2015: Why it rained in November — Expert

Although rainfall in Nigeria varies across regions, the raining season which often begins around March is expected to last till September, with a peak period at mid October. In recent times, however, the pattern of the season seems to have changed.
Speaking on what could be responsible for the prolonged rain till November this year, Dr Matthew Olaniran, a research fellow at the Climate Impact Studies, Institute of Ecology and Environmental Studies, Obafemi Awolowo University (OAU), opined that although one cannot really tell what is responsible for the prolonged length of rainfall this year, the sharp departure from what we used to have, particularly in recent years, could be normal inter-annual variability, that is a change in rainfall pattern from one year to another.
“The change in annual rainfall is a function of many processes such as change in sea surface temperature, strength of the South-East trade wind, which brings moisture/rainfall across the Atlantic Ocean, or weakness of the North-East trade wind, that is the wind system that brings harmattan from the Sahara. If these changes persist in the years to come and there is no tendency to return to what it used to be, then these are consequences of climate change.”

Noting that this has been predicted to happen in recent published researches, Dr Olaniran said that the effects of these changes on the environment could be both positive and negative.
“It can be positive for production of some arable food and cash crops due to the prolonged growing length, and it might be negative to some animals and plants, due to possible reduction in the dry season,” he said.
According to him, the length of the raining season is about eight to nine months in the southern parts of the country and four to five months in the north.
“Under warmer future climate, the length of the wet season is expected to be prolonged in the south but reduced in the north. It must be noted that the onset of the wet season is the day/period when nine to 10 per cent of the total rainfall for the year has fallen. During this period, the probability that it will rain within five days is usually greater than or equal to 0.5. The wet season ends when about 90 per cent of the total rainfall for the year has fallen. Therefore the end of the wet season is not the last day it rains in the year,” he said.