Spatiotemporal Variability of Drought and its Relationships to ENSO and IOD Indices in Somaliland

Abstract

Drought is one of Somaliland’s most prevalent natural hazards, causing serious socioeconomic and environmental harm. This study investigated the spatial and temporal variability of drought and its relationships with El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) indices using the Standardized Evapotranspiration Index (SPEI) from 1981 to 2020. The Mann-Kendall trend test and Sen's slope estimator were used to assess the trends of annual and seasonal SPEI time series. The Empirical Orthogonal Function (EOF) was employed to examine the dominant modes of the SPEI series, and Pearson and partial correlation analyses were performed to investigate the associations between significant modes of drought variability and ENSO and IOD indices. The results demonstrated a statistically significant downward trend of SPEI (increasing drought) at 99% confidence level. The EOF analysis indicated two spatially distinct zones of drought variability in the west and east of the country. Drought variability had a statistically significant negative correlation with ENSO in the summer and winter seasons, and with IOD in the winter season and annual time series. The findings of this study will provide important information for drought risk assessment, mitigation, and predictability in Somaliland.

Keywords: Drought, Standardized Precipitation Index, ENSO, IOD, Somaliland