scholarly journals Modeling volcanic ash aggregation processes and related impacts on the April–May 2010 eruptions of Eyjafjallajökull volcano with WRF-Chem

2020 ◽  
Vol 20 (10) ◽  
pp. 2721-2737 ◽  
Author(s):  
Sean D. Egan ◽  
Martin Stuefer ◽  
Peter W. Webley ◽  
Taryn Lopez ◽  
Catherine F. Cahill ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Field Measurements ◽  
Volcanic Eruptions ◽  
Sensitivity Study ◽  
Collision Kernel ◽  
Aggregation Process ◽  
Airborne Measurements ◽  
Aggregation Processes ◽  
Ash Transport

Abstract. Volcanic eruptions eject ash and gases into the atmosphere that can contribute to significant hazards to aviation, public and environment health, and the economy. Several volcanic ash transport and dispersion (VATD) models are in use to simulate volcanic ash transport operationally, but none include a treatment of volcanic ash aggregation processes. Volcanic ash aggregation can greatly reduce the atmospheric budget, dispersion and lifetime of ash particles, and therefore its impacts. To enhance our understanding and modeling capabilities of the ash aggregation process, a volcanic ash aggregation scheme was integrated into the Weather Research Forecasting with online Chemistry (WRF-Chem) model. Aggregation rates and ash mass loss in this modified code are calculated in line with the meteorological conditions, providing a fully coupled treatment of aggregation processes. The updated-model results were compared to field measurements of tephra fallout and in situ airborne measurements of ash particles from the April–May 2010 eruptions of Eyjafjallajökull volcano, Iceland. WRF-Chem, coupled with the newly added aggregation code, modeled ash clouds that agreed spatially and temporally with these in situ and field measurements. A sensitivity study provided insights into the mechanics of the aggregation code by analyzing each aggregation process (collision kernel) independently, as well as by varying the fractal dimension of the newly formed aggregates. In addition, the airborne lifetime (e-folding) of total domain ash mass was analyzed for a range of fractal dimensions, and a maximum reduction of 79.5 % of the airborne ash lifetime was noted.

scholarly journals Modeling volcanic ash aggregation processes and related impacts on the April/May 2010 eruptions of Eyjafjallajökull Volcano with WRF-Chem

2019 ◽  
Author(s):  
Sean D. Egan ◽  
Martin Stuefer ◽  
Peter W. Webley ◽  
Taryn Lopez ◽  
Catherine F. Cahill ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Volcanic Ash ◽  
Field Measurements ◽  
Volcanic Eruptions ◽  
Collision Kernel ◽  
Aggregation Process ◽  
Airborne Measurements ◽  
Aggregation Processes ◽  
Ash Transport

Abstract. Volcanic eruptions eject ash and gases into the atmosphere that can contribute to significant hazards to aviation, public and environment health, and the economy. Several volcanic ash transport and dispersion (VATD) models are in use to simulate volcanic ash transport operationally, but none include a treatment of volcanic ash aggregation processes. Volcanic ash aggregation can greatly reduce the atmospheric budget, dispersion and lifetime of ash particles and therefore its impacts. To enhance our understanding and modeling capabilities of the ash aggregation process, a volcanic ash aggregation scheme was integrated into the Weather Research Forecasting with online Chemistry (WRF-Chem) model. Aggregation rates and ash mass loss in this modified code are calculated in-line with the meteorological conditions, providing a fully coupled treatment of aggregation processes. The updated-model results were compared to field measurements of tephra fallout and in situ airborne measurements of ash particles from the April/May 2010 eruptions of Eyjafjallajökull Volcano, Iceland. WRF-Chem, coupled with the newly added aggregation code, modeled ash clouds that agreed spatially and temporally with these in situ and field measurements. A sensitivity study provided insights into the mechanics of the aggregation code by analyzing each aggregation process (collision kernel) independently, as well as by varying the fractal dimension of the newly formed aggregates. In addition, the airborne lifetime (e-folding) of total domain ash mass was analyzed for a range of fractal dimension, and a maximum reduction of 79.5 % of the airborne ash lifetime was noted.

scholarly journals Aeolian Remobilisation of Volcanic Ash: Outcomes of a Workshop in the Argentinian Patagonia

