16 June 2015

Supplemental information for flask data provided in the site-specific “multi-compound” files.  These files provide results for measurements at different sites (one file per site) for multiple compounds measured by gas chromatography with mass spectrometry detection.  Note that additional measurements are conducted on these flasks (gas chromatography with electron capture detection) but are reported elsewhere.  These data are provided by the Global Monitoring Division of the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory (NOAA/ESRL/GMD).

Measurements of halocarbons and other trace gases from flasks by gas chromatography with mass spectrometry detection.

Principal Investigators:  
Steve Montzka NOAA/GMD (303) 497-6657 (Stephen.A.Montzka@noaa.gov)
and 
Jim Elkins NOAA/GMD (303) 497-6224 (James.W.Elkins@noaa.gov) 
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 If you use this data in a presentation, publication, or report, NOAA and CDIAC policy requires that you contact the principal investigators first and discuss your interests.  By including this data here in electronic form, we are trying to encourage scientific interaction.  Furthermore, if you use the data in any presentation or publication, you must cite the appropriate articles in which these data were first presented and give credit to the National Oceanic and Atmospheric Administration (NOAA)/Global Monitoring Division (GMD) in Boulder, CO as a source of the data.  

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Key to the information provided in NOAA GCMS flask data files:

First column: 
Site where the flask sample was collected.  
Code legend for flask sampling locations: 

South Pole (SPO, 90°S, 2837 m asl)
Palmer Station, Antarctica (PSA, 64.6°S, 64.0°W, 15 m asl)
Cape Grim, Australia (CGO, 40.682°S, 144.688°E, 164 m asl or 70 m agl)
American Samoa (SMO, 14.247°S, 170.564°W, 77 m asl)
Mauna Loa, USA (MLO, 19.5362°N, 155.5763°W, 3433 m asl or 36 m agl)
Cape Kumukahi, USA (KUM, 19.516°N, 154.811°W, 39 m asl or 36 m agl) 
Niwot Ridge, USA (NWR, 40.1°N, 105.5°W, 3526 m asl or 3 m agl) 
Trinidad Head, USA (THD, 41.0°N, 124.1°W, 120 m asl)
Wisconsin, USA (LEF, 45.6°N, 90.27°W, 868 m asl or 396 m agl) 
Harvard Forest, USA (HFM, 42.5°N, 72.2°W, 340 m asl or 29 m agl)
Mace Head, Ireland (MHD, 53.3°N, 9.9°W, 42 m asl)
Barrow, USA (BRW, 71.3°N, 156.6°W, 27 m asl or 16 m agl) 
Alert, Canada (ALT, 82.5°N, 62.3°W, 210 m asl)
Summit, Greenland (SUM, 72.6°N, 38.4°W, 3209 + inlet m asl)

Second and third columns:
Sampling date and time expressed as a fraction of the year elapsed before the sample was collected, and, in the third column, expressed as yyyymmdd hhmmss.  

Note that 'SampleDate' includes the exact time of sampling (GMT) ONLY for data 
after November, 1994 ('SampleDate' for the oldest data has not been updated 
to include sample time; for example, a flask filled on 10 Feb 1994 at 1000 GMT 
would be indicated here as a decimal date corresponding to 
10 Feb 1994 at 0000 GMT).

Fourth column:

Sampling time in a separate field

Fifth and Sixth columns:
Wind direction and wind speed recorded at the time of sampling.  Values of nd or -99 indicate magnitudes that were not recorded.

Remaining columns:
The dry air mole fraction (in picomol per mol or parts per trillion) determined for the sample and 1 standard deviation of the mean mole fraction derived for the two simultaneously filled flasks.  Results are derived from the sampling and analysis of 2 stainless steel or glass flasks filled simultaneously.  Results appearing on the same row were obtained from the same flask pair.

Key to the compound names in this file:

Label in file		compound		chemical formula
HCFC22			HCFC-22			CHClF2
HCFC141B		HCFC-141b		CH3CCl2F
HCFC142B		HCFC-142b		CH3CClF2
CFC113			CFC-113			CCl2FCClF2
CH3CCl3			methyl chloroform	CH3CCl3	
HAL1211			H-1211			CBrClF2
hfc134a			HFC-134a		CH2FCF3
hf152a			HFC-152a		CH3CHF2
CH3BR			methyl bromide		CH3Br
OCS			carbonyl sulfide	OCS or COS
CH3Cl			methyl chloride		CH3Cl		
CH2Cl2			dichloromethane		CH2Cl2
pce			perchloroethylene	C2Cl4
Hal2402			H-2402			CBrF2CBrF2
F365_			HFC-365mfc		CH3CF2CH2CF3
F227_			HFC-227ea		CF3CHFCF3

Note that data for some additional halocarbons are not yet available (as of mid-2015) in the site-specific multi-compound files but measurements are posted by compound in their respective directories.  Those compounds include:
H-1301
HFC-125
HFC-32
HFC-143a

Other notes:
Data are reported in this file only if the flask pairs had no statistically discernable difference at the 90-95% confidence level; if the standard deviation of the individual flasks within a pair is larger than the instrument precision determined by replicate injections, those results are not included here.

