Study on Distribution Characteristics of Evaporation Duct for Electromagnetic Wave Propagation

Abstract

Evaporation duct widely exists in the ocean, which has an important impact on shipborne electronic equipment. The application of an evaporation duct requires mastering the distribution characteristics of an evaporation duct. Based on the ERA-Interim surface data released by ECMWF from 2011 to 2015, the P-J evaporation duct model is used to analyze the distribution of global evaporation ducts. It is concluded that the average height of the evaporation duct is zonally distributed, which can be divided into seven zones, from low to high latitudes, the lower-value zone of the tropical convergence zone, the high- value zone of the north trade wind zone, the high-value zone of the south trade wind zone, the transition zone of the northern hemisphere, the transition zone of the southern hemisphere, the low-value zone in northern hemisphere and southern hemisphere; the height of the evaporation duct is relatively low on the cold current areas, and relatively high on the warm current areas; the evaporation duct has not only geographical variation but also seasonal variation. The seasonal variation in the location of the lower value zone of the tropical convergence zone are roughly the same as that of the equatorial convergence zone. It is located at the southernmost point in February and the northernmost point in August. The location of high-value areas of trade wind has the same seasonal variation. The height of the evaporation duct in high-value areas of trade wind is higher in the season with relatively strong trade wind and low relative humidity, and lower in the season with relatively weak trade wind and high relative humidity.