2020 ◽  
Vol 8 ◽  
Author(s):  
Paul A. Jarvis ◽  
Costanza Bonadonna ◽  
Lucia Dominguez ◽  
Pablo Forte ◽  
Corine Frischknecht ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Friction Velocity ◽  
Critical Infrastructure ◽  
Dust Emission ◽  
Source Area ◽  
Field Measurements ◽  
Volcanic Eruptions ◽  
Field Studies ◽  
Sediment Traps ◽  
Economic Sectors

During explosive volcanic eruptions, large quantities of tephra can be dispersed and deposited over wide areas. Following deposition, subsequent aeolian remobilisation of ash can potentially exacerbate primary impacts on timescales of months to millennia. Recent ash remobilisation events (e.g., following eruptions of Cordón Caulle 2011; Chile, and Eyjafjallajökull 2010, Iceland) have highlighted this to be a recurring phenomenon with consequences for human health, economic sectors, and critical infrastructure. Consequently, scientists from observatories and Volcanic Ash Advisory Centers (VAACs), as well as researchers from fields including volcanology, aeolian processes and soil sciences, convened at the San Carlos de Bariloche headquarters of the Argentinian National Institute of Agricultural Technology to discuss the “state of the art” for field studies of remobilised deposits as well as monitoring, modeling and understanding ash remobilisation. In this article, we identify practices for field characterisation of deposits and active processes, including mapping, particle characterisation and sediment traps. Furthermore, since forecast models currently rely on poorly-constrained dust emission schemes, we call for laboratory and field measurements to better parameterise the flux of volcanic ash as a function of friction velocity. While source area location and extent are currently the primary inputs for dispersion models, once emission schemes become more sophisticated and better constrained, other parameters will also become important (e.g., source material volume and properties, effective precipitation, type and distribution of vegetation cover, friction velocity). Thus, aeolian ash remobilisation hazard and associated impact assessment require systematic monitoring, including the development of a regularly-updated spatial database of resuspension source areas.

The fate of volcanic ash aggregates: premature or delayed sedimentation?

2020 ◽  
Author(s):  
Eduardo Rossi ◽  
Frances Beckett ◽  
Costanza Bonadonna ◽  
Gholamhossein Bagheri
Keyword(s):  
Volcanic Ash ◽  
Dispersion Model ◽  
Volcanic Eruptions ◽  
Fall Velocity ◽  
Field Evidence ◽  
Aggregation Processes ◽  
Lagrangian Dispersion ◽  
Theoretical Evidence

<p>Most volcanic ash produced during explosive volcanic eruptions sediments as aggregates of various types that typically have a greater fall velocity than the particles of which they are composed. As a result, aggregation processes are commonly known to affect the sedimentation of fine ash by considerably reducing its residence time in the atmosphere. Nonetheless, speculations also exist in the literature that aggregation does not always result in a premature sedimentation of their constitute particles but that it can also result in a delayed sedimentation (i.e. the so-called rafting effect). However, previous studies have considered rafting as a highly improbable phenomenon due to a biased representation of aggregate shapes.</p><p>Here we provide the first theoretical evidence that rafting may not only occur, but it is probably more common than previously thought, helping to elucidate often unexplained field observations. Starting from field evidence of rafted aggregates at Sakurajima Volcano (Japan), we clarify the conditions for which aggregation of volcanic ash results either in a premature or a delayed sedimentation.</p><p>Moreover, using the Lagrangian dispersion model NAME, we show the practical consequences of rafting on the final sedimentation distance of aggregates with different morphological features. As an application we chose the case study of the 2010 eruption of Eyjafjallajökull volcano (Iceland), for which rafting can increase the travel distances of ash <500 m up 3.7 times with respect to sedimentation of individual particles.</p><p>These findings have fundamental implications both for real-time forecasting and long-term hazard assessment of volcanic ash dispersal and sedimentation and for weather modelling. The constraints on rafting presented and discussed in this work will help the scientific community to clarify the often unexpected role of aggregation in creating a delayed sedimentation of coarse ash.</p>

scholarly journals Evaluation of MODIS Albedo Product over Ice Caps in Iceland and Impact of Volcanic Eruptions on Their Albedo

