Title: C130 Carbon Monoxide Concentration Contact: Greg Kok NCAR-RAF Box 3000 Boulder, Colorado 80307 phone 303-497-1070 fax 303-497-1092 E-Mail Address: kok@ucar.edu Or Andre Prevot RAF, NCAR Box 3000 Boulder, CO 80307 USA 303-497-1042 303-497-1092 E-Mail Address: prevot@raf.atd.ucar.edu Or Richard Schillawski NCAR/RAF 10800 W 120th Broomfield, CO 80021 USA 303-497-1046 303-497-1092 E-Mail Address: rschill@ucar.edu Data Set Description: This data set contains carbon monoxide measurements made from the NCAR C-130 in the ACE-1 program. The data parameter is COCAL, the calibrated CO signal in ppbv. The carbon monoxide instrumentation used an infrared absorption method (TECO 48 with a modified optical system). After every 5 minute sampling period the instrument was zeroed for 2 minutes to take baseline changes into account. The data during zeroing periods were eliminated from the data set by setting them to -32767.0. The span was obtained by calibrating the instrument with a standard cylinder of CO in air. Our standard was cross calibrated with a NIST SRM-standard. The vibration of the aircraft significantly increases the noise in the signal for this instrument. To decrease the noise, two procedures were applied. The raw signal was smoothed by taking the median of a running 15 second window over the whole data set. This procedure eliminates data outliers. After the smoothing, a spline fit was calculated from the zeroing periods and the CO signal was obtained by subtracting the zero spline from the data. To remove high frequency noise further, a 45 second running average was then applied and the calibrated span was used to get the CO concentrations. The time lag of the air entering the inlet to the measurement was determined to be around 50 seconds; the data were shifted accordingly. Publications that make general use of these data are requested to acknowledge Andre Prevot, Richard Schillawski and Greg Kok for providing the data. Co-authorship is requested for significant use of these data in a publication. Format: space-delimited ASCII with fields: Date : (UTC) YYYY/MM/DD Time : (UTC) HH:MM:SS XLATC :GPS-Corrected Inertial Latitude deg XLONC :GPS-Corrected Inertial Longitude deg PALT :NACA Pressure Altitude M COCAL :Corrected Carbon Monoxide Concentration ppbv File Name Conventions: rfxxx.dat where xxx is the flight number. An example for flight 30 is rf30.dat. References: None.