CSIRO ATMOSPHERIC RESEARCH GASLAB FLASK CH4 DATA
RELEASE DATE: OCTOBER 2002

CONTACTS:

Paul Steele, CSIRO Atmospheric Research,
Private Bag 1, Aspendale, Victoria, Australia  3195
Telephone:   (+613) 9239 4578                     Fax:  (+613) 9239 4444
e-mail:  paul.steele@csiro.au

Paul Krummel, CSIRO Atmospheric Research,
Private Bag 1, Aspendale, Victoria, Australia  3195
Telephone:  (+613) 9239 4568                      Fax:  (+613) 9239 4444
e-mail:  paul.krummel@csiro.au

Ray Langenfelds, CSIRO Atmospheric Research,
Private Bag 1, Aspendale, Victoria, Australia  3195
Telephone:  (+613) 9239 4598                      Fax:  (+613) 9239 4444
e-mail:   ray.langenfelds@csiro.au


NOTICE:

*   The current version of the data represents the highest quality we can
provide at this time, in terms of alignment to a calibration scale, internal
consistency and precision. However, any data version should be considered
provisional only. Adjustments may be made in the future, as new or improved
information becomes available.

*   Please contact us at the above e-mail addresses if any clarification of
the meaning or limitations of the data is required. If users wish to send us
preprints of any publications using the data, we would be happy to check that
the data are being used within their limitations. 

*   We ask that use of this data in any paper or presentation be accompanied
by acknowledgement of the source of the data (CSIRO Atmospheric Research
GASLAB) and that the version of the data (as specified by release date) be
explicitly stated.


SAMPLING:

The listed data have been obtained from flask air samples returned to GASLAB
for analysis. The flasks are of 5 types: (i) glass 0.5 litre, sealed with two
stopcocks fitted with PTFE, PFA or Viton O-rings (flask identifier prefix
"G050"), (ii) glass 5.0 litre, sealed with two stopcocks fitted with PTFE
O-rings ("G500"), (iii) glass 0.8 litre, sealed with two stopcocks fitted with
PTFE or PFA O-rings ("G080"), (iv) electropolished stainless steel 1.6 litre
"Sirocans" fitted with two stainless steel valves manufactured by either Nupro
or Hoke ("S160"), (v) glass 2.0 litre sealed with a single stopcock fitted
with a Viton O-ring ("F", "FF", "FA", "FE", "EP", ALT") and provided by the
Meteorological Service of Canada for air sampling at the Canadian sites,
Alert, Estevan Point and Fraserdale. Experiments carried out to test for any
change in sample CH4 mixing ratio during storage have shown no drift to within
detection limits over test periods of several months to years (Cooper et al.,
1999). Typical sample storage times range from days to weeks for some sites
(e.g. Cape Grim, Aircraft) to as much as 1 year for Macquarie Island and the
Antarctic sites. 


ANALYSIS:

Samples were analysed by gas chromatography with flame ionisation detection
(FID). Three individual but similarly configured Carle gas chromatographs were
used over the length of the record. They are labelled "Carle-1" (C1),
"Carle-2" (C2) and "Carle-3" (C3). Further details are provided elsewhere of
CSIRO's global sampling network, sampling and analytical techniques (Francey
et al., 1996), and measurement uncertainty (Langenfelds et al., 2001a). 


CALIBRATION:

Data are reported in the CSIRO94 CH4 scale (Steele et al., 1996) which is
derived from the CH4 scale maintained at NOAA/CMDL (Dlugokencky et al., 1994).
The link to this scale was established with two high pressure cylinders
containing dry, natural air that were calibrated by NOAA/CMDL between 1987 and
1990. Results from later exchanges high-pressure cylinders indicate a small,
but measurable difference. Stability of the CSIRO scale is monitored with ~25
assorted long-lived standards. Instrument response has been evaluated with a
suite of six Nippon Sanso CH4-in-air standards (volumetrically prepared,
calibrated against a gravimetric scale at Tohoku University) spanning the
range 310-1845 ppb. Pre-1992 data that were previously reported (Fraser at
al., 1994, and references therein) in a scale derived from the scale used by
the Oregon Graduate Institute (OGI) have been adjusted here to be consistent
with the CSIRO94 CH4 scale. Details of calibration and measurement uncertainty
are given by Langenfelds et al. (2001a).


DATA PROCESSING:

Flask data are assigned flags to indicate whether they are classified as
retained or rejected. Cause of rejection falls into three broad categories:
(i) the sample is considered to be not representative of the atmosphere at
thetime and place of sampling due to identified or inferred sampling or
analytical problems (eg. sample contamination, poor analysis),
(ii) the sample is considered to be "non-baseline" as indicated by the
meteorological conditions at the time of sampling and
(iii) any remaining outliers are flagged on the basis of a 3 sigma filter
(geographically fixed sites only). For completeness, all data are included
here, regardless of whether they are retained or rejected. Please note that
for routine "baseline" applications, any rejected data must be actively
excluded from the provided data sets, while for "non-baseline" applications
data flagged under categories (ii) and (iii) above may carry biogeochemical
information (see DATA FORMAT section below). Also, further data selection may
be desirable for those data sets that cannot be screened by the 3 sigma filter
(e.g. AIA; aircraft).


