HR: 1340h
AN: A13A-0084    [Abstracts]
TI: Measurements of N$_{2}$O and SF$_{6}$ for use in Inverse Model Studies
AU: * Dlugokencky, E J
EM: ed.dlugokencky@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Peters, W
EM: wouter.peters@noaa.gov
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Masarie, K A
EM: Kenneth.Masarie@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Lang, P M
EM: Patricia.M.Lang@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Dutton, G
EM: Geoff.Dutton@noaa.gov
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Hall, B D
EM: Bradley.Hall@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AB: NOAA CMDL makes measurements of atmospheric nitrous oxide (N$_{2}$O) and sulfur hexafluoride (SF$_{6}$) mole fractions in discrete air samples from $\sim$60 surface sites and $\sim$10 vertical profile sites for use in inverse modeling. Measurements are made by gas chromatography with electron capture detection (ECD) relative to standard scales developed in CMDL's Halocarbons and Other Atmospheric Trace Species (HATS) group. Uncertainties in the standard scales (95% confidence limits) are 0.8 nmol mol$^{-1}$ for N$_{2}$O and 0.05 pmol mol$^{-1}$ for SF$_{6}$. For N$_{2}$O, the ECD response is characterized monthly by a second-order polynomial with a suite of 6 secondary standards covering the range 242-343 nmol mol$^{-1}$. An instrument response function prepared from measurements of the secondary standards relative to a reference cylinder is used to quantify samples. SF$_{6}$ in air samples is quantified with the reference by assuming a linear response with zero intercept in samples that are free of SF$_{6}$. Reproducibility of the measurements, based on agreement between two samples collected in series, is $\sim$0.4 nmol mol$^{-1}$ for N$_{2}$O and $\sim$0.04 pmol mol$^{-1}$ for SF$_{6}$. So far, all measurements have been made on a single analytical system. The measurements impose important constraints on the budgets of N$_{2}$O and SF$_{6}$ based on observed trends, changes in trends, and spatial gradients. These parameters can be used to determine source/sink imbalances, changes in emission rates over time, and the distribution of emissions. In addition, Peters et al. [JGR, in press, 2004] have used the SF$_{6}$ measurements to evaluate transport in the two-way nested chemistry transport model, TM5. They found that TM5 captures vertical gradients and synoptic variability in SF$_{6}$ well at both MBL and continental sampling sites, but it over-estimates the meridional gradient by $\sim$19%. The SF$_{6}$ data also suggest that global SF$_{6}$ emissions increased by $\sim$20% during late-2002.
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting