Data Policy
GAW Data Policy
"For Scientific purposes, access to these data is unlimited and provided without charge.
By their use you accept that an offer of co-authorship will be made through personal contact with the data providers
or owners whenever substantial use is made of their data.
In all cases, an acknowledgement must be made to the data providers or owners and to the data centre when these data are used within a publication."
Version
2025-04-28-1830 (Last updated: 2025-05-09)File
This data set is submitted by NOAA.
In line with the GAW Data Policy, users should contact the contributors of all data of interest and propose co-authorship or acknowledgement.
Organization
| NO | 2 |
|---|---|
| Acronym | NOAA |
| Name | Global Monitoring Laboratory, NOAA |
| Address 1 | NOAA/ESRL |
| Address 2 | R/GML1 |
| Address 3 | 325 Broadway Boulder, CO 80305-3328 |
| Country/Territory | United States of America |
| Website | https://gml.noaa.gov/ |
Contact(s)
| Name | Xin Lan |
|---|---|
| Prefix | |
| xin.lan@noaa.gov | |
| Organization No | 2 |
| Organization acronym | NOAA |
| Organization name | Global Monitoring Laboratory, NOAA |
| Organization country/territory | United States of America |
| Address 1 | NOAA GML |
| Address 2 | 325 Broadway R/GML-1 |
| Address 3 | Boulder, CO 80305-3328 |
| Country/territory | United States of America |
| Tel | |
| Fax | |
| Last updated date | 2025-04-28 |
| Background observation | |
| UTC | |
| ppb | |
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9999-12-31 00:00:00 - 9999-12-31 23:59:59: WMO CH4 X2004A |
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1986-01-29 04:00:00 - 2012-06-01 23:00:00: Unknown(Gas chromatography (FID)) 2013-04-11 00:00:00 - 2024-12-31 23:00:00: Unknown(off-axis integrated cavity output spectroscopy (OA-ICOS)) |
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| 10 seconds | |
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GC/FID systems were calibrated with a single-point calibration; each aliquot of ambient air was bracketed by aliquots of standard gas, and CH4 in each air sample was calculated based on the ratio of the sample chromatographic peak response to the average response of the bracketing standards, and the assigned value for the standard cylinder. For laser-based spectrometers, the analyzer response is calibrated with a suite of standards every two weeks relative to a reference cylinder, and the reference cylinder is measured hourly to track and correct short term analyzer drift. As a quality assurance step, a well-calibrated "target" cylinder is measured up to twice per day. NOAA methane measurements are reported on the gravimetrically-prepared NOAA X2004A CH4 standard scale (see Dlugokencky et al., 2005; https://gml.noaa.gov/ccl/ch4_scale.html). |
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| Measurement uncertainties (value_unc_1) are calculated for each measurement (individual aliquot on GC and 5-minute average on optical spectrometer) based on analytical repeatability and reproducibility, and our ability to propagate the WMO CH4 mole fraction standard scale. For GCs, analytical repeatability is based on the stability of standard or reference aliquots averaged over the period a particular instrument was used. It varies with analytical instrument from 5.5 to 0.9 ppb. For laser-based spectrometers, it is based on the standard deviations of the bracketing measurements of reference gas. Reproducibility is based on a comparison of near-simultaneous flask-air samples measured independently in Boulder and quasi-continuous hourly averaged measurements at MLO and BRW observatories. It is assessed from the median difference, and it ranges from 0.1 to 0.9 ppb. The scale propagation term is based on the uncertainty we assign to standards, 0.5 ppb. All terms are given as 68% confidence intervals. Although we still list "value_sd" of hourly averages (standard deviation of values that go into an hourly average as described above, which includes natural variability and measurement uncertainty), we now list measurement uncertainty as a separate term. For the hourly average uncertainty, repeatability is divided by sqrt n, where "n" is the number of observations used in the calculation. Reproducibility and scale propagation terms are applied once. Total uncertainty is calculated by adding the individual terms in quadrature (square root of the sum of the squares). Methane hourly average values outside the range of standards are assigned a default uncertainity (-999.999). | |
