Dielectric data in volcanic ash at weather radar wavelengths (centimeter range) are extremely sparse and are crucial for radar sensing of ash clouds and for imaging of volcanic terrains. This study extends previous data to include a wavelength range of 1.5-7.5 cm and volcanic ash compositions of 50-75 % silica. The real part of the complex permittivity, 2′, of volcanic ash is 6± 0.5 (1σ) for al...

Volcanic eruptions are important causes of natural variability in the climate system at all time scales. Assessments of the climate impact of volcanic eruptions by climate models almost universally assume that sulfate aerosol is the only radiatively active volcanic material. We report satellite observations from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the Cloud-Ae...

The Eyjafjallajökull (Iceland) volcanic eruption of April-May 2010 caused unprecedented air-traffic disruption in Northern Europe, revealing some important weaknesses of current operational ash-monitoring and forecasting systems and encouraging the improvement of methods and procedures for supporting the activities of Volcanic Ash Advisory Centers (VAACs) better. In this work, we compare two es...

BACKGROUND AND AIMS The Soufriere Hills volcano, Montserrat, has been erupting since July 1995 and volcanic ash has fallen on the island throughout most of the eruption. The ash contains substantial quantities of respirable particles and unusually large amounts (15-20%) of the crystalline silica mineral, cristobalite. The purpose of the surveys described here, undertaken between December 1996 a...

An open-ended coaxial probe is designed for making permittivity measurements on volcanic ash. Reference liquids such as water and methanol are used for calibrating the probe, whose input admittance is related to the complex permittivity by Marcuvitz integral. The reflection coefficient of the probe in the presence of volcanic ash samples from Etna volcano, Italy, is measured from 1 to 15 GHz an...

Volcanic ash was recovered from lower Aptian to Albian deposits from DSDP Sites 463, 465, and 466; pelagic clay of the upper Pleistocene to Upper Cretaceous was recovered mainly from Site 464, with minor amounts at Sites 465 and 466 (Figs. 1 and 2). We present X-ray-mineralogy data on pelagic clay and altered volcanic ash recovered from the four Leg 62 sites (Table 1; Fig. 1). In addition, two ...

Volcanic ash is emitted by most eruptions, sometimes reaching the stratosphere. In addition to its climate effect, ash may have a significant impact on civilian flights. Currently, the horizontal distribution of ash aerosols is quite extensively studied, but not its vertical profile, while of high importance for both applications mentioned. Here, we study the sensitivity of the thermal infrared...

Interactions with volcanic gases in eruption plumes produce soluble salt deposits on the surface of volcanic ash. While it has been postulated that saturation-driven precipitation of salts following the dissolution of ash surfaces by condensed acidic liquids is a primary mechanism of salt formation during an eruption, it is only recently that this mechanism has been subjected to detailed study....

The article represents a nice study treating the application of an Ensemble Kalman Filter on the prediction of volcanic ash plumes distal to the emission source, exploiting the observational information of aircraft-performed mass concentration measurements. This is innovative in terms of volcanic ash dispersion forecast improvements for aviation advice because it exploits real observational in-...

The article represents a nice study treating the application of an Ensemble Kalman Filter on the prediction of volcanic ash plumes distal to the emission source, exploiting the observational information of aircraft-performed mass concentration measurements. This is innovative in terms of volcanic ash dispersion forecast improvements for aviation advice because it exploits real observational in-...