Drought monitoring using the Climate Hazards InfraRed Precipitation with Stations (CHIRPS) in Ethiopia

Abstract

Ethiopia has experienced numerous natural disasters, with 110 documented events that include floods, disease outbreaks, droughts, landslides, pest infestations, volcanic eruptions, earthquakes, mass movements, and wildfires over the past 58 years. Among these, drought occurrences are characterized by various factors such as duration, inter-arrival time, peak intensity, frequency, and severity. This study aims to monitor drought patterns in Ethiopia using the Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS-v2) satellite rainfall product. A 3 and 12-month timescale Standardized Precipitation Index (SPI) based on a gamma distribution was calculated to evaluate inter-arrival time, peak intensity, frequency, severity, and trends from 1981 to 2021. The performance of CHIRPS data was evaluated compared to gauging stations using the coefficient of determination (R²), root means square error (RMSE), and mean absolute error (MAE) and showed a good agreement was reached. Results reveal an increasing trend in drought across all seasons, including winter, spring, summer, and autumn. However, statistical analysis via the Mann-Kendall trend test indicates that these upward trends are not statistically significant, with computed p-values (0.335, 0.419, 0.384, and 0.207) exceeding the significance level of α ​= ​0.05. Temporal variations in drought indices reveal that certain years, such as 1984, 2010, and 2016, were among the driest periods in Ethiopia, both in terms of annual and seasonal drought severity. In contrast, 1998, 2007, and 2020 were identified as the wettest years and seasons in the country. The SPI-12 monthly index drought characterization shows an average of 4 drought events per year, with a maximum drought duration of 45 months, a maximum magnitude of 80, a frequency of 18%, and a severity of 2.6. The findings highlight the significance of advanced satellite data in accurately characterizing drought conditions, vital for strengthening the country's capacity to adapt to climate variability. By incorporating these insights into national planning and resource management frameworks, Ethiopia can enhance its ability to protect ecosystems, ensure food security, and maintain overall socio-economic stability in the face of the growing threat of drought.