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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
CARBON FLUX FRAMEWORK UNDERLYING MANY ATMOSPHERIC CO2 INVERSIONS
Fossil Biosphere Land use Change
Ocean
1.6 0.5
6120 120
Units = Pg C/yr
Atmospheric CO2
9092
TROPOSPHERIC CO OXIDATION IS A SOURCE OF ATMOSPHERIC CO2
Fossil Biosphere, Land use change, Agriculture, Biomass burning
Ocean
ATMOSPHERIC CO2
ATMOSPHERIC CO
CO, CH4, NMHCs
0.9-1.2 Pg C/yr
REDUCED CARBON GASES ARE ACCOUNTED FOR IN EMISSIONS INVENTORIES BUT EMITTED AS CO2
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 : Biospheric C efflux represents respiration (CO2) and emissions of reduced C gases (biogenic hydrocarbons, CH4,etc)
(Randerson et al. , 2002; Randerson et al. 1997)
CASA Neutral Biosphere
Fossil Fuel
ANALYSIS FOCUS: Evaluating the “Chemical Pump” Effect IMPLICATIONS FOR FLUX ESTIMATES FROM CO2 INVERSIONS OF MODELING
REDUCED C CONTRIBUTION TO CO2 AT SURFACE RATHER THAN AT OXIDATION SITE IN TROPOSPHERE
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]
CO2 from reduced C gases
VS.CO2 source from CO oxidation
Surface Source Tropospheric Source
EVALUATION OF THE CHEMICAL PUMP EFFECTCalculate ADJUSTMENT zmodel to Model Concentrations
1) Flux estimates from atmospheric inversions are based on difference between modeled and observed CO2 concentrations : zmodel – zobs
2) Adjust zmodel to account for redistribution of reduced gas C from surface inventories to oxidation location in troposphere
3) Adjustmentzmodel = zCOox – zRedC
ADD effect of CO oxidation source of CO2
SUBTRACT effect of reduced C from surface inventories
Total carbon source conserved between zCOox and zRedC
simulations
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
CO2RedC SimulationCO2COox Simulation
Simulations spun up for 3 years. Results from 4th year of simulation
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)
GLOBAL CO BUDGETSOURCES Duncan et al. 2004
Tg CO Pg CRecent Inverse
Analyses*
COMBUSTIONFossilBiomass BurningBiofuelsTOTAL
465-490450-570
190 1105-1250 0.47 –0.55
* Bergamaschi et al. [2000]; Petron et al. [2002]; Kasibhatla et al. [2002]
1100-1530 0.47-0.65
BIOGENICSIsoprene, Monoterpenes, etc.
350-370 0.15-0.16 510-660 0.22-0.28
CH4 OXIDATION 840-915 0.36-0.39 740-830 0.32-0.35
TOTAL 2290-2540 0.9-1.1 2846-3067 1.2-1.3
SINKS : Oxidation by OH
STANDARD SIMULATION :CO2 source from CO oxidation of 1.1 Pg C/yr
REDUCED CARBON SOURCES BY SECTOR STANDARD SIMULATION : CO2 Source from CO Oxidation = 1.1 Pg C/yr
* Methane sources distributed according to a priori fields from Wang et al. [2004]
REDUCED CARBON SOURCES Pg C/yr
Fossil (CO,CH4,NMHCs) 0.27
Biomass Burning (CO,CH4,NMHCs) 0.26
Biofuels (CO,CH4) 0.09
Biogenic Hydrocarbons 0.16
Other Methane Sources* 0.31
TOTAL 1.1
CH4 EMISSIONS AND BUDGET PROPORTIONS
Rice
Livestock
Wetlands
Termites
BiomassBurn
Fossil
Landfills
Biofuel
Standard Simulation :CH4 Oxidation to CO = 0.39 Pg C/yr
CH4 emissions distributions and budget proportions from the a priori distribution of Wang et al. [2004]
Rice 11%
Wetlands 36%
Termites 5%
Biomass Burning 4%
Fossil 16%
Landfills 10%Biofuel 2%
Livestock 11%
Source Distributions : Annual Mean
Zonal Integral of Emissions
Latitude
CO2COox: Column Integral of
CO2 from CO OxidationCO2RedC :CO2 Emissions from
Reduced C Sources
CO2COox :Maximum in tropics, diffuse
CO2RedC : Localized, corresponding to regions of high CO, CH4 and biogenic NMHC emissions
CO2COox
CO2RedC
gC/(cm2 yr)
ZONAL AVERAGE : CHEMICAL PUMP EFFECT
DmodelCO2 at
Surface
CO
2 (p
pm
)
Mean Interhemispheric
difference = - 0.21 ppm
0.8 ppm
Fossil : Surface, annual mean
1 Pg Fossil fuel CO2 source gives interhemispheric difference of 0.81 ppm at surface, in GEOS-CHEM model
0.21 ppm
Latitude
CHEMICAL PUMP EFFECT AT GLOBALVIEW SITES USED IN TRANSCOM LEVEL 1 INVERSION
TRANSCOM Level 1 Inversion residuals from Gurney et al. 2002
Mean interhemispheric difference at TRANSCOM sites = 0.2 ppm
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)
IMPACT ON SURFACE FLUX ESTIMATES
INTERHEMISPHERIC DIFFERENCE AT
GLOBALVIEW SITES (ppm)
DECREASE IN NHEM LAND CO2
UPTAKE(Pg C/yr)
Standard Simulation - 0.2 0.2
High CO (Petron et al. 2002)Increased Fossil+Biofuel emissions of 0.12 Pg C/yr
- 0.27 0.3
Preliminary inversion results from J. Randerson, N. Krakauer
TRANSCOM Level 1 inversion MATCH model
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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