Wind conditions for snow cornice formation in a wind tunnel
Wind conditions for snow cornice formation in a wind tunnel
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DOI：
10.5194/tc-17-639-2023
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发表时间：
2023-02
期刊：
影响因子：
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通讯作者：
Hong-xiang Yu;Guang Li;B. Walter;M. Lehning;J. Zhang;N. Huang
中科院分区：
文献类型：
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作者：
Hong-xiang Yu;Guang Li;B. Walter;M. Lehning;J. Zhang;N. Huang
抽象的。在雪季，生长在山脊背风侧的积雪飞檐在高山和极地地区很常见。这些结构可能会破裂和坍塌，导致雪崩危险增加。虽然已经在风洞试验和现场观察到了飞檐的形成，但关于形成机理的认识仍然存在空白。这一点在有利于飞檐形成的风条件下尤其如此。为了确定风的作用是影响檐盖生长的主要因素，我们在寒冷的实验室中进行了不同风条件下的环状风洞试验。定量研究了飞檐在水平方向和垂直方向上的生长速度以及空气中颗粒物的浓度。结果表明，飞檐只出现在中等风速范围内(1-2倍的门槛风速)。飞檐的长度和厚度的增长速度主要是由质量积累和侵蚀的综合作用决定的。飞檐生长的下限风速与积雪输送的门槛风速大致相等。当侵蚀速率大于淤积速率时，风速的上限。当风速高于门槛风速约40%时，飞檐的长度增长率达到最大值。此外，基于质量守恒定律和RWT实验结果，提出了一个解释天檐吸积机理的概念模型。在斯瓦尔巴特群岛Gruvefjellet估计的适宜的风条件下，檐的生长和形成与现场观测很好地一致。基于漂雪的物理基础上，我们的结果提供了对积雪飞檐形成的新见解，并提高了对影响雪崩活动的飞檐过程的理解。实验结果和概念模型可用于未来雪檐下雪崩的模拟和预报工作。
Abstract. Snow cornices growing on the leeward side of mountain ridges are common in alpine and polar regions during snow seasons. These structures may crack and fall, leading to an increase in avalanche danger. Although cornice formation has been observed in wind tunnel tests and the field, knowledge gaps still exist regarding the formation mechanism. This is particularly true with respect to wind conditions which favor cornice formation. To characterize the wind effects as the main factor for cornice growth, we carried out ring wind tunnel (RWT) experiments in a cold laboratory under various wind conditions. We quantitatively investigated the growth rate of the cornice in the horizontal and vertical direction as well as the airborne particle concentration. The results show that cornices only appear under a moderate wind speed range (1–2 times the threshold wind speed). The cornice growth rates in length and thickness are mainly determined by the combined effects of mass accumulation and erosion. The lower-limit wind speed for cornice growth is approximately equal to the threshold wind speed for snow transport. The upper limit of wind speed is when the erosion rate is higher than the deposition rate. The length growth rate of the cornices reaches a maximum for wind speeds approximately 40 % higher than the threshold wind speed. Moreover, a conceptual model for interpreting the cornice accretion mechanism is proposed based on the mass conservation and the results of the RWT experiments. The estimated suitable wind condition for cornice growth and formation are in good agreement with field observations in Gruvefjellet, Svalbard. Based on the physics of drifting snow, our results provide new insights into snow cornice formation and improve understanding of cornice processes that can influence avalanche activity. The experimental results and the conceptual model can be used in future snow cornice simulation and prediction work for cornice-induced avalanches.