--------------------------------------------------------------------- Atmospheric Carbon Dioxide Dry Air Mole Fractions from quasi-continuous measurements at Barrow, Alaska; Mauna Loa, Hawaii; American Samoa; and South Pole, 1973-2016 National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) Global Monitoring Division (GMD) Carbon Cycle Greenhouse Gases (CCGG) Version: 2017-08-15 -------------------------------------------------------------------- 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 8. Data retrieval 9. References -------------------------------------------------------------------- 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), 1973-2016. 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 -------------------------------------------------------------------- 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 insure 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 Reference the Mauna Loa, Hawaii (MLO) record as ... NOAA ESRL Global Monitoring Division. 2016, updated annually. Atmospheric Carbon Dioxide Dry Air Mole Fractions from quasi-continuous measurements at Mauna Loa, Hawaii. Compiled by K.W. Thoning, D.R. Kitzis, and A. Crotwell. National Oceanic and Atmospheric Administration (NOAA), Earth System Research Laboratory (ESRL), Global Monitoring Division (GMD): Boulder, Colorado, USA. Version 2017-8 at http://dx.doi.org/10.7289/V54X55RG Reference the Barrow, Alaska (BRW) record as ... NOAA ESRL Global Monitoring Division. 2016, updated annually. Atmospheric Carbon Dioxide Dry Air Mole Fractions from quasi-continuous measurements at Barrow, Alaska. Compiled by K.W. Thoning, D.R. Kitzis, and A. Crotwell. National Oceanic and Atmospheric Administration (NOAA), Earth System Research Laboratory (ESRL), Global Monitoring Division (GMD): Boulder, Colorado, USA. Version 2017-8 at http://dx.doi.org/10.7289/V5RR1W6B Reference the American Samoa (SMO) record as ... NOAA ESRL Global Monitoring Division. 2016, updated annually. Atmospheric Carbon Dioxide Dry Air Mole Fractions from quasi-continuous measurements at American Samoa. Compiled by K.W. Thoning, D.R. Kitzis, and A. Crotwell. National Oceanic and Atmospheric Administration (NOAA), Earth System Research Laboratory (ESRL), Global Monitoring Division (GMD): Boulder, Colorado, USA. Version 2017-8 at http://dx.doi.org/10.7289/V51834DB Reference the South Pole Observatory (SPO) record as ... NOAA ESRL Global Monitoring Division. 2016, updated annually. Atmospheric Carbon Dioxide Dry Air Mole Fractions from quasi-continuous measurements at South Pole. Compiled by K.W. Thoning, D.R. Kitzis, and A. Crotwell. National Oceanic and Atmospheric Administration (NOAA), Earth System Research Laboratory (ESRL), Global Monitoring Division (GMD): Boulder, Colorado, USA. Version 2017-8 at http://dx.doi.org/10.7289/V5WH2MXN -------------------------------------------------------------------- 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. -------------------------------------------------------------------- 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: 2016-08-26 Latitude and longitude were adjusted for 3 sites: ALT Old: 82.4508 -62.5056 205.00 200.00 New: 82.4508 -62.5072 195.00 190.00 TAC Old: 52.5178 1.1389 236.00 56.00 New: 52.5177 1.1386 236.00 56.00 ZEP Old: 78.9067 11.8889 479.00 474.00 New: 78.9067 11.8883 479.00 474.00 Collaborator name corrected for UTA: Old: U.S. National Weather Service [NWS] New: Beth Anderson/NWS Cooperative Observer 2015-08-03 The 3-letter site identification code for Ushuaia, Argentina (TDF) was changed to USH to be consistent with the WMO GAWSIS. 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 Species (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: 2017-01-24 =================================================================== The method used to apply flags to the hourly average data was changed for the years 1973-2014, to agree with the method used for the 2015 and 2016 data. This means that daily and monthly averages for those earlier years may have changed by small amounts for data packages from previous years. Hourly values were not affected by this change, only the flags. See https:/www.esrl.noaa.gov/gmd/ccgg/about/co2_measurements.html for more details. =================================================================== 2011-10-13 Quasi-continuous CO2 dry air mole fractions from 1980 to 2006 have all been recalculated to bring them into the WMO X2007 Mole Fraction Scale (X07). The data since 2007 were already on the X07 scale. WMO X2007 is based on repeated manometric measurements of the NOAA primary standards (Zhao et al. 2006) and comparison of those results to similar measurements made over a period of more than 10 years at Scripps Institution of Oceanography. The difference between the X07 and the previous scales propagated by SIO and NOAA (X83, X87, etc.) is ~0.2 ppm (X07-previous) in the 1980s, decreasing to ~0.1 