期刊名称：Journal of Advances in Modeling Earth Systems
电子版ISSN：1942-2466
出版年度：2021
卷号：13
期号：2
页码：e2020MS002256
DOI：10.1029/2020MS002256
出版社：John Wiley & Sons, Ltd.
摘要：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. Plain Language Abstract Convective aggregation, or organization, is known to affect the spatial distribution of clouds, the wind circulation and the intensity of rain as a result of feedbacks that couple convective processes, radiative transfer in the atmosphere and energy fluxes from the Earth's surface. We investigate how the hydrologic cycle responds to warming in various conditions of forcing and aggregation feedbacks in a hierarchy of idealized simulations, and provide a fine characterization of the statistical distribution of rain in order to connect its modes of change to the physical drivers involved in aggregation. The critical role of precipitation efficiency, namely the fraction of rainwater that reaches the surface, is advanced. The complex behavior of the rain distribution in these simulations feeds a discussion on the use of idealized experiments to investigate convective organization and on their relevance to understand future changes in the hydrologic cycle.
