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Atmospheric Carbon Dioxide Dry Air Mole Fractions from 
quasi-continuous measurements at Barrow, Alaska; Mauna 
Loa, Hawaii; American Samoa; and South Pole, 1973-2009

National Oceanic and Atmospheric Administration (NOAA)
Earth System Research Laboratory (ESRL)
Global Monitoring Division (GMD)
Carbon Cycle Greenhouse Gases (CCGG)

Version: 2010-07-14
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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 - Hourly Averages
7.4      DATA - QC Flags
7.5      DATA - Daily Averages
7.6      DATA - Monthly Averages
8.       Data retrieval
9.       References

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1. DATA SOURCE AND CONTACTS

These directories contain atmospheric Carbon Dioxide (CO2)
Dry Air Mole Fractions from quasi-continuous measurements 
at Barrow, Alaska (BRW); Mauna Loa, Hawaii (MLO); American 
Samoa (SMO); and South Pole (SPO), 1973-2009.

Correspondence concerning these data should be directed to:

Dr. Pieter Tans
NOAA ESRL Global Monitoring Division
325 Broadway, GMD-1
Boulder, Colorado, 80305 USA
Telephone: 303 497-6678
Electronic Mail: pieter.tans@noaa.gov

Kirk W. Thoning (kirk.w.thoning@noaa.gov)
NOAA ESRL GMD

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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

   Thoning, K.W., D.R. Kitzis, and A. Crotwell (2010), Atmospheric 
   Carbon Dioxide Dry Air Mole Fractions from quasi-continuous 
   measurements at Barrow, Alaska; Mauna Loa, Hawaii; American
   Samoa; and South Pole, 1973-2009, Version: 2010-07-14, 
   Path: ftp://ftp.cmdl.noaa.gov/ccg/co2/in-situ/.

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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

Please read the 'Update_notes' file for information
regarding problems and changes to the data sets.

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6. INTRODUCTION


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7. DATA - GENERAL COMMENTS


7.1 DATA - SAMPLING LOCATIONS


Carbon Cycle In Situ Observatory (ccg_obs).

The table includes the three letter code used to identify each
site; the site name; latitude, longitude, and elevation (meters
above sea level) of the sampling location; and country.

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 - HOURLY AVERAGES

Data files are located in "/ccg/co2/in-situ/[site]/".  The hourly averaged
data are grouped by year (e.g., mlo1998_01C0_hr.co2).  Each hourly average
is computed from individual measurements (typically 4 per hour).

The data files in "ccg/co2/in-situ/[site]/" use the following naming
scheme (see Section 7.2):

     xxx[grouping]_01C0_[qualifier].co2

(ex) mlo1998_01C0_hr.co2 contains Mauna Loa co2 hourly averages 
     for 1998.

(ex) brw_01C0_day.co2 contains co2 daily averages from Barrow.

The data files contain multiple lines of header information
followed by one line for each computed average.

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:    [MEAN VALUE] Dry air mole fraction.
             Missing values are denoted by -999.99[9].

Field 7:    [STANDARD DEVIATION]  Standard deviation of mean value (1 sigma).

Field 8:    [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)

   MLO 1999 01 12 08 1909.60 2.81 .C.

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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.

SUMMARY OF SELECTION FLAGS

Missing data will have a value of -999.99 for the mixing ratio.
Times are specified in Greenwich Mean Time. Hours are specified
as the beginning of the hour, for example, hour 5 corresponds to
5 AM to 6 AM GMT.

The selection process is done to distinguish "background" mixing
ratios, that is, the values that we believe are not contaminated
by local sources or sinks of CO2.  The selection process depends
on the station (see references).  There are a large number of
possible codes, but the most common codes are:

   ... - No code applied. Data are considered 'background'.
   C.. - Weekly calibration of reference gases, no data available
   I.. - Instrument malfunction, no data available
   .V. - Large variability of CO2 mixing ratio within one hour
   .D. - Hour-to-hour difference in mixing ratio > 0.25 ppm
   .A. - Automatic selection based on residuals from a spline curve
   .U. - Rejected, diurnal variation (upslope) in CO2 (Mauna Loa only)

Other codes may be used, but the main point is that missing data
will have a value of -999.99 for the hour, and "background" values
will be designated by a lack of a code.  See also the 'Update_notes'
file for information regarding other codes.

