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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Laboratory simulations show diabatic heating drives cumulus-cloud evolution and entrainment
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Laboratory simulations show diabatic heating drives cumulus-cloud evolution and entrainment

机译：实验室模拟显示非绝热加热驱动积云演化和夹带

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摘要

Clouds are the largest source of uncertainty in climate science, and remain a weak link in modeling tropical circulation. A major challenge is to establish connections between participate micro-physics and macroscale turbulent dynamics in cumulus clouds. Here we address the issue from the latter standpoint. First we show how to create bench-scale flows that reproduce a variety of cumulus-cloud forms (including two genera and three species), and track complete cloud life cycles-e.g., from a "cauliflower" con-gestus to a dissipating fractus. The flow model used is a transient plume with volumetric diabatic heating scaled dynamically to simulate latent-heat release from phase changes in clouds. Laser-based diagnostics of steady plumes reveal Riehl-Malkus type protected cores. They also show that, unlike the constancy implied by early self-similar plume models, the diabatic heating raises the Taylor entrainment coefficient just above cloud base, depressing it at higher levels. This behavior is consistent with cloud-dilution rates found in recent numerical simulations of steady deep convection, and with aircraft-based observations of homogeneous mixing in clouds. In-cloud diabatic heating thus emerges as the key driver in cloud development, and could well provide a major link between microphysics and cloud-scale dynamics.
机译：在气候科学中，云是最大的不确定性来源，并且仍然是模拟热带环流的薄弱环节。一个主要的挑战是在参与的微物理学和积云中的宏观湍流动力学之间建立联系。在这里，我们从后一种角度解决这个问题。首先，我们展示了如何创建能再现各种积云形式（包括两个属和三个物种）的台规模流，并跟踪完整的云生命周期，例如，从“花椰菜”充血到消散的分形。所用的流动模型是瞬态羽流，具有动态非绝热体积，可动态缩放以模拟云相变释放的潜热。基于激光的稳定羽流诊断显示了Riehl-Malkus类型的保护核。他们还表明，与早期自相似羽状模型所暗示的恒定性不同，绝热加热使泰勒夹带系数略高于云层，从而将其压低到更高的水平。这种现象与最近在稳定的深对流数值模拟中发现的云稀释率以及飞机对云中均匀混合的观测结果一致。因此，云中非绝热加热成为云发展的主要驱动力，并且很可能在微观物理学和云规模动力学之间提供主要联系。

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