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Radiocarbon Composition of Atmospheric Carbon Dioxide
(Delta-14CO2) from the NOAA ESRL Carbon Cycle Surface
PFP Sampling Network, 2009-2011.
Version: 2013-12-02
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CONTENTS
1. Data source and contacts
2. Use of data
2.1 Citation
3. Reciprocity
4. Warnings
5. Update notes
6. Introduction
7. DATA - General Comments
7.1 DATA - Sampling Locations
7.2 DATA - File Name Description
7.3 DATA - Event with single parameter
7.4 DATA - Event with multiple parameters
7.5 DATA - QC Flags
8. Data retrieval
9. References
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1. DATA SOURCE AND CONTACTS
University of Colorado, INSTAAR
and
National Oceanic and Atmospheric Administration (NOAA)
Earth System Research Laboratory (ESRL)
Global Monitoring Division (GMD)
Carbon Cycle Greenhouse Gases (CCGG)
Correspondence concerning these data should be directed to:
John Miller
NOAA ESRL Global Monitoring Division
325 Broadway, GMD-1
Boulder, CO 80305
U.S.A.
or
Scott Lehman
INSTAAR
University of Colorado at Boulder
1560 30th St
Boulder, CO 80309-0450
U.S.A.
email: John.B.Miller@noaa.gov
Scott.Lehman@colorado.edu
INX results
Correspondence should be directed to:
Jocelyn Turnbull
National Isotope Centre
GNS Science
30 Gracefield Rd
Lower Hutt
New Zealand
email: j.turnbull@gns.cri.n
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2. USE OF DATA
These data are made freely available to the public and the
scientific community in the belief that their wide dissemination
will lead to greater understanding and new scientific insights.
The availability of these data does not constitute publication
of the data. NOAA relies on the ethics and integrity of the user to
insure that ESRL receives fair credit for their work. If the data
are obtained for potential use in a publication or presentation,
ESRL should be informed at the outset of the nature of this work.
If the ESRL data are essential to the work, or if an important
result or conclusion depends on the ESRL data, co-authorship
may be appropriate. This should be discussed at an early stage in
the work. Manuscripts using the ESRL data should be sent to ESRL
for review before they are submitted for publication so we can
insure that the quality and limitations of the data are accurately
represented.
2.1 CITATION
Please reference these data as
J.B. Miller, S.J. Lehman (2011),
University of Colorado, Institute of Alpine and Arctic Research
(INSTAAR), Radiocarbon Composition of Atmospheric Carbon Dioxide
(14CO2) from the NOAA ESRL Carbon Cycle Air Sampling Network,
2009-2011, Version: 2013-12-02
For INX results
J.C. Turnbull and S.J. Lehman (2013),
GNS Science and University of Colorado Institute of Alpine and
Arctic Research, Radiocarbon Composition of Atmospheric Carbon
Dioxide (14CO2) from the Indianapolis Flux Project (INFLUX),
2010-2013, Version: 2013-12-02
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3. RECIPROCITY
Use of these data implies an agreement to reciprocate.
Laboratories making similar measurements agree to make their
own data available to the general public and to the scientific
community in an equally complete and easily accessible form.
Modelers are encouraged to make available to the community,
upon request, their own tools used in the interpretation
of the ESRL data, namely well documented model code, transport
fields, and additional information necessary for other
scientists to repeat the work and to run modified versions.
Model availability includes collaborative support for new
users of the models.
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4. WARNINGS
+++++++++++++++++++++++++++++++
Lab-wide notes:
Every effort is made to produce the most accurate and precise
measurements possible. However, we reserve the right to make
corrections to the data based on recalibration of standard gases
or for other reasons deemed scientifically justified.
We are not responsible for results and conclusions based on use
of these data without regard to this warning.
+++++++++++++++++++++++++++++++
Project-specific notes:
2011-10-01
The data file format has been modified to include the measurement group
and, additionally, the sample collection and analysis times now include
second information (e.g., 2011 03 15 23 06 12). See section 7.3 for
details.
2010-10-01
The format of the NOAA ESRL data records has been changed to include
an estimate of the uncertainty associated with each measurement. The
determination of the estimate is trace gas specific and described in
section 6 (INTRODUCTION).
