modelling: geology and meteorology Earth, wind and fire


From natural disasters to natural resources, modelling and simulation software is improving knowledge, as


Warren Clark discovers


by soſtware packages. Te results are used to predict future movements of, for example, volcanic ash – or to identify the most productive process for mining coal.


W


Ashes to ashes At the Barcelona Supercomputing Center (BSC), Arnau Folch, has been working as part of the Environmental Simulations Group to provide numerical modelling of volcanic ash clouds. Explosive volcanic eruptions eject into


the atmosphere enormous quantities of particulate matter, globally known as tephra, that is dispersed by winds at scales from local to continental. Millimetric particles sediment and fall out, causing an array of impacts on local communities, infrastructures and ecosystems. In contrast, micrometric-size particles (volcanic ash) can remain airborne for days to weeks, in the form of ash clouds that jeopardise aerial navigation. Volcanic Ash Advisory Centers (VAACs)


are the official institutions tasked by the International Civil Aviation Organization (ICAO) with monitoring and forecasting of ash clouds within their assigned airspace. Although the 2010 Iceland eruption was the most disruptive event in recent history, VAACs have been around since the mid-90s. VAACs make use of satellite imagery


and Volcanic Ash Transport and Dispersal Models (VATDMs) to produce six-hourly forecasts that are used by civil aviation authorities to close contaminated airspace and aircraſt re-routing. Te recent disruptions caused by Eyjafallajökull (Iceland, 2010) and Cordón Caulle (Chile, 2011) volcanoes have evidenced some flaws in the operational strategies and lead to an examination of VATDMs. ‘Te community realised that existing codes and modelling


30 SCIENTIFIC COMPUTING WORLD The Eyjafjallajokull eruption in May 2010 wreaked havoc with international flights


strategies were not as good as could be,’ says Folch. ‘Moreover, different VAACs use different codes and modelling strategies.’ Te BSC group develops and maintains


FALL3D, a parallel VATDM running at scales from local to continental, and used at the VAAC in Buenos Aires. Several other users apply the model worldwide for a number of purposes including operational forecast of tephra fallout and ash clouds or generation of probabilistic maps for long-term hazard


THE CODE COULD RUN ON A PC, BUT IN ORDER TO ACHIEVE USEFUL RESULTS, HPC IS REQUIRED


and risk assessment (for example, Australia Geoscience or the members of the Latin- American thematic network CENIZA). In turn, the group is also developing a GIS- based tool for short- and long-term air traffic management aimed at providing decision support to stakeholders, decision-makers and other model end users. ‘Originally, we developed the code just to


monitor and predict ground-level fallout,’ says Folch. ‘But now, it is used mostly for predicting the concentration of ash in the air, which is why the civil aviation industry has become interested in it.’ Te code itself could run on a standard


PC – but, in order to achieve the results at the speed at which they are useful, HPC is required. ‘In an emergency, speed of the code is important,’ says Folch. ‘Te problem is that there is still great uncertainty during an eruption, since we are dependent on live data being fed into the model in order for it to be accurate. It is very difficult to measure all the factors in an eruption in real time. We mainly need to know how much ash has erupted, and how it is distributed within the cloud. If we are able to feed in satellite imagery and data from ground-based systems, the model can be more accurate. So, in the early stages of an eruption, prediction is very difficult. ‘Also, some volcanoes are very well


monitored, while others are in remote locations that may not even have proper satellite coverage; that will clearly have an effect on the quality of the model we can generate. ‘HPC is still not widely used within the


@scwmagazine l www.scientific-computing.com


hether it’s up in the sky or under our feet, the natural world and all its complexities are increasingly being modelled


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