Vertical profile of δ<sup>18</sup>OOO from the middle stratosphere to lower mesosphere from SMILES spectra

Abstract

Abstract.Ozone is known to have large oxygen isotopic enrichments of about 10 % in the middle stratosphere; however, there have been no reports of ozone isotopic enrichments above the middle stratosphere. We derived an enrichment δ 18 OOO in the stratosphere and the lower mesosphere from observations of the Superconducting SubmillimeterWave Limb-Emission Sounder (SMILES) onboard the International Space Station (ISS) using a retrieval algorithm optimized for the isotopic ratio. The retrieval algorithm includes (i) an a priori covariance matrix constrained by oxygen isotopic ratios in ozone, (ii) an optimization of spectral windows for ozone isotopomers and isotopologues, and (iii) common tangent height information for all windows. The δ 18 OOO by averaging the SMILES measurements at the latitude range of 20 to 40 • N from February to March in 2010 with solar zenith angle < 80 • was 13 % (at 32 km) with the systematic error of about 5 %. SMILES and past measurements were in good agreement, with δ 18 OOO increasing with altitude between 30 and 40 km. The vertical profile of δ 18 OOO obtained in this study showed an increase and a decrease with altitude in the stratosphere and mesosphere, respectively. The δ 18 OOO peak, 18 %, is found at the stratopause. The δ 18 OOO has a positive correlation with temperature in the range of 220-255 K, indicating that temperature can be a dominant factor to control the vertical profile of δ 18 OOO in the stratosphere and mesosphere. This is the first report of the observation of δ 18 OOO over a wide altitude range extending from the stratosphere to the mesosphere (28-57 km).

Retrievals of heavy ozone with MIPAS

“…Since the discovery over 30 years ago, these findings have been confirmed by further mass spectrometer measurements of atmospheric samples (Krankowsky et al, 2007), and by high-resolution spectroscopy using surface-based total-column measurements (Rinsland et al, 1985;Meier and Notholt, 1996), balloon-borne instruments (Abbas et al, 1987;Goldman et al, 1989;Johnson et al, 2000;Haverd et al, 2005), and space-based spectrometers (Irion et al, 1996;Piccolo et al, 2009;Sato et al, 2014). Laboratory research indicated that the observed isotopic enrichment is primarily controlled by unusually strong isotope effects associated with the O 3 formation reaction (Morton et al, 1990):…”

“…As is the case for total 50 O 3 in the tropical and northern latitude bands, discussed above, the MIPAS global mean δ(a− 50 O 3 ) shows a decrease above 33 km; other datasets also show a decrease with altitude, starting at 40 km for the FTIR dataset of Haverd et al (2005) and the SMILES dataset of Sato et al (2014), or at 30 km for the FIRS-2 dataset of Johnson et al (2000). The ATMOS dataset of Irion et al (1996) shows a steady increase up until the maximum retrieval altitude of 40 km.…”

“…3 for references), which are shown on a 5 km grid, are presented. The SMILES data of Sato et al (2014), which is on its own grid of approximately 5 km vertical resolution, are also shown.…”

“…The most comprehensive datasets, used here for validation of the MIPAS data, are the space-based solar absorption spectra by the ATMOS Fourier transform infrared spectrometer (Irion et al, 1996); the balloon-borne thermal emission spectra by the FIRS-2 Fourier transform spectrometer (Johnson et al, 2000); the balloon-borne solar absorption spectra by the MkIV FTIR spectrometer (Haverd et al, 2005); the mass spectrometer data of Krankowsky et al (2007); and the space-borne emission spectra by the SMILES submillimetre sounder (Sato et al, 2014).…”

“…For validation, 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-MOS solar spectra of Irion et al (1996), and the space-based SMILES thermal emission spectra by Sato et al (2014); the total enrichment of 50 O 3 is compared to the presumably highest precision mass spectrometer data of Krankowsky et al (2007). This paper is structured as follows: the description of the data and the retrieval procedure, including the error analysis, is given in Sect.…”