+++++++++++++++++++++++++++++++
Parameter-specific notes:
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5. UPDATE NOTES
No changes have been made to these datasets since they
were first uploaded to this site.
Files obtained previously from this site should be discarded
and replaced with the revised files contained in this version.
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6. INTRODUCTION
A "Programmable Flask Package" was developed in the early 1990s for
use in our aircraft project to collect vertical profiles of air
samples. These packages (PFPs) are analyzed on the same analytical
systems used for the CCGG's global cooperative air sampling network
samples to measure CO2, CH4, CO, H2, N2O, and SF6. Many of the PFPs
are also analzed by the HATS group by GCMS for a suite of CFCs, HFCs,
HCFCs, NMHCs, and a few other species.
As a quality control step, we began deploying PFPs at some surface
sites in 2006. Most of these sites are tall towers, where the PFP
measurements can be compared with continuous in situ measurements of
CO2 and CO. Samples are collected approximately daily from one of
the tower intakes.
The Delta 14CO2 values reported in these files were measured
from air samples collected in Programmable Flask Packages
(PFPs) at NOAA ESRL Carbon Cycle Surface Sampling Network sites.
PFPs contain 12, 0.7L glass flasks into which 2.7bar of air is
filled. For all samples, CO2 was cryogenically extracted from
whole air at INSTAAR. Then CO2 was then reduced to graphite
with hydrogen over an iron catalyst and packed into aluminum
targets, then measured for 14C content by Accelerator Mass
Spectrometry (AMS). Several different graphitization laboratories
and AMS facilities may be used, and are indicated by the
instrument code for each sample:
1st letter of instrument code indicates graphitization laboratory
c : University of Colorado INSTAAR
l : Lawrence Livermore National Laboratory Center for Accelerator Mass Spectrometry
r : Rafter Radiocarbon Laboratory, GNS Science
2nd letter of instrument code indicates AMS laboratory
i : University of California Irvine
l : Lawrence Livermore National Laboratory Center for Accelerator Mass Spectrometry
r : Rafter Radiocarbon Laboratory, GNS Science
Descriptions of the sample preparation and measurement are given
in Turnbull et al., 2007; details of the 14C reporting conventions
are given by Stuiver and Polach, 1977 (note that we use the DELTA
notation with decay correction given in their Table 1) and Donahue
et al, 1990. Analysis and interpretation of other sources of NOAA/ESRL
14C data have been reported in Turnbull et al., 2006, Turnbull et al., 2007
and Miller et al., 2012
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7. DATA - GENERAL COMMENTS
The radiocarbon content of carbon dioxide in ambient and
standard air samples is measured by: (1) Cryogenic extraction
of CO2 from whole air; (2) Reduction of the collected CO2 with
hydrogen over an iron catalyst; and (3) accelerator mass
spectrometric measurement of the carbon isotopic ratio.
Measurements are made relative to NBS Oxalic Acid I, which
is measured concurrently with each batch of authentic samples,
and reported as Delta 14C, the permil deviation of the sample
14C/C ratio from that of the absolute radiocarbon standard.
All results are corrected for 14C blank, and radioactive decay
between the time of collection and measurement, and are normalized
to a delta 13C value of -25 permil. The blank is characterized
by concurrently prepared and measured 14C-free synthetic air,
and is typically 45,000-50,000 radiocarbon years BP. The
normalization correction is applied using the 13C content
determined online in the accelerator mass spectrometer (UC Irvine,
RRL after 2010), or from the 13C value obtained from CO2 in the same
sample (RRL prior to 2010). These reported values follow standard
radiocarbon procedures as described by Stuiver and Polach (1977)
and Donahue et al. (1990). For UC Irvine measurement, uncertainties
are determined as the largest of; the "statistical" uncertainty
derived from the number of 14C atoms counted during AMS measurement;
and the repeatability of replicate measurements of air aliquots
extracted from a single tank of air over time. For RRL measurement,
uncertainties are determined as the sum in quadrature of the statistical
uncertainty and the long-term "system error" determined from the
repeatability of replicate measurements of air aliquots over time.
