Flux Observations of Carbon from an Airborne Laboratory (FOCAL): Using Advances in Spectroscopy, Turbulent Wind Measurements, and Small, Commercial Aircraft to Create Eddy Covariance Flux Maps from the Air.

Over the past decade improvements in high-sensitivity, cavity-enhanced spectroscopic techniques have allowed for near-real time acquisition of atmospherically important gases at rates fast enough for use in eddy covariance. We report on the development of a suite of spectrometers capable of in situ measurements of the carbon-13 isotopologues of methane and carbon dioxide at high acquisition rates (10 Hz). Coupled with a mature airborne turbulence probe and a small, economical, commercial aircraft flying at 10 m above the surface FOCAL provides region scale surface fluxes of these important greenhouse gases. We describe the instrumentation, with emphasis on how new technology is changing the way these types of measurements can be made. FOCAL was first flown over the North Slope of Alaska in August, 2013. We will present a regional view of methane and carbon dioxide fluxes over parts of the North Slope as well as comparisons to traditional eddy covariance methods.