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Xiao, X, Prinn RG, Fraser PJ, Simmonds PG, Weiss RF, O'Doherty S, Miller BR, Salameh PK, Harth CM, Krummel PB, Porter LW, Muhle J, Greally BR, Cunnold D, Wang R, Montzka SA, Elkins JW, Dutton GS, Thompson TM, Butler JH, Hall BD, Reimann S, Vollmer MK, Stordal F, Lunder C, Maione M, Arduini J, Yokouchi Y.  2010.  Optimal estimation of the surface fluxes of methyl chloride using a 3-D global chemical transport model. Atmospheric Chemistry and Physics. 10:5515-5533.   10.5194/acp-10-5515-2010   AbstractWebsite

Methyl chloride (CH(3)Cl) is a chlorine-containing trace gas in the atmosphere contributing significantly to stratospheric ozone depletion. Large uncertainties in estimates of its source and sink magnitudes and temporal and spatial variations currently exist. GEIA inventories and other bottom-up emission estimates are used to construct a priori maps of the surface fluxes of CH(3)Cl. The Model of Atmospheric Transport and Chemistry (MATCH), driven by NCEP interannually varying meteorological data, is then used to simulate CH(3)Cl mole fractions and quantify the time series of sensitivities of the mole fractions at each measurement site to the surface fluxes of various regional and global sources and sinks. We then implement the Kalman filter (with the unit pulse response method) to estimate the surface fluxes on regional/global scales with monthly resolution from January 2000 to December 2004. High frequency observations from the AGAGE, SOGE, NIES, and NOAA/ESRL HATS in situ networks and low frequency observations from the NOAA/ESRL HATS flask network are used to constrain the source and sink magnitudes. The inversion results indicate global total emissions around 4100 +/- 470 Ggyr(-1) with very large emissions of 2200 +/- 390 Gg yr(-1) from tropical plants, which turn out to be the largest single source in the CH(3)Cl budget. Relative to their a priori annual estimates, the inversion increases global annual fungal and tropical emissions, and reduces the global oceanic source. The inversion implies greater seasonal and interannual oscillations of the natural sources and sink of CH(3)Cl compared to the a priori. The inversion also reflects the strong effects of the 2002/2003 globally widespread heat waves and droughts on global emissions from tropical plants, biomass burning and salt marshes, and on the soil sink.

Simmonds, PG, Manning AJ, Cunnold DM, McCulloch A, O'Doherty S, Derwent RG, Krummel PB, Fraser PJ, Dunse B, Porter LW, Wang RHJ, Greally BR, Miller BR, Salameh P, Weiss RF, Prinn RG.  2006.  Global trends, seasonal cycles, and European emissions of dichloromethane, trichloroethene, and tetrachloroethene from the AGAGE observations at Mace Head, Ireland, and Cape Grim, Tasmania. Journal of Geophysical Research-Atmospheres. 111   10.1029/2006jd007082   AbstractWebsite

[1] In situ observations ( every 4 hours) of dichloromethane (CH(2)Cl(2)) from April 1995 to December 2004 and trichloroethene (C(2)HCl(3)) and tetrachloroethene (C(2)Cl(4)) from September 2000 to December 2004 are reported for the Advanced Global Atmospheric Gases Experiment (AGAGE) station at Mace Head, Ireland. At a second AGAGE station at Cape Grim, Tasmania, CH(2)Cl(2) and C(2)Cl(4) data collection commenced in 1998 and 2000, respectively. C(2)HCl(3) is below the limit of detection at Cape Grim except during pollution episodes. At Mace Head CH(2)Cl(2) shows a downward trend from 1995 to 2004 of 0.7 +/- 0.2 ppt yr(-1) ( ppt: expressed as dry mole fractions in 10(12)), although from 1998 to 2004 the decrease has been only 0.3 +/- 0.1ppt yr(-1). Conversely, there has been a small but significant growth of 0.05 +/- 0.01 ppt yr(-1) in CH(2)Cl(2) at Cape Grim. The time series for C(2)HCl(3) and C(2)Cl(4) are relatively short for accurate trend analyses; however, we observe a small but significant decline in C(2)Cl(4) (0.18 +/- 0.05 ppt yr(-1)) at Mace Head. European emissions inferred from AGAGE measurements are compared to recent estimates from industry data and show general agreement for C(2)HCl(3). Emissions estimated from observations are lower than industry emission estimates for C(2)Cl(4) and much lower in the case of CH(2)Cl(2). A study of wildfires in Tasmania, uncontaminated by urban emissions, suggests that the biomass burning source of CH(2)Cl(2) may have been previously overestimated. All three solvents have distinct annual cycles, with the phases and amplitudes reflecting their different chemical reactivity with OH as the primary sink.

O'Doherty, S, Simmonds PG, Cunnold DM, Wang HJ, Sturrock GA, Fraser PJ, Ryall D, Derwent RG, Weiss RF, Salameh P, Miller BR, Prinn RG.  2001.  In situ chloroform measurements at Advanced Global Atmospheric Gases Experiment atmospheric research stations from 1994 to 1998. Journal of Geophysical Research-Atmospheres. 106:20429-20444.   10.1029/2000jd900792   AbstractWebsite

Measurements of atmospheric chloroform (CHCl3) by in situ gas chromatography using electron capture detection are reported from the Advanced Global Atmospheric Gases Experiment (AGAGE) network of atmospheric research stations. They are some of the most comprehensive in situ, high-frequency measurements to be reported for CHCl3 and provide valuable information not only on clean "baseline" mixing ratios but also on local and regional sources. Emissions from these sources cause substantial periodic increases in CHCl3 concentrations above their baseline levels, which can be used to identify source strengths. This is particularly the case for measurements made at Mace Head, Ireland. Furthermore, these local sources of CHCl3 emissions are significant in relation to current estimates of global emissions and illustrate that the understanding of competing sources and sinks of CHCl3 is still fragmentary. These observations also show that CHCl3 has a very pronounced seasonal cycle with a summer minimum and winter maximum presumably resulting from enhanced destruction by OH in the summer. The amplitude of the cycle is dependent on sampling location. Over the 57 months of in situ measurements a global average baseline concentration of 8.9 +/-0.1 ppt was determined with no appreciable trend in the baseline detected.