5:15 PM - 6:30 PM
[MIS13-P01] Estimation of ash refractive index and improvement of Himawari-8 volcanic ash algorithm
★Invited Papers
Keywords:volcanic ash clouds , refractive index, Himawari-8
For continuous near-real time monitoring of volcanic ash clouds (VAC) in both day and night, satellite observations by using infrared sensors are particularly useful. Because volcanic silicate has a characteristic absorption band around 10μm wavelength, VAC of fine ash particles can be easily detected and distinguished from water/ice clouds by measurements of brightness temperature difference between two channels in this absorption band. Applying further constraints for microphysical properties of the ash particles, such as particle size distribution, and for atmospheric profile, retrieval of physical properties for VAC (cloud height, particle effective radius, optical depth, and the associated ash mass loading) has been realized by adding the measurements of other infrared channels of high-resolution satellite imagers. These retrieval analyses are based on the results of numerical simulations for the measured infrared brightness temperature by radiative transfer calculations for VAC under the assumption of atmospheric profiles and surface condition, and therefore, optical properties of the ash particles are essential. In particular, the complex refractive index (RI) is one of the important and upstream parameters in estimation of the ash optical properties and their wavelength dependences.
From the data of satellite infrared sounder measurements for VAC and radiative transfer calculations, we estimate optimal refractive index models of the volcanic ash material to simulate the measured brightness temperature spectrum. In addition, we have developed an algorithm of 1DVAR analysis (OVAA) that estimates the physical properties of VAC from the data of multi-wavelength satellite imager such as Himawari-8. By using the optimal RI model estimated by the infrared sounder and using OVAA, high accuracy Himawari-8 analysis for the physical parameters of VAC is expected.
From the data of satellite infrared sounder measurements for VAC and radiative transfer calculations, we estimate optimal refractive index models of the volcanic ash material to simulate the measured brightness temperature spectrum. In addition, we have developed an algorithm of 1DVAR analysis (OVAA) that estimates the physical properties of VAC from the data of multi-wavelength satellite imager such as Himawari-8. By using the optimal RI model estimated by the infrared sounder and using OVAA, high accuracy Himawari-8 analysis for the physical parameters of VAC is expected.