Diagnosis of circulation patterns influencing drought events for a period 1989 to 2018 over Uganda
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Droughts are considerable adverse climate events that have always caused large damage to both ecosystems and humans, and agriculture is usually the first economic sector to be affected. The study's main objective was to investigate the droughts events and the associated circulation patterns over different regions in Uganda and the specific objectives were analyzing the trends of drought occurrences and investigating the circulation anomalies associated with the droughts for a period 1989 to 2018. Characteristics of the events were analyzed in terms of intensity, duration, and frequency at different time scales. This provided insight not only into the historical perspective of anomalously dry and wet conditions but also into the long-term variation of climate in Uganda. The datasets used in this study included daily rainfall, temperature data obtained from CORDEX extracted for seven meteorological stations (Arua, Gulu, Soroti, Jinja, Kasese, Masindi, and Entebbe) spanning a period of 29 years from 1989 to 2018, monthly wind data from ERA-Interim reanalysis. Annual linear trends of drought over Uganda depicted positive linear trends at Arua, Kasese, and Soroti stations while negative linear trends were observed at Entebbe, Gulu, Jinja, and Masindi stations, Though, not statistically significant (P>0.05). Kasese district registered the highest number of extreme and severe drought events, followed by Gulu, Jinja, and Masindi, and the least being Entebbe. Linear trends at 500hPa pressure level within the seven districts were statistically significant (P≤0.05), however, at 850hPa pressure level, statistically significant trends were only observed at Jinja and Soroti districts. Generally, results for the relationship between circulation anomalies and drought events depicted a weak positive linear relationship throughout all the districts at both two pressure levels (500 and 850hPa) except for Masindi at (500hPa) and Kasese at (850hPa). This, therefore, leads to a partial rejection of the null hypothesis and that there is a relationship between drought events and associated circulation patterns over Uganda.