Abstract
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.
Highlights
The abundance of the heavy oxygen isotopes 17O and 18O in stratospheric O3 is unusually large compared to ambient O2
Laboratory research indicated that the observed isotopic enrichment is primarily controlled by unusually strong isotope effects associated with the O3 formation reaction (Morton et al, 1990): O + O2
There are several processors that retrieve ozone volume mixing ratios (VMRs) from Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) level 1b data; an overview and intercomparison is given by Laeng et al (2015)
Summary
The abundance of the heavy oxygen isotopes 17O and 18O in stratospheric O3 is unusually large compared to ambient O2. Satellite retrievals of δ(a−50O3) and δ(s−50O3) derived from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument on Envisat are presented. The purpose is to investigate whether and how the MIPAS observations can be used to provide independent data on ozone enrichment in the middle and upper stratosphere, and to detect and quantify possible temporal and geographical variations These enrichments are compared to previously published results from the balloon-based thermal emission Fourier transform infrared (FTIR) spectra of Johnson et al (2000), the balloon-based solar FTIR spectra of Haverd et al (2005), the space-based AT-. There are several processors that retrieve ozone volume mixing ratios (VMRs) from MIPAS level 1b data; an overview and intercomparison is given by Laeng et al (2015) These algorithms differ in the microwindows and regularisation technique used, but yield similar results. The latter isotopologue is not examined because its weak spectral lines make it hard to quantify accurately; rather, special attention is given to the enrichment profiles of 50O3 for different latitude bands
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
