D. Buba¹, F.O. Anjorin^2,, A. Jacob³

Weather conditions are natural causes of visibility deterioration and increase in atmospheric extinction coefficient at a place. A 10- year dataset (1998-2007) of visibility and meteorological parameters such as Relative Humidity, Temperature and Atmospheric Pressure measured every 3-hour daily were analysed to examine the dependence of Atmospheric Extinction Coefficient, β_ext on seasonal meteorological conditions and synoptic weather patterns in Bauchi, a City in the North-eastern-Nigeria. From the visibility data obtained, the corresponding atmospheric extinction coefficient (β_ext) for the period under review was computed by using the Koschmieder relationship. In year 2000, when the Relative Humidity and atmospheric extinction coefficient, β_ext are highest, the temperature and visibility values are lowest. In 2003, when temperature (29.82°C) is highest, the Relative Humidity (42.52%) is lowest, although, the atmospheric coefficient was not at its lowest neither was the visibility (18.49km) at its highest. Of the years considered, year 2000 has the highest estimated atmospheric extinction coefficient, β_ext for both raining season and harmattan season. The raining season (June-September) has β_ext of 0.267 while the harmattan season has β_ext of 0.689. Their respective decadal mean for both raining season and harmattan season for the period under review are 0.205 ± 0.036 and 0.689±0.133.

atmospheric extinction coefficient, weather, visibility, Bauchi