Rainfall extremes and trends during the little dry season in Nigeria

Abstract

The little dry season (LDS), a phenomenon of interest in West Africa is associated with a dry spell amid the wet season and is consequential to agriculture and global food production. However, the current literature suffers a knowledge gap on rainfall extremes and trends during this period. This study examined the rainfall extremes and trends during the LDS in Nigeria using daily and monthly rainfall data from 19 synoptic stations for the period 1960 to 2020. The Kendal tau correlation, Standardized Precipitation Index (SPI), and descriptive statistics were employed for the study. The result showed the LDS reduction from the western area eastward and northward. The LDS is more intense in August than in July and is characterized by drought, ranging from mild (74.34%) to extreme (2.64%). The droughts fluctuate with wet conditions. The severe and extreme drought was mostly confined to the southwestern area. Lagos observed the highest drought occurrences, 50% of below 10‐mm rainfall and prolonged dry spells. Shaki recorded 13.73% of the total severe droughts while Osogbo recorded 43.33% of extreme drought events. The mean SPI is majorly distributed in space as mild drought and mildly wet respectively, except for a few stations where it ranged from moderate to extreme. A significant trend was negative at Bida (p ≤ .01), positive at Iseyin (p ≤ .05), Abeokuta (p ≤ .01), and Akure (p ≤ .01) in July, and Bida (p ≤ .05) in August. The LDS period is associated with hardship through prolonged dry spells and drought. This study explains the extreme rainfall and trends during the LDS to water management and suggests agricultural planning, forecasting, and mitigation of drought impacts.