Validation of ash cloud modelling with satellite retrievals: a case study of the 16–17 June 1996 Mount Ruapehu eruption

2015 ◽  
Vol 78 (2) ◽  
pp. 973-993 ◽  
Author(s):  
J. Liu ◽  
J. A. Salmond ◽  
K. N. Dirks ◽  
J. M. Lindsay
Keyword(s):  
Satellite Retrievals ◽  
Mount Ruapehu ◽  
Cloud Modelling ◽  
Ash Cloud

scholarly journals Identifying local anthropogenic CO2 emissions with satellite retrievals: a case study in South Korea

2018 ◽  
Vol 40 (3) ◽  
pp. 1011-1029 ◽  
Author(s):  
Changsub Shim ◽  
Jihyun Han ◽  
Daven K. Henze ◽  
Taeyeon Yoon
Keyword(s):  
South Korea ◽  
Co2 Emissions ◽  
Anthropogenic Co2 ◽  
Satellite Retrievals

scholarly journals FALL3D-8.0: a computational model for atmospheric transport and deposition of particles, aerosols and radionuclides – Part 2: Model validation

2021 ◽  
Vol 14 (1) ◽  
pp. 409-436
Author(s):  
Andrew T. Prata ◽  
Leonardo Mingari ◽  
Arnau Folch ◽  
Giovanni Macedonio ◽  
Antonio Costa
Keyword(s):  
Case Studies ◽  
Model Validation ◽  
Volcanic Ash ◽  
Atmospheric Transport ◽  
Test Suite ◽  
Structure Amplitude ◽  
Satellite Retrievals ◽  
Mt Etna ◽  
Ash Cloud ◽  
Tephra Fallout

Abstract. This paper presents model validation results for the latest version release of the FALL3D atmospheric transport model. The code has been redesigned from scratch to incorporate different categories of species and to overcome legacy issues that precluded its preparation towards extreme-scale computing. The model validation is based on the new FALL3D-8.0 test suite, which comprises a set of four real case studies that encapsulate the major features of the model; namely, the simulation of long-range fine volcanic ash dispersal, volcanic SO2 dispersal, tephra fallout deposits and the dispersal and deposition of radionuclides. The first two test suite cases (i.e. the June 2011 Puyehue-Cordón Caulle ash cloud and the June 2019 Raikoke SO2 cloud) are validated against geostationary satellite retrievals and demonstrate the new FALL3D data insertion scheme. The metrics used to validate the volcanic ash and SO2 simulations are the structure, amplitude and location (SAL) metric and the figure of merit in space (FMS). The other two test suite cases (i.e. the February 2013 Mt. Etna ash cloud and associated tephra fallout deposit, and the dispersal of radionuclides resulting from the 1986 Chernobyl nuclear accident) are validated with scattered ground-based observations of deposit load and local particle grain size distributions and with measurements from the Radioactivity Environmental Monitoring database. For validation of tephra deposit loads and radionuclides, we use two variants of the normalised root-mean-square error metric. We find that FALL3D-8.0 simulations initialised with data insertion consistently improve agreement with satellite retrievals at all lead times up to 48 h for both volcanic ash and SO2 simulations. In general, SAL scores lower than 1.5 and FMS scores greater than 0.40 indicate acceptable agreement with satellite retrievals of volcanic ash and SO2. In addition, we show very good agreement, across several orders of magnitude, between the model and observations for the 2013 Mt. Etna and 1986 Chernobyl case studies. Our results, along with the validation datasets provided in the publicly available test suite, form the basis for future improvements to FALL3D (version 8 or later) and also allow for model intercomparison studies.

scholarly journals Improving volcanic ash predictions with the HYSPLIT dispersion model by assimilating MODIS satellite retrievals

2016 ◽  
Author(s):  
Tianfeng Chai ◽  
Alice Crawford ◽  
Barbara Stunder ◽  
Michael Pavolonis ◽  
Roland Draxler ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Dispersion Model ◽  
Temporal Variations ◽  
Current Case ◽  
Cost Functional ◽  
Free Region ◽  
Model Predictions ◽  
Satellite Retrievals ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Ash Cloud