Typical uncertainties are 1.8-2.0 permil. These procedures and additional
quality checks are described by Turnbull et al., 2007 and Lehman et al., 2013.
Also note that for surface PFP samples, 14CO2 is typically measured
only for every other sampling instance. For example, for a tower PFP
site where a pair of PFP samples is collected every day, 14CO2 will be
measured only on every second pair.
Note that reproducibility within a single AMS measurement wheel may
be better than the long-term repeatability. When results from a single
measurement wheel are compared, it may be appropriate to use the
within-wheel reproducibility. Please contact us for more detail.
Sampling frequencies are approximately daily.
The air samples are collected using an automated Programmable Flask
Package (PFP).
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7.1 DATA - SAMPLING LOCATIONS
Table of NOAA GMD aircraft sampling sites.
The table includes the three letter code used to identify each
site; the site name; latitude, longitude, and altitude (meters
above sea level) of the sampling location; the first and last sample
dates; and sampling status.
Note: Data for all species may not be available for all sites listed
in the table.
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7.2 DATA - FILE NAME DESCRIPTION
Encoded into each file name are the parameter (trace gas identifier); sampling
site; sampling project; laboratory ID number; measurement group; and optional
qualifiers that further define the file contents.
All file names use the following naming scheme:
1 2 3 4 5 6
[parameter]_[site]_[project]_[lab ID number]_[measurement group]_[optional qualifiers].txt
1. [parameter]
Identifies the measured parameter or trace gas species.
(ex)
co2 Carbon dioxide
ch4 Methane
co2c13 d13C (co2)
merge more than one parameter
2. [site]
Identifies the sampling site code.
(ex)
brw
pocn30
car
amt
3. [project]
Identifies sampling platform and strategy.
(ex)
surface-flask
surface-pfp
surface-insitu
aircraft-pfp
aircraft-insitu
tower-insitu
4. [lab ID number]
A numeric field that identifies the measurement laboratory (1,2,3, ...).
NOAA ESRL is lab number 1 (see http://www.esrl.noaa.gov/gmd/ccgg/obspack/labinfo.html).
5. [measurement group]
Identifies the group with NOAA and INSTAAR that makes the actual measurement.
See Section 5 (UPDATE NOTES) for details.
(ex)
ccgg
hats
arl
sil
6. [optional qualifiers]
Optional qualifier(s) may indicate data subsetting or averaging.
Multiple qualifiers are delimited by an underscore (_). A more detailed
description of the file contents is included within each data file.
(ex)
event All measurement results for all collected samples (discrete (flask) data only).
hour_#### Computed hourly averages for the specified 4-digit year (quasi-continuous data only)
day Computed daily averages (quasi-continuous data only)
month Computed monthly mean values
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7.3 DATA - EVENT WITH SINGLE PARAMETER
The data files "ccg/co2c14/flask/event/" use the following naming
scheme (see Section 7.2):
[parameter]_[site]_[project]_[lab ID number]_[measurement group]_[optional qualifiers].txt
(ex) CH4_lef_surface-pfp_1_ccgg.txt contains CH4 ccgg measurement
results for all surface pfp samples collected at Park Falls, Wisconsin.
The data files contain multiple lines of header information followed by one
record for each atmospheric measurement of a single parameter or trace gas species.
Fields are defined as follows:
Field 1: [SITE CODE] The three-character sampling location code (see above).
Field 2: [YEAR] The sample collection date and time in UTC.
Field 3: [MONTH]
Field 4: [DAY]
Field 5: [HOUR]
Field 6: [MINUTE]
Field 7: [SECOND]
Field 8: [FLASK ID] The sample container ID.
Field 9: [METHOD] A single-character code that identifies the sample
collection method. The codes are:
A - Sample collected using a Programmable Flask Package (PFP).
Field 10: [TRACE GAS NAME] Gas identifier (e.g., co2, co2c13).
Field 11: [MEASUREMENT GROUP] Identifies the group within NOAA and
INSTAAR making the actual measurement (e.g., ccgg, hats, arl).
See Section 5 (UPDATE NOTES) for details.
Field 12: [MEASURED VALUE] Dry air mole fraction or isotopic composition.
