Journal cover Journal topic
Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 3.248 IF 3.248
  • IF 5-year value: 3.650 IF 5-year 3.650
  • CiteScore value: 3.37 CiteScore 3.37
  • SNIP value: 1.253 SNIP 1.253
  • SJR value: 1.869 SJR 1.869
  • IPP value: 3.29 IPP 3.29
  • h5-index value: 47 h5-index 47
  • Scimago H index value: 60 Scimago H index 60
Volume 11, issue 8
Atmos. Meas. Tech., 11, 4707-4723, 2018
https://doi.org/10.5194/amt-11-4707-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Atmos. Meas. Tech., 11, 4707-4723, 2018
https://doi.org/10.5194/amt-11-4707-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 13 Aug 2018

Research article | 13 Aug 2018

Differences in ozone retrieval in MIPAS channels A and AB: a spectroscopic issue

Norbert Glatthor1, Thomas von Clarmann1, Gabriele P. Stiller1, Michael Kiefer1, Alexandra Laeng1, Bianca M. Dinelli2, Gerald Wetzel1, and Johannes Orphal1 Norbert Glatthor et al.
  • 1Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
  • 2National Research Council of Italy, Institute of Atmospheric Sciences and Climate, Bologna, Italy

Abstract. Discrepancies in ozone retrievals in MIPAS channels A (685–970cm−1) and AB (1020–1170cm−1) have been a long-standing problem in MIPAS data analysis, amounting to an interchannel bias (AB–A) of up to 8% between ozone volume mixing ratios in the altitude range 30–40km. We discuss various candidate explanations, among them forward model and retrieval algorithm errors, interchannel calibration inconsistencies and spectroscopic data inconsistencies. We show that forward-modelling errors as well as errors in the retrieval algorithm can be ruled out as an explanation because the bias can be reproduced with an entirely independent retrieval algorithm (GEOFIT), relying on a different forward radiative transfer model. Instrumental and calibration issues can also be refuted as an explanation because ozone retrievals based on balloon-borne measurements with a different instrument (MIPAS-B) and an independent level-1 data processing scheme produce a rather similar interchannel bias. Thus, spectroscopic inconsistencies in the MIPAS database used for ozone retrieval are practically the only reason left. To further investigate this issue, we performed retrievals using additional spectroscopic databases. Various versions of the HITRAN database generally produced rather similar channel AB–A differences. Use of a different database, namely GEISA-2015, led to similar results in channel AB, but to even higher ozone volume mixing ratios for channel A retrievals, i.e. to a reversal of the bias. We show that the differences in MIPAS channel A retrievals result from about 13% lower air-broadening coefficients of the strongest lines in the GEISA-2015 database. Since the errors in line intensity of the major lines used in MIPAS channels A and AB are reported to be considerably lower than the observed bias, we posit that a major part of the channel AB–A differences can be attributed to inconsistent air-broadening coefficients as well. To corroborate this assumption we show some clearly inconsistent air-broadening coefficients in the HITRAN-2008 database. The interchannel bias in retrieved ozone amounts can be reduced by increasing the air-broadening coefficients of the lines in MIPAS channel AB in the HITRAN-2008 database by 6%–8%.

Please read the corrigendum first before accessing the article.
Publications Copernicus
Download
Notice on corrigendum

The requested paper has a corresponding corrigendum published. Please read the corrigendum first before downloading the article.

Short summary
We report differences in ozone retrievals in channels A and AB of the space-borne Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), which amount to up to 8 %. We provide strong evidence that the bias is caused by inconsistencies in different spectroscopic databases (MIPAS, HITRAN, GEISA). We show that a major part of the differences can be attributed to inconsistent air-broadening coefficients of the ozone lines contained in the databases.
We report differences in ozone retrievals in channels A and AB of the space-borne Michelson...
Citation
Share