B. A. Cahoon and G. D. Thayer

Abstract:

Maps and charts are presented giving the world wide distribution and relative occurrence of ducting and superrefractive gradients of the radio refractive index for the atmospheric layer nearest to the surface. Areas with frequent occurrences of ducting gradients are shown to be found primarily in the tropics, with the highest incidence of over 75% being along the Gulf of Arabia. Large areas of the world have ducting incidences of less than 1%, primarily temperate oceans and artic and polar areas during the summer season. The effects of anomolous [sic] gradients in the surface layer of the atmosphere on radio horizon distances are discussed.

Keywords: ducting; radiosonde data; superrefractive

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