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Abstract The Icelandic Meteorological Office maintains a national network of webcams designed and built in house for environmental monitoring. During the 2021 Fagradalsfjall eruption these cameras, along with a temporary near-field network of commercial cameras installed by the Department of Civil Protection and Emergency Management, were used to estimate the height of the $$SO_2$$ S O 2 plume and lava fountain. Here we present the webcam designs, the techniques used to calibrate them, and the messaging system and web interface that allow near real time measurements to be made from the images. With this system we were able to make estimates of heights with an accuracy on the order of tens to a few hundreds of meters with a lag typically of five to ten minutes at up to ten minute intervals when weather conditions were favorable. The plume heights were then used to constrain the performance of the $$SO_2$$ S O 2 dispersion model used for air quality forecasts while fountain heights were used to delineate danger zones where visitors at the eruption site were in danger of being hit by ballistic clasts.

The mass eruption rate (MER) of an explosive volcanic eruption is a commonly used quantifier of the magnitude of the eruption, and estimating it is important in managing volcanic hazards. The physical connection between the MER and the rise height of the eruption column results in a scaling relationship between these quantities, allowing one to be inferred from the other. Eruption source parameter datasets have been used to calibrate the relationship, but the uncertainties in the measurements used in the calibration are typically not accounted for in applications. This can lead to substantial over- or under-estimation. Here we apply a simple Bayesian approach to incorporate uncertainty into the calibration of the scaling relationship using Bayesian linear regression to determine probability density functions for model parameters. This allows probabilistic prediction of mass eruption rate given a plume height observation in a way that is consistent with the data used for calibration. By using non-informative priors, the posterior predictive distribution can be determined analytically. The methods and datasets are collected in a python package, called merph. We illustrate their use in sampling plausible MER—plume height pairs, and in identifying usual eruptions. We discuss applications to ensemble-based hazard assessments and potential developments of the approach. • A Bayesian linear regression is applied to eruption source parameter datasets. • Inference of mass eruption rate from plume height can be obtained with a quantification of uncertainty. • Analytical forms for the Posterior Predictive distributions facilitate analysis and sampling. • Observational uncertainty can be included in prediction. [ABSTRACT FROM AUTHOR]

Abstract At many volcano observatories, measurements of the plume height are frequently applied. On the other hand, the recent development of the satellite measurements enables the monitoring of the SO2 mass emitted by the passive degassing at sufficient temporal resolution. Using these two techniques, this study focuses on the degassing activity before the 8 October 2016 phreatomagmatic eruption of Aso volcano, Japan. Here we show the temporal variations of the plume height, the SO2 mass, and ground-based SO2 flux during 6 months before the eruption. Our result shows similar temporal changes of them, especially for the maxima and the increase, respectively, in about 2 months and 6 days before the eruption. This result indicates that the degassing system had been stable during the whole study period, but the accumulation of volcanic gas in the conduit since August might trigger the phreatomagmatic eruption. These techniques can be sufficient to monitor the degassing activity and to detect its precursory change.

We present three‐dimensional numerical simulations of eruption clouds from circular to linear fissure vents to investigate the control of vent shape on the height and stability of volcanic plumes during large explosive eruptions. Our results show that clouds ejected from circular or low‐aspect‐ratio (nearly square‐like) fissure vents can be associated with radially suspended flow (RSF) at the top of the jet region, whereas those emitted from narrow‐fissure vents are not. Non‐RSF plumes are more stable than those associated with RSF because the highly concentrated parts of the ejected mixture are easily dissipated and mixed with air near the vent. Plume height in the RSF regime decreases while that in the non‐RSF regime increases with increasing aspect ratio, even for a fixed magma flow rate. These observations suggest that the efficiency of air entrainment is influenced by the vent shape, which in turn controls the dynamics of eruption plumes. Plain Language Summary: Explosive volcanic eruptions eject hot mixtures of gas and ash, forming eruption clouds. Eruption clouds can either become buoyant and rise upward as kilometer‐scale volcanic plumes, from which they release ash and gas into the atmosphere, or flow downward along the ground, resulting in devastating pyroclastic flows. Understanding the dynamics of eruption clouds and the critical conditions for generating pyroclastic flows versus volcanic plumes is an important focus of modern volcanology research. We present numerical simulations of eruption clouds using a three‐dimensional numerical model to investigate the effects of volcanic vent geometry on plume stability and height. Our simulation results indicate that plume height depends on the shape of the volcanic vent and can have different dynamics even for the same eruption intensity. These effects of vent shape are caused by the complex mechanism of mixing between the eruption cloud and the ambient air. The efficiency of such mixing inside the cloud largely controls the critical conditions for the generation of pyroclastic flows; above a critical mass flow rate, clouds ejected from circular vents can generate pyroclastic flows, whereas those ejected from thin fissure vents develop stable volcanic plumes. Key Points: Three‐dimensional numerical simulations reveal the effects of volcanic vent shape on plume stability and plume heightPlumes from narrow fissures are more stable than those from circular vents owing to more efficient dissipation mechanisms near the ventPlume height has complex dependency on vent aspect ratio because of changes in the efficiency of air entrainment [ABSTRACT FROM AUTHOR]