2017 ◽  
Author(s):  
Simon Gascoin ◽  
Sverrir Guðmundsson ◽  
Guðfinna Aðalgeirsdóttir ◽  
Finnur Pálsson ◽  
Louise Schmidt ◽  
...  
Keyword(s):  
Correlation Coefficients ◽  
Field Measurements ◽  
Volcanic Eruptions ◽  
Ground Truth ◽  
Climate Forcing ◽  
Balance Model ◽  
Ice Caps ◽  
Good Ability ◽  
Mean Square Errors

Albedo is a key variable in the response of glaciers to climate. In Iceland, large albedo variations in the ice caps may be caused by the deposition of volcanic ash (tephra). Sparse in situ field measurements are insufficient to characterize the spatial variation of albedo over the ice caps. Here we evaluate the latest MCD43 MODIS albedo product (collection 6) to monitor albedo over the Icelandic ice caps using albedo from ten automatic weather stations in Vatnajökull and Langjökull as ground truth. We examine the influence of the albedo variability within MODIS pixels by comparing the results with a collection of Landsat scenes. The results indicate a good ability of the MODIS product to characterize the seasonal and interannual albedo changes with correlation coefficients ranging from 0.47 to 0.90 (median 0.84) and a small bias ranging from -0.07 to 0.09. The root-mean square errors (RMSE) ranging from 0.08 and 0.21, is larger than that from previous studies, but we did not discard the retrievals flagged as bad quality to maximize the amount of observations given the frequent cloud obstruction in Iceland. We find a positive but non-significant relationship between the RMSE and the subpixel variability as indicated by the standard deviation of the Landsat albedo within the MODIS pixel (R=0.48). The summer albedo maps and time series computed from the MODIS product show that the albedo decreased significantly after the Eyjafjallajökull and Grímsvötn eruptions in 2010 and 2011 in all the main ice caps (except the northernmost Drangajökull), with albedo reduction up to 0.6 over large regions of the accumulation areas. Following this validation, these data will be assimilated in an energy and mass balance model of to better understand the relative influence of the volcanic and climate forcing to the ongoing mass losses of Icelandic ice caps.

scholarly journals Retrievals of Aerosol Optical and Microphysical Properties from Imaging Polar Nephelometer Scattering Measurements

2016 ◽  
Author(s):  
W. Reed Espinosa ◽  
Lorraine Remer ◽  
Oleg Dubovik ◽  
Luke Ziemba ◽  
Andreas Beyersdorf ◽  
...  
Keyword(s):  
Refractive Index ◽  
Measurement Techniques ◽  
Field Measurements ◽  
Atmospheric Composition ◽  
Particle Size Distributions ◽  
Airborne Measurements ◽  
Microphysical Properties ◽  
Scattering Measurements ◽  
Visible Wavelengths

Abstract. A method for the retrieval of optical and microphysical properties from in situ light scattering measurements is presented and the results are compared with existing measurement techniques. The Generalized Retrieval of Aerosol and Surface Properties (GRASP) is applied to airborne and laboratory measurements made by a novel polar nephelometer. This instrument, the Polarized Imaging Nephelometer (PI-Neph), is capable of making high accuracy field measurements of phase function and degree of linear polarization, at three visible wavelengths, over a wide angular range of 3° to 177°. The resulting retrieval produces particle size distributions (PSD) that agree, to within experimental error, with measurements made by commercial optical particle counters (OPCs). Additionally, the retrieved real part of the refractive index is generally found to be within the predicted error of 0.02 from the expected values for three species of humidified salts particles, whose refractive index is well established. The airborne measurements used in this work were made aboard the NASA DC-8 aircraft during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field campaign, and the inversion of this data represent the first aerosol retrievals of airborne polar nephelometer data. The results provide confidence in the refractive index product, as well as in the retrieval's ability to accurately determine PSD, without assumptions about refractive index that are required by the majority of OPCs.

scholarly journals Model-based aviation advice on distal volcanic ash clouds by assimilating aircraft in situ measurements

