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NAMMA Carbon monOxide By Attenuated Laser Transmission (COBALT) Table of Contents
COBALT (Carbon mOnoxide By Attenuation of Laser Transmission), an autonomous instrument based on off-axis integrated cavity output spectroscopy, has been developed and successfully deployed for measurements of carbon monoxide in the troposphere and tropopause onboard a NASA DC-8 aircraft. This instrument was used to measure in-situ carbon monoxide mixing ratios, and to derive mixing ratio profiles. Tunable-laser absorption spectroscopy is an established analytical technique that is being used to obtain accurate in-situ CO concentrations. CampaignThese data files were generated during support of the NASA African Monsoon Multidisciplinary Analyses (NAMMA) campaign, a field research investigation sponsored by the Science Mission Directorate of the National Aeronautics and Space Administration (NASA). This mission was based in the Cape Verde Islands, 350 miles off the coast of Senegal in west Africa. Commencing in August 2006, NASA scientists employed surface observation networks and aircraft to characterize the evolution and structure of African Easterly Waves (AEWs) and Mesoscale Convective Systems over continental western Africa, and their associated impacts on regional water and energy budgets. For more information about the NAMMA Campaign, go to the NAMMA web site: http://namma.nsstc.nasa.gov/ Instrument DescriptionThe COBALT instrument consists of a measurement cell comprised of two high-reflectivity mirrors, a continuous-wave quantum-cascade laser, gas sampling system, control and data-acquisition electronics, and data-analysis software. CO measurements were determined from high-resolution CO absorption line shapes obtained by tuning the laser wavelength over the R(7) transition of the fundamental vibration band near 2172.8 cm-1. The instrument reports CO mixing ratio (mole fraction) at a 1-Hz rate based on measured absorption, gas temperature, and pressure using Beer's Law. Previous flights have shown the instrument to record CO values with a precision of 0.2 ppbv (1-s averaging time) and an accuracy limited by the reference CO gas cylinder (uncertainty <1.0%). File Naming ConventionThe COBALT data files are named following the example below:
where, Data Format The COBALT data files follow the "1001" Gaines-Hipskind format as described in the document entitled - "ASCII File Format Specification for Data Exchange" found at: http://espoarchive.nasa.gov/archive/docs/formatspec_2_0.pdf. These carbon monoxide mixing ratio data files contain informative headers that explain the dataset. Column 1 is the time, in seconds UTC, and column 2 is CO Volumetric Mixing Ratio in ppbv (wet air). An example data file is listed below: References R. Provencal, M. Gupta, T. G. Owano, D. S. Baer, K. N. Ricci, A. O"Keefe, and J. R. Podolske, "Cavity-enhanced quantum-cascade laser-based instrument for carbon monoxide measurements", Appl.Opt. 44, 6712-6717 (2005). Contact InformationThe data producer is:
To order these data or for further information, please contact:
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