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Atmospheric Hydrogen Record from Shetland Islands, Scotland
L.P. Steele, P.B. Krummel and R.L. Langenfelds
Commonwealth Scientific and Industrial Research Organization (CSIRO), Atmospheric Research,
Aspendale, Victoria, Australia, 3195
Period of Record
December 1992 - December 2001
The listed data have been obtained from flask air samples returned to the CSIRO GASLAB for analysis. Typical sample storage times range from days to weeks for some sites (e.g., Cape Grim) to as much as one year for Macquarie Island and the Antarctic sites. Experiments carried out to test for any change in sample H2 mixing ratio during storage have shown no consistent and systematic drift in these flask types over test periods of several months to years (Cooper et al., 1999).
Samples were analyzed by gas chromatography with a mercuric oxide reduction gas detector. H2 reduces HgO to Hg vapor which is detected by UV absorption. One Trace Analytical gas chromatograph, labeled "RGA3-1" (R1), was used over the length of the record. Further details of CSIRO's global sampling network, sampling, and analytical techniques are provided by Francey et al. (1996); measurement uncertainty is discussed by Langenfelds et al. (2001).
Data are reported in the CSIRO94 H2 scale which was defined by dilution of high purity H2 and CH4 (in a 1:3 ratio) with zero air to produce a mixture with H2 mole fraction close to atmospheric levels, and "bootstrapping" to a gravimetrically derived, absolute CH4 scale. The CH4 mixing ratio was then determined to be 1585.5 ppb, adjusted from the CSIRO94 CH4 scale to the gravimetrically derived scale of the Meteorological Research Institute, Japan (Matsueda, 1993). The hydrogen content of the mixture could then be determined as 528.5 ppb in dry air. The relationship of the CSIRO94 H2 scale to the gravimetrically derived H2 scale of NOAA/CMDL is not well-defined due to both time and concentration- dependent variations in the difference (see Masarie et al., 2001). Stability of the CSIRO scale is monitored with ~20 high-pressure cylinder standards, with lifetimes of 4-10+ years, spanning a H2 range of 430-1000 ppb. Most of these cylinders are of electropolished, stainless steel construction. In CSIRO's experience, the aluminum cylinders successfully used for long-term storage of calibration gases for other GASLAB species are generally not reliable for H2. Details of calibration and measurement uncertainty are given by Langenfelds et al. (2001).
These data represent monthly means calculated from the mean of the daily values from a smooth curve fit to the data using the curve- fitting routines described by Thoning et al. (1989).
Shetland Islands, Scotland
60°10' N, 01°10' W, 30 m above MSL
An annual cycle of H2 is evident, reflecting the seasonal nature of some of the major sources and sinks (Novelli et al., 1999). Annual average concentrations since 1992 have varied between 494 and 513 ppb, peaking in 1999. The maximum H2 increase for the Shetland Islands occurred from 1997-1998; the maximum globally averaged growth rate occurred in 1998 (Langenfelds et al., 2002).
- Cooper, L.N., L.P. Steele, R.L. Langenfelds, D.A. Spencer and M.P. Lucarelli. 1999. Atmospheric methane, carbon dioxide, hydrogen, carbon monoxide and nitrous oxide from Cape Grim flask air samples analysed by gas chromatography. Baseline Atmospheric Program (Australia) 1996, edited by J.L. Gras, N. Derek, N.W. Tindale and A.L. Dick, pp 98 - 102, Bureau of Meteorology and CSIRO Atmospheric Research, Melbourne, Australia.
- Francey, R.J., L.P. Steele, R.L. Langenfelds, M.P. Lucarelli, C.E. Allison, D.J. Beardsmore, S.A. Coram, N. Derek, F.R. de Silva, D.M. Etheridge, P.J. Fraser, R.J. Henry, B. Turner, E.D. Welch, D.A. Spencer and L.N. Cooper. 1996. Global Atmospheric Sampling Laboratory (GASLAB): supporting and extending the Cape Grim trace gas programs. Baseline Atmospheric Program (Australia) 1993, edited by R.J. Francey, A.L. Dick and N. Derek, pp 8 - 29, Bureau of Meteorology and CSIRO Division of Atmospheric Research, Melbourne, Australia.
- Langenfelds, R.L., L.P. Steele, C.E. Allison and R.J. Francey. 2001. GASLAB Calibration Information, 2001. Internal Report, CSIRO Atmospheric Research, Aspendale, Australia.
- Langenfelds, R.L., R.J. Francey, B.C. Pak, L.P. Steele, J. Lloyd, C.M. Trudinger, and C.E. Allison. 2002. Interannual growth rate variations of atmospheric CO2 and its delta 13C, H2, CH4, and CO between 1992 and 1999 linked to biomass burning, Global Biogeochem. Cycles 16(3), Paper 21, 22 pp.
- Masarie, K.A., R.L. Langenfelds, C.E. Allison, T.J. Conway, E.J. Dlugokencky, R.J. Francey, P.C. Novelli, L.P. Steele, P.P. Tans, B. Vaughn and J.W.C. White. 2001. NOAA/CSIRO Flask Air Intercomparison Experiment: A strategy for directly assessing consistency among atmospheric measurements made by independent laboratories, J. Geophys. Res., 106, 20,445-20,464.
- Matsueda, H. 1993. Intercalibration experiment of the methane standard gas scale between NOAA/CMDL and and MGI/GRL. Papers in Meteorology and Geophysics 44, 45-56.
- Novelli, P.C., P.M. Lang, K.A. Masarie, D.F. Hurst, R. Myers, and J.W. Elkins. 1999. Molecular Hydrogen in the troposphere: Global distribution and budget. J. Geophys. Res. 104, 30,427-30,444.
- 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 - 1985, J. Geophys. Res., 94, 8,549-8,565.
CITE AS: Steele, L. P., P. B. Krummel and R. L. Langenfelds. 2003. Atmospheric H<font size=-1><sub>2</sub></font> concentrations from sites in the CSIRO Atmospheric Research GASLAB air sampling network (October 2002 version). 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, TN, U.S.A.