Distribution of radio refractivity gradient and effective earth radius factor (k-factor) over Akure, South Western Nigeria

Refractivity gradient and k-factor variations, based on measurements of atmospheric pressure, temperature and relative humidity made in Akure North (7.15°N, 5.12°E), South Western Nigeria, is reported. The measurement was made using wireless weather stations (Integrated Sensor Suite, ISS) positioned at five different height levels beginning from the ground surface and at intervals of 50 m to a height of 200 m on a 220 m idled TV tower. The study utilised 2 years of meteorological data measured from January 2007 to December 2008 to calculate refractivity, its gradient and the effective Earth radius factor (k-factor). From the results, refractivity values were observed to be generally high during the rainy season (April–October) and the values decreased with increasing altitude. The average refractivity gradient was −52.8 N-units/km and the average value of k-factor is 1.51 for the 2 year period of this report.

► Mean surface refractivity for years 2007 and 2008 are 365 and 367 N-units, respectively. ► Mean refractivity gradient for 2 years is −52.8 N-units/km. ► Mean k-factor for 2 year period of measurement is 1.51. ► Microwave propagation in the Akure environment is mostly super-refractive.