The measurement of CO2 in air is made relative to reference standards whose mixing ratio is determined with high precision and accuracy. Because detector response is non-linear in the range of atmospheric levels, ambient samples are bracketed during analysis by a set of reference standards used to calibrate detector response. Measurements are reported in units of micromol/mol (10^-6 mol CO2 per mol of dry air or parts per million (ppm)). Measurement accuracy determined from repeated NDIR analyses of CO2 in standard gas cylinders using an absolute manometric technique is ~0.2 micromol/mol. Measurement precision determined from repeated analysis of the same air is ~0.1 micromol/mol. Average agreement between pairs of flasks sampled in series throughout the network is ~0.2 micromol/mol.
The air samples are collected by two general methods: flushing and then pressurizing glass flasks with a pump, or opening a stopcock on an evacuated glass flask. During each sampling event, a pair of flasks is filled.
Scientific Aim
Supporting Contributor(s)
Last update
2009-07-31
Situation
1999 07
This site is maintained by the Japan Meteorological Agency
in cooperation with the World Meteorological Organization
(Created : 2001/07/02 Modified : 2010/07/31)
WMO World Data Centre for Greenhouse Gases
c/o Japan Meteorological Agency
1-3-4, Otemachi, Chiyoda-ku
Tokyo 100-8122, Japan
WDCGG Data Submission and Dissemination Guide (PDF 1.2Mbyte)
WDCGG leaflet (PDF 2.7MByte, July 2008)
