VERTICAL DISTRIBUTION OF ATMOSPHERIC ANOMALOUS PROPAGATION CONDITIONS IN COASTAL AREAS OF NIGERIA

Abstract

The vertical profile of temperature, moisture and pressure are mostly responsible for the way radio waves propagate in a given air layer (atmosphere). The atmospheric parameters among others is dynamic in nature hence there is a need to continuously assess their impacts on radio communication network which necessitated this study. In this study, ERA-INTERIM satellite data for six (6) different locations in the coastal areas of Nigeria; namely: Bayelsa, Cross-river, Lagos, Delta, Ondo and Rivers were used. Five years ERA-INTERIM satellite data was accessed from from January 2014 to December 2018 with 0.25 by 0.25 resolution was used in evaluating the vertical distribution of atmospheric anomalous propagation conditions at different altitudes for 110 m, 540 m and 988 m. The meteorological parameters for the locations were used to calculate the radio refractivity, modified refractivity and modified refractivity gradient at different altitudes. The result of this study shows that modified refractivity gradient values are generally high during the rainy season (April-October) and during the dry harmattan season (November - May), the values of modified refractivity gradient are generally low. The highest negative value of modified refractivity gradient G was notably observed 110 m above ground level (at pressure level 1000 hPa). Further result shows the occurrence of duct refraction is high at altitude110 m above the sea level. The degree of occurrence of ducting condition reduces with increasing altitude across the coastal locations. The occurrence of standard refraction propagation is more achieved at higher altitude and its noticed at altitude 988 m above the ground level. There is slight occurrence of sub- refraction condition at 110 m, it reduces with increasing altitude, which further disappears at 540 m and 988 m above the ground level across the coastal locations. This work would assist subsequent researches.