Department of Atmospheric and Oceanic Sciences, Peking University, Beijing 100871, China;
Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027.
Proc Natl Acad Sci U S A. 2020 Apr 21;117(16):8757-8763. doi: 10.1073/pnas.1913584117. Epub 2020 Apr 6.
Responses of extreme precipitation to global warming are of great importance to society and ecosystems. Although observations and climate projections indicate a general intensification of extreme precipitation with warming on global scale, there are significant variations on the regional scale, mainly due to changes in the vertical motion associated with extreme precipitation. Here, we apply quasigeostrophic diagnostics on climate-model simulations to understand the changes in vertical motion, quantifying the roles of dry (large-scale adiabatic flow) and moist (small-scale convection) dynamics in shaping the regional patterns of extreme precipitation sensitivity (EPS). The dry component weakens in the subtropics but strengthens in the middle and high latitudes; the moist component accounts for the positive centers of EPS in the low latitudes and also contributes to the negative centers in the subtropics. A theoretical model depicts a nonlinear relationship between the diabatic heating feedback (α) and precipitable water, indicating high sensitivity of α (thus, EPS) over climatological moist regions. The model also captures the change of α due to competing effects of increases in precipitable water and dry static stability under global warming. Thus, the dry/moist decomposition provides a quantitive and intuitive explanation of the main regional features of EPS.
极端降水对全球变暖的响应对社会和生态系统至关重要。尽管观测和气候预测表明，随着全球变暖，极端降水总体上会加剧，但在区域尺度上存在显著的变化，主要是由于与极端降水相关的垂直运动的变化。在这里，我们应用准地转诊断方法对气候模型模拟进行分析，以了解垂直运动的变化，量化干（大尺度绝热流）和湿（小尺度对流）动力在塑造极端降水敏感区（EPS）的区域模式方面的作用。干燥成分在亚热带地区减弱，但在中高纬度地区增强；潮湿成分解释了 EPS 低值中心的正中心，也导致了亚热带的负中心。一个理论模型描述了非绝热加热反馈（α）和可降水量之间的非线性关系，表明在气候潮湿地区，α 的敏感性（因此，EPS）很高。该模型还捕捉到了由于全球变暖下可降水量和干燥静稳度增加的竞争效应，α 发生的变化。因此，干湿分解为 EPS 的主要区域特征提供了一种定量和直观的解释。
