Calibration for atmospheric nitrous oxide observation

JMA primary standard gases

   In the first rank of gases on which JMA's N₂O observations are based, the primary standard gases for N₂O are stored in five cylinders with concentrations ranging from about 280 to 340 ppb. The cylinders used to store these gases, which are mixtures of N₂O and natural air, have a volume of 48 liters and are made of aluminum alloy to minimize drift. The concentrations of the primary gases were determined accurately against the WMO reference standard gases maintained by NOAA/ESRL in December 2006 (Hall et al. 2007) . The standard scale is called NOAA 2006A, and assures the international traceability of JMA's observations.

JMA working standard gases

   The concentrations of working standard gases (the second-rank gases used at Ryori and stored in four 9.4-liter aluminum cylinders) are determined using the N₂O calibration system at JMA Headquarters based on the primary standard gases, and these working standard gases are then sent out to Ryori. After use in observation, the gases are sent back to JMA Headquarters to be checked for drift, and the concentrations are compared with those of the primary standard gases (see Atmospheric nitrous oxide observation ) .

   The calibration system for N₂O concentration is configured using a gas chromatograph analyzer with a radiative electron capture detector (GC-ECD: Shimadzu Corporation, GC-2014) . The repeatability of the N₂O calibration system does not exceed 3 ppb, which is determined by introducing standard gases ten times and taking the standard deviation for the mean peak area.

Hall, B. D., G. S. Dutton, and J. W. Elkins, 2007: The NOAA nitrous oxide standard scale for atmospheric observations, J. Geophys. Res., 112, D09305, doi:10.1029/2006JD007954.