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[Hourly] For GC/FID systems, hourly averages were calculated from all valid measurements within an hour and reported in our data files with the number of measurements (nvalue) and standard deviation (value_sd). For n=1, value_sd cannot be calculated. For spectrometer systems, 5-minute averages are used to calculate hourly averages, but value_sd includes variability in the 5-min averages, so it is greater than the normal sample SD of the 5-min averages that go into the hourly mean, and when nvalue=1 (i.e., one 5-min average in the hourly mean), value_sd is still calculated and reported. [Daily] Daily values derived from hourly data representative of baseline conditions [Monthly] Monthly values derived from hourly data representative of baseline conditions |
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| This is the NOAA 3-character quality control flag. Column 1 is the 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 is the 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 is the INFORMATION flag. An alphanumeric other than a period (.) in the THIRD column provides additional information about the collection or analysis of the sample. | |
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Valid (background): ... Valid (background): ..? Valid: .?? Invalid: ??? |
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| Operational/Reporting | |
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Atmospheric Methane Dry Air Mole Fractions from quasi-continuous measurements at Barrow, Alaska. These data are provided by NOAA. Principal investigators include Xin Lan (NOAA). Please cite the product's citation when using data from this dataset : K.W. Thoning, X. Lan, A.M. Crotwell, and J.W. Mund (2025), Atmospheric methane from quasi-continuous measurements at Barrow, Alaska and Mauna Loa, Hawaii, 1986-present. Version: 2025-04-26, National Oceanic and Atmospheric Administration (NOAA), Global Monitoring Laboratory (GML), Boulder, Colorado, USA https://doi.org/10.15138/ve0c-be70 |
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Wind direction: Wind speed: Relative humidity: Precipitation amount: Air pressure: Air temperature: Dew point temperature: Sea water temperature: Sea surface water temperature: Sea water salinity: Sea surface water salinity: |
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Meteorological data may remain as first provided, even when greenhouse gas data are updated. |
DOI Metadata
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| For more information, please refer: doi.org/10.15138/ve0c-be70 | |||||||||||||
Related information
| Format | Text (WDCGG Data Format Table, WDCGG Meteorological Data Format Table), NetCDF | ||||
|---|---|---|---|---|---|
| Relation List (Is Part Of) |
All CH4 data contributed to WDCGG by GAW stations and mobiles by 2024-09-24 All CH4 data contributed to WDCGG by GAW stations and mobiles by 2023-09-13 All CH4 data contributed to WDCGG by GAW stations and mobiles by 2022-09-07 All CH4 data contributed to WDCGG by GAW stations and mobiles by 2021-08-27 All CH4 data contributed to WDCGG by GAW stations and mobiles by 2020-09-28 All CH4 data contributed to WDCGG by GAW stations and mobiles by 2019-09-19 All CH4 data contributed to WDCGG by GAW stations and mobiles by 2018-10-25 |
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GAW Data Policy
"For Scientific purposes, access to these data is unlimited and provided without charge.
By their use you accept that an offer of co-authorship will be made through personal contact with the data providers
or owners whenever substantial use is made of their data.
In all cases, an acknowledgement must be made to the data providers or owners and to the data centre when these data are used within a publication."
Citation format
This format is an example of the WDCGG standard citation.
Please follow the citation format which the data providers or owners indicate.
Please follow the citation format which the data providers or owners indicate.
Xin Lan (NOAA),
Atmospheric CH4
at Barrow (AK) by Global Monitoring Laboratory, NOAA
,
dataset published as CH4_BRW4003_
surface-insitu_NOAA_ccgg at WDCGG,
ver. 2025-04-28-1830 (Reference date*: YYYY/MM/DD)
* As the reference date, please indicate the date you downloaded the files.
* As the reference date, please indicate the date you downloaded the files.
Reference(s)
| 1 | K.W. Thoning, X. Lan, A.M. Crotwell, and J.W. Mund (2025), Atmospheric methane from quasi-continuous measurements at Barrow, Alaska and Mauna Loa, Hawaii, 1986-present. Version: 2025-04-26, National Oceanic and Atmospheric Administration (NOAA), Global Monitoring Laboratory (GML), Boulder, Colorado, USA https://doi.org/10.15138/ve0c-be70 |
|---|---|
| 2 | Dlugokencky, E. J., L. P. Steele, P. M. Lang and K. A. Masarie, (1995), Atmospheric methane at Mauna Loa and Barrow observatories: Presentation and analysis of in situ measurements, Journal of Geophysical Research-Atmospheres, 100, d11, 23103-23113, doi:10.1029/95JD0246. |
