33. Modeling Volcanic Ash Plumes and Fallout for Improved Hazard Assessment and Forecasting

The dispersal of volcanic ash is a major hazard to aviation and infrastructure in areas downwind of erupting volcanoes.  Volcanic ash hazards to aviation are significant and command the attention of volcano observatories that work with volcanic ash advisory centers throughout the world to model and forecast the trajectories of ash clouds.  The models currently in use require information on the rate of ash loading in the atmosphere, its vertical distribution above the vent, and its grain size, as source parameters.  Presently, these parameters are not well constrained for many types of eruptions and this limits the ability of existing models to accurately forecast the temporal and spatial characteristics of ash clouds and ash fallout.

Eruption source parameters can be inferred from satellite images, seismic or other monitoring data, or from empirical equations that relate plume height and eruption rate. Such methods provide reasonable estimates of plume height and eruption rate in strong vertical plumes with associated umbrella clouds.  Estimates of eruption source parameters are less certain for weak plumes that rise slowly and are bent over by wind.  Weak plumes are the most common type of ash plume and they typically develop during small volume eruptions, which occur more frequently than eruptions that produce strong plumes. Thus, an important component of the proposed project is to evaluate the eruption source conditions for eruptions that produce weak plumes.

Sedimentation from volcanic ash clouds is currently addressed using  advection diffusion models, in which a constant diffusion coefficient controls the rate of widening of the fall deposit with distance from the vent. This coefficient approximates dispersion that results from local eddies and variations in the wind field; but experience has found that its value must be adjusted from one eruption to another, limiting its accuracy in predicting the pattern of tephra deposition a priori.

Because volcanic ash is such an important hazard, improved plume models are needed.  We seek a candidate who can develop models of ash cloud dispersal that can better predict tephra deposit patterns and provide more realistic relations between plume height and eruption rate or mass tephra distribution for aviation hazards assessment.  The candidate should have a strong background in numerical modeling, fluid dynamics, and turbulent processes and should be familiar with existing approaches to modeling ash clouds and ash fallout.  Potential candidates also should be able to integrate model results with visual observations, satellite data, tephra deposit studies, and new technologies such as Doppler radar. Tephra deposit studies, satellite data, and archived wind-field patterns from several well-studied eruptions in the past few decades are available for analysis and study.

The type of model and method of solution are open to the candidate.  Open-source, multi-phase codes such as Clawpack and ATHAM are available, as are collaborative arrangements with other institutions as can be arranged by the candidate and the USGS.  Plume models may be integrated with microscale meteorological models such as NCAR’s WRF model that can simulate local wind fields, or with larger-scale models of tephra dispersal such as PUFF or HYSPLIT.

Proposed Duty Station: Anchorage, AK; Vancouver, WA

Areas of Ph.D.: Volcanology, physics, fluid mechanics, applied mathematics, geophysics, geology

Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Geophysicist, Research Physicist

(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Research Advisor(s): Chris Waythomas, (907) 786-7122, cwaythomas@usgs.gov; Larry Mastin, (360) 993-8925, lgmastin@usgs.gov

Human Resources Office contact: Candace Azevedo, (916) 278-9393, caazevedo@usgs.gov

Summary of Opportunities