Optimal estimation of the surface fluxes of chloromethanes using a 3-D global atmospheric chemical transport model

Conference Proceedings Paper
Optimal estimation of the surface fluxes of chloromethanes using a 3-D global atmospheric chemical transport model
Xiao, X., R.G. Prinn, R. Weiss, P. Simmonds and P. Fraser (2007)
Eos Transactions, AGU, 88(52), Fall Meet. Suppl., abstract A11C-0613

Abstract/Summary:

The four chloromethanes - methyl chloride (CH3Cl), dichloromethane (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4) are chlorine-containing gases contributing significantly to stratospheric ozone depletion and/or having adverse health effects. Large uncertainties in estimates of their source and sink magnitudes and temporal and spatial variations currently exist. GEIA inventories and other bottom-up emission results are used to construct a priori maps of surface fluxes of these species. The Model of Atmospheric Transport and CHemistry (MATCH), driven by NCEP interannually varying meteorological fields, is then used to simulate the trace gas mole fractions using the a priori emissions and to quantify the time series for sensitivities of tracer concentrations to different aseasonal, seasonal, and regional sources and sinks. We then implement the Kalman filter (with the unit pulse response method) to estimate time-varying surface fluxes at a monthly resolution for the three short-lived species between 2000-2004, and at a 3-month resolution for CCl4 between 1996-2004. The high frequency observations from AGAGE, SOGE, NIES and NOAA/GMD/ESRL HATS CATS and other low frequency flask observations from NOAA/GMD/ESRL HATS are used to constrain the source and sink magnitudes estimated as multiplying factors for the a priori emissions and contained in the state vector in the Kalman filter. The CH3Cl inversion results indicate large CH3Cl emissions of ~ 2278 Gg/yr from the tropical plants. Relative to their a priori magnitudes, the inversion nearly doubles global fungal emissions, slightly increases emissions from biomass burning and salt marshes, and reduces the global ocean source and soil sink. The inversion also implies greater seasonal oscillations of the natural sources and sink of CH3Cl compared to the a priori. These results and those for the CH2Cl2, CHCl3 and CCl4 inversions will be presented and discussed.

Citation:

Xiao, X., R.G. Prinn, R. Weiss, P. Simmonds and P. Fraser (2007): Optimal estimation of the surface fluxes of chloromethanes using a 3-D global atmospheric chemical transport model. Eos Transactions, AGU, 88(52), Fall Meet. Suppl., abstract A11C-0613 (http://www.agu.org/meetings/fm07/)
  • Conference Proceedings Paper
Optimal estimation of the surface fluxes of chloromethanes using a 3-D global atmospheric chemical transport model

Xiao, X., R.G. Prinn, R. Weiss, P. Simmonds and P. Fraser

AGU, 88(52), Fall Meet. Suppl., abstract A11C-0613

Abstract/Summary: 

The four chloromethanes - methyl chloride (CH3Cl), dichloromethane (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4) are chlorine-containing gases contributing significantly to stratospheric ozone depletion and/or having adverse health effects. Large uncertainties in estimates of their source and sink magnitudes and temporal and spatial variations currently exist. GEIA inventories and other bottom-up emission results are used to construct a priori maps of surface fluxes of these species. The Model of Atmospheric Transport and CHemistry (MATCH), driven by NCEP interannually varying meteorological fields, is then used to simulate the trace gas mole fractions using the a priori emissions and to quantify the time series for sensitivities of tracer concentrations to different aseasonal, seasonal, and regional sources and sinks. We then implement the Kalman filter (with the unit pulse response method) to estimate time-varying surface fluxes at a monthly resolution for the three short-lived species between 2000-2004, and at a 3-month resolution for CCl4 between 1996-2004. The high frequency observations from AGAGE, SOGE, NIES and NOAA/GMD/ESRL HATS CATS and other low frequency flask observations from NOAA/GMD/ESRL HATS are used to constrain the source and sink magnitudes estimated as multiplying factors for the a priori emissions and contained in the state vector in the Kalman filter. The CH3Cl inversion results indicate large CH3Cl emissions of ~ 2278 Gg/yr from the tropical plants. Relative to their a priori magnitudes, the inversion nearly doubles global fungal emissions, slightly increases emissions from biomass burning and salt marshes, and reduces the global ocean source and soil sink. The inversion also implies greater seasonal oscillations of the natural sources and sink of CH3Cl compared to the a priori. These results and those for the CH2Cl2, CHCl3 and CCl4 inversions will be presented and discussed.