The effect of phase changes of water on the development of volcanic plumes

A complex thermodynamic-microphysical package has been formulated that is a ble to deal with the microphysical processes of condensed water vapour in a volcanic plume. The microphysics follows a prognostic bulk approach for cl oud water, cloud ice, rain and graupel and the interaction between them. In a standard experiment, this module, applied within a new nonhydrostatic vo lcano plume model, Active Tracer High Resolution Atmospheric Model (ATHAM), produces reasonable concentrations of different types of hydrometeors. Und er tropical conditions, the plume gains three times as much water from the environment through entrainment as from the volcanic source. The formed hyd rometeors are dominated by the ice phase. Thermodynamic effects of phase ch anges contribute about 13% to the plume's total thermal energy and therefor e have a considerable effect on the vertical development of the plume. (C) 1998 Elsevier Science B.V. All rights reserved.