ppm in the late 1990s, and to 0.0 ppm by 2006. The recalculation of individual measurements was accomplished by first determining the X07 values for the reference gases used to measure the air samples and then using those values with the raw data (NDIR voltages) to recompute mole fractions for each sample. =================================================================== 2003-11-28 Added year 2002 data for all sites. Updated tar.gz files to include new data. =================================================================== 2003-03-13 The hourly average files now have a new format, which includes the standard deviation of the hourly average. See the README for details. Individual text files also now have a .co2 extension on the file name. =================================================================== 2002-11-27 Revised Maunal Loa 2001 data. There was a mistake in the November 2001 data values, resulting in them being ~0.5 ppm to low. =================================================================== 2002-10-01 Added year 2000 data for Barrow, Samoa and South Pole. Added year 2001 data for all sites. =================================================================== 2001-10-10 Added year 2000 data for Mauna Loa. Updated mlo.in-situ.tar.Z files to include new data. =================================================================== 2000-10-05 Added data through 1999 for all sites. Updated tar.Z files to include new data. Updated tar.Z files to include new data. =================================================================== 1999-11-29 Added data through 1998 for all sites. Updated tar.Z files to include new data. =================================================================== 1996-10-04 Changed the archive for the Mauna Loa data. The formats of the Mauna Loa files are different from the other sites. See the README for details. Added Mauna Loa data for 1993, 1994, and 1995. Updated tar.Z files to include new data. =================================================================== 1996-03-04 Changed the archive for all sites. The formats of the files are different from before. See the README for details. Added data for 1993, 1994, and 1995. Updated tar.Z files to include new data. =================================================================== 1994-05-18 Added data for Barrow, 1992. Added data for Mauna Loa, 1992. Added data for Samoa, 1992. Added data for South Pole, 1991. Added data for South Pole, 1992. Changes to this data based on recalibration of reference gases will occur in the future. Updated tar.Z files to include new data. =================================================================== 1992-08-12 Minor corrections to Samoa and Barrow data were made. Samoa: 77-04-09 hour 00 CO2 changed from 300.45 to 999.99 77-04-09 hour 00 Flag changed from SI to I 81-11-20 hour 00 CO2 changed from 861.97 to 999.99 81-11-20 hour 01 CO2 changed from 861.97 to 999.99 82-01-07 hour 19 CO2 changed from 902.43 to 999.99 82-01-07 hour 20 CO2 changed from 902.43 to 999.99 82-01-07 hour 21 CO2 changed from 902.43 to 999.99 82-01-07 hour 22 CO2 changed from 902.43 to 999.99 82-01-07 hour 23 CO2 changed from 902.43 to 999.99 82-01-08 hour 00 CO2 changed from 340.46 to 999.99 82-01-08 hour 01 CO2 changed from 340.11 to 999.99 Barrow: 82-06-20 hour 09 CO2 changed from 99.99 to 999.99 =================================================================== 1992-07-28 Compressed tar files are now available for transfer. There are four files, one for each observatory. Each tar file contains all the files in the directory for that station, and is named sta.in-situ.tar.Z where sta is the three letter station code, 'brw', 'mlo', 'smo', or 'spo'. =================================================================== 1992-07-27 Preliminary data from Mauna Loa for 1991 is now available. Changes to this data based on recalibration of reference gases will occur in the future. =================================================================== 1992-07-27 Corrections to the Samoa data from January 1, 1988 to August 31, 1991 were made due to better determinations of the reference gases used during this period. Files affected were smo88, smo89, smo90, smoday88, smoday89, smoday90, smomm. The data for 1991 were added to the archive. The new files are smo91 and smoday91. Data starting on September 1, 1991 are still subject to revision. =================================================================== 1992-07-22 Preliminary data from Barrow for 1991 is now available. Changes to this data based on recalibration of reference gases will occur in the future. =================================================================== 1992-07-22 The types of flags used are currently under review. Many flags that were seldom used or were redundant in thier meaning will be replaced with more common flags. The goal is to eventually have only 8 base flags total; ' ', C, I, V, D, A, DN, and