Atmospheric carbon dioxide record from continuous in situ measurements at American Samoa

Graphics

Digital Data

K.W. Thoning and P.P. Tans

National Oceanic and Atmospheric Administration, Climate Monitoring and Diagnostics Laboratory, Boulder, Colorado 80303, U.S.A

Period of Record

1976-1998

Methods

A URAS-2T nondispersive infrared CO₂ analyzer (NDIR) manufactured by Hartmann and Braun was used from the start of measurements at Cape Matatula, American Samoa until October 1990. Since then, a Siemens ULTRAMAT 5E CO₂ analyzer has been used.

Details on the sampling methods, NDIR apparatus, and calibration standards are provided in Komhyr et al. (1983), Thoning et al. (1987, 1995), and Zhang et al. (1997).

Additional data selection steps for the data through 1987 include a selection based on wind direction and wind speed and an hour-to-hour difference criterion that rejects data that change by more than 0.25 parts per million by volume (ppmv) from one hour to the next. For data since 1987, the wind direction and wind speed selection has not been applied. Instead, a selection step based on residuals from a spline fit (Thoning 1989) has been applied after the hour-to-hour selection.

American Samoa (Cape Matatula)
U.S. Territory, Pacific Ocean
An ancient barren lava flow atop
an island rocky promontory

14°15'S, 170°34'W
30 m above MSL

Trends

Since 1976 the annual atmospheric CO₂ concentration at Cape Matatula has risen from 331.45 parts per million by volume (ppmv) to 360.92 ppmv in 1996. Waterman et al. (1989) found that the average growth rate of CO₂ at Cape Matatula, American Samoa for 1976-1987 was 1.44 ppmv yr^-1 and found the interannual variability of the CO₂ growth rate correlates very well with that observed at other CMDL sites. For comparison, Conway et al. (1988) reported a growth rate of 1.35 ppmv yr^-1 from the NOAA/CMDL flask-sampling data from Cape Matatula, American Samoa for 1981-1984. Waterman et al. (1989) indicated the Cape Matatula record is characterized by the lack of a prominent seasonal cycle, with CO₂ concentrations for the first half of each year being more variable than those for the latter half of each year, when the wind flow is dominated by strong southeasterly trades. This record is considered indicative of maritime air for the central pacific region of the Southern Hemisphere.

References

Conway, T.J., P. Tans, L.S. Waterman, K.W. Thoning, K.A. Masarie, and R.H. Gammon. 1988.

Atmospheric carbon dioxide measurements in the remote global troposphere, 1981-84. Tellus 40(B):81-115.

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 National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory Global Air Sampling Network. Journal of Geophysical Research 99(D11):22831-55.

Halter, B.C., J.M. Harris, and T.J. Conway. 1988.

Component signals in the record of atmospheric carbon dioxide concentration at American Samoa. Journal of Geophysical Research 93:15914-18.

Komhyr, W.D., L.S. Waterman, and W.R. Taylor. 1983.

Semiautomatic nondispersive infrared analyzer apparatus for CO₂ air sample analyses. Journal of Geophysical Research 88:1315-22.

Thoning, K.W. 1989.

Selection of NOAA/GMCC CO₂ data from Mauna Loa Observatory. In W.P. Elliot (ed.), The Statistical Treatment of CO₂ Data Records. NOAA Technical Memorandum ERL ARL-173. Air Resources Laboratory, Silver Spring, Maryland.

Thoning, K.W., P. Tans, T.J. Conway, and L.S. Waterman. 1987.

NOAA/GMCC calibrations of CO₂-in-air reference gases: 1979-85. NOAA Technical Memorandum ERL ARL-150. Environmental Research Laboratory, Boulder, Colorado.

Thoning, K.W., P.P. Tans, and W.D. Komhyr. 1989.

Atmospheric carbon dioxide at Mauna Loa Observatory 2. Analysis of the NOAA GMCC data, 1974-85. Journal of Geophysical Research 94(D6):8549-65.

Thoning, K.W., T.J. Conway, N. Zhang, and D. Kitzis. 1995.

Analysis system for measurement of CO₂ mixing ratios in flask air samples. Journal of Atmospheric and Oceanic Technology 12(6):1349-56.

Waterman, L.S., D.W. Nelson, W.D. Komhyr, T.B. Harris, K.W. Thoning, and P.P. Tans. 1989.

Atmospheric carbon dioxide measurements at Cape Matatula, American Samoa, 1976-87. Journal of Geophysical Research 94(D12):14817-29.

Zhang, N., P.P. Tans, and K.W. Thoning. 1997.

A high precision manometric system for absolute calibrations of CO₂ in dry air. Journal of Geophysical Research 102(D5):5885-94.

CITE AS: Thoning, K.W. and P.P. Tans. 2000. Atmospheric CO₂ records from sites in the NOAA/CMDL continuous monitoring network. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

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February 2000