Spatial Analysis of Rainfall in the Climatic Regions of Nigeria using Insitu Data

Abstract

Analysis of rainfall trends is important in studying the impart of climate change for water resources planning and management. In this paper, the daily rainfall data of thirty-two (32) years (1982 - 2013) were obtained from the Nigeria Meteorological Agency (NIMET), Oshodi, Lagos for some stations across the climatic regions of Nigeria and these stations were further divided into four climatic regions according to their weather conditions such as Sahel savannah, Derived Savannah, Guinea Savannah and coastal regions. The rainfall pattern as well as its spatial distribution with air temperature through different months and years were observed and studied. The long time average of monthly and annual amounts of rainfall was calculated and analyzed. It was observed in the years of study statistically that highest mean rainfall of 193.38mm occurred in August at Sahel region, 215.99mm and 214.87mm in September at Guinea and Derived savannah regions respectively and 310.19mm in July at Coastal regions. Meanwhile, the average annual rainfall includes 590.831mm in Sahel, 1220.941mm in Guinea Savannah, 1381mm in Derived savannah and 1532mm in Coastal. It was observed that rainfall pattern below latitude $10^0$ is bi-modal in distribution having a primary peak in June-July and another secondary peak in September with little dryness in August. Finally, there is an increasing trend in rainfall amounts and frequency towards the middle of the wet season in all the regions in Nigeria.

Keywords: Spatial distribution, Climate change, Climatic regions, Rainfall and Air temperature.