In the Central Andes, large Plinian eruptions (Volcanic Explosivity Index ≥ 5) occur at a relatively high frequency, i.e. average one every 2000 to 4000 years over the past 50,000 years in Peru. Such recurring explosive activity represents a significant challenge for regions typically hosting several million people (e.g. Southern Peru, Western Bolivia and Northern Chile). With VEI 6, the 1600 CE Huaynaputina eruption is considered the largest historical eruption in South America. We have re-examined the first Plinian phase of this eruption in order to better assess critical eruption source parameters (i.e. erupted volume, plume height, mass eruption rate, eruption duration).The revised bulk volume of the tephra-fall deposit associated with the Plinian phase is approximately 13–14 km3, almost twice the previous estimate (7–8 km3 within the 1 cm isopach) based on methods including power law, Weibull function and Bayesian linear regression. Tephra was dispersed by strong winds to the WNW as far as 400 km on Peruvian territory and then in the Pacific Ocean. Seven villages were buried, killing ~ 1500 people. The revised plume height estimate, 32.2 ± 2.5 km, is consistent with the early estimations. As a result, the Huaynaputina 1600 CE first eruption phase lies in the upper part of the Plinian field close to the ultra-Plinian transition, making this event one of the largest in the past millennium which coincides with results from recent studies on palaeoclimatic impacts. [ABSTRACT FROM AUTHOR]

Multi-sensor strategies are key to the real-time determination of eruptive source parameters (ESPs) of explosive eruptions necessary to forecast accurately both tephra dispersal and deposition. To explore the capacity of these strategies in various eruptive conditions, we analyze data acquired by two Doppler radars, ground- and satellite-based infrared sensors, one infrasound array, visible video-monitoring cameras as well as data from tephra-fallout deposits associated with a weak and a strong paroxysmal event at Mount Etna (Italy). We find that the different sensors provide complementary observations that should be critically analyzed and combined to provide comprehensive estimates of ESPs. First, all measurements of plume height agree during the strong paroxysmal activity considered, whereas some discrepancies are found for the weak paroxysm due to rapid plume and cloud dilution. Second, the event duration, key to convert the total erupted mass (TEM) in the mass eruption rate (MER) and vice versa, varies depending on the sensor used, providing information on different phases of the paroxysm (i.e., unsteady lava fountaining, lava fountain-fed tephra plume, waning phase associated with plume and cloud expansion in the atmosphere). As a result, TEM and MER derived from different sensors also correspond to the different phases of the paroxysms. Finally, satellite retrievals for grain-size can be combined with radar data to provide a first approximation of total grain-size distribution (TGSD) in near real-time. Such a TGSD shows a promising agreement with the TGSD derived from the combination of satellite data and whole deposit grain-size distribution (WDGSD).

