Login to WDCGG as

 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 109
Acronym GTRC
Name Gobabeb Training and Research Centre
 Background observation
 UTC
 permil
 9999-12-31 00:00:00 - 9999-12-31 23:59:59: PDB
 9999-12-31 00:00:00 - 9999-12-31 23:59:59: Unknown(Mass spectrometry)
 weekly
 PDB (Pee Dee Bellemnite) is a carbonate, and its link to CO2-in-air standards differs among laboratories. Ongoing intercomparison experiments are essential for assessing the comparability of isotope measurements from one lab with another (Masarie et al., 2001; Allison et al., 2003; Ghosh, P., Patecki, M., Rothe, M. and Brand, W.A. 2005). Measurement accuracy based on results from intercomparison experiments is 0.03 per mil.
 Samples are run daily from a cylinder whose isotope value is known: 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 uncertainty 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 November 2009, uncertanty is calculated with each run, and has been back-calculated to 2004. On the Optima (flask measurement system) uncertainty averages 0.014 permil for d13C and 0.035 permil for d18O; for the Isoprime (PFP system), uncertainty averages 0.017 permil for d13C and 0.04 permil for d18O.
 [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 t" 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 determined.

Samples are collected in pairs, and in order for a value to be retained, the flask pair difference must meet the threshold tolerance for the specific instrument being used. For samples analyzed prior to 1996 pairs must agree to within 0.09 per mil for C13 and 0.15 per mil for O18. For post-1996 analyses, done on both Optima and Isoprime mass spectrometers, pairs must agree to within 0.06 per mil for C13 and 0.12 per mil for O18.

Typically, pairs are flagged for pair rejection more frequently for d18O of CO2 than for d13C of CO2. The reason for the lower success rate in O18 pair agreement is likely related to the isotopic exchange of water vapor and CO2 in the flask during storage and analysis. This is dramatically demonstrated in the particularly low pair agreements at high humidity, low latitude sites. See Section 7, Data-General Comments for more details on the O18 data set.

FLAG DEFINITIONS
*********************Reject flags (1st flag character)********************
Automatic flags - applied daily during data reduction by a processing program
A problems in analysis or data reduction. Typically, the A is applied when the working references run at the beginning, middle, or end of the run have a standard deviation higher than 0.04 or 0.08 permil for d13C and d18O, respectively. For measurements prior to 1996, values differ by more than 0.075 and 0.14 permil, respectively.

+ bad pair (high member). Values differ by more than 0.06 or 0.12 permil for d13C and d18O, respectively. For measurements prior to 1996, values differ by more than 0.09 and 0.15 permil, respectively)
- bad pair (low menber). See above.
H The trap tank run on the same day has an average d13C or d18O value greater than 0.15 or 0.3 permil above its long term averages, respectively (since 2005.)
L The trap tank run on the same day has an average d13C or d18O value less than 0.15 or 0.3 permil above its long term averages, respectively (since 2005.)
. good flask

Flags applied periodically by code
C flagged for CO2 mole fraction (by NOAA CO2 measurement lab)
W flask sampled 'wet' (applied to o18 data only). See comments.
N/n problem due to sample collection (inherited from CO2 measurements)

Hand flags - applied by hand or in software (REFLAG) to selected flasks
! hand flag

*******************Non-background flags (2nd flag character)****************
ground flags - applied by outlier-identification software (CCG_FILTER)
X Outlier by more than 3-sigma from a CCGVU curve
x Outlier by more than 3-sigma in CO2 concentration
. Good flask

Hand flags - applied by hand to selected flasks
! hand flag

*********************Retain flags (3rd flag character)***********************
Automatic flags - applied during data reduction (by the processing program)
S - single flask (flask without a pair mate)
o - no trap data available for comparisons
H The trap tank run on the same day has an average d13C or d18O value greater than 0.045 or 0.09 permil above its long term averages, respectively (since 2005.)
L The trap tank run on the same day has an average d13C or d18O value less than 0.045 or 0.09 permil above its long term averages, respectively (since 2005.)
P Data has poor precision in dual inlet analysis: greater than 0.02 permil for d13C and 0.03 permil for d18O (since 2005).
T The trap tank run on the same day has high standard deviation of its (typically) three measurements: above 0.08 permil and 0.16 permil for d13C and d18O respectively (since 2005).

