Density-driven transport in the umbrella region of volcanic clouds: Implications for tephra dispersion models
Density-driven transport in the umbrella region of volcanic clouds: Implications for tephra dispersion models
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DOI：
10.1002/grl.50942
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发表时间：
2013-09-28
影响因子：
5.2
通讯作者：
Macedonio, Giovanni
中科院分区：
文献类型：
--
作者：
Costa, Antonio;Folch, Arnau;Macedonio, Giovanni
大规模的火山爆发会产生火山灰云，这些火山灰云会在中性浮力水平（NBL）附近的大气中扩散。这些火山灰云以惯性侵入的方式扩散，并被大气风平流。对于低质量流率，火山灰的运输主要是由风平流，因为灰云扩散由于重力流的影响是可以忽略不计的（被动运输）。对于大的质量流率，重力驱动的运输在NBL可以是主要的运输机制。被动输运假设有效的条件尚未得到严格的研究。我们分析的条件时，重力驱动的运输是占主导地位的云理查森数。此外，我们耦合的分析模型，描述云的传播作为一个重力流与对流扩散模型。这个耦合模式是用来模拟1991年皮纳图博火山喷发的气候阶段的火山云的演变。
Large explosive volcanic eruptions can generate ash clouds from rising plumes that spread in the atmosphere around a Neutral Buoyancy Level (NBL). These ash clouds spread as inertial intrusions and are advected by atmospheric winds. For low mass flow rates, tephra transport is mainly dictated by wind advection, because ash cloud spreading due to gravity current effects is negligible (passive transport). For large mass flow rates, gravity-driven transport at the NBL can be the dominant transport mechanism. Conditions under which the passive transport assumption is valid have not yet been critically studied. We analyze the conditions when gravity-driven transport is dominant in terms of the cloud Richardson number. Moreover, we couple an analytical model that describes cloud spreading as a gravity current with an advection-diffusion model. This coupled model is used to simulate the evolution of the volcanic cloud during the climatic phase of the 1991 Pinatubo eruption.