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

Harvey, Nicholas Peter; Huntley, Nathan; Dacre, Helen; Goldstein, Michael; Thomson, David J.; Webster, Helen

doi:10.5194/nhess-18-41-2018

Cited by 42 publications

(65 citation statements)

References 47 publications

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“…Of six eruption source parameters and 12 internal model parameters, Harvey et al . () found that NAME outputs are most sensitive to plume height, MER, the precipitation threshold for wet deposition, and free tropospheric turbulence. We suggest uncertainty due to the model physics is less than the uncertainty in source parameters.…”

Section: Discussionmentioning

confidence: 99%

The importance of grain size and shape in controlling the dispersion of the Vedde cryptotephra

Saxby

Rust

Cashman

et al. 2019

J Quaternary Science

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Volcanic ash is dispersed in the atmosphere according to meteorology and particle properties, including size and shape. However, the multiple definitions of size and shape for non-spherical particles affect our ability to use physical particle properties to understand tephra transport. Moreover, although particles >100 m μ are often excluded from operational ash dispersion model setups, ash in tephra deposits > 1000 km from source can exceed 100 m μ . Here we measure the shape and size of samples of Vedde ash from Iceland, an exceptionally widespread tephra layer in Europe, collected in Iceland and Norway. Using X-ray computed tomography and optical microscopy, we show that distal ash is more anisotropic than proximate ash, suggesting that shape exerts an important control on tephra dispersion. Shape also impacts particle size measurements. Particle long axis, a parameter often reported by tephrochronologists, is on average 2.4× greater than geometric size, used by dispersion modellers. By using geometric size and quantifying shape, we can explain the transport of Vedde ash particles 190 m ≤ μ more than 1200 km from source. We define a set of best practices for measuring the size and shape of cryptotephra shards and discuss the benefits and limitations of using physical particle properties to understand cryptotephra transport. Figure 3. Balloon-borne radiosonde data for the weather stations at (a) Keflavík, Iceland, (b) Tórshavn, Faroe Islands, and (c) Ørland, Norway. Station codes correspond to locations in Fig. 2. Coloured lines show monthly mean speed at each height for the period 1973 -2018. Dashed lines show individual records for days with extremely high winds, with the day and time chosen based on the highest (height-averaged mean) wind velocities. [Color figure can be viewed at wileyonlinelibrary.com].

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Section: Discussionmentioning

confidence: 99%

The importance of grain size and shape in controlling the dispersion of the Vedde cryptotephra

Saxby

Rust

Cashman

et al. 2019

J Quaternary Science

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“…Emulators have been used in several studies to analyze complex models in multiple scientific fields including tsunami modeling (Sarri et al, 2012), aerosol and cloud modeling (e.g., Carslaw et al, 2013;Hamilton et al, 2014;Johnson et al, 2015;Lee et al, 2013;Regayre et al, 2014Regayre et al, , 2015, and galaxy formation (Rodrigues et al, 2017;Vernon et al, 2010). A recent study by Harvey et al (2018) also successfully applied this approach to volcanic ash modeling of the 2010 Eyjafjallajökull eruption to understand the influence of eruption source parameters and internal model parameters on the simulated output.…”

Section: Emulation and Sensitivity Analysismentioning

confidence: 99%

Exploring How Eruption Source Parameters Affect Volcanic Radiative Forcing Using Statistical Emulation

et al. 2019

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The radiative forcing caused by a volcanic eruption is dependent on several eruption source parameters such as the mass of sulfur dioxide (SO2) emitted, the eruption column height, and the eruption latitude. General circulation models with prognostic aerosol and chemistry schemes can be used to investigate how each parameter influences the volcanic forcing. However, the range of multidimensional parameter space that can be explored is restricted because such simulations are computationally expensive. Here we use statistical emulation to explore the radiative impact of eruptions over a wide covarying range of SO2 emission magnitudes, injection heights, and eruption latitudes based on only 30 simulations. We use the emulators to build response surfaces to visualize and predict the sulfate aerosol e‐folding decay time, the stratospheric aerosol optical depth, and net radiative forcing of thousands of different eruptions. We find that the volcanic stratospheric aerosol optical depth and net radiative forcing are primarily determined by the mass of SO2 emitted, but eruption latitude is the most important parameter in determining the sulfate aerosol e‐folding decay time. The response surfaces reveal joint effects of the eruption source parameters in influencing the net radiative forcing, such as a stronger influence of injection height for tropical eruptions than high‐latitude eruptions. We also demonstrate how the emulated response surfaces can be used to find all combinations of eruption source parameters that produce a particular volcanic response, often revealing multiple solutions.

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“…Sensitivity studies have prioritized the importance of the ESPs, indicating that plume height, MER and PSD are the key parameters when modelling the movement of volcanic ash clouds, while particle shape has a lesser but still important role [51,53,71,72]. The MER and particle characteristics are hard to measure, and it is highly unlikely that we will be provided with this information in real-time during an event.…”

Section: Improvements To Model Initializationmentioning

confidence: 99%

Atmospheric Dispersion Modelling at the London VAAC: A Review of Developments since the 2010 Eyjafjallajökull Volcano Ash Cloud

et al. 2020

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It has been 10 years since the ash cloud from the eruption of Eyjafjallajökull caused unprecedented disruption to air traffic across Europe. During this event, the London Volcanic Ash Advisory Centre (VAAC) provided advice and guidance on the expected location of volcanic ash in the atmosphere using observations and the atmospheric dispersion model NAME (Numerical Atmospheric-Dispersion Modelling Environment). Rapid changes in regulatory response and procedures during the eruption introduced the requirement to also provide forecasts of ash concentrations, representing a step-change in the level of interrogation of the dispersion model output. Although disruptive, the longevity of the event afforded the scientific community the opportunity to observe and extensively study the transport and dispersion of a volcanic ash cloud. We present the development of the NAME atmospheric dispersion model and modifications to its application in the London VAAC forecasting system since 2010, based on the lessons learned. Our ability to represent both the vertical and horizontal transport of ash in the atmosphere and its removal have been improved through the introduction of new schemes to represent the sedimentation and wet deposition of volcanic ash, and updated schemes to represent deep moist atmospheric convection and parametrizations for plume spread due to unresolved mesoscale motions. A good simulation of the transport and dispersion of a volcanic ash cloud requires an accurate representation of the source and we have introduced more sophisticated approaches to representing the eruption source parameters, and their uncertainties, used to initialize NAME. Finally, upper air wind field data used by the dispersion model is now more accurate than it was in 2010. These developments have resulted in a more robust modelling system at the London VAAC, ready to provide forecasts and guidance during the next volcanic ash event.

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

Cited by 42 publications

References 47 publications

The importance of grain size and shape in controlling the dispersion of the Vedde cryptotephra

The importance of grain size and shape in controlling the dispersion of the Vedde cryptotephra

Exploring How Eruption Source Parameters Affect Volcanic Radiative Forcing Using Statistical Emulation

Atmospheric Dispersion Modelling at the London VAAC: A Review of Developments since the 2010 Eyjafjallajökull Volcano Ash Cloud

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