Additional flags
L linked flask (0.5-liter flask analyzed together with its mate)
I flask also analyzed by another lab (aliquot taken)
i same as "I" above, but displaced a previous flag in this field.
. no comments
 Operational/Reporting
 The INSTAAR-NOAA scale was known to be +0.82 per mil different from other labs measuring the d18O of CO2 in air, due to the temperature of the carbonate reaction that established the original CO2-in-air reference (Masarie et al., 2001; Allison et al., 2003). The application of a +0.82 per mil scale adjustment has been made as of November 2006 based on the results of the following comparisons: the CLASSIC cylinders; standards prepared by Hitoshi Mukai's NARCIS I and II; CO2 in air samples from W. Brand; flask inter comparisons with CSIRO (Cape Grim); and IAEA standard materials.
If air is sampled without drying, oxygen can exchange between carbon dioxide and water vapor in the flasks, in some cases entirely masking the desired signal (Gemery et al, 1996). While pair agreement flagging identifies most of the problem flasks, some flasks still have good pair aggreement and are within the normal range of acceptable values, even though they are biased by the influence of water vapor (Evans, 2008).
Comparisons between d18O of CO2 and specific humidity, calculated from the National Climatic Data Center (NCDC), show that at tropical and semi-tropical NOAA/ESRL sites, d18O of CO2 of non-dried samples has a seasonal cycle that is strongly anti-correlated to the specific humidity, while the d18O of dried samples display a seasonal cycle that occurs 1-2 months earlier than the specific humidity seasonal cycle. The latter phasing is expected, given the seasonal phasing between climate over the ocean and land; the former is consistent with a small, but measurable isotope exchange in the flasks.
Based on investigations by Evans et al (2008), a threshold of specific humidity, below which non-dried air flask samples can be considered unaltered, has been set at 12 g/kg, and this filter has been applied to the d18O of CO2 database. For example, for sites where specific humidity exceeds 12 g/kg, each non-dried flask sample has been matched to a NCDC measurement of specific humidity within
a 4-hour window. If specific humidity for that sample exceeded 12 g/kg, the SIL measurement for d18O is flagged with a 'W' (for wet) in the first position. If specific humidity data was unavailable, the sample is also flagged. Unfortunately there are several sites where the specific humidity is always above 12 g/kg (including CHR, GMI, POCN00, POCN05, POCN10, POCN15, POCS05, POCS10, POCS15, RPB, SEY, and SMO); therefore all data sampled without drying are flagged.
This approach segregates suspect and reliable data, providing a much-improved record of d18O of CO2 over the past two decades.
1  Mook, W.G. and J. Jongsma. 1987. Measurement of the N2O correction for 13C/12C ratios of atmospheric CO2 by removal of N2O. Tellus 39B: 96-99.
2  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, Journal of Geophysical Research 94: 8549-8565.
3  Assonov, S.S., and Brenninkmeijer, C.A.M. 2003. On the 17O correction for CO2 mass spectrometric isotopic analysis. Rapid Communications in Mass Spectrometry 17(10): 1007-1016.
4  Tans, P.P., T.J. Conway, and T. Nakazawa. 1989a. Latitudinal distribution of the sources and sinks of atmospheric carbon dioxide from surface observations and an atmospheric transport model. Journal of Geophysical Research 94: 5151-5172.
5  Brand, W.A., S.S. Assonov, and T.B. Coplen. 2009. Correction for the 17O interference in d13C measurements when analyzing CO2 with stable isotope mass spectrometry (IUPAC Technical Report). Journal of Pure and Applied Chemistry 82(8): 1719-1733.
6  Ciais, P., P.P. Tans, J.W.C. White, M. Trolier, R.J. Francey, J.A. Berry, D.R. Randall, R.J. Sellers, J.G. Collatz and D.S. Schimel. 1995. Partitioning of ocean and land uptake of CO2 as inferred by d13C measurements from the NOAA/CMDL global air sampling network, Journal of Geophysical Research 100: 5051-5070.
