Seasonal Variations of Volcanic Ash and Aerosol Emissions around Sakurajima Detected by Two Lidars

Atsushi Shimizu,Haruhisa Nakamichi,Masato Iguchi

doi:10.3390/atmos12030326

Atsushi Shimizu, Haruhisa Nakamichi + Show 1 more

Open Access

https://doi.org/10.3390/atmos12030326

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Abstract

Two polarization-sensitive lidars were operated continuously to monitor the three-dimensional distribution of small volcanic ash particles around Sakurajima volcano, Kagoshima, Japan. Here, we estimated monthly averaged extinction coefficients of particles between the lidar equipment and the vent and compared our results with monthly records of volcanic activity reported by the Japan Meteorological Agency, namely the numbers of eruptions and explosions, the density of ash fall, and the number of days on which ash fall was observed at the Kagoshima observatory. Elevated extinction coefficients were observed when the surface wind direction was toward the lidar. Peaks in extinction coefficient did not always coincide with peaks in ash fall density, and these differences likely indicate differences in particle size.

Highlights

The five indices of volcanic activity at Sakurajima reported by Japan Meteorological Agency (JMA) and Disaster Prevention Research Institute (DPRI) during 2017 are broadly consistent with our lidar results, during the later part of the year, all indices except ash fall days peaked in September
This may indicate that the ash particles transported westward were larger than during other periods: in this case, the density of ash fall at Kagoshima observatory should be large and the extinction coefficient near the lidar should be small because ash volume and surface area are related to the cube and square of particle size, respectively
We analyzed monthly mean extinction coefficient profiles obtained from the SVO and KUR lidars deployed around Sakurajima

Summary

Introduction

Seasonal Variations of Volcanic eruptions are a natural source of atmospheric aerosols [1]. Monitoring equipment around volcanoes target volcanic ash, not sulfate, an indispensable task for mitigating the impacts of eruptions. AOD can be retrieved over broad areas from satellite-borne passive sensors such as the Advance Himawari Imager onboard Himawari-8 [6], optical properties observed by active lidar sensing are more accurate because horizontal variations are non-negligible in individual pixels of satellite data. Lidar is very sensitive to smaller particles such as fine ash because it utilizes visible to infrared light [8,9,10,11]. We describe volcanic ash observations using two lidars near Sakurajima volcano, Japan.

Lidar Observation and Supplemental Information

16 June 2018

Seasonal and Annual Variations of Aerosols Detected by SVO Lidar

Concluding Remarks