Effects of Explicit Convection on Future Projections of Mesoscale Circulations, Rainfall, and Rainfall Extremes over Eastern Africa
Effects of Explicit Convection on Future Projections of Mesoscale Circulations, Rainfall, and Rainfall Extremes over Eastern Africa
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DOI：
10.1175/jcli-d-19-0328.1
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发表时间：
2020-04-01
影响因子：
4.9
通讯作者：
Jackson, Lawrence S.
中科院分区：
文献类型：
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作者：
Finney, Declan L.;Marsham, John H.;Jackson, Lawrence S.
东非快速增长的人口容易受到降雨量变化和极端天气的影响。使用第一泛非洲气候变化模拟，明确模拟的对流，我们调查的气候变化响应的关键中尺度驱动器东非降雨，如海风和湖风，降雨响应的空间异质性。显式模型显示，在世纪末，平均（类似于40%）和极端（类似于50%）降雨率普遍增加，而降雨频率变化的迹象具有很大的空间异质性（从-50%到超过+90%）。相比之下，一个等效的参数化模拟有更大的水分收敛和总降雨量的增加在东部刚果和非洲东部少。参数化模型也没有捕捉到：1）降雨频率变化的巨大异质性; 2）极端降雨量的广泛和大幅增加，这是由于每一个湿度变化都会增加降雨量; 3）降雨对海风变化的响应，尽管海风变化被捕捉到了。因此，以前的降雨预测可能不足以为许多气候敏感的决策提供信息，例如，沿海城市的基础设施。我们认为这里揭示的物理学及其影响与许多其他脆弱的热带地区，特别是那些沿海对流有关。
Eastern Africa's fast-growing population is vulnerable to changing rainfall and extremes. Using the first pan-African climate change simulations that explicitly model the rainfall-generating convection, we investigate both the climate change response of key mesoscale drivers of eastern African rainfall, such as sea and lake breezes, and the spatial heterogeneity of rainfall responses. The explicit model shows widespread increases at the end of the century in mean (similar to 40%) and extreme (similar to 50%) rain rates, whereas the sign of changes in rainfall frequency has large spatial heterogeneity (from -50% to over +90%). In comparison, an equivalent parameterized simulation has greater moisture convergence and total rainfall increase over the eastern Congo and less over eastern Africa. The parameterized model also does not capture 1) the large heterogeneity of changes in rain frequency; 2) the widespread and large increases in extreme rainfall, which result from increased rainfall per humidity change; and 3) the response of rainfall to the changing sea breeze, even though the sea-breeze change is captured. Consequently, previous rainfall projections are likely inadequate for informing many climate-sensitive decisions-for example, for infrastructure in coastal cities. We consider the physics revealed here and its implications to be relevant for many other vulnerable tropical regions, especially those with coastal convection.