Time-dependent freezing rate parcel model
Time-dependent freezing rate parcel model
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DOI：
10.5194/acp-15-2071-2015
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发表时间：
2014-11
影响因子：
6.3
通讯作者：
G. Vali;J. Snider
中科院分区：
文献类型：
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作者：
G. Vali;J. Snider
抽象的。本文所描述的随时间变化的冻结速率（TDFR）模型代表了在一个空气包中通过浸没冻结形成的冰粒。空气包裹轨迹遵循绝热上升，并且包括包裹在其上升的顶部保持静止的时间段。空气中的冰成核粒子（INPs）的描述取自云和降水样品的实验室实验，并被假定为代表在包裹中的云滴的INP含量。时间依赖性包括考虑上升气流速度的变化和在等温条件下继续形成冰粒。这些因素的大小是在实验室测量的基础上评估的。结果表明，这两个因素引起的三倍的变化，冰浓度为一个现实的输入参数范围。需要对指定时间依赖性和INP浓度的参数进行细化，以使结果更具体地反映不同的大气气溶胶类型。本文描述的简单模型框架可以适用于更复杂的云模型。这里提出的结果可以帮助指导决定是否包括一个时间依赖的冰成核计划或一个简单的奇异描述模型。
Abstract. The time-dependent freezing rate (TDFR) model here described represents the formation of ice particles by immersion freezing within an air parcel. The air parcel trajectory follows an adiabatic ascent and includes a period in time when the parcel remains stationary at the top of its ascent. The description of the ice nucleating particles (INPs) in the air parcel is taken from laboratory experiments with cloud and precipitation samples and is assumed to represent the INP content of the cloud droplets in the parcel. Time dependence is included to account for variations in updraft velocity and for the continued formation of ice particles under isothermal conditions. The magnitudes of these factors are assessed on the basis of laboratory measurements. Results show that both factors give rise to three-fold variations in ice concentration for a realistic range of the input parameters. Refinements of the parameters specifying time dependence and INP concentrations are needed to make the results more specific to different atmospheric aerosol types. The simple model framework described in this paper can be adapted to more elaborate cloud models. The results here presented can help guide decisions on whether to include a time-dependent ice nucleation scheme or a simpler singular description in models.