The Initial Development of Transient Volcanic Plumes as a Function of Source Conditions
The Initial Development of Transient Volcanic Plumes as a Function of Source Conditions
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作为源条件函数的瞬态火山羽流的初步发展
DOI：
10.1002/2017jb014907
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
A. Yokoo
中科院分区：
文献类型：
--
作者：
Pierre;J. Taddeucci;D. Gaudin;J. J. Peña Fernández;E. del Bello;P. Scarlato;U. Kueppers;J. Sesterhenn;A. Yokoo
短暂的火山羽流，具有相似的喷发持续时间和上升时间尺度，特点是许多不稳定的斯特龙博利火山喷发。尽管更常见，但这种羽流比来自更强爆发的稳定状态对应物研究得更少。在这里，我们使用高速（可见光和热）和高分辨率（可见光）视频从Strombolian到Vulcanian的Stromboli（意大利），Fuego（危地马拉）和Sakurajima（日本）火山爆发调查瞬态火山羽流的初始动力学。通过定义它们的锋面速度、速度场、体积和表观表面温度，对羽流进行了物理参数化。我们还描述了喷口处气体-火山碎屑混合物的喷射特征，包括单个喷射脉冲的数量、位置、持续时间和频率，以及喷射物灰分的时间分辨质量喷发率。前缘速度沿沿着两个不同的趋势发展，这两个趋势与初始气体推力阶段和后来的浮力阶段有关。通过光流分析获得的羽流速度场突出了不同的特征，包括初始射流和不同尺度的环形涡的形成和/或合并。烟羽体积随时间增加，遵循所有火山共有的幂律趋势，并受到喷口排放历史的影响。时间分辨的火山灰喷发速率范围在102到107千克/秒之间，在喷发的第一秒内可能变化高达2个数量级。我们的研究结果有助于详细说明喷口喷射脉冲之间的数量，位置，角度，持续时间，速度和时间间隔如何至关重要地控制初始（前几十秒），并可能在以后，瞬态火山羽流的演变。
Transient volcanic plumes, having similar eruption duration and rise timescales, characterize many unsteady Strombolian to Vulcanian eruptions. Despite being more common, such plumes are less studied than their steady state counterpart from stronger eruptions. Here we investigate the initial dynamics of transient volcanic plumes using high‐speed (visible light and thermal) and high‐resolution (visible light) videos from Strombolian to Vulcanian eruptions of Stromboli (Italy), Fuego (Guatemala), and Sakurajima (Japan) volcanoes. Physical parameterization of the plumes has been performed by defining their front velocity, velocity field, volume, and apparent surface temperature. We also characterized the ejection of the gas‐pyroclast mixture at the vent, in terms of number, location, duration, and frequency of individual ejection pulses and of time‐resolved mass eruption rate of the ejecta's ash fraction. Front velocity evolves along two distinct trends related to the initial gas‐thrust phase and later buoyant phase. Plumes' velocity field, obtained via optical flow analysis, highlights different features, including initial jets and the formation and/or merging of ring vortexes at different scales. Plume volume increases over time following a power law trend common to all volcanoes and affected by discharge history at the vent. Time‐resolved ash eruption rates range between 102 and 107 kg/s and may vary up to 2 orders of magnitude within the first seconds of eruption. Our results help detailing how the number, location, angle, duration, velocity, and time interval between ejection pulses at the vents crucially control the initial (first tens of second), and possibly later, evolution of transient volcanic plumes.
影响因子：
5.8
作者：
L. Scharff;M. Hort;N. Varley
通讯作者：
L. Scharff;M. Hort;N. Varley