Missing values are denoted by -999.99[9].
Field 13: [ESTIMATED UNCERTAINTY] Estimated uncertainty of the reported
measurement value. Missing values are denoted by -999.99[9].
Field 14: [QC FLAG] A three-character field indicating the results of our
data rejection and selection process, described in section 7.5.
Field 15: [INSTRUMENT] A 2-character code that identifies the instrument
used for the measurement.
Field 16: [YEAR] The measurement date and time in LT.
Field 17: [MONTH]
Field 18: [DAY]
Field 19: [HOUR]
Field 20: [MINUTE]
Field 21: [SECOND]
Field 22: [LATITUDE] The latitude where the sample was collected, (negative (-)
numbers indicate samples collected in the southern hemipshere).
Field 23: [LONGITUDE] The longitude where the sample was collected, (negative (-)
numbers indicate samples collected in the western hemisphere).
Field 24: [ALTITUDE] The altitude where the sample was collected (masl).
Field 25: [EVENT NUMBER] A long integer that uniquely identifies the sampling
event.
Fields in each line are delimited by whitespace.
(ex)
LEF 2011 10 12 20 30 46 3108-08 A ch4 CCGG 1902.040 -999.990 ... H6 2011 11 01 08 06 00 45.9451 -90.2732 868.00 325975
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7.4 DATA - EVENT WITH MULTIPLE PARAMETERS
On special request we can distribute a "merged" file, which
includes for each sampling event, measurement results for muliple
parameters or trace gas species. A merged file does not include all
information found in a single parameter data file. For example,
merged files exclude measurement uncertainty, analysis instrument
ID and date and time for each parameter. Thus, the single parameter
data file is our most comprehensive data archive.
The format of a merged file is slightly different from single parameter event file.
A "merged" file will have the word "merge" in the parameter field of the file name.
The file name does not inform on the number of parameters included in the file.
Merged data files use the following naming scheme (see Section 7.2):
merge_[site]_[project]_[lab ID number]_[measurement group]_[optional qualifiers].txt
(ex) merge_lef_surface-pfp_1_ccgg.txt contains ccgg measurement results for two or
more parameters for all surface pfp samples collected at Park Falls, Wisconsin.
The data files contain multiple lines of header information followed by one
record for each atmospheric measurement of a single parameter or trace gas species.
Fields are defined as follows:
Field 1: [SITE CODE] The three-character sampling location code (see above).
Field 2: [YEAR] The sample collection date and time in UTC.
Field 3: [MONTH]
Field 4: [DAY]
Field 5: [HOUR]
Field 6: [MINUTE]
Field 7: [SECOND]
Field 8: [FLASK ID] The sample container ID.
Field 9: [METHOD] A single-character code that identifies the sample
collection method. The codes are:
A - Sample collected using a Programmable Flask Package (PFP).
Field 10: [LATITUDE] The latitude where the sample was collected, (negative (-)
numbers indicate samples collected in the southern hemipshere).
Field 11: [LONGITUDE] The longitude where the sample was collected, (negative (-)
numbers indicate samples collected in the western hemisphere).
Field 12: [ALTITUDE] The altitude where the sample was collected (masl).
Field 13: [EVENT NUMBER] A long integer that uniquely identifies the sampling
event.
There is a group of 4 fields for each parameter and measurement group included in the
merge file.
Field ##+1: [TRACE GAS NAME] Gas identifier (e.g., co2, co2c13).
Field ##+2: [MEASUREMENT GROUP] Identifies the group within NOAA and
INSTAAR making the actual measurement (e.g., ccgg, hats, arl).
See Section 5 (UPDATE NOTES) for details.
Field ##+3: [MEASURED VALUE] Dry air mole fraction or isotopic composition.
Missing values are denoted by -999.99[9].
Field ##+4: [QC FLAG] A three-character field indicating the results of our
data rejection and selection process, described in section 7.5.
Fields in each line are delimited by whitespace.
(ex)
LEF 2006 10 10 19 01 18 3013-09 A 45.9451 -90.2732 715.98 224059 co2 CCGG 381.690 ...
ch4 CCGG 1842.720 ... co CCGG 108.320 ...
