5:15 PM - 7:15 PM
[MTT38-P06] Lidar remote sensing of small volcanic particles emitted from Sakurajima
Keywords:lidar, extinction coefficient, depolarization ratio
Volcanic ash whose size is smaller than 1 millimeter is not detected effectively by radars due to small reflectivity at the wavelength of radio wave. Lidar (laser radar) is useful to detect such small particles because the scattering by particles of micrometer size is strong at the wavelength of visible or infrared light. Small volcanic ash is transported for long-range, and their density is crucial for aviation, and precise monitoring of such particles by lidars are beneficial to keep the safety of residents and passengers.
Since 2014, two lidars have been operated at two observatories at western and eastern side in Sakurajima to monitor the variations of small particles emitted from Sakurajima vent. Continuous observations of volcanic ash have been conducted by two-wavelength polarization lidars which can distinguish non-spherical mineral particles and secondary generated particles including sulfate. The telescope of the lidar is pointed toward the Minami-dake vent and the range resolution is 6 m with time resolution of 10 seconds. Extinction coefficient of the particles was estimated by Fernald's method and compared with meteorological parameters.
Monthly mean extinction coefficient near the Sakurajima Volcano Observatory of DPRI, Kyoto University exhibited annual variation along with the surface wind direction. During May and September, the extinction coefficient was enhanced and in other seasons the value was low. Daily maximum extinction coefficient was highest at the near vent ranges, namely about 5 km from the lidar equipment. Long-term variation of extinction coefficient is not evident, but the number of highly depolarized airmass and the ash emission from Sakurajima reported by Japan Meteorological Agency (JMA) showed moderate correlation. Especially after 2020 the correlation coefficient was enhanced at a zone near the vent.
Since 2014, two lidars have been operated at two observatories at western and eastern side in Sakurajima to monitor the variations of small particles emitted from Sakurajima vent. Continuous observations of volcanic ash have been conducted by two-wavelength polarization lidars which can distinguish non-spherical mineral particles and secondary generated particles including sulfate. The telescope of the lidar is pointed toward the Minami-dake vent and the range resolution is 6 m with time resolution of 10 seconds. Extinction coefficient of the particles was estimated by Fernald's method and compared with meteorological parameters.
Monthly mean extinction coefficient near the Sakurajima Volcano Observatory of DPRI, Kyoto University exhibited annual variation along with the surface wind direction. During May and September, the extinction coefficient was enhanced and in other seasons the value was low. Daily maximum extinction coefficient was highest at the near vent ranges, namely about 5 km from the lidar equipment. Long-term variation of extinction coefficient is not evident, but the number of highly depolarized airmass and the ash emission from Sakurajima reported by Japan Meteorological Agency (JMA) showed moderate correlation. Especially after 2020 the correlation coefficient was enhanced at a zone near the vent.