Volcanic plume height is a key parameter in retrieving plume ascent and dispersal dynamics, as well as eruption intensity; all of which are crucial for assessing hazards to aircraft operations. One way to retrieve cloud height is the shadow technique. This uses shadows cast on the ground and the sun geometry to calculate cloud height. This technique has, however, not been frequently used, especially not with high-spatial resolution (30 m pixel) satellite data. On 26 October 2013, Mt Etna (Sicily, Italy) produced a lava fountain feeding an ash plume that drifted SW and through the approach routes to Catania international airport. We compared the proximal plume height time-series obtained from fixed monitoring cameras with data retrieved from a Landsat-8 Operational Land Imager image, with results being in good agreement. The application of the shadow technique to a single high-spatial resolution image allowed us to fully document the ascent and dispersion history of the plume–cloud system. We managed to do this over a distance of 60 km and a time period of 50 min, with a precision of a few seconds and vertical error on plume altitude of ±200 m. We converted height with distance to height with time using the plume dispersion velocity, defining a bent-over plume that settled to a neutral buoyancy level with distance. Potentially, the shadow technique defined here allows downwind plume height profiles and mass discharge rate time series to be built over distances of up to 260 km and periods of 24 h, depending on vent location in the image, wind speed, and direction.

中文翻译：

---

在单空间分辨率卫星图像中使用阴影进行羽流高度时间序列的检索

火山羽流高度是检索羽流上升和扩散动态以及喷发强度的关键参数。所有这些对于评估飞机运行的危害至关重要。检索云高的一种方法是阴影技术。这将使用投射在地面上的阴影和太阳几何来计算云的高度。但是，这种技术并未得到广泛使用，尤其是在具有高空间分辨率（30 m像素）的卫星数据中更是如此。2013年10月26日，埃特纳火山（意大利西西里岛）制作了一个熔岩喷泉，向火山灰提供烟灰，该烟灰飘过西南偏南，并通过通往卡塔尼亚国际机场的进场路线。我们比较了从固定监控摄像机获得的近端羽流高度时间序列与从Landsat-8 Operational Land Imager图像检索到的数据，结果吻合良好。将阴影技术应用于单个高空间分辨率的图像使我们能够完整记录羽状云系统的上升和扩散历史。我们设法在60 km的距离和50 min的时间段内执行此操作，精度为几秒钟，垂直羽流高度为±200 m。我们使用羽流分散速度将高度随距离转换为时间随高度的高度，定义了弯曲的羽流，该羽流随着距离稳定到中性浮力水平。根据图像中通风口的位置，风速和方向，此处定义的阴影技术可能会在最大260 km的距离和24 h的时间范围内建立顺风羽流高度轮廓和质量排放速率时间序列。