Assessing characteristics of dry spells over central Uganda
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Agriculture is a major economic activity in Uganda, however it is affected by different Climate and Weather Extremes. These weather extremes include rainfall extremes, floods, droughts and dry spells. Dry spells are some of the major extremes affecting the agricultural sector as these spells create water shortages leading to low yields, famine, and hunger. Dry Spells affect other sectors like hydrology, transport and communication, health and can cause a permanent damage to the economy of Uganda. To cope up with the uncertain weather extremes because of the short time scale weather variations in Uganda, this research focuses on assessing some of the dry spell characteristics (drought and frequency) in the projected future years by CORDEX enforced under the Representative Concentration Pathways (RCP) 4.5 and 8.5 The main objectives focused on durations of dry spells and their frequencies in the next 2, 5, 10- and 20-year return period for the projected years 2021 to 2050 and how the percentage increase in the duration in the course of those years might affect Uganda’s major economic activity. Since dry spells are directly dependent on the amount of rainfall received in an area and the rain days. Assessing a relationship between the past dry spells and future projected spells was done. To achieve these objectives, the Annual Maximum Series and Peak Over Threshold method under the Extreme Value Theory (Extreme Package) in R Studio program was used. For Annual Maximum Series, the maximum number of dry days under the Generalized Extreme Value were fitted by the Maximum Likelihood Estimation and L Moments while for Peak Over Threshold, the mean number of dry days are fitted under the same parameter estimation to give the duration lengths of dry spells for the 2,5,10 mad 20-year return periods. This was carried out for regions Masaka, Entebbe and Kampala. (Central Uganda) In Conclusion, the duration of dry spells for the future projected year under the different return periods increased especially Kampala as opposed to Entebbe and Masaka. In the next 20 years, Kampala’s dry spell duration increased by 52% under RCP 8.5 and 15% under RCP 4.5. While Entebbe and Masaka by 42%and 26% respectively under the Representative Concentration Pathways 8.5. There was no relationship between the future projected dry spells and the past dry spells because of the differences in the variations of rainfall over different periods of time. Most research showed that rainfall increased over Uganda in the future while some objected. A decrease or increase in rainfall days and amount contributed to the number of dry days experienced within a given period of time. Because of the significant increase in the length of dry spells as projected, Uganda’s Agricultural Systems needs proper planning, adaptation and solutions like irrigations, planting drought resistant crops to cope with the impacts of dry spells like famine, hunger and water shortages.