HR: 10:50h
AN: A12B-03    [Abstracts]
TI: Simmulations and Inverse Modeling of Global Methyl Chloride
AU: * Yoshida, Y
EM: yyoshida@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Dr., Atlanta, GA 30332-0340 United States
AU: Wang, Y
EM: ywang@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Dr., Atlanta, GA 30332-0340 United States
AU: Zeng, T
EM: tzeng@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Dr., Atlanta, GA 30332-0340 United States
AU: Shim, C
EM: cshim@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Dr., Atlanta, GA 30332-0340 United States
AU: Cunnold, D
EM: cunnold@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311 Ferst Dr., Atlanta, GA 30332-0340 United States
AU: Yantosca, R
EM: bmy@io.harvard.edu
AF: Division of Engineering and Applied Sciences, Harvard University, 29 Oxford St., Cambridge, MA 02138 United States
AU: Blake, D
EM: drblake@uci.edu
AF: Department of Chemistry, University of California, Irvine, 570 Rowland Hall, Irvine, CA 92697-2025 United States
AU: Dutton, G
EM: geoff.dutton@noaa.gov
AF: NOAA/CMDL, 325 Broadway, Boulder, CO 80305 United States
AB: Methyl chloride (CH$_{3}$Cl) is one of the most abundant chlorine-containing gases in the atmosphere and thus, it is a major contributor to stratospheric chlorine. In spite of its important role in atmospheric chemistry, the known sources and sinks of CH$_{3}$Cl are unbalanced. Global simulations of atmospheric CH$_{3}$Cl are conducted using the GEOS-CHEM model. In addition to the known sources (1.5 Tg yr$^{-1}$) from ocean, biomass burning, incineration/industry, salt marshes, and wetlands, a hypothetical aseasonal biogenic source of 2.9 Tg yr$^{-1}$ is added in order to match needed emissions. Observations from 7 surface sites and 8 aircraft field experiments are used to evaluate the model simulations. The model results with a priori emissions and sinks reproduce CH$_{3}$Cl observations at northern mid and high latitudes reasonably well. However, the seasonal variation of CH$_{3}$Cl at southern mid and high latitudes is severely overestimated. Simulated vertical profiles show disagreements in the vicinities of major sources, principally reflecting the uncertainties in the estimated distributions of our added pseudo-biogenic and the biomass burning sources. Inverse modeling is applied to obtain optimal source distributions of CH$_{3}$Cl on the basis of surface and aircraft observations and model results, especially for the biogenic and biomass burning sources. The inversion of the pseudo biogenic CH$_{3}$Cl source is modeled for 4 seasons and 6 geographical regions. The inversion of the biomass burning source is modeled for 4 seasons and two hemispheres. The inversions of the other sources and oceanic and soil uptake are also performed. Model simulations using a posteriori emissions are in better agreement with the observations particularly at the southern high latitudes. The a posteriori source of biomass burning CH$_{3}$Cl is lower by about 27% than the a priori estimate, although there is little change for the biogenic source. The inverse modeling results suggest a clear seasonal pattern of the biogenic source, peaking in spring and fall.
DE: 5405 Atmospheres--composition and chemistry
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting