Characteristics of atmospheric CO2 and CH4 at the Shangdianzi regional background station in China

Atmospheric CO2 and CH4 have been continuously measured at the Shangdianzi regional background station (SDZ) in China from 2009 to 2013. Based on the influences of local surface wind and long-distance transport, the observed records were flagged into locally influenced, Beijing-Tianjin-Hebei (BTH) influenced, and Russia, Mongolia, and Inner Mongolia autonomous region influenced (RMI). similar to 81.4% of CO2 and similar to 75.6% of CH4 mole fractions were flagged as locally representative, indicating that the atmospheric CO2 and CH4 at SDZ were strongly influenced by local sources and sinks. Cluster analysis of back trajectories proved that the atmospheric CO2 and CH4 were influenced by air masses from northwest (RMI) or from south and southeast (BTH). The CO2 and CH4 mole fractions in BTH are always higher than in RMI, with the largest difference of 11.5 +/- 0.3 ppm for CO2 and 102 +/- 1 ppb for CH4 in July. The annual growth rates of CO2 and CH4 in BTH are 3.8 +/- 0.01 ppm yr(-1) and 10 +/- 0.1 ppb yr(-1), respectively, which are apparently higher than those of the RMI and the global means. The long-term trends of CO2 and CH4 in BTH are deviating from those in RMI, with ratios of similar to 1.0 ppm yr(-1) for CO2 and similar to 2 ppb yr(-1) for CH4, indicating the strengths of CO2 and CH4 emission in Beijing-Tianjin-Hebei plain increased more than 20% every year. (C) 2016 Elsevier Ltd. All rights reserved.