Interpreting seasonal changes of low-tropospheric CO2 over China based on SCIAMACHY observations during 2003–2011

The atmospheric carbon dioxide (CO2) concentration exhibits a strong seasonal variation. Analyzing the regional seasonal cycle could help to improve the interpretation of the sources and sinks of CO2 over certain areas. Based on a long-term (2003–2011) retrieved dataset from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY), the seasonal cycle and inter-annual variations of column-averaged dry air mole fraction of atmospheric carbon dioxide (XCO2) over China have been analyzed. The result shows that XCO2 over China increases by about 4.2% from 2003 to 2011, but the seasonal fluctuation keeps the similar pattern with the average peak-to-peak amplitude of 9.35 ppm. The highest concentration appears in spring, and the lowest value always occurs in summer. Based on the multi-year averages, it can be discerned that the seasonal signal of XCO2 increases during colder seasons with a drop during the period from December to February of the following year. The potential affecting factors are also discussed in this manuscript, including Normalized Difference Vegetation Index (NDVI), air temperature, and industrial productions in Thermal Power Generation (TPG) and cement that are relative main contributors for the anthropogenic CO2 of China. The seasonal variations of CO2 are highly connected with the changes of NDVI and air temperature. While the increase of the anthropogenic CO2 emission over China since 2003 is probably caused by the rapid growth of coal combustion and cement manufacture.