Biofilm formation is a dynamic process that leads to mature communities over time. Despite a general knowledge of biofilm community formation and the resultant limitations of antibiotic therapy, there is a paucity of data describing specific plume heights, surface coverage and rates of maturation. Furthermore, little is published on the effect that the broth medium might have on the degree of biofilm maturation. In this study, three strains of methicillin-resistant Staphylococcus aureus (MRSA) (USA300, USA400 and a clinical isolate) were grown in brain heart infusion broth (BHI) or tryptic soy broth (TSB). Following growth, SEM images were captured for 3-D analysis to assess plume height. TSB produced significantly higher plume heights of USA300 and USA400 compared to BHI. Broth type was less influential on the clinical isolate. The data indicate that broth type and time may be important factors to consider when assessing maturation and plume height formation of MRSA biofilms. [ABSTRACT FROM AUTHOR]

Abstract Plume height is an important parameter routinely used to characterize and classify explosive eruptions. Though the strategies to estimate key eruption source parameters such as erupted volume and mass flow rate have evolved over the past few decades, the determination of plume height of past eruptions is still mostly based on empirical approaches that do not account for the new developments in plume modelling based on the interaction of plume and wind. Here we present a revised strategy for the retrieval of plume height from field data that accounts for key aspects of plume dynamics and particle sedimentation, which include: i) the effect of wind advection on the buoyant plume, ii) a new parameterization of the gravitational spreading of the umbrella cloud for distances smaller than the radius of the plume, iii) the effect of particle shape on particle sedimentation, iv) the effect of different atmospheric profiles in different climate zones, v) three-dimensional wind, temperature and pressure data, and vi) topography. In particular, as wind can affect the dynamics and height of the plume, new computed sedimentation patterns are more complex and result in non-linear relationships between downwind and crosswind deposition. Our method is tested against observations of the 2011 eruption of Shinmoedake (Japan), the 1980 eruption of Mount St Helens (USA), and the 1991 eruption of Pinatubo (Philippines). These are well-constrained examples of small, intermediate, and high intensity eruptions, respectively. Intensity scenarios are introduced to account for the non-unique relation between plume height and particle sedimentation resulting from wind advection of volcanic plumes. We further demonstrate that needle-like and disk-like particle shapes can have downwind distances 36 to 70% larger than the equivalent spheres. In addition, we find that the effect of latitude on the determination of plume height is more significant for low and intermediate intensity scenarios with a discrepancy between 7 and 20%. Highlights • A new revised numerical strategy for the determination of plume height is presented. • Accounting for wind, particle shape, gravitational spreading and climate zone. • Wind significantly affects the clast support envelope of weak and transitional plumes. • The new method is available through a Matlab package and a series of nomograms. [ABSTRACT FROM AUTHOR]

For the prediction of the ventilation rate for removing the non-isothermal concentrated fume from the semi-enclosed space, the computational fluid dynamics (CFD) analysis was done. Securing the proper ventilation conditions in emergency state such as in fire is crucial factor for the protection of the resident in the space. In the analysis for the determining the proper ventilation rate, the experimental study had the limitation for simulating the versatile conditions of fume development. The theoretical and computational method had been chosen as the alternate tool for the experimental analysis. In this study, the CFD analysis was done on the defined model which already had been done the experimental analysis by the previous workers. By comparing the prediction on the plume heights and the ventilation rates by the CFD analysis at, and in the parametric model of 1 m³ with those of the previous experimental works, the feasibility of the computational analysis was evaluated. For the required ventilation rate analyzed by the CFD analysis was over predicted in 7.1% difference with that of the experimental results depending on the different plume height. With the comparison with the analytical Zukoski model at, the CFD analysis on the ventilation was under predicted in 8.3%. By the verification of the feasibility of the CFD analysis, the extended analysis was done for getting the extra information such as the water vapor distribution and CO2 distribution in the semi-enclosed spaces. [ABSTRACT FROM AUTHOR]

Volcanic eruptions represent a significant source of atmospheric aerosols and can display local, regional and global effects, impacting earth systems and human populations. In order to assess the relative impacts of these events, accurate plume injection altitude measurements are needed. In this work, volcanic plumes generated from seven Kamchatka Peninsula volcanoes (Shiveluch, Kliuchevskoi, Bezymianny, Tolbachik, Kizimen, Karymsky and Zhupanovsky), were identified using over 16 years of Multi-angle Imaging SpectroRadiometer (MISR) measurements. Eighty-eight volcanic plumes were observed by MISR, capturing 3–25% of reported events at individual volcanoes. Retrievals were most successful where eruptive events persisted over a period of weeks to months. Compared with existing ground and airborne observations, and alternative satellite-based reports compiled by the Global Volcanism Program (GVP), MISR plume height retrievals show general consistency; the comparison reports appear to be skewed towards the region of highest concentration observed in MISR-constrained plume vertical extent. The report observations display less discrepancy with MISR toward the end of the analysis period (2013–2016), with improvements in the suborbital data likely the result of the deployment of new instrumentation. Conversely, the general consistency of MISR plume heights with conventionally reported observations supports the use of MISR in the ongoing assessment of volcanic activity globally, especially where ground-based observations are unavailable. Differences between the northern (Shiveluch, Kliuchevskoi, Bezymianny and Tolbachik) and southern (Kizimen, Karymsky and Zhupanovsky) volcanoes broadly corresponding to the Central Kamchatka Depression (CKD) and Eastern Volcanic Front (EVF) geological sub-regions of Kamchatka, respectively, are distinguished by varying magma composition. For example, by comparison with reanalysis-model simulations of local meteorological conditions, CKD plumes were generally less constrained by mid-tropospheric (< 6 km) layers of vertical stability above the boundary layer, suggesting that these eruptions were more energetic than those in the EVF region. [ABSTRACT FROM AUTHOR]

The Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard the Terra satellite acquires imagery at 275-m resolution at nine angles ranging from 0° (nadir) to 70° off-nadir. This multi-angle capability facilitates the stereoscopic retrieval of heights and motion vectors for clouds and aerosol plumes. MISR’s operational stereo product uses this capability to retrieve cloud heights and winds for every satellite orbit, yielding global coverage every nine days. The MISR INteractive eXplorer (MINX) visualization and analysis tool complements the operational stereo product by providing users the ability to retrieve heights and winds locally for detailed studies of smoke, dust and volcanic ash plumes, as well as clouds, at higher spatial resolution and with greater precision than is possible with the operational product or with other space-based, passive, remote sensing instruments. This ability to investigate plume geometry and dynamics is becoming increasingly important as climate and air quality studies require greater knowledge about the injection of aerosols and the location of clouds within the atmosphere. MINX incorporates features that allow users to customize their stereo retrievals for optimum results under varying aerosol and underlying surface conditions. This paper discusses the stereo retrieval algorithms and retrieval options in MINX, and provides appropriate examples to explain how the program can be used to achieve the best results.

Regardless of the recent advances in geophysical monitoring and real-time quantitative observations of explosive volcanic eruptions, the characterization of tephra deposits remains one of the largest sources of information on Eruption Source Parameters (ESPs) (i.e. plume height, erupted volume/mass, Mass Eruption Rate — MER, eruption duration, Total Grain-Size Distribution — TGSD). ESPs are crucial for the characterization of volcanic systems and for the compilation of comprehensive hazard scenarios but are naturally associated with various degrees of uncertainties that are traditionally not well quantified. Recent studies have highlighted the uncertainties associated with the estimation of ESPs mostly related to: i) the intrinsic variability of the natural system, ii) the observational error and iii) the strategies used to determine physical parameters. Here we review recent studies focused on the characterization of these uncertainties and we present a sensitivity analysis for the determination of ESPs and a systematic investigation to quantify the propagation of uncertainty applied to two case studies. In particular, we highlight the dependence of ESPs on specific observations used as input parameters (i.e. diameter of the largest clasts, thickness measurements, area of isopach contours, deposit density, downwind and crosswind range of isopleth maps, and empirical constants and wind speed for the determination of MER). The highest uncertainty is associated to the estimation of MER and eruption duration and is related to the determination of crosswind range of isopleth maps and the empirical constants used in the empirical parameterization relating MER and plume height. Given the exponential nature of the relation between MER and plume height, the propagation of uncertainty is not symmetrical, and both an underestimation of the empirical constant and an overestimation of plume height have the highest impact on the final outcome. A ± 20% uncertainty on thickness measurements, area of isopach contours, integration limit for the power-law fit and deposit density result in ESP uncertainties ≤± 20% for plume height and erupted volume/mass. Finally, a third case study has also been used to explore the sensitivity of the Voronoi Tessellation strategy for the determination of TGSD and the inversion on both mass/area and grain-size data for the determination of erupted mass and plume height. Results confirm the validity of the methods but also the strong dependence on the distribution and number of observations. [ABSTRACT FROM AUTHOR]

