Past Colloquia
Abstracts from past colloquia and seminars
2016-03-23 Cory Barton Defense
âSpatio-Temporal Evolutions of Non-Orthogonal Equatorial Wave Modes Derived from Observationsâ
Speaker
Cory Barton
Geophysical Fluid Dynamics Ph.D. Candidate
Florida State University
(Major Professor: Dr. Ming Cai)
Time: Wednesday, March 23, 2016 at 1:00PM
Place: Melvin Stern Seminar Room Room 18 Keen Bldg.
Dissertation Defense will follow the seminar
Abstract: Equatorial waves have been studied extensively due to their importance to the tropical climate and weather systems. The non-orthogonality of wave modes has yet posed a problem when attempting to separate data into instantaneous wave fields where the waves project onto the same structure functions. We propose the development and application of a new methodology for equatorial wave expansion of instantaneous flows using the full equatorial wave spectrum. By mapping the meridional structure function amplitudes to the equatorial wave class amplitudes, we are able to diagnose instantaneous wave fields and determine their evolution.
The wave class spectra diagnosed assuming the peak projection response depth scale mostly match their expected dispersion curves, showing that this method successfully partitions the wave spectra by calculating wave amplitudes in physical space. This is particularly striking because the time evolution, and therefore the frequency characteristics, is determined simply by a timeseries of independently-diagnosed instantaneous horizontal fields. Vertical tilting in the wave fields is similarly diagnosed across multiple pressure levels. We have confirmed the continuous evolution of the QBO selection mechanism for equatorial waves in the tropical middle atmosphere and additionally identified a time-evolution of the zonal wavenumber spectrum responsible for the amplitude variability in physical space.
2016-03-14 Mark Sussman Seminar
âAn adaptive coupled levelset and moment-of-fluid method for simulating droplet impact and icing on solid surfaces.â
Dr. Mark Sussman
Professor of Mathematics
Florida State University
Time
Monday, March 14, 2016 at 1:00PM
Place
Melvin Stern Seminar Room
Room 18 Keen Bldg.
Refreshments will be served at 12:45PM
Abstract:
A new numerical method is presented for simulating droplet impact and icing on solid surfaces. The four materials, air, liquid, ice, and solid are represented using the coupled level set and moment-of-fluid interface reconstruction method. The moment-of-fluid interface reconstruction algorithm has volume and linearity preserving properties using only local information within a computational cell, and for any number of materials. The ghost fluid numerical method has been implemented so that solutions are consistent with the jump conditions at the interface(s) taking into account surface tension, triple point conditions, contact line dynamics, phase change, expansion of ice, and heat release. Results are presented in 2D, RZ, and 3D coordinate systems which demonstrate the effect of surface wetting properties on the resulting drop impact and solidification.
The presented numerical method is general enough to be applied to many scenarios where materials change phase. An example of the application of the new method to nucleate boiling problems in microgravity environments
will be presented too.
2016-02-19 Eli Tziperman Seminar
Title
âCOLD: Snowball Earth ocean circulation, and WARM: suppression of Arctic air formation in warm climatesâ
Speaker
Dr. Eli Tziperman
Professor of Oceanography and Applied Physics
Department of Earth & Planetary Sciences
Harvard University
Time
Friday, February 19, 2016 at 2:30PM
Placce
Melvin Stern Seminar Room, 018 Keen Bldg.
Refreshments will be served at 2:00PM
Abstract:
Part I: The hypothesized complete freezing of the Earth during the Snowball Earth events of the Neoproterozoic Era (1,000 to 542 Myr) poses several interesting problems, testing our understanding of ocean dynamics in an unusual dynamical regime. An ocean covered by thick ice and driven only by a very weak geothermal heat flux (0.1 watts/m^2) is shown to be surprisingly dynamic, characterized by strong zonal jets, an energetic turbulent eddy field and a dramatic meridional overturning circulation limited to very close to the equator. We discuss the dynamics of the mean zonal jets and meridional circulations, the Lorenz energy cycle and the relevant eddy-generating instability mechanisms.
Part II: High-latitude continents have warmed much more rapidly in recent decades than the rest of the globe, especially in winter, and the maintenance of warm, frost-free conditions in continental interiors in winter has been a long-standing problem of past equable (warm) climates. We study the polar night process of air mass transformation from high-latitude maritime air, to much colder high-latitude continental air. We find that, in warm climates, a low-cloud feedback considerably slows radiative cooling of the surface and amplifies continental warming. This mechanism may explain recent continental warming and indicates that optically thick low clouds could help maintain frost-free winter continental interiors in equable climates.
2016-01-25 Yueyue Yu Seminar
âFeeling the Pulse of the Stratosphere: An Emerging Opportunity for Predicting Continental-Scale Cold Air Outbreaks One Month in Advanceâ
Speaker:
Dr. Yueyue Yu
Geophysical Fluid Dynamics Institute
Florida State University
Time: Monday, January 25, 2016 at 2:30PM
Place: Melvin Stern Seminar Room
Room 18 Keen Bldg. Refreshments will be served at 2:00PM
Abstract: Extreme weather events such as cold air outbreaks (CAOs) pose great threats to human life and socioeconomic well-being of the modern society. In the past, our capability to predict their occurrences is constrained by the 2-week predictability limit for weather. We demonstrate here a new source of sub-seasonal predictability of CAOs: a rapid increase of air mass transported into the polar stratosphere, referred to as âthe pulse of the stratosphere (PULSE)â. Firstly, such PULSEs can be directly derived from the output fields of operational models once they are generated and often be predicted with a useful skill 4â6 weeks in advance by operational forecast models, such as CFSv2; and secondly, the PULSE events have robust diagnostic relations with the timing of individual continental-scale CAO events in northern hemispheric mid-latitudes, namely the probability of the occurrence of continental-scale CAOs increases substantially above the normal condition within a short time period from one week before to 1-2 weeks after the peak day of a PULSE event. Those advantages of PULSEs inspired us to construct a hybrid paradigm (dynamical and statistical) for forecasts of CAOs one month in advance. To test this idea, we have inaugurated a real time forecast experiment since the winter of 2014â15, which is mainly supported by Geophysical Fluid Dynamics Institute, FSU and leaded by Prof. Ming Cai.
2015-12-04 Schoonover Defense
âTopographic Wave Arrest and the
Gulf Stream Separationâ
Speaker
Joseph Schoonover
Geophysical Fluid Dynamics Ph.D. Candidate
Florida State University
(Major Professor: Dr. W. Dewar)
Time
Friday, December 4, 2015 at 9:00 AM
Place
Melvin Stern Seminar Room
Room 18 Keen Bldg.
2015-11-02 Lakshika Girihagama Seminar
âLocal cooling despite global warmingâ
Lakshika Girihagama
Geophysical Fluid Dynamics Ph.D. Candidate
Florida State University
Time
Monday, November 2, 2015 at 2:30 PM
Place
Melvin Stern Seminar Room
Room 18 Keen Bldg.
Dissertation Defense will follow the seminar
2015-09-25: WKP Workshop
WKP Workshop
2015-02-05: Andy Thompson Seminar
âA Multi-basin Residual Mean Model of the Global Overturning Circulationâ
Dr. Andrew F. Thompson
Department of Environmental Science and Engineering
California Institute of Technology
Pasadena, CA
Time
Monday, November 2, 2015 at 12:00 Noon
Place
Melvin Stern Seminar Room
Room 18 Keen Bldg.
Refreshments will be served at 11:30 AM