scholarly journals Sulphur dioxide as a volcanic ash proxy during the April–May 2010 eruption of Eyjafjallajökull Volcano, Iceland

2011 ◽  
Vol 11 (14) ◽  
pp. 6871-6880 ◽  
Author(s):  
H. E. Thomas ◽  
A. J. Prata
Keyword(s):  
Western Europe ◽  
Volcanic Ash ◽  
Final Phase ◽  
Middle Phase ◽  
Eruption Style ◽  
Infrared Imager ◽  
Cloud Monitoring ◽  
Volcanic Ash Cloud ◽  
Volcanic Cloud ◽  
Financial Losses

Abstract. The volcanic ash cloud from the eruption of Eyjafjallajökull volcano in April and May 2010 resulted in unprecedented disruption to air traffic in Western Europe causing significant financial losses and highlighting the importance of efficient volcanic cloud monitoring. The feasibility of using SO2 as a tracer for the ash released during the eruption is investigated here through comparison of ash retrievals from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) with SO2 measurements from a number of infrared and ultraviolet satellite-based sensors. Results demonstrate that the eruption can be divided into an initial ash-rich phase, a lower intensity middle phase and a final phase where considerably greater quantities both ash and SO2 were released. Comparisons of ash-SO2 dispersion indicate that despite frequent collocation of the two species, there are a number of instances throughout the eruption where separation is observed. This separation occurs vertically due to the more rapid settling rate of ash compared to SO2, horizontally through wind shear and temporally through volcanological controls on eruption style. The potential for the two species to be dispersed independently has consequences in terms of aircraft hazard mitigation and highlights the importance of monitoring both species concurrently.

scholarly journals Sulphur dioxide as a volcanic ash proxy during the April–May 2010 eruption of Eyjafjallajökull Volcano, Iceland

2011 ◽  
Vol 11 (3) ◽  
pp. 7757-7780 ◽  
Author(s):  
H. E. Thomas ◽  
A. J. Prata
Keyword(s):  
Western Europe ◽  
Volcanic Ash ◽  
Final Phase ◽  
Lower Intensity ◽  
Middle Phase ◽  
Eruption Style ◽  
Infrared Imager ◽  
Cloud Monitoring ◽  
Volcanic Ash Cloud ◽  
Volcanic Cloud

Abstract. The volcanic ash cloud from the eruption of Eyjafjallajökull volcano in April and May 2010 resulted in unprecedented disruption to air traffic in Western Europe causing significant monetary loses and highlighting the importance of efficient volcanic cloud monitoring. The feasibility of using SO2 as a tracer for the ash released during the eruption is investigated here through comparison of ash retrievals from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) with SO2 measurements from a number of infrared and ultraviolet satellite-based sensors. Results demonstrate that the eruption can be divided into an initial ash-rich phase, a lower intensity middle phase and a final phase where considerably greater quantities of both ash and SO2 were released. Comparisons of ash-SO2 dispersion indicate that despite frequent collocation of the two species, there are a number of instances throughout the eruption where separation is observed. This separation occurs vertically due to the more rapid settling rate of ash compared to SO2, horizontally through wind shear and temporally through volcanological controls on eruption style. The potential for the two species to be dispersed independently has consequences in terms of aircraft hazard mitigation and highlights the importance of monitoring both species concurrently.

scholarly journals Near-real-time volcanic cloud monitoring: insights into global explosive volcanic eruptive activity through analysis of Volcanic Ash Advisories

2021 ◽  
Vol 83 (2) ◽  
Author(s):  
S. Engwell ◽  
L. Mastin ◽  
A. Tupper ◽  
J. Kibler ◽  
P. Acethorp ◽  
...  
Keyword(s):  
Real Time ◽  
Volcanic Activity ◽  
Volcanic Ash ◽  
Source Parameters ◽  
Volcanic Eruptions ◽  
Volcanic Hazards ◽  
Process Data ◽  
Cloud Monitoring ◽  
Satellite Sensors ◽  
Volcanic Cloud

