DB1001

The ALE / GAGE / AGAGE Network

Links to additional sources:

• Advanced Global Atmospheric Gases Experiment (AGAGE) home page
• How halocarbons (CFCs, HFCs, HCFCs, and halons) are named
• CDIAC data base including some of the same compounds, and a tabulation of their uses and atmospheric lifetimes

Investigators

R.G. Prinn, R.F. Weiss, P.J. Fraser, P.G. Simmonds, S. O'Doherty, P. Salameh, L. Porter, P. Krummel, R.H.J. Wang, B. Miller, C. Harth, B. Greally, F.A. Van Woy, L.P. Steele, J. Muehle, G. Sturrock, F.N. Alyea, J. Huang, and D.E. Hartley

DOI

10.3334/CDIAC/atg.db1001

Description

In the ALE/GAGE/AGAGE global network program, continuous high frequency gas chromatographic measurements of four biogenic/anthropogenic gases (methane, CH₄; nitrous oxide, N₂O; hydrogen, H; and carbon monoxide, CO) and several anthropogenic gases that contribute to stratospheric ozone destruction and/or to the greenhouse effect have been carried out at five globally distributed sites for several years. Recently additional stations at Jungfraujoch, Switzerland and Zeppelin Mountain, Norway have been added to the network. Data are currently available for all measured species listed in the table below. Units are dry air mole fractions in parts per 10¹² (picomoles/mole) for all halocarbons and SF₆, and parts per 10⁹ (nanomoles/mole) for nitrous oxide, methane, carbon monoxide and hydrogen.

The program, which began in 1978, is divided into three parts associated with three changes in instrumentation: the Atmospheric Lifetime Experiment (ALE), which used Hewlett Packard HP5840 gas chromatographs; the Global Atmospheric Gases Experiment (GAGE), which used HP5880 gas chromatographs; and the present Advanced GAGE (AGAGE). AGAGE uses two types of instruments: a gas chromatograph with multiple detectors (GC-MD), and a gas chromatograph with mass spectrometric analysis (GC-MS). The GC-MD is a new fully automated system produced at the Scripps Institution of Oceanography and includes a custom-designed sample module plus HP5890 and Carle AGC-211 gas chromatographic components. The original GC-MS was a fully automated system produced at the University of Bristol and comprised of an adsorption-desorption preconcentration module and an HP5973 gas chromatographic and mass spectrometric module. Beginning in January 2004, an improved cryogenic preconcentration system (Medusa) replaced the absorption-desorption module in the GC-MS systems at Mace Head and Cape Grim; this provided improved capability to measure a broader range of volatile perfluorocarbons with high global warming potentials. The Medusa system is now used at all current AGAGE stations. Further details on this upgrade may be found at the AGAGE home page.

http://agage.eas.gatech.edu/instruments-gcms-medusa.htm

The current station locations are Cape Grim, Tasmania (41° S, 145° E), Cape Matatula, American Samoa (14° S, 171° E), Ragged Point, Barbados (13° N, 59° W), Mace Head, Ireland (53° N, 10° W), Trinidad Head, California (41° N, 124° W), Jungfraujoch, Switzerland (47° N, 8° E), and Zeppelin Mountain, Norway (79° N, 12° E). Stations also previously existed at Cape Meares, Oregon (45° N, 124° W) and Adrigole, Ireland (52° N, 10° W). The Mace Head station came on line in January 1987 as a replacement for the Adrigole station which ceased operations at the end of December 1983; the Trinidad Head station began operations during AGAGE in October 1995, as an essential replacement for the Cape Meares station from which GAGE data were not available after June 1989.

Data from all three experiments are posted. AGAGE data through September 2010 are now available for all existing sites except for the latest addition, Zeppelin Mountain, where data as yet only extend through December 2008, and Cape Matatula, Samoa, where data for s few species only extend through April 2010. Individual measurements (generally made 4 times daily at each site for ALE, 12 times daily at each site for GAGE, and more than 30 times daily at each site for AGAGE) and monthly summary averages are provided for each site. All ALE and GAGE data have been recalculated according to the current AGAGE calibration standards, thus creating a unified ALE/GAGE/AGAGE data set. All ALE/GAGE/AGAGE data previously reported based on the Scripps Institution of Oceanography (SIO)-1998 calibration scale are now recalibrated to the SIO-2005 scale; more information about instrumentation and calibration for ALE, GAGE and AGAGE is given by Prinn et al. (2000). Please see the "readme" files and (for gc-md) the "COcalibration.doc" and "H2calibration.doc" files for information on calibration of individual species.

More extensive information about AGAGE may found from the AGAGE home page.

Reference:

• Prinn, R.G., R.F. Weiss, P.J. Fraser, P.G. Simmonds, D.M. Cunnold, F.N. Alyea, S. O'Doherty, P. Salameh, B.R. Miller, J. Huang, R.H.J. Wang, D.E. Hartley, C. Harth, L.P. Steele, G. Sturrock, P.M. Midgely, and A. McCulloch. 2000. A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE. Journal of Geophysical Research 105: 17751-17792.

¹No longer used for sampling. Replaced by the station at Mace Head, Ireland (53° N, 10° W).
²No longer used for sampling. Replaced by the station at Trinidad Head, California (41° N, 124° W).
³A tsunami on September 30, 2009 caused a power shutdown that prevented measurements of many gases at this station from October 2009 through February 2010.
⁴Carbon monoxide (CO) data for Cape Grim, Tasmania, after December 1999 are also temporarily removed in this update due to a non-linear problem. It will be added after an appropriate correction is applied.
⁵Recent Medusa perchloroethylene (tetrachloroethylene)(C₂Cl₄) data have not been subjected to "blank correction". Those data are still preliminary and will be updated after the blank correction is applied.

Updated February 2012.