Radio Superrefraction in the Coastal Regions of Australia

Abstract

A survey has been made of the incidence of radio superrefraction round the coast of Australia and nearby islands. It is based on the systematic reporting of the strengths of echoes from ground objects observed by Royal Australian Air Force 200 Mc/s. Radar stations. Observations taken hourly over periods of up to eighteen months have been analysed in terms of geographical position, season of year, time of day, and synoptic weather situations. The main points arising from the analysis are : (i) The frequency of occurrence of superrefraction at different times and places has been determined ; (ii) superrefraction is strongest and most regular in north-west Australia (occasional very long-range echoes occur in this region) ; (iii) superrefraction in coastal Australia is associated with one general condition, the offshore movement of a relatively warm and dry air mass ; and (iv) superrefraction on inland echoes is due almost exclusively to nighttime radiation inversions.