INDOEX: Maldives KCO Chemistry Gas Chromatograph (Lobert) Contact: j.lobert@bigfoot.com; http://www-indoex.ucsd.edu/observatory/ http://JurgenLobert.org/ CATEGORY: INDOEX: Maldives KCO TITLE: KCO Surface.Gases (Lobert) AUTHOR: J.M. Lobert Center for Clouds, Chemistry and Climate Scripps Institution of Oceanography University of California, San Diego 9500 Gilman Drive La Jolla, CA 92093-0221 USA 1.0 DATA SET OVERVIEW: The data set contains daily, mean surface mixing ratios for the gases nitrous oxide (N2O), sulfur hexafluoride (SF6), chlorofluorocarbon-11 (CFC-11), chlorofluorocarbon-12 (CFC12) and carbon tetrachloride (CCl4) collected at the Kaashidhoo Climate Observatory (KCO) during the INDOEX IFP Feburary to March 1999. Data coverage is (inclusive) 12. February 1999 to 29. March 1999. KCO is located at 4.9664° N and 73.4657° E, the air inlet for all gases was mounted about 14 m above sea level (mean elevation of the site is about 0.5-1.0 m) on the top of the observation tower. KCO local time is UT + 5 hours. For website info, see authors. 2.0 INSTRUMENT DESCRIPTION: A gas chromatograph (Agilent Technologies) with dual-electron capture detectors (ECDs) was used to determine mixing ratios for the above compounds in ambient air. 3/8" OD Decabon tubing and a metal bellows pump were used to draw air in at about 15 l/min, of which a 60 ml/min stream was diverted to the sample loops of about 3 (CFCs, CCl4) and 10 ml volume (N2O, SF6). An inline, Nafion-type gas dryer was used to dry the air sample; calibration was carried out with a NOAA/CMDL standard. For a more detailed description of this instrument and the experiment, see Lobert and Harris (submitted to JGR)or contact the author. 3.0 DATA COLLECTION AND PROCESSING: Ambient air was continuously drawn through the instrument using 9 mm OD Decoron tubing. The instrument runtime for each sample was about 30 minutes, two air samples were bracketed with a calibration gas measurement. Daily means were then computed from these individual data points. Data intercomparison with NOAA/CMDL flasks taken at the same site yielded an agreement within 5% for some compounds. For others, comparison with NOAA/CMDL stations yielded a similar agreement. 4.0 DATA FORMAT: All files are in plain, tab-delimited ASCII text. One file for each compound Data headers as they appear in the files: DayTimeSpread DOY1999 XXXmean XXXstddev XXXstderr XXXmedian XXX_n XXXmax XXXmin with XXX denoting the gas. Header explanation: "DayTimeSpread" is the Date and Time (Universal time) of 1999 in spreadsheet format, noon of 01 January 1999 is 36161.5. "DOY1999" is the decimal day of year 1999, noon of 01 January is 1.5 XXXmean is the mean, daily gas mixing ratio in ppb (parts per billion, 10^-9 mole per mole of air) or ppt (parts per trillion, 10^-12 mole per mole of air). All units are in ppb for N2O and ppt for all other gases, except XXX_n, which is dimensionless (number of measurements per day). 5.0 DATA REMARKS: none 6.0 REFERENCES: 1) Jürgen M. Lobert and Joyce Harris, Trace Gases and Air Mass Origin at Kaashidhoo, Indian Ocean. revised, submitted to JGR.