Geoscience Reference
In-Depth Information
several volcanoes in different sounding conditions and various types of volcanic activity,
from Strombolian lava jets to weak ash plumes. They are meant to illustrate the many
capabilities of this type of radar and the interpretation of the variety of Doppler signatures
in terms of volcanic processes.
2. Radar monitoring of explosive eruptions
2.1 Ash plume hazards and tephra dispersal forecast
Volcanic ash plumes generate important hazards as widespread ash fallout may cause
serious perturbations to surrounding population and infrastructures. In addition, volcanic
ash clouds derived from eruptive columns, even of moderate size, can generate direct
hazards to aviation, as recently highlighted by the 2010 Eyjafjöll eruption in Iceland. The air
traffic was disrupted over Europe for several days, causing a loss of about 1.7 billion dollars
to airliners. Although no significant damage to aircraft was reported for this eruption, over
120 aircraft encounters with volcanic ash have nevertheless been documented between 1973
and 2008 (Schneider, 2009). The tracking of large ash clouds has therefore become a main
concern in the last decades, as attested by the creation of Volcanic Ash Advisory Centers
(VAAC) to provide their expertise to civil aviation in case of significant volcanic eruptions.
Volcanic ash transport and dispersion (VATD) models are used to forecast the location and
movement of ash clouds over hours to days in order to define hazards to aircraft and to
communities downwind. Inputs are eruption source parameters such as plume height, mass
eruption rate, duration, and mass fraction of fine ash (Mastin et al., 2009). Values of such
parameters are frequently unconstrained in the first minutes or hours after an eruption is
detected, and also change during an eruption (e.g. plume height), requiring rapid
reevaluation. Dispersion model forecast are routinely validated, verified against all available
observations, including field observations, combination of tephra deposits analysis and
theoretical models, or in-situ measurements and sampling (aircraft). However remotely-
sensed measurements by satellite imagery, ground-based radars and lidars, or better a
combination of all, are the most efficient tools for real-time response owing to their
continuous data acquisition and potential for automatic processing and rapid parameter
quantification (Fig. 1).
Fig. 1. Synergetic potential of integrated remote-sensing techniques for ash plume
monitoring. Photo: Sabancaya volcano, courtesy of J.-L. Le Pennec.
