Browsing by Author "Hannun, Reem A."
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Item A Cavity-Enhanced UV Absorption Instrument for High Precision, Fast Time Response Ozone Measurements(EGU Publications, 2020-07-22) Hannun, Reem A.; Swanson, Andrew K.; Bailey, Steven A.; Hanisco, Thomas F.; Bui, T. Paul; Bourgeois, Ilann; Peischl, Jeff; Ryerson, Thomas B.The NASA Rapid Ozone Experiment (ROZE) is a broadband cavity-enhanced UV absorption instrument for the detection of in situ ozone (O₃). ROZE uses an incoherent LED light source coupled to a high-finesse optical cavity to achieve an effective pathlength of ~ 104 m. Due to its high-sensitivity and small optical cell volume, ROZE demonstrates a 1σ precision of 80 pptv (0.1 s) and 31 pptv (1 s), as well as a 1/e response time of 50 ms. ROZE can be operated in a range of field environments, including low- and high-altitude research aircraft, and is particularly suited to O₃ vertical flux measurements using the eddy covariance technique. ROZE was successfully integrated aboard the NASA DC-8 aircraft during July–September 2019 and validated against a well-established chemiluminescence measurement of O₃. A flight within the marine boundary layer also demonstrated flux measurement capabilities, and we observed a mean O₃ deposition velocity of 0.029 ± 0.005 cm s⁻¹ to the ocean surface. The performance characteristics detailed below make ROZE a robust, versatile instrument for field measurements of O₃.Item The NASA Carbon Airborne Flux Experiment (CARAFE): instrumentation and methodology(Copernicus Publications, 2018-03-28) Wolfe, Glenn M.; Kawa, S. Randy; Hanisco, Thomas F.; Hannun, Reem A.; Newman, Paul A.; Swanson, Andrew; Bailey, Steve; Barrick, John; Thornhill, K. Lee; Diskin, Glenn; DiGangi, Josh; Nowak, John B.; Sorenson, Carl; Bland, Geoffrey; Yungel, James K.; Swenson, Craig A.The exchange of trace gases between the Earth's surface and atmosphere strongly influences atmospheric composition. Airborne eddy covariance can quantify surface fluxes at local to regional scales (1–1000 km), potentially helping to bridge gaps between top-down and bottom-up flux estimates and offering novel insights into biophysical and biogeochemical processes. The NASA Carbon Airborne Flux Experiment (CARAFE) utilizes the NASA C-23 Sherpa aircraft with a suite of commercial and custom instrumentation to acquire fluxes of carbon dioxide, methane, sensible heat, and latent heat at high spatial resolution. Key components of the CARAFE payload are described, including the meteorological, greenhouse gas, water vapor, and surface imaging systems. Continuous wavelet transforms deliver spatially resolved fluxes along aircraft flight tracks. Flux analysis methodology is discussed in depth, with special emphasis on quantification of uncertainties. Typical uncertainties in derived surface fluxes are 40–90 % for a nominal resolution of 2 km or 16–35 % when averaged over a full leg (typically 30–40 km). CARAFE has successfully flown two missions in the eastern US in 2016 and 2017, quantifying fluxes over forest, cropland, wetlands, and water. Preliminary results from these campaigns are presented to highlight the performance of this system.