Events on Thursday, August 22nd, 2024
- Thesis Defense
- Available Energy and Slow Eigenmodes for Understanding Moisture and Phase Changes in Atmospheric Physics
- Time: 10:00 am - 12:00 pm
- Place: 5280 Chamberlin -
- Speaker: Brad Kumm, Physics Graduate Student
- Abstract: In atmospheric physics, clouds and moisture are some of the greatest challenges. They are the leading source of uncertainty in climate change predictions, and rainfall is arguably the most challenging quantity to predict in weather forecasts. In addition, theoretical understanding of moisture in the atmosphere lags behind the understanding of a dry atmosphere. To increase our theoretical understanding of moisture in the atmosphere this work focuses on two concepts: (i) Energy, and in particular Available Potential Energy (APE), and (ii) slow eigenmodes. The first results presented center around a new decomposition of APE for a compressible, adiabatic atmosphere with phase changes, and shows that it can be decomposed into acoustic and buoyant pieces, which are present in dry decompositions, as well as a new slow "latent" piece which accounts for a parcel changing between saturated, and unsaturated states. Second, a method is presented to account for moisture in a global atmospheric decomposition framework, by splitting it into an Inertio-gravity piece, a Rossby piece, and an additional "slow" piece which accounts for a large fraction of the total atmospheric moisture. Finally, such a decomposition is performed using global moisture data, in what may be the first moist decomposition of this kind, in order to quantify the relative contributions of each of these pieces.
- Host: Samuel Stechmann, Jan Egedal
- Preliminary Exam
- Line Intensity Mapping: A Novel Technique to Measure Large Scale Structure and Galaxy Evolution
- Time: 2:00 pm - 4:00 pm
- Place: B343, Sterling Hall
- Speaker: Sam Kramer, Physics PhD Graduate Student
- Abstract: Understanding the formation and development of the Universe's large scale structure (LSS) is the primary goal of cosmology. The earliest stage of the Universe has been well-measured via the cosmic microwave background, and traditional, large-spectrum surveys have mapped the most recent epochs. Line intensity mapping (LIM) is a novel technique that seeks to fill in the billions of years of evolution in between. LIM experiments record the atomic/molecular transition line emissions of common galactic constituents from many galaxies at once, requiring less integration time and lower resolutions to efficiently map LSS over a broad range of redshifts. The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a LIM pathfinding mission that seeks to measure the [CII] emission line of ionized carbon at redshifts 2.5 to 3.5, corresponding to a period in the Universe with the highest rates of new star formation. [CII] is believed to be a tracer of both star formation and the large scale structure of the universe, but current empirical models for this relationship vary across orders of magnitude. Using simulations and existing survey data, we can develop cross-correlation techniques like the cross power spectrum, stacking, and the conditional voxel intensity distribution to predict [CII] detection at high SNRs and constrain the [CII] emission models with EXCLAIM.
- Host: Peter Timbie