RELATIVE INCIDENCE PROPAGATION CONDITIONS OVER SOME SELECTED LOCATIONS IN NIGERIA

Abstract

Relative incidence propagation conditions are important parameters in the study of clear air propagation and interference phenomena. Thus, the existence of non-standard refractive propagation conditions (ducting, super and sub refraction) provide valuable information about the propagation of radiowaves in the lower atmosphere. Relative incidence conditions are functions of refractivity gradient deduced from the atmospheric parameters (temperature, relative humidity and pressure). This research investigates the relative incidence propagation conditions across the climatic regions of Nigeria. Eight years (2010-2017) of atmospheric parameters were obtained from the Era-Interim archive of the European for Medium-Range Weather Forecasts (ECMWF). These atmospheric parameters were computed to evaluate the radio refractivity, refractivity gradient and relative incidence at three different altitudes (0.1 km, 0.5 km and 1.0 km) for two synoptic hours of the day (00:00 and 12:00 UTC). The atmospheric parameters at the surface, and at 0.1 km, 0.5 km and 1.0 km altitudes across the climatic regions of Nigeria at resolution of 0.25o × 0.25o were computed using the Matlab to carry out the seasonal and annual variations of the refractivity gradients and relative incidence at all the 16 locations in Nigeria. Relative incidence is deduced from the probability at which the refractivity gradient value is less than or equal to -100 N-units/km. The result showed that the values of radio refractivity, refractivity gradient and relative incidence vary spatially and temporally across the 16 selected locations in Nigeria. This research will aid the radio engineers in deciding the system performance in terrestrial communication links across Nigeria.