This study analysed trends and variability in extreme precipitation and potential evapotranspiration (PET) indices across Uganda. We made use of daily precipitation and temperature datasets from 1979 to 2013 obtained from the Climate Forecast System Reanalysis (CFSR) products of the National Centres for Environmental Prediction (NCEP). The PET was estimated using the Hargreaves method based on the minimum and maximum temperature. Analysis was focused on the level of Water Management Zones (WMZs). Examples of the extracted extreme climatic indices included the annual maximum number of consecutive days with precipitation intensity < 1 mm/day (CDD1) or < 5 mm/day (CDD5), annual sum of PET for days with PET rate > 5 mm/day (SPETD5), and spell of high evaporative demand (or annual maximum number of consecutive days with PET > 5 mm/day) (CDPET5). Attributes of the variability in meteorological dry conditions were investigated. Trend and variability were investigated using an approach based on the cumulative sum of difference (CSD) between exceedance and non-exceedance counts of data points. The magnitudes of the linear decrease or increase in the precipitation and PET indices were determined using Sen’s method. To apply these methods, the CSD-based Sub (Trend) and Variability Analysis Tool (CSD-VAT) was used. The long-term mean of the extracted indices showed Kyoga and Victoria to be the driest and wettest WMZs, respectively. An increase in the number of dry days (indicating increasing severity of meteorological dry conditions) was confined to the Karamoja region or the eastern parts of the Upper Nile and Kyoga WMZs. However, the rest of the country generally experienced negative trends in the precipitation and PET indices. Extreme precipitation indices of Kyoga and the Upper Nile WMZs exhibited consecutive positive and negative sub-trends over the early 1980s and from 1985 to 2013, respectively. Victoria and Albert WMZs mainly exhibited negative sub-trends for both precipitation and PET indices especially from the mid-1980s to the end of the data. Across Victoria and Albert WMZs, we found that the variability in extreme precipitation indices such as CDD1 and CDD5 was significant (p<0.05). However, these WMZs were characterized by insignificant (p>0.05) variability of the PET indices such as SPETD5 and CDPET5. Changes in the precipitation and PET indices were significantly (p<0.05) found to be positively linked to the quasi-biennial oscillation. The meteorological drought indicators were significantly (p<0.05) negatively correlated with the Indian Ocean dipole and Atlantic multidecadal oscillation. Our findings based on NCEP’s CFSR data show that variation in sub-trends of the meteorological dry conditions across Uganda resonates well with the changes in some indicators of large-scale ocean-atmosphere conditions. This is important for planning predictive adaptation to the impacts of climate variability on water resources applications which are sensitive to the severity of meteorological dry conditions. Apart from our findings, we introduced a number of extreme PET indices which can be used for analysis of meteorological dry conditions or drought.


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    Title :

    Changes in Meteorological Dry Conditions across Water Management Zones in Uganda


    Additional title:

    KSCE J Civ Eng


    Contributors:

    Published in:

    Publication date :

    2022-12-01


    Size :

    20 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English







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