Abstract
M.Sc. (Geography)
In this study the spatial and temporal variation of radio-refractivity over southern Africa is investigated. Climatological data from 8 upper-air stations and 49 surface stations were used and transformed. into values of refractivity to establish a data base of radio
refractivity information.
The spatial analysis yielded maps of surface refractivity (Ns ) and height corrected surface refractivity (No) for southern Africa. In order to calculate the height correction factors, a radio-climatological classification of southern Africa was drawn: up. These maps are a refinement of the existing maps published by the CSIR. The temporal analysis consisted of graphs of mean monthly and yearly values of various refractivity- (Ns, Delta N, K-factor) and climatological (temperature, vapour pressure) factors for the eight upper-air stations. Some preliminary information about ducting was also obtained from this analysis. A spatial-temporal analysis of limited extent was then performed for one station to obtain an indication of the factors leading to the formation of radio ducts, as well as the actual variation of refractivity with height.
Information about the variation of refractivity over southern Africa was thus obtained, with emphasis on macroscale variation as well as preliminary information about ducting conditions.