--------------------------------------------------------------------- Atmospheric Carbon Monoxide Mixing Ratios from the NOAA GMD Tower Network, 2003 - 2009 04 Version: 2011-08-31 -------------------------------------------------------------------- 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 - All 7.4 DATA - QC Flags 8. Data Retrieval 9. References -------------------------------------------------------------------- 1. DATA SOURCE AND CONTACTS National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) Global Monitoring Division (GMD) Carbon Cycle Greenhouse Gases (CCGG) Correspondence concerning these data should be directed to: Dr. Arlyn E. Andrews NOAA ESRL Global Monitoring Division 325 Broadway, GMD-1 Boulder, CO 80305 U.S.A. email: Arlyn.Andrews@noaa.gov The collection and analysis of data available from the NOAA ESRL data archive is greatly enabled by collaborating institutions. Collaborators are identified in the header of each data file. The collection and analysis of data available from the NOAA ESRL data archive is greatly enabled by collaborating institutions. Collaborators are identified in the header of each data file. -------------------------------------------------------------------- 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 Andrews, A.E., J. Kofler, P.S. Bakwin, C. Zhao, P. Tans (2009), Carbon Dioxide and Carbon Monoxide Dry Air Mole Fractions from the NOAA ESRL Tall Tower Network, 1992-2009, Version: 2011-08-31, Path: ftp://ftp.cmdl.noaa.gov/ccg/towers/. -------------------------------------------------------------------- 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 -------------------------------------------------------------------- 6. INTRODUCTION CO Dry Air Mole Fraction: The CO abundance is given as a mole fraction with units of parts per billion (ppb). This value corresponds to the number of CO molecules per 1 billion molecules of dry air. Each data point represents a 120 sec average of data collected at 0.2 Hz. ------------------------------------------------------------------- 7. DATA - GENERAL COMMENTS Uncertainty Estimates: The Total Uncertainty Estimate attempts to account for known quantifiable errors in the CO measurements. Total Uncertainty is comprised of three components: (1) Atmospheric Variability, AV; (2) Measurement Uncertainty, MU; (3) Scale Uncertainty, SU; such that TU^2=AV^2+MU^2+SU^2. Atmospheric Variability is a standard deviation that represents real natural variability of the species' abundance during the measurement period (30 sec). Measurement Uncertainty is computed from several quasi-independent terms, including uncertainty in the calibration scale, drift in the analyzer baseline and gain between calibrations, any lack of full equilibration of air samples or standards, curve fitting errors, extrapolation error for samples that are outside of the calibrated range, differences in H2O content of samples and standards. All measurements are reported relative to the WMO mole fraction scale. For CO, calibration scale uncertainty is 1% of the measured value. Sample equilibration error/atmospheric variability is frequently the largest contribution to the total uncertainty. -------------------------------------------------------------------- 7.1 DATA - SAMPLING LOCATIONS NOAA GMD tower sites. The table includes the three letter code used to identify each site; the site name; latitude, longitude, and altitude (meters above sea level) of the sampling location; the number of samples; the first and last sample dates; and sampling status. 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/. ------------------------------------------------------------------- 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) ------------------------------------------------------------------- 7.3 DATA - ALL The data files in "ccg/tower/site/co/" use the following naming scheme (see Section 7.2): xxx[data grouping]_01C3_all.co (ex) lef200403_01C3_all.co2 contains all LEF co2 data from 2004-03 (March 2004). (ex) amt200601_01C3_all.aux contains all AMT auxillary data from 2006-01 (January 2006). The data files contain multiple lines of header information (identified by a "#" character in the first column) followed by one line for each atmospheric measurement. 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: [MINUTE] Field 7: [SECOND] Field 8: [LATITUDE] The latitude where the sample was collected, (negative (-) numbers indicate samples collected in the southern hemipshere). Field 9: [LONGITUDE] The longitude where the sample was collected, (negative (-) numbers indicate samples collected in the western hemisphere). Field 10: [ELEVATION] The elevation of the site (masl). Field 11: [INTAKE HEIGHT] The intake height above ground level (m). Field 12: [MEASURED VALUE] The dry air mole fraction. Missing values are denoted by -999.99[9]. Field 13: [TOTAL UNCERTAINTY ESTIMATE] The Total Uncertainty estimate (see Section 7). Missing values are denoted by -999.99[9]. Field 14: [ATMOSPHERIC VARIABILTY] The Total Uncertainty estimate (see Section 7). Missing values are denoted by -999.99[9]. Field 15: [MEASUREMENT UNCERTAINTY] The Measurement Uncertainty estimate (see Section 7). Missing values are denoted by -999.99[9]. Field 16: [SCALE UNCERTAINTY] The Scale Uncertainty estimate (see Section 7). Missing values are denoted by -999.99[9]. Field 17: [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) code yr mo dy hr mn sc lat lon elev(masl) ht(magl) value totunc atmvar measunc scaleunc flag AMT 2009 04 30 23 29 55 45.0300 -68.6800 50.000 12.0 396.811 0.140 0.115 0.039 0.070 ... ------------------------------------------------------------------- 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. Flag Description RETAINED ... Normal Operation ..F Flow through Licor 50-95 sccm (normal flow = 100 sccm) ..R Data outside calibrated range REJECTION F.. Flow through Licor < 50 sccm (normal flow = 100 sccm) C.. Temporal gap in calibrations precludes reliable calculation. Z.. Suspect value not identified by standard QC algorithms (manually applied) L.. Leak suspected. A.. Other known problem with analyzed value ------------------------------------------------------------------- 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 ------------------------------------------------------------------- 9. REFERENCES Tans, P.P. et al., Carbon Cycle (Group Report), Climate Monitoring and Diagnostics Laboratory, No. 23, Summary Report 1994-1995, Hoffman, D.J., J.T. Peterson and R.M. Rosson, eds, US Department of Commerce, Boulder, Colorado, 1996. Bakwin, P.S., P.P. Tans, D.F. Hurst, C.Zhao, Measurements of Carbon Dioxide on Very Tall Towers: Results of the NOAA/CMDL Program, Tellus, Ser. B., 50, 401-415, 1998. Zhao, C., P.S. Bakwin, and P.P. Tans, A design for unattended monitoring of trace gases on a tall tower, J. Atmos. Ocean. Tech., 14, 1139-1145, 1997. -------------------------------------------------------------------