Institute of Meteorology and Climate Research

The version 7 of MIPAS ozone record has improved long-term stability

Altitude-latitude cross-section of absolute drifts of MIPAS V5R (left panel) and V7R (middle panel) vs. Aura MLS ozone measurements as well as their difference (right panel). Hatched areas mean that the significance is less than 2σ.

The ESA recently released the new version 7 of Level 1B MIPAS spectra. One of two main improvements of this release is that a full instrument misalignment matrix was implemented in this version, which results in better knowledge of tangent altitudes.
This change, however, is of minor relevance to the IMK/IAA data product because tangent altitudes are retrieved from the spectra (von Clarmann et al., 2003). Another major improvement is the implementation of a new set of time-dependent correction coefficients for the non-linearity in the detector response functions. In the previous version, the correction coefficients were taken from pre-flight studies and were not time dependent, but the instrument is ageing and the detector response function is changing (Eckert et al., 2014). This improvement of the Level 1B spectra is expected to have a major impact on MIPAS Level 2 data, by reducing the instrument drift. We demonstrate this improvement for the MIPAS IMK/IAA ozone dataset. The MIPAS IMK/IAA dataset versions V7H_O3_40 (2002-2004, for the FR period) and V7R_O3_240 (2005- 2012, for the RR period) are part of the new edition of HARMonized dataset of OZone profiles (HARMOZ) database (Sofieva et al., 2013). They are also used in the Long-term Ozone Trends and Uncertainties in the Stratosphere (LOTUS)  SPARC Initiative as a parent dataset for two long-term ozone timeseries: the merged SAGE II/MIPAS/OMPS NASA dataset (Laeng et al., 2018) and the merged SAGE II/CCI/OMPS Sask dataset (Sofieva et al., 2017).

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