A Computational Methodology for the Calibration of Tephra Transport Nowcasting at Sakurajima Volcano, Japan

Alexandros P Poulidis,Atsushi Shimizu,Haruhisa Nakamichi,Masato Iguchi

doi:10.3390/atmos12010104

Alexandros P Poulidis, Atsushi Shimizu + Show 2 more

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https://doi.org/10.3390/atmos12010104

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Abstract

Ground-based remote sensing equipment have the potential to be used for the nowcasting of the tephra hazard from volcanic eruptions. To do so raw data from the equipment first need to be accurately transformed to tephra-related physical quantities. In order to establish these relations for Sakurajima volcano, Japan, we propose a methodology based on high-resolution simulations. An eruption that occurred at Sakurajima on 16 July 2018 is used as the basis of a pilot study. The westwards dispersal of the tephra cloud was ideal for the observation network that has been installed near the volcano. In total, the plume and subsequent tephra cloud were recorded by 2 XMP radars, 1 lidar and 3 optical disdrometers, providing insight on all phases of the eruption, from plume generation to tephra transport away from the volcano. The Weather Research and Forecasting (WRF) and FALL3D models were used to reconstruct the transport and deposition patterns. Simulated airborne tephra concentration and accumulated load were linked, respectively, to lidar backscatter intensity and radar reflectivity. Overall, results highlight the possibility of using such a high-resolution modelling-based methodology as a reliable complementary strategy to common approaches for retrieving tephra-related quantities from remote sensing data.

Highlights

Tephra released after volcanic eruptions constitutes a persistent hazard for communities around them [1,2,3,4]
Lidars can be used to monitor the presence of fine particles [17,18,19], but the sampled area is limited to a line
The top of the plume was advected away from the volcano by 1623 JST (Figure 6d), while part of the tephra cloud lingered over the leeside of the volcano until the end of the simulation due to low wind values (Figure 6f)

Summary

Introduction

Tephra released after volcanic eruptions constitutes a persistent hazard for communities around them [1,2,3,4] This has been the case for Sakurajima volcano in Japan [5]. XMP radars provide a way of monitoring the transport of tephra over large areas, with the drawback of neglecting fine particles due to the wavelengths employed [10,11,12,13,14,15,16]. Disdrometers have been shown to be valuable in the monitoring of tephra sedimentation [20,21], but carry similar limitations to the radars, that is, the wavelength employed limits observations of particles with diameters below ∼0.2 mm [21,22,23]. Despite the limitations of individual equipment, this observational network, coupled with numerical modelling of

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