Inside Volcanic Clouds: Remote Sensing of Ash Plumes Using Microwave Weather Radars

Abstract

Ash clouds due to volcanic eruptions can be detected in near-real time, quantitatively retrieved, and microphysically characterized by using ground-based microwave weather radars and their high-resolution spatial-temporal coverage.

Interpretation of observed microwave signatures from ground dual polarization radar and space multi-frequency radiometer for the 2011 Grímsvötn volcanic eruption

“…Note that the Grímsvötn eruption considered in this work and observed by the X-band dual polarization radar is a Plinian style event, and it was classified as class 4 at least within a range 0-8 in terms of volcanic explosive index (Newhall and Self 1982). On the contrary, the Etna event, considered in the introductory paper by Marzano et al (2013b) and observed by the same radar system used in this work, is a Strombolian style eruption that typically implies a VEI less than 3. Retrievals of mass loading from space observations obtained from the LEO passive Special Sensor Microwave Imager/Sounder (SSMIS) are compared with those derived using ground-based radars.…”

“…Weather radars are an example of such sensors whose use is increasing as an additional tool for volcanic cloud monitoring and quantitative retrieval of ash. A comprehensive overview of recent progress in radar volcanology is given by Marzano et al (2013b). That paper summarize the basis fundamentals of the radar-driven remote sensing of explosive volcanic eruptions, showing how quantitative estimates of ash category and concentration can be nowadays accomplished with a fairly good degree of confidence within the spatial coverage of weather radars.…”

“…These achievements were aimed at characterizing ash particles in terms of their shape, composition, density and particle size distribution, and they have led to a physically based retrieval scheme called volcanic ash radar retrieval (VARR). To support the potentials of VARR, Marzano et al (2013b) analysed five case studies observed by weather radars at S, C and X frequency bands from various eruptions all over the world. These are the eruptions that occurred in November 2004 in Iceland from the Grímsvötn volcano, in January 2006 in Alaska from the Augustine volcano, in April 2010 in Iceland from the Eyjafjöll volcano, in April 2011 in Italy from the Etna volcano, and finally in May 2011 again from the Grímsvötn volcano.…”

“…All the aforementioned eruptive case studies provide examples of weather radar signatures at different frequency bands and radar-derived ash products. However, Marzano et al (2013b) give an overview of the ashrelated radar products without going into detail of radar data processing. Additionally, four out of the five volcanic eruption events were discussed in terms of the single polarization radar data.…”

Characterization of Mediterranean hail-bearing storms using an operational polarimetric X-band radar

“…Use of weather radar for hail detection began in the 1950s with single-polarization techniques for analyzing echo intensity, spatial structure, and time evolution (Cook, 1958;Douglas and Hitschfeld, 1958). Mason (1971) suggested a 55 dBZ reflectivity threshold as an indicator of the presence of hail in S-band radars. A refinement of the relationship between the 45 dBZ level above the freezing layer and the occurrence of hail at the ground (Waldvogel et al, 1979) has been used by the Weather Surveillance Radar-1988 Doppler (WSR-88D) single-polarization systems.…”