Detection of plumes at Redoubt and Etna volcanoes using the GPS SNR method

Larson, Kristine M.; Palo, S. E.; Roesler, Carolyn; Mattia, M.; Bruno, Valentina; Coltelli, M.; Fee, David

doi:10.1016/j.jvolgeores.2017.04.005

Cited by 17 publications

(28 citation statements)

References 26 publications

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“…Note, however, that even with highly charged particles, large attenuations are more readily observed for the densest of flows (i.e., those with mass loading in the range of 10–100 g/m 3 ), suggesting that L‐band signals are most affected by particle jets which are either very dense or proximal. Such inference conforms well with observations at Etna and Redoubt (Larson et al, ). At Redoubt, signals that traversed small, dilute plumes did not display important attenuations.…”

Section: Discussionsupporting

confidence: 92%

“…The modified Mie model presented here suggests that the excess charge on particles may have been responsible for the attenuations observed at Redoubt and Etna. In agreement with Larson et al (), our model consistently predicts that uncharged ash clouds will produce attenuation coefficients below or at the lower limit of those observed in the field for ash‐sized pyroclasts. Large attenuations do occur for higher mass loadings, but require an abundance of clasts with diameters of several tens of centimeters (large peaks on the left in Figures ).…”

Section: Discussionsupporting

confidence: 91%

“…Using a simple model, however, these authors showed that (for the parameter set used) the total path attenuation caused by the presence of silicates and ice would only be on the order of 1 dB. Larson et al () suggest that this discrepancy may be resolved by including larger particle sizes into their model. Here, we show that large scatterers are not required to attenuate L‐band radiation if a plume comprises micron‐to‐millimeter‐sized grains that are electrostatically charged.…”

Section: Introductionmentioning

confidence: 98%

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The Effect of Electrostatic Charge on the Propagation of GPS (L‐band) Signals Through Volcanic Plumes

et al. 2019

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Recent field studies have shown that the presence of ash in the atmosphere can produce measurable attenuation of Global Positioning System (GPS) signals (Aranzulla et al., 2013, https://doi.org/10.1007/s10291-012-0294-4; Larson, 2013, https://doi.org/10.1002/grl.50556; Larson et al., 2017, https://doi.org/10.1016/j.jvolgeores.2017.04.005). The ability to detect plumes using GPS is appealing because many active volcanoes are already instrumented with high‐quality receivers. However, analyses using a Ralyeigh approximation have shown that the large attenuations cannot be explained by the scattering and absorption associated with ash or hydrometeors alone. Here, we show that the extinction of GPS signals, which fall into the L‐band of the electromagnetic spectrum, may be exacerbated significantly by excess surface charge on pyroclasts. Indeed, volcanic eruptions are often accompanied by a range of electrostatic processes, leading, in some cases, to spectacular lightning storms. We use a modified Mie scattering model to demonstrate that electrostatic effects can increase the extinction of L‐band radiation by up to an order of magnitude, producing attenuations consistent with those observed in the field. Thus, future work involving GPS as a tool to remotely probe plumes must take into account the electrification of ash in radiative transfer models. Additionally, we propose that the sensitivity of GPS to particle charging may catalyze the development of new techniques to explore electrostatic processes in plumes, especially if GPS measurements are complemented with millimeter‐wave RADAR measurements.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 98%

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The Effect of Electrostatic Charge on the Propagation of GPS (L‐band) Signals Through Volcanic Plumes

et al. 2019

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“…Larson et al, (2017, Appendix A) model signal path extinction as a superposition of absorption and scattering for particle diameters much smaller than the radiation wavelength (Rayleigh scattering). For instance, if the particles were purely tephra with similar complex dielectric permittivity as used by Larson et al (2017), particle diameters would range between 6.2 and 13.5 mm. If we knew the effective dielectric properties of the scatterers, which are likely aggregates of ash, and water or ice (see below), we could estimate a range of likely particle diameters in the plume at these high altitudes.…”

Section: Snr and Phase Residual Comparisonmentioning

confidence: 99%

“…Two effects are notable: (1) signal refraction causes a phase delay, which can induce artificial position offsets in the GNSS time series (Aranzulla et al, 2013;Grapenthin et al, 2013;Houlié, Briole, Nercessian, Murakami, & Union, 2005), and (2) scattering and attenuation lower the signal-to-noise ratio (SNR) commonly recorded by GNSS receivers (Larson, 2013;Larson et al, 2017;Ohta & Iguchi, 2015). Rapid detection and characterization of ash clouds are valuable components of volcano monitoring and hazard assessment.…”

Section: Introductionmentioning

confidence: 99%

Volcanic Hail Detected With GPS: The 2011 Eruption of Grímsvötn Volcano, Iceland

Grapenthin

Hreinsdóttir

Eaton

2018

Geophysical Research Letters

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Volcanic plumes are challenging to detect and characterize rapidly, but insights into processes such as hail formation or ash aggregation are valuable to hazard forecasts during volcanic crises. Global Navigation Satellite System (GNSS, which includes GPS) signals traveling from satellites to ground receivers can be disturbed by volcanic plumes. To date, two effects aiding plume detection from GNSS observations have been described: (a) ash‐rich plumes scatter the signal, lowering the signal‐to‐noise ratio (SNR), and (b) some plumes refract and thus delay GNSS signals. Using GNSS data from the VEI 4 2011 Grímsvötn eruption, we show that tephra and water contents of plumes distinctly affect SNR and phase residuals. The signals suggest high‐altitude freezing of plume water into volcanic hail—corroborated by 1‐D modeling and volcanic hail deposits. Combining GNSS SNR and phase residual analyses is valuable for detecting processes that rapidly scrub fine ash out of the atmosphere.

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The Global Navigation Satellite System (GNSS): Positioning, Velocities, and Reflections

Grapenthin

2022

Preprint

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Detection of plumes at Redoubt and Etna volcanoes using the GPS SNR method

Cited by 17 publications

References 26 publications

The Effect of Electrostatic Charge on the Propagation of GPS (L‐band) Signals Through Volcanic Plumes

The Effect of Electrostatic Charge on the Propagation of GPS (L‐band) Signals Through Volcanic Plumes

Volcanic Hail Detected With GPS: The 2011 Eruption of Grímsvötn Volcano, Iceland

The Global Navigation Satellite System (GNSS): Positioning, Velocities, and Reflections

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