impact of reduced carbon oxidation on atmospheric co 2 : implications for inversions p....
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![Page 1: Impact of Reduced Carbon Oxidation on Atmospheric CO 2 : Implications for Inversions P. Suntharalingam TransCom Meeting, June 13-16, 2005 N. Krakauer,](https://reader035.vdocuments.us/reader035/viewer/2022062516/56649d7b5503460f94a5f40e/html5/thumbnails/1.jpg)
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.
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MOTIVATION
QUESTION :
What is impact of accounting for realistic representation of
reduced carbon oxidation
1) 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)
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Previous Work on this Topic
Enting and Mansbridge (1991)
Enting et al. (1995)
Tans et al. (1995)
Baker (2001)
Suntharalingam et al.Folberth et al. (2005)
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CARBON FLUX FRAMEWORK UNDERLYING RECENT ATMOSPHERIC CO2 INVERSIONS
Fossil Seasonal Biosphere
“Residual Biosphere”
Land use change, Fires, Regrowth, CO2 Fertilization
Ocean
6 120 120
Units = Pg C/yr
Atmospheric CO2
9092
NET LAND UPTAKE
??
( 0-2 )
All surface fluxes
ymod - yobsConcentration residual
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REDUCED C OXIDATION PROVIDES TROPOSPHERIC CO2 SOURCE The “Atmospheric Chemical Pump”
Fossil Biomass Burning, Agriculture, Biosphere Ocean
ATMOSPHERIC CO2
CO
0.9-1.3 Pg C/yr Non- CO pathways
(< 6%)
CH4NMHCs
Distribution of this CO2 source can be far downstream of C
emission location
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HOW IS REDUCED CARBON ACCOUNTED FOR IN CURRENT INVERSIONS ?
A : Emitted as CO2 in surface inventories
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) : Biospheric C efflux represents respiration (CO2) and emissions of reduced C gases (biogenic hydrocarbons, CH4,etc)
(Randerson et al. , 2002; Randerson et al. 1997)
Seasonal Biosphere : CASA
Fossil Fuel
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Modeling CO2 release at surface rather than in troposphere leads to systematic error in inversion flux estimates
Surface release of CO2 from reduced C
gases
Tropospheric CO2 source from reduced C oxidation
CO, CH4, NMHCs
VS.
Observation network detects tropospheric CO2 source from
reduced C oxidation
ymodsurf ymod3D yobs
VS.
ymod = modeled concentrations
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CALCULATION OF CHEMICAL PUMP EFFECT
• Flux Estimate: x = xa + G (y - K xa)
• STEP 1 : Impact on modeled concentrations
Adjust ymodel to account for redistribution of reduced C from surface inventories to oxidation location in troposphere
ymodelyobs
• Adjustmentymodel = y3D – ySURF
ADD effect of CO2 source from tropospheric reduced C
oxidation
SUBTRACT effect of reduced C from surface inventories
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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
CO2SURF Simulation : ySURFCO23D Simulation : y3D
Simulations spun up for 3 years. Results from 4th year of simulation
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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)
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REDUCED CARBON SOURCES BY SECTOR STANDARD 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]
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
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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%
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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/(m2 yr)
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MODELED SURFACE CONCENTRATIONS : Annual Mean
CO2SURFCO23D
Surface concentrations reflect source distributions:
Diffuse with tropical maximum for CO23D and localized to regions of high reduced C emissions for CO2SURF
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Largest changes in regions in and downstream of high reduced C emissions
TAP : - 0.55; ITN : - 0.35; BAL : - 0.35 (ppm)
REGIONAL VARIATION OF CHEMICAL PUMP EFFECT ymodel = CO23D – CO2SURF
ppm
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ymodel : Zonal average
at surface
CO
2 (
pp
m)
ANNUAL MEAN CHEMICAL PUMP EFFECT
Mean Interhemispheric difference
y = - 0.21 ppm
0.21 ppm
Latitude
Impact on TransCom3 residuals (Level 1)
Systematic decrease in Northern Hemisphere
50-50
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SEASONALITY OF CONCENTRATION ADJUSTMENT y
Greatest seasonal variation in northern mid-latitudes
Smallest impact of chemical pump in N. Hem. summer (shorter CO lifetime)
Seasonal variation of interhemispheric y:
–0.32 ppm (January)
-0.15 ppm (July)
LATITUDE
JAN
JUL
Surfa
ce
y (p
pm)
-50 +50
-0.3
-0.1
0.1
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IMPACT ON SURFACE FLUX ESTIMATESInverse analyses by Nir Krakauer
•Estimate effect by modifying concentration error vector as :
(y – (K xa + ymodel))
Then, ‘adjusted’ flux estimate is:
xadj = xa + G(y – (K xa + ymodel))
• Evaluate with 3 transport models (MATCH, GISS-UCI, TM2-LSCE)
Q : What are the changes in estimates of ‘residual’ fluxes when we account for chemical pump adjustment ymodel
Evaluate impact on TransCom3 Inversions:
1) annual mean (Gurney et al. 2002)
2) seasonal (Gurney et al. 2004)
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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.
ANNUAL MEAN INVERSION (Level 1) REDUCTION IN UPTAKE : NORTHERN EXTRA-TROPICAL LAND
Systematic Reduction (0.22-0.26 Pg C/year)
Pg
C/y
r
0.22 0.25 0.26
Original Uptake
(a posteriori uncertainty)
-19%-27%-9% % Change
MATCH-CCM TM2-LSCE
-1.4 (0.5)-2.5 (0.4) -0.9 (0.5)
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Annual Mean Estimates from Cyclostationary Analysis(Level 2)
NORTHERN LAND UPTAKE (Pg C/year)
• 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]
GISS-UCI TM2-LSCE
Original estimate
With Chemical pump
FLUX ADJUSTMENT (Level 2)
-0.99 +0.34 -0.06 +0.29
-0.64 0.26
0.35 0.32
Flux adjustment (Level 1) 0.26 0.25
MATCH-NCEP
-4.02 +0.27
-3.80
0.22
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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.