Characteristics Variation of Atmospheric CO₂ and CH₄ in Yongxing Island, South China Sea

Using the observation data in Yongxing Island, South China Sea (SCS) from December 2013 to November 2018, the multiple time scales variation of atmospheric CO₂ and CH₄ were analyzed to understand their temporal variation characteristics and controlling factors. The regional-averaged background mole fractions of CO₂ and CH₄ both show a single-period sinusoidal variation with a lower value at noon and a higher value in the wee hours. In the seasonal scale, they exhibited a significant seasonal difference with higher values in winter and lower values in summer. In the annual scale, CO₂ and CH₄ both show an increasing trend, with an annual growth rate of approximately 3.2 ppm and 12 ppb, respectively. The annual growth rate at this site was higher than the global average. The change in atmospheric CO₂ and CH₄ in Yongxing Island was probably caused by the higher emission of the surrounding areas and the airflows driven by monsoon. Hopefully, the long-term and high-resolution greenhouse gases (GHGs) dataset will aid relevent researchers and decision-makers in performing more in-depth studies for GHG sources in order to derive effective strategies.