FPLUME-1.0: An integrated volcanic plume model accounting for ash aggregation

Eruption source parameters (ESP) characterizing
volcanic eruption plumes are crucial inputs for atmospheric
tephra dispersal models, used for hazard assessment and
risk mitigation.We present FPLUME-1.0, a steady-state 1-D
(one-dimensional) cross-section-averaged eruption column
model based on the buoyant plume theory (BPT). The model
accounts for plume bending by wind, entrainment of ambient
moisture, effects of water phase changes, particle fallout and
re-entrainment, a new parameterization for the air entrainment
coefficients and a model for wet aggregation of ash particles
in the presence of liquid water or ice. In the occurrence
of wet aggregation, the model predicts an effective grain size
distribution depleted in fines with respect to that erupted at
the vent. Given a wind profile, the model can be used to determine
the column height from the eruption mass flow rate or
vice versa. The ultimate goal is to improve ash cloud dispersal
forecasts by better constraining the ESP (column height,
eruption rate and vertical distribution of mass) and the effective
particle grain size distribution resulting from eventual
wet aggregation within the plume. As test cases we apply the
model to the eruptive phase-B of the 4 April 1982 El Chichón
volcano eruption (México) and the 6 May 2010 Eyjafjallajökull
eruption phase (Iceland). The modular structure of the
code facilitates the implementation in the future code versions
of more quantitative ash aggregation parameterization
as further observations and experiment data will be available
for better constraining ash aggregation processes.

This work was partially supported by the
MED-SUV Project funded by the European Union (FP7 grant agreement no. 308665).