Using Satellite Data to Determine Empirical Relationships between Volcanic Ash Source Parameters

Meelis J Zidikheri,Chris Lucas

doi:10.3390/atmos11040342

Abstract

Poor knowledge of dispersion model source parameters related to quantities such as the total fine ash mass emission rate, its effective spatial distribution, and particle size distribution makes the provision of quantitative forecasts of volcanic ash a difficult problem. To ameliorate this problem, we make use of satellite-retrieved mass load data from 14 eruption case studies to estimate fine ash mass emission rates and other source parameters by an inverse modelling procedure, which requires multidimensional sampling of several thousand trial simulations with different values of source parameters. We then estimate the dependence of these optimal source parameters on eruption height. We show that using these empirical relationships in a data assimilation procedure leads to substantial improvements to the forecasts of ash mass loads, with the use of empirical relationships between parameters and eruption height having the added advantage of computational efficiency because of dimensional reduction. In addition, the use of empirical relationships, which encode information in satellite retrievals from past case studies, implies that quantitative forecasts can still be issued even when satellite retrievals of mass load are not available in real time due to cloud cover or other reasons, making it especially useful for operations in the tropics where ice and water clouds are ubiquitous.

Highlights

Due to the hazards posed by volcanic ash on airborne aircraft, the monitoring and forecasting of volcanic ash is a key service for the aviation industry [1]
The Australian Bureau of Meteorology provides this service through the Darwin Volcanic Ash Advisory Centre (VAAC), one of nine such centers globally
(13 in the Darwin VAAC region and one in the Wellington VAAC region), are used as the base data to enable the estimation of the relationships between various source parameters and eruption height

Summary

Introduction

Due to the hazards posed by volcanic ash on airborne aircraft, the monitoring and forecasting of volcanic ash is a key service for the aviation industry [1]. The Australian Bureau of Meteorology provides this service through the Darwin Volcanic Ash Advisory Centre (VAAC), one of nine such centers globally. It is responsible for issuing volcanic ash advisories in the volcanically active region covering Indonesia, Papua New Guinea, and the southern Philippines. The volcanic ash advisories issued by the VAACs comprise polygon coordinates that identify the regions of contaminated airspace. These advisories are qualitative in the sense that no estimates of the amount of ash in the contaminated region are provided. Quantitative forecasts will enable aircraft operators to better manage the risks of flying through regions of airspace with some likelihood of ash contamination

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