scholarly journals Airborne Volcanic Ash Forecast Area Reliability

2007 ◽  
Vol 22 (5) ◽  
pp. 1132-1139 ◽  
Author(s):  
Barbara J. B. Stunder ◽  
Jerome L. Heffter ◽  
Roland R. Draxler
Keyword(s):  
Volcanic Ash ◽  
Dispersion Model ◽  
Analysis Data ◽  
Flight Safety ◽  
Commercial Aircraft ◽  
Hysplit Model ◽  
Aircraft Flight ◽  
Two Parameters ◽  
Degree Of Overlap ◽  
Ash Transport

Abstract In support of aircraft flight safety operations, daily comparisons between modeled, hypothetical, volcanic ash plumes calculated with meteorological forecasts and analyses were made over a 1.5-yr period. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model simulated the ash transport and dispersion. Ash forecasts and analyses from seven volcanoes were studied. The volcanoes were chosen because of recent eruptions or because their airborne ash could impinge on well-traveled commercial aircraft flight paths. For each forecast–analysis pair, a statistic representing the degree of overlap, the threat score (TS), was calculated. A forecast was classified as acceptable if the TS was greater than 0.25. Each forecast was also categorized by two parameters: the forecast area quadrant with respect to the volcano and a factor related to the complexity of the meteorology. The forecast complexity factor was based on the degree of spread using NCEP ensemble output or using a HYSPLIT offset configuration. In general, the larger the spread of the ensemble or offset forecasts, the greater the complexity. The forecasts were sorted by complexity factor, and then classified by the quartile of the complexity. The volcanic ash forecast area reliability (VAFAR) was calculated for each forecast area quadrant and for each quartile of the complexity factor. VAFAR is the ratio of the number of acceptable forecasts to the total number of forecasts. Most VAFAR values were above 70%. VAFAR values for two of the seven volcanoes (Popocatepetl in Mexico and Tungurahua in Ecuador) tended to be lower than the others. In general, VAFAR decreased with increasing complexity of the meteorology. It should be noted that the VAFAR values reflect the reliability of the meteorological forecasts when compared to the same calculation using analysis data; the dispersion model itself was not evaluated.

scholarly journals Operational Modelling of Umbrella Cloud Growth in a Lagrangian Volcanic Ash Transport and Dispersion Model

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 200 ◽  
Author(s):  
Helen N. Webster ◽  
Benjamin J. Devenish ◽  
Larry G. Mastin ◽  
David J. Thomson ◽  
Alexa R. Van Eaton
Keyword(s):  
Flow Rate ◽  
Volcanic Ash ◽  
Dispersion Model ◽  
Volume Flow Rate ◽  
Gravity Current ◽  
Volume Flow ◽  
Lateral Spread ◽  
Lagrangian Model ◽  
Model Predictions ◽  
Ash Transport

Large explosive eruptions can result in the formation of an umbrella cloud which rapidly expands, spreading ash out radially from the volcano. The lateral spread by the intrusive gravity current dominates the transport of the ash cloud. Hence, to accurately forecast the transport of ash from large eruptions, lateral spread of umbrella clouds needs to be represented within volcanic ash transport and dispersion models. Here, we describe an umbrella cloud parameterisation which has been implemented into an operational Lagrangian model and consider how it may be used during an eruption when information concerning the eruption is limited and model runtime is key. We examine different relations for the volume flow rate into the umbrella, and the rate of spreading within the cloud. The scheme is validated against historic eruptions of differing scales (Pinatubo 1991, Kelud 2014, Calbuco 2015 and Eyjafjallajökull 2010) by comparing model predictions with satellite observations. Reasonable predictions of umbrella cloud spread are achieved using an estimated volume flow rate from the empirical equation by Bursik et al. and the observed eruption height. We show how model predictions can be refined during an ongoing eruption as further information and observations become available.

scholarly journals Improvements on Near Real Time Detection of Volcanic Ash Emissions for Emergency Monitoring with Limited Satellite Bands

2015 ◽  
Vol 57 ◽  
Author(s):  
Torge Steensen ◽  
Peter Webley ◽  
Jon Dehn
Keyword(s):  
Real Time ◽  
Satellite Data ◽  
Volcanic Ash ◽  
Dispersion Model ◽  
Volcano Monitoring ◽  
Quantitative Comparison ◽  
Title Page ◽  
Model Data ◽  
Dispersion Models ◽  
Ash Transport

<div class="page" title="Page 1"><div class="layoutArea"><div class="column"><p><span>Quantifying volcanic ash emissions syneruptively is an important task for the global aviation community. However, due to the near real time nature of volcano monitoring, many parameters important for accurate ash mass estimates cannot be obtained easily. Even when using the best possible estimates of those parameters, uncertainties associated with the ash masses remain high, especially if the satellite data is only available in the traditional 10.8 and 12.0 μm bands. To counteract this limitation, we developed a quantitative comparison between the ash extents in satellite and model data. The focus is the manual cloud edge definition based on the available satellite reverse absorption (RA) data as well as other knowledge like pilot reports or ground-based observations followed by an application of the Volcanic Ash Retrieval on the defined subset with an RA threshold of 0 K. This manual aspect, although subjective to the experience of the observer, can show a significant improvement as it provides the ability to highlight ash that otherwise would be obscured by meteorological clouds or, by passing over different surfaces with unaccounted temperatures, might be lost entirely and thus remains undetectable for an automated satellite approach. We show comparisons to Volcanic Ash Transport and Dispersion models and outline a quantitative match as well as percentages of overestimates based on satellite or dispersion model data which can be converted into a level of reliability for near real time volcano monitoring. </span></p></div></div></div>

scholarly journals Multi-level emulation of a volcanic ash transport and dispersion model to quantify sensitivity to uncertain parameters

2016 ◽  
Author(s):  
Natalie J. Harvey ◽  
Nathan Huntley ◽  
Helen Dacre ◽  
Michael Goldstein ◽  
David Thomson ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Dispersion Model ◽  
Model Development ◽  
Atmospheric Dispersion ◽  
Theoretical Research ◽  
Model Parameters ◽  
Formal Framework ◽  
Geographical Regions ◽  
Multi Level ◽  
Ash Transport

Abstract. Following the disruption to European airspace caused by the eruption of Eyjafjallajokull in 2010 there has been a move towards producing quantitative predictions of volcanic ash concentration using volcanic ash transport and dispersion simulators. However, there is no formal framework for determining the uncertainties on these predictions and performing many simulations using these complex models is computationally expensive. In this paper a Bayes linear emulation approach is applied to the Numerical Atmospheric-dispersion Modelling Environment (NAME) to better understand the influence of source and internal model parameters on the simulator output. Emulation is a statistical method for predicting the output of a computer simulator at new parameter choices without actually running the simulator. A multi-level emulation approach is applied to combine information from many evaluations of a computationally fast version of NAME with relatively few evaluations of a slower, more accurate, version. This approach is effective when it is not possible to run the accurate simulator many times and when there is also little prior knowledge about the influence of parameters. The approach is applied to the mean ash column loading in 75 geographical regions on 14 May 2010. Through this analysis it has been found that the parameters that contribute the most to the output uncertainty are initial plume rise height, mass eruption rate, free tropospheric turbulence levels and precipitation threshold for wet deposition. This information can be used to inform future model development and observational campaigns and routine monitoring. The analysis presented here suggests the need for further observational and theoretical research into parameterisation of atmospheric turbulence. Furthermore it can also be used to inform the most important parameter perturbations for a small operational ensemble of simulations. The use of an emulator also identifies the input and internal parameters that do not contribute significantly to simulator uncertainty. Finally, the analysis highlights that the fast, less accurate, version of NAME can provide useful information without needing the accurate version at all. This approach can easily be extended to other case studies, simulators or hazards.

scholarly journals Multi-level emulation of a volcanic ash transport and dispersion model to quantify sensitivity to uncertain parameters

2018 ◽  
Vol 18 (1) ◽  
pp. 41-63 ◽  
Author(s):  
Natalie J. Harvey ◽  
Nathan Huntley ◽  
Helen F. Dacre ◽  
Michael Goldstein ◽  
David Thomson ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Dispersion Model ◽  
Model Development ◽  
Atmospheric Dispersion ◽  
Theoretical Research ◽  
Model Parameters ◽  
Formal Framework ◽  
Geographical Regions ◽  
Multi Level ◽  
Ash Transport

