1. Constraints on Asian Carbon Fluxes using TRACE-P CO2/CO Correlations
P. Suntharalingam, D. Jacob, P. Palmer, Y. Xiao, R. Yantosca, D. Streets, S. Vay, G. Sachse and C. Harward

2. MOTIVATION To identify contraints on Asian CO2 sources through analysis of observed correlations between CO2 and CO
CO2/CO correlations from TRACE-P flights display a range of distinct values

3. APPROACH Analysis of CO2/CO correlations in TRACE-P data
Combination of GEOS-CHEM simulations for CO2 and CO to develop a set of modeled CO2/CO correlations
Comparison of modeled correlations with observations allows evaluation of imposed CO2/CO emissions ratios in model

4. Model Emissions Inventories used in TRACE-P Analysis
Averaged over TRACE-P period
Averaged over TRACE-P period
SOURCE
CO2 CO
Fossil fuel
Asian : Streets et al. 2002
Global : Marland et al. 2001
Global :Logan et al.
Biomass burning
Asian : Heald et al. 2002
Global : Yevich and Logan 2002
Biofuels
Global : Yevich and Logan, 2002
Seasonal biosphere
CASA ecosystem model
Potter et al. 1993

5. Regional CO2/CO Emissions Ratios in Model
Regional CO2/CO signatures display a range of values reflecting the respective mix of source types

6. DC8 Flight 16 : Yokota Local 4
Measurements on this flight display distinct CO2/CO correlations

7. DC8 Flight 16 : Yokota Local 4
Ascent out of Japan (slope = 65)
Boundary layer measurements off China (slope = 12)
Measurements above 500 mb (slope = 60)

8. Regional Analysis of TRACE-P Measurements
To compare ensemble of TRACE-P measurements to model simulations :
a) define flight regions
b) Calculate regional mean CO2/CO ratio relative to background

9. CO2/CO Ratios for selected TRACE-P Flight Regions
Mean CO2/CO Ratio (s.d)
(mol/mol)
Region1 : Off-shore China
( > 850 mb)
25.1 (15.3)
Region 2 : Over Japan
(> 850 mb)
45.6 (24.8)
All TRACE-P flights
40.9 (17.5)
Mean CO2/CO ratios show an 80% difference between regions

10. GEOS-CHEM Simulations for TRACE-P
3-D Transport Model : GEOS-CHEM
Resolution : (2o x 2.5o), 48 vertical levels
CO2 simulation : Inventories detailed previously
CO simulation : Palmer et al., 2002
A posteriori CO distribution derived from inversion of TRACE-P CO measurements

11. Analysis of Region 1: Flights off China
Mean CO2/CO = 25.1
Mean CO2/CO = 44.9
Discrepancies between modeled and observed CO2/CO ratios are due to overestimates of simulated CO2 and underestimates of simulated CO in the boundary layer

12. Regional Mean CO2/CO Ratios Comparison of GEOS-CHEM Model with TRACE-P Data
FLIGHT REGION
TRACE-P Data
GEOS-CHEM Model
% Difference
Offshore-China
( > 850 mb)
25.1 (15.3)
44.9 (18.2)
78 %
Over Japan
45.6 (24.8)
56.7 (20.5)
24 %
All Data (> 850 mb)
40.0 (17.5)
53.9 (13.6)
34 %
Greatest discrepancy
Modeled CO2/CO ratios higher than for the TRACE-P measurements. Most marked difference in Region1 off China

13. Which Emissions Source is too High ?
Region1 : Offshore China
TRACE-P Observations
GEOS-CHEM Model
Mean ratio = 25.1
Mean ratio = 44.9 CO
Modeled CO2/CO ratios higher than observations
Modeled boundary layer CO2 is higher and CO is lower than observations
Reconciliation of modeled CO2 with observed CO2 and CO2/CO ratios requires a reduction in a source with a high CO2/CO emissions ratio
CO2
OBSERVATIONS
MODEL

14. Impact on Modeled CO2/CO Ratio of Reducing an Emissions Source
Reduce SOURCE 1 which has a low CO2/CO ratio
Reduce SOURCE 2 which has a high CO2/CO ratio
Original model ratio
New ratio
SOURCE 2
Original model ratio
SOURCE 2
New ratio
CO2
CO2
SOURCE 1
SOURCE 1 CO CO
New model ratio is higher than before
New model ratio is lower than before

15. Scenarios of CO2 Source Emissions Reductions
Region1 : Offshore China
Mean CO2/CO(mol/mol)
OBSERVATIONS
24.4
Original Model
44.9
Reduce biospheric CO2 by 30%
35.1
Reduce fossil emissions by 30%
55.4
Reduce biomass burning by 30%
45.5
Mean CO2 vs Altitude
Original Model
A reduction in modeled biospheric CO2 emissions yields a closer match with CO2 and CO2/CO measurements
Observations
Model: Reduced biospheric emissions

16. Conclusions
Observed CO2/CO correlations from the TRACE-P flight data display distinct correlations reflecting regional signatures
Modeled correlations, analyzed on a regional basis, are consistently higher than in the observations; these differences can be ascribed to discrepancies in GEOS-CHEM simulations of both CO2 and CO
A reduction in Asian biospheric CO2 emissions yields a closer match with observed CO2 and CO2/CO values
A systematic evaluation of carbon fluxes using observed CO2/CO correlations will be analyzed in a formal inversion