Characteristic temporal variability and trend of annual rainfall series in Port Harcourt Nigeria, a tropical coastal location

Abstract

Rainfall analysis over a locality provides useful information for sustainable water resources management over such an area. The paper is designed to examine the temporal variability of annual rainfall amount in Port Harcourt, Nigeria. Using monthly rainfall amount for a period of 41 years, Standardized Precipitation Index (SPI) and other statistical tools were used to evaluate anomalies in the annual rainfall amount for Port Harcourt, Nigeria during 1972 to 2012. Simple statistical techniques were used to evaluate the trend and rainfall variability index over the period of the study. The trend in rainfall series is statistically defined by the function Y = 2.180x + 2392, indicating an increase of 2.180 mm per year. The year 1993 recorded the highest SPI value of +3.369 while the lowest SPI was -1.420 recorded in 1983. The city witnessed sequences of distinct cycles of wet and dry spells with dominant dry spells. The SPI values present mild to severe anomalies from the normal. The Port Harcourt annual rainfall series requires effective monitoring in such a manner that timely warnings and swift response actions are provided in the run–up to the occurrence of those extreme events and their associated risks and damning consequences. These are necessary to guarantee effective risk reduction and management in the area.