Air-Sea Interaction Related to Characterizing Electromagnetic Wave Propagation in the Atmosphere – CASPER Science Objectives and Measurement Strategy

The Coupled Air-Sea Processes and Electromagnetic Wave (EM) ducting Research (CASPER) is a Multidisciplinary University Research Initiative (MURI) project aimed at improving EM propagation prediction in marine atmospheric environments. The so-called refractive condition of the atmosphere depicts various atmospheric effects on EM propagation and is affected by the vertical gradients of temperature and, more importantly, water vapor. The depiction and prediction of these vertical gradients in the lower atmosphere are key to understanding EM propagation problems. EM ducting problems thus require in depth understanding of the layers with strong gradients in the lower atmosphere: the surface layer and inversion layer. The evaporation duct is associated with the surface layer while elevated or surface-based ducts are often associated with the boundary layer capping inversion. CASPER East focused on the MASL and its effects on EM propagation.

CASPER East field campaign was uniquely designed to make concurrent measurements to quantify evaporation ducts and the associated air-sea interaction environment, and quantify EM propagation with varying wavelength bands. The field campaign occurred between October 10 and November 6, 2015 offshore of Duck, NC. Major platforms of CASPER East include R/V Hugh Sharp, R/V Atlantic Explorer, instrumented Twin Otter research aircraft, and shore site based off a 500 m long pier in Duck, NC. A second aircraft, a SAAB 340, was also involved with multiple upper ocean remote sensing instruments. A suite of small wave buoys, small flux buoy, autonomous ocean vehicles, and tethered balloons ad rawinsondes were deployed to obtain the near surface temperature and water vapor profiles and surface fluxes in minimally disturbed environment.

In this presentation, we will present some of the air-sea interaction issues important to EM propagation substantiated with results from the CASPER field campaign. The overall design of the field measurements and example results from various platform/sensors will be discussed.