Influence of regional‐scale anthropogenic emissions on CO₂ distributions over the western North Pacific

We report here airborne measurements of atmospheric CO 2 over the western North Pacific during the March–April 2001 Transport and Chemical Evolution over the Pacific (TRACE‐P) mission. The CO 2 spatial distributions were notably influenced by cyclogenesis‐triggered transport of regionally polluted continental air masses. Examination of the CO 2 to C 2 H 2 /CO ratio indicated rapid outflow of combustion‐related emissions in the free troposphere below 8 km. Although the highest CO 2 mixing ratios were measured within the Pacific Rim region, enhancements were also observed further east over the open ocean at locations far removed from surface sources. Near the Asian continent, discrete plumes encountered within the planetary boundary layer contained up to 393 ppmv of CO 2 . Coincident enhancements in the mixing ratios of C 2 Cl 4 , C 2 H 2 , and C 2 H 4 measured concurrently revealed combustion and industrial sources. To elucidate the source distributions of CO 2 , an emissions database for Asia was examined in conjunction with the chemistry and 5‐day backward trajectories that revealed the WNW/W sector of northeast Asia was a major contributor to these pollution events. Comparisons of NOAA/CMDL and JMA surface data with measurements obtained aloft showed a strong latitudinal gradient that peaked between 35° and 40°N. We estimated a net CO 2 flux from the Asian continent of approximately 13.93 Tg C day −1 for late winter/early spring with the majority of the export (79%) occurring in the lower free troposphere (2–8 km). The apportionment of the flux between anthropogenic and biospheric sources was estimated at 6.37 Tg C day −1 and 7.56 Tg C day −1 , respectively.