Sabancaya volcano (Peru), is a stratovolcano in the Central Volcanic Zone of the Andes. Since November 2016, it has been in constant activity, marked by daily multiple Vulcanian explosions. In this contribution, we first characterize the plumes generated by the explosions using visible- and infrared-wavelength imagery, describing plume morphologies and quantifying rise rates. Through an analysis of plume morphology and rise rates, we find that plumes fall on a continuum between two end-member classifications. Class A plumes are characterized by an amorphous head containing multiple vortices which may combine to form a vortex ring. These plumes have higher initial velocities (generally $\gtrsim 10$ m ${\mathrm{s}}^{-1}$ and up to 40 m ${\mathrm{s}}^{-1}$) which monotonically decrease as the plume rises. Conversely, class B plumes have narrow, cylindrical morphologies and lack large vortical structures in the head. They have smaller initial velocities ($\lesssim 12$ m ${\mathrm{s}}^{-1}$) and, after an initial rise, undergo stagnation followed by a short acceleration in rise velocity, before slowing down again. Secondly, we use a numerical model to invert our observations for eruptive source conditions, including the initial temperature, gas mass fraction and bulk density, as well as the air entrainment coefficient. From our numerical inversions, we find that these plumes have entrainment coefficients between 0.03 and 0.11. This work provides insight into the dynamics of transient plumes and highlights the need for better models to describe their dynamics.

中文翻译：

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将可见光和红外波长观测与数值建模相结合，描述秘鲁 Sabancaya 的火山喷发羽流


萨班卡亚火山（秘鲁）是安第斯山脉中央火山带的一座成层火山。自 2016 年 11 月以来，它一直处于持续活动状态，每天都有多次 Vulcanian 爆炸。在这篇文章中，我们首先使用可见光和红外波长图像来描述爆炸产生的羽流，描述羽流形态并量化上升速率。通过对羽流形态和上升速率的分析，我们发现羽流落在两个端元分类之间的连续体上。A 类羽流的特征是包含多个漩涡的无定形头部，这些漩涡可以组合形成一个涡环。这些羽流具有较高的初始速度（通常为 $\gtrsim 10$ m ${\mathrm{s}}^{-1}$ 和高达 40 m ${\mathrm{s}}^{-1}$ ），随着羽流的上升而单调降低。相反，B 类羽流具有狭窄的圆柱形形态，头部没有大的涡状结构。它们具有较小的初始速度 （ $\lesssim 12$ m ${\mathrm{s}}^{-1}$ ），并且在初始上升后，会停滞，然后上升速度会短暂加速，然后再次减速。其次，我们使用数值模型来反转我们对喷发源条件的观测，包括初始温度、气体质量分数和体积密度，以及空气夹带系数。从我们的数值反演中，我们发现这些羽流的夹带系数在 0.03 到 0.11 之间。这项工作提供了对瞬态羽流动力学的见解，并强调了需要更好的模型来描述它们的动力学。