Effect of land-sea air masses transport on spatiotemporal distributions of atmospheric CO₂ and CH₄ mixing ratios over the south Yellow Sea

Abstract. To reveal the spatiotemporal distributions of atmospheric CO₂ and CH₄ mixing ratios and regulation mechanisms over the China shelf sea, two field surveys were conducted in the south Yellow Sea in China in November 2012 and June 2013, respectively. Observed results showed that mean atmospheric CO₂ and CH₄ mixing ratios were 403.50 ± 13.70 ppm and 1934.1 ± 33.6 ppb in November 2012, and 396.40 ± 12.30 ppm and 1919.2 ± 30.2 ppb in June 2013, respectively. An improved data filtering method were established to flag diverse sources of atmospheric CO₂ and CH₄ in survey area. Fe found that, compared to the influences of air-sea exchange, the spatiotemporal distributions of atmospheric CO₂ and CH₄ mixing ratios over the south Yellow Sea were dominated by land-sea air masses transport, which was driven by seasonal monsoon. In addition, atmospheric CO₂ and CH₄ mixing ratios over the south Yellow Sea could be elevated remarkably in a distance of approximate 20 km offshore by land-to-sea air masses transportation from the Asia Continent during early winter monsoon.