Abstract:
We assess the spatiotemporal characteristics of historical and projected future
drought over southern Ethiopia using the Standardized Precipitation Evapotranspiration
Index and the K-means clustering method. Historical assessment
is done for the period 1981–2018 while projected drought is analysed over two
consecutive future periods, that is, 2021–2060 (near future) and 2061–2100 (far
future). Projected drought events are identified under RCP 4.5 and 8.5 climate
scenarios based on three RCMs selected after performance evaluation. Modified
Mann–Kendall trend test is applied to determine trends and significance
at the 5% significance level. The results reveal broadly diverse and heterogeneous
spatiotemporal characteristics both over the historical and future
periods. Droughts of various frequencies, durations, and magnitudes are
observed amongst stations, while trends generally lack spatial coherence. The
year 1984 is noted to be the driest year in the historical period while the years
1982, 2009, and 1991 are with the driest March–May (MAM), June–August
(JJA), and September–November (SON) seasons, respectively. Compared to
the historical period, the frequency, magnitude, and duration of drought
events are projected to decrease in the near future and increase in the far
future. The frequency of drought events in SON and JJA seasons are projected
to increase in the near future and far future, respectively, under both scenarios.
More number of station shows a wetting tendency in the historical period
while more number of stations exhibit a drying tendency during the projected
future periods under the two scenarios. Since complex drought characteristics
are observed both in the historical and future periods, rigorous local-scale
drought monitoring and management is recommended.
