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.

爆炸性火山喷发中的灰烬含有有关火山导管中岩浆动态的信息，在发生破碎的关键区域，并确定了喷发样式。尽管Ash和Scoria的形态学和岩石学特征为爆炸性基本喷发的机制提供了见解，但有关不同机制之间过渡的重要问题仍未得到解答。理解灰分组合物的三种方法是：李子光谱法，块状李子颗粒样品的化学分析和颗粒显微镜。这些技术中的第一个是经历其提供洞察力的能力的步骤，原因有两个。首先，来自火山灰样品的高分辨率折射率数据正在通过NERC资助的项目获得。尽管该数据对项目并不重要，但它允许使用已知喷发（例如Grimsvötn）的样品的折射率来生成用于检索卫星测量值的火山灰云特性的光学性质。其次，高分辨率红外光谱仪现在以足够的频率观察地球，以至于在偏远位置进行了很好的观察到，例如厄立特里亚的2011年纳布罗爆发。该项目最初将基于科学文献和新的ASH测量值中的现有信息来构建灰光学特性的数据库（灭绝系数，单个散点反照函数和相位功能）。然后，这些特性将构成灰分组合物，光学厚度和高分辨率红外光谱的有效半径的最佳估计类型检索的基础。检索算法将针对三种不同类型的观察开发：1）火山通风口附近的灰分的高分辨率红外传输光谱。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。2）来自红外大气发声干涉仪（IASI）在板载Metop卫星上的高分辨率红外发射光谱。 IASI是一种Nadir查看傅里叶变换光谱仪，覆盖光谱范围645至2760 cm-1（3.62-15.5微米）。 IASI视野由50 x 50 km的正方形内部的四个直径为20 km的电路组成，名义上可以在12小时内实现全球覆盖范围。3）3）高分辨率红外发射光谱，来自米歇尔森干涉仪的高分辨率红外发射光谱，用于被动大气响料（MIPAS）Onboard Envisat estellite satellite。 MIPA在从2002年到现在的6-68 km的切线高度范围内，从685-2410 cm-1（14.5至4.1微米）测量大气肢体发射光谱。使用这些仪器，我们将观察到由几个不同火山产生的火山灰，在不同的阶段和不同的爆发行为。基于卫星的灰分性能估计值将通过将其与灰分样品测得的灰分以及与其他卫星结果进行比较来验证。我们进行相关测量的喷发包括Eyjafjallajökull，Grimsvötn，Nabro和Puyehue。然后，观察到的灰分行为将用灰烬生成的火山过程来解释。