Evaluation of pollutant outflow and CO sources during TRACE‐P using model‐calculated, aircraft‐based, and Measurements of Pollution in the Troposphere (MOPITT)‐derived CO concentrations

Abstract

Outflow of CO from Asia during March 2001 is evaluated using data from the Transport and Chemical Evolution over the Pacific (TRACE‐P) mission and the Measurements of Pollution in the Troposphere (MOPITT) instrument in conjunction with model‐calculated CO from the University of Maryland chemistry and transport model (UMD CTM). Comparison of model‐calculated CO with aircraft measurements indicates that temporal and spatial variations in CO are well captured by the model (mean correlation coefficient of 0.78); however, model‐calculated mixing ratios are lower than observed especially for pressures >850 hPa where negative biases of ∼60 ppbv were seen. Regression analysis is used to optimize the magnitudes of the bottom‐up TRACE‐P Asian fossil fuel (FF), biofuel (BF), and biomass burning (BB) CO emission inventories. Resulting Asian scaling factors are 1.59 ± 0.34 for FF + BF emissions and 0.47 ± 0.46 for BB emissions. Resulting FF + BF emissions are 27.7 ± 6.1 Tg for March 2001 (301 ± 67 Tg for an entire year). Resulting BB emissions for March 2001 are 8.5 ± 8.3 Tg. These results are consistent with recent inverse modeling studies. Scaling factors are lowest (highest) for experiments that assume a high (low) CO yield for the oxidation of anthropogenic and natural hydrocarbons and for experiments that use (do not use) an aerosol‐modified OH distribution. Comparison of model‐calculated CO with MOPITT measurements supports the results from our regression analysis. Without exception, mean March 2001 model‐calculated CO profiles in the TRACE‐P region from a simulation with adjusted CO sources are within a standard deviation of mean March 2001 MOPITT‐sampled profiles.