Measurements of long-term changes in atmospheric OCS (carbonyl sulfide) from infrared solar observations

Curtis P. Rinsland, Linda Chiou, Emmanuel Mahieu, Rodolphe Zander, Chris D. Boone, Peter F. Bernath

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Multi-decade atmospheric OCS (carbonyl sulfide) infrared measurements have been analyzed with the goal of quantifying long-term changes and evaluating the consistency of the infrared atmospheric OCS remote-sensing measurement record. Solar-viewing grating spectrometer measurements recorded in April 1951 at the jungfraujoch station (46.5 degrees N latitude, 8.0 degrees E longitude, 3.58 km altitude) show evidence for absorption by lines of the strong nu(3) band of OCS at 2062cm(-1). The observation predates the earliest previously reported OCS atmosphere remote-sensing measurement by two decades. More recent infrared ground-based measurements of OCS have been obtained primarily with high-resolution solar-viewing Fourier transform spectrometers (FTSs). Long-term trends derived from this record span more than two decades and show OCS columns that have remained constant or have decreased slightly with time since the Mt. Pinatubo eruption, though retrievals assuming different versions of public spectroscopic databases have been impacted by OCS nu(3) band line intensity differences of similar to 10%. The lower stratospheric OCS trend has been inferred assuming spectroscopic parameters from the high-resolution transmission (HITRAN) 2004 database. Volume mixing ratio (VMR) profiles measured near 30 degrees N latitude with high-resolution solar-viewing FTSs operating in the solar occultation mode over a 22 years time span were combined. Atmospheric Trace MOlecule Spectroscopy (ATMOS) version 3 FTS measurements in 1985 and 1994 were used with Atmospheric Chemistry Experiment (ACE) measurements during 2004-2007. Trends were calculated by referencing the measured OCS VMRs to those of the long-lived constituent N2O to account for variations in the dynamic history of the sampled airmasses. Means and 1-sigma standard deviations of VMRs (in ppbv, or 10(-9) per unit air volume) averaged over 30-100 hPa from measurements at 25-35 degrees N latitude are 0.334 +/- 0.089 ppbv from 1985 (ATMOS Spacelab 3 measurements), 0.297 +/- 0.094 ppbv from 1994 ATLAS 3 measurements, 0.326 +/- 0.074 ppbv from ACE 2004 measurements, 0.305 +/- 0.096 ppbv from ACE 2005 measurements, 0.328 +/- 0.074 from ACE 2006 measurements, and 0.305 +/- 0.090 ppbv from ACE measurements through August 2007. Assuming these parameters, we conclude that there has been no statistically significant trend in lower stratospheric OCS over the measurement time span. We discuss past measurement sets, quantify the impact of changes in infrared spectroscopic parameters on atmospheric retrievals and trend measurements, and discuss OCS spectroscopic uncertainties of the current nu(3) band parameters in public atmospheric databases. (C) 2008 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)2679-2686
Number of pages8
JournalJournal of Quantitative Spectroscopy and Radiative Transfer
Issue number16
Publication statusPublished - Nov 2008


  • Atmospheric carbonyl sulfide
  • Long-term lower stratospheric trend
  • Infrared spectroscopy
  • COS

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