Precipitation efficiency constraint on climate change
Precipitation efficiency constraint on climate change
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DOI：
10.1038/s41558-022-01400-x
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发表时间：
2022-07-01
影响因子：
30.7
通讯作者：
Storelvmo, Trude
中科院分区：
文献类型：
--
作者：
Li, Ryan L.;Studholme, Joshua H. P.;Storelvmo, Trude
降水效率(PE)将云凝结与降水联系起来，本质上将大气环流与水循环联系在一起。由于PE固有的微物理依赖性，其定义和估计差别很大。因此，人们对PE对温室气体变暖的敏感性以及对气候变化的影响知之甚少。在这里，我们通过定义一个简单的指数epsilon来量化PE在气候变化中的作用，即地表降水与凝结水路径的比率。这一宏观度量与微观物理PE度量是一致的，较高的epsilon与较强的平均Walker环流相关。我们进一步发现，最先进的气候模型在未来埃西隆变化的标志和幅度上存在分歧。这一迹象的不一致源于模式的对流参数化。最重要的是，在温室气体变暖下，与云分辨模拟相一致的模式显示，大尺度的Hadley环流和Walker环流的减慢程度更大，极端降雨量的增加是下降模式的两倍。雨滴下落在全球气候变化中起着重要但尚未量化的作用。在这里，作者使用降水效率的概念来确定雨滴在未来热带大气环流和极端降水的预测中起着关键作用。
Precipitation efficiency (PE) relates cloud condensation to precipitation and intrinsically binds atmospheric circulation to the hydrological cycle. Due to PE's inherent microphysical dependencies, definitions and estimates vary immensely. Consequently, PE's sensitivity to greenhouse warming and implications for climate change are poorly understood. Here, we quantify PE's role in climate change by defining a simple index epsilon as the ratio of surface precipitation to condensed water path. This macroscopic metric is reconcilable with microphysical PE measures and higher epsilon is associated with stronger mean Walker circulation. We further find that state-of-the-art climate models disagree on the sign and magnitude of future epsilon changes. This sign disagreement originates from models' convective parameterizations. Critically, models with increasing epsilon under greenhouse warming, in line with cloud-resolving simulations, show greater slowdown of the large-scale Hadley and Walker circulations and a two-fold greater increase in extreme rainfall than models with decreasing epsilon.Falling raindrops play an essential but as-yet unquantified role in planetary climate change. Here the authors use the concept of precipitation efficiency to establish that raindrops play a critical role in predicting future tropical atmospheric circulation and extreme precipitation.