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Atmospheric Carbon Monoxide Mixing Ratios from the
NOAA GMD Tower Network, 2003 - 2009 04

Version: 2011-08-31
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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 - All
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)
Carbon Cycle Greenhouse Gases (CCGG)

Correspondence concerning these data should be directed to:

Dr. Arlyn E. Andrews
NOAA ESRL Global Monitoring Division
325 Broadway, GMD-1
Boulder, CO 80305
U.S.A.

email: Arlyn.Andrews@noaa.gov

The collection and analysis of data available from the NOAA ESRL
data archive is greatly enabled by collaborating institutions.
Collaborators are identified in the header of each data file.

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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

Andrews, A.E., J. Kofler, P.S. Bakwin, C. Zhao, P. Tans (2009),
Carbon Dioxide and Carbon Monoxide Dry Air Mole Fractions from
the NOAA ESRL Tall Tower Network, 1992-2009, Version: 2011-08-31,
Path: ftp://ftp.cmdl.noaa.gov/ccg/towers/.

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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

CO Dry Air Mole Fraction: The CO abundance is given
as a mole fraction with units of parts per billion (ppb).
This value corresponds to the number of CO molecules per
1 billion molecules of dry air. Each data point represents
a 120 sec average of data collected at 0.2 Hz.

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7. DATA - GENERAL COMMENTS

Uncertainty Estimates: The Total Uncertainty
Estimate attempts to account for known quantifiable
errors in the CO measurements. Total Uncertainty is
comprised of three components: (1) Atmospheric
Variability, AV; (2) Measurement Uncertainty, MU;
(3) Scale Uncertainty, SU; such that TU^2=AV^2+MU^2+SU^2.
Atmospheric Variability is a standard deviation that
represents real natural variability of the species'
abundance during the measurement period (30 sec).
Measurement Uncertainty is computed from several
quasi-independent terms, including uncertainty in the
calibration scale, drift in the analyzer baseline and
gain between calibrations, any lack of full equilibration
of air samples or standards, curve fitting errors,
extrapolation error for samples that are outside of the
calibrated range, differences in H2O content of samples
and standards. All measurements are reported relative to
the WMO mole fraction scale. For CO, calibration scale
uncertainty is 1% of the measured value. Sample equilibration
error/atmospheric variability is frequently the largest
contribution to the total uncertainty.

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7.1 DATA - SAMPLING LOCATIONS

NOAA GMD tower 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 number of samples;
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/ccgg/iadv/.

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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 - ALL

The data files in "ccg/tower/site/co/" use the following naming
scheme (see Section 7.2):

xxx[data grouping]_01C3_all.co

(ex) lef200403_01C3_all.co2 contains all LEF co2 data from
2004-03 (March 2004).

(ex) amt200601_01C3_all.aux contains all AMT auxillary data from
2006-01 (January 2006).

The data files contain multiple lines of header information (identified
by a "#" character in the first column) 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: [SECOND]

Field 8: [LATITUDE] The latitude where the sample was collected, (negative (-)
numbers indicate samples collected in the southern hemipshere).

Field 9: [LONGITUDE] The longitude where the sample was collected, (negative (-)
numbers indicate samples collected in the western hemisphere).

Field 10: [ELEVATION] The elevation of the site (masl).

Field 11: [INTAKE HEIGHT] The intake height above ground level (m).

Field 12: [MEASURED VALUE] The dry air mole fraction.
Missing values are denoted by -999.99[9].

Field 13: [TOTAL UNCERTAINTY ESTIMATE] The Total Uncertainty estimate (see
Section 7). Missing values are denoted by -999.99[9].

Field 14: [ATMOSPHERIC VARIABILTY] The Total Uncertainty estimate (see
Section 7). Missing values are denoted by -999.99[9].

Field 15: [MEASUREMENT UNCERTAINTY] The Measurement Uncertainty estimate (see
Section 7). Missing values are denoted by -999.99[9].

Field 16: [SCALE UNCERTAINTY] The Scale Uncertainty estimate (see
Section 7). Missing values are denoted by -999.99[9].

Field 17: [QC FLAG] A three-character field indicating the results of our
data rejection and selection process, described in section 7.4.

Fields in each line are delimited by whitespace.

(ex)

code yr mo dy hr mn sc lat lon elev(masl) ht(magl) value totunc atmvar measunc scaleunc flag
AMT 2009 04 30 23 29 55 45.0300 -68.6800 50.000 12.0 396.811 0.140 0.115 0.039 0.070 ...

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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.

Flag Description

RETAINED ... Normal Operation
..F Flow through Licor 50-95 sccm (normal flow = 100 sccm)
..R Data outside calibrated range

REJECTION F.. Flow through Licor < 50 sccm (normal flow = 100 sccm)
C.. Temporal gap in calibrations precludes reliable calculation.
Z.. Suspect value not identified by standard QC algorithms (manually applied)
L.. Leak suspected.
A.. Other known problem with analyzed value

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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

Tans, P.P. et al., Carbon Cycle (Group Report), Climate Monitoring
and Diagnostics Laboratory, No. 23, Summary Report 1994-1995,
Hoffman, D.J., J.T. Peterson and R.M. Rosson, eds, US Department
of Commerce, Boulder, Colorado, 1996.

Bakwin, P.S., P.P. Tans, D.F. Hurst, C.Zhao, Measurements of Carbon
Dioxide on Very Tall Towers: Results of the NOAA/CMDL Program, Tellus,
Ser. B., 50, 401-415, 1998.

Zhao, C., P.S. Bakwin, and P.P. Tans, A design for unattended monitoring
of trace gases on a tall tower, J. Atmos. Ocean. Tech., 14, 1139-1145, 1997.

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