Abstract Real-time monitoring of volcanic tephra fallout rate is an important factor to predict ash plume dispersion and to mitigate risk to air traffic. Ground-based weather radar has been one of the fundamental instruments to detect the plume and derive eruptive source parameters, such as the tephra fallout rate. The current work presents the use of two small and compact X-band Multi-Parameter (X-MP) radars for a new tephra fallout rate model development and the technical aspects of the system in Sinabung and Merapi Volcanoes. The new model estimates the tephra fallout rate using two radar parameters: the specific differential phase shift parameter and the reflectivity intensity factor. Total cumulated mass estimated from the radar-based tephra fallout rate model from the radar is compared with the plume height model and an empirical radar-based model. A volcanic eruptive index (VEI)-2 of Sinabung generated a plume exceeding 15 km, resulting in a maximum tephra fallout rate of 0.58 kg m−2 h−1 and a total tephra mass of 51 × 106 kg. The VEI 1 of Sinabung caused a plume height of 2.5 km, resulting in a maximum tephra fallout rate of 0.3 kg m−2 h−1 and a total cumulated tephra of 9 × 106 kg. In the last case, a VEI 1 eruption of Mt. Merapi produces a 6 km plume, resulting in a maximum tephra fallout rate of 0.28 kg m−2 h−1 and a total cumulated tephra of 35 × 106 kg. The sector range height indicator scan-mode strategy in the VEI 2 eruption of Mt. Sinabung ran at six degrees azimuth angles capturing only a partial volume of the plume. Thus, the total mass was only 22% of the result from the empirical plume height model, even though the plume height was assumed to be equally the same with the maximum height scanned of radar at 7 km. In contrast, the volumetric scan by a plan position indicator strategy gave a total cumulated tephra mass, that matches better to the result of the empirical plume height model at 65–92%. Based on these results and the ability of the X-MP radar to capture the volcanic plume at the same reported onset time, we can confirm the importance of an X-MP radar for real-time tephra fallout monitoring during an eruption.

中文翻译：

---

小型紧凑型X波段多参数雷达的实时火山灰沉降率模型

摘要 实时监测火山灰沉降率是预测灰羽扩散和降低空中交通风险的重要因素。地基天气雷达一直是检测羽流和推导出火山喷发源参数（如火山灰沉降率）的基本工具之一。当前的工作介绍了使用两个小型紧凑型 X 波段多参数 (X-MP) 雷达开发新的火山灰沉降率模型以及该系统在 Sinabung 和 Merapi 火山的技术方面。新模型使用两个雷达参数估计火山灰沉降率：特定微分相移参数和反射强度因子。将根据雷达的基于雷达的火山灰沉降率模型估计的总累积质量与羽流高度模型和基于经验的雷达模型进行比较。Sinabung 的火山爆发指数 (VEI)-2 产生了超过 15 公里的羽流，导致最大的 tephra 沉降率为 0.58 kg m-2 h-1，总 tephra 质量为 51 × 106 kg。Sinabung 的 VEI 1 造成了 2.5 公里的羽状流高度，导致最大的火山灰沉降率为 0.3 kg m-2 h-1，总的累积火山灰为 9 × 106 kg。在最后一种情况下，山的 VEI 1 喷发。Merapi 产生 6 公里的羽流，导致最大的火山灰沉降率为 0.28 kg m-2 h-1，总累积火山灰为 35 × 106 kg。Mt. VEI 2 喷发中的扇区范围高度指示器扫描模式策略。Sinabung 以 6 度方位角运行，仅捕获部分羽流。因此，总质量仅为经验羽流高度模型结果的 22%，即使羽流高度被假定为与雷达在 7 公里处扫描的最大高度相同。相比之下，计划位置指示器策略的体积扫描给出了总累积的火山灰质量，与经验羽流高度模型的结果匹配得更好，为 65-92%。根据这些结果以及 X-MP 雷达在报告的同一时间捕获火山羽流的能力，我们可以确认 X-MP 雷达在喷发期间实时监测火山灰沉降的重要性。即使假设羽流高度与雷达在 7 公里处扫描的最大高度相同。相比之下，计划位置指示器策略的体积扫描给出了总累积的火山灰质量，与经验羽流高度模型的结果匹配得更好，为 65-92%。根据这些结果以及 X-MP 雷达在报告的相同爆发时间捕获火山羽流的能力，我们可以确认 X-MP 雷达对于火山喷发期间实时火山灰沉降监测的重要性。即使假设羽流高度与雷达在 7 公里处扫描的最大高度相同。相比之下，计划位置指示器策略的体积扫描给出了总累积的火山灰质量，与经验羽流高度模型的结果匹配得更好，为 65-92%。根据这些结果以及 X-MP 雷达在报告的相同爆发时间捕获火山羽流的能力，我们可以确认 X-MP 雷达对于火山喷发期间实时火山灰沉降监测的重要性。