NC. Any additional flags based on specific selection schemes for each site will be noted in this file. =================================================================== 1992-07-22 The data selection for Barrow is not consistent for the data set. Data starting in 1981 has been given a more rigourous selection than prior to this date, i.e., there are no D or A selection flags before 1981. The data for Samoa from 1976 through 1987 have had an additional selection based on wind direction and wind speed. (See Waterman et al., 1989). A 'WD' code stands for data that has been flagged because the wind direction was not from the clean air sector. A 'WS' speed is for data where the wind speed is below a minimum value. There are no 'A' flags in the data for this time period. -------------------------------------------------------------------- 6. INTRODUCTION ------------------------------------------------------------------- 7. DATA - GENERAL COMMENTS 7.1 DATA - SAMPLING LOCATIONS For a summary of sampling locations, please visit http://www.esrl.noaa.gov/gmd/dv/site/site_table.html. 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/. ------------------------------------------------------------------- 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 [parameter]_[site]_[project]_[lab ID number]_[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 ESRL is lab number 1 (see http://www.esrl.noaa.gov/gmd/ccgg/obspack/labinfo.html). 5. [measurement group] Identifies the group within NOAA or 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 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] We provide some NOAA Global Monitoring Division measurements in two unique file formats (netCDF and ASCII text). (ex) txt ASCII text file nc netCDF4 file ------------------------------------------------------------------- 7.3 DATA - FILE TYPE We now provide some NOAA Global Monitoring Division 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 file is derived directly from the netCDF file. The text file is also self-describing and can be viewed using any 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. ------------------------------------------------------------------- 7.4 DATA - CONTENT For each observatory record we provide an hourly, daily, and monthly average file. Daily averages are derived directly from the hourly data. Monthly averages are derived from the daily averages. Higher resolution data (sub-hourly) are available upon request. All (ASCII text and netCDF) files are located in "ftp://aftp.cmdl.noaa.gov/data/trace_gases/co2/in-situ/surface/[site]/". Files are named as follows (see Section 7.2 for details): co2_[site]_surface-insitu_1_ccgg_HourlyData.[file type] co2_[site]_surface-insitu_1_ccgg_DailyData.[file type] co2_[site]_surface-insitu_1_ccgg_MonthlyData.[filetype] ------------------------------------------------------------------- 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 assessed. SUMMARY OF SELECTION FLAGS Missing data will have a value of -999.99 for the mole fraction. 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" mole fractions, 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). The selection code is a three character code, where the first character indicates missing data or instrumental problems, the second character indicates selection due to non-background criteria. The third character is not used for data selection. The available codes are: ... - No code applied. Data are considered 'background' *.. - Unable to compute a mole fraction or average I.. - No data available due to instrument calibration or malfunction. .V. - Large variability of CO2 mole fraction within one hour .D. - Hour-to-hour difference in mole fraction > 0.25 ppm .U. - Rejected, diurnal variation (upslope) in CO2 (Mauna Loa only) .S. - Single hour bracketed by flagged data. .N. - No unflagged data within +/- 8 hours. Assume non-background. Missing data will have a value of -999.99 for the hour, and "background" values will be designated by a '.' character for the first two characters. See also the 'Update_notes' file for information regarding other codes. ------------------------------------------------------------------- 8. DATA RETRIEVAL Users may transfer individual files from a directory or may choose to transfer a single zipped file. Zipped files contain the README file and either netCDF files or ASCII text files depending on the zipped file name. (ex) co2_mlo_surface-insitu_1_ASCIItext.zip (ex) co2_mlo_surface-insitu_1_netCDF.zip 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 ------------------------------------------------------------------- 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. Zhao, C., and P.P. Tans (2006), Estimating uncertainty of the WMO Mole Fraction Scale for carbon dioxide in air, J. Geophys. Res. 111, D08S09, doi: 10.1029/2005JD006003. -------------------------------------------------------------------