Remote sensing of particle load

Remote sensing ash plume dynamics and quantification of particle load. Transportable Doppler radars enable to characterise the plume dynamics at high time resolution and retrieve the tephra load (e.g. Gouhier & Donnadieu, 2008). Several 23.5 cm-wavelength OPGC radars could be used: one can be deployed on any active volcano, another being permanently monitoring near-source (eruptive column) tephra plumes of Etna (Donnadieu et al., 2016), which is opportunely offering various eruption styles. A high spatio-temporal resolution millimeter-wave radar optimized for ash detection and already tested successfully on weak plumes at Stromboli (Donnadieu et al., EGU 2016; Freret-Lorgeril et al., subm. to Geology) will make it possible to measure ash concentrations in combination with disdrometers (or even to characterize pure degassing plumes involving liquid H2O). 3-D scans, or 2-D scans combined with wind velocity, will provide the cloud height and thickness along with the total erupted ash mass, these source term parameters being directly utilizable in input of dispersion models. Other weather radars could be opportunely used to track large ash plumes in Europe. Importantly, the characterized ash content can further be used to quantify the measurement errors on gas amounts using infrared and UV methods. Finally, combinations of radars at different wavelengths could help to understand better the variable partitioning between explosively emitted tephra at the source and the fraction of ash transported in the atmosphere and causing most hazards.