performed: zonal monthly anomalies from the 3 instruments are merged to study ozone trends over the last 35 years. Applying the same MLR analysis, consistent results with previous studies were found: negative trends before 1997 up to -6% per decade at mid-latitudes around 40 km and the expected recovery after the ozone turn-around point at the end of ‘90, related also to the implementation of the Montreal protocol and its amendments.
Primary author
Mr
Carlo Arosio
(Institute of Environmental Physics, University of Bremen)
Co-authors
Mr
Alexei Rozanov
(Institute of Environmental Physics, University of Bremen, Bremen, Germany)
Prof.
John P. Burrows
(Institute of Environmental Physics, University of Bremen, Bremen, Germany)
Mr
Mark Weber
(Institute of Environmental Physics, University of Bremen, Bremen, Germany)
