Variations in satellite-derived carbon dioxide over different regions of China from 2003 to 2011

Variations of CO2 mole fraction (XCO2) on a global or country-wide scale have been widely examined, while the regional differences within China remain unclear because of the huge differences in the stage of economic development and climatic diversities. In this study, the variations of monthly and yearly XCO2 from 2003 to 2011 are analyzed for the entire China and its six geographical regions. Atmospheric Infrared Sounder (AIRS) data, which are mainly sensitive in the mid-troposphere, were used. During 2003-2011, the mean annual XCO2 increased from 375.7 ± 3.3 to 392.5 ± 3.5 ppm, at a rate of +2.10 ppm/year, which is similar to the previous rate during 2003-2008 (+2.09 ppm/year). However, there are two new findings for different regions of China. First, the XCO2 growth rate and its seasonal amplitude were higher in Northern China than in Southern China. The growth rates of XCO2 over North-East, North, and North-West during 2003-2011 are 2.18, 2.17, and 2.13 ppm/year, respectively, while they are 2.03, 2.05, and 2.09 ppm/year over South-East, Central, and South-West, respectively. The seasonal CO2 fluctuations over the North-East and North are larger than other regions. Second, the highest monthly mean XCO2 of mid-troposphere occurs during April to May for different regions of China in 2003-2011, while the lowest XCO2 is September for southern China and January for northern China. These results offer valuable insights into the regional differences of XCO2 within China.