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 Organization

NO 2
Acronym NOAA
Name Earth System Research Laboratory, NOAA
Address 1 R/GMD1
Address 2 NOAA/ESRL
Address 3 325 Broadway Boulder, CO 80305-3337
Country/Territory United States of America
Website https://www.esrl.noaa.gov/gmd/index.html

 Contact(s)

Name James White
Prefix
Email James.White@colorado.edu
Organization No 34
Organization acronym INSTAAR
Organization name Institute of Arctic and Alpine Research, University of Colorado
Organization country/territory United States of America
Address 1 Institute of Arctic and Alpine Research
Address 2 Campus Box 450
Address 3 University of Colorado, Boulder, CO 80309-0450
Country/territory United States of America
Tel (303) 492-5494
Fax (303) 492-6388
Last updated date 2019-09-10


Name Bruce H Vaughn
Prefix
Email Bruce.Vaughn@colorado.edu
Organization No 34
Organization acronym INSTAAR
Organization name Institute of Arctic and Alpine Research, University of Colorado
Organization country/territory United States of America
Address 1 Institute of Arctic and Alpine Research
Address 2 Campus Box 450
Address 3 University of Colorado, Boulder, CO 80309-0450
Country/territory United States of America
Tel (303) 492-7985
Fax (303) 492-6388
Last updated date 2019-09-10


Name Sylvia Michel
Prefix
Email sylvia.michel@colorado.edu
Organization No 34
Organization acronym INSTAAR
Organization name Institute of Arctic and Alpine Research, University of Colorado
Organization country/territory United States of America
Address 1 Institute of Arctic and Alpine Research
Address 2 Campus Box 450
Address 3 University of Colorado, Boulder, CO 80309-0450
Country/territory United States of America
Tel (303)735-5850
Fax (303) 492-6388
Last updated date 2019-09-10


NO 87
Acronym NWS
Name U.S. National Weather Service
 Background observation
 UTC
 permil
 9999-12-31 00:00:00 - 9999-12-31 23:59:59: VPDB-CO2
 9999-12-31 00:00:00 - 9999-12-31 23:59:59: Unknown(Mass spectrometry)
 weekly
 Isotope data are reported as 'delta' values: the ratio of minor to major isotopes relative to a standard, VPDB-CO2. The 'delta' notation is

delta = [ (13C/12C)sam / (13C/12C)ref - 1 ] * 1000

and is expressed in units of 'permil' (parts per thousand).

All of the samples have been analyzed at the Stable Isotope Laboratory at CU-INSTAAR in Boulder, Colorado, using either a Micromass Optima or Micromass Isoprime isotope-ratio mass spectrometer coupled to a methane a custom-built trapping system, a gas chromatograph, and a combustion furnace. Measurement precision is approximately 0.1 permil for 13C (where 'precision' is taken as the standard deviation of three repeated measurements of standard air). Our isotopic scale for d13C of CH4 is tied to Stan Tyler's lab at the University of California Irvine. Current efforts to validate this scale and compare with other labs in the isotopic community are ongoing. For more information regarding calibrations of methane-in-air isotopes, see the recent review by Umezawa et al., 2017.
 We have recently added calculations of uncertainty for isotopes of methane. This relies on the performance of a cylinder of air whose isotopic value of methane is well characterized by long-term measurement. This "trap" tank alerts us to any problems with the mass spectrometer or extraction system. We also use this cylinder to calculate uncertainty, which we define as the standard deviation of ten runs' worth of trap measurements. Usually four trap samples are run a day, of which all but the first are used (due to known irregularities caused by the tank regulator). For each run, the uncertainty is calculated from the trap data from that run, regardless of its flagging, and the previous nine runs of unflagged data. (For example, if the current run is flagged, that trap data will be used in the ncertainty calculation; however, the next day's run will not use the flagged data in its uncertainty calculation. Presumably, whatever caused one run to be flagged will have been repaired.) As of Dec 2013, uncertanty is calculated with each run, and has been back-calculated to 2006.
 [Hourly]
 [Daily]
 [Monthly] Monthly means are produced for each site by first averaging all valid measurement results in the event file with a unique sample date and time. Values are then extracted at weekly intervals from a smooth curve (Thoning et al., 1989) fitted to the averaged data and these weekly values are averaged for each month to give the monthly means recorded in the files. Flagged data are excluded from the curve fitting process. Some sites are excluded from the monthly mean directory because sparse data or a short record does not allow a reasonable curve fit. Also, if there are 3 or more consecutive months without data, monthly means are not calculated for these months.
 NOAA ESRL uses a 3-column quality control flag where each column is defined as follows:

column 1 REJECTION flag. An alphanumeric other than a period (.) in the FIRST column indicates a sample with obvious problems during collection or analysis. This measurement should not be interpreted.

