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Atmospheric Halocarbons Dry Air Mole Fractions from the
NOAA ESRL GMD Carbon Cycle Surface Network
Version: 2011-03-17
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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
7.4 DATA - QC Flags
8. Data retrieval
9. References
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1. DATA SOURCE AND CONTACTS
National Oceanic and Atmospheric Administration (NOAA)
Earth System Research Laboratory (ESRL)
Global Monitoring Division (GMD)
Halocarbons & other Atmospheric Trace Species Group (HATS)
Correspondence concerning these data should be directed to:
Stephen Montzka and Ben Miller
NOAA ESRL Global Monitoring Division
325 Broadway, MS: R/GMD1
Boulder, CO 80305
U.S.A.
email: steve.montzka@noaa.gov
ben.r.miller@noaa.go
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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
assure 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
Montzka, S. A., Miller, B. R., (2010)
Atmospheric Halocarbon Dry Air Mole Fractions from the NOAA ESRL
Surface Network using Programmable Flask Packages
(PFP), 1992-2010, Version: 2011-03-17.
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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
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.
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5. UPDATE NOTES
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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.
All samples were analyzed for GCMS analytes (mostly halocarbons) at
NOAA ESRL in Boulder, Colorado by gas chromatography / mass spectrometric
detection, and each sample aliquot was referenced to the NOAA standard
scale (see Hall et al. 2007).
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7. DATA - GENERAL COMMENTS
GCMS analyses involve cryogenic preconcentration of analytes
from approximately 150 cc (STP) of sample gas, followed by
thermal desorption onto a short capillary precolumn and main capillary
column (Gaspro) for separation, and finally detection of each mass/charge
ratio specific to each analyte (Montzka et al., 1993). Analyses of
PFP air samples are compared to analyses of known (calibrated) compressed
air standards. Analytical results are expressed as dry gas mole fractions
(pmol/mol or ppt) on the NOAA scale. Reproducibility varies
by compound but are typically less than 5% RSD, with better
reproducibility for the higher abundance compounds.
Sampling frequencies are approximately daily.
The air samples are collected using an automated Programmable Flask
Package (PFP).
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 sampling location, platform, and
strategy; measurement laboratory; file content; and gas identifier.
All file names use the following naming scheme:
1 2 3 4 5 6 7
[site][data grouping]_[lab#][strategy][platform]_[qualifier].[gas]
1. [Sampling site]
(ex) brw_, poc_, car_, amt_
2. [Grouping of data within the file]
Data may be grouped by date, latitude, longitude, altitude, etc.
If data are grouped by date then identifier has yyyy[mm][dd] format.
(ex) brw2005_, amt200403_, lef20050315_
If the sampling platform is an aircraft then the identifier is a
3-character numeric field with units of 10^2 meters (hm) above sea level.
(ex) car040_, haa005_
If the sampling platform is a ship then the identifier is a 3-character
alphanumeric field with units of degrees (00-90). Bins in the northern
and southern hemispheres are denoted as n## and s## respectively. The
equatorial bin is denoted as 000.
(ex) pocs25_, poc000_, scsn03_
3. [Measurement laboratory]
A two character numeric field identifies the measurement laboratory (01-99).
NOAA ESRL is lab number 01 (see https://om.cmdl.noaa.gov/globalview/labs/).
4. [Sampling strategy]
A single alphanumeric character (0-9,a-z,A-Z) indicates the sampling strategy.
_??C Semi-continuous
_??D Discrete using Portable Sampling Unit (PSU)
_??P Discrete using Programmable Flask Package (PFP)
5. [Sampling platform]
A single alphanumeric character (0-9,a-z,A-Z) indicates the sampling platform.
_???0 Land
_???1 Ship
_???2 Aircraft
_???3 Tower
6. [Qualifier]
An alphanumeric string describes the type of data included in the file.
_????_event Data from every collection event
_????_mm Computed monthly mean values
_????_hr Computed hourly averages (semi-continuous data only)
_????_day Computed daily averages (semi-continuous data only)
_????_all All Data
7. [Gas]
Identifies the trace gas species.
_????_???.co2 Carbon dioxide
_????_???.ch4 Methane
_????_???.co2c13 d13C (co2)
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7.3 DATA - EVENT
The data files in "ccg/gcms/event/" use the following naming
scheme (see Section 7.2):
xxx_01P0_event.gcms
(ex) lef_01P0_event.gcms contains LEF gcms surface data
The data files contain multiple lines of header information
followed by one line for each atmospheric measurement.
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: [FLASK ID] The sample container ID.
Field 8: [METHOD] A single-character code that identifies the sample
collection method. The codes are:
A - Sample collected using a Programmable Flask Package (PFP).
Field 9: [TRACE GAS NAME] Gas identifier (e.g., co2, co2c13).
Field 10: [MEASURED VALUE] Dry air mole fraction or isotopic composition.
Missing values are denoted by -999.99[9].
Field 11: [ESTIMATED UNCERTAINTY] Estimated uncertainty of the reported
measurement value. Missing values are denoted by -999.99[9].
Field 12: [QC FLAG] A three-character field indicating the results of our
data rejection and selection process, described in section 7.4.
Field 13: [INSTRUMENT] A 2-character code that identifies the instrument
used for the measurement.
Field 14: [YEAR] The measurement date and time in LT.
Field 15: [MONTH]
Field 16: [DAY]
Field 17: [HOUR]
Field 18: [MINUTE]
Field 19: [LATITUDE] The latitude where the sample was collected, (negative (-)
numbers indicate samples collected in the southern hemipshere).
Field 20: [LONGITUDE] The longitude where the sample was collected, (negative (-)
numbers indicate samples collected in the western hemisphere).
Field 21: [ALTITUDE] The altitude where the sample was collected (masl).
Field 22: [EVENT NUMBER] A long integer that uniquely identifies the sampling
event.
Fields in each line are delimited by whitespace.
(ex)
WKT 2010 08 10 20 31 3083-12 A co2 387.940 -999.990 ..P L8 2010 08 19 03 07 31.3200 -97.3300 708.05 302117
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7.4 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 COMMENT 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.
If both the first and second column contain a period (e.g., "..." and "..I"),
the sample is RETAINED.
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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
Hall, B. D., G. S. Dutton, and J. W. Elkins (2007), The
NOAA nitrous oxide standard scale for atmospheric observations,
J. Geophys. Res., 112, D09305, doi:10.1029/2006JD007954.
Montzka, S. A., R. C. Myers, J. H. Butler, J.W. Elkins, and
S.O. Cummings (1993), Global tropospheric distribution and
calibration scale of HCFC-22, Geophys. Res. Lett., 20, 703-706.
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