Changes in length of rainy season and rainfall extremes under moderate greenhouse gas emission scenario in the Vea catchment, Ghana

Abstract

The economic implications of extreme climate changes are found to impact sub-Saharan Africa negatively. This study aimed to analyze projected changes in length of rainy season (LRS), and rainfall extreme indices at the Vea catchment, Ghana. The analysis was performed using high-resolution simulated rainfall data from the Weather Research and Forecasting (WRF) model under moderate greenhouse gas emission scenario for the period 2020–2049 relative to the 1981–2010 period. LRS was computed from the difference between rainfall onset and cessation dates, and its trends were assessed using Mann–Kendall test and Sen's slope estimator. Annual rainfall intensity and frequency indices were computed. Results showed an increase in mean LRS from 168 to 177 days, which was at a rate of 1 day/year in the future (2020–2049). The LRS increase would be more significant at northern and south-western parts of the catchment. Rainfall intensity and frequency indices are projected to increase at spatial scale across the catchment. Projected changes in rainfall extremes could increase the frequency and intensity of drought and flood events. Thus, it is necessary to integrate suitable climate change adaptation measures such as rainwater harvesting, flood control measures, and development of early warning systems in the planning process by decision-makers at the catchment.

Observed trends in timing and severity of streamflow droughts across global tropics

“…We present a detailed analysis of changes in the timing of lower-than-average precipitation and the shift in the timing of streamflow droughts across a few representative stations, which confirms the hypothesis that a shift in rainfall may drive the changes in the timing of droughts (figure S7 and table S10). Precipitation patterns in the tropics are strongly influenced by shifts in sea surface temperature changes (Trenberth 2011, Larbi et al 2021, Bochow and Boers 2023, whereas streamflow responses are often controlled by changes in evapotranspiration, antecedent soil water content, and land atmospheric feedback (Farrick and Branfireun 2014, Wendling et al 2019, Setti et al 2020. While a detailed investigation of these drivers in controlling streamflow drought onset and associated changes is beyond the scope of the present study, understanding such changes requires an extensive examination across different IPCC reference regions.…”