AbstractUnderstanding the location, intensity, and likely duration of volcanic hazards is key to reducing risk from volcanic eruptions. Here, we use a novel near-real-time dataset comprising Volcanic Ash Advisories (VAAs) issued over 10 years to investigate global rates and durations of explosive volcanic activity. The VAAs were collected from the nine Volcanic Ash Advisory Centres (VAACs) worldwide. Information extracted allowed analysis of the frequency and type of explosive behaviour, including analysis of key eruption source parameters (ESPs) such as volcanic cloud height and duration. The results reflect changes in the VAA reporting process, data sources, and volcanic activity through time. The data show an increase in the number of VAAs issued since 2015 that cannot be directly correlated to an increase in volcanic activity. Instead, many represent increased observations, including improved capability to detect low- to mid-level volcanic clouds (FL101–FL200, 3–6 km asl), by higher temporal, spatial, and spectral resolution satellite sensors. Comparison of ESP data extracted from the VAAs with the Mastin et al. (J Volcanol Geotherm Res 186:10–21, 2009a) database shows that traditional assumptions used in the classification of volcanoes could be much simplified for operational use. The analysis highlights the VAA data as an exceptional resource documenting global volcanic activity on timescales that complement more widely used eruption datasets.

scholarly journals Interpretation of Accurate UV Polarization Lidar Measurements: Application to Volcanic Ash Number Concentration Retrieval

2012 ◽  
Vol 29 (4) ◽  
pp. 558-568 ◽  
Author(s):  
A. Miffre ◽  
G. David ◽  
B. Thomas ◽  
M. Abou Chacra ◽  
P. Rairoux
Keyword(s):  
Volcanic Ash ◽  
Source Region ◽  
Number Concentration ◽  
Optical Remote Sensing ◽  
Polarization Measurements ◽  
Lidar Measurements ◽  
Volcanic Ash Cloud ◽  
Range Transport ◽  
Volcanic Cloud ◽  
Traditional Approaches

Abstract In this paper, accurate UV polarization measurements are performed on a volcanic ash cloud after long-range transport at Lyon, France (45.76°N, 4.83°E). The volcanic particles are released from the mid-April 2010 eruption of the Eyjafjallajökull Icelandic volcano (63.63°N, 19.62°W). The aerosol UV depolarization, which arises from nonspherical volcanic ash particles, serves as an independent means to discriminate ash from nonash particles in the volcanic cloud. This discrimination is only feasible if the intrinsic ash particle depolarization ration δash is accurately determined. In this paper, the δash value [δash = (40.5 ± 2.0)%] is derived from literature laboratory measurements on a scattering matrix to ensure ash particle specificity. It is shown that traditional approaches, based on direct lidar depolarization ratio δa measurements, are only valid very close to the source region, because δa may be very different from δash, when nonash particles are present. For the first time, observed lidar depolarization ratios, in the range from a few percent to 40%, are hence interpreted in comparison with δash taken as a reference. It is then shown how to use the sensitive and accurate UV polarization measurements to access to the size-averaged number concentration vertical profile of volcanic ash particles in the troposphere. Vertical profiles of the backscattering coefficient specific to volcanic ash particles, providing altitude-resolved ash particle number concentrations, are presented in the troposphere after optical scattering computation. This new methodology can be applied to other aerosols events and for other optical remote sensing experiments.

Automatic onsite imaging of volcanic ash particles with VOLCAT: Towards quasi-real-time eruption style monitoring

2021 ◽  
pp. 107267
Author(s):  
Takahiro Miwa ◽  
Nobuo Geshi ◽  
Jun'ichi Itoh ◽  
Toshikazu Tanada ◽  
Masato Iguchi
Keyword(s):  
Real Time ◽  
Volcanic Ash ◽  
Eruption Style

scholarly journals Volcanic ash cloud detection from space: a comparison between the RSTASHtechnique and the water vapour corrected BTD procedure

2011 ◽  
Vol 2 (3) ◽  
pp. 263-277 ◽  
Author(s):  
Alessandro Piscini ◽  
Stefano Corradini ◽  
Francesco Marchese ◽  
Luca Merucci ◽  
Nicola Pergola ◽  
...  
Keyword(s):  
Water Vapour ◽  
Volcanic Ash ◽  
Cloud Detection ◽  
Volcanic Ash Cloud ◽  
Ash Cloud

