New Empirical Formulation for the Sublimational Breakup of Graupel and Dendritic Snow
New Empirical Formulation for the Sublimational Breakup of Graupel and Dendritic Snow
复制标题
霰和树枝状雪升华破碎的新经验公式
DOI：
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发表时间：
2021
影响因子：
3.1
通讯作者：
Deepak Waman
中科院分区：
文献类型：
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作者：
Akash Deshmukh;V. Phillips;A. Bansemer;S. Patade;Deepak Waman
冰碎片是由冰粒在天然云中的亚饱和条件下升华而产生的。可以想象，这种升华分裂将导致自然云中的冰增殖。任何碎片的生存将成长为冰降水，可能升华和fractional.As对评估这一被忽视的过程的第一步，提出了一个公式的冰碎片的数量从升华的冰粒的大气模式。这是通过合并以前发表的研究的实验室观察结果来完成的。分裂的“升华质量活度谱”的概念应用于数据集。冰碎片的数量取决于冰上的相对湿度和母体冰粒的初始大小。新的公式仅适用于树枝状晶体和重镶边粒子。最后，对理想化的云内下降的欠饱和情况进行了思想实验。尺度分析产生的冰增强比约5（50）内的弱深对流下沉气流约2米s-1，为3 L-1和2 mm的树枝状雪（）颗粒的初始单分散人口的估计。在下降过程中，在碎片的持续发射和它们因升华而耗尽之间存在动态平衡。一个简化的箱微观物理包裹模型表现出这种动态准平衡，与思想实验一致。碎片的平均寿命分别为90秒和240秒左右的树突和霰。据预测，升华破裂会导致大量的二次冰产生。
Ice fragments are generated by sublimation of ice particles in subsaturated conditions in natural clouds. Conceivably, such sublimational breakup would be expected to cause ice multiplication in natural clouds. Any fragment that survives will grow to become ice precipitation that may sublimate and fragment further.As a first step towards assessing this overlooked process, a formulation is proposed for the number of ice fragments from sublimation of ice particles for an atmospheric model. This is done by amalgamating laboratory observations from previously published studies. The concept of a ‘sublimated mass activity spectrum’ for the breakup is applied to the dataset. The number of ice fragments is determined by the relative humidity over ice and the initial size of the parent ice particles. The new formulation applies to dendritic crystals and heavily rimed particles only.Finally, a thought experiment is performed for an idealized scenario of subsaturation with in-cloud descent. Scaling analysis yields an estimate of an ice enhancement ratio of about 5 (50) within a weak deep convective downdraft of about 2 m s-1, for an initial monodisperse population of dendritic snow (graupel) particles of 3 L-1 and 2 mm . During descent, there is a dynamic equilibrium between continual emission of fragments and their depletion by sublimation. A simplified bin microphysics parcel model exhibits this dynamical quasi-equilibrium, consistent with the thought experiment. The fragments have average lifetimes of around 90 and 240 seconds for dendrites and graupel respectively. Sublimational breakup is predicted to cause significant secondary ice production.