Abstract
Abstract. The important role played by ground-based microwave weather radars for the monitoring of volcanic ash clouds has been recently demonstrated. The potential of microwaves from satellite passive and ground-based active sensors to estimate near-source volcanic ash cloud parameters has been also proposed, though with little investigation of their synergy and the role of the radar polarimetry. The goal of this work is to show the potentiality and drawbacks of the X-band dual polarization (DPX) radar measurements through the data acquired during the latest Grímsvötn volcanic eruptions that took place in May 2011 in Iceland. The analysis is enriched by the comparison between DPX data and the observations from the satellite Special Sensor Microwave Imager/Sounder (SSMIS) and a C-band single polarization (SPC) radar. SPC, DPX, and SSMIS instruments cover a large range of the microwave spectrum, operating respectively at 5.4, 3.2, and 0.16–1.6 cm wavelengths.
Highlights
The ability to recognize the signature of volcanic ash clouds on remote sensing data, and to retrieve quantitatively their physical parameters, is of significant importance
In this work ground radar and satellite radiometer observations at microwave frequencies are exploited for the study of volcanic eruptions
The main conclusions are as follows: i. radar acquisition at X-band can clearly detect the volcanic plume and the cloud spreading in the surrounding area of the Grímsvötn, which showed a horizontal extension of approximately 100 × 130 km; ii. dual polarization signatures from X-band radar data, DPX, are not easy to interpret
Summary
The ability to recognize the signature of volcanic ash clouds on remote sensing data, and to retrieve quantitatively their physical parameters, is of significant importance. Investigating the ash dispersion in the atmosphere from remote offers the practical advantage of monitoring it in near-real-time, avoiding impractical or even dangerous conditions of in situ sampling In this perspective, remote sensing observations provided by visible, infrared, and microwave remote sensors on either ground or satellite platforms are of particular interest. Either from ground or space, remote sensors operating at infrared and visible wavelengths suffer from strong ash cloud opacity (mixed with water cloud at times) due to the significant radiation extinction, which is often the case in the proximity of the volcanic source In this respect, the exploitation of passive microwave sensors represents a good opportunity to probe ash clouds, despite some inherent limitations (Delene et al, 1996; Grody and Basist, 1996; Marzano et al, 2012b; Montopoli et al, 2013).
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