Abstract
African society is particularly vulnerable to climate change. The representation of convection in climate models has so far restricted our ability to accurately simulate African weather extremes, limiting climate change predictions. Here we show results from climate change experiments with a convection-permitting (4.5 km grid-spacing) model, for the first time over an Africa-wide domain (CP4A). The model realistically captures hourly rainfall characteristics, unlike coarser resolution models. CP4A shows greater future increases in extreme 3-hourly precipitation compared to a convection-parameterised 25 km model (R25). CP4A also shows future increases in dry spell length during the wet season over western and central Africa, weaker or not apparent in R25. These differences relate to the more realistic representation of convection in CP4A, and its response to increasing atmospheric moisture and stability. We conclude that, with the more accurate representation of convection, projected changes in both wet and dry extremes over Africa may be more severe.
Highlights
African society is vulnerable to climate change
R25, CP4A and CMORPH all show a similar spatial variation in the wet season to TRMM, there are discrepancies over northern Africa and neither model captures the variation between March–April–May (MAM) and October–November–December (OND) across East Africa
Some future changes in wet season are seen in both models: over West Africa, the wet season is typically shifted 1-month later, consistent with previous studies[11]; over southern Africa, it is shifted 1-month earlier and over the Horn of East Africa, there is a shift from MAM to OND as being the wettest period in the future, shown to relate to a slower retreat of the Intertropical Convergence Zone (ITCZ) southwards[22]
Summary
African society is vulnerable to climate change. The representation of convection in climate models has so far restricted our ability to accurately simulate African weather extremes, limiting climate change predictions. Convection parameterisation schemes often produce very intermittent rainfall at the model time step[3], rainfall too early in the day[4], and fail to capture organised propagating systems, instead simulating unrealistically widespread light daily total and insufficient heavy rain[5] Such deficiencies can have a significant impact on the regional scale circulation and water cycle over Africa[6,7] and the response of storms to their environment[8]. For the first time we analyse multi-year climate-change projections for an Africa-wide domain at convection-permitting (4.5 km) resolution (CP4A) This builds on an earlier study[19] that described the CP4A experimental design and provided the results from the first 5 years of the present-day simulation. We conclude that changes in extreme rainfall and dry spells over Africa may be underestimated in all models where convection is parameterised
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