Global carbonyl sulfide (OCS) measured by MIPAS/Envisat during 2002–2012

Abstract

<p><strong>Abstract.</strong> We present a global OCS data set covering the period June 2002 to April 2012, derived from FTIR limb emission spectra measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the ENVISAT satellite. The vertical resolution is 4–5 km in the height region 6–15 km and 15 km at 40 km altitude. The total estimated error amounts to 40–50 pptv between 10 and 20 km and to 120 pptv at 40 km altitude. MIPAS OCS data show no systematic bias with respect to balloon observations, with deviations mostly below ±50 pptv. However, they are systematically higher than the OCS volume mixing ratios of the ACE-FTS instrument on SCISAT, with maximum deviations of up to 100 pptv in the altitude region 13–16 km. The data set of MIPAS OCS exhibits only moderate interannual variations and low interhemispheric differences. Average concentrations at 10 km altitude range from 480 pptv at high latitudes to 500–510 pptv in the tropics and at northern mid-latitudes. Seasonal variations at 10 km altitude amount up to 35 pptv in the northern and up to 15 pptv in the southern hemisphere. Northern hemispheric OCS abundances at 10 km altitude peak in June in the tropics and around October at high latitudes, while the respective southern hemispheric maxima were observed in July and in November. Global OCS distributions at 250 hPa (~ 10–11 km) show enhanced values at low latitudes, peaking during boreal summer above the western Pacific and the Indian Ocean, which indicates oceanic release. Further, a region of depleted OCS amounts extending from Brazil to central and southern Africa was detected at this altitude, which is most pronounced in austral summer. This depletion is related to seasonally varying vegetative uptake by the tropical forests. Typical signatures of biomass burning like the southern hemispheric biomass burning plume are not visible in MIPAS data, indicating that this process is only a minor source of tropospheric OCS. At the 150 hPa level (~ 13–14 km) enhanced amounts of OCS were also observed inside the Asian Monsoon Anticyclone, but this enhancement is not especially outstanding as compared to other low latitude regions at the same altitude. At the 80 hPa level (~ 17–18 km) equatorward transport of mid-latitude air masses containing lower OCS amounts around the summertime anticyclones was observed. A significant trend could not be detected in tropospheric MIPAS OCS amounts, which points to globally balanced sources and sinks.</p>

Sampling bias adjustment for sparsely sampled satellite measurements applied to ACE-FTS carbonyl sulfide observations

“…4b again shows how much denser the MIPAS sampling is compared to ACE-FTS. Like Glatthor et al (2017), we also find the ACE-FTS mean value between 60 and 90 • S to be 115 ppt (28 %) lower than the mean value of MIPAS. Therefore, relative rather than absolute mixing ratio differences are used to quantitatively describe the sampling bias in the comparison below.…”

“…1a, so this appears to be an instrumental difference between the MIPAS and ACE-FTS OCS data products. A systematic difference of 75 to 100 ppt lower OCS observed by ACE-FTS compared to MIPAS in the 14 to 20 km altitude region has been noted by Glatthor et al (2017). For the best possible quantitative evaluation, the spatiotemporal box in the ACE-FTS measurements with the lowest ACE-FTS coverage (Fig.…”

“…With a horizontal sampling of about 400 to 500 km along its orbit, MIPAS measured 1000 vertical profiles per day from 2002 to 2004 and 1400 between 2005 and 2012, covering almost all latitudes from 88 • S to 88 • N. This is about 40 times as many profiles as can be provided by ACE-FTS. OCS profiles are retrieved in spectral windows between 839 and 876 cm −1 (Glatthor et al, 2015(Glatthor et al, , 2017. The retrieval uncertainty for a single OCS scan is estimated to be 10 % between 10 and 15 km, 26 % at 20 km and increasing up to 195 % at 40 km altitude (Glatthor et al, 2015).…”

Remotely Sensed Carbonyl Sulfide Constrains Model Estimates of Amazon Primary Productivity

“…Although large‐scale OCS analyses have thus far focused on global or North American domains (Campbell, Berry, et al., 2017; Campbell et al., 2008; Hilton et al., 2017; Parazoo et al., 2021; Wang et al., 2016), recently published satellite retrievals of OCS concentrations provide more detailed spatial coverage that may support a broader range of regional applications (Glatthor et al., 2015, 2017; Kuai et al., 2014, 2015; Vincent & Dudhia, 2017). In particular, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) provides retrievals of OCS mixing ratios in the upper troposphere over both continental and oceanic regions.…”

“…In particular, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) provides retrievals of OCS mixing ratios in the upper troposphere over both continental and oceanic regions. MIPAS is a limb‐sounding instrument operating aboard the Envisat satellite from 2002 to 2012 (Glatthor et al., 2015, 2017). Such measurements are generally too high in altitude to be useful for inferring the land surface plant sink, absent sufficient convective transport (Figure 2).…”