SEASONAL AND DIURNAL VARIATIONS OF SURFACE RADIO REFRACTIVITY IN AKURE, SOUTH-WESTERN NIGERIA

Abstract

The surface meteorological data recorded at Akure (lat. 07° 17' N, long. 05° 14'E), in South-Western Nigeria are used to study the seasonal and diurnal variations of surface radio refractivity, Ns in this 'geographic zone. The Ns patterns for this geographic location are presented and these cover the two main seasons of the year: the rainy and the dry seasons. The percentage contribution of both the dry and wet terms to the total surface radio refractivity are also deduced. The seasonal and diurnal variations of No' the reduced-to-sea level form of Ns' have been compared with that of surface pressure, P, temperature, T and water vapour pressure, e. The comparison reveals that the No variations closely follow that of the water vapour pressure more than any of the other meteorological parameters. The monthly mean values of No have been computed for the rainy and the dry seasons at Akure. The average surface radio refractivity has been observed to be generally high in the rainy seaaon, while it reaches the lowest value in January, during obtained the peak of the dry season. The for Akure is about 378 N-units. mean value of iii Analysis of the experimental results shows that N~ variation at Akure has maximum value around 1900 hours local time.