USE OF AUTOMATIC NUMERICAL DISPERSION/FALLOUT MODELS TO INFORM PUBLIC OF ASHFALL HAZARD

The Alaska Volcano Observatory (AVO) has long used numerical models of volcanic ash dispersion to inform and guide scientists in preparing volcanic activity products for public release or to advise other agencies in preparing their hazard alerts and information statements. Publicly displaying numerical results of ash dispersion and fallout models, however, can lead to misunderstandings of actual hazards. Primary points of confusion center around two issues: the distinction between automated hypothetical eruptions and the current estimate of an actual event; and the distinction between the areas affected by ash fallout and that by airborne ash. The USGS has developed a numerical model (Ash3d) to improve our calculations of volcanic ash fallout. Recently, AVO has added automatically generated output graphics from this model to its public webpages of volcanic activity for volcanoes at an elevated level of unrest. Ash3d-derived maps of ashfall thickness and airborne cloud load are displayed alongside similar maps derived from two independent numerical models (Puff and Hysplit). Each graphic is accompanied by brief descriptions of the model, simple guidelines for interpretation, and links to more detailed descriptions. These model graphics are also displayed with links to the public AVO ashfall reporting webpage so that model output can be compared with real-time observations of citizen-scientists. The initial reaction to the new products have been favorable, although the products have yet to be tested during events of high public interest.