Abstract. Currently NOAA's National Weather Service (NWS) runs the HYSPLIT dispersion model with a unit mass release rate to predict the transport and dispersion of volcanic ash. The model predictions provide information for the Volcanic Ash Advisory Centers (VAAC) to issue advisories to meteorological watch offices, area control centers, flight information centers, and others. This research aims provide quantitative forecasts of ash distributions generated by objectively and optimally estimating the volcanic ash source strengths, vertical distribution and temporal variations using an observation-modeling inversion technique. In this top-down approach, a cost functional is defined to mainly quantify the differences between model predictions and the satellite measurements of column integrated ash concentrations, weighted by the model and observation uncertainties. Minimizing this cost functional by adjusting the sources provides the volcanic ash emission estimates. As an example, MODIS (MOderate Resolution Imaging Spectroradiometer) satellite retrievals of the 2008 Kasatochi volcanic ash clouds are used to test the HYSPLIT volcanic ash inverse system. Because the satellite retrievals include the ash cloud top height but not the bottom height, three options for matching the model concentrations to the observed mass loadings are tested. Although the emission estimates vary significantly with different options the subsequent model predictions with the different release estimates all show decent skill when evaluated against the unassimilated satellite observations at later times. Among the three options, integrating over three model layers yields slightly better results than integrating from the surface up to the volcanic ash cloud top or using a single model layer. Inverse tests also show that including the ash-free region to constrain the model is not beneficial for the current case. In addition, extra constraints to the source terms can be given by explicitly enforcing ``no-ash'' for the atmosphere columns above or below the observed ash cloud top height. However, in this case such extra constraints are not helpful for the inverse modeling. It is also found that simultaneously assimilating observations at different times produces better hindcasts than only assimilating the most recent observations.

scholarly journals Improving volcanic ash predictions with the HYSPLIT dispersion model by assimilating MODIS satellite retrievals

2017 ◽  
Vol 17 (4) ◽  
pp. 2865-2879 ◽  
Author(s):  
Tianfeng Chai ◽  
Alice Crawford ◽  
Barbara Stunder ◽  
Michael J. Pavolonis ◽  
Roland Draxler ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Dispersion Model ◽  
Temporal Variations ◽  
Current Case ◽  
Cost Functional ◽  
Free Region ◽  
Model Predictions ◽  
Satellite Retrievals ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Ash Cloud

Abstract. Currently, the National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) runs the HYSPLIT dispersion model with a unit mass release rate to predict the transport and dispersion of volcanic ash. The model predictions provide information for the Volcanic Ash Advisory Centers (VAAC) to issue advisories to meteorological watch offices, area control centers, flight information centers, and others. This research aims to provide quantitative forecasts of ash distributions generated by objectively and optimally estimating the volcanic ash source strengths, vertical distribution, and temporal variations using an observation-modeling inversion technique. In this top-down approach, a cost functional is defined to quantify the differences between the model predictions and the satellite measurements of column-integrated ash concentrations weighted by the model and observation uncertainties. Minimizing this cost functional by adjusting the sources provides the volcanic ash emission estimates. As an example, MODIS (Moderate Resolution Imaging Spectroradiometer) satellite retrievals of the 2008 Kasatochi volcanic ash clouds are used to test the HYSPLIT volcanic ash inverse system. Because the satellite retrievals include the ash cloud top height but not the bottom height, there are different model diagnostic choices for comparing the model results with the observed mass loadings. Three options are presented and tested. Although the emission estimates vary significantly with different options, the subsequent model predictions with the different release estimates all show decent skill when evaluated against the unassimilated satellite observations at later times. Among the three options, integrating over three model layers yields slightly better results than integrating from the surface up to the observed volcanic ash cloud top or using a single model layer. Inverse tests also show that including the ash-free region to constrain the model is not beneficial for the current case. In addition, extra constraints on the source terms can be given by explicitly enforcing no-ash for the atmosphere columns above or below the observed ash cloud top height. However, in this case such extra constraints are not helpful for the inverse modeling. It is also found that simultaneously assimilating observations at different times produces better hindcasts than only assimilating the most recent observations.

scholarly journals Operational Response to Volcanic Ash Risks Using HOTVOLC Satellite-Based System and MOCAGE-Accident Model at the Toulouse VAAC

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 864
Author(s):  
Mathieu Gouhier ◽  
Mathieu Deslandes ◽  
Yannick Guéhenneux ◽  
Philippe Hereil ◽  
Philippe Cacault ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Source Parameters ◽  
Vertical Column ◽  
Cloud Properties ◽  
Eruptive Column ◽  
Operational Management ◽  
Remote Sensing Techniques ◽  
Ash Cloud

