Sensitivity of liquid clouds to homogenous freezing parameterizations.
Sensitivity of liquid clouds to homogenous freezing parameterizations.
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DOI：
10.1002/2014gl062729
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发表时间：
2015-03-16
影响因子：
5.2
通讯作者：
Koop, Thomas
中科院分区：
文献类型：
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作者：
Herbert, Ross J.;Murray, Benjamin J.;Dobbie, Steven J.;Koop, Thomas
关键词：
一些云中的水滴可以过冷到均匀冰成核成为主要冻结机制的温度。在许多云解析模式和中尺度模式中，都假设水滴中的均匀冰核只会在低于某些阈值温度（通常设定为−40°C）的情况下发生。然而，实验室测量表明，在较温暖的温度下，有一个有限的成核率。在这项研究中，我们使用了一个具有详细微物理学的包裹模型，以表明云的特性可以对温度高达-30 °C的均匀冰成核敏感。因此，均匀冰核可能比通常假设的云发展，降水率和关键云辐射参数更重要。此外，我们表明，云的发展是特别敏感的成核率的温度依赖性。为了更好地约束均匀冰核的参数化，需要在高温（>−35°C）和低温（<−38°C）下进行实验室测量。均匀冻结可能在-30 °C的温度下是显著的均匀冻结不应该由阈值近似表示需要改进均匀冰成核的参数化
Water droplets in some clouds can supercool to temperatures where homogeneous ice nucleation becomes the dominant freezing mechanism. In many cloud resolving and mesoscale models, it is assumed that homogeneous ice nucleation in water droplets only occurs below some threshold temperature typically set at −40°C. However, laboratory measurements show that there is a finite rate of nucleation at warmer temperatures. In this study we use a parcel model with detailed microphysics to show that cloud properties can be sensitive to homogeneous ice nucleation as warm as −30°C. Thus, homogeneous ice nucleation may be more important for cloud development, precipitation rates, and key cloud radiative parameters than is often assumed. Furthermore, we show that cloud development is particularly sensitive to the temperature dependence of the nucleation rate. In order to better constrain the parameterization of homogeneous ice nucleation laboratory measurements are needed at both high (>−35°C) and low (<−38°C) temperatures. Homogeneous freezing may be significant as warm as −30°C Homogeneous freezing should not be represented by a threshold approximation There is a need for an improved parameterization of homogeneous ice nucleation