7  Ciais, P., P.P. Tans, M. Trolier, J.W.C. White and R.J. Francey. 1995. A large northern hemisphere terrestrial CO2 sink indicated by the 13C/12C ratio of atmospheric CO2. Science 269: 1098-1102.
8  Ciais, P., A.S. Denning, P.P. Tans, J.A. Berry, D.A. Randall, G.J. Collatz, P.J. Sellers, J.W.C. White, M. Trolier, H.A.J. Meyer, R.J. Francey, P. Monfray, and M. Heimann. 1997. A three-dimensional synthesis study of d18O in atmospheric CO2. 1. Surface fluxes. Journal of Geophysical Research 102: 5857-5872.
9  Ciais, P., P.P. Tans, A.S. Denning, R.J. Francey, M. Trolier, H.A.J. Meyer, J.W.C. White, J.A. Berry, D.A. Randall, G.J. Collatz, P.J. Sellers, P. Monfray, and M. Heimann. 1997. A three-dimensional synthesis study of d18O in atmospheric CO2. 2. Simulations with the TM2 transport model. Journal of Geophysical Research 102: 5873-5883.
10  Conway, T.J., P.P. Tans, L.S. Waterman, K.W. Thoning, D.R. Kitzis, K.A. Masarie, and N. Zhang. 1994. Evidence for interannual variability of the carbon cycle from the NOAA/CMDL global air sampling network. Journal of Geophysical Research 99: 22831- 22855.
11  Cuntz, M., P. Ciais, G. Hoffmann, C.E. Allison, R.J. Francey, W. Knorr, P.P. Tans, J.W.C. White, I. Levin. 2003. A comprehensive global three- dimensional model of delta O-18 in atmospheric CO2: 2. Mapping the atmospheric signal. Journal of Geophysical, Research- Atmospheres 108(D17): article 4528.
12  Evans, C.U. 2008. d18O of atmospheric carbon dioxide: Towards the development of an artifact free database from the NOAA/ESRL Carbon Cycle Cooperative Global Air Sampling Network. Masters Thesis, INSTAAR, University of Colorado, Boulder.
13  Francey, R.J., P.P. Tans, C.E. Allison, I.G. Enting, J.W.C. White and M. Trolier. 1995. Changes in oceanic and terrestrial carbon uptake since 1982. Nature 373: 326-330.
14  Gemery, P.A., M. Trolier, and J.W.C. White. 1996. Oxygen isotope exchange between carbon dioxide and water following atmospheric sampling using glass flasks. Journal of Geophysical Research - Atmospheres 101: 14415-14420.
15  Ghosh, P., M. Patecki, M. Rothe and W.A. Brand. 2005. Calcite-CO2 mixed into CO2-free Air: A New CO2 in-Air Stable Isotope Reference Material for the VPDB Scale. Rapid Communications in Mass Spectrometry 19: 1097-1119.
16  Miller, J.B., P.P. Tans, J.W.C. White, T.J. Conway, B.H. Vaughn. 2003. The atmospheric signal of terrestrial carbon isotopic discrimination and its implication for partitioning carbon fluxes. Tellus Series B-Chemical and Physical Meteorology 55(2): 197-206.
17  Tans, P.P, K.W. Thoning, W.P. Elliott, and T.J. Conway. 1989b. Background atmospheric CO2 patterns from weekly flask samples at Barrow, Alaska: Optimal signal recovery and error estimates, in NOAA Tech. Memo. (ERL ARL- 173). Environmental Research Laboratories, Boulder, CO, 131 pp.
18  Tans, P.P., I.Y. Fung, and T. Takahashi. 1990. Observational constraints on the global atmospheric CO2 budget. Science 247: 1431-1438.
19  Trolier, M., J.W.C. White, P.P. Tans, K.A. Masarie and P.A. Gemery. 1996. Monitoring the isotopic composition of atmospheric CO2: measurements from the NOAA Global Air Sampling Network. Journal of Geophysical Research 101: 25897-25916.
20  Vaughn, B., Ferretti, D., Miller, J. & White, J. 2004: Stable isotope measurements of atmospheric CO2 and CH4. Handbook of Stable Isotope Analytical Techniques, vol 1, ch.14, Elsiever, 1248 p.
21  For more publications see the Stable Isotope Lab web site at:
http://instaar.colorado.edu/research/labs-groups/stable-isotope-laboratory/publications-detail/
22  Battle. M., M.L. Bender, P.P. Tans, J.W.C. White, J.T. Ellis, T. Conway, and R.J. Francey. 2000. Global carbon sinks and their variability inferred from the atmospheric O2 and d13C. Science 287: 2467-2470.