View
218
Download
2
Tags:
Embed Size (px)
Citation preview
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.
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)
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)
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
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
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
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
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
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
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)
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
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/(m2 yr)
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
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
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
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
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)
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)
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
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.