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Main Topics






Combining Data




Atmospheric Trajectory Models

PUFF Volcanic Ash Model

Model Description

PUFF is a trajectory model developed for tracking ash clouds for hazard mitigation, especially to aircraft. Developed specifically for the Alaska region, the model is designed to provide near real-time information on the 3-D position of relatively young ( < 48 hours old) ash clouds on relatively fine temporal and spatial resolutions. The model can be used as a forecast tool to predict cloud migration and dispersion, an operational tool that provides near real-time volcanic cloud positions, and as a research tool for studying the behavior of ash in the atmosphere.

The PUFF model uses LaGrangian random walk formulations to calculate a trajectory for a user-specified number of particles that independently sample wind data from a 4-dimensional (latitude, longitude, height, time) data set. In addition, turbulent diffusion and particle fallout are also accounted for.

Model Input

The 4-dimensional wind fields used in PUFF are derived from National Meteorological Center (NMC) twice-daily forecast runs that are available in a number of formats and models. Three current data sets used in the model are the Unidata Grid Model 77 (available through UCAR) the Nested Grid Model (NGM), and the Aviation model (AVN). However, any data set that can be mapped to a 4-D grid is acceptable to the model.

The user must also specify simulation time, the number of ash particles, the vertical distribution of ash particles, and the ash size distribution. Default values exist for most inputs to expedite model output during emergency situations.

Model Output

The model creates one binary file for every requested forecast interval that includes each particle's 3-D position, size, and age. The format of the file facilitates display in a number of visualization software packages. Click here for an example of PUFF output.

Can I run the model myself?

Currently, there is not an on-line version of the model, but one is being developed. In the mean time, model runs can be requested for specific locations and dates on the PUFF home page.


Searcy, C., Dean, K., and Stringer, W., 1998, PUFF: A high-resolution volcanic ash tracking model, Journal of Volcanology and Geothermal Research, 80, 1-16.

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