Sébastien VALADE

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Mr. Sébastien VALADE

Function: Post doctoral research fellow

Participation in ClerVolc program N°: 1

Main Research Unit: LMV

E-mail:

Presentation

I am a ClerVolc post-doctoral research fellow at the Laboratoire Magmas et Volcans, University Blaise Pascal in Clermont-Ferrand. Over the past few years, my research interests have focused on volcanic ash plumes, from remote sensing observations through to numerical modeling of these. My PhD work has investigated the source mechanisms and emission dynamics of volcanic pyroclastic emissions. This was mainly done throughout the use of a ground-based Doppler radar (VOLDORAD), specifically designed for the sounding of volcanic eruptive jets. Numerical modeling of pyroclastic emissions (i.e. ballistic particles and wind-drifted ash plumes), and simulation of synthetic radar signals resulting from these, have shown that the radar informs on both the internal dynamics of pyroclastic emissions and on the mass fraction prone to be ejected in the atmosphere . Inversion modeling procedures (i.e. near-neighborhood Monte Carlo algorithms) have been used to give constrains on eruptive parameters, such as the size, trajectory, exit velocities and source gas velocities of the pyroclasts, as well as the speed / direction of the ash cloud drifted by trade winds.

My Postdoctoral work on the other hand, uses infrared cameras to inform on the dynamics of small scale ash plumes. A freeware (plumeTracker) has been designed to track and analyze the plumes through time, and extract descriptive parameters such as the ascent velocities, volume, spreading rate, air entrainment coefficient, heat budget, ash mass loading, etc… Recently, in collaboration with Matteo Cerminara from INGV Pisa, we have reconstructed synthetic two-dimensional thermal images of volcanic plumes from analytical one-dimensional models. These have then compared with, and fitted to, thermal images of real plumes in order to recover the best input parameters, such as the source ash mass, particle size distribution and air entrainment coefficient.

Research Topics

Publications

  • Valade, S. and F. Donnadieu (2011). Ballistics and ash plumes discriminated by Doppler radar, Geophysical Research Letters, 38, L22301, doi:10.1029/2011GL049415.
  • Valade, S., Donnadieu, F., Lesage, P., Mora, M. M., Harris, A. and G. E. Alvarado (2012). Explosion mechanisms at Arenal volcano, Costa Rica: an interpretation from integration of seismic and Doppler radar data, Journal of Geophysical Research, doi:10.1029/2011JB008623.
  • Donnadieu, F., Valade, S. and S. Moune (2011). Three dimensional transport speed of wind-drifted ash plumes using ground-based radar, Geophysical Research Letters, 38, L18310, doi:10.1029/2011GL049001.
Sébastien VALADE

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