Ice nucleation in cirrus clouds: A model study of the homogeneous and heterogeneous modes
Ice nucleation in cirrus clouds: A model study of the homogeneous and heterogeneous modes
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卷云中的冰核：同质和异质模式的模型研究
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
S. Benson
中科院分区：
文献类型：
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作者：
K. Sassen;S. Benson
包裹云模式模拟探索了一种统一的方法来描述卷云中均匀和非均匀冰成核机制的可行性。据推测，冰晶生成过程涉及硫酸铵雾颗粒的冻结，在这两种情况下，由与摩尔浓度成比例的有效温度调制。在-36 ° C至-60 °C的模型区域中，上升气流速度和用于近似非均匀冻结的修正弗莱彻方程中的项被视为变量。从均匀的冷冻运行绘制的参数化提供的阈值相对湿度和成核的晶体的数量，作为温度和上升气流速度的函数。我们发现，异质成核可以竞争或占主导地位，在相对较弱的上升气流，但只有异常高的冰核浓度和温度激活条款。
Parcel cloud model simulations have explored the feasibility of a unified approach to describe the homogeneous and heterogeneous ice nucleation mechanisms in cirrus clouds. It was assumed that the ice crystal generation process involved the freezing of ammonium sulfate haze particles, as modulated by an effective temperature proportional to molality in both cases. Treated as variables in the ‐36° to ‐60°C model domain are the updraft velocity, and the terms in a modified Fletcher equation used to approximate heterogeneous freezing. Parameterizations drawn from the homogeneous freezing runs are provided for the threshold relative humidity and number of crystals nucleated, as functions of both temperature and updraft velocity. We find that heterogeneous nucleation can compete or dominate at relatively weak updrafts, but only for unusually high ice nuclei concentration and temperature activation terms.