Constraining physical parameters of tephra dispersion and deposition from explosive volcanic eruptions is a significant challenge, because of both the complexity of the relationship between tephra distribution and distance from the vent and the difficulties associated with direct and comprehensive real-time observations. Three andesitic subplinian explosions in January 2011 at Shinmoedake volcano, Japan, are used as a case study to validate selected empirical and theoretical models using observations and field data. Tephra volumes are estimated using relationships between dispersal area and tephra thickness or mass/area. A new cubic B-spline interpolation method is also examined. Magma discharge rate is estimated using theoretical plume models incorporating the effect of wind. Results are consistent with observed plume heights (6.4-7.3 km above the vent) and eruption durations. Estimated tephra volumes were 15-34 × 10 m for explosions on the afternoon of 26 January and morning of 27 January, and 5.0-7.6 × 10 m for the afternoon of 27 January; magma discharge rates were in the range 1-2 × 10 kg/s for all three explosions. Clast dispersal models estimated plume height at 7.1 ± 1 km above the vent for each explosion. The three subplinian explosions occurred with approximately 12-h reposes and had similar mass discharge rates and plume heights but decreasing erupted magma volumes and durations. [ABSTRACT FROM AUTHOR]

Abstract: During the sub-plinian eruptions of Mt. Shinmoedake (Japan) on 26–27 January 2011 a significant amount of ash was emitted into the atmosphere, destroying thousands of hectares of farm land, causing air traffic disruption, and forcing the closure of four railroad lines located around the volcano. In this work, a retrospective analysis of these eruptive events is presented, exploiting the high temporal resolution of the Japanese Multi-functional Transport Satellites (MTSAT) data to study thermal volcanic activity, to identify and track volcanic ash, and to determine the cloud-top height, inferring information about eruption features and space-time evolution. We show that a strong and sudden increase in the thermal signal occurred at Mt. Shinmoedake as a consequence of above mentioned eruptive events, generating hot spots timely detected by the RSTVOLC algorithm for the first time implemented here on data provided by geostationary satellites. This study also shows that the emitted ash plume, identified by means of the RSTASH algorithm, strongly fluctuated in altitude, reaching a maximum height around 7.4km above sea level, in agreement with information provided by the Tokyo VAAC. The plume heights derived in this work, by implementing the widely accepted cloud-top temperature method, appear also compatible with the values provided by independent weather radar measurements, with the main differences characterizing the third sub-plinian event that occurred in the afternoon of 27 January. The estimates of discharge rate, the temporal trend of ash affected areas, and the results of thermal monitoring reported in this work seem to indicate that the third sub-plinian event was the least intense. In spite of some limitations, this study confirms the potential of Japanese geostationary satellites in effectively monitoring volcanoes located in the West Pacific region, providing continuous information also about such critical parameters of ash clouds as the plume height. Such information is useful not only for driving numerical models, forecasting ash dispersion into the atmosphere, but also for characterizing eruption features and dynamics. [Copyright &y& Elsevier]

The Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard the Terra satellite acquires imagery at 275-m resolution at nine angles ranging from 0° (nadir) to 70° off-nadir. This multi-angle capability facilitates the stereoscopic retrieval of heights and motion vectors for clouds and aerosol plumes. MISR's operational stereo product uses this capability to retrieve cloud heights and winds for every satellite orbit, yielding global coverage every nine days. The MISR INteractive eXplorer (MINX) visualization and analysis tool complements the operational stereo product by providing users the ability to retrieve heights and winds locally for detailed studies of smoke, dust and volcanic ash plumes, as well as clouds, at higher spatial resolution and with greater precision than is possible with the operational product or with other space-based, passive, remote sensing instruments. This ability to investigate plume geometry and dynamics is becoming increasingly important as climate and air quality studies require greater knowledge about the injection of aerosols and the location of clouds within the atmosphere. MINX incorporates features that allow users to customize their stereo retrievals for optimum results under varying aerosol and underlying surface conditions. This paper discusses the stereo retrieval algorithms and retrieval options in MINX, and provides appropriate examples to explain how the program can be used to achieve the best results. [ABSTRACT FROM AUTHOR]

