Advances in Research

The variation of refractivity with height is of major importance in controlling the path                                       of propagation of radio wave in the troposphere. The variation which leads to                                      anomalous propagation such as sub refraction, super refraction and ducting on terrestrial                            paths is of great importance for microwave links. In this paper, 5-year (2009 – 2013) data of climatological parameters like pressure, temperature and relative humidity among others,                                at the ground surface and at the first 100 m altitude over five locations across Nigeria (Akure,              Minna, Enugu, Jos and Sokoto) are analysed to ascertain their impact on microwave communication links in Nigeria. The analyses involved the influence of refractivity gradient and k-factor on the season of the year as well as their implications on microwave communication systems. The results revealed that different locations have different average values of k-factor in different seasons of the year. Hence, we can conclude that the fixed value of 1.33 recommended by the ITU may either underestimate or overestimate k-factor value in Nigeria. The overall results also show a        common occurrence of sub-refraction in the arid region and super-refraction in the coastal region of Nigeria.