DATA FILES:

Data are provided for samples collected at the following geographically fixed
sites:

     ALC   Alert, Canada (82 27'N, 62 31'W, 6 metres altitude)
     CFA - Cape Ferguson, Australia (19 17'S, 147 03'E, 2 m)
     CGA - Cape Grim, Australia (40 41'S, 144 41'E, 94 m) 
     EPC   Estevan Point, Canada (49 23'N, 126 32'W, 39 m)
     MAA   Mawson, Australia (67 37'S, 62 52'E, 32 m)
     MLU   Mauna Loa, Hawaii, USA (19 32'N, 155 35'W, 3397 m)
     MQA   Macquarie Island, Australia (54 29'S, 158 58'E, 12 m)
     SIS   Shetland, Scotland (60 10'N, 01 10'W, 30 m)
     SPU   South Pole, Antarctica (89 59'S, 24 48'W, 2810 m)

and from the following moving platforms:

     AIA - Aircraft (over Bass Strait and Cape Grim)

Files containing a single CH4 value for each sample are provided for each site
code (e.g. cga.ch4). For the geographically fixed sites, data are also
provided in the form of monthly means (e.g. cga_mm.ch4), which are calculated
as the mean of daily values from a smooth curve fit to the data using the
curve-fitting routines described by Thoning et al. (1989). 


DATA FORMATS:

Files listing individual flask data are provided in the following format. Note
that altitude, latitude and longitude coordinates are only included for moving
platform sites. Sign conventions employed for position coordinates are
positive for latitudes north and longitudes east.

sss yyyy mm dd hh mm xxxx-xxx c nnnnn.nn fff ii YYYY MM DD HH MM uuuuuu
aaaaa ttt.tttt gggg.gggg

     sss  three-letter site code
     yyyy mm dd     collection date (year, month, day; UT)
     hh mm       collection time (hour, minute; UT)
     xxxx-xxx  flask identifier
     c   sample collection method code (for the retained data:
         A = GASLAB flask pump unit (FPU) with anhydrous Mg(ClO4)2 drying,
         D = metal bellows pump   with anhydrous Mg(ClO4)2 drying,
         C = manual aircraft sampling unit with anhydrous Mg(ClO4)2 drying,
         H = automated aircraft sampling unit with anhydrous Mg(ClO4)2 drying,
         6 = method not directly recorded)
     nnn.nn    CH4  mixing ratio (ppb)
     fff     flags: "..." indicates no flags, sample retained.
Any entry other than "." in the first flag column indicates the sample is not
representative of the time and place of sampling: 
         A  = no sample taken
         B  = sample lost before analysis
         C  = identified sampling error
         D  = suspected sampling problem (eg. 2 or more species give           
                 anomalous values)
         E  = mixed samples (time/place not unique)
         N  = unacceptable analysis
         *   =  no analysis data available
         H  = species-specific manually applied rejection flag
         I    = species-specific sample collection problem
         J   = irretrievable sample storage effect
         .   = not subject to any of the above flags
Any entry other than "." in the second flag column indicates the sample is
non-baseline, rejected only on grounds of being an outlier or is excluded from
this data set because of a non-standard sampling technique. 
         F  = non-baseline meteorological conditions
         G  = marginal-baseline meteorological conditions
         K  = species-specific non-baseline meteorological conditions
         L  = species-specific marginal-baseline meteorological conditions 
         M =  3 sigma filter rejected
         O  =      non-standard sampling technique
         .    =    not subject to any of the above flags
     ii     analytical instrument code
            YYYY MM DD HH MM first analysis date and time
     uuuuuu     Universal Analysis Number (UAN; a number that uniquely
                identifies each sample)

For aircraft samples only:
     aaaaa      altitude (metres)
     ttt.tttt   latitude (decimal degrees)
     gggg.gggg  longitude (decimal degrees)


Files listing the monthly mean data are provided in the following format:
   yyyy mm nnnn.nn

       yyyy    year
       mm      month
       nnnn.nn CH4 (ppb)


REFERENCES:

Cooper, L.N., L.P. Steele, R.L. Langenfelds, D.A. Spencer and M.P. Lucarelli.
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, 1999. 

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.
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,
1996.

Francey, R.J., L.P. Steele, R.L. Langenfelds, C.E. Allison, L.N. Cooper. B.L.
Dunse, B.G. Bell, T.D. Murray, H.S. Tait, L. Thompson and K.A. Masarie.
Atmospheric carbon dioxide and its isotopes, methane, carbon monoxide, nitrous
oxide and hydrogen from Shetland. Atmos. Environ., 32, 3331-3338, 1998.