Abstract: During operational ash-cloud forecasting, prediction of ash concentration and total erupted mass directly depends on the determination of mass eruption rate (MER), which is typically inferred from plume height. Uncertainties for plume heights are large, especially for bent-over plumes in which the ascent dynamics are strongly affected by the surrounding wind field. Here we show how uncertainties can be reduced if MER is derived directly from geophysical observations of source dynamics. The combination of infrasound measurements and thermal camera imagery allows for the infrasonic type of source to be constrained (a dipole in this case) and for the plume exit velocity to be calculated (54–142m/s) based on the acoustic signal recorded during the 2010 Eyjafjallajökull eruption from 4 to 21 May. Exit velocities are converted into MER using additional information on vent diameter (50±10m) and mixture density (5.4±1.1kg/m3), resulting in an average ∼9×105 kg/s MER during the considered period of the eruption. We validate our acoustic-derived MER by using independent measurements of plume heights (Icelandic Meteorological Office radar observations). Acoustically derived MER are converted into plume heights using field-based relationships and a 1D radially averaged buoyant plume theory model using a reconstructed total grain size distribution. We conclude that the use of infrasonic monitoring may lead to important understanding of the plume dynamics and allows for real-time determination of eruption source parameters. This could improve substantially the forecasting of volcano-related hazards, with important implications for civil aviation safety. [Copyright &y& Elsevier]

Research on height variation of plumes, which were formed by near free-surface underwater explosion of small TNT equivalent, has been done. With 0.6 g RDX cylindrical charge, underwater explosion experiments were carried out at 14 detonation depth. Using two synchronous high speed video cameras, the water movement and bubble images were recorded and the height variations of plumes versus explosion depth and rising time were achieved through further data processing. By dimensionless treatment and polynomial fitting method, the engineering calculation model of the dimensional height was obtained. Comparing the calculated results with experimental ones for charge RDX of 1 kg weight, the error was less than 5%. Research results show that the obtained engineering calculation model of the dimensionless plume is more versatile than Swisdak calculation formula. It is suitable for the height engineer calculation of near free-surface underwater explosion with small equivalent charge. [ABSTRACT FROM AUTHOR]

Physical parameters of explosive eruptions are typically derived from tephra deposits. However, the characterization of a given eruption relies strongly on the quality of the dataset used, the strategy chosen to obtain and process field data and the particular model considered to derive eruptive parameters. As a result, eruptive parameters are typically affected by a certain level of uncertainty and should not be considered as absolute values. Unfortunately, such uncertainty is difficult to assess because it depends on several factors and propagates from field sampling to the application and interpretation of dispersal models. Characterization of explosive eruptions is made even more difficult when tephra deposits are poorly exposed and only medial data are available. In this paper, we present a quantitative assessment of the uncertainty associated with the characterization of tephra deposits generated by the two largest eruptions of the last 2,000 years of Cotopaxi volcano, Ecuador. In particular, we have investigated the effects of the determination of the maximum clast on the compilation of isopleth maps, and, therefore, on the characterization of plume height. We have also compared the results obtained from the application of different models for the determination of both plume height and erupted volume and for the eruption classification. Finally, we have investigated the uncertainty propagation into the calculation of mass eruption rate and eruption duration. We have found that for our case study, the determination of plume height from isopleth maps is more sensitive to the averaging techniques used to define the maximum clast than to the choice of dispersal models used (i.e. models of Carey and Sparks ; Pyle ) and that even the application of the same dispersal model can result in plume height discrepancies if different isopleth lines are used (i.e. model of Carey and Sparks ). However, the uncertainties associated with the determination of erupted mass, and, as a result, of the eruption duration, are larger than the uncertainties associated with the determination of plume height. Mass eruption rate is also associated with larger uncertainties than the determination of plume height because it is related to the fourth power of plume height. Eruption classification is also affected by data processing. In particular, uncertainties associated with the compilation of isopleth maps affect the eruption classification proposed by Pyle (), whereas the VEI classification is affected by the uncertainties resulting from the determination of erupted mass. Finally, we have found that analytical and empirical models should be used together for a more reliable characterization of explosive eruptions. In fact, explosive eruptions would be characterized better by a range of parameters instead of absolute values for erupted mass, plume height, mass eruption rate and eruption duration. A standardization of field sampling would also reduce the uncertainties associated with eruption characterization. [ABSTRACT FROM AUTHOR]

