Diurnal Variation of Surface Radio Refractivity over Sokoto, North-western Nigeria

Abstract

The knowledge of good refractivity profile is vital for proper planning of terrestrial communication links; surface refractivity profile of a station is particularly required for enhanced planning and prediction of performance of terrestrial radio links especially in tropical regions where International Telecommunication Union Recommendations (ITU-R) has called for such local propagation data. The diurnal surface radio refractivity Ns over Sokoto was investigated for a period of three years (2008-2010). High values of Ns were recorded in the early morning hours while low values were recorded during afternoon hours. The least mean hourly Ns varied between 270-280 N-units in January (a typical dry season month in Sokoto) while the mean maximum was recorded between 345-360 N- units in July (a typical rainy season month). Also, average seasonal variation of Ns was 356-440 N-units in rainy season and 270-285 N-units in dry season. The result of this investigation also showed that relative humidity and temperature have major influence on the variation of surface radio refractivity, while pressure has relatively less influence. The study further showed that coverage of a radio transmitter of 200 m height may have a variation of up to 0.5 km between morning and afternoon hours in Sokoto.

Keywords

• refractivity
• temperature
• pressure
• relative humidity
• radio horizon