Browsing by Author "Sabiiti, Geoffrey"

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    Empirical Relationships between Banana Yields and Climate Variability over Uganda
    (J. Environ. Agric. Sci, 2016) Sabiiti, Geoffrey; Ininda, Joseph Mwalichi; Ogallo, Laban; Opijah, Franklin; Nimusiima, Alex; Otieno, George; Ddumba, Saul Daniel; Nanteza, Jamiat; Basalirwa, Charles
    Variations in weather and climate have a significant impact on rain-fed banana yields in East Africa. This study examined empirical linkages between banana yields and variations in rainfalland temperature over Uganda for the historical period (1971-2009) using time series moments,correlation and regression analysis. The Food and Agriculture Organization (FAO) Crop Water Assessment Tool (CROPWAT) was used to estimate banana crop water requirements, soil moisturedeficits and their effects onbanana yield levels under rain-fed conditions for different regions. Thestudy observed high comparability in moment indices with some significant differences reflected in thevalues of the banana yields and rainfall and temperature moment indices. The cumulative effect ofrainfall and temperature variations on banana yields was discernible from strong correlationcoefficients of up to 78%. The CROPWAT simulations indicated up to 46% reductions in optimalbanana yields due to soil moisture deficits within banana plantations. In conclusion, the study observedstronger linkages between banana yields and temperature variations than rainfall. In addition,temperature manifests both direct and indirect effects on banana growth while rainfall exhibitscomparatively high intra-seasonal and intra-annual variability with lag effects on banana yields. Thestudy provides a strong scientific basis for the development of coping, adaptation and mitigationstrategies in the banana farming subsector in the region due to the anticipated shifts in rainfall and temperature extremes and changes across Uganda and neighbouring regions.
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    WRF Simulations of Extreme Rainfall over Uganda’s Lake Victoria Basin: Sensitivity to Parameterization, Model Resolution and Domain Size
    (Journal of Geoscience and Environment Protection, 2020) Opio, Ronald; Sabiiti, Geoffrey; Nimusiima, Alex; Mugume, Isaac; Sansa-Otim, Julianne
    Rainfall extremes have strong connotations to socio-economic activities and human well-being in Uganda’s Lake Victoria Basin (LVB). Reliable prediction and dissemination of extreme rainfall events are therefore of paramount im-portance to the region’s development agenda. The main objective of this study was to contribute to the prediction of rainfall extremes over this region using a numerical modelling approach. The Weather Research and Forecasting (WRF) model was used to simulate a 20-day period of extremely heavy rainfall that was observed in the March to May season of 2008. The underlying interest was to investigate the performance of different combinations of cumulus and mi-crophysical parameterization along with the model grid resolution and do-main size. The model output was validated against rainfall observations from the Tropical Rainfall Measuring Mission (TRMM) using 5 metrics; the rain-fall distribution, root mean square error, mean error, probability of detection and false alarm ratio. The results showed that the model was able to simulate extreme rainfall and the most satisfactory skill was obtained with a model se-tup using the Grell 3D cumulus scheme combined with the SBU_YLin micro-physical scheme. This study concludes that the WRF model can be used for simulating extreme rainfall over western LVB. In the other 2 regions, central and eastern LVB, its performance is limited by failure to simulate nocturnal rainfall. Furthermore, increasing the model grid resolution showed good po-tential for improving the model simulation especially when a large domain is used.