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Impact of Reduced Carbon Oxidation on Atmospheric CO 2 : Implications for Inversions

Impact of Reduced Carbon Oxidation on Atmospheric CO 2 : Implications for Inversions. P. Suntharalingam TransCom Meeting, June 13-16, 2005. N. Krakauer, J. Randerson (CalTech/UCI); D. J. Jacob, J. A. Logan (Harvard); A. Fiore (GFDL/NOAA) The TransCom3 Modelers.

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Impact of Reduced Carbon Oxidation on Atmospheric CO 2 : Implications for Inversions

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  1. Impact of Reduced Carbon Oxidation on Atmospheric CO2 : Implications for Inversions P. Suntharalingam TransCom Meeting, June 13-16, 2005 N. Krakauer, J. Randerson (CalTech/UCI); D. J. Jacob, J. A. Logan (Harvard); A. Fiore (GFDL/NOAA) The TransCom3 Modelers Suntharalingam et al., Global Biogeochemical Cycles, in press.

  2. MOTIVATION • QUESTION : • What is impact of accounting for realistic representation of reduced carbon oxidation • on modeled CO2 distributions • 2) on inverse flux estimates • APPROACH : • 1)Use 3-D atmospheric chemistry model (GEOS-CHEM) to estimate impact on concentrations. (Harvard) • 2) Inverse analysis with MATCH and TransCom3 model basis functions (Caltech/UCI)

  3. Folberth et al. (2005) Suntharalingam et al. Previous Work on this Topic • Enting and Mansbridge (1991) • Enting et al. (1995) • Tans et al. (1995) • Baker (2001)

  4. CARBON FLUX FRAMEWORK UNDERLYING RECENT ATMOSPHERIC CO2 INVERSIONS Atmospheric CO2 Concentration residual ymod - yobs Units = Pg C/yr NET LAND UPTAKE All surface fluxes ?? ( 0-2 ) 90 6 120 92 120 “Residual Biosphere” Land use change, Fires, Regrowth, CO2 Fertilization Fossil Seasonal Biosphere Ocean

  5. REDUCED C OXIDATION PROVIDES TROPOSPHERIC CO2 SOURCE The “Atmospheric Chemical Pump” ATMOSPHERIC CO2 0.9-1.3 Pg C/yr Non- CO pathways (< 6%) Distribution of this CO2 source can be far downstream of C emission location CO NMHCs CH4 Fossil Biomass Burning, Agriculture, Biosphere Ocean

  6. HOW IS REDUCED CARBON ACCOUNTED FOR IN CURRENT INVERSIONS ? A : Emitted as CO2 in surface inventories 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) Seasonal Biosphere : CASA Seasonal biosphere (CASA) : Biospheric C efflux represents respiration (CO2) and emissions of reduced C gases (biogenic hydrocarbons, CH4,etc) (Randerson et al. , 2002; Randerson et al. 1997)

  7. Modeling CO2 release at surface rather than in troposphere leads to systematic error in inversion flux estimates ymodsurf ymod3D VS. yobs Tropospheric CO2 source from reduced C oxidation VS. Surface release of CO2 from reduced C gases CO, CH4, NMHCs Observation network detects tropospheric CO2 source from reduced C oxidation ymod = modeled concentrations

  8. CALCULATION OF CHEMICAL PUMP EFFECT yobs ymodel • Flux Estimate: x = xa+ G (y - Kxa) • STEP 1 : Impact on modeled concentrations • Adjust ymodel to account for redistribution of reduced C from surface inventories to oxidation location in troposphere • Adjustment: D ymodel = y3D –ySURF ADDeffect of CO2 source from tropospheric reduced C oxidation SUBTRACTeffect of reduced C from surface inventories

  9. EVALUATION OF THE CHEMICAL PUMP EFFECTGEOS-CHEM SIMULATIONS (v. 5.07) Standard Simulation CO2 Source from Reduced C 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 Combustion and Biosphere sources CO23DSimulation : y3D CO2SURFSimulation : ySURF Simulations spun up for 3 years. Results from 4th year of simulation

  10. GEOS-CHEM Model http://www-as.harvard.edu/chemistry/trop/geos/index.html • Global 3-D model of atmospheric chemistry (v. 5-07-08) • 2ox2.5o horizontal resolution; 30 vertical levels • Assimilated meteorology (GMAO); GEOS-3 (year 2001) • CO chemistry of Duncan et al. 2005 Reduced Carbon Emissions Distributions (spatial and temporal variability) Fossil : Duncan et al. [2005] (annual mean) Biomass Burning : Duncan et al. [2003] (monthly) Biofuels : Yevich and Logan [2003] NMVOCs : Duncan et al. [2005] ; Guenther et al. [1995]; Jacob et al. [2002] CH4 : A priori distributions from Wang et al. [2004] (monthly)

