Seasonal variations of Radio Refractive Index Gradients over Minna in North central Nigeria

Abstract

Variations of radio refractivity with height up to 10 km atmospheric layer above ground over Minna (9o 37’’N, 6o 30’’E) have been evaluated. Five years Radiosonde data was used. The refractivity-altitude variation over Minna has also been compared with those of four low latitude stations: Addis Ababa, Ethiopia (9o 01’N); Khartoum, Sudan (15o 35’N); Mumbai, India (18o 57’N) and Nampula, Mozambique (15o 06’S). From the values of refractive index gradients computed, subrefractive condition was observed during the dry season while superrefractive condition was observed during the wet season periods over Minna. Also, an average value of 1.41 was calculated for the effective earth radius factor of the region.