Francey, R.J., L.P. Steele, R.L. Langenfelds and B.C. Pak, High precision
long-term monitoring of radiatively-active trace gases at surface sites and
from ships and aircraft in the Southern Hemisphere atmosphere. J. Atmos.
Science., 56, 279-285, 1999.

Fraser, P.J., S.A. Coram and N. Derek. Atmospheric methane, carbon monoxide
and carbon dioxide by gas chromatography. Baseline Atmospheric Program
(Australia) 1991, edited by A.L. Dick and J.L. Gras, pp 60 - 64, Bureau of
Meteorology and CSIRO Division of Atmospheric Research, Melbourne, Australia,
1994.

Langenfelds, R.L., R.J. Francey, L.P. Steele, P.J. Fraser, S.A. Coram, M.R.
Hayes, D.J. Beardsmore, M.P. Lucarelli, and F.R. de Silva, Improved vertical
sampling of the trace gas composition of the troposphere above Cape Grim since
1991, in Baseline Atmospheric Program (Australia) 1993, edited by R.J.
Francey, A.L. Dick and N. Derek, pp 45-56, Bureau of Meteorology and CSIRO
Division of Atmospheric Research, Melbourne, Australia, 1996.

Langenfelds, R.L., L.P. Steele, C.E. Allison and R.J. Francey, GASLAB
Calibration Information, 2001.  Internal Report, CSIRO Atmospheric Research,
Aspendale, Australia, 2001a.

Langenfelds, R.L., L.N. Cooper,  L.P. Steele, D.A.Spencer, P.B. Krummel and
P.J. Fraser. Atmospheric methane, carbon dioxide, hydrogen, carbon monoxide
and nitrous oxide from Cape Grim flask air samples analysed by gas
chromatography. Baseline Atmospheric Program (Australia) 1997-98, edited by
N.W. Tindale, N. Derek, and R.J. Francey, pp 69 - 74, Bureau of Meteorology
and CSIRO Atmospheric Research, Melbourne, Australia, 2001b.

Langenfelds, R.L., R.J. Francey, L.P. Steele, D.A. Spencer and B.L. Dunse,
Flask sampling from Cape Grim overflights, in Baseline Atmospheric Program
(Australia) 1997-98, edited by N.W. Tindale, N. Derek and R.J. Francey, pp 74
- 84, Bureau of Meteorology and CSIRO Atmospheric Research, Melbourne,
Australia, 2001c.
 
Langenfelds, R.L., R.J. Francey, B.C. Pak, L.P. Steele, J. Lloyd, C.M.
Trudinger and C.E. Allison, The use of multi-species measurements for
interpreting interannual variability in the carbon cycle, 6th International
CO2 Conference: extended abstracts, Sendai, Japan, 9-11, 2001d.

Langenfelds, R.L., R.J. Francey, B.C. Pak, L.P. Steele, J. Lloyd, C.M.
Trudinger and C.E. Allison, Interannual growth rate variations of atmospheric
CO2 and its 13C, H2, CH4 and CO between 1992 and 1999 linked to biomass
burning, Glob. Biogeochem. Cycles, 2002, in press.

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, 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, 2001.

Pak, B.C., R.L. Langenfelds, R.J. Francey, L.P. Steele and I. Simmonds, A
climatology of trace gases from the Cape Grim overflights, 1992 - 1995, in
Baseline Atmospheric Program (Australia) 1994-5, edited by R.J. Francey, A.L.
Dick and N. Derek, pp 41-52, Bureau of Meteorology and CSIRO Division of
Atmospheric Research, Melbourne, Australia, 1996.

Pak, B.C., Vertical structure of atmospheric trace gases over Southeast
Australia, PhD Thesis, University of Melbourne, Australia, 273 pp. (available
at the Australian Digital Theses Project via
(http://adt1.lib.unimelb.edu.au/adt-root/public/), 2000.

Steele, L.P., R.L. Langenfelds, M.P. Lucarelli, P.J. Fraser, L.N. Cooper, D.A.
Spencer, S. Chea and K. Broadhurst. Atmospheric methane, carbon dioxide,
carbon monoxide, hydrogen and nitrous oxide from Cape Grim flask air samples
analysed by gas chromatography. Baseline Atmospheric Program (Australia)
1994-95, edited by R.J. Francey, A.L. Dick and N. Derek, pp 107 - 110, Bureau
of Meteorology and CSIRO Division of Atmospheric Research, Melbourne,
Australia, 1996. 

Thoning, K.W., P.P. Tans and W.D. Komhyr, Atmospheric carbon dioxide at Mauna
Loa Observatory, 2, Analysis of the NOAA/GMCC data, 1974 - 1985, J. Geophys.
Res., 94, 8549-8565, 1989.