  11. REDUCED CARBON SOURCES BY SECTORSTANDARD SIMULATION : CO2 Source from Reduced C Oxidation = 1.1 Pg C/yr • Sector breakdown based on Duncan et al. [2005] • *Methane sources distributed according to a priori fields from Wang et al. [2004]

  12. 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]

  13. Source Distributions : Annual Mean CO2COox: Column Integral of CO2 from CO Oxidation CO2RedC :CO2 Emissions from Reduced C Sources gC/(m2 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

  14. MODELED SURFACE CONCENTRATIONS: Annual Mean CO23D CO2SURF Surface concentrations reflect source distributions: Diffuse with tropical maximum for CO23D and localized to regions of high reduced C emissions for CO2SURF

  15. REGIONAL VARIATION OF CHEMICAL PUMP EFFECT Dymodel = CO23D– CO2SURF ppm Largest changes in regions in and downstream of high reduced C emissions TAP : - 0.55; ITN : - 0.35; BAL : - 0.35 (ppm)

  16. ANNUAL MEAN CHEMICAL PUMP EFFECT D ymodel : Zonal average at surface Mean Interhemispheric difference Dy = - 0.21 ppm CO2 (ppm) 0.21 ppm -50 50 Latitude Impact on TransCom3 residuals (Level 1) Systematic decrease in Northern Hemisphere

  17. SEASONALITY OF CONCENTRATION ADJUSTMENT Dy Seasonal variation of interhemispheric Dy: –0.32 ppm (January) -0.15 ppm (July) 0.1 JUL Surface Dy (ppm) -0.1 JAN -0.3 -50 +50 LATITUDE • Greatest seasonal variation in northern mid-latitudes • Smallest impact of chemical pump in N. Hem. summer (shorter CO lifetime)

  18. IMPACT ON SURFACE FLUX ESTIMATESInverse analyses by Nir Krakauer Q :What are the changes in estimates of ‘residual’ fluxes when we account for chemical pump adjustment Dymodel Evaluate impact on TransCom3 Inversions: 1) annual mean(Gurney et al. 2002) 2) seasonal(Gurney et al. 2004) • Estimate effect by modifying concentration error vector as : • (y – (K xa + Dymodel)) • Then, ‘adjusted’ flux estimate is: • xadj = xa + G(y – (K xa + Dymodel)) • Evaluate with 3 transport models (MATCH, GISS-UCI, TM2-LSCE)

  19. 0.22 0.25 0.26 MATCH-CCM TM2-LSCE Original Uptake (a posteriori uncertainty) -2.5 (0.4) -0.9 (0.5) -1.4 (0.5) -19% -9% -27% % Change ANNUAL MEAN INVERSION (Level 1)REDUCTION IN UPTAKE:NORTHERN EXTRA-TROPICAL LANDSystematic Reduction (0.22-0.26 Pg C/year) Pg C/yr • Largest regional impact in Temperate Asia (reductions of 0.1- 0.15 PgC/yr) • Tropical efflux reduced (by 0.14 to 0.19 Pg C/year) • Relative impact varies across models.

  20. Annual Mean Estimates from Cyclostationary Analysis(Level 2)NORTHERN LAND UPTAKE (Pg C/year) GISS-UCI TM2-LSCE MATCH-NCEP Original estimate -0.99 +0.34 -0.06 +0.29 -4.02 +0.27 0.26 -3.80 -0.64 With Chemical pump FLUX ADJUSTMENT (Level 2) 0.35 0.32 0.22 0.26 0.25 Flux adjustment (Level 1) • Bias from seasonal analysis similar to Level 1 analysis (slightly larger) • Bias comparable to a posteriori uncertainty • ‘Between model’ uncertainty is 1.1 PgC/yr from Gurney et al. [2004]

  21. SUMMARY • Neglecting the 3D representation of the CO2 source from reduced C oxidation produces systematic errors in inverse CO2 flux estimates • Accounting for a reduced C oxidation source of 1.1 Pg C/yr gives a reduction in the modeled annual mean N-S CO2 gradient of 0.2 ppm (Regional changes are larger; up to 0.6 ppm in regions of high reduced C emissions) • Inverse estimates of N. extratropical land uptake reduce by about 0.25 Pg C/yr in Level 1 inversions; by up to 0.35 Pg C/yr in Level 2. • We can provide chemical pump concentration adjustments (e.g. at GLOBALVIEW stations) or reduced C source distributions (3D and surface) to calculate the impacts in your own models.

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