Characteristics of Particle Size Distributions of Falling Volcanic Ash Measured by Optical Disdrometers at the Sakurajima Volcano, Japan

Atmosphere

Masato Iguchi¹  Ren Takaoka²  Masayuki Maki³ 

[1] Disaster Prevention Research Institute, Kyoto University, Kyoto 611-0011, Japan;Graduate School of Science and Engineering, Kagoshima University, Kagoshima 890-0065, Japan;Research and Education Center for Natural Hazards, Kagoshima University, Kagoshima 890-0065, Japan;

关键词: disdrometer;    eruption cloud;    fall velocity;    gamma function;    particle size distribution;    quantitative ash fall estimation;   

DOI  :  10.3390/atmos12050601

来源: DOAJ

【 摘 要 】

In the present study, we analyzed the particle size distribution (PSD) of falling volcanic ash particles measured using optical disdrometers during six explosive eruptions of the Sakurajima volcano in Kagoshima Prefecture, Japan. Assuming the gamma PSD model, which is commonly used in radar meteorology, we examined the relationships between each of the gamma PSD parameters (the intercept parameter, the slope parameter, and the shape parameter) calculated by the complete moment method. It was shown that there were good correlations between each of the gamma PSD parameters, which might be one of the characteristics of falling volcanic ash particles. We found from the normalized gamma PSD analysis that the normalized intercept parameter and mass-weighted mean diameter are suitable for estimating the ash fall rate. We also derived empirical power law relationships between pairs of integrated PSD parameters: the ash fall rate, the volcanic ash mass concentration, the reflectivity factor, and the total number of ash particles per unit volume. The results of the present study provide essential information for studying microphysical processes in volcanic ash clouds, developing a method for quantitative ash fall estimation using weather radar, and improving ash transport and sedimentation models.

【 授权许可】

Unknown