This review study examines the state of meteorological drought over Africa, focusing on historical trends, impacts, mitigation strategies, and future prospects. Relevant meteorological drought-related articles were systematically sourced from credible bibliographic databases covering African subregions in the twentieth and twenty-first centuries (i.e. from 1950 to 2021), using suitable keywords. Past studies show evidence of the occurrence of extreme drought events across the continent. The underlying mechanisms are mostly attributed to complex interactions of dynamical and thermodynamical mechanisms. The resultant impact is evidenced in the decline of agricultural activities and water resources and the environmental degradation across all subregions. Projected changes show recovery from drought events in the west/east African domain, while the south and north regions indicate a tendency for increasing drought characteristics. The apparent intricate link between the continent’s development and climate variability, including the reoccurrence of drought events, calls for paradigm shifts in policy direction. Key resources meant for the infrastructural and technological growth of the economy are being diverted to develop coping mechanisms to adapt to climate change effects, which are changing. Efficient service delivery to drought-prone hotspots, strengthening of drought monitoring, forecasting, early warning, and response systems, and improved research on the combined effects of anthropogenic activities and changes in climate systems are valuable to practitioners, researchers, and policymakers regarding drought management in Africa today and in the future.
This study estimates the total solar radiation potential over Nairobi City. Several theoretical models based on the initial work of Angstrom have been used to estimate the global solar radiations on a horizontal surface for the city, using bright sunshine hours for the period 2004–2014. The models were developed using the 2004–2012 sunshine hours data and validated by comparing with measured values for 2013 and 2014. Dependencies of the models were tested using Mean Bias Error, Root Mean Square Error, the Nash–Sutcliffe Equation and t-statistics. The result of clearness index for Nairobi shows that the sky is clear all year round except during the June-July-August season where KT is less than 0.5. Most models tested in the current studies were able to adequately estimate daily mean monthly global radiation from sunshine duration with Akinoglu and Ecevit model giving the best estimation.
Modifications in rainfall patterns may have significant effects on a variety of natural and human systems. This study evaluates the ability of 20 Coupled Model Intercomparison Project Phase 6 (CMIP6) to simulate the interannual variability of rainfall over East Africa (EA) using a method based on the empirical orthogonal function (EOF) analysis. The future changes in rainfall variability during the near (2021-2040), middle (2041-2060) and late (2080-2099) future are analysed under two different shared socioeconomic pathways (SSP), SSP2-4.5 and SSP5-8.5. Results reveal that most models captured better spatial climatological rainfall pattern than simulated amplitude in the EA region receiving bimodal rainfall pattern (EABM) compared to that with unimodal rainfall regime (EAUM) in the historical period. An ensemble mean of all models (AMME) and a set of 13 models that best simulated the rainfall variability in the base period were selected using a robust method based on the EOF analysis for further analysis. Most of the selected models and their ensemble mean (BMME) displayed good capability in representing the annual standard deviation (SD) in recent decades, whereas BMME corroborates AMME, particularly over the EABM and EAUM regions. Based on these findings, the AMME and BMME were used to evaluate the future changes in rainfall variability. The models project a significant increase in rainfall variability during March by the mid and late 21st century over the EAUM region under SSP5-8.5, whereas the increase appears much earlier in the near-future over the EABM region. In all future periods and SSPs, SD demonstrates a considerable increase over most of the EABM region, and the magnitude gradually increases from the AMME to BMME projections. Moreover, a relatively stronger increase is anticipated to actualize by the mid of 21st century.
The spatial–temporal characteristics of March–April–May rainfall are investigated over Lake Victoria Basin on a diurnal time scale using harmonic and principal component analyses. The study uses high‐resolution Tropical Rainfall Measuring Mission 3B42 V7 satellite estimate for the years 1998–2015. The diurnal signal in the initiation time for the land and the lake shows a difference in amplitude and phase with a peak in the late afternoon to evening over the land and late night to early morning over the lake. The rainfall maximum first appears over the highlands on the northeast of the lake around 1500 local standard time (LST) then intensifies and migrates westwards. Around 0300 LST the rainfall is observed ubiquitously over the lake before localizing in the western half of the lake around 1100 LST. There exists an enhanced rainfall amplitude of about 50% of the daily rainfall mean over the northeastern sector of the basin and the western half of the lake. By comparison, the amplitude of the semi‐diurnal cycle is weaker and in the range of 1–30% of the daily mean. Rainfall amount (RA) values are higher over the lake and the highlands on the east of the basin while lower on southeastern and western parts of the basin. The distribution of RA, rainfall intensity (RI) and rainfall frequency revealed high peak of RA over the eastern part of the basin that may be attributed to the high incidence of moderate rainfall. The peak over the western half of the lake may be ascribed to the enhanced RI over the lake.
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