Volcanic ash detection and retrievals using SLSTR. Test case: 2019 Raikoke  eruption

2021 ◽  
Author(s):  
Ilaria Petracca ◽  
Davide De Santis ◽  
Stefano Corradini ◽  
Lorenzo Guerrieri ◽  
Matteo Picchiani ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Volcanic Ash ◽  
Thermal Infrared ◽  
Integrated Approach ◽  
Effective Radius ◽  
Volcanic Plume ◽  
Transfer Model ◽  
Volcanic Cloud

<p>When an eruption event occurs it is necessary to accurately and rapidly determine the position and evolution during time of the volcanic cloud and its parameters (such as Aerosol Optical Depth-AOD, effective radius-Re and mass-Ma of the ash particles), in order to ensure the aviation security and the prompt management of the emergencies.</p><p>Here we present different procedures for volcanic ash cloud detection and retrieval using S3 SLSTR (Sentinel-3 Sea and Land Surface Temperature Radiometer) data collected the 22 June at 00:07 UTC by the Sentinel-3A platform during the Raikoke (Kuril Islands) 2019 eruption.</p><p>The volcanic ash detection is realized by applying an innovative machine learning based algorithm, which uses a MultiLayer Perceptron Neural Network (NN) to classify a SLSTR image in eight different surfaces/objects, distinguishing volcanic and weather clouds, and the underlying surfaces. The results obtained with the NN procedure have been compared with two consolidated approaches based on an RGB channels combination in the visible (VIS) spectral range and the Brightness Temperature Difference (BTD) procedure that exploits the thermal infrared (TIR) channels centred at 11 and 12 microns (S8 and S9 SLSTR channels respectively). The ash volcanic cloud is correctly identified by all the models and the results indicate a good agreement between the NN classification approach, the VIS-RGB and BTD procedures.</p><p>The ash retrieval parameters (AOD, Re and Ma) are obtained by applying three different algorithms, all exploiting the volcanic cloud “mask” obtained from the NN detection approach. The first method is the Look Up Table (LUT<sub>p</sub>) procedure, which uses a Radiative Transfer Model (RTM) to simulate the Top Of Atmosphere (TOA) radiances in the SLSTR thermal infrared channels (S8, S9), by varying the aerosol optical depth and the effective radius. The second algorithm is the Volcanic Plume Retrieval (VPR), based on a linearization of the radiative transfer equation capable to retrieve, from multispectral satellite images, the abovementioned parameters. The third approach is a NN model, which is built on a training set composed by the inputs-outputs pairs TOA radiances vs. ash parameters. The results of the three retrieval methods have been compared, considering as reference the LUT<sub>p</sub> procedure, since that it is the most consolidated approach. The comparison shown promising agreement between the different methods, leading to the development of an integrated approach for the monitoring of volcanic ash clouds using SLSTR.</p><p>The results presented in this work have been obtained in the sphere of the VISTA (Volcanic monItoring using SenTinel sensors by an integrated Approach) project, funded by ESA and developed within the EO Science for Society framework [https://eo4society.esa.int/projects/vista/].</p>

Coalition Governance in Western Europe

2021 ◽  
pp. 1-14
Author(s):  
Torbjörn Bergman ◽  
Bäck Hanna ◽  
Hellström Johan
Keyword(s):  
Life Cycle ◽  
Eastern Europe ◽  
Formation Process ◽  
Western Europe ◽  
Party Systems ◽  
Final Phase ◽  
Central Eastern Europe ◽  
Three Stages ◽  
Central Eastern ◽  
Western European

This chapter describes the ambitions of the volume. First, we build on the lessons from earlier studies of governments in Western and Central Eastern Europe to deepen our understanding of the coalition life cycle, covering the three stages of a government’s ‘life’, beginning with the formation process, then turning to the governance stage, and lastly turning to the final phase when governments eventually terminate. Second, we seek to capture how recent changes in the Western European party systems, which are also described here, influence the various stages of the coalition life cycle. Third, we are in particular interested in how coalition partners cooperate and make policy once a government has formed, aiming to contribute to the growing literature on the topic of coalition governance. The chapter ends with a description of the content of the volume.

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