Electromagnetic Ducting in the Near‐Shore Marine Environment: Results From the CASPER‐East Field Experiment

Abstract

We used the observations from the east coast of the USA and model simulations to elicit marine atmospheric surface layer (MASL) processes that controlled the spatial variability of electromagnetic ducting conditions in the near‐shore (60 km) marine environment during CASPER‐East field campaign. The estimated evaporation duct height (EDH) showed an average decrease of ∼2.5 m over every 10 km distance from the shore. The surface layer stability conditions chiefly determined the duct heights. While the mean duct height remained ∼10 m under unstable conditions, deeper (>20 m) evaporation ducts were frequently evident (∼40% of the time) during stable MASL conditions, which were responsible for the observed near‐shore EDH variability. Episodes of warm offshore flow and advection of hot and humid air from the Gulfstream region created ideal environmental conditions for stable MASL development and thus deeper ducts over the coastal ocean. A detailed case study of warm and humid Gulfstream air advection over the cooler coastal ocean is presented to elucidate the temporal evolution of the surface layer stability and associated changes in the spatial distribution of the evaporation duct height.

Evaporation Duct Anomalies Caused by Mesoscale Eddies in the Kuroshio Extension

“…At larger spatial scales, ocean waves can affect evaporation ducts by influencing the distribution of sea surface scalars (Anderson et al., 2004), and changes occur with boundary layer stability and wind speed (Jiang, 2020). In particular, abrupt horizontal changes in evaporation ducts resulting from stability variations are particularly notable in oceanic fronts or coastal current regions (Alappattu et al., 2022; Ding et al., 2021). Furthermore, the wind speed plays a significant role in modulating evaporation ducts in the presence of typhoons (Shi et al., 2019).…”