Infra-red remote sensing of organic compounds in the upper troposphere

John J. Remedios, Grant Allen, Alison M. Waterfall

Research output: Contribution to journalConference articlepeer-review

Abstract

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument measures the intensity of atmospheric radiation emitted in the infra-red spectral region at high spectral resolution in five bands ranging from 685 cm-1 to 2410 cm-1. The instrument has an excellent radiometric calibration, allowing the determination of weak features of organic compounds which are present and rather important in the upper troposphere. We have recorded spectral data for peroxyacetyl nitrate (PAN) and acetone in the laboratory with a typical accuracy of better than 10%. These data have allowed us to analyse spectral data from the MIPAS instrument and to detect the spectral signatures of these gases for the first time. For PAN, the detection has been possible in two bands with consistent concentrations giving excellent confidence in the observations. In addition, the signatures of formic acid and ethane have been observed in the MIPAS spectra, although that for ethane is rather better known and not a surprise. The quality of formic acid and ethane retrievals from the MIPAS data will be limited by current uncertainties in the quality of the spectral databases. For PAN, acetone and formic acid, it is shown that the concentrations of these gases can be retrieved both in the Western Mediterranean, a region close to the balloon validation site at Aire-sur-l'adour, and in the polluted region of the East China Sea in April 2003. Typical detection limits for PAN are close to background limits in the Northern hemisphere upper troposphere (60 pptv) whilst those for acetone are somewhat larger and are of the order of 150-250 pptv. Tentatively we assign a detection limit to formic acid of 120 pptv, an estimate limited by uncertainties in spectroscopic data.

Original languageEnglish
JournalEuropean Space Agency. (Special Publication) ESA SP
Issue number628
Publication statusPublished - 1 Jul 2006
Event1st Atmospheric Science Conference - Frascati, Italy
Duration: 8 May 200612 May 2006

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