Graduation Year


Document Type




Degree Granting Department


Major Professor

Graham A. Tobin, Ph.D.

Co-Major Professor

Arlene G. Laing, Ph.D.

Committee Member

Charles B. Connor, Ph.D.

Committee Member

Steven Reader, Ph.D.


Volcanology, Meteorology, Volcanic ash, Climatology, Atmospheric diffusion, Mesoscale modeling, Computer modeling


Models of tephra fallout are used to assess volcanic hazards in advance of eruptions and in near-real-time. Current models often approximate the wind field using simplistic assumptions of the atmosphere that cannot account for typical variations in wind velocity that occur in time and three-dimensional space. Here, a widely used mesoscale atmospheric model is used to improve forecasts of the location of the major axis of dispersion for erupting plumes. The Pennsylvania State University-National Center for Atmospheric Research fifth-generation Mesoscale Model (MM5) specializes in atmospheric prediction for regions on the order of ten to hundreds of kilometers on a side. MM5 generates realistic wind fields based on the laws of conservation of mass, energy, and momentum, along with land surface data and atmospheric forecasts and observations. It is particularly effective at resolving circulation patterns in areas with sparse meteorological observations, and/or mountainous terrain. MM5 is applied to the 1995 eruption of Cerro Negro, Nicaragua. Estimates of particle settling velocities are used in conjunction with MM5-derived wind fields to forecast the plume track. Particle trajectories generated from MM5 winds are compared to those produced by other wind models. The complex wind fields generated by MM5 explain non-linear plume dispersion. MM5 winds are shown to be more accurate than the other models in reproducing the observed tephra deposit, and satellite imagery is used to confirm the accuracy of MM5 winds. The appropriate application of meteorological data sets and mesoscale models should ultimately improve the utility of tephra fallout hazard assessments, especially in the absence of abundant meteorological observations.