In-situ observation of surface layer scalar profiles for characterizing Evaporative Duct properties

Abstract

Marine atmospheric surface layer (MASL) is the lowest few tens of meters of the atmosphere immediately adjacent to the ocean surface. Because of surface evaporation, the MASL often consists of a surface trapping layer and hence a ducting layer for the propagation of electromagnetic Wave (EM) propagation often referred to as Evaporative Duct (ED). Such ducting conditions in the MASL are characterized through the temperature and humidity profiles and are affected by the surface layer wind profiles as well. These profiles are normally obtained by a MASL model based on the Monin-Obukhov Similarity theory (MOST) and input of measured quantities at a fixed level. However, MOST is based on the empirical dimensionless functions obtained over the land surfaces, the fidelity of bulk parameterization derived surface layer profiles are often debatable. Direct measurements of the MASL profiles of temperature and humidity are needed at high vertical resolution so that the gradients near the surface can be resolved. Such measurements should be done away from the immediate ship environment to avoid contamination by the ship structure.