--------------------------------------------------------------------- Atmospheric Methane (CH4), Carbon Dioxide (CO2) Dry Air Mole Fractions and Carbon Monoxide (CO) from Harvard University in the CARVE Aircraft Campaign Alaska, USA, April - October 2013 Harvard University School of Engineering and Applied Sciences Earth and Planetary Sciences Version: 2014-03-14 Prepared by: Rachel Chang -------------------------------------------------------------------- CONTENTS 1. Data source and contacts 2. Use of data 3. Warnings 4. Data comments 5. References -------------------------------------------------------------------- 1. DATA SOURCE AND CONTACTS This directory contains atmospheric Methane (CH4), Carbon Dioxide (CO2) and Carbon Monoxide (CO) Dry Air Mole Fractions from continuous measurements from the Carbon in the Arctic Reservoirs Vulnerability Experiment (CARVE) Apr-Oct 2013 on board the Sherpa C-23B aircraft owned and operated by NASA. Correspondence concerning these data should be directed to: Prof. Steven Wofsy or Dr. Rachel Chang Harvard Universtiy School of Engineering and Applied Sciences 24 Oxford Street Cambridge, MA 02138 U.S.A. email: swofsy@seas.harvard.edu rachel.yw.chang@gmail.com -------------------------------------------------------------------- 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. We rely on the ethics and integrity of the user to assure that we receive fair credit for this work. If the data are obtained for potential use in a publication or presentation, S. Wofsy should be informed at the outset of the nature of this work. If the data are essential to the work, or if an important result or conclusion depends on the data, co-authorship may be appropriate. This should be discussed at an early stage in the work. Manuscripts using the data should be sent to S. Wofsy for review before they are submitted for publication so we can insure that the quality and limitations of the data are accurately represented. -------------------------------------------------------------------- 3. WARNINGS Lab-wide notes: 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. Users of the data are requested to ensure that they are publishing only the most recent revision. We are not responsible for results and conclusions based on use of these data without regard to this warning. -------------------------------------------------------------------- 4. DATA COMMENTS Measurements are from the Harvard University four-species (Picarro model G2401m, SN CFKBDS2010) cavity ring-down spectrometer system. Columns: Days_Since_Jan1 = fractional days since midnight Jan 1 (i.e. 6 AM on Jan 1 = 0.25) GPS_Lat = Latitude from GPS GPS_Lon = Longitude from GPS GPS_Alt = Altitude in meters above sea level from GPS CO2.ppm = CO2 dry mole fraction in parts per million CH4.ppb = CH4 dry mole fraction in parts per billion CO.ppb = CO mixing ratio in parts per billion CO2.flag = flag indicating quality of CO2, see below CH4.flag = flag indicating quality of CH4, see below CO.flag = flag indicating quality of CO, see below Flag values: 0 = data are good 1 = mixing ratios are above or below the in-flight standards 375.9 ppm, 418.9 ppm for CO2 1700.5 ppb, 2294.1 ppb for CH4 40 ppb, 204 ppb for CO These values are for the user's reference since the line absorption is expected to remain fairly linear 2 = variation in cavity pressure is beyond 139.8-140.2 torr or the cavity temperature is outside the range 44.98-45.02 C 3 = the wavelength monitor was unstable (April 2013, Days_Since_Jan1=91-95), resulting in very noisy data. A new wavelength monitor and lower-vibration inlet valve were installed in time for the first May flight and the remaining data are much less noisy; or the calibration system was not enabled until mid-way through the flight on 2013-07-09 (Days_Since_Jan1=189). These data were calibrated using the mean calibration for the second half of the flight. Data are reported at 5-second intervals. Times for which there are no valid measurements have been assigned a default mole fration (-999.9). Native CO2, CH4 and CO measurements are at 2.5 to 5 second resolution, and all have been aggregated onto 5-second intervals. Methane measurements are reported on the gravimetrically-prepared NOAA 2004 CH4 standard scale (see Dlugokencky et al., 2005). CO2 measurements are reported on the gravimetrically-prepared NOAA 2007 CO2 standard scale (see Zhao and Tans, 2006). CO measurements are reported on the gravimetrically-prepared NOAA CO standard scale (see Novelli et al., 1994). Sample air was dried in two stages prior to measurement, first with a nafion dryer, then followed by a dry ice trap. Hence no water data are reported. The sample time has been corrected to account for lag in the inlet lines. ------------------------------------------------------------------- 5. REFERENCES Dlugokencky, E.J., R.C. Myers, P.M. Lang, K.A. Masarie, A.M. Crotwell, K.W. Thoning, B.D. Hall, J.W. Elkins, and L.P. Steele (2005), Conversion of NOAA CMDL atmospheric dry air methane mole fractions to a gravimetrically-prepared standard scale, J. Geophys. Res., 110, D18306, doi : 10.1029/2005JD006035. Novelli, P. C., J.E. J.. Collins, R. C. Myers, G.W. Sachse and H.E. Scheel, (1994), Reevaluation of the NOAA/CMDL carbon monoxide reference scale and comparisons with CO reference gases at NASA-Langley and the Fraunhofer Institute, J. Geophys. Res., 99, D6, 12833-12839, JD00314 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. -------------------------------------------------------------------