Variation of Surface Refractivity with Soil Permittivity and Leaf Wetness in a Tropical Location

Radio signal transmitting above the ground surface experiences attenuation as a result of absorption by vegetation and hydrometeors, refraction due to turbulence in weather parameters; and reflection from ground surface. In this study, attempt was made to compute surface refractivity from its constituent parameters, and investigate its variation with leaf wetness and soil permittivity, at seven (7) different stations across Ondo state, Nigeria. Data for the research were obtained by in-situ measurement using Davis 3125 Vantage Pro2 weather station having sensors for measuring temperature, pressure, relative humidity, leaf wetness and soil moisture content. Measurement was carried out round the clock at 10 minutes integration time for a period of two weeks at each of the study locations, and for each of rainy and dry seasons. The soil moisture content was obtained at 30cm soil depth while leaf wetness was measured by attaching its sensor directly to a projected leaf-branch; and surface refractivity was computed from pressure, temperature and humidity data. Correlation analysis was employed to measure the strength and direction of the relationship between surface refractivity and each of soil permittivity and leaf wetness. Across the locations, R ranges from 0.38 to 0.9; and 0.04 to 0.7 for rainy and dry season respectively. The value of R is statistically significant at all the stations during the rainy season and majority of the stations during the dry season; signifying that surface refractivity exhibits good spatial and temporal relationship with soil permittivity and leaf wetness across the stations albeit with varying intensities.