Using stochastic NWP ensembles for volcanic ash transport and dispersion model outcomes
Abstract
Ash clouds ejected into the atmosphere by volcanic eruption extend over large areas and can travel thousands of kilometers from the source volcano, disrupting air traffic and posing a significant hazard to air travel. Volcanic ash transport and dispersion models like the PUFF model simulate the ash transport and dispersion. An important input parameter for such simulations are wind fields. They represent one of the major sources for uncertainties in ash transport and dispersion simulations. Ensemble methods are considered to be an effective way to estimate the probability density function of future states of the atmosphere by addressing uncertainties present in initial conditions and in model approximations. To generate localized wind ensemble we are using the Weather Research and Forecast (WRF) model with various initial conditions. We examine the spatial variability of the wind fields as well as their uncertainty by using two methods to simulate uncertainty on initial conditions. First method was developed by National Centers for Environmental Prediction (NCEP) and it is based on breeding vectors [2], while the second method was proposed by [1] and uses a distribution of the initial conditions to describe the confidence in the knowledge of the initial state of the atmosphere. PUFF runs are performed with the above wind fields for the eruption of Eyjafjallajokull, Iceland which had a peak ash emission in the period 15-20 April 2010.. A variety of model outputs are compiled, including snapshots of airborne-ash concentration (relative to the number of particles released at the start of the simulation) and particle location color-coded by height which shows the sensitivity of these outputs to wind fields. [1] E. Constantinescu, V. Zavala, M. Rocklin, S. Lee, and M. Anitescu. A com- putational framework for uncertainty quantification and stochastic optimiza- tion in unit commitment with wind power generation. IEEE Transactions on Power Systems, 2010. [2] Z. Toth and E. Kalnay. Ensemble forecasting at ncep and the breeding method. Mon. Wea. Rev, 126:3292-3302, 1997.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMNG51B1771P
- Keywords:
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- 0370 ATMOSPHERIC COMPOSITION AND STRUCTURE / Volcanic effects