-------------------------------------------------------------------------------- Readme file to accompany NOAA flask data: CH4, N2O, CO, CO2 (C13, C14, O18), H2 CH4 version v20090618, N2O v20090714, CO v20090618, CO2 v20090715, CO2(C13) v20090601, CO2(C14) v20081024, CO2(O18) v20090601, H2 v20061127 -------------------------------------------------------------------------------- TERMS AND CONDITIONS (Adapted from NOAA and NACP data policy) ------------------------------------------------------------- Use of these data in any part implies an agreement on the part of the user that individuals and/or institutions responsible for contributing to data sets used must be specifically cited in addition to a general citation of the NACP greenhouse gas database. The CH4 data should be cited as follows: Dlugokencky, E.J., P.M. Lang, and K.A. Masarie (2009), Atmospheric Methane Dry Air Mole Fractions from the NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network, 1983-2008, Version: 2009-06-18, Path: ftp://ftp.cmdl.noaa.gov/ccg/ch4/flask/event/. for CO: Novelli, P.C. and K.A. Masarie (2009), Atmospheric Carbon Monoxide Dry Air Mole Fractions from the NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network, 1988-2008, Version: 2009-06-18, Path: ftp://ftp.cmdl.noaa.gov/ccg/co/flask/event/. for CO2: Conway, T.J., P.M. Lang, and K.A. Masarie (2009), Atmospheric Carbon Dioxide Dry Air Mole Fractions from the NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network, 1968-2008, Version: 2009-07-15, Path: ftp://ftp.cmdl.noaa.gov/ccg/co2/flask/event/. for CO2(C13): White, J.W.C. and B.H. Vaughn (2009), University of Colorado, Institute of Arctic and Alpine Research (INSTAAR), Stable Isotopic Composition of Atmospheric Carbon Dioxide (13C and 18O) from the NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network, 1990-2007, Version: 2009-06-01, Path: ftp://ftp.cmdl.noaa.gov/ccg/co2c13/flask/event/. for CO2(C14): Turnbull, J.C., S.J. Lehman, J.B. Miller and P.P. Tans (2008), University of Colorado, Institute of Alpine and Arctic Research (INSTAAR), Radiocarbon Composition of Atmospheric Carbon Dioxide (14CO2) from the NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network, 2003-2007, Version: 2008-10-24, Path: ftp://ftp.cmdl.noaa.gov/ccg/co2c14/flask/event/. for CO2(O18): White, J. and B. Vaughn (2009), University of Colorado, Institute of Arctic and Alpine Research (INSTAAR), Stable Isotopic Composition of Atmospheric Carbon Dioxide (13C and 18O) from the NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network, 1990-2007, Version: 2009-06-01, Path: ftp://ftp.cmdl.noaa.gov/ccg/co2o18/flask/event/. for H2: Novelli, Paul C (2009), Atmospheric Hydrogen Mixing Ratios from the NOAA GMD Carbon Cycle Cooperative Global Air Sampling Network, 1988-2005, Version: 2006-11-27, Path: ftp://ftp.cmdl.noaa.gov/ccg/h2/flask/event/. NACP investigators will include an acknowledgement in each publication or presentation arising from participation in NACP. The wording shall be similar to the following: "This study was part of the North American Carbon Program." Data providers and funding agencies may request additional acknowledgements. Upon publication of results, investigators should send the NACP Office an electronic copy of the publication. 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 a greater understanding and new scientific insights. The availability of these data does not constitute publication of the data. We rely on the ethics and integrity of the user to assure that the source(s) receive fair credit for their work. If the data are obtained for potential use in a publication or presentation, the source(s) should be informed at the outset of the nature of this work. If the source's data are essential to the work, or if an important result or conclusion depends on their data, co-authorship may be appropriate. This should be discussed at an early stage in the work. Manuscripts using the source's data should be sent to the source(s) for review before they are submitted for publication so we can ensure that the quality and limitations of the data are accurately represented. RECIPROCITY AGREEMENT 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 source 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. NOAA FLASK DATA PROJECT PURPOSE & DESCRIPTION --------------------------------------------- The PIs for the project are: Thomas J. Conway, NOAA/ESRL Global Monitoring Division, Thomas.J.Conway@noaa.gov Edward J. Dlugokencky, NOAA/ESRL Global Monitoring Division, ed.dlugokencky@noaa.gov Scott J. Lehman, U of Colorado Insitute of Arctic and Alpine Research, Scott.Lehman@colorado.edu Ken A. Masarie, NOAA/ESRL Global Monitoring Division, kenneth.masarie@noaa.gov John B. Miller, NOAA/ESRL Global Monitoring Division, John.B.Miller@noaa.gov Paul C. Novelli, NOAA/ESRL Global Monitoring