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Cape Kumukahi
-CO2-
| Observation |
| Category |
: |
Air sampling observation |
| Situation |
: |
ongoing |
| Time zone |
: |
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| Sampling |
| Sampling height |
: |
|
| Description |
: |
flask |
| Sampling and analysis frequency |
: |
Weekly |
| Sampling environment |
: |
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| Description for sampling analysis |
: |
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. |
| Instrument and Analysis |
| Measurement method |
: |
NDIR |
| Current status and history of instrument |
: |
NDIR |
| Description of instrument |
: |
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| Calibration |
| Current scale employed in the measurement |
: |
WMO CO2 mole fraction scale |
| Measurement calibration |
: |
CO2-in-air reference gases. |
| Scale and calibration(treasability) |
: |
WMO CO2 mole fraction scale |
| Data Processing |
| Measurement unit |
: |
ppm |
| Data processing |
: |
Corrections have been applied to CO2 mixing ratios measured on the flask analysis apparatus in use from July 1987 through April 1998. The corrections are +0.1 ppm to samples measured from July 1987 through 18 November 1993, and +0.24 ppm to samples measured from 19 November 1993 through 10 April 1998.
Corrections for drifting reference gas cylinders have been applied to all samples measured during 1995 through 2004.
Data selection (flagging) for 2003 and 2004 is not yet final. Only minor changes are expected. These files will be updated when final data selection is complete.
Files obtained previously from this site should be discarded and replaced with the revised files contained in this version.
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| Processing for averaging |
: |
Processing for Monthly Data:
Monthly means are produced for each site by first averaging all valid measurement results in the event file with a unique sample date and time. Values are then extracted at week intervals from smooth curve (Thoning et al., 1989) fitted to the averaged data and these weekly values are averaged for each month to give the monthly means. Flagged data are excluded from the curve fitting process. If there are 3 or more consecutive months without data, monthly means are not calculated for these months. |
| Data flag |
: |
WARNING: A QC flag assignment of "PRE" indicates the measurement result is preliminary and has not yet been carefully examined by the PI. The "PRE" flag is removed once the quality of the measurement has been determined.
Samples are collected in pairs, the pair difference is calculated, and samples with a pair difference greater than 0.5ppm ("bad pairs") are flagged. Through 1988 on or both members of a bad pair were sometimes retained if they fell within +/- 3 residual standard deviations rejected. Retained and rejected flasks are flagged as follows.
@ flag Description
Retained ... : (3 periods) good pair (D <= 0.5ppm)
..H : high member of bad pair ; retained
..L : low member of bad pair ; retained
Rejected .X. : rejected as not representative of backbround conditions (>3 sigma from a fitted curve)
.Z. : rejected manually as not representative of background conditions (this is necessary to
prevent distortion of the curve used for automated data selection)
+.. : high member of bad pair ; rejected
-.. : low member of bad pair ; rejected
*.. : off scale or broken flask; rejected
N.. : rejected due to error in sampling or analysis
T.. : sample collected as part of a methods test; not used in data analysis
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| Data remarks |
: |
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| Other Information |
| Scientific aim |
: |
To determine the global distribution and temporal variations of atmospheric CO2. Deduce CO2 sources and sinks. |
| Reference |
: |
Conway, T.J., P.P. Tans, L.S. Waterman, K.W. Thoning, D.R. Kitzis, K.A. Masarie, and N. Zhang, 1994, Evidence for interannual variability of the carbon cycle from the NOAA/CMDL global air sampling network, J. Geophys. Res., 99, 22,831-22,855.
Conway, T.J., P. Tans, L.S. Waterman, K.W. Thoning, K.A. Masarie, and R.H. Gammon, 988, Atmospheric carbon dioxide measurements in the remote global troposphere, 1981-1984, Tellus, 81-115.
Komhyr, W.D., L.S. Waterman, and W.R. Taylor, 1983, Semiautomatic nondispersive infrared analyzer apparatus for CO2 air sample analyses, J. Geophys. Res., 88, ,315-1,322.
Komhyr, W.D. R.H. Gammon, T.B. Harris, L.S. Waterman, T.J. Conway, W.R. Taylor, and K.W. Thoning, 1985, Global atmospheric CO2 distribution and variations from 1968-1982 NOAA/GMCC CO2 flask sample data, J. Geophys. Res., 90, 5,567-5,596.
Tans, P.P., T.J. Conway, and T. Nakazawa, 1989a, Latitudinal distribution of the sources and sinks of atmospheric carbon dioxide from surface observations and an atmospheic transport model, J. Geophys. Res., 94, 5,151-5,172.
Tans, P.P., K.W. Thoning, W.P. Elliott, and T.J. Conway, 1989b, Background atmospheirc CO2 patterns from weekly flask samples at Barrow, Alaska: Optimal signal recovery and error estimates, in NOAA Tech. Memo. (ERL ARL-173). Environmental Research Laboratories, Boulder, CO, 131 pp.
Tans, P.P., I.Y. Fung, and T. Takahashi, 1990, Observational constraints on the global atmospheric CO2 budget, Science, 247, 1,431-1,438.
Thoning, K.W., P. Tans, T.J. Conway, and L.S. Waterman, 1987, NOAA/GMCC calibrations of CO2-in-air reference gases: 1979-1985. NOAA Tech. Memo. (ERL ARL-150). Environmental Research Laboratories, Boulder, CO, 63pp.
Thoning, K.W., P.P. Tans, and W.D. Komhyr, 1989, Atmospheic carbon dioxide at Mauna Loa Observatory 2. Analysis of the NOAA GMCC data, 1974-1985, J. Geophys. Res., 94, 8,549- 8,565.
Thoning, K.W., T.J. Conway, N. Zhang, and D. Kitzis, 1995, Analysis system for measurement of CO2 mixing ratios in flask air samples, J. Atmos. and Oceanic Tech., 12, 1,349-1,365. |
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| submitted by NOAA/ESRL Global Monitoring Division ( the former CMDL ) |
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