2016 ◽  
Vol 16 (14) ◽  
pp. 9189-9200 ◽  
Author(s):  
Guangliang Fu ◽  
Arnold Heemink ◽  
Sha Lu ◽  
Arjo Segers ◽  
Konradin Weber ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Transport Model ◽  
Real Life ◽  
Forecast Accuracy ◽  
In Situ Measurements ◽  
Northwestern Part ◽  
Ash Plume ◽  
Potential Improvement ◽  
Ash Transport

Abstract. The forecast accuracy of distal volcanic ash clouds is important for providing valid aviation advice during volcanic ash eruption. However, because the distal part of volcanic ash plume is far from the volcano, the influence of eruption information on this part becomes rather indirect and uncertain, resulting in inaccurate volcanic ash forecasts in these distal areas. In our approach, we use real-life aircraft in situ observations, measured in the northwestern part of Germany during the 2010 Eyjafjallajökull eruption, in an ensemble-based data assimilation system combined with a volcanic ash transport model to investigate the potential improvement on the forecast accuracy with regard to the distal volcanic ash plume. We show that the error of the analyzed volcanic ash state can be significantly reduced through assimilating real-life in situ measurements. After a continuous assimilation, it is shown that the aviation advice for Germany, the Netherlands and Luxembourg can be significantly improved. We suggest that with suitable aircrafts measuring once per day across the distal volcanic ash plume, the description and prediction of volcanic ash clouds in these areas can be greatly improved.

scholarly journals Retrievals of aerosol optical and microphysical properties from Imaging Polar Nephelometer scattering measurements

2017 ◽  
Vol 10 (3) ◽  
pp. 811-824 ◽  
Author(s):  
W. Reed Espinosa ◽  
Lorraine A. Remer ◽  
Oleg Dubovik ◽  
Luke Ziemba ◽  
Andreas Beyersdorf ◽  
...  
Keyword(s):  
Refractive Index ◽  
Measurement Techniques ◽  
Field Measurements ◽  
Atmospheric Composition ◽  
Particle Size Distributions ◽  
Airborne Measurements ◽  
Microphysical Properties ◽  
Scattering Measurements ◽  
Visible Wavelengths

Abstract. A method for the retrieval of aerosol optical and microphysical properties from in situ light-scattering measurements is presented and the results are compared with existing measurement techniques. The Generalized Retrieval of Aerosol and Surface Properties (GRASP) is applied to airborne and laboratory measurements made by a novel polar nephelometer. This instrument, the Polarized Imaging Nephelometer (PI-Neph), is capable of making high-accuracy field measurements of phase function and degree of linear polarization, at three visible wavelengths, over a wide angular range of 3 to 177°. The resulting retrieval produces particle size distributions (PSDs) that agree, within experimental error, with measurements made by commercial optical particle counters (OPCs). Additionally, the retrieved real part of the refractive index is generally found to be within the predicted error of 0.02 from the expected values for three species of humidified salt particles, with a refractive index that is well established. The airborne measurements used in this work were made aboard the NASA DC-8 aircraft during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field campaign, and the inversion of this data represents the first aerosol retrievals of airborne polar nephelometer data. The results provide confidence in the real refractive index product, as well as in the retrieval's ability to accurately determine PSD, without assumptions about refractive index that are required by the majority of OPCs.

scholarly journals Development of PUFF–Gaussian dispersion model for the prediction of atmospheric distribution of particle concentration

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jooyong Lee ◽  
Sungsu Lee ◽  
HyunA Son ◽  
Waon-ho Yi
Keyword(s):  
Numerical Analysis ◽  
Volcanic Ash ◽  
Dispersion Model ◽  
Gaussian Model ◽  
Field Measurements ◽  
Volcanic Eruptions ◽  
Lagrangian Model ◽  
Analysis Model ◽  
Ash Dispersion ◽  
Gaussian Dispersion