Division, Paul.C.Novelli@noaa.gov Pieter P. Tans, NOAA/ESRL Global Monitoring Division, Pieter.Tans@noaa.gov Jocelyn Turnbull, NOAA/ESRL Global Monitoring Division, Jocelyn.Turnbull@noaa.gov Bruce H. Vaughn, U of Colorado Institute of Arctic and Alpine Research, bruce.vaughn@colorado.edu James White, U of Colorado Institute of Arctic and Alpine Research, James.White@colorado.edu I. Introduction NOAA flask data provides measurements of eight species, drawing samples from ground-based sites as well as aircraft. Sampling frequencies are approximately weekly for the fixed sites and average one sample every 3 weeks per latitude zone for POC (Pacific Ocean) measurements. The air samples are collected by two general methods: flushing and then pressurizing glass flasks with a pump, or opening a stopcock on an evacuated glass flask. During each sampling event, a pair of flasks is filled. The Pacific Ocean Cruise (POC, travelling between the US west coast and New Zealand or Australia) data have been merged and grouped into 5 degree latitude bins. NOAA GMD uses a gas chromatograph with various separation methods for different species. CH4 is separated and analyzed with Flame Ionization Detection (FID), while a mercury oxide (HgO) method is used to determine the mixing ratios of CO and H2. N2O measurements use an electron capture detector (ECD). This study uses a non-dispersive infrared analyzer (NDIR) to measure CO2, while isotope fractionations of CO2 (C13, C14, O18) are measured by mass spectrometry: Each analysis of CO2(C13) and CO2(O18) is carried out by first extracting CO2 from the sample and then measuring its isotopic composition relative to CO2 gas in a reference standard. The isotopic analysis is carried out simultaneously with the extraction of the next sample. This system is maintained and operated by the University of Colorado/INSTAAR Stable Isotope Laboratory. The radiocarbon content of carbon dioxide (CO2C14) in ambient and standard air samples is measured by: (1) Cryogenic extraction of CO2 from whole air; (2) Reduction of the collected CO2 with hydrogen over an iron catalyst; and (3) accelerator mass spectrometric measurement of the carbon isotopic ratio. Typically, air from two flasks is combined to obtain sufficient sample for a single 14CO2 measurement. WARNING: Users of O18 data should be aware that many flasks in the network are sampled without drying the air. This can result in isotopic exchange between CO2 and H2O. (See Gemery et al, 1996). O18 values depleted by as much as several per mill are typical in such flasks. While most of the problem flasks can be identified via poor pair agreement, good pair agreement is also possible in this situation. The Stable Isotope Lab recommends using O18 data at sites between 30N and 30S with caution. These sites are the warmest and most humid and have the highest chance of compromised O18 data. Data from other sites are considered more reliable. NOAA is working to dry all air at wet sites prior to sampling. As of May 2009, NOAA has applied a new flagging scheme that makes more of the data from potentially wet sites available for use. For additional information, see the comments section of the CO2(O18) README at: ftp://ftp.cmdl.noaa.gov/ccg/co2o18/flask/README_flask_co2o18.html For more information and data updates, visit: ftp://ftp.cmdl.noaa.gov/ccg/ II. Methods Parameter Method PIs a. CH4 GC/FID E. Duglokencky, NOAA/ESRL, ed.duglokencky@nooa.gov b. CO GC/HgO P. Novelli, NOAA/ESRL, Paul.C.Novelli@noaa.gov K. Masarie, NOAA/ESRL, kenneth.masarie@noaa.gov c. CO2 NDIR infrared analyzer P. Tans, NOAA/ESRL, Pieter.Tans@noaa.gov T. Conway, NOAA/ESRL, Thomas.J.Conway@noaa.gov d. CO2(C13) Micromass Optima mass J. White, INSTAAR, James.White@colorado.edu spectrometer (MS) from B. Vaughn, INSTAAR, bruce.vaughn@colorado.edu 1996 to 2005. GV Instruments (formerly Micromass) Isoprime dual-Inlet MS replaced Optima MS in 2005 e. CO2(C14) Accelerator MS J. Turnbull, NOAA/ESRL, Jocelyn.Turnbull@noaa.gov P. Tans, NOAA/ESRL, Pieter.Tans@noaa.gov J. Miller, NOAA/ESRL, John.B.Miller@noaa.gov f. CO2(O18) Micromass Optima MS J. White, INSTAAR, James.White@colorado.edu replaced by GV Isoprime B. Vaughn, INSTAAR, bruce.vaughn@colorado.edu dual-Inlet MS g. H2 GC/HgO P. Novelli, NOAA/ESRL, Paul.C.Novelli@noaa.gov h. N2O GC/ECD E. Duglokencky, NOAA/ESRL, ed.duglokencky@nooa.gov VARIABLE NAMES -------------- YYYYMMDD : Year, month, and day of sampling doy : Absolute day of year UTC : Coordinated Universal Time, in seconds from midnight station : NOAA three-letter code for in-situ measurement site flask.ID : ID number of sample container sampling.method : A single-character code that identifies the sample collection method. The codes are: "P" - Sample collected using a portable, battery powered pumping unit. Two flasks are connected in series, flushed with air, and then pressurized