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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Self-aggregation of clouds in conditionally unstable moist convection
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Self-aggregation of clouds in conditionally unstable moist convection

机译：有条件的不稳定对流中云团的自聚集

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摘要

The behavior of moist Rayleigh-Benard convection is investigated using a Boussinesq model with a simplified thermodynamics for phase transitions. This idealized configuration makes the problem accessible to high-resolution three-dimensional direct numerical simulations without small-scale parameterizations of the turbulence for extended layers with aspect ratios up to 64. Our study is focused on the frequently observed conditionally unstable environment that is stably stratified for unsaturated air, but is unstable for cloudy air. We find that no sharp threshold for the transition to convective turbulence exists, a situation similar to wall-bounded shear flows. Rather, the transition depends on the amplitude of the initial perturbation of the quiescent equilibrium and on the aspect ratio of the convective domain. In contrast to the classical dry Rayleigh-Benard case, convection is highly asymmetric with respect to the vertical direction. Moist upwelling air inside turbulent cloud aggregates is surrounded by ambient regions of slowly descending unsaturated air. It is also found that conditionally unstable moist convection is inefficient at transporting energy. Our study suggests that there is an upper bound on the Nusselt number in moist convection that is lower than that of the classical dry case.
机译：使用具有简化的热力学进行相变的Boussinesq模型研究了潮湿的瑞利-贝纳德对流行为。这种理想的配置使得该问题可用于高分辨率的三维直接数值模拟，而无需对宽高比高达64的扩展层进行小规模的湍流参数化。我们的研究集中在稳定地分层的经常观察到的条件不稳定环境上对于不饱和空气，但对于多云空气则不稳定。我们发现，不存在向对流湍流过渡的尖锐阈值，这种情况类似于边界有限的剪切流。而是，过渡取决于静态平衡的初始扰动的幅度以及对流域的纵横比。与经典的干瑞利-贝纳德案例相反，对流相对于垂直方向高度不对称。湍流云团内部的上升气流被周围缓慢下降的不饱和空气包围。还发现，条件不稳定的湿对流在传输能量方面效率低下。我们的研究表明，湿对流中Nusselt数的上限比经典干燥情况下的上限低。

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    Olivier Pauluis; Joerg Schumacher;

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    Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10012-1185;

    Institute of Thermodynamics and Fluid Mechanics, Technische Universitat llmenau, P.O. Box 100565, D-98684 llmenau, Germany;

  • 收录信息 美国《科学引文索引》(SCI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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