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Near global upper tropospheric concentrations of carbon monoxide (CO), ethane (C₂H₆) and ethyne (C₂H₂) from ACE (Atmospheric Chemistry Experiment) Fourier transform spectrometer on board the Canadian satellite SCISAT-1 are presented and compared with the output from the Chemical Transport Model (CTM) GEOS-Chem. The retrievals of ethane and ethyne from ACE have been improved for this paper by using new sets of microwindows compared with those for previous versions of ACE data. With the improved ethyne retrieval we have been able to produce a near global upper tropospheric distribution of C₂H₂ from space. Carbon monoxide, ethane and ethyne concentrations retrieved using ACE spectra show the expected seasonality linked to variations in the anthropogenic emissions and destruction rates as well as seasonal biomass burning activity. The GEOS-Chem model was run using the dicarbonyl chemistry suite, an extended chemical mechanism in which ethyne is treated explicitly. Seasonal cycles observed from satellite data are well reproduced by the model output, however the simulated CO concentrations are found to be systematically biased low over the Northern Hemisphere. An average negative global mean bias of 12% and 7% of the model relative to the satellite observations has been found for CO and C₂H₆ respectively and a positive global mean bias of 1% has been found for C₂H₂. ACE data are compared for validation purposes with MkIV spectrometer data and Global Tropospheric Experiment (GTE) TRACE-A campaign data showing good agreement with all of them

We have shown that the amount fraction of carbon dioxide in a nitrogen or synthetic air matrix stored in cylinders increases as the pressure of the gas mixture reduces, while the amount fraction of methane remains unchanged. Our measurements show the initial amount fraction of carbon dioxide to be lower than the gravimetric value after preparation, which we attribute to the adsorption of a proportion of the molecules to active sites on the internal surface of the cylinder and the valve. As the mixture is consumed, the pressure in the cylinder reduces and the amount fraction of the component is observed to increase. The effect is less pronounced in the presence of water vapor. More dramatic effects have been observed for hydrogen chloride. These findings have significant implications for the preparation of high accuracy gaseous reference materials with unprecedented uncertainties which underpin a broad range of requirements, in particular atmospheric monitoring of high impact greenhouse gases.

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