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

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

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

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

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

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

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)

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

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

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

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

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

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

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

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

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