Assessing current and future spatiotemporal precipitation variability and trends over Uganda, East Africa, based on CHIRPS and regional climate model datasets

Abstract

The lack of reliable rainfall projection records remains a major challenge to Uganda. In the advent of extreme wetness or drought events, reliable rainfall estimates for local planning and adaptation are essential. The present study used two main datasets to conduct a historical analysis from 1981 to 2019, coupled with future projections under representative concentration pathway (RCP 8.5) for the period 2020-2050. Historical analysis revealed bimodal annual rainfall pattern for March-May (MAM) and September-November (SON) gradients representing heavier to lighter rainfall events respectively over the study area. Investigation of recent trends in rainfall patterns revealed an upward trend from 2010 onwards in annual and seasonal rainfall. Moreover, results for future projections show wet conditions are projected to occur over the study area between the months of April/May and October. Contrarily, March is likely to experience a reduction in wet conditions. Mann-Kendall test employed to make future projections of rainfall depicted decreasing patterns during MAM season whilst increasing tendencies with strong shift was highlighted for SON season over the study region. Meanwhile, annual projections indicate huge variations with linear trends showing a marginal increase as compared to historical trends. Findings would serve as baseline print to propel further studies

Mechanisms associated with September to November (SON) rainfall over Uganda during the recent decades

“…v2) blends 0.05° resolution satellite imagery with in-situ measurements toproduce a gridded value from 1981 to present. CHIRPS has been evaluated and utilized by a number of studies over East Africa (Dinku et al, 2018;Ayugi et al, 2019;Ngoma et al, 2021).…”

“…This has posed pronounced consequences on the population. Past studies have reported an observed decrease in rainfall during MAM season and an increase during SON (Nsubuga et al, 2014;2017;Egeru et al, 2019;Ngoma et al, 2021). Nevertheless, SON rains have exhibited higher interannual variability as they are reported to be more influenced by global teleconnections (Saji et al, 1999;Ongoma et al, 2015).…”

Water availability trends across water management zones in Uganda

“…Nevertheless, the entire country was considered in a few other studies such as Ngoma et al . (2021), Kisembe et al . (2019), Jury (2018), Onyutha (2016a), and Nsubuga et al .…”

“…Examples of such products include Global Precipitation Climatology Project (GPCP) (Adler et al ., 2018), Princeton Global Forcing (PGF) (Sheffield et al ., 2006), Climate Forecast System Reanalysis (CFSR) of the National Center for Environmental Prediction (NCEP) (Saha et al ., 2014), Climate Research Unit (CRU) Time series version 4.0 (Harris et al ., 2020), and Climate Hazards group Infrared Precipitation with Stations (CHIRPS) (Funk et al ., 2015). A number of recent studies (Hua et al ., 2019; Alfaro et al ., 2020; Martinez‐Cruz et al ., 2020; Mubialiwo et al ., 2020; 2021b; Ngoma et al ., 2021; Onyutha et al ., 2021) have made use of the reanalyses and/or satellite products. The increasing use of satellite or reanalyses products is largely attributed to their global coverage, fine spatial and temporal resolutions, and long‐term record periods.…”

“…Nevertheless, the entire country was considered in a few other studies such as Ngoma et al (2021), Kisembe et al (2019), Jury (2018), Onyutha (2016a), and Nsubuga et al (2014). However, even with the establishment of catchment management planning guidelines (Ministry of Water and Environment, 2014), country-wide studies conducted after 2014 (Onyutha, 2016a;Jury, 2018;Kisembe et al, 2019;Ngoma et al, 2021) did not consider differences in the hydro-climates of the various WMZs. Besides, some of the past studies (Onyutha, 2016a;Jury, 2018) analysed changes in precipitation only.…”