Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session L36: Physics of Natural PhenomenaInvited Undergraduate
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Sponsoring Units: DMP Chair: Antoinette Taylor, Los Alamos National Laboratory Room: BCEC 205C |
Wednesday, March 6, 2019 11:15AM - 11:51AM |
L36.00001: Fire/atmosphere Feedbacks that Control Wildland Fire Invited Speaker: Rodman Ray Linn Wildfires pose a threat to life, property and critical infrastructure, but wildland fire is an unavoidable part of the nature. In order to improve our ability to cope with wildfires and anticipate their evolving roles on the earth system we need to better understand how they interact with their environment. Recent fire behavior research illustrates the importance of the two-way feedbacks between fires and the surrounding atmosphere, which is influenced by the vegetation structure and topography as well as ambient winds. The effectiveness and consequences of fuels management activities are tied not only on the removal of combustible fuel, but also on the changes in the ventilation induced by decreased vegetation drag, which can potentially increase fire spread. Safe use of prescribed fires to reduce fire risk while accomplishing ecologic objectives typically depends on fire practitioner’s ability to anticipate the interaction of multiple fires. This interaction is controlled by the competition between their fire-induced indrafts. Topographic influences on fire behavior are dominated by terrain-induced changes in entrainment patterns that control the patterns of heat transfer to unburned fuel. Multi-scale two-way fire/atmosphere feedbacks determine heterogeneous fire line dynamics and thus fire spread, the effects of fires on ecology and the near-field lofting and transport of the smoke. Unfortunately, deciphering the complex interaction between fires and surrounding atmosphere through field and laboratory experiments alone has been challenging, but recent advancements in computing power have created new opportunity for the complimentary use of numerical models to provide additional perspectives concerning fire/atmosphere feedbacks that have previously been challenging to explore. Examples of ways that the interactions between fire and surrounding atmosphere dictate fire behavior and the use of numerical models to investigate this coupling will be discussed. |
Wednesday, March 6, 2019 11:51AM - 12:27PM |
L36.00002: The Physics of Climate and Climate Change Invited Speaker: Kerry Emanuel The talk will begin with a broad overview of climate science, including the history of the science itself, and what we have learned about the Earth’s climate system through analysis of paleoclimate data, the instrumental record, and, most importantly, the fundamental physics, chemistry, and biology underlying the climate system. Projections of future climates, made using both simple and complex models, will be discussed, with an emphasis on sources of uncertainty together with an assessment of whether and to what extent the level of uncertainty can be reduced. I will end the talk with reflections on how physicists might help find solutions for mitigating climate change. |
Wednesday, March 6, 2019 12:27PM - 1:03PM |
L36.00003: Mixed signals in future climate extremes: understanding counterintuitive results Invited Speaker: Sarah Kapnick If temperatures warm in the future, if everything else remains constant, there should be less snowfall since temperatures will rise above freezing more often. If we know a region will become drier on average in the future, and storms have constant rainfall amounts, the likelihood of extreme events should decline. But these stationarity assumptions do not hold true, resulting in what can appear to be counterintuitive changes in climate phenomena and extremes. We will discuss where snowfall accumulation and blizzards may actually increase and why some glaciers have been expanding. We will also discuss why a region may become drier overall, but also have increased risk for extreme precipitation events. While these regional changes may seem counterintuitive, they can actually be explained by unique conditions, seasonality, and changes in atmospheric moisture. |
Wednesday, March 6, 2019 1:03PM - 1:39PM |
L36.00004: Physics of Earthquakes: The Real Earthshaking Science Invited Speaker: Rachel E Abercrombie The study of earthquakes is driven by the desire to understand our dynamic planet and to minimize the devastation that earthquakes can cause. Earthquake science spans a huge range of temporal and spatial scales. The largest earthquakes rupture faults that are 100s to 1000s of kilometers long but start from nucleation regions so small that they have never been reliably observed. Earthquake faults move at only millimeters to centimeters a year but earthquake ruptures propagate at speeds of kilometers a second, and most earthquakes last less than a minute. |
Wednesday, March 6, 2019 1:39PM - 2:15PM |
L36.00005: The mechanics of hydraulic fractures in glaciers, volcanoes, and reservoirs Invited Speaker: Brad Lipovsky Fractures that interact with fluid are ubiquitous in Earth systems. In the floating ice shelves that fringe the grounded Antarctic Ice Sheet, hydraulic fractures pose a threat to ice sheet stability. Hydraulic fractures in volcanoes transport magma and other fluids through Earth's crust. And hydraulic fractures may be engineered to improve the performance of geothermal energy resources. The mechanical analysis of hydraulic fractures may take several viewpoints, of which I focus on two. First, linear elastic fracture mechanics provides insight into the dynamics of hydraulic fractures at shallow depths above the brittle--ductile transition. Second, active hydraulic fractures may create mechanical vibrations that are observable at distant seismometers. In both instances, geophysical data and mechanical analyses together provide insights into stunning natural phenomena that have direct bearing on human civilization. |
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