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7.5 DATA - DAILY AVERAGES

Data files are located in "/ccg/co2/in-situ/[site]/".  There is one
daily mean data file for each site (e.g., brw_01C0_day.co2).  The
file contains one row for each day in the reporting period. Daily
means are calculated from background (QC Flag is '...') hourly
averages.  Days for which only one hourly value is used to
determine the average are assigned a default (-9.99) standard
deviation. 

The data files contain multiple lines of header information 
followed by one line for each day.

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:    [MEAN VALUE] Dry air mole fraction.
             Missing values are denoted by -999.99[9].

Field 6:    [STANDARD DEVIATION]  Standard deviation of mean value (1 sigma),

Field 7:    [# OF HOURS] The number of hourly averages used to calculate
             the daily mean.

Fields in each line are delimited by whitespace.

(ex)

   BRW 2000  2 22  1890.48    4.471   11 

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7.6 DATA - MONTHLY AVERAGES

Data files are located in "/ccg/co2/in-situ/[site]/".  There is one
monthly mean data file for each site, (e.g., mlo_01C0_mm.co2).
Monthly means are calculated from the daily averages.

The data files contain multiple lines of header information followed
by one line for each available month.

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:    [MEAN VALUE] Dry air mole fraction.
             Missing values are denoted by -999.99[9].

Field 5:    [STANDARD DEVIATION]  The standard deviation is of the mean 
             value (1 sigma).

Field 6:    [# OF DAYS] The number of daily averages available.

Fields in each line are delimited by whitespace.

(ex)

   BRW 2006  6   385.85  2.42 28

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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

Peterson, J.T., W.D. Komhyr, L.S. Waterman, R.H. Gammon, K.W.
   Thoning, and  T.J. Conway, Atmospheric CO2 variations at Barrow,
   Alaska, 1973-1982,  J. Atmos. Chem., 4, 491-510, 1986.

Herbert, G.A., E.R. Green, J.M. Harris, G.L. Koenig, S.J. Roughton,
   and K.W. Thaut, Control and monitoring instrumentation for the
   continuous measurement of atmospheric CO2 and meteorological
   variables, J. Atmos. Oceanic Technol., 3, 414-421, 1986.

Gillette, D.A., W.D. Komhyr, L.S. Waterman, L.P. Steele, and R.H.
   Gammon, The NOAA/GMCC continuous CO2 record at the South Pole,
   1975-1982, J. Geophys. Res., 92, 4231-4240, 1987.

Halter, B.C., Harris, J.M., and Conway, T.J., Component signals in
   the record of atmospheric carbon dioxide concentation at
   American Samoa, J. Geophys. Res., 93, 15914-15918, 1988.

Komhyr, W.D., T.B. Harris, L.S. Waterman, J.F.S. Chin, and K.W.
   Thoning,  Atmospheric carbon dioxide at Mauna Loa Observatory: 1.
   NOAA Global Monitoring for Climatic Change measurements with a
   nondispersive infrared analyzer, 1974-1985, J. Geophys. Res.,
   94, 8533-8547, 1989.

Thoning, K.W., P.P. Tans, and W.D. Komhyr, Atmospheric carbon
   dioxide at Mauna Loa Observatory, 2. Analysis of the NOAA/GMCC
   data, 1974-1985., J. Geophys. Res. ,94, 8549-8565, 1989.

Thoning, K.W. Selection of NOAA/GMCC CO2 data from Mauna Loa
   Observatory, In The Statistical Treatment of CO2 Data
   Records, NOAA Tech. Mem. (ERL-ARL-173), Environ. Res. Lab.,
   131 pp., 1989

Waterman, L.S., D. W. Nelson, W.D. Komhyr, T.B. Harris, and K.W.
   Thoning,  Atmospheric carbon dioxide measurements at Cape
   Matatula, American Samoa, 1976-1984., J. Geophys. Res. , 94,
   14817-14829, 1989.

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