Impacts of Climate Change on Ecosystem Services of Agroforestry Systems in the West African Sahel: A Review

Author(s):  
Kapoury Sanogo ◽  
Djibril S. Dayamba ◽  
Grace B. Villamor ◽  
Jules Bayala
2021 ◽  
pp. 1-42

Abstract The West African monsoon (WAM) is the dominant feature of West African climate providing the majority of annual rainfall. Projections of future rainfall over the West African Sahel are deeply uncertain with a key reason likely to be moist convection, which is typically parameterized in global climate models. Here, we use a pan-Africa convection permitting simulation (CP4), alongside a parameterized convection simulation (P25), to determine the key processes that underpin the effect of explicit convection on the climate change of the central West African Sahel (8°W-2°E, 12-17°N). In current climate, CP4 affects WAM processes on multiple scales compared to P25. There are differences in the diurnal cycles of rainfall, moisture convergence, and atmospheric humidity. There are upscale impacts: the WAM penetrates farther north, there is greater humidity over the north Sahel and the Saharan heat low regions, the sub-tropical subsidence rate over the Sahara is weaker, and ascent within the tropical rain belt is deeper. Under climate change, the WAM shifts northwards and Hadley circulation weakens in P25 and CP4. The differences between P25 and CP4 persist, however, underpinned by process differences at the diurnal and large-scales. Mean rainfall increases 17.1% in CP4 compared to 6.7% in P25 and there is greater weakening in tropical ascent and sub-tropical subsidence in CP4. These findings show the limitations of parameterized convection and demonstrate the value that explicit convection simulations can provide to climate modellers and climate policy decision makers.


2020 ◽  
Vol 33 (8) ◽  
pp. 3151-3172 ◽  
Author(s):  
Rory G. J. Fitzpatrick ◽  
Douglas J. Parker ◽  
John H. Marsham ◽  
David P. Rowell ◽  
Francoise M. Guichard ◽  
...  

AbstractExtreme rainfall is expected to increase under climate change, carrying potential socioeconomic risks. However, the magnitude of increase is uncertain. Over recent decades, extreme storms over the West African Sahel have increased in frequency, with increased vertical wind shear shown to be a cause. Drier midlevels, stronger cold pools, and increased storm organization have also been observed. Global models do not capture the potential effects of lower- to midtropospheric wind shear or cold pools on storm organization since they parameterize convection. Here we use the first convection-permitting simulations of African climate change to understand how changes in thermodynamics and storm dynamics affect future extreme Sahelian rainfall. The model, which simulates warming associated with representative concentration pathway 8.5 (RCP8.5) until the end of the twenty-first century, projects a 28% increase of the extreme rain rate of MCSs. The Sahel moisture change on average follows Clausius–Clapeyron scaling, but has regional heterogeneity. Rain rates scale with the product of time-of-storm total column water (TCW) and in-storm vertical velocity. Additionally, prestorm wind shear and convective available potential energy both modulate in-storm vertical velocity. Although wind shear affects cloud-top temperatures within our model, it has no direct correlation with precipitation rates. In our model, projected future increase in TCW is the primary explanation for increased rain rates. Finally, although colder cold pools are modeled in the future climate, we see no significant change in near-surface winds, highlighting avenues for future research on convection-permitting modeling of storm dynamics.


2010 ◽  
Vol 11 (S1) ◽  
pp. 119-125 ◽  
Author(s):  
Keffing Sissoko ◽  
Herman van Keulen ◽  
Jan Verhagen ◽  
Vera Tekken ◽  
Antonella Battaglini

2021 ◽  
Vol 39 ◽  
pp. 103110
Author(s):  
L. Champion ◽  
N. Gestrich ◽  
K. MacDonald ◽  
L. Nieblas-Ramirez ◽  
D.Q. Fuller

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