Preliminary Results of Weather Radar Observations of Sakurajima Volcanic Smoke

Maki, Masayuki; Iguchi, Masato; Maesaka, Takeshi; Miwa, Takahiro; Tanada, Toshikazu; Kozono, Tomofumi; Momotani, Tatsuya; Yamaji, Akihiko; Kakimoto, Ikuya

doi:10.20965/jdr.2016.p0015

Cited by 28 publications

(36 citation statements)

References 15 publications

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“…Ashfall patterns for the different plume heights (H P ) and for both normal and flat simulations exhibit a number of similarities ( Figure 5). All experiments show a NW distribution of ash, which is in agreement with JMA observations as well as radar and satellite data close to the volcano [Shimbori et al, 2013b;Maki et al, 2016]. Deposition occurs along two clearly defined branches in all cases.…”

Section: Ashfallsupporting

confidence: 88%

Orographic effects on the transport and deposition of volcanic ash: A case study of Mount Sakurajima, Japan

et al. 2017

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Volcanic ash is a major atmospheric hazard that has a significant impact on local populations and international aviation. The topography surrounding a volcano affects the transport and deposition of volcanic ash, but these effects have not been studied in depth. Here we investigate orographic impacts on ash transport and deposition in the context of the Sakurajima volcano in Japan, using the chemistry‐resolving version of the Weather Research and Forecasting model. Sakurajima is an ideal location for such a study because of the surrounding mountainous topography, frequent eruptions, and comprehensive observing network. At Sakurajima, numerical experiments reveal that across the 2–8ϕ grain size range, the deposition of “medium‐sized” ash (3–5ϕ) is most readily affected by orographic flows. The direct effects of resolving fine‐scale orographic phenomena are counteracting: mountain‐induced atmospheric gravity waves can keep ash afloat, while enhanced downslope winds in the lee of mountains (up to 50% stronger) can force the ash downward. Gravity waves and downslope winds were seen to have an effect along the dispersal path, in the vicinity of both the volcano and other mountains. Depending on the atmospheric conditions, resolving these orographic effects means that ash can be transported higher than the initial injection height (especially for ash finer than 2ϕ), shortly after the eruption (within 20 min) and close to the vent (within the first 10 km), effectively modifying the input plume height used in an ash dispersal model—an effect that should be taken into account when initializing simulations.

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Section: Ashfallsupporting

confidence: 88%

Orographic effects on the transport and deposition of volcanic ash: A case study of Mount Sakurajima, Japan

et al. 2017

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“…Sakurajima volcano is a complex stratovolcano located on the island of Kyushu in the south of Japan (31.58N, 130.65E, peak height 1117 m; Fig. 1), and is one of Japan's most active and closely monitored volcanoes [14][15][16]. The volcano has a long eruptive history [17], but despite its potential for larger eruptions, since 2008 it has been erupting mainly with ash-rich vulcanian eruptions [18], i.e.…”

Section: Introductionmentioning

confidence: 99%

“…The Sakurajima Volcanological Observatory (SVO), Disaster Prevention Research Institute (DPRI) of Kyoto University operates a Particle-Size-Velocity (parsivel) disdrometer network in order to monitor ashfall over the volcano. Parsivel disdrometers are laser-optical disdrometers used to measure the number, size and fall speed of hydrometeors and ash particles [15,22]. The OTT Parsivel 2 disdormeters used have operating limits of 0.2-25 mm for the particle size and 0.2-20 m s −1 for the velocity.…”

Section: Introductionmentioning

confidence: 99%

Experimental High-Resolution Forecasting of Volcanic Ash Hazard at Sakurajima, Japan

Poulidis¹,

Takemi²,

Iguchi³

2019

J. Disaster Res.

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A high-resolution forecast methodology for the ash hazard at Sakurajima volcano, Japan, is presented. The methodology employs a combined modeling approach and utilizes eruption source parameters estimated by geophysical observations from Sakurajima, allowing for a proactive approach in forecasting. The Weather Research and Forecasting (WRF) model is used to downscale Japan Meteorological Agency (JMA) forecast data over the area of interest. The high-resolution meteorological data are then used in FALL3D model to provide a forecast for the ash dispersal and deposition. The methodology is applied for an eruption that occurred on June 16, 2018. Disdrometer observations of ashfall are used along with ash dispersal modeling to inform the choice of the total grain size distribution (TGSD). A series of pseudo-forecast ash dispersal simulations are then carried out using the proposed methodology and estimated TGSD, initialized with meteorological forecast data released up to ∼13 hours before the eruption, with results showing surprising consistency up to ∼10 hours before the eruption. Using forecast data up to 4 hours before the eruption was seen to constrain observation to model ratios within a factor of 2–4 depending on the timing of simulation and location. A number of key future improvements for the methodology are also highlighted.

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“…Aerodynamic properties are important for safe aviation and for studying the effects of volcanic ash on climate change, since these parameters determine the residence time of ash particles in the atmosphere (e.g., Folch et al, 2009). The V T of particles varies widely due to their irregular shapes and material components (e.g., Wilson, 1972;Harris and Rose, 1983;Bonadonna et al, 2011;Maki et al, 2016). Bonadonna et al (2011) analyzed V T of volcanic ash particles with various particle densities (ρ s ) from 990 to 2738 kg m −3 , and Maki et al (2016) summarized the list of various V T relationships suggested by previous studies.…”

Section: Introductionmentioning

confidence: 99%

Free-fall experiments of volcanic ash particles using a 2-D video disdrometer

Suh

Maki²,

Iguchi

et al. 2019

Atmos. Meas. Tech.

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Abstract. Information of aerodynamic parameters of volcanic ash particles, such as terminal velocity, axis ratio, and canting angle, are necessary for quantitative ash-fall estimations with weather radar. In this study, free-fall experiments of volcanic ash particles were accomplished using a two-dimensional video disdrometer under controlled conditions. Samples containing a rotating symmetric axis were selected and divided into five types according to shape and orientation: oblate spheroid with horizontal rotating axis (OH), oblate spheroid with vertical axis (OV), prolate spheroid with horizontal rotating axis (PH), prolate spheroid with vertical rotating axis (PV), and sphere (Sp). The horizontally (OH and PH) and vertically (OV and PV) oriented particles were present in proportions of 76 % and 22 %, and oblate and prolate spheroids were in proportions of 76 % and 24 %, respectively. The most common shape type was OH (57 %). The terminal velocities of OH, OV, PH, PV, and Sp were obtained analyzing 2-D video disdrometer data. The terminal velocities of PV were highest compared to those of other particle types. The lowest terminal velocities were found in OH particles. It is interesting that the terminal velocities for OH decreased rapidly in the range 0.5<D<1 mm, corresponding to the decrease in axis ratio (i.e., smaller the particle, the flatter the shape). The axis ratios of all particle types except Sp were found to be converged to 0.94 at D>2 mm. The histogram of canting angles followed unimodal and bimodal distributions with respect to horizontally and vertically oriented particles, respectively. The mean values and the standard deviation of entire particle shape types were close to 0 and 10∘, respectively, under calm atmospheric conditions.

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Preliminary Results of Weather Radar Observations of Sakurajima Volcanic Smoke

Cited by 28 publications

References 15 publications

Orographic effects on the transport and deposition of volcanic ash: A case study of Mount Sakurajima, Japan

Orographic effects on the transport and deposition of volcanic ash: A case study of Mount Sakurajima, Japan

Experimental High-Resolution Forecasting of Volcanic Ash Hazard at Sakurajima, Japan

Free-fall experiments of volcanic ash particles using a 2-D video disdrometer

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