Peter W. Webley

Predicting and Validating the Tracking of a Volcanic Ash Cloud during the 2006 Eruption of Mt. Augustine Volcano

On 11 January 2006, Mount Augustine volcano in southern Alaska began erupting after 20-year repose. The Anchorage Forecast Office of the National Weather Service (NWS) issued an advisory on 28 January for Kodiak City. On 31 January, Alaska Airlines cancelled all flights to and from Anchorage after multiple advisories from the NWS for Anchorage and the surrounding region. The Alaska Volcano Observatory (AVO) had reported the onset of the continuous eruption. AVO monitors the approximately 100 active volcanoes in the Northern Pacific. Ash clouds from these volcanoes can cause serious damage to an aircraft and pose a serious threat to the local communities, and to transcontinental air traffic throughout the Arctic and sub-Arctic region. Within AVO, a dispersion model has been developed to track the dispersion of volcanic ash clouds. The model, Puff, was used operational by AVO during the Augustine eruptive period. Here, we examine the dispersion of a volcanic ash cloud from Mount Augustine across Alaska from 29 January through the 2 February 2006. We present the synoptic meteorology, the Puff predictions, and measurements from aerosol samplers, laser radar (or lidar) systems, and satellites. UAF aerosol samplers revealed the presence of volcanic aerosols at the surface at sitesmorexa0» where Puff predicted the ash clouds movement. Remote sensing satellite data showed the development of the ash cloud in close proximity to the volcano and a sulfur-dioxide cloud further from the volcano consistent with the Puff predictions. Lidars showed the presence of volcanic aerosol with consistent characteristics aloft over Alaska and were capable of detecting the aerosol, even in the presence of scattered clouds and where the cloud is too thin/disperse to be detected by remote sensing satellite data. The lidar measurements revealed the different trajectories of ash consistent with the Puff predictions. Dispersion models provide a forecast of volcanic ash cloud movement that might be undetectable by any other means but are still a significant hazard. Validation is the key to assessing the accuracy of any future predictions. The study highlights the use of multiple and complementary observations used in detecting the trajectory ash cloud, both at the surface and aloft within the atmosphere.«xa0less

Unified model intercomparison for volcanic ash transport modelling

Our group is pursuing a volcanic ash transport model intercomparison study to evaluate the relative performance of several atmospheric transport models for selected case studies. These intercomparisons require the definition of standard output formats for producing results in a common framework. We define here the common format and develop a set of evaluation tools, allowing for side-by-side comparisons on a level playing field and providing a platform for further quantitative evaluation. The tools developed have widespread applicability to a number of ATM activities and are demonstrated in the realm of volcanic ash transport modelling. The Crater Peak, Mount Spurr eruption of 1992, Alaska, is used as a case study, employing HYSPLIT, FLEXPART and PUFF with common meteorological driving data, and with releases and intrinsic-model set-ups as similar as possible.