Articles | Volume 18, issue 3
Research article
12 Feb 2018
Research article |  | 12 Feb 2018

Atmospheric carbonyl sulfide (OCS) measured remotely by FTIR solar absorption spectrometry

Geoffrey C. Toon, Jean-Francois L. Blavier, and Keeyoon Sung

Abstract. Atmospheric OCS abundances have been retrieved from infrared spectra measured by the Jet Propulsion Laboratory (JPL) MkIV Fourier transform infra-red (FTIR) spectrometer during 24 balloon flights and during nearly 1100 days of ground-based observations since 1985. Our spectral fitting approach uses broad windows to enhance the precision and robustness of the retrievals. Since OCS has a vertical profile similar in shape to that of N2O, and since tropospheric N2O is very stable, we reference the OCS observations to those of N2O, measured simultaneously in the same air mass, to remove the effects of stratospheric transport, allowing a clearer assessment of secular changes in OCS. Balloon measurements reveal less than 5 % change in stratospheric OCS amounts over the past 25 years. Ground-based measurements reveal a springtime peak of tropospheric OCS, followed by a rapid early-summer decrease, similar to the behavior of CO2. This results in a peak-to-peak seasonal cycle of 5–6 % of the total OCS column at northern mid-latitudes. In the long-term tropospheric OCS record, a 5 % decrease is seen from 1990 to 2002, followed by a 5 % increase from 2003 to 2012.

Short summary
OCS is the main form of atmospheric sulfur. It is produced near the earth's surface and destroyed primarily in the stratosphere, where it is converted to stratospheric sulfate aerosol (SSA). SSA plays an important role in atmospheric chemistry and transport and so it is important to better understand the factors that regulate OCS and hence SSA. Ground-based and balloon-borne infrared spectra observed over the past 30 years are analyzed to provide an improved OCS dataset.
Final-revised paper