Investigations into the occurrence of evaporation ducts within the English Channel

摘要

Evaporation ducts are a particular type of atmospheric duct that predominantly exist over large sections of water. These ducts can cause anomalous propagation of radio signals. The most popular method of evaluating the height or strength of evaporation duct is the Paulus Jeske Method. This research provides analysis of annual, seasonal, monthly, daily and hourly trends of occurrence of evaporation ducts in English Channel. It is believed that such extensive insight into these ducts has not been provided before. The annual mean duct height is 7.3m. The seasonal trend shows higher values in autumn and lower in summer. Further analysis shows that occurrence of maxima is possible at any time of the year. Also, there are indications of enhancements in received signal levels due to the occurrence of evaporation ducts, despite the fact that dominant propagation phenomenon was diffraction. The findings of this study improve the understanding of over-sea propagation.