HR: 09:30h
AN: V21E-07    [Abstracts]
TI: Plumes and Wind I: Jetstream Interaction and Implications for Air Traffic
AU: * Bursik, M
EM: mib@buffalo.edu
AF: Department of Geology, 876 Natural Sciences Complex University of Buffalo, Buffalo, NY 14260, United States
AU: Kobs, S E
EM: sekobs@buffalo.edu
AF: Department of Geology, 876 Natural Sciences Complex University of Buffalo, Buffalo, NY 14260, United States
AB: Volcanic plumes interact with the wind at all scales. On smaller scales, wind affects local eddy structure; on larger scales, wind shapes the entire plume trajectory. The polar jets or jetstreams are regions of high eastbound winds that span the globe from 30 to 60 degrees in latitude, centered at an altitude of about 10 km. They can be hundreds of kilometers wide, but as little as 1 km in thickness. Core windspeeds are up to 130 m/s. Modern transcontinental and transoceanic air routes are configured to take advantage of the jetstream. Eastbound jets can save both time and fuel by flying within it. Using both an integral model of plume motion that is formulated within a plume-centered coordinate system (BENT) as well as the Active Tracer High-resolution Atmospheric Model (ATHAM), we have calculated plume trajectories and rise heights under different wind conditions. Model plume trajectories compare well with the observed plume trajectory of the Sept 30/Oct 1, 1994, eruption of Kliuchevskoi Volcano, Kamchatka, Russia, for which measured maximum windspeed was 30--40 m/s at about 12 km. Tephra fall patterns for some prehistoric eruptions of Avachinskiy Volcano, Kamchatka, and Inyo Craters, CA, USA, are anomalously elongated and inconsistent with simple models of tephra dispersal in a windfield, but are modeled well by BENT. The numerical experiments suggest that over a wide range of mass eruption rates, from ~ 10⁶ to ~ 10⁸ kg/s, plumes rise between 9 and 11 km. In a still atmosphere, the rise height over this range of mass eruption rate increases from 17 to 33 km. This effect is caused in large part by the enhanced entrainment from the wind, as well as by plume bending. Two potentially useful observations can be made about air routes and volcanic eruption plumes under jetstream conditions. The first is that by taking advantage of the jetstream, aircraft are flying within an airspace that is also preferentially occupied by volcanic eruption clouds and particles. The second is that, because eruptions with highly variable mass eruption rate pump volcanic particles into the jetstream under these conditions, it is difficult to characterize the maximum size, grain size distribution and mass loading that might be present within a downwind volcanic plume or cloud that has interacted with the jetstream. Furthermore, anomalously large particles and high mass loadings could be present within the cloud, if it was in fact formed by an eruption with a high mass eruption rate.
DE: 8409 Atmospheric effects (0370)
DE: 8428 Explosive volcanism
DE: 8488 Volcanic hazards and risks
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting