Raypath deviation under stable and unstable conditions

摘要

Ray-bending resulting from atmospheric refraction in the maritime environment has been shown to potentially produce significant effects on electro-optical target detection and imaging. Positive bending makes possible detection beyond the horizon while negative bending reduces the maximum inter-vision range (MIVR) and is likely to produce severe image distortion or mirages. It has been shown by many authors that these phenomena can be efficiently described using ray-tracing in conjunction with bulk estimations of the refractivity profiles based on the Monin-Obhukov theory. In this paper, the accuracy of bulk methods to describe ray bending is assessed by examining angular deviations of apparent target elevations with respect to the meteorological conditions. Prediction accuracy is shown for a large spectrum of conditions, characterized by the air-sea temperature difference, by combining measurements collected in the North Sea and in the Baltic Sea. Moreover, the use of bulk profiles as opposed to profiles measured at sea by using a buoy is discussed.