Known data issues:
We strive to provide the highest quality data possible for all periods.  However, NOAA flask data obtained by the GCMS for some compounds analyzed during the 2008.5-2009.5 period are subject to some small biases owing to instrumental issues during that period.  Data obtained for CH3CCl3 during that time period, for example, should not be used for deriving hydroxyl radical concentrations. 

Furthermore, flask data for HCFC-142b shows some anomalously low values in recent years and specific seasons that are not yet flagged.  Work is ongoing to discern the cause and apply the appropriate flags, but as of 2013, this is not yet completed.

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For more information, see the articles in which portions of these data are published:

S. A. Montzka, J. H. Butler, R. C. Myers, T. M. Thompson, T. H. Swanson, A. D. Clarke, L. T. Lock, and J. W. Elkins, Decline in the tropospheric abundance of halogen from halocarbons: Implications for stratospheric ozone depletion, Science, 272, 1318-1322, 1996.

S. A. Montzka, J. H. Butler, J. W. Elkins, T. M. Thompson, A. D. Clarke, and L. T. Lock, Present and Future Trends in the Atmospheric Burden of Ozone-Depleting Halogens, Nature, 398, 690-694, 1999.

Scientific Assessment of Ozone Depletion Reports from 2003; 2007; 2011; and 2014. 

For brominated gases:
Montzka, S.A, J.H. Butler, B.D. Hall, J.W. Elkins, D.J. Mondeel, A decline in tropospheric organic bromine, Geophy. Res. Lett., 30(15), 1826, doi:10.1029/2003GL017745, 2003.

Butler, J.H., S.A. Montzka, A.D. Clarke, J.M. Lobert, J.W. Elkins, Growth and distribution of halons in the atmosphere, J. Geophys. Res., 103, 1503-1511, 1998.

For methyl chloroform:
Montzka, S.A., M. Krol, E. Dlugokencky, B. Hall, P. Jockel, J. Lelieveld, Small interannual variability of global atmospheric hydroxyl, Science, 331, 67-69, 2011.

Montzka, S.A., C.M. Spivakovsky, J.H. Butler, J.W. Elkins, L.T. Lock, and D.J. Mondeel, New observational constraints for atmospheric hydroxyl on global and hemispheric scales, Science, 288, 500-503, 2000.

For HCFCs and HFCs:
Montzka, S.A., M. McFarland, S.O. Andersen, B.R. Miller, D.W. Fahey, B.D. Hall, L. Hu, C. Siso, J.W. Elkins, Recent trends in global emissions of hydrochlorofluorocarbons and hydrofluorocarbons—Reflecting on the 2007 Adjustments to the Montreal Protocol, J. Phys. Chem. A, 119, 4439-4449, doi:10.1021/jp5097376, 2015.

Montzka, S.A., B.D. Hall, J.W. Elkins, Accelerated increases observed for hydrochlorofluorocarbons since 2004 in the global atmosphere, Geophys. Res. Lett., 36, L03804, doi:10.1029/2008GL036475, 2009.

Montzka, S.A., R.C. Myers, J.H. Butler, J.W. Elkins, L. Lock, A. Clarke, and A.H. Goldstein, Observations of HFC-134a in the remote troposphere, Geophys Res. Lett., 23, 169-172, 1996.

Montzka, S.A., R.C. Myers, J.H. Butler, and J.W. Elkins, Early trends in the global tropospheric abundance of hydrochlorofluorocarbon-141b and -142b, Geophys. Res. Lett., 21, 2483-2486, 1994.

Montzka, S.A., R.C. Myers, J.H. Butler, J.W. Elkins, and S.O. Cummings, Global tropospheric distribution and calibration scale of HCFC-22, Geophys Res. Lett., 20, 703-706, 1993.

Xiang, B., P.K. Patra, S.A. Montzka, S.M. Miller, J.W. Elkins, F.L. Moore, E.L. Atlas, B.R. Miller, R.F. Weiss, R.G. Prinn, S.C. Wofsy, Global emissions of refrigerants HCFC-22 and HFC-134a:  unforeseen seasonal contributions, Proc. Natl. Acad. Sci., doi:10.1073/pnas.1417372111, 2014.

For carbonyl sulfide:
Montzka, S.A., P. Calvert, B. Hall, J.W. Elkins, P. Tans, and C. Sweeney, On the global distribution, seasonality, and budget of atmospheric carbonyl sulfide (COS) and some similarities to CO2, J. Geophys. Res., 112, D09302, doi:10.1029/2006JD07665, 2007.

Montzka, S.A, M. Aydin, M. Battle, J.H. Butler, E.S. Saltzman, B.D. Hall, A.D. Clarke, D. Mondeel, J.W. Elkins, A 350-year atmospheric history for carbonyl sulfide inferred from Antarctic firn air and air trapped in ice, J. Geophys. Res., 109, D22302, doi:10.1029/2004JD004686, 2004.

Berry J., A. Wolf, J.E. Campbell, I. Baker, N. Blake, D. Blake, A.S. Denning, S.R. Kawa, S.A. Montzka, U. Seibt, K. Stimler, D. Yakir, Z. Zhu, A coupled model of the global cycles of carbonyl sulfide and CO2: A possible new window on the carbon cycle, J. Geophys. Res., 118, doi:10.1002/jgrg.20068, 2013.