1Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, the Netherlands
2Karlsruher Institut für Technologie, Institut für Meteorologie und Klimaforschung, Karlsruhe, Germany
3LERMA-IPSL, Sorbonne Universités, UPMC Univ. Paris 6, Observatoire de Paris, PSL Research University, CNRS, Paris, France
Received: 25 Apr 2016 – Discussion started: 14 Jun 2016
Abstract. A method for retrieval of 18O-substituted isotopomers of O3 in the stratosphere with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is presented. Using a smoothing regularisation constraint, volume mixing ratio profiles are retrieved for the main isotopologue and the symmetric and asymmetric isotopomers of singly substituted O3. For the retrieval of the heavy isotopologues, two microwindows in the MIPAS A band (685–970 cm−1) and six in the AB band (1020–1170 cm−1) are used. As the retrievals are performed as perturbations on the previously retrieved a priori profiles, the vertical resolution of the individual isotopomer profiles is very similar, which is important when calculating the ratio between two isotopomers. The performance of the method is evaluated using 1044 vertical profiles recorded with MIPAS on 1 July 2003. The mean values are separated by latitude bands, along with estimates of their uncertainties. The asymmetric isotopomer shows a mean enrichment of ∼ 8 %, with a vertical profile that increases up to 33 km and decreases at higher altitudes. This decrease with altitude is a robust result that does not depend on retrieval settings, and it has not been reported clearly in previously published datasets. The symmetric isotopomer is considerably less enriched, with mean values around 3 % and with a large spread. In individual retrievals the uncertainty of the enrichment is dominated by the measurement noise (2–4 %), which can be reduced by averaging multiple retrievals; systematic uncertainties linked to the retrieval are generally small at ∼ 0.5 %, but this is likely underestimated because the uncertainties in key spectroscopic parameters are unknown. The variabilities in the retrieval results are largest for the Southern Hemisphere.
Revised: 25 Aug 2016 – Accepted: 31 Aug 2016 – Published: 15 Dec 2016
Jonkheid, B., Röckmann, T., Glatthor, N., Janssen, C., Stiller, G., and von Clarmann, T.: Retrievals of heavy ozone with MIPAS, Atmos. Meas. Tech., 9, 6069-6079, doi:10.5194/amt-9-6069-2016, 2016.