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Rainfall Trends And Variability
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1.4 AIM AND OBJECTIVES OF THE STUDY
The aim of this study is to investigate the changes in rainfall over Ibadan from 1982 to 2011. The specific objectives include:
To determine the monthly variation in rainfall from 1982 to 2011
To determine the annual variation in rainfall variation from 1982 to 2011.
To determine the biannual variation in rainfall from 1982 to 2011.
To predict the rainfall in Ibadan for the next 30 years.
1.5 HYPOTHESIS
i. There is a significant difference in monthly rainfall trends from 1982 to 2011.
ii. There is a significant variation in annual rainfall trends from 1982 to 2011.
iii. There is a significant difference in biannual rainfall trends from 1982 to 2011.
iv. There is an increase in the annual rainfall for the next 30 years.
1.6 STUDY AREA
1.6.1 Location
The city of Ibadan is located approximately on longitude 30 541 East of
the Greenwich meridian and latitude 70 231 North of the Equator at a
distance some 145kilometres North East of Lagos (Figure 1). Ibadan is
directly connected to many towns in Nigeria by a system of roads,
railways and air routes. The physical setting of the city consists of
ridges of hills that run approximately in northwest - southeast
direction. The largest of these ridges lies in the central part of the
city and contains such peaks as Mapo, Mokola and Aremo. These hills
range in elevation from 160 to 275 meters above sea level and thus
affords the vistor a panoramic view of the city.
Figure 1: Study Area: Ibadan, Oyo State.
1.6.2 Climate
Ibadan has a tropical wet and dry climate, with a lengthy wet season
and relatively constant temperatures throughout the course of the year.
Ibadan’s wet season runs from March through October, though August sees
somewhat of a lull in precipitation. This lull nearly divides the wet
season into two different wet seasons. The remaining months form the
city’s dry season. Like a good portion of West Africa, Ibadan
experiences the Harmattan between the months of November and February.
The tropical rainfall regime experienced in Ibadan is bi-modal,
convectional and follows the apparent movement of the sun while both
length of rainy season and the yearly total rainfall, decreases with
increasing distance from the equator. August is the coldest month and
coinciding with the August break while in December-January, the months
are noted for the dusty and cold harmattan winds conveyed from the
Sahara by the north- east trade winds.
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