Urban influence on relative-humidity and its corresponding effects on rainfall, a case study of Ibadan, Nigeria

Abstract

Urbanization is one serious process that transforms natural environment into various surfaces that have long run pronounced effects on the whole atmospheric system. For instance subjection of one time thick forest surface into concrete and asphalt surfaces greatly altered aerodynamic processes in the area, water balance system as well as evapo-transpiration process.As it is known that availability of moisture is one of the evidences of precipitation process. This paper explored urban effects on relative-humidity, through loss of moisture due to loss of water retention surfaces and as such intercepting water balance system which probably could influence rainfall occurrence in the area. The data for this paper are secondary data; in which mean monthly relative-humidity and mean monthly rainfall were collected across seven stations over the period of twenty years, (1989-2009). Data were analysed using Mean graph, Pearson correlation and Anova. The results showed that relative-humidity over time indicate increase in urban land surface transformation. Mean graph shows almost increase relative-humidity with time across the stations as well as rainfall, which indicate increase of relative-humidity with urbanization, as well as increase rainfall with increase relative-humidity. These validated both hypotheses. It is therefore concluded that urbanization increases relative-humidity and that relative-humidity has corresponding influence on rainfall.