Accession Number : AD0288283

Title :   ON THE CLIMATOLOGY OF GROUND-BASED RADIO DUCTS AND ASSOCIATED FADING REGIONS

Corporate Author : NATIONAL BUREAU OF STANDARDS BOULDER COLO

Personal Author(s) : DUTTON,E.J.

Report Date : 16 JUN 1961

Pagination or Media Count : 1

Abstract : Maximum observed incidence of ducts was determined to be 13, 10 and 5% by analysis of 3 to 5 years of radiosonde data for a tropical, temperate, and arctic location, respectively. Annual maxima are observed in the winter for the arctic and summer for the tropics. Arctic ducts arise from ground based temperature inversions with the ground temperature less than -25 C; temperate zone ducts arise from radiation inversions and accompanying humidity lapse; while tropical ducts occur with slight temperature and humidity lapses when the surface temperat re is is 30 C and greater. The mean iniil elevation angle of a radio ray trapped by these ducts is found to be about 3 mr, with the maximum value about 5.8 mr. The steepest gradient of N observed is -420 N units/km. Observed ducts trap radio-waves of frequency higher than 1 kmc at all locations for at least 50% of the time. Fading regions arising from abnormal defocussing of radio-rays passing from an elevated antenna down through the duct to a ground-based receiver are analyzed. The horizontal extent of these regions is determined for the same arctic, tropic, and temperate conditions given above. (Author)

Descriptors :   *ATTENTION, *PROPAGATION, *REFRACTION, ATMOSPHERES, PERIODIC VARIATIONS, RADIO WAVES

Distribution Statement : APPROVED FOR PUBLIC RELEASE