DB1001

The ALE / GAGE / AGAGE Network
(updated and revised August 2001)

R. Prinn, Massachusetts Institute of Technology; D. Cunnold, Georgia Institute of Technology; P. Fraser, Commonwealth Scientific and Industrial Research Organisation; R. Weiss, Scripps Institution of Oceanography; P. Simmonds, Bristol University; S. O'Doherty, Bristol University; L.P. Steele, Commonwealth Scientific and Industrial Research Organisation; P. Salameh, Scripps Institution of Oceanography; and R.H.J. Wang, Georgia Institute of Technology

In the ALE/GAGE/AGAGE global network program, continuous high frequency gas chromatographic measurements of two biogenic/anthropogenic gases (methane, CH₄; nitrous oxide, N₂O; and six anthropogenic gases (chlorofluorocarbons CFCl₃, CF₂Cl₂, and CF₂ClCFCl₂; methyl chloroform, CH₃CCl₃; chloroform, CHCl₃; and carbon tetrachloride, CCl₄) are carried out at five globally distributed sites. Additional important species (H₂, CO, HFC-134a, HCFC-141b, and HCFC-142b) have been added at select sites in recent years. 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 containing a custom-designed sample module and HP5890 and Carle Instruments gas chromatographic components. The GC-MS is a fully automated system produced at the University of Bristol and comprised of an adsorption-desorption preconcentration module and HP5973 gas chromatographic and mass spectrometric module.

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), and Trinidad Head, California (41° N, 124° W). Stations also previously existed at Cape Meares, Oregon (45° N, 124° W), and Adrigole, Ireland (52° N, 10° W). The current Mace Head station replaced the Adrigole station and the station at Trinidad Head replaced the Cape Meares station.

Presently, data from all three experiments are available. Data through September 2000 are now available for all five existing sites. 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 based upon the same standards. All ALE/GAGE/AGAGE data presented here are reported in the SIO-1998 calibration scale (Prinn et al., 2000).

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.