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Understanding subtropical anvil cirrus: A coupled modeling study.

机译：了解亚热带铁砧卷云：耦合建模研究。

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摘要

This research investigates the sensitivity of anvil layer cirrus's characteristics to its mesoscale environment. A coupled modeling system composed of a mesoscale model and cloud model is used to represent the evolution of systems with different scales. Lagrangian trajectories in the mesoscale model are used to determine the mesoscale environment of the simulated anvil and calculate the mesoscale forcing. A new sedimentation parameterization for the cloud model is developed to better represent fall speeds for large particles. Convection and the resulting outflow cirrus occurring near Ft. Myers, Florida on July 16, 2002 are used for the case study. The mesoscale model produced convection and an ice cloud similar to what was observed that day. The cloud model was used to determine the set of cloud processes in response to the mesoscale forcing that produced more condensate and prolonged cloud lifetime. These simulations show that differential radiative heating and cooling is the key process. The cooling and moistening in response to the mesoscale forcing produces more ice, enhancing cloud-top radiative cooling and cloud-base infrared warming. This generates more buoyancy, strengthening the cloud's updrafts and producing many small crystals to further enhance the cloud-top cooling, until sedimentation removes enough mass to end the positive feedbacks. The presence and magnitude of the mesoscale forcing alters the amount of condensate formed, altering the cloud-top cooling rate and the cloud's response to the forcing. The anvil cloud simulation was relatively insensitive to the initial condensate once the cloud becomes optically thick enough to be considered a black-body. While longwave cloud-top cooling is necessary for the interactions between mesoscale forcing and cloud dynamics, the most turbulent anvil cirrus layers require shortwave in-cloud warming.;In response to recent measurements of the deposition coefficient, alpha d, I develop a parameterization that represents the effects of kinetically-limited growth in a bulk ice microphysics model. Using this, we explore a range of coefficients to determine how this would would affect our set of cloud processes. Values of alphad near those measurements significantly reduce vapor deposition, elevating supersaturation and the nucleation rates. The elevated nucleation rates sequester more condensate in non-precipitating ice and minimize sedimentation velocities. The large ice water contents so produced keep cloud-top infrared cooling rates high. These two effects directly and indirectly prolongs cloud lifetimes. These results are the first demonstration of the connection between alpha v and simulated cirrus dynamics.
机译：这项研究调查了砧层卷云特征对其中尺度环境的敏感性。由中尺度模型和云模型组成的耦合建模系统用来表示不同尺度系统的演化。中尺度模型中的拉格朗日轨迹用于确定模拟砧座的中尺度环境并计算中尺度强迫。针对云模型开发了一种新的沉降参数化方法，以更好地表示大颗粒的下落速度。对流和由此产生的流出卷云发生在Ft附近。本案例研究使用2002年7月16日在佛罗里达州迈尔斯进行的研究。中尺度模型产生的对流和冰云类似于当天所观察到的。云模型用于确定中尺度强迫响应，从而产生更多的凝结水和延长云寿命，从而确定云过程集。这些模拟表明，差分辐射加热和冷却是关键过程。响应中尺度强迫而进行的冷却和润湿会产生更多的冰，从而增强云顶辐射冷却和云基红外增温。这产生了更多的浮力，增强了云的上升气流，并产生了许多小晶体，从而进一步增强了云顶的冷却，直到沉淀物去除足够的质量以结束正反馈为止。中尺度强迫的存在和大小改变了形成的冷凝物的量，改变了云顶冷却速率和云对强迫的响应。一旦云的光学厚度变得足够厚，可以认为是黑体，那么砧座云模拟对初始冷凝物就相对不敏感。虽然长波云顶冷却对于中尺度强迫和云动力学之间的相互作用是必需的，但最动荡的砧卷云层需要短波云内加热。;为响应最近对沉积系数αd的测量，我开发了一个参数化表示在体冰微观物理学模型中动力学受限的生长的影响。利用这一点，我们探索了一系列系数，以确定这将如何影响我们的云过程集。在这些测量值附近的αd值显着降低了气相沉积，提高了过饱和度和成核速率。较高的成核速率可将更多的凝结物隔离在非沉淀冰中，并使沉降速度最小化。如此产生的大量冰水使云层顶红外冷却速率保持较高。这两种影响直接或间接地延长了云的寿命。这些结果是alpha v与模拟卷云动力学之间联系的首次证明。

著录项

  • 作者

    Carver, Robert Wyatt.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Meteorology.;Atmospheric Sciences.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 248 p.
  • 总页数 248
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

  • 入库时间 2022-08-17 11:38:19

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