INFLUENCE OF SPECIFIC HUMIDITY ON SURFACE RADIO REFRACTIVITY OVER NIGERIA.

Abstract

In the transmission of radio wave through the atmosphere (the troposphere), radio propagation is affected by the changes of water vapour in the troposphere. This study utilized two years archived data (Jan. 2011-Dec. 2012) of atmospheric variables of temperature, pressure and relative humidity obtained for eight locations in Nigeria (Abuja 9O4’N, 7O29’E, Akure 7O10’N, 5O05’E, Jos 9O10’N, 9O45’E, Lagos 6O35’N, 3O45’E, Markurdi 7O43’N, 8O32’E, Minna 10O00’N, 6O00’E, Nsukka 6O30’N, 7O30’E and Port-Harcourt 4O45’N, 6O50’E). Data for this work was obtained from Tropospheric Data Acquisition Network (TRODAN) of the Centre for Atmospheric Research (CAR) located at the campus of Kogi State University Anyigba, Kogi State. CAR is a subsidiary of the National Space Research and Development Agency (NASRDA). The data obtained was used to determine the specific humidity from available relative humidity data. Radio refractivity at the ground surface was also computed and the correlation between specific humidity and radio refractivity was deduced. The spatial patterns of specific humidity and radio refractivity over the study locations were also mapped out showing its trends. The results show that throughout the entire stations, an average of 309.60 N-unit for radio refractivity was observed in the year 2011 and 316.51 N-unit for 2012, and for specific humidity for the year 2011 was observed to be 0.45049 and 0.4572 for 2012. The results show increasing trends in specific humidity in the coastal regions as compared to the inland regions, a reason for which more energy is needed for radio wave propagation. Spatially, the increasing trends in specific humidity are more coherent in the rainforest climatic condition of the country.