Project 10

Volcanic ash emissions are a common phenomenon accompanying eruptions of many types. This ash consists of silicate particles that are produced from the fragmentation of magma as it is being expelled from the volcanic vent and present significant hazards: (1) potential damage to infrastructure when large quantities fall in proximity to the vent, (2) respiratory hazards for nearby populations and (3) hazards to commercial flights when injected at high altitudes. Volcanic Ash Advisory Centers (VAAC), tasked with monitoring volcanic ash emissions and providing timely forecasts to airline pilots, rely heavily on satellite imagery to quantify the mass of ash injected into the atmosphere and initiate atmospheric circulation models. Accurate ash retrievals require prior knowledge of the optical properties of ash, currently only characterized for a limited number of samples, because laboratory measurements are complex. In this project, we will develop a new method for deriving the optical properties of silicate ash using mixtures of natural samples and potassium bromide (KBr) powders. This new method is more repeatable and easier to implement and will lead to the creation of a large database of ash of many different types. This would not only help produce more accurate retrievals of ash from satellite imagery but would also enable investigations of the natural variability in optical properties found in natural samples.

The student will be trained in laboratory techniques top prepare the samples (sieving, crushing, etc.), make the KBr pellets and measure their
transmission in a Fouriet Transform Infrared (FTIR) spectrometer. They will help develop a robust and repeatable procedure to ensure the accuracy of the measurements. The student will also participate in the analysis of the data to derive the complex refractive index (n +i ) for each sample. Using a Mie or Rayleigh scattering model and a fitting algorithm, we will determine the best fit parameters for each sample. Once a large database exists, we will explore the natural variability found in all samples, and attempt to identify controlling factors to create a quantitative parameterization. We estimate this work will require a time commitment of 10h/week over the course of the year.

We expect this work will lead to the creation of a large database of optical properties of volcanic ash. Depending on student progress and the availability of samples, we expect this work will lead to: (1) a conference abstract presenting the initial results of the study (pending available funds, the student will be able to present those results at the conference); (2) the publication of a scientific paper in a peer-reviewed journal (on which the student will be an author), detailing the method and partial results; (3) the preparation of a research proposal to fund broader efforts to create a larger database (again we expect the student will be involved in this effort, and named as a participant if they wish); and (4) several subsequent publications focused on the application of the database to satellite retrievals of ash from recent eruptions and the parameterization efforts (the student will be involved in those efforts as they come to fruition as well).