Walter Hannah

Ph.D. Candidate
Maloney Research Group

Department of Atmospheric Science
Colorado State University
1371 Campus Delivery
Fort Collins, CO 80523-1371

(970) 491-1487

whannah (at) atmos.colostate.edu

Curriculum Vitae



MS Research

The Role of Moisture-Convection Feedbacks in Simulating the Intraseasonal Oscillation

My master's thesis analyzed the sensitivity of the NCAR Community Atmosphere Model (CAM) to varying strength of the Tokioka et al. (1988) minimum entrainment threshold which suppresses deep convection. Increasing this threshold enhances the tropical intraseasonal variability in the model and produces a more coherent MJO as well as a drier and colder mean climate in the model. The Gross Moist Stability (GMS; see Raymond et al. 2009) was also reduced which may be responsible for allowing the model to build up the large-scale moisture anomalies associated with the MJO. Further analysis showed that changes to the time mean GMS is not a reliable metric for diagnosing the model's ability to simulate a realistic MJO. This is because further CAM simulations which used an alternative method to enhance the MJO did not exhibit this change to the mean GMS. It appears that looking at the intraseasonal fluctuations of GMS provides a better diagnostic for assessing a model's ability to sustain MJO variability.


Undergraduate Work

Internal Rays of the Mandelbrot Set

My undergraduate thesis focused on mapping the internal structure of the Mandelbrot set by projecting a unit disc and the associated internal rays onto the various cardiod and circular bulbs of the Mandelbrot set. The points within these bulbs are associated with a specific period of attracting cycle for a certain connected Julia set defined by some hyperbolic polynomial. I was able to find a relationship between the period of a given bulb and the period of an attached bulb based on the angle of the internal ray which projects onto the connection point. None of this is particularly useful, but it was an interesting project that I really enjoyed working on with my advisor Dave Brown.

SOSUS Data Acquisition System

I did a few internships during my undergraduate days at the Hatfield Marine Science Center with Bob Dziak's Geo-Acoustics group. The first summer I was there I developed software to record acoustic data from the SOSUS hydrophone array which is operating at the Whidbey Island naval base in Puget Sound.

QUEphone: Autonomous Acoustic Profiler

The second summer at HMSC I was able to work on another hydrophone project called the Quasi-Eulerian Hydrophone (QUEphone). The QUEphone is an ARGO float with a hydrophone. This device can control its own buoyancy so that it can move up and down in the water column, which allows near real-time monitoring of acoustic events. Most of the time the float sits on the ocean floor and listens for seismic events. If a significant event occurs the float can pop up to the surface and communicate to the land station via satellite. This has many applications including early tsunami warning, but also offers a cheap alternative to acoustic monitoring with a moored hydrophone array which requires a ship to retrieve the data. When the QUEphone is ascending/descending it gets pushed around by the ocean currents so it can't be as accurate for locating the source of seismic events as a moored hydrophone array, which is why it's called Quasi-Eulerian.