• Atmospheric modeling of natural hazards

      Hirtl, Marcus; Stuefer, Martin; Webley, Peter; Simpson, William; Grell, Georg (2021-05)
      Airborne hazards either in gaseous form or particulate matter can originate from a variety of sources. The most common natural airborne hazards are ash and SO₂ released during volcanic eruptions, smoke emitted caused by wildfires and dust storms. Once released into the atmosphere they can have a significant impact on different parts of the environment e.g. air quality, soil and water, as well as air traffic and ground transportation networks. This latter field is an important aspect of everyday life that is affected during hazardous events. Aviation is one of the most critical ways of transport in this century. Even short interruptions in flight schedules can lead to major economic damages. Volcanic eruptions comprise one of the most important airborne hazards to aviation. These are considered rare as compared to severe weather, but with an extremely high impact. This dissertation focusses on dispersion modeling tools and how they can support emergency response during different phases of volcanic eruption events. The impact of the volcanic ash cloud on the prediction of meteorological parameters and furthermore the dispersion of the ash is demonstrated by applying the Weather Research Forecasting (WRF) model with on-line integrated chemical transport (WRF-Chem) to simulate the 2010 Eyjafjallajökull eruption in Iceland. Comprehensive observational data sets have been collected to evaluate the model and to show the added value of integrating direct-feedback processes into the simulations. The case of the Eyjafjallajökull eruption showed the necessity to further develop the volcanic emission preprocessor of WRF-Chem which has been extended for flexible and complex ash and SO₂ source terms. Furthermore, the thesis describes how scientists could support operational centers to mitigate hazards during a large volcanic eruption event. The author of the dissertation coordinated a large exercise including experts across all Europe within a project funded by the European Union. The exercise aimed to develop and test new tools, models, and data to support real-time decision making in aviation flight planning during a volcanic crisis event. New state-of-the-art modeling applications were integrated into a flight planning software during a fictitious eruption of the Etna volcano in Italy with contributions from scientists, the military and the aviation community.