column 2 SELECTION flag. An alphanumeric other than a period (.) in the SECOND column indicates a sample that is likely valid but does not meet selection criteria determined by the goals of a particular investigation.

column 3 INFORMATION flag. An alphanumeric other than a period (.) in the THIRD column provides additional information about the collection or analysis of the sample.

WARNING: A "P" in the 3rd column of the QC flag indicates the measurement result is preliminary and has not yet been carefully examined by the PI. The "P" flag is removed once the quality of the measurement has been assessed.

Reject flags (1st flag character)

A known problem in analysis (poor precision of measured standard air)
a analysis problem (specifics unknown)
! Hand-flagged by INSTAAR researcher: analytical problem.
E specific analysis problem due to extraction manifold problem
B specific analysis problem due to transfer pump

n known sampling problem -- taken from NOAA CH4 data base
+ bad pair, high member
- bad pair, low member
. good flask

Data measured after 2006 may have these flags:
H mean of trap (cylinder of known isotopic value run as sample) in same run as sample was more than 0.3 permil above the long-term mean
L mean trap value in same run as sample was more than 0.3 permil below the long term mean
T trap samples had unusually high variance (0.2 permil)
P small peak (less than 3 nA) - too low for accurate analysis
Y peak too large (greater than 18 nA) - swamps collectors
D too much drift; more than 0.25 permil drift in the reference gas

Data measured before 2006 may have these flags:
D a second aliquot taken more than 20 days after the first
2 a 'D' flag applied over another hard flag (e.g., D+n=2 or D+A=2)
M a third or greater aliquot taken more than 20 days after the first
3 a 'M' flag applied over another hard flag (e.g., T+n=2 or T+A=2)

------------------------------------------------------------------------------
Non-background flags (2nd flag character)

X outlier by more than 3-sigma from a smooth curve fit to CH4C13 data
x outlier flag taken from CH4 data (ie, outlier in CH4 concentration)
Z hand-flagged by NOAA (not INSTAAR) researchers
. good flask
-----------------------------------------------------------------------------
Retain flags (3rd flag character)

S flask analyzed singly, without its mate
. good flask
I intercomparison sample
i intercomparison sample flag overwriting previous (now lost) flag
 Operational/Reporting
 
1  Conway, T.J., Tans, P.P., Waterman, L.S., Thoning, K.W., Kitzis, D.R., Masarie, K.A., and Zhang, N. 1994. Evidence for interannual variability of the carbon cycle from the NOAA/CMDL global air sampling network, JGR 99, 22831- 22855.
2  Miller, J. B., Mack, K. A., Dissly, R., White, J. W. C., Dlugokencky, E. J. and Tans, P. P. 2002. Development of analytical methods and measurements of 13C/12C in atmospheric CH4 from the NOAA/CMDL global air sampling network. J. Geophys. Res. 107, doi: 10.1029/2001JD000630.
3  Thoning, K.W., Tans, P.P., and Komhyr, W.D. 1989, Atmospheric carbon dioxide at Mauna Loa Observatory 2. Analysis of the NOAA GMCC Data, 1974-1985, J. Geophys. Res., 94, 8549-8565.
4  Vaughn, B., Ferretti, D., Miller, J. and White, J. 2004. Stable isotope measurements of atmospheric CO2 and CH4. Handbook of Stable Isotope Analytical Techniques, vol 1, ch. 14, Elsevier, 1248 p.
5  Umezawa, T., Brenninkmeijer, C., Rockmann, T., van der Veen, C., Tyler, S. C., Fujita, R., Morimoto, S., Aoki, S., Sowers, T., Schmitt, J., and Bock, M. (2018). Interlaboratory comparison of d13C and dD measurements of atmospheric CH4 for combined use of data sets from different laboratories. Atmospheric Measurement Techniques.