Fildier Benjamin, Collins William D, Muller Caroline
Laboratoire de Météorologie Dynamique/IPSL, ENS, PSL Université, École Polytechnique, Institut Polytechnique de Paris, Sorbonne Université, CNRS Paris France.
University of California Berkeley CA USA.
J Adv Model Earth Syst. 2021 Feb;13(2):e2020MS002256. doi: 10.1029/2020MS002256. Epub 2021 Feb 23.
We investigate how mesoscale circulations associated with convective aggregation can modulate the sensitivity of the hydrologic cycle to warming. We quantify changes in the full distribution of rain across radiative-convective equilibrium states in a cloud-resolving model. For a given Sea Surface Temperature (SST), the shift in mean rainfall between disorganized and organized states is associated with a shift in atmospheric radiative cooling, and is roughly analogous to the effect of a 4K SST increase. With rising temperatures, the increase in mean rain rate is insensitive to the presence of organization, while extremes can intensify faster in the aggregated state, leading to a faster amplification in the sporadic nature of rain. When convection aggregates, heavy rain is enhanced by 20%-30% and nonlinear behaviors are observed as a function of SST and strength of aggregation feedbacks. First, radiative- and surface-flux aggregation feedbacks have multiplicative effects on extremes, illustrating a non-trivial sensitivity to the degree of organization. Second, alternating Clausius-Clapeyron and super-Clausius-Clapeyron regimes in extreme rainfall are found as a function of SST, corresponding to varying thermodynamic and dynamic contributions, and a large sensitivity to precipitation efficiency variations in some SST ranges. The potential for mesoscale circulations in amplifying the hydrologic cycle is established. However, these nonlinear distortions question the quantitative relevance of idealized self-aggregation. This calls for a deeper investigation of relationships which capture the coupling between global energetics, aggregation feedbacks and local convection, and for systematic tests of their sensitivity to domain configurations, surface boundary conditions, microphysics, and turbulence schemes.
我们研究了与对流聚合相关的中尺度环流如何调节水文循环对变暖的敏感性。我们在一个云分辨模型中量化了辐射对流平衡状态下整个降雨分布的变化。对于给定的海表面温度（SST），无序状态和有序状态之间平均降雨量的变化与大气辐射冷却的变化相关，大致类似于海表面温度升高4K的影响。随着温度升高，平均降雨率的增加对对流组织的存在不敏感，而极端降雨在聚合状态下可能加剧得更快，导致降雨的间歇性更快增强。当对流聚合时，暴雨增强20%-30%，并且观察到作为海表面温度和聚合反馈强度函数的非线性行为。首先，辐射和表面通量聚合反馈对极端降雨有倍增效应，说明了对组织程度的非平凡敏感性。其次，发现极端降雨中交替出现克劳修斯-克拉珀龙和超克劳修斯-克拉珀龙状态，这是海表面温度的函数，对应于不同的热力学和动力学贡献，并且在某些海表面温度范围内对降水效率变化有很大敏感性。确定了中尺度环流在放大水文循环方面的潜力。然而，这些非线性扭曲质疑了理想化自聚合的定量相关性。这需要更深入地研究捕捉全球能量学、聚合反馈和局部对流之间耦合的关系，并对它们对区域配置、表面边界条件、微物理学和湍流方案的敏感性进行系统测试。
