Interconnection between Inter Tropical Convergence Zone Migration and Variation of Anomalous Radio Propagation in Tropical Region

Abstract

Seasonal cycle of radio refractivity aloft the tropical region have been studied in relation to the migration of the Intertropical Convergence Zone (ITCZ). Radio refractivity values were calculated from meteorological parameters obtained from the archive of the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim). ITCZ position is obtained using maritime and continental winds. Refractivity conditions of anomalous radio propagation were evaluated from refractivity using ITU-recommendation. Multilinear empirical model was developed from ITCZ position determinant factors and refractivity values. The performance of the model was evaluated against ITU-R values using standard metrics. The result showed that the values of refractivity gradient and the position of the ITCZ vary seasonally across Nigeria. ITCZ reached its maximum position northward in August with highest value of refractivity gradient ranges between − 100 N-units/km and − 50 N-units/km across the regions. with the movement of ITCZ across Nigeria. High values of refractivity gradient ranges between Southward position of ITCZ correlate with minimum position of refractivity gradient, which typified ducting. Ducting occurrence prevailed around the ITCZ position.