Atmospheric carbonyl sulfide (OCS) variation from 1992-2004 by ground-based solar FTIR spectrometry

Analysis of ground-based high-resolution solar FTIR absorption spectra from four sites was performed to determine trends and variability in OCS columns over the period 1992–2004. The sites were Wollongong, Australia (34.45° S, 150.88° E), Lauder, New Zealand (45.0° S, 169.7° E), Arrival Heights, Antarctica (77.8° S, 166.6° E) and Mauna Loa, Hawaii (19.5° N, 155.6° W). Small but significant long-term trends of −0.18±0.02% yr-1 above Hawaii, −0.30±0.12% yr-1 above Wollongong and −0.29±0.14% yr-1 above Lauder, were seen. No significant trend was seen above Arrival Heights. A large peak-to-peak seasonal difference observed in 1996–1997 above Wollongong and reported earlier was confirmed, but not repeated in later years. This seasonal feature correlated with particularly high water vapour columns present during late summer and early autumn, and suggests a link to warm oceanic airmasses. Seasonal variation of approximately 6% per year is observed in the total column in other years for all four locations.