Estimation of evaporation rate in Ilorin using penman modified equation

Abstract

Evaporation is a common occurrence in the atmospheric dynamics. This was studied in Ilorin (8°32' N, 4°34' E), by using five
meteorological parameter data collected from the Nigeria Meteorological Agency (NIMET) in Lagos Nigeria covering the period of
twenty years (1991-2010). These parameters include solar radiation, wind speed, relative humidity, rainfall and temperature. These
data were used to estimate the rate of evaporation using MATLAB 2013 to numerically simulate the penman equation modified by
Shuttleworth. The evaporation rate for dry months (November to March) was estimated to be 7.67mm/day with observed value of
7.74mm/day and evaporation rate in wet season which begins from April to October was estimated to be 2.90mm/day and the observe is 2.99 mm/day. The average rate of evaporation for the period of study was estimated to be 5.284692mm/day while the observed
value was calculated to be 5.362367mm/day, thereby giving a coefficient of determination R² = 0.99. A seasonal effect shows that
during dry season evaporation rate is high as compared to the wet season.