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PHSC 13600 Natural Hazards Only a few days into 2020, we’ve already seen some major natural disasters unfold: Australia is being ravaged by the worst wildfires in decades with 18 casualties and more than 1000 homes destroyed. On New Year’s Eve Indonesia was hit by a record rainfall which caused an extreme flooding in Jakarta, killing more than 50 people and displacing 175,000 people. Other notable events in 2019: 900 people perished in Mozambique and Zimbabwe in March due to a historic tropical cyclone Idai. In June and July more than 250 people died from heat waves in India and Japan. In August an intense hurricane Dorian wreaked havoc on the Bahamas and the eastern seaboard of the US. In October a supertyphoon Hagibis hit Japan and killed over 80 people and caused flood damage worth billions of dollars. Also in October, Sonoma County, CA, sustained a major wildfire, which will impact the region’s tourism for years to come. In December, a volcano on White Island of New Zealand erupted and killed 19 tourists and 18 people injured. These incidents are a reminder that we live in a dynamic environment, where extreme and adverse conditions do arise. Making society more resilient to the risks of natural hazards is of practical importance, and to meet that need it is essential to understand how our environment works and how our action can affect the outcome of hazards. But then irrespective of the societal need, there is something awe-inspiring about the forces of nature that arouses our curiosity. Whether your motivation is public service or pure curiosity, you will learn a few things about what we call natural hazards in this course: •

Hazards as natural processes

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Why/when does a hazard become a disaster?

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How to use statistics to quantify risks and to relate long-term changes and extreme events

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How principles and concepts of physics are used to understand complex meteorological and geological phenomena

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Geography and frequency of hazards

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Mechanisms of specific hazards

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How different types of natural hazards affect society and how to minimize risks

What we cover in this course is part of earth science, collectively the study of the physical properties of our planet and of the solar system. However the materials of this course are organized around the theme of natural hazards and our responses to them. As such, the course includes, in addition to physics, some elements of statistics and human geography. How earth science works Earth science is an applied science, meaning it applies the fundamental principles of physics, chemistry, and biology to understand the planet’s physical environment. Even though the principles themselves are well understood, how to apply them makes all the difference

because the objects in earth science involve enormous degrees of freedom (many interacting elements). The result is a very complex problem – one that cannot be solved exactly by hand or even with computers (e.g., prediction of hurricanes or earthquakes). To make the problem manageable, scientists often focus on the essential aspects and make simplifying assumptions. They then form a model, a representation of reality, with varying levels of sophistication – for example it may be a physical experiment in a laboratory or an equation-based mathematical model. Models play an important role in testing hypotheses (e.g., ‘the strength of hurricanes increases with increasing sea surface temperatures’) because one can play with models in ways that are not possible with the real environment. Of course to test a hypothesis and verify the model itself, the output of the model must be compared with observed data. If both the model and collected data are perfect, they should match exactly. In reality this almost never happens, since neither the model nor the data reflects the full complexity of reality. (Sometimes they match for wrong reasons!) The model’s accuracy depends on the degree of sophistication. Observed data contain measurement errors. In some cases direct observations are not available at all – e.g., for the interior of Earth or deep oceans. So there is always a level of uncertainty, and a reliable conclusion is reached only after many cases of model-data comparison are performed, often using many independent models and data from different researchers. In the context of disaster readiness, quantifying the uncertainty in the prediction is as important as the prediction itself. Earth scientists routinely use statistics to process and interpret a large amount of data and evaluate the confidence level and uncertainty of their results. You will taste some of these flavors of scientific inquiries throughout the course. Lecture synopsis Lectures 1-6. Here we concern basic concepts and principles, starting with the definition of natural hazards, general strategies for prediction/forecast, the use of statistics to quantify and interpret risks, and application of first principles (conservation of energy and momentum) in the context of hazards. In these lectures discussion often drifts away from the textbook (except ch.1) and involves more abstract, quantitative development than the subsequent lectures. This conceptual development is important because it lays out a common framework/language with which to approach and analyze seemingly unrelated hazards, keeping the course from becoming an encyclopedic description of random phenomena. In particular, I will expound on moist thermodynamics, radiation, and fluid mechanics necessary to understand observed properties and processes of the atmosphere. These include temperature distribution, global wind patterns and precipitation (the areas in which theory is well developed and data corroborate it). Try to follow the logic of theory closely, and keep asking ‘why?’ and ‘what if?’ Lectures 7-11. The actual description of natural hazards starts here (with lots of information to process!). We will touch on various forms of weather-related hazards, including extratropical cyclones and fronts, tropical cyclones and storm surge, thunderstorms, lightning and tornadoes, heat waves, droughts, and wildfires. In this part of the course the lectures largely parallel the descriptions in the textbook, although additional materials may be used. Explanation draws on the concepts developed in Lectures 1-6 but otherwise remains descriptive and qualitative. In addition to their physical mechanisms, we will discuss geography and statistics of the hazards, as well as their interaction with society, sometimes using case studies of actual events. We will also look at how slow, naturally occurring climate

variabilities (e.g., El Niño Southern Oscillation and North Atlantic Oscillation) modulate the location and frequency of extreme weather. Lectures 12-18. In these lectures we deal with geologic and hydrologic hazards such as earthquakes, tsunamis, volcanoes, flooding and bolide impacts. Geologic processes are driven by plate tectonics, a slow movement of Earth’s fragmented crust, which in turn is propelled by an overturning deep layer of Earth’s mantle. While the concept of plate tectonics has been firmly established, precise prediction of earthquakes and volcanic eruptions remains an elusive goal. We will go over the current understanding and state-of-the-art mitigation techniques and warning systems of geologic hazards. (You’ll see why Chicago is not entirely free from the risk of earthquake.) Other topics include historic and more recent tsunamis, river dynamics and floods, and flood control methods. The course concludes by expanding the scale in both time and space, discussing the impacts of falling meteors and associated extinction events in the past. Most of these lectures closely follow the textbook chapters. See syllabus for the timeline and reading plans....