Analysis of Refractive-Index Layer Observations during CASPER-East

Meteorological observations were made during October 12 to November 6, 2015 onboard the R/V Atlantic Explorer as part of the CASPER-East field program to understand the formation and dissolution of temperature and moisture gradient layers in the marine surface layer over the continental shelf off North Carolina. A suite of meteorological and oceanic instruments were deployed by the Notre Dame/ARL/NOAA team. The former included a stabilized Doppler wind Lidar, microwave radiometer (MWR), tethered lifting system, and a fully instrument bow mast flux system. The conditions for the appearance of refractive index layers (observed by MWR) are discussed in this presentation, focusing on measurements made by the flux tower at the ship bow. The bow mast was outfitted with a Vaisala WXT system, 3 levels of ultrasonic anemometers, temperature and relative humidity probes, a LICOR 7500A open path water vapor flux sensor, a net radiometer; and a pressure sensor. True wind speed and wind direction and temperature obtained by processing data of WXT and sonic anemometers, after correcting for the ship distortion and ship-plumes, were in good agreement. Inertial dissipation and covariance methods were used to calculate fluxes using the data from LICOR (water vapor) and sonics (momentum and heat), and they showed a marked difference with those obtained using the COARE 3.5 algorithm, perhaps in part due to breakdown of similarity assumptions made in deriving the latter. Observed variations of latent heat and water vapor fluxes could be related to local background meteorological and sea surface conditions, and hence to the observation of refractive-index layer evolution.