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Evaluating the Role of the CO 2 Source from CO Oxidation

Evaluating the Role of the CO 2 Source from CO Oxidation. P. Suntharalingam Harvard University TRANSCOM Meeting, Tsukuba June 14-18, 2004. Collaborators : J. Randerson, J. A. Logan, D. J. Jacob, N. Krakauer, Y. Xiao, R. M. Yantosca,.

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Evaluating the Role of the CO 2 Source from CO Oxidation

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  1. Evaluating the Role of the CO2 Source from CO Oxidation P. Suntharalingam Harvard University TRANSCOM Meeting, Tsukuba June 14-18, 2004 Collaborators : J. Randerson, J. A. Logan, D. J. Jacob, N. Krakauer, Y. Xiao, R. M. Yantosca, Acknowledgements : NOAA OGP Global Carbon Cycle Program, NASA Carbon Cycle Program

  2. CARBON FLUX FRAMEWORK UNDERLYING MANY ATMOSPHERIC CO2 INVERSIONS Atmospheric CO2 Units = Pg C/yr 90 6 92 120 120 1.6 0.5 Fossil Biosphere Land use Change Ocean

  3. TROPOSPHERIC CO OXIDATION IS A SOURCE OF ATMOSPHERIC CO2 ATMOSPHERIC CO2 0.9-1.2 Pg C/yr ATMOSPHERIC CO CO, CH4, NMHCs Fossil Biosphere, Land use change, Agriculture, Biomass burning Ocean

  4. REDUCED CARBON GASES ARE ACCOUNTED FOR IN EMISSIONS INVENTORIES BUT EMITTED AS CO2 Fossil Fuel Fossil fuel : CO2 emissions based on carbon content of fuel and assuming complete oxidation of CO and volatile hydrocarbons. (Marland and Rotty, 1984; Andres et al. 1996) CASA Neutral Biosphere CASA neutral biosphere : Biospheric C efflux represents respiration (CO2) and emissions of reduced C gases (biogenic hydrocarbons, CH4,etc) (Randerson et al. , 2002; Randerson et al. 1997)

  5. ANALYSIS FOCUS: Evaluating the “Chemical Pump” Effect IMPLICATIONS FOR FLUX ESTIMATES FROM CO2 INVERSIONS OF MODELING REDUCED C CONTRIBUTION TO CO2AT SURFACE RATHER THAN AT OXIDATION SITE IN TROPOSPHERE CO2 from reduced C gases CO2 source from CO oxidation VS. Tropospheric Source Surface Source STEP 1 : Evaluate impact on modeled concentrations STEP 2 : Implications for atmospheric inversions and estimated fluxes Previous related analyses : Enting and Mansbridge [1991]; Baker [2001]

  6. EVALUATION OF THE CHEMICAL PUMP EFFECTCalculate ADJUSTMENT D zmodel to Model Concentrations • Flux estimates from atmospheric inversions are based on difference between modeled and observed CO2 concentrations : zmodel– zobs • Adjust zmodel to account for redistribution of reduced gas C from surface inventories to oxidation location in troposphere • AdjustmentD zmodel = zCOox –zRedC ADDeffect of CO oxidation source of CO2 SUBTRACTeffect of reduced C from surface inventories Total carbon source conserved between zCOox and zRedC simulations

  7. EVALUATION OF THE CHEMICAL PUMP EFFECTANALYSIS SETUP USING THE GEOS-CHEM MODEL Standard Simulation CO2 Source from CO Oxidation = 1.1 Pg C/yr Distribute source according to seasonal 3-D variation of CO2 production from CO Oxidation Distribute source according to seasonal SURFACE variations of reduced C emissions from Fossil and Biosphere sources CO2COoxSimulation CO2RedCSimulation Simulations spun up for 3 years. Results from 4th year of simulation

  8. The GEOS-CHEM Modelhttp://www-as.harvard.edu/chemistry/trop/geos/index.html • Global 3-D model of atmospheric chemistry • 2ox2.5o horizontal resolution; 30 vertical levels • Driven by assimilated meteorology (GMAO) • The CO simulation run to obtain CO oxidation distribution relies on archived OH fields (monthly) Emissions Distributions (spatial and temporal variability) Fossil : Andres et al. [1996] (annual mean) Biomass Burning : Duncan et al. [2003] (monthly) Biofuels : Yevich and Logan [2003] (annual mean) Biogenic hydrocarbons : Duncan et al. [2004], based on Guenther et al. [1995] (monthly) CH4 emissions distributions : A priori from Wang et al. [2004] (monthly)

  9. GLOBAL CO BUDGET SINKS : Oxidation by OH STANDARD SIMULATION :CO2 source from CO oxidation of 1.1 Pg C/yr

  10. REDUCED CARBON SOURCES BY SECTORSTANDARD SIMULATION : CO2 Source from CO Oxidation = 1.1 Pg C/yr * Methane sources distributed according to a priori fields from Wang et al. [2004]

  11. CH4 EMISSIONS AND BUDGET PROPORTIONS Standard Simulation:CH4 Oxidation to CO = 0.39 Pg C/yr Biofuel 2% Landfills 10% Rice 11% Fossil 16% Livestock 11% Biomass Burning 4% Termites 5% Wetlands 36% CH4 emissions distributions and budget proportions from the a priori distribution of Wang et al. [2004]

  12. Source Distributions : Annual Mean CO2COox: Column Integral of CO2 from CO Oxidation CO2RedC :CO2 Emissions from Reduced C Sources gC/(cm2 yr) Zonal Integral of Emissions CO2COox :Maximum in tropics, diffuse CO2RedC : Localized, corresponding to regions of high CO, CH4 and biogenic NMHC emissions CO2COox CO2RedC Latitude

  13. SURFACE CONCENTRATIONS: Annual Mean CO2RedC CO2COox DDmodelCO2 Chemical Pump Adjustment

  14. D DmodelCO2 at Surface CO2 (ppm) ZONAL AVERAGE : CHEMICAL PUMP EFFECT Mean Interhemispheric difference = - 0.21 ppm 0.21 ppm Fossil : Surface, annual mean Latitude 1 Pg Fossil fuel CO2 source gives interhemispheric difference of 0.81 ppm at surface, in GEOS-CHEM model 0.8 ppm

  15. CHEMICAL PUMP EFFECT AT GLOBALVIEW SITES USED IN TRANSCOM LEVEL 1 INVERSION Mean interhemispheric difference at TRANSCOM sites = 0.2 ppm TRANSCOM Level 1 Inversion residuals from Gurney et al. 2002

  16. REGIONAL VARIATION OF CHEMICAL PUMP EFFECT Largest changes in regions in and downstream of high reduced C emissions TAP : - 0.55; ITN : - 0.35; BAL : - 0.35 (ppm)

  17. IMPACT ON SURFACE FLUX ESTIMATES Preliminary inversion results from J. Randerson, N. Krakauer TRANSCOM Level 1 inversion MATCH model

  18. SUMMARY • The atmospheric chemical pump has important implications for modeled CO2 concentrations and inversion flux estimates. • A CO oxidation source of 1.1 Pg C/yr gives a reduction in the modeled annual mean N-S gradient of 0.2 ppm (equivalent to a reduction of 0.2 Pg C/yr in Northern Hemispheric land uptake in an annual mean inversion.) • Regional changes are larger; up to 0.6 ppm in regions of high reduced C emissions. • Seasonal variations and sensitivities to model assumptions will be explored in future work. • We can provide the reduced C source distributions (3D and surface) to TRANSCOM modelers to calculate their own model-specific chemical pump adjustments.

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