In 2010, the Eyjafjallajökull volcano erupted, generating an ash cloud causing unprecedented disruption of European airspace. Despite an exceptional situation, both the London and Toulouse Volcanic Ash Advisory Centres (VAAC) provided critical information on the location of the cloud and on the concentration of ash, thus contributing to the crisis management. Since then, substantial efforts have been carried out by the scientific community in order to improve remote sensing techniques and numerical modeling. Satellite instruments have proven to be particularly relevant for the characterization of ash cloud properties and a great help in the operational management of volcanic risk. In this study, we present the satellite-based system HOTVOLC developed at the Observatoire de Physique du Globe de Clermont-Ferrand (OPGC) using Meteosat geostationary satellite and designed for real-time monitoring of active volcanoes. After a brief presentation of the system we provide details on newly developed satellite products dedicated to the ash cloud characterization. This includes, in particular, ash cloud altitude and vertical column densities (VCD). Then, from the Stromboli 2018 paroxysm, we show how HOTVOLC can be used in a timely manner to assist the Toulouse VAAC in the operational management of the eruptive crisis. In the second part of the study, we provide parametric tests of the MOCAGE-Accident model run by the Toulouse VAAC from the April 17 Eyjafjallajökull eruption. For this purpose, we tested a range of eruption source parameters including the Total Grain Size Distribution (TGSD), the eruptive column profile, the top plume height and mass eruption rate (MER), as well as the fine ash partitioning. Finally, we make a comparison on this case study between HOTVOLC and MOCAGE-Accident VCD.

scholarly journals Visualizing Volcanic Ash Forecasts: Scientist and Stakeholder Decisions Using Different Graphical Representations and Conflicting Forecasts

2017 ◽  
Vol 9 (3) ◽  
pp. 333-348 ◽  
Author(s):  
Kelsey J. Mulder ◽  
Matthew Lickiss ◽  
Natalie Harvey ◽  
Alison Black ◽  
Andrew Charlton-Perez ◽  
...  
Keyword(s):  
High Risk ◽  
Volcanic Ash ◽  
Volcanic Eruptions ◽  
Graphical Representations ◽  
Risk Averse ◽  
Airline Operations ◽  
Risk Seeking ◽  
Satellite Retrievals ◽  
Flight Cancellations ◽  
Ash Cloud

Abstract During volcanic eruptions, Volcanic Ash Advisory Centres issue ash advisories for aviation showing the forecasted outermost extent of the ash cloud. During the 2010 Icelandic volcano Eyjafjallajökull eruption, the Met Office produced supplementary forecasts of quantitative ash concentration, due to demand from airlines. Additionally, satellite retrievals of estimated volcanic ash concentration are now available. To test how these additional graphical representations of volcanic ash affect flight decisions, whether users infer uncertainty in graphical forecasts of volcanic ash, and how decisions are made when given conflicting forecasts, a survey was conducted of 25 delegates representing U.K. research and airline operations dealing with volcanic ash. Respondents were more risk seeking with safer flight paths and risk averse with riskier flight paths when given location and concentration forecasts compared to when given only the outermost extent of the ash. Respondents representing operations were more risk seeking than respondents representing research. Additionally, most respondents’ hand-drawn no-fly zones were larger than the areas of unsafe ash concentrations in the forecasts. This conservatism implies that respondents inferred uncertainty from the volcanic ash concentration forecasts. When given conflicting forecasts, respondents became more conservative than when given a single forecast. The respondents were also more risk seeking with high-risk flight paths and more risk averse with low-risk flight paths when given conflicting forecasts than when given a single forecast. The results show that concentration forecasts seem to reduce flight cancellations while maintaining safety. Open discussions with the respondents suggested that definitions of uncertainty may differ between research and operations.

The Genesis and Internal Dynamics of El Salvador's People's Revolutionary Army, 1970–1976

2014 ◽  
Vol 38 (01) ◽  
pp. 102-129
Author(s):  
ALBERTO MARTÍN ÁLVAREZ ◽  
EUDALD CORTINA ORERO
Keyword(s):  
Latin America ◽  
El Salvador ◽  
Early Years ◽  
Left Wing ◽  
Internal Dynamics ◽  
Internal Coherence ◽  
The 1960S

AbstractUsing interviews with former militants and previously unpublished documents, this article traces the genesis and internal dynamics of the Ejército Revolucionario del Pueblo (People's Revolutionary Army, ERP) in El Salvador during the early years of its existence (1970–6). This period was marked by the inability of the ERP to maintain internal coherence or any consensus on revolutionary strategy, which led to a series of splits and internal fights over control of the organisation. The evidence marshalled in this case study sheds new light on the origins of the armed Salvadorean Left and thus contributes to a wider understanding of the processes of formation and internal dynamics of armed left-wing groups that emerged from the 1960s onwards in Latin America.

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