SEASONALITY OF RAINFALL IN SOUTH-WESTERN NIGERIA.

FAJEMIDAGBA, K.J., SAWA, B.A., ADELEKE, E.A. AND IBRAHIM, S.O.

Climate change seems to be the foremost global challenge facing humans at the moment. One of the challenges posed by change in climate is ascertainment, identification and quantification of rainfall and its implications on human activities. This study aimed at analyzing the effect of climate change on rainfall seasonality in south-western Nigeria. Data used for the study was monthly rainfall records of Lagos, Oyo, Ogun, Osun, Ondo and Ekiti state for the period 1983-2017 which was gotten from NIMET office at Oshodi. Walsh and Lawler (1981) method was adopted to calculate seasonality index while time domain Time Series Analysis and t-test were used to analyze the data of the study. The results of the study revealed that Lagos, Oyo, Osun and Ondo states experienced shortened spread of rainfall during the period of study while Osun and Ekiti experienced increase in spread of rainfall. In general, south-western Nigeria experienced a shortened spread of rainfall with rainfall occurring between 7-9months of the year during the period of study. Furthermore, t-test result showed that there is a significant difference in seasonality of rainfall in the region during the study period. It was concluded that the region experienced shortened spread of rainfall during the period of study. It was therefore recommended that during the periods of excess rainfall, water should be stored by government in dams while farmers and residents should store water in artificial reservoirs to cater for the shortage during the period of deficit.

Key words: Climate, Rainfall, Seasonality, South-western, Time series.