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Speaker: Christina Patricola, Lawrence Berkeley National Laboratory

Host: Pedro DiNezio

Title: Natural and Anthropogenic Influences on Tropical Cyclones

Abstract: Tropical cyclones (TCs) are among the costliest and deadliest natural hazards. There are numerous influences on TCs that can originate from the atmosphere and ocean, act constructively or compensate, operate on timescales spanning weather to climate, and arise from natural variability or anthropogenic forcings. Due to this complex set of factors, as well as the limited period of consistent observations, I use ensembles of convection-permitting regional climate model experiments to uncover causal relationships. Starting with anthropogenic change, I will (1) discuss how the intensity and rainfall of 15 recent destructive TCs could be different if similar events were to occur in pre-industrial and future climates. On the topic of TC variability, I will (2) demonstrate that Atlantic TCs are not limited by their typical precursor (African easterly waves) on the climate timescale, and (3) discuss the influence of the diverse spatial patterns of El Niño’s sea-surface temperature (SST) warming on TCs. Finally, I will (4) present a new index for the El Niño-Southern Oscillation (ENSO) that, for the first time, uniquely captures ENSO’s diversity and extremes and accounts for both the nonlinear response of deep convection to SST and background SST changes associated with the seasonal cycle and climate change. Altogether this research sheds light on the ongoing debate as to whether climate change has yet affected TCs and identifies the utility of potential atmospheric and oceanic sources of seasonal-centennial TC predictability.

Speaker: Carlos Calderon, Senior Geophysicist, ION Geophysical

Host: Mrinal Sen

Title: Improving the resolution of the velocity model with full-waveform inversion of diving waves and reflections

Abstract: Deriving an accurate subsurface velocity model in complex geology requires seismic data with long offsets and wide signal bandwidth in combination with high-resolution model building and imaging methods. Full waveform inversion (FWI) has become a powerful tool for improving the shallow part of the velocity. This type of inversion makes use mostly of first arrivals from the longest offsets. Signal from smaller offsets and later times extend the depth range and resolution of FWI. A top-down FWI approach in combination with offset and frequency staging potentially produces a robust and accurate velocity model that improves the image. Furthermore, the inverted model can be used as a product for quantitative interpretation with post-stack or pre-stack inversion methods. We illustrate the benefits of a FWI flow with field data.

Informal weekly presentations by UTIG students and researchers. Bring your lunch!

This week: Chasing ice in Greenland and Alaska from beneath the sea surface, improving multibeam techniques

Speaker: Dan Duncan, Research Scientist Associate IV, UTIG

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Important note: This is a live-only event. The presentation will be streamed live but there will be no recording available after the event.

Speaker: Gregor Steinbrügge, UTIG

Host: Don Blankenship

Title: Tides of Planets and Satellites

Abstract: Tidal interactions and resulting deformation of planets and satellites are key to understand the dynamics of our Solar System. Tides are relevant for the rotational state of bodies, their orbital evolution, thermal state and are important for assessing the habitability of icy satellites in the outer Solar System. I will summarize the current understanding of tidal processes and how they link to the interior structure and orbital evolution of terrestrial and icy bodies. I will outline the theoretical basics, related observations and also highlight the future challenges in view of the upcoming missions Europa Clipper, Jupiter Icy Moon Explorer and BepiColombo to worlds affected by tides.

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Speaker: Sarah Brownlee, Wayne State University

Host: Rob Porritt

Title: Seismic anisotropy in the middle and lower continental crust: using rocks to improve seismic interpretations

Abstract: Seismic anisotropy, the directional dependence of seismic velocity, has been an invaluable tool for understanding strain and flow in the upper mantle. The utility of seismic anisotropy in the upper mantle can be attributed in part to a wealth of studies characterizing the properties of mantle rocks and minerals. In contrast, the continental crust is not nearly as well-characterized due in large part to its very small volume in relation to global seismic raypaths. The continental crust also poses numerous complexities in mineralogy and structure making it significantly more difficult to characterize. Recently, a number of studies have been focused on characterizing the full anisotropic elasticity of rocks from the continental crust. These studies have motivated efforts to predict how these rocks will appear in seismic observations, and thus to recalibrate the assumptions used in seismic inversions in order to improve our ability to distinguish various rock types and deformation in the continental crust. I will begin by discussing the basics of seismic anisotropy and how it is observed. Then we will delve into the catalogue of crustal rock properties, reviewing some of the trends in elastic symmetry with deformation and rock type in the continental crust. I will present a simple scaling scheme to allow for more realistic non-elliptical hexagonal elastic tensors in seismic inversions, and discuss how real crustal rocks might appear in seismic data. The take home message is that while the continental crust is complicated, it cannot be ignored, because even when the focus of study is the mantle, most of our observations are made through the window of the continental crust. Further characterization of the elastic properties of crustal rocks, and how these rocks are expressed in seismic data will improve our ability to use seismic methods to understand deformation in and beyond the continental crust.