Development of a new JMA flask sampling and trace gas measuring system for observation on a cargo aircraft C-130H

Abstract

Abstract. We developed and evaluated a flask air sampling system for atmospheric trace gas observation on a cargo C-130H aircraft, as well as an automated analysis system for the flask samples, as part of a new operational monitoring program of the Japan Meteorological Agency (JMA). Air samples were collected during each flight, between Kanagawa Prefecture (near Tokyo) and Minamitorishima (an island located nearly 2000 km southeast of Tokyo), from the air-conditioning system on the aircraft. The quality assurance test of the flask sampling air was made by specially coordinated flights at a low altitude of 1000 ft over Minamitorishima and comparing the flask values with those obtained at the surface. Based on our storage tests, the flask samples remained stable until analyses. The concentration measuring system for the flask samples has, in addition to the conventional sensors, two laser-based analyzers using wavelength-scanned cavity ring-down spectroscopy (WS-CRDS) and off-axis integrated cavity output spectroscopy (ICOS). Laboratory tests of the measuring system indicated relatively high reproducibility with overall precisions of less than 0.06 ppm for CO2, 0.68 ppb for CH4, 0.36 ppb for CO, and 0.03 ppb for N2O. Inter-comparison experiments for ambient air measurements showed excellent agreements between the laser-based measurement techniques and the conventional methods currently in use. We also found that there are no significant influences of isotope effects for the laser-based analyzers.