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7.5 QC FLAGS
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 determined.
14CO2 measurements are typically obtained by combining the
air from two flasks collected within about 5 minutes of another.
However, a 14CO2 result is reported for every flask measured,
such that the same delta-14CO2 value is often repeated in the
"event" results file. We include a flag 'M' in the third column
when multiple flasks were combined.
Flag Description
RETAINED ... Retained, no comments.
..M Multiple flasks were combined
to obtain this measurement; retained
..I sample has also been measured
by another lab as part of
an intercomparison experiment
***NOTE: Currently (as of Nov, 2011) no 'Selection' flags are included
******* for surface PFP samples
SELECTED .F. automatically flagged as
non-background
.Z. flagged manually as non-background
REJECTED C.. rejected due to error in CO2
mole fraction analysis
A.. rejected due to
error in CO2C14 analysis
T.. sample collected as
part of a methods
test; not used in
data analysis
The retained values comprise the data set that we feel
best represents the 14CO2 distribution in the remote,
well-mixed global troposphere. These are the values
we use to calculate long-term trends and interannual
and seasonal variations in our studies of the global
carbon cycle. It is possible, and even likely, that
the values flagged as not representative of
background conditions are valid measurements, but
represent poorly mixed air masses influenced by local
or regional anthropogenic sources or strong local
biospheric sources or sinks. Users of these data
should be aware that data selection is a difficult
but necessary aspect of the analysis and interpretation
of atmospheric trace gas data sets, and the specific
data selection scheme used may be determined by the
goals of a particular investigation.
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8. DATA RETRIEVAL
To transfer all files in a directory, it is more efficient to
download the tar or zipped files.
To transfer a tar file, use the following steps from the ftp prompt:
1. ftp> binary ! set transfer mode to binary
2. ftp> get filename.tar.gz ! transfer the file
3. ftp> bye ! leave ftp
4. $ gunzip filename.tar.gz ! unzip your local copy
5. $ tar xvf filename.tar ! unpack the file
To transfer a zipped file, use the following steps from the ftp prompt:
1. ftp> binary ! set transfer mode to binary
2. ftp> get filename.zip ! transfer the file
3. ftp> bye ! leave ftp
4. $ unzip filename.zip ! uncompress your local copy
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9. REFERENCES
Donahue, D. J., Linick, T., and Jull, A. T.: Isotope-ratio
and background corrections for accelerator mass spectrometry
radiocarbon measurements, Radiocarbon, 32, 135-142, 1990.
Lehman, S. J., Miller, J. B., Wolak, C., Southon, J., Tans, P. P.,
Monzka, S. A., Sweeney, C., Andrews, A., LaFranchi, B.,
Guilderson, T. P., and Turnbull, J. C.: Allocation of Terrestrial
Carbon Sources Using 14CO2: Methods, Measurement, and Modeling,
Radiocarbon, 2013.
Miller, J. B., Lehman, S. J., Montzka, S. A., Sweeney, C.,
Miller, B. R., Karion, A., Wolak, C., Dlugokencky, E. J.,
Southon, J., Turnbull, J. C., and Tans, P. P.: Linking emissions
of fossil fuel CO2 and other anthropogenic trace gases using
atmospheric (CO2)-C-14, J. Geophys. Res., 117, D08302
10.1029/2011jd017048, 2012.
Stuiver, M., and Polach, H. A.: Discussion: Reporting of
14C data, Radiocarbon, 19, 355-363, 1977.
Turnbull, J. C., Miller, J. B., Lehman, S. J., Tans, P. P.,
Sparks, R. J., and Southon, J. R.: Comparison of 14CO2, CO
and SF6 as tracers for determination of recently added fossil
fuel CO2 in the atmosphere and implications for biological
CO2 exchange, Geophysical Research Letters, 33, L01817, 2006.
Turnbull, J. C., Lehman, S. J., Miller, J. B., Sparks, R. J.,
Southon, J. R., and Tans, P. P.: A new high precision 14CO2
time series for North American continental air, Journal of
Geophysical Research, 112, D11310, doi:10.1029/2006JD008184,
2007.
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