AbstractMt. Baekdu’s eruption precursors are continuously observed and have become a global social issue. Volcanic activities in neighboring Japan are also active. There are no direct risks of proximity-related disasters in South Korea from the volcanic eruptions at Japan or Mt. Baekdu; however, severe impacts are expected from the spread of volcanic ash. Numerical analysis models are generally used to predict and analyze the diffusion of volcanic ash, and each numerical analysis model has its own limitations caused by the computational algorithm it employs. In this study, we analyzed the PUFF–UAF model, an ash dispersion model based on the Lagrangian approach, and observed that the number of particles used in tracking substantially affected the results. Even with the presence of millions of particles, the concentration of ash predicted by the PUFF–UAF model does not accurately represent the dispersion. To overcome this deficit and utilize the computational efficiency of the Lagrangian model, we developed a PUFF–Gaussian model to consider the dispersive nature of ash by applying the Gaussian dispersion theory to the results of the PUFF–UAF model. The results of the proposed method were compared with the field measurements from actual volcanic eruptions, and the comparison showed that the proposed method can produce reasonably accurate predictions for ash dispersion.

scholarly journals Aircraft validation of Aura Tropospheric Emission Spectrometer retrievals of HDO and H<sub>2</sub>O

2014 ◽  
Vol 7 (4) ◽  
pp. 3801-3833 ◽  
Author(s):  
R. L. Herman ◽  
J. E. Cherry ◽  
J. Young ◽  
J. M. Welker ◽  
D. Noone ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Standard Deviation ◽  
Lower Troposphere ◽  
Field Measurements ◽  
Temporal Variations ◽  
Observation Error ◽  
Free Troposphere ◽  
Airborne Measurements

Abstract. The EOS Aura Tropospheric Emission Spectrometer (TES) retrieves the atmospheric HDO/H2O ratio in the mid-to-lower troposphere as well as the planetary boundary layer. TES observations of water vapor and the HDO isotopologue have been compared with nearly coincident in situ airborne measurements for direct validation of the TES products. The field measurements were made with a commercially available Picarro L1115-i isotopic water analyzer on aircraft over the Alaskan interior boreal forest during the three summers of 2011 to 2013. TES special observations were utilized in these comparisons. The TES averaging kernels and a priori constraints have been applied to the in situ data, using Version Five (V005) of the TES data. TES calculated errors are compared with the standard deviation (1-σ) of scan-to-scan variability to check consistency with the TES observation error. Spatial and temporal variations are assessed from the in situ aircraft measurements. It is found that the standard deviation of scan-to-scan variability of TES δD is ±34.1‰ in the boundary layer, and ±26.5‰ in the free troposphere. This scan-to-scan variability is consistent with the TES estimated error (observation error) of 10–18‰ after accounting for the atmospheric variations along the TES track of ±16‰ in the boundary layer, increasing to ±30‰ in the free troposphere observed by the aircraft in situ measurements. We estimate that TES V005 δD is biased high by an amount that decreases with pressure: approximately +12.3% at 1000 hPa, +9.8% in the boundary layer, and +3.7% in the free troposphere. The uncertainty in this bias estimate is ±2%. After bias correction, we show that TES has accurate sensitivity to water vapor isotopologues in the boundary layer.

scholarly journals Impacts of Volcanic Eruptions around the Korean Peninsula: A Long-term Simulation Study for Hypothetical Eruption Scenarios

2020 ◽  
Vol 20 (5) ◽  
pp. 361-371
Author(s):  
Kihyun Park ◽  
Byung-Il Min ◽  
Sora Kim ◽  
Jiyoon Kim ◽  
Kyung-Suk Suh
Keyword(s):  
Korean Peninsula ◽  
Volcanic Ash ◽  
Dispersion Model ◽  
Three Dimensional ◽  
Volcanic Eruptions ◽  
Summer Season ◽  
Assessment System ◽  
Dose Assessment ◽  
Ash Transport

To build a response against potential volcanic risks around Korea, we developed a three-dimensional Volcanic Ash Transport and Dispersion Model (VATDM), known as the Lagrangian Atmospheric Dose Assessment System-Volcanic Ash (LADAS-VA) model. Using the LADAS-VA model, we performed numerous simulations for multiple year-round hypothetical eruptions of several representative volcanoes around the Korean peninsula. We analyzed the simulation results and revealed the impacts of hypothetical volcanic eruptions on the Korean peninsula as counting the number of days influenced by the season. Overall simulations for hypothetical volcanic eruptions around the Korean peninsula revealed that the most impactful eruptions would potentially occur during the summer season. Long-term simulations examining hypothetical eruption scenarios at least over a decade must be conducted to enable the analysis of deviations on a year-on-year basis, in comparison with the climatological normals.

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