A method is described for estimating the two-dimensional spatial distribution of volcanic SO2 using thermal infrared image data acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). The author proposes a new method to estimate wind velocity and plume height using an along-track stereoscopic pair image. Volcanic SO2 flux can be estimated from the spatial distribution of SO2 and wind velocity. Since ASTER has both the Thermal Infrared Radiometer (TIR) and stereoscopic viewing function in the along-track direction, the volcanic SO2 flux can be estimated from the ASTER data alone. These methods are applied to the Miyakejima volcano, Japan. The SO2 flux derived from ASTER is around 5×104 ton/day (580 kg s-1), which is slightly larger than the value derived from COSPEC. The plume height estimation error may cause this disagreement because the SO2 estimation procedure is very sensitive to the plume height. [Copyright &y& Elsevier]

Multi-sensor strategies are key to the real-time determination of eruptive source parameters (ESPs) of explosive eruptions necessary to forecast accurately both tephra dispersal and deposition. To explore the capacity of these strategies in various eruptive conditions, we analyze data acquired by two Doppler radars, ground- and satellite-based infrared sensors, one infrasound array, visible video-monitoring cameras as well as data from tephra-fallout deposits associated with a weak and a strong paroxysmal event at Mount Etna (Italy). We find that the different sensors provide complementary observations that should be critically analyzed and combined to provide comprehensive estimates of ESPs. First, all measurements of plume height agree during the strong paroxysmal activity considered, whereas some discrepancies are found for the weak paroxysm due to rapid plume and cloud dilution. Second, the event duration, key to convert the total erupted mass (TEM) in the mass eruption rate (MER) and vice versa, varies depending on the sensor used, providing information on different phases of the paroxysm (i.e., unsteady lava fountaining, lava fountain-fed tephra plume, waning phase associated with plume and cloud expansion in the atmosphere). As a result, TEM and MER derived from different sensors also correspond to the different phases of the paroxysms. Finally, satellite retrievals for grain-size can be combined with radar data to provide a first approximation of total grain-size distribution (TGSD) in near real-time. Such a TGSD shows a promising agreement with the TGSD derived from the combination of satellite data and whole deposit grain-size distribution (WDGSD). [ABSTRACT FROM AUTHOR]

Volcanoes are complex environmental systems that pose challenges to scientific study, due to their inherently hazardous nature and in many cases, remote locations. Satellite-based remote sensing provides a useful tool for assessing both ongoing activity and retrospective eruptions. This paper represents an initial application of a multi-sensor approach, in part to demonstrate its strengths and limitations in a single volcanic region that is fairly well monitored in situ. We utilize data from five NASA satellite-based instruments, having up to 18 years of global observations, to conduct in-depth investigations of eight volcanoes on the Kamchatka Peninsula (Russia) that were active between 2000 and 2018. From 169 eruptive plumes observed, we performed detailed plume-dynamics analysis in eighty-two cases for which sufficiently favorable observations were obtained. Plume heights from MISR and CALIOP, microphysical particle properties (e.g. fine ash, sulfates) from MISR, thermal anomalies generated by lava features from MODIS, and sulfur dioxide (SO 2) concentrations from OMI and OMPS are all considered. Evidence of eruption evolution over months-to-years was identified at Shiveluch, Kliuchevskoi, Kizimen, Karymsky, Zhupanovsky, Koryaksky and Kambalny. In cases with extensive data coverage (Kliuchevskoi, Kizimen, Karymsky and Zhupanovsky), underlying subsurface dynamics is inferred, corroborated where possible with detailed ground-based data records. The 1.1 km resolution of the particle property retrievals from the Multi-angle Imaging SpectroRadiometer (MISR) instrument capture downwind plume-particle evolution in many cases. Comparison of changes in aerosol optical depth (AOD), retrieved effective particle size (REPS) and retrieved effective particle absorption (REPA) map to six plume transport regimes, indicating varying degrees of downwind particle aggregation, deposition, and/or new particle formation. Distinct meteorological conditions are identified as likely driving these evolutionary processes, most notably the atmospheric static stability and wind shear at plume altitude. This approach can be applied to volcanic plumes globally, including those for which surface monitoring is limited or entirely absent. • Creation of a robust technique for volcanic assessment using multiple satellites. • Multi-sensor technique highlighted geological evolution at individual volcanoes. • Comparison between volcanoes linked emissions to underlying geological dynamics. • Downwind plume particle retrievals isolated seven plume transportation regimes. • Plume transportation regimes linked to ambient static stability and wind shear. [ABSTRACT FROM AUTHOR]