Abstract
Climate change has increased extreme weather events over the planet. The most robust changes in East Africa (EA) are for daily temperature and precipitation, where high-impact extreme values have become more common. The overall magnitude, seasonal distribution of precipitation and its inter-annual variability have been altered. East Africa experiences some of the most severe convective storms in the world. They can come without warning and are becoming more frequent. These changes present significant risks to the vulnerable developing EA nations. There is still limited knowledge regarding the past, present and future patterns of climate extremes in East Africa and understanding these characteristics of climate extremes at regional and local scales is critical in developments of early warning systems and adaptation strategies. Improvements in recent climate models have enhanced our ability to simulate climate variability and extremes, however there are still limitations in accurately simulating regional climate conditions. This study focuses on the analysis of daily precipitation, minimum, and maximum temperature characteristics, seasonal climatologies and their extremes using observed in situ data. In addition, this study assesses the capability of the Co-ordinated Regional Climate Downscaling Experiment (CORDEX) Rossby Centre Regional Climate Model - RCA4, Regional Climate Model (RCM), to simulate the observed climate of the EA region. This study demonstrates the evidence of extreme weather events as a result of climate change in EA, and explores expected future changes. The results show that the RCM can reasonably simulate the main features of weather patterns over the region and is able to realistically capture the observed climatological patterns with some slight bias. Extreme indices of temperature and precipitation are also reasonably well reproduced. However, RCA4 showed a poor simulation of temperatures, especially minimum temperature. Further results on extremes showed an increasing trend in intensity and frequency of extreme precipitation (RX90p; Annual total precipitation from days > 95th percentile and RX20 Count of days when precipitation ≥ 20 mm) and increasing warm extremes while cold extremes are decreasing. Potential future changes in temperature and precipitation extremes were evaluated based on downscaled RCA4 Global Circulation Models (GCMs). The simulated changes in these extremes are for years 2046–65 and 2081–2100 relative to 1981–2000 under the Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathways (RCP) 4.5 and 8.5 emissions scenarios. Increases (decreases) in warm (cold) extremes and increases in the frequency of intense precipitation events were projected. Also, long-term observed changes in precipitation extremes including correlations to climate indices/large scale oscillations. Emphasis was on characterization of the changes in the extremes as such, as well as on understanding how they relate to changes in synoptic systems and teleconnections.