Abstract. Following the disruption to European airspace caused by the eruption of Eyjafjallajökull in 2010 there has been a move towards producing quantitative predictions of volcanic ash concentration using volcanic ash transport and dispersion simulators. However, there is no formal framework for determining the uncertainties of these predictions and performing many simulations using these complex models is computationally expensive. In this paper a Bayesian linear emulation approach is applied to the Numerical Atmospheric-dispersion Modelling Environment (NAME) to better understand the influence of source and internal model parameters on the simulator output. Emulation is a statistical method for predicting the output of a computer simulator at new parameter choices without actually running the simulator. A multi-level emulation approach is applied using two configurations of NAME with different numbers of model particles. Information from many evaluations of the computationally faster configuration is combined with results from relatively few evaluations of the slower, more accurate, configuration. This approach is effective when it is not possible to run the accurate simulator many times and when there is also little prior knowledge about the influence of parameters. The approach is applied to the mean ash column loading in 75 geographical regions on 14 May 2010. Through this analysis it has been found that the parameters that contribute the most to the output uncertainty are initial plume rise height, mass eruption rate, free tropospheric turbulence levels and precipitation threshold for wet deposition. This information can be used to inform future model development and observational campaigns and routine monitoring. The analysis presented here suggests the need for further observational and theoretical research into parameterisation of atmospheric turbulence. Furthermore it can also be used to inform the most important parameter perturbations for a small operational ensemble of simulations. The use of an emulator also identifies the input and internal parameters that do not contribute significantly to simulator uncertainty. Finally, the analysis highlights that the faster, less accurate, configuration of NAME can, on its own, provide useful information for the problem of predicting average column load over large areas.

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.

scholarly journals Determination of time- and height-resolved volcanic ash emissions and their use for quantitative ash dispersion modeling: the 2010 Eyjafjallajökull eruption

2011 ◽  
Vol 11 (9) ◽  
pp. 4333-4351 ◽  
Author(s):  
A. Stohl ◽  
A. J. Prata ◽  
S. Eckhardt ◽  
L. Clarisse ◽  
A. Durant ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Dispersion Model ◽  
A Priori ◽  
Volcanic Eruptions ◽  
General Nature ◽  
Aviation Industry ◽  
Dispersion Modeling ◽  
Source Information ◽  
European Area ◽  
Ash Dispersion

Abstract. The April–May, 2010 volcanic eruptions of Eyjafjallajökull, Iceland caused significant economic and social disruption in Europe whilst state of the art measurements and ash dispersion forecasts were heavily criticized by the aviation industry. Here we demonstrate for the first time that large improvements can be made in quantitative predictions of the fate of volcanic ash emissions, by using an inversion scheme that couples a priori source information and the output of a Lagrangian dispersion model with satellite data to estimate the volcanic ash source strength as a function of altitude and time. From the inversion, we obtain a total fine ash emission of the eruption of 8.3 ± 4.2 Tg for particles in the size range of 2.8–28 μm diameter. We evaluate the results of our model results with a posteriori ash emissions using independent ground-based, airborne and space-borne measurements both in case studies and statistically. Subsequently, we estimate the area over Europe affected by volcanic ash above certain concentration thresholds relevant for the aviation industry. We find that during three episodes in April and May, volcanic ash concentrations at some altitude in the atmosphere exceeded the limits for the "Normal" flying zone in up to 14 % (6–16 %), 2 % (1–3 %) and 7 % (4–11 %), respectively, of the European area. For a limit of 2 mg m−3 only two episodes with fractions of 1.5 % (0.2–2.8 %) and 0.9 % (0.1–1.6 %) occurred, while the current "No-Fly" zone criterion of 4 mg m−3 was rarely exceeded. Our results have important ramifications for determining air space closures and for real-time quantitative estimations of ash concentrations. Furthermore, the general nature of our method yields better constraints on the distribution and fate of volcanic ash in the Earth system.

scholarly journals Characterizing the Atmospheric Conditions Leading to Large Error Growth in Volcanic Ash Cloud Forecasts

