World Data Centre for Greenhouse Gases (WDCGG)

Category	Air sampling observation
Sampling Type	flask
Sampling Height/Depth
Sampling and Analysis Frequency	Weekly
Sampling Environment
Measurement Method
Current status and history of Instruments	GC-HgO
Description of Instruments	Trace Analytical lnc.
Time Zone
Data Period	2002-04-01 - 2009-12-31
Data Type	event, monthly
Parameter detail
Other Descriptions for Sampling and Analyses	Through most of the 1988-1991, one flask of a sample pair was analyzed for CO, and when there was suitable pressure remaining in the flask, two or more aliquots were analyzed. CO mixing ratios between two aliquots were used as an indication of the precision of the measurement. Details of the analytical procedures through 1990 are described in Novelli et al., 1992. Since October 1991, a single aliquots from both members of a flask pair (rather than 2 or more aliquots from a single flask) is analyzed. The principle reasons for the change were to simplify flask handling procedures and to have flask pair agreement (the difference in mixing ratio between the two flasks collected simultaneously) as an additional diagnostic to use in evaluating the quality of the data. 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. From the beginning of CO measurements in flask samples (mid 1987) to December 1990, a single point calibration sequence was used because the response characteristics of the CO instrument had been shown to be linear over a range of 0 to 1000 ppb CO. Since January 1991, a multiple standard calibration scheme (a multi-point calibration procedure based upon that used for calibaration of standards) has been used, as the new instrument exhibites a non-linear response over the range of 0 to 250 ppb CO. The non-linear detector requires a multipont calibraton (6 standards are used in the atmospheric range). Measurements are reported in units of nanomol/mol (10^-9mol CO per mol of dry air (nmol/mol) or parts per billion (ppb)) relative to the WMO CO scale (Novelli et al., 1991, Novelli et al., 1994, Novelli et al., 1998). Reproducibility of measurements, based on repeated analysis of air from a high-pressure cylinder, is 1 nmol/mol at 50 nmol/mol and 2 nmol/mol at 200 nmol/mol over the period of the measurements. The absolute accuracy of CO scale is unknown. 1987-1990: Reduction Gas Detector (R2) 1991-mid 1997: Reduction Gas Analyzer (RGA7) mid (1997-present: Reduction Gas Analyzer (RGA5)
Scientific Aim
Supporting Contributor(s)
Last update	2010-07-23
Situation	ongoing

Category	Parameter	Country/Territory	Contributor

Updated in
the last 365 days

This site is maintained by the Japan Meteorological Agency
in cooperation with the World Meteorological Organization
(Created : 2001/07/02 Modified : 2010/09/02)

WMO World Data Centre for Greenhouse Gases
c/o Japan Meteorological Agency
1-3-4, Otemachi, Chiyoda-ku
Tokyo 100-8122, Japan

Tel:	+81-3-3287-3439
Fax:	+81-3-3211-4640
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