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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 4 | Copyright
Atmos. Meas. Tech., 10, 1511-1518, 2017
https://doi.org/10.5194/amt-10-1511-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 21 Apr 2017

Research article | 21 Apr 2017

Merged ozone profiles from four MIPAS processors

Alexandra Laeng1, Thomas von Clarmann1, Gabriele Stiller1, Bianca Maria Dinelli2, Anu Dudhia3, Piera Raspollini4, Norbert Glatthor1, Udo Grabowski1, Viktoria Sofieva5, Lucien Froidevaux6, Kaley A. Walker7, and Claus Zehner8 Alexandra Laeng et al.
  • 1Institut für Meteorologie und Klimaforschung, Karlsruhe Institute of Technology, Karlsruhe, Germany
  • 2ISAC-CNR, Bologna, Italy
  • 3Earth Observation Data Group, Oxford University, Oxford, UK
  • 4IFAC-CNR, Florence, Italy
  • 5Finnish Meteorological Institute, Helsinki, Finland
  • 6Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA
  • 7University of Toronto, Toronto, Canada
  • 8ESA ESRIN, Frascati, Italy

Abstract. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) was an infrared (IR) limb emission spectrometer on the Envisat platform. Currently, there are four MIPAS ozone data products, including the operational Level-2 ozone product processed at ESA, with the scientific prototype processor being operated at IFAC Florence, and three independent research products developed by the Istituto di Fisica Applicata Nello Carrara (ISAC-CNR)/University of Bologna, Oxford University, and the Karlsruhe Institute of Technology–Institute of Meteorology and Climate Research/Instituto de Astrofísica de Andalucía (KIT–IMK/IAA). Here we present a dataset of ozone vertical profiles obtained by merging ozone retrievals from four independent Level-2 MIPAS processors. We also discuss the advantages and the shortcomings of this merged product. As the four processors retrieve ozone in different parts of the spectra (microwindows), the source measurements can be considered as nearly independent with respect to measurement noise. Hence, the information content of the merged product is greater and the precision is better than those of any parent (source) dataset.

The merging is performed on a profile per profile basis. Parent ozone profiles are weighted based on the corresponding error covariance matrices; the error correlations between different profile levels are taken into account. The intercorrelations between the processors' errors are evaluated statistically and are used in the merging. The height range of the merged product is 20–55km, and error covariance matrices are provided as diagnostics. Validation of the merged dataset is performed by comparison with ozone profiles from ACE-FTS (Atmospheric Chemistry Experiment–Fourier Transform Spectrometer) and MLS (Microwave Limb Sounder). Even though the merging is not supposed to remove the biases of the parent datasets, around the ozone volume mixing ratio peak the merged product is found to have a smaller (up to 0.1ppmv) bias with respect to ACE-FTS than any of the parent datasets. The bias with respect to MLS is of the order of 0.15ppmv at 20–30km height and up to 0.45ppmv at larger altitudes. The agreement between the merged data MIPAS dataset with ACE-FTS is better than that with MLS. This is, however, the case for all parent processors as well.

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A MIPAS instrument was flown in 2002–2012 on the Envisat satellite and measured atmospheric composition. There exist four processors retrieving atmospheric profiles from MIPAS spectra. We performed a mathematically clean merging of 2007–2008 datasets of ozone from these four processors. The merged product was compared with ozone datasets from ACE-FTS and MLS instruments. The advantages and the shortcomings of this merged product are discussed.
A MIPAS instrument was flown in 2002–2012 on the Envisat satellite and measured atmospheric...
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