Evolutionary drought patterns over the Sahel and their teleconnections with low frequency climate oscillations

Abstract The need for ideal drought metrics to explore the impacts of climate variability drivers on drought intensity and characteristics is essential to provide support that leads to optimizing existing templates on risk mitigation in drought-prone regions. The main aim of this study therefore is to improve contemporary understanding on the evolutionary patterns of historical drought over the Sahel (1901–2014) and the large-scale processes that drive its variability using the SPEI (standardized precipitation evapotranspiration index) and SPI (standardized precipitation index). Historically, the distributions of SPEI and SPI are generally quite similar with fairly strong correlations ranging from 0.80 to 1.0 around the central Sahel. The dissimilarity between SPI and SPEI in some regions however, suggest the influence of changing land surface conditions and the need to incorporate biophysical indicators to support the accounting process that aid the understanding of drought impacts and its cascading effects. Furthermore, SPEI and SPI confirm that the worst drought during the 20th century over the Sahel occurred between 1982 and 1985, affecting more than 90% of the region while the 1950s remained the wettest on record. However, between 2005 and 2015, drought episodes and their intensities have diminished over the Sahel. In the assessment of the coupled relationship of seven climate modes with drought evolutions, SPEI was more associated with Atlantic Multi-decadal Oscillation-AMO (r = 0.66) and Pacific Decadal Oscillation (r = − 0.53) unlike the SPI. A predictive multivariate model confirms the AMO is a strong driver of drought events and in addition, highlights the multi-scale climate influence in the Sahel.