Drift corrected Odin-OSIRIS ozone product: algorithm and updated stratospheric ozone trends
Abstract. A small long-term drift in the Optical Spectrograph and Infrared Imager
System (OSIRIS) stratospheric ozone product, manifested mostly since 2012, is
quantified and attributed to a changing bias in the limb pointing knowledge
of the instrument. A correction to this pointing drift using a predictable
shape in the measured limb radiance profile is implemented and applied within
the OSIRIS retrieval algorithm. This new data product, version 5.10, displays
substantially better both long- and short-term agreement with Microwave Limb Sounder
(MLS) ozone throughout the stratosphere due to the pointing correction. Previously
reported stratospheric ozone trends over the time period 1984–2013, which
were derived by merging the altitude–number density ozone profile
measurements from the Stratospheric Aerosol and Gas Experiment (SAGE) II
satellite instrument (1984–2005) and from OSIRIS (2002–2013), are
recalculated using the new OSIRIS version 5.10 product and extended to 2017.
These results still show statistically significant positive trends throughout
the upper stratosphere since 1997, but at weaker levels that are more closely
in line with estimates from other data records.