Carbon Dioxide and Methane in the China Sea Shelf Boundary Layer Observed by Cavity Ring-Down Spectroscopy

Abstract

AbstractHigh-accuracy continuous ship-based cavity ring-down spectroscopy was used to simultaneously measure the mixing ratios of the carbon dioxide and methane in the China Sea shelf boundary layer for the first time, from 22 March to 2 April 2013. The mixing ratios of CO2 and CH4 ranged from 397.40 to 432.40 µmol mol−1 and from 1812.8 to 2068.7 nmol mol−1, respectively. Measurement data showed latitudinal distributions, with a slight fluctuation between 35.52° and 22.00°N but a sharp decline from 22.00° to 20.50°N. This distribution was not only the result of airmass transport from the Asian continent and Pacific Ocean induced by winter monsoon and trade winds but also by air–sea exchange and atmospheric chemical processes. Moreover, mixing ratios of CO2 and CH4 showed a temporal and spatial correlation that was possibly due to the effects of multisource air masses and their mixed status.