to 1.2 - 1.5 times ambient pressure. "D" - Similar to P but the air passes through a condenser cooled to about 5 deg C to partially dry the sample. "G" - Similar to D but with a gold-plated condenser. "T" - Evacuated flask filled by opening an O-ring sealed stopcock. "S" - Flasks filled at NOAA ESRL observatories by sampling air from the in situ CO2 measurement air intake system. "N" - Before 1981, flasks filled using a hand-held aspirator bulb. After 1981, flasks filled using a pump different from those used in method P, D, or G. "F" - Five liter evacuated flasks filled by opening a ground glass, greased stopcock. latitude : Latitude of measuring site, in degrees longitude : Longitude of measuring site, in degrees altitude : Altitude of measuring site, in masl CH4_FID : Methane mixing ratio via GC/FID, in ppbv CH4_FID.flag : 3-column flags as noted below, for CH4 measurements CO_HgOGC : Carbon monoxide mixing ratio via GC/HgO, in ppbv CO_HgOGC.flag : 3-column flags as noted below, for CO measurements CO2_NDIR : Carbon dioxide mixing ratio via NDIR, in ppmv CO2_NDIR.flag : 3-column flags as noted below, for CO2 measurements CO2C13_INSTAAR : Isotope fractionation of CO2(C13). The isotope ratios are reported in units of per mil where d13C = [(13C/12Csample)/ (13C/12Cstandard)-1] x 1000. CO2C13_INSTAAR.flag: 3-column flags as noted below, for CO2(C13) measurements CO2C14_INSTAAR : Isotope fractionation of CO2(C14). The isotope ratios are reported in units of per mil where d14C = [(14C/12Csample)/ (14C/12Cstandard)-1] x 1000. SD.CO2C14_INSTAAR: Standard deviation error of CO2(C14) mixing ratio, in per mill CO2C14_INSTAAR.flag: 3-column flags as noted below, for CO2(C14) measurements CO2O18_INSTAAR : Isotope fractionation of CO2(O18). The isotope ratios are reported in units of per mill where d18O = [(18O/16Osample)/ (18O/16Ostandard)-1] x 1000 CO2O18_INSTAAR.flag: 3-column flags as noted below, for CO2(O18) measurements H2_HgOGC : H2 mixing ratio via GC/HgO, in ppbv H2_HgOGC.flag : 3-column flags as noted below, for H2 measurements N2O_ECD : N2O mixing ratio via GC/ECD, in ppbv N2O_ECD.flag : 3-column flags as noted below, for N2O measurements --------------------------------------------------------------------------------------- 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. NOTE: In this data set, REJECTION flag data has been REMOVED. SUMMARY OF SELECTION AND COMMENT FLAGS -------------------------------------- CO: RETAINED ... Accepted as background air sample ..I sample has also been measured by another lab as part of an intercomparison experiment ..C mixing ratio falls outside of calibration range (see Section ). ..< first reference sample flagged ..> second reference sample flagged SELECTED .X. determined using a statistical method to be an outlier .N. flagged manually as an outlier NOTE: Some sites known to be heavily impacted by regional pollution are not SELECTED for background conditions. Among these are BAL, BSC, HUN, OBN and TAP. CO2: RETAINED ... (3 periods) good pair (D <= 0.5 ppm) ..H high member of bad pair; retained ..L low member of bad pair; retained ..I sample has also been measured by another lab as part of an intercomparison experiment SELECTED .X. flagged automatically as an outlier, greater than 3 sigma from a fitted curve .Z. flagged manually as an outlier (this is necessary to prevent distortion of the curve used for automated data selection) CO2(C13)/CO2(O18): RETAINED Automatic flags - applied during data reduction (by the processing program) ..L linked flask (0.5-liter flask analyzed together with its mate) ..S single flask (flask without a pair mate) ..I flask also analyzed by another lab (aliquot taken) ..i same as "I" above, but displaced a previous flag in this field. ... good flask SELECTED Automatic flags - applied by outlier-identification software (OUTLIER/FILTER) .X. outlier by more than 3-sigma from a CCGVU curve Hand flags - applied by hand to selected flasks .!. hand flag CO2(C14): RETAINED ..M Multiple flasks were combined to obtain this measurement; retained ..I sample has also been measured by another lab as part of an intercomparison experiment SELECTED .F. automatically flagged as non-background .Z. flagged manually as non-background H2: REJECTED .X. Not representative of background conditions (> 3 sigma from a fitted curve), may include unidentified sampling/analysis problems. .N. High/low mixing ratio thought to not represent background conditions. ..I Flask is one of the pair used in an intercomparison with the cooperating agency NOTE: In the H2 data set, NOAA recommends that 1st and 2nd column flags be rejected. In this formatted version, 2nd column flags have not been removed. MISSING VALUES ------------- For files in .RData format, missing values are represented by "NA". For files in .csv format, missing values are represented by "NaN".