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[1] Measurements of carbonyl sulfide (COS) from a global air-monitoring network over multiple years suggest that atmospheric mixing ratios of COS are strongly influenced by terrestrial vegetation in the Northern Hemisphere (NH) and by the oceans in the Southern Hemisphere (SH). The annual mean NH mixing ratio estimated from results at seven surface sites during 2000.2-2005.2 was 476 ± 4 ppt, or slightly less than the mean of 491 ± 2 ppt derived from results at three surface sites in the SH. The lowest annual mean mixing ratios were measured at low-altitude continental sites in the midlatitude and high-latitude NH. Mixing ratios undergo substantial seasonal variations at nearly all sites across the globe; the largest seasonal variations are observed at the NH sites having the lowest annual means. There is little coherence in the seasonality in the NH and SH, suggesting that the COS seasonality is driven by different processes in each hemisphere. These seasonal changes cause the NH/SH ratio, as estimated from the available surface data, to vary regularly from 0.91 ± 0.01 to 1.04 ± 0.02 across a year; the annual mean NH/SH ratio was 0.97 ± 0.01. Results from over 160 aircraft profiles regularly collected at eight sites over the continental United States throughout an entire year reveal substantial vertical gradients for COS mixing ratios that vary with season. While similar mixing ratios are observed throughout the NH troposphere during January-April (up to 8 km above sea level (asl)), during the growing season substantially reduced mixing ratios are observed in the boundary layer above the continental United States (defined here as <2 km asl). The surface and aircraft results for COS show strong similarities to atmospheric CO 2 , though both the amplitude of seasonal variations measured at Earth's surface and the observed vertical gradients during the growing season are 5-6 times larger for COS than for CO 2 on a relative basis. A qualitative analysis of the results in light of known sources and sinks suggests (1) that terrestrial uptake, most likely due to photosynthetically active vegetation, dominates the seasonality observed throughout the Northern Hemisphere at a rate that is about 5 times greater than estimates based upon scaling net primary production by mean, ambient air mixing ratios of COS to CO 2 , (2) the oceans dominate the seasonality observed in the Southern Hemisphere, and (3) biomass burning has a small influence on the seasonality observed for COS in the extratropics of both hemispheres.Citation: Montzka, S. A., P. Calvert, B. D. Hall, J. W. Elkins, T. J. Conway, P. P. Tans, and C. Sweeney (2007), On the global distribution, seasonality, and budget of atmospheric carbonyl sulfide (COS) and some similarities to CO 2 ,

The multispecies analysis of daily air samples collected at the NOAA Boulder Atmospheric Observatory (BAO) in Weld County in northeastern Colorado since 2007 shows highly correlated alkane enhancements caused by a regionally distributed mix of sources in the Denver‐Julesburg Basin. To further characterize the emissions of methane and non‐methane hydrocarbons (propane, n‐butane, i‐pentane, n‐pentane and benzene) around BAO, a pilot study involving automobile‐based surveys was carried out during the summer of 2008. A mix of venting emissions (leaks) of raw natural gas and flashing emissions from condensate storage tanks can explain the alkane ratios we observe in air masses impacted by oil and gas operations in northeastern Colorado. Using the WRAP Phase III inventory of total volatile organic compound (VOC) emissions from oil and gas exploration, production and processing, together with flashing and venting emission speciation profiles provided by State agencies or the oil and gas industry, we derive a range of bottom‐up speciated emissions for Weld County in 2008. We use the observed ambient molar ratios and flashing and venting emissions data to calculate top‐down scenarios for the amount of natural gas leaked to the atmosphere and the associated methane and non‐methane emissions. Our analysis suggests that the emissions of the species we measured are most likely underestimated in current inventories and that the uncertainties attached to these estimates can be as high as a factor of two.

The oxidizing capacity of the global atmosphere is largely determined by hydroxyl (OH) radicals and is diagnosed by analyzing methyl chloroform (CH(3)CCl(3)) measurements. Previously, large year-to-year changes in global mean OH concentrations have been inferred from such measurements, suggesting that the atmospheric oxidizing capacity is sensitive to perturbations by widespread air pollution and natural influences. We show how the interannual variability in OH has been more precisely estimated from CH(3)CCl(3) measurements since 1998, when atmospheric gradients of CH(3)CCl(3) had diminished as a result of the Montreal Protocol. We infer a small interannual OH variability as a result, indicating that global OH is generally well buffered against perturbations. This small variability is consistent with measurements of methane and other trace gases oxidized primarily by OH, as well as global photochemical model calculations.