Sensitivity Analysis of Volcanic Ash Inherent Optical Properties to the Remote Sensed Radiation

Abstract

: Volcanic ash (VA) can be estimated by remote sensing sensors through their spectral signatures determined by the inherent optical property (IOP) including complex refractive index and the scattering properties. Until now, a very limited range of VA refractive indices has been reported and the VA from each volcanic eruption has a different composition. To improve the robustness of VA remote sensing, there is a need to understanding of VA -radiation interactions. In this study, we calculated extinction coefficient, scattering phase function, asymmetry factor, and single scattering albedo which show different values between andesite and pumice. Then, IOPs were used to analyze the relationship between theoretical remote sensed radiation calculated by radiative transfer model under various aerosol optical thickness (τ) and sun-sensor geometries and characteristics of VA. It was found that the mean rate of change of radiance at top of atmosphere versus τ is six times larger than in radiance values at 0.55 μm. At the surface, positive correlation dominates when τ<1, but negative correlation dominates when τ>1. However, radiance differences between andesite and pumice at 11 μm are very small. These differences between two VA types are expressed as the polynomial regression functions and that increase as VA optical thickness increases. Finally, these results would allow VA to be better characterized by remote sensing sensors.

Numerical Simulation of Volcanic Ash Dispersion and Deposition during 2011 Eruption of Mt. Kirishima

“…따라서 대규모 화산 분화에 의 한 화산재 방출은 단기간 내에 급격한 대기질 악화 와 항공교통 마비를 야기시키고 경제적 피해 또한 막대하다 (Millet and Casadevall, 2000;Gasteiger et al, 2011;Sulpizio et al, 2012;Lee et al, 2012;Yu et al, 2013). 또한 대류권 및 성층권내에서 화산재의 이동 및 침적과정을 통하여 복사에너지의 변화를 야 기하고 이러한 복사 수지의 변화는 궁극적으로 지구 규모의 기후 변화에 영향을 준다 (Mishchenko et al, 2007;Lee and Jang, 2014). (Costa et al, 2009;Folch, 2012).…”