发表机构
Yale University; Pohang University of Science and Technology; Sorbonne Université -CNRS-IRD-MNHN（耶鲁大学; 浦项科技大学; 索邦大学-CNRS-IRD-MNHN）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出一个降阶耦合振子模型，用柱积分湿度和热力层结表示热带对流，再现准稳态与阵发性两种降水状态，揭示湿度阈值与对流持续性驱动的转变机制。
AI 中文摘要
极端降水是社会关注的问题，而在气候变暖背景下，理解热带湿对流日益重要。气候模拟表明，在“温室地球”情景下，对流可以从准稳态降水转变为阵发性状态，其特征是强降雨爆发与干燥间隔交替出现，尽管控制这一转变的机制仍存在争议。在此，我们开发了一个降阶框架，通过柱积分湿度（q）和热力层结（Delta）来表示热带对流，而非使用对流不稳定的整体度量。对云解析模型（CRM）模拟的分析表明，这些变量共同演化：在干燥期，地表通量补充湿度，而辐射和动力过程侵蚀先前对流产生的层结。我们将这一演化与热带降水（P）的非线性湿度依赖性耦合，即降水在临界湿度阈值以上急剧增加。第三个预报变量C代表对流持续性，允许对流在其起始阈值以下继续，从而产生滞后现象。通过CRM输出约束参数，该模型再现了两种状态下q、Delta和P的演化，将准稳态对流表示为稳定的、噪声驱动的振荡，而将阵发性对流表示为不稳定的、自持的极限环。线性稳定性分析表明，转变取决于湿度补充和层结调整时间尺度、热-湿敏感性和对流持续性。由于辐射和动力过程通过其对热力层结的影响而进入，该框架不依赖于特定机制，为湿度阈值降水行为与变暖下阵发性对流涌现之间提供了统一的动力学联系。
英文摘要
Extreme precipitation is a societal concern, and understanding tropical moist convection is increasingly important in a warming climate. Climate simulations show that, under hothouse Earth, convection can transition from quasi-steady precipitation to an episodic regime characterized by intense rainfall bursts separated by dry intervals, although the mechanisms governing this transition remain debated. Here we develop a reduced-order framework that represents tropical convection through column-integrated moisture (q) and thermal stratification (Delta), rather than bulk measures of convective instability. Analysis of cloud-resolving model (CRM) simulations shows that these variables evolve together: during dry periods, surface fluxes recharge moisture, while radiative and dynamical processes erode stratification generated by previous convection. We couple this evolution to the nonlinear moisture dependence of tropical precipitation (P), whereby rainfall increases sharply above a critical moisture threshold. A third prognostic variable, C, represents convective persistence, allowing convection to continue below its onset threshold and thereby producing hysteresis. With parameters constrained by CRM output, the model reproduces the evolution of q, Delta, and P in both regimes, representing quasi-steady convection as stable, noise-driven oscillations and episodic convection as an unstable, self-sustained limit cycle. Linear stability analysis shows that the transition depends on moisture-recharge and stratification-adjustment timescales, thermal-moisture sensitivity, and convective persistence. Because radiative and dynamical processes enter through their effects on thermal stratification, the framework is not tied to a specific mechanism, providing a unified dynamical link between moisture-threshold precipitation behavior and the emergence of episodic convection under warming.
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