标题： 耦合火灾-云模拟揭示了火积云的机制 显示英文标题

标题： Coupled Fire-Cloud Simulations Reveal Mechanisms of Pyrocumulonimbus Clouds

摘要： 对流积云（pyroCb）火灾发生在野火的上升气流形成降水云时。这些云产生不可预测的风，对生命和财产构成威胁。控制pyroCb行为的耦合火灾-大气相互作用尚未完全理解，之前的模拟要么将火灾视为静态，要么使用半经验的蔓延速率模型。燃料湿度是否作为pyroCb事件的能量源或汇存在争议。我们使用一个精细尺度的云模型，结合具有燃烧物理的火灾模型，来模拟和分析pyroCb及其相关火灾的共同演化。在这里，我们展示了燃料湿度作为能量汇，减弱火灾强度并抑制pyroCb的发展，并且我们识别并量化了一个正反馈环路，即自增强火灾诱导再循环（SAFIR）机制，其中降水引起的下沉气流增强母火。我们的结果表明，燃料湿度对于pyroCb来说是一个不重要的水分来源，与之前的预报指导相矛盾。我们对SAFIR机制的分析显示，弱的高层风有利于靠近母火的pyroCb下沉气流，创造了快速增强的条件。这些发现提供了一个新的机制框架来理解pyroCb行为，为改进这些极端事件的预测提供了见解。 显示英文摘要

摘要： Pyrocumulonimbus (pyroCb) firestorms occur when the updraft from a wildfire forms a precipitating cloud. These clouds create unpredictable winds, posing threats to life and property. The coupled fire-atmosphere interactions that govern the behavior of pyroCb are incompletely understood, with previous simulations either treating the fire as static or using semi-empirical rate of spread models. It is disputed whether fuel moisture serves as an energy source or sink for pyroCB events. We use a fine-scale cloud model coupled with a fire model with combustion physics to simulate and analyze the co-evolution of pyroCb and its associated fire. Here we show fuel moisture acts as an energy sink attenuating fire intensity and suppressing pyroCb development, and we also identify and quantify a positive feedback loop, the self-amplifying fire-induced recirculation (SAFIR) mechanism, where precipitation-induced downdrafts intensify the parent fire. Our results demonstrate fuel moisture is an insignificant source of moisture for the pyroCb, contradicting previous forecasting guidance. Our analysis of the SAFIR mechanism shows weak upper-level winds favor a pyroCb downdraft close to the parent fire, creating conditions for rapid intensification. These findings provide a new mechanistic framework for understanding pyroCb behavior, offering insight towards improved prediction of these extreme events.