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.
Highlights
A reliable operation of ground-based communication systems for various purposes largely depends on the physical state of the atmosphere
The worked on the variation of tropospheric surface refractivity over Nsukka in the South-East, Nigeria and observed that surface refractivity is generally higher in the wet season than in the dry season as reported by [7]
The monthly mean of hourly surface radio refractivity over Sokoto were calculated using the meteorological data of temperature, pressure and the relative humidity collected from 2008-2010 with (2), whereas (3) and (4) were used to calculate the water vapour pressure and saturated vapour pressure
Summary
A reliable operation of ground-based communication systems for various purposes largely depends on the physical state of the atmosphere. The effects of the atmospheric parameters on the radio wave propagation can be observed from the study of radio refractive index, which varies considerably diurnally and seasonably in the tropics [3]. PHYSICSAccess waves and it is related to the distributions of vertical pressure, temperature and humidity in the atmosphere [5,6] These atmospheric constituents introduce propagation delay in troposphere signal transmission. The worked on the variation of tropospheric surface refractivity over Nsukka in the South-East, Nigeria and observed that surface refractivity is generally higher in the wet season than in the dry season as reported by [7]. Considering the atmospheric conditions of Sokoto, this research work investigates the diurnal surface refractivity variation over Sokoto, using diurnal atmospheric parameters, and determines the transition characteristics of radio signals between dry and wet seasons in the state
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