2018 ◽  
Vol 57 (4) ◽  
pp. 1011-1019 ◽  
Author(s):  
H. F. Dacre ◽  
N. J. Harvey
Keyword(s):  
Flow Separation ◽  
Volcanic Ash ◽  
Dispersion Model ◽  
Forecast Accuracy ◽  
Large Error ◽  
Ensemble Member ◽  
Forecast Errors ◽  
Atmospheric Conditions ◽  
Wind Fields ◽  
Ensemble Forecasts

ABSTRACTVolcanic ash poses an ongoing risk to safety in the airspace worldwide. The accuracy with which volcanic ash dispersion can be forecast depends on the conditions of the atmosphere into which it is emitted. In this study, meteorological ensemble forecasts are used to drive a volcanic ash transport and dispersion model for the 2010 Eyjafjallajökull eruption in Iceland. From analysis of these simulations, the authors determine why the skill of deterministic-meteorological forecasts decreases with increasing ash residence time and identify the atmospheric conditions in which this drop in skill occurs most rapidly. Large forecast errors are more likely when ash particles encounter regions of large horizontal flow separation in the atmosphere. Nearby ash particle trajectories can rapidly diverge, leading to a reduction in the forecast accuracy of deterministic forecasts that do not represent variability in wind fields at the synoptic scale. The flow‐separation diagnostic identifies where and why large ensemble spread may occur. This diagnostic can be used to alert forecasters to situations in which the ensemble mean is not representative of the individual ensemble‐member volcanic ash distributions. Knowledge of potential ensemble outliers can be used to assess confidence in the forecast and to avoid potentially dangerous situations in which forecasts fail to predict harmful levels of volcanic ash.

scholarly journals Estimating the system efficiency to ensure aircraft flight safety

2015 ◽  
Vol 36 (1) ◽  
pp. 115-122
Author(s):  
Mariusz Zieja ◽  
Henryk Smoliński ◽  
Paweł Gołda
Keyword(s):  
Air Force ◽  
Analytical Method ◽  
Quantitative Estimation ◽  
Emergency Situation ◽  
Flight Safety ◽  
System Efficiency ◽  
Safety Assurance ◽  
Aircraft Flight ◽  
Assurance System ◽  
Random Nature

Abstract In the article was presented approach logical - probabilistic to assess the efficiency of the flight safety assurance system of aircraft considering that it is justified by the random nature of the process, which describe the indicators and logic is necessary during qualifying the threats and prevent such threats. Was proposed a method of quantitative estimation of system efficiency based on data and information collected in the information systems exploited in the Air Force. Was presented an analytical method for determining the probability of counteracting by the pilot emergency situation in-flight in cases where we have relevant data on the risks of flight safety. The probability of counteracting by the pilot emergency situation in-flight is even greater the higher the expected value and the lower the variance.

scholarly journals DID TECHNOLOGY IMPROVE SAFETY? AN EMPIRICAL STUDY OF CONTROLLED FLIGHT INTO TERRAIN ACCIDENTS

2015 ◽  
Vol 6 (1) ◽  
pp. 13-35 ◽  
Author(s):  
Cheng-Hua Yang ◽  
Alex
Keyword(s):  
Developed Countries ◽  
Aviation Safety ◽  
General Aviation ◽  
Flight Safety ◽  
Warning Systems ◽  
Commercial Aircraft ◽  
Mandatory Requirement ◽  
Civil Aircraft ◽  
Technological Improvements

Aviation safety has been affected greatly by technological improvements. A series of Ground Proximity Warning Systems (GPWSs) were developed to prevent accidents during Controlled Flight into Terrain (CFIT). This study analyzed the role of GPWS (or Enhanced GPWS, EGPWS) in flight safety history to determine how effective GPWS/EGPWS was in terms of preventing CFIT. The result showed a substantial increase in CFIT accidents due to the rapid growth of aviation development. This situation improved after the mandatory installation of GPWSs in commercial aircraft. However, the legal requirement did not apply to all general aviation. Most CFIT accidents have involved general aviation aircraft that do not have GPWS/EGPWS installed on board. Thus, the mandatory requirement should apply to all civil aircraft. CFIT accidents have also been reduced considerably in developed countries whereas they remain a major issue in developing countries.

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