Atmospheric Dry Air Mole Fractions of c2h2 from the NOAA GML Surface 
and Aircraft Vertical Profile Network.

Version: 2023-05-16

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 - File Types
7.4      DATA - Content
7.5      DATA - QC Flags
7.6      DATA - Collection Methods
8.       Data retrieval
9.       References


National Oceanic and Atmospheric Administration (NOAA)
Earth System Research Laboratories (ESRL)
Global Monitoring Laboratory (GML)
Halocarbons & other Atmospheric Trace Species Group (HATS)

Correspondence concerning these data should be directed to:

Isaac Vimont and Stephen Montzka
NOAA ESRL Global Monitoring Laboratory
325 Broadway, MS: R/GML1
Boulder, CO  80305

email:    isaac.vimont@noaa.gov


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
ensure that GML receives fair credit for their work.  If the data 
are obtained for potential use in a publication or presentation, 
GML should be informed at the outset of the nature of this work.  
If the GML data are essential to the work, or if an important 
result or conclusion depends on the GML data, co-authorship
may be appropriate.  This should be discussed at an early stage in
the work.  Manuscripts using the GML data should be sent to GML
for review before they are submitted for publication so we can
ensure that the quality and limitations of the data are accurately


Please reference these data as

   Vimont, I., Montzka, S., Crotwell, M., Andrews, A., Baier, B., Hall, B.,
   Handley, P., Higgs, J., Kofler, J., Legard, T., McKain, K., Miller, J., Moglia,
   E., Mund, J., Neff, D., Newberger, T., Petron, G., Sweeney, C., Turnbull, J., Wolter, S.,
   & NOAA Global Monitoring Laboratory. (2022). Atmospheric Dry Air Mole Fractions of 
   c2h2 from the NOAA GML Surface and Aircraft Vertical Profile Network. 
   [Data set]. NOAA GML. Version 2023-05-16. https://doi.org/10.15138/j91s-4223


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 GML data, namely well documented model code, transport
fields, modeled mole fractions, 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.


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:


Datasets are provided in the self describing ObsPack format.
See https://gml.noaa.gov/ccgg/obspack/ for details.
Aircraft pfp event data are available in NetCDF and ASCII text.


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 analyte specific 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


    GCMS analyses involve extraction of approximately 150-400 cc(STP) of the
whole air sample through two cryogenic preconcentration traps, subsequent
thermal desorption onto a capillary precolumn and then a capillary main
column before final detection of the mass/charge ration specific to each
analyte (Montzka et al., 1993).  Sample volumes vary based on the number of
additional measurements to be performed on each sample subsequent to the GCMS
extraction.  To account for the variable sample volumes, the GCMS analysis
system is routinely checked for non-linearities and non-linearity corrections
are made where necessary.  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 specified
compound specific scale.  Reproducibility varies by compound but are
typically less than 5% RSD, with better reproducibility for the higher
abundance compounds.

    Air samples are collected in programmable flask packages (PFP) using
programmable compressor packages (PCP). The PCP contains battery-powered
pumps for flushing and pressuring the flasks. The PFP contains twelve 0.7L
cylindrical borosilicate glass flasks with glass valves on each end sealed
with Teflon O-rings, a stainless-steel manifold on each side of the flasks,
and a data logging and control system. 


For a summary of sampling locations, please visit:

or https://gml.noaa.gov/ccgg/aircraft/.

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:



Encoded into each file name are the parameter (trace gas identifier); sampling 
site; sampling project; laboratory ID number; measurement group (optional); and optional 
qualifiers that further define the file contents.

All file names use the following naming scheme:

         1      2         3               4                   5            
[parameter]_[site]_[project]_[lab ID number]_[optional measurement group]_[optional 

         6           7
qualifiers].[file type]

1. [parameter]

   Identifies the measured parameter or trace gas species.

   co2      Carbon dioxide
   ch4      Methane
   co2c13   d13C (co2)
   merge    more than one parameter

2. [site]

   Identifies the sampling site code.


3. [project]
   Identifies sampling platform and strategy.


4. [lab ID number]

   A numeric field that identifies the sampling laboratory (1,2,3, ...).
   NOAA GML is lab number 1 (see https://gml.noaa.gov/ccgg/obspack/labinfo.html).

5. [optional measurement group]

  Identifies the group within the NOAA GML or the Institute of Arctic and Alpine
  Research (INSTAAR) at the University of Colorado Boulder that made the
  It is possible to have multiple different 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 group (CCGG)
  hats:  NOAA Halocarbons and other Atmospheric Trace Species group (HATS)
  arl:   INSTAAR Atmospheric Research Laboratory (ARL)
  sil:   INSTAAR Stable Isotope Laboratory (SIL)
  curl:  INSTAAR Laboratory for Radiocarbon Preparation and Research (CURL)

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.

   event         All measurement results for all collected samples (discrete (flask) data only).
   month         Computed monthly averages all collected samples (discrete (flask) data only).
   hour_####     Computed hourly averages for the specified 4-digit year (quasi-continuous data only)
   HourlyData    Computed hourly averages for entire record (quasi-continuous data only)
   DailyData     Computed daily averages for entire record (quasi-continuous data only)
   MonthlyData   Computed monthly averages for entire record (quasi-continuous data only)

7. [file type]
   File format (netCDF, ASCII text). 


   txt           ASCII text file
   nc            netCDF4 file


We now provide some NOAA Global Monitoring Laboratory measurements
in two unique file formats; netCDF and ASCII text. 

The Network Common Data Form (NetCDF) is a self-describing, machine-independent
data format that supports creation, access, and sharing of array-oriented
scientific data.  To learn more about netCDF and how to read netCDF
files, please visit http://www.unidata.ucar.edu. 

The ASCII text (technically UTF-8 encoded) file is derived directly from the 
netCDF file.  The text file is also self-describing and can be viewed using 
any ASCII or UTF-8 capable text editor.  "Self-describing" means the file 
includes enough information about the included data (called metadata) 
that no additional file is required to understand the structure of the data 
and how to read and use the data.  Note that some non-ASCII characters (accents,
international character sets) may be present in various names and contact 
information.  These may require a UTF-8 capable text editor to view properly.


See individual files for description of the provided variables and other 
dataset metadata.


NOAA GML 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

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 assessed.

NOTE: For this data set, preliminary selection
    flags have been added to denote if a data point
    is above or below the general “background” for a
    given site.  At this time, these selection flags
    are still being developed, and as such, a given
    datapoint’s flag status is subject to change in
    future releases, once the statistical methods are
    perfected and deemed appropriate for this use.
    Data points with this flag should be considered
    valid at this time, and the end user is encouraged
    to evaluate which data (with the selection flag) are
    appropriate for their individual use.


A single-character code is used to identify the sample collection method.
The codes are:
    A - The automated or manual filling of a whole air sample using the
Programmable Flask Package (PFP) and Programmable Compressor Package (PCP)air
sampling devices. The air sample is contained in a 0.7 liter borosilicate
glass container (flask) fitted with two Glass Expansion high vacuum glass
piston valves sealed with PTFE O-rings. The flasks are typically flushed with
10 liters (aircraft samples) or 75 liters (tower samples) of ambient air and
then pressurized to 40 psia. Air is delivered through an intake tube using
two diaphragm pumps connected in series and controlled with a microprocessor.
The flow rate is approximately 15 L/min at sea level.  See Sweeney et al.
2015 and Andrews et al. 2014 for more details.
    C - Air samples are collected as with method ‘A’, but the sample air is
dried before sample collection. Flasks are not pre-filled with ambient air
before flushing and collecting  the air sample.
    R - Air samples are collected as with method 'A', but with an additional
glass conditioning step known as “prefilling”. During prefilling,  the glass
containers are flushed and filled with ambient air and then vented and
flushed immediately before air sample collection. This is a glass
conditioning step that addresses glass wall effects of the gasses of interest
(Andrews et al. 2014).
    B - Air samples are collected as with method ‘R’, but with an additional
drying step  using one of several techniques. In one method, e.g. site=ACT,
air samples were dried with a two-stage chiller cooled to 5 degrees C; those
taken below 3000 m MSL were also pressurized to 40 psia to further facilitate
air sample drying (Baier et al. 2019). At tower sampling sites, M&C chillers
with temperatures set to approximately 3 degrees C and sub-ambient pressure
due to high flow are used (Andrew et al. 2014). At CRV tower, a two-stage
chiller set to -26 degrees C is used. 


All (ASCII text and netCDF) files are located in 

To transfer all files in a directory, it is more efficient to 
download the tar or zipped files. Individual or zipped files can
be downloaded using your web browser by clicking the hyperlinked file
or right clicking hyperlink and using browser menu to 'save as' or similar.

Files can also be accessed by anonymous ftp at aftp.cmdl.noaa.gov.