EFFECT OF HUMIDITY ON REDUCED-TO-SEA LEVEL VALUE OF SURFACE RADIO REFRACTIVITY OVER NIGERIA

Abstract

Surface meteorological parameters obtained from the archives of Tropospheric Data Acquisition Network (TRODAN) domiciled at the Centre for Atmospheric Research, Ayingba, a subsidiary of National Space Research and Development Agency, Abuja, Nigeria have been used to investigate the effect of humidity on reduced-to-sea level value of surface radio refractivity over six locations in Nigeria. Two years (January 2007-December 2008) data of temperature, pressure and relative humidity have been used for the study. The locations are Akure (5.18 0 E, 7.17 0 N), Port-Harcourt (7.01 0 E, 4.78 0 N), Nsukka (13.04 0 E,5.13 0 N), Markurdi (8.53 0 E, 7.73 0 N), Abuja (9.36 0 ,6.33 0 ) and Lagos (3.24 0 E, 6.27 0 N). The correlation between humidity and reduced-to-sea level value of surface radio refractivity was determined. Typical values for dry month of January, 2007 are 0.97 for (Port-Harcourt), 0.97 for Makurdi, 0.70 for Lagos, 0.91 for Nsukka, 0.96 for Abuja and 0.97 for Akure. From the result, a high correlation value was established between humidity and reduced-to-sea level value of surface radio refractivity throughout the months in all the locations studied. The results obtained also show higher correlation values during the rainy season when compared with that of dry season. Notably, Port-Harcourt has the highest annual average value of surface refractivity 417 N-units. While Akure has the lowest annual average value of surface refractivity 385 N-units when compared to the remaining locations. It was also established that reduced-to-sea level value of surface radio refractivity has higher values in the early hours of the day and late night hours.