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Atmospheric Halocarbons Dry Air Mole Fractions from the
NOAA ESRL GMD Carbon Cycle Aircraft Network
Version: 2012-09-26
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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
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.gov
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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
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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
+++++++++++++++++++++++++++++++
Lab-wide notes:
2011-10-07
We have introduced the term "measurement group", which identifies
the group within NOAA and INSTAAR that made the actual measurement.
We can now have multiple groups measuring some of the same trace
gas species in our discrete samples.
Measurement groups within NOAA and INSTAAR are
ccgg: NOAA Carbon Cycle Greenhouse Gases (CCGG)
hats: NOAA Halocarbons and other Atmospheric Trace Gases (HATS)
arl: INSTAAR Atmospheric Research Laboratory (ARL)
sil: INSTAAR Stable Isotope Laboratory (SIL)
curl: INSTAAR Laboratory for Radiocarbon Preparation and Research (CURL)
We have also changed the file naming convention (see section "DATA - FILE
NAME DESCRIPTION").
+++++++++++++++++++++++++++++++
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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6. INTRODUCTION
In the early 1990's the NOAA GMD Carbon Cycle Greenhouse Gases (CCGG)
Group began a long term aircraft project to determine the vertical
distributions of CO2, CH4, and CO in the troposphere. For more detail,
please visit
http://www.cmdl.noaa.gov/ccgg/aircraft.html.
Whole air samples have been collected from small chartered aircraft in
glass flasks above Briggsdale, Colorado since 1992 (Tans et al., 1996).
Other aircraft programs were begun near Moscow, Russia in 1995 and near
Howland, Maine in late 1996. These programs experienced significant
equipment damage and were discontinued in 1997. These data
are not included because the records are short and incomplete.
As part of the NASA Earth Observing System/AM-1 satellite (renamed
TERRA) CCGG was funded to provide correlative data to be used in the
validation of the Measurement Of Pollution In The Troposphere
instrument (MOPITT). For more information, visit the MOPITT site at
http://www.atmosp.physics.utoronto.ca/MOPITT/overview.html.
Four new profiling sites from the Arctic to the South Pacific were
developed for the MOPITT program, and the aircraft profiles were
scheduled to coincide with the descending 10:30 AM TERRA overpass.
The first NOAA/MOPITT flights were flown in 1999, prior to the March
2000 launch of TERRA. For more detail, see
http://www.cmdl.noaa.gov/ccgg/mopitt/mopitt.html.
Additional profiling sites have been developed.
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).
Estimates of the uncertainty associated with each GCMS measurement are
not yet available. It is expected that this will be included in future
updates.
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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 weekly or biweekly for most sites.
The air samples are collected using an automated Programmable Flask
Package (PFP) operated on a small aircraft. Air samples are collected
at several altitudes during a single flight resulting in a vertical
distribution (profile) for each trace gas measured.
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7.1 DATA - SAMPLING LOCATIONS
Table of NOAA GMD aircraft sampling sites (ccg_aircraft).
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 number of profiles;
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.
To view near real-time data, manipulate and compare data, and create
custom graphs, please visit
http://www.esrl.noaa.gov/gmd/dv/iadv/.
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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/globalview/gv_labs.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 are 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/gcms/aircraft/event/" use the following naming
scheme (see Section 7.2):
[parameter]_[site]_[project]_[lab ID number]_[measurement group]_[optional qualifiers].txt
(ex) co2_cma_aircraft-pfp_1_ccgg.txt contains CO2 ccgg measurement
results for all aircraft PFP samples collected at Cape May, New Jersey.
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)
CMA 2010 03 07 14 00 40 3072-01 A co2 CCGG 391.260 -999.990 ... L10 2010 03 13 06 57 00 38.8904 -74.3505 7629.75 292646
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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_cma_aircraft_pfp_ccgg.txt contains ccgg measurement results for two or
more parameters for all aircraft PFP samples collected at Cape May, New Jersey.
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)
CMA 2005 08 17 16 47 00 3008-09 A 38.8300 -74.3100 1584.04 204583 co2 CCGG 371.950 ... ch4 CCGG 1844.350 ...
co CCGG 128.010 ...
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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.
Flag Description
RETAINED ... (3 periods) Good sampling and analysis.
..0 (3rd column zero) Preliminary data awaiting QC
SELECTED .A. Suspected analysis issue that may affect data quality,
although the affect may not be readily evident. Use with caution.
.N. suspected sampling issue that may affect data quality,
although the affect may not be apparent. Use with caution.
REJECTED A.. Known analysis issue that has compromised data quality.
Do not use these data!
N.. Known sampling issue that has compromised data quality.
Do not use these data
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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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