Volcanic Cloud/Atmosphere Interactions: The First Week

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RoseEAR-0106875Volcanic eruptions produce complex clouds of gas, ash and aerosol mixtures which can be observed in the Earth's atmosphere for minutes to years. Their dynamics, and the chemistry and physics of their evolution, are poorly known yet form the basis for our understanding and mitigation of aircraft hazards, local to regional health effects from fallout, and the potential for global climatic impact. Because the combination of volcanologic, geographic, and atmospheric settings is largely unique for each event, a process-oriented study combining observations, modeling, and laboratory efforts, is warranted.In this proposal, we plan to integrate remote sensing studies of several key examples of volcanic clouds from activity of the past 10 years. We combine numerical models of volcanic eruptions that include microphysical processes, ground-based observations of fallout materials, direct sampling of the clouds, meteorological data and lab-based studies of ash/ice particles. Emphasis is placed on the evolution of volcanic clouds during a period lasting hours to about one week. The direct results of our efforts are expected to clarify issues related to the mechanisms of fallout and hazards of fine ash, the conversion of SO2 to sulfate, and the role of ice in various reactions and processes. The results are important in understanding a wide range of local and global scale environmental effects of eruptions, ranging from livestock poisoning to respiratory disease to hypercanes to climate change to mass extinctions. They are also significant to the mitigation of hazards to aircraft. We focus on four eruptions, all for which we have amassed considerable observational data and experience, and which span a range of volcanic and atmospheric environments: (1) The February 26, 2000 Hekla fissure eruption, which represents an ash-poor example and which fortuitously has important validation information associated with it; (2) The December 26, 1997 eruption at Soufriere Hills Volcano, Montserrat, which is marked by significant interaction with the ocean; (3) The three 1992 subplinian Spurr eruptions which have unusually extensive and complete observational constraints; and (4) The climactic June 15, 1991 Pinatubo event, the largest well-documented eruption of the past century.