Sierra Leone Rainfall and Drought Dynamics from 1990-2020: A Holistic Perspective

The erratic weather pattern in recent years pose a great threat to human survival and livelihood in Sierra Leone. The rationale for this study was to determine rainfall variability and drought frequency occurrence in Sierra Leone from 1990-2020. The daily precipitation data were accumulated to obtain the monthly and annual precipitation extending over 30 years × 12 months × 2383 cell grids. Three metrics were used to determine drought and rainfall changes; Standard Precipitation Index (SPI), Drought Severity (DS) and Drought Intensity (DI). About eight SPI scales namely; (SPI-1, SPI-3, SPI-6, SPI-9, SPI-12, SPI-18, SPI-24, SPI-48) time series were computed. All statistical evaluations and visualizations were carried out using R Studio, version 4.0.3 (R Core Team, 2020). The highest annual rainfall ranges from 1000-4700mm with the west being the wettest region in Sierra Leone. The results showed that annual rainfall is less in the northeast as compared to the west and southern part of the country. A significant decline in precipitation was observed in 2009, 2003, 2004, 2005 and 2015 respectively. While 1992, 1993, 1994, 1995, 1996, 1997, 2008, 2010 and 2011 were observed as the wettest years. The study reveals that, drought incidence decreases contrariwise while duration linearly increases base on time scale. Drought characteristics and vulnerability risk differ across regions and was eminent across the northern province. The findings of this research can be enhance to mitigate future drought risk and helps in understanding the rainfall variability and pattern for agricultural productivity in Sierra Leone.