Model DescriptionThe Volcanic Ash Forecast Transport and Dispersion Model (VAFTAD) was developed by the Air Resources Laboratory (ARL) of the National Oceanic and Atmospheric Administration (NOAA) for forecasting the visual transport of volcanic ash clouds. The operational use of VAFTAD has been transferred to the National Weather Service to support operations at the Anchorage and Washington Volcanic Ash Advisory Centers (VAAC). VAFTAD results are used to alert aircraft and avoid aviation encounters with volcanic clouds.
VAFTAD is a 3-dimensional Eularian model that calculates the advection and dispersion of volcanic ash
using meteorological and volcanological data. Incorporated into the model are an ash distribution function,
vertical and horizontal advection, gravitational settling of ash, ash diffusion, and ash-air concentrations.
The model computes a "visual" ash cloud that has been calibrated by comparing model-calculated concentrations
with satellite images. The magnitude of the eruption (calculated using user-input of ash column height) is
also utilized in the model. A detailed description of the model can be found on the
VAFTAD Information page.
A list of user-defined input is located on the VAFTAD
Information page. Most input is volcanological information such as the volcano location, height of the
eruption column, and the date of the eruption. The location of the volcano can be specified using latitude/longitude coordinates,
picking a location on a map, or selecting a volcano name from an extensive database.
VAFTAD results may also be posted for current eruptions
within the Washington and Anchorage VAAC areas of responsibility. VAFTAD results are also posted on the web
for hypothetical eruptions of certain volcanoes
within the Washington and Anchorage VAAC areas of responsibility.
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