Variation in Meteorological Parameters on the Tropospheric Radio Refractivity Over Lapai, Niger State, Nigeria.

Abstract

The study of radio refractivity has aroused considerable interest primarily because of its influence on radio wave communication in the lower atmosphere. There is little or no need to over emphasize the effects of the parameters concerned with this research, temperature, pressure, and relative humidity on the various weather conditions experienced in Lapai town, which is the study area. Various weather conditions experienced also have their features which bring about their effects on the weather. The fact that these parameters stated above are subject to fluctuation gives them this ability to cause variations in the weather. This change in the weather on the other hand has a great effect on the rate of propagation of radio signals. The aim of this work is to examine the variations in meteorological parameters (Temperature, Atmospheric pressure, and Relative humidity) on the surface radio refractivity ‘N’ in Lapai town, Niger state of Nigeria, with focus on the wet and dry seasons. Lapai town is located within latitude 9º 02ʺ N and longitude 6º 34ʺ E. The Meteorological data were obtained from the Nigerian Meteorological Agency (NIMET), and used to compute the mean monthly refractivity for each month of the six years under review. The results obtained showed that the refractivity values are lower in the dry season months (January, February, November and December) due to lower relative humidity, as compared to the wet season months (March, April, May, June, July, August, September and October), which are characterized by higher refractivity values, and it could be attributed mainly to high relative humidity values. The result also indicated that month of January for the year 2018 has the minimum refractivity value of 325 N-units, while the month of April, 2018 with N value of 444 N-units has the maximum value of refractivity. The k-factor obtained from the radio refractivity gradient (RRG),[ dN dh] was used to establish the fact that the study area has been found to be super refractive during both seasons, with values of 1.5 and 1.87 for dry and wet seasons respectively. The results provide useful information needed by radio engineers to set up new terrestrial radio propagation links or to improve on the existing ones especially at VHF, UHF in Lapai, as recommended by ITU-R. The research therefore concludes that meteorological parameters put into focus for this work contribute noticeably to the radio refractivity, and subsequently the k-factor of Lapai, therefore, it affects the radio wave propagation. It has also established the fact that there exists a significant variation in the wet and dry season refractivity, with dry seasons having lesser N values due to low relative humidity as the major driving force. More so, the wet seasons are characterized by higher refractivity values due to higher values of relative humidity. Consequently, both seasons for the study area have been found to be super refractive, with the wet season having an increased super refractivity as compared to the dry season.