Journal Article

Study of Surface Refractivity Over Lapai and Makurdi (North-Central) Nigeria

Abstract

This paper studied the diurnal and seasonal variations and the tropospheric surface refractivity (Ns) over Lapai and Makurdi (8.82o N, 6.68o E and 7.74o N, 8.51o E), Central part of Nigeria. The results indicated that both the hourly and monthly averages of radio refractivity during the rainy season months (April to October) are greater than the Ns values of the dry season months (November to March) for the two locations and years of the study. The computed mean diurnal Ns over Makurdi and Lapai in the first 1 km are respectively 343 and 342 N-units, which respectively give the refractivity gradients (dN/dh) of -47 N/km and -46 N/km; this shows that the stations are, on average, characterised by low scale super-refraction. The mean k-factor over the two regions in the first 1 km is 1.4. The mean Field Strength Variability (FSV) in first 1 km in the region is 14 dB. The mean Radio Horizon distance within 1 km height for a transmitter height of 100 m over the stations is 42 km. Diurnal and seasonal Ns variations in Makurdi and Lapai were shown using 2-D contouring. The refractivity shows a seasonal variation with higher values in the rainy season and lower values in the dry season and it can be concluded that refractivity varies according to height above the over sea-level from one station to another

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