Interpretation of umbrella cloud growth and morphology: implications for flow regimes of short-lived and long-lived eruptions
Interpretation of umbrella cloud growth and morphology: implications for flow regimes of short-lived and long-lived eruptions
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DOI：
10.1007/s00445-015-0993-0
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发表时间：
2015
影响因子：
3.5
通讯作者：
S. Pouget;M. Bursik;Christopher G. Johnson-Christopher G.-Johnson-2249719709;Christopher G. Johnson-Christopher G.-Johnson-2249719709;A. Hogg;J. Phillips;R. Sparks
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文献类型：
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作者：
S. Pouget;M. Bursik;Christopher G. Johnson-Christopher G.-Johnson-2249719709;Christopher G. Johnson-Christopher G.-Johnson-2249719709;A. Hogg;J. Phillips;R. Sparks
新的数值和分析模型表明，火山伞云的生长（表示为半径随时间的增加）会通过不同的力平衡主导的状态进行。确定了四种制度：状态Ia是浮力-惯性状态下连续供应侵入体的长期行为;状态IIa是连续供应的湍流阻力主导侵入体的长期行为;状态Ib是恒定体积的浮力-惯性侵入体的长期行为;状态IIb是恒定体积的湍流阻力主导侵入体的长期行为。在每种状态下，扩展时间的幂律指数为3/4（Ia）、5/9（IIa）、1/3（Ib）和2/9（IIb）。数值模拟和观测都表明，制度之间的过渡期可以是持久的，在这些过渡期间，扩展率不遵循简单的幂律。新模型的预测与七次火山爆发的卫星数据一致，再加上对伞云结构和形态演变的观测，支持存在多种扩散机制。
New numerical and analytical modeling shows that the growth of a volcanic umbrella cloud, expressed as the increase of radius with time, proceeds through regimes, dominated by different force balances. Four regimes are identified: Regime Ia is the long-time behavior of continuously-supplied intrusions in the buoyancy-inertial regime; regime IIa is the long-time behavior of continuously-supplied, turbulent drag-dominated intrusions; regime Ib is the long-time behavior of buoyancy-inertial intrusions of constant volume; and regime IIb that of turbulent drag-dominated intrusions of constant volume. Power-law exponents for spreading time in each regime are 3/4 (Ia), 5/9 (IIa), 1/3 (Ib), and 2/9 (IIb). Both numerical modeling and observations indicate that transition periods between the regimes can be long-lasting, and during these transitions, the spreading rate does not follow a simple power law. Predictions of the new model are consistent with satellite data from seven eruptions and, together with observations of umbrella cloud structure and morphological evolution, support the existence of multiple spreading regimes.