Quantification of historical drought conditions over different climatic zones of Nigeria

The impact of extreme climate such as drought and flooding on agriculture, tourism, migration and peace in Nigeria is immense. There is the need to study the trend and statistics for better planning, preparation and adaptation. In this study, the statistical and temporal variation of climatic indices Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) was computed for eighteen (18) stations covering four climatic zones (Sahel, Midland, Guinea Savannah and Coastal) of tropical Nigeria. Precipitation, minimum and maximum temperature from 1980 to 2010 obtained from the archives of the Nigerian Meteorological Services were used to compute both the SPI and SPEI indices at 1-, 3- 6- and 12-month timescales. The temporal variation of drought indices showed that droughts were more prominent at 6- and 12-month timescales. SPI and SPEI were found to be better correlated at longer timescales than short timescales. Predominant small, positive and significant trend across the region suggest an increasing trend due to climate change.