Browsing by Subject "vorticity"
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Item A Climatology of the Arctic on Mid-Tropospheric Temperature Regulation(2014-06-24) Anthony, Jeremy PatrickThe Arctic is a unique and complex environment. Many factors play a role in determining the long-term climate of the Arctic, including mesoscale weather systems and many complex ice-albedo feedback mechanisms. Previous studies determined using real observations that although 500 hPa temperatures reach -45? by mid-November, temperatures very rarely drop below, despite a total loss of incoming solar radiation. This temperature value at 500 hPa follows moist-adiabatically to the surface value of approximately -2?, which is the freezing point of high-latitude sea water. Sea ice data was examined using satellite and model data to paint a picture of the environment during three distinct periods in history: the last glacial maximum (twenty-one thousand years ago), the mid-Holocene (six-thousand years ago), and the 20th century. Areal September minimum sea ice extent has reached record lows annually since 2007. Vertical temperature profiles created with CCSM4 model data during these three eras show the atmosphere becoming more moist-adiabatic at high latitudes over time. Saturation potential vorticity allows us to assess the convective environment, and it shows that the Arctic is becoming more tropical over time. Analysis of areal extent where temperatures fall below -45? at 500 hPa shows this to be an extremely rare occurrence, and temperatures never fall below -47.5?, except for very rare occurrences during the last glacial maximum. Transient eddy heat flux is increasing at higher latitudes, and the warm half of a cyclone contains convection (as seen in saturation potential vorticity). In this paper, we present several lines of evidence supporting a role for intermittent convection in maintaining mid-tropospheric temperatures across climate states of the past twenty-one thousand years.Item Art Directable Tornadoes(2011-08-08) Dwivedi, RavindraTornado simulations in the visual effects industry have always been an interesