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Spectrally High resolution Infrared measurements for the characterisation of Volcanic Ash (SHIVA): a new way to study volcanic processes

用于表征火山灰 (SHIVA) 的光谱高分辨率红外测量：研究火山过程的新方法

基本信息

批准号：
NE/J023310/1
负责人：
Roy Grainger
金额：
$ 41.01万
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FJ023310%2F1
关键词：
Spectrally resolution Infrared measurements characterisation

项目摘要

Ash from explosive volcanic eruptions holds information about magma dynamics within volcanic conduits, in the critical zone where fragmentation occurs and eruption style is decided. Although morphological and petrological features of ash and scoria have provided insights into the mechanisms of explosive basaltic eruptions, important questions on the transition between different mechanisms are still unanswered. Three approaches to understanding ash composition are: plume spectrometry, chemical analysis of bulk plume particle samples and particle microscopy. The first of these techniques is experiencing a step change in its ability to provide insight for two reasons. Firstly, high resolution refractive index data from volcanic ash samples is becoming available through a NERC funded project. While this data is not critical to the project, it allows the refractive indices of samples from a known eruption (e.g. Grimsvötn) to be used to generate the optical properties that are used in the retrieval of the properties of the volcanic ash cloud from satellite measurements. Secondly, high resolution infrared spectrometers now observe the Earth with sufficient frequency that recent eruption in remote locations have been well observed, e.g. the 2011 eruption of Nabro in Eritrea. The project will initially construct a database of ash optical properties (extinction coefficient, single scatter albedo and phase function) based on existing information in the scientific literature and new ash measurements. These properties will then form the basis of an optimal estimation type retrieval of ash composition, optical thickness and effective radius from high resolution infrared spectra. The retrieval algorithm will be developed for three different types of observation:1) High resolution infrared transmission spectra of ash near the volcanic vent. These spectra are provided by our project partners who will assist in the interpretation of the measurements.2) High resolution infrared emission spectra from the Infrared Atmospheric Sounding Interferometer (IASI) onboard MetOp satellite. IASI is a nadir viewing Fourier transform spectrometer that covers the spectral range 645 to 2760 cm-1 (3.62-15.5 microns). The IASI field of view consists of four circles of 20 km diameter inside a square of 50 x 50 km, and nominally it can achieve global coverage in 12 hours.3) High resolution infrared emission spectra from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT satellite. MIPAS measures atmospheric limb emission spectra from 685-2410 cm-1 (14.5 to 4.1 microns) over a tangent altitude range 6-68 km from 2002 to the present.Using these instruments we will observe volcanic ash generated by several different volcanoes and during different stages of eruptive behaviour. The satellite based estimates of ash properties will be validated by comparing them to ash properties measured from ash samples as well as by comparison with other satellite results. Eruptions for which we have correlative measurements include Eyjafjallajökull, Grimsvötn, Nabro and Puyehue. The observed ash behaviour will then be interpreted in terms of the ash-generating volcanic processes.

火山爆发产生的火山灰包含了火山管道内岩浆动力学的信息，这些信息位于发生碎裂和决定喷发方式的关键地带。尽管火山灰和火山渣的形态学和岩石学特征为玄武岩爆发机制提供了新的见解，但关于不同机制之间的过渡的重要问题仍然没有答案。了解火山灰成分的三种方法是：羽流光谱法、对大量羽流颗粒样品进行化学分析和颗粒显微镜检查。其中第一种技术在提供洞察力的能力上正在经历一个台阶式的变化，原因有二。首先，通过NERC资助的一个项目，可以获得火山灰样品的高分辨率折射率数据。虽然这一数据对该项目并不重要，但它允许利用已知喷发（如Grimsvötn）样本的折射率来生成光学特性，用于从卫星测量结果中检索火山灰云的特性。其次，高分辨率红外光谱仪现在以足够的频率观察地球，最近在偏远地区的火山爆发得到了很好的观察，例如2011年厄立特里亚Nabro火山爆发。该项目将根据科学文献中的现有信息和新的灰测量结果，初步建立一个灰光学特性数据库（消光系数、单次散射系数和相位函数）。这些属性将形成一个最佳的估计类型检索的基础上，灰成分，光学厚度和有效半径从高分辨率红外光谱。将为三种不同类型的观测开发反演算法：1）火山口附近火山灰的高分辨率红外透射光谱。这些光谱由我们的项目合作伙伴提供，他们将协助解释测量结果。2）来自MetOp卫星上红外大气探测干涉仪（IASI）的高分辨率红外发射光谱。IASI是一种最低点观察傅里叶变换光谱仪，覆盖光谱范围645至2760 cm-1（3.62-15.5微米）。IASI的视场由一个50 x 50公里的正方形内的四个直径为20公里的圆圈组成，名义上它可以在12小时内实现全球覆盖。MIPAS从2002年至今在6-68公里的切线高度范围内测量685-2410厘米-1（14.5至4.1微米）的大气临边发射光谱，我们将利用这些仪器观测几个不同火山在喷发行为的不同阶段产生的火山灰。将通过与从火山灰样品测得的火山灰特性以及与其他卫星结果进行比较，验证基于卫星的火山灰特性估计值。我们进行了相关测量的喷发包括Eyjafjallajökull、Grimsvötn、Nabro和Puyehue。观察到的火山灰行为将被解释为火山灰生成过程。