--------------------------------------------------------------------- Atmospheric Dry Air Mole Fractions of hfc125 from the NOAA GML Surface and Aircraft Vertical Profile Network. Version: 2023-05-16 -------------------------------------------------------------------- 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 - File Types 7.4 DATA - Content 7.5 DATA - QC Flags 7.6 DATA - Collection Methods 8. Data retrieval 9. References -------------------------------------------------------------------- 1. DATA SOURCE AND CONTACTS 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 U.S.A. email: isaac.vimont@noaa.gov steve.montzka@noaa.gov -------------------------------------------------------------------- 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 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 represented. 2.1 CITATION 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 hfc125 from the NOAA GML Surface and Aircraft Vertical Profile Network. [Data set]. NOAA GML. Version 2023-05-16. https://doi.org/10.15138/y6xe-ms92 -------------------------------------------------------------------- 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 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. -------------------------------------------------------------------- 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. -------------------------------------------------------------------- 5. UPDATE NOTES +++++++++++++++++++++++++++++++ Lab-wide notes: 2011-10-07 We introduced the term "measurement group", which identifies the group within NOAA or Institute of Arctic and Alpine Research (INSTAAR) University of Colorado Boulder that made the 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 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) +++++++++++++++++++++++++++++++ Project-specific notes: 2022-11-01 Datasets are provided in the self describing ObsPack format. See https://gml.noaa.gov/ccgg/obspack/ for details. Surface pfp event data are available in NetCDF and ASCII text. +++++++++++++++++++++++++++++++ Parameter-specific notes: -------------------------------------------------------------------- 6. INTRODUCTION 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 updates. ------------------------------------------------------------------- 7. DATA - GENERAL COMMENTS 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. 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. ------------------------------------------------------------------- 7.1 DATA - SAMPLING LOCATIONS For a summary of sampling locations, please visit https://gml.noaa.gov/dv/site/?program=ccgg. 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 https://gml.noaa.gov/dv/iadv/. ------------------------------------------------------------------- 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 (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. (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 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 measurement. 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. (ex) 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). (ex) txt ASCII text file nc netCDF4 file ------------------------------------------------------------------- 7.3 DATA - FILE TYPES 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. ------------------------------------------------------------------- 7.4 DATA - CONTENT See individual files for description of the provided variables and other dataset metadata. ------------------------------------------------------------------- 7.5 QC FLAGS 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 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 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. ------------------------------------------------------------------- 7.6 COLLECTION METHODS 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. 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. 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. I - Air is sampled from a 15L spherical stainless steel mixing volume after being filled with ambient air that was pulled through an M&C Techgroup Model ECP 20-2 gas chiller using an integrating compressor and mass flow controller. The two stainless steel dryer traps are plumbed in series, held at approximately 5 degrees C and the condensed water is removed with a peristaltic pump. The integration starts with a high flow rate of 3.8 SLM and decreases over time to 0.29 SLM over 1 hour. The resulting one hour time averaged ambient air sample is compressed into a 0.75 liter borosilicate glass container (flask) fitted with 2 Glass Expansion high vacuum glass valves and PTFE O-rings. The flask is typically filled to 40 psia. (See Turnbull, J.C., Guenther, D., Karion, A., Sweeney, C., Anderson, E., Andrews, A.E., Kofler, J., Miles, N.L., Newberger, T., Richardson, S.J., Tans, P.P., 2012. An integrated flask sample collection system for greenhouse gas measurements. Atmos. Meas. Tech. 5, 2321-2327.) 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). ------------------------------------------------------------------- 8. DATA RETRIEVAL All (ASCII text and netCDF) files are located in "https://gml.noaa.gov/aftp/data/trace_gases/gcms/pfp/surface/". 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. ------------------------------------------------------------------- 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. -------------------------------------------------------------------