Abstract:
The significance of rainfall in agriculture and decision making processes such as water resource management cannot be over emphasized, therefore the present study is aimed at investigating the teleconnection between globally observed El Nino Southern Oscillation (ENSO) and/or La Nina and rainfall distribution over Nigeria. The study specifically investigated the impact of El Nino, La Nina, very strong El Nino and strong La Nina events on rainfall properties such as rainfall onset dates (RODs),rainfall cessation dates (RCDs), lengths of rainy season (LRSs), seasonal (JJAS) and annual rainfall (AnnR) amount compared to the neutral years.The data used comprises thirty-two years (1983 to 2014) of daily rainfall obtained from the archive of Nigerian Meteorological Agency (NiMET) for the thirty-eight climatic stations in Nigeria. The results indicated that very strong El Nino and strong La Nina episodes have significanteffects on rainfall properties compared to the neutral years.Most stations over the guinea zone are affected with delayed rainfall onset dates, early rainfall cessation dates and hence shorter lengths of rainy season during very strong El Nino compared to the neutral years. The effects on the savanna zone were moderate and those stations in the sahelian zone have the least effects. But there are some stations where RODs were later, RCDs earlier, LRSs shorter during very strong El Nino, while during strong La Nina, RODs were earlier, RCDs later and LRSs longer over the same stations. Similarly, seasonal (JJAS) and annual (AnnR) rainfall amounts were reduced significantly over the guinea zone, moderately over the savanna and the least effect over the sahel zone during very strong El Nino than strong La Nina episodes compared to the neutral years. Although, there are some cases where JJAS and AnnR rainfall amounts were less during very strong El Nino and more during strong La Nina over the same stations. A station likeIkeja(IKJ)was significantly influenced by very strong El Nino by having its onset delayed by 18 days, cessation earlier by 54 days, LRSs reduced by 72 days, JJAS
and AnnR rainfall amount reduced by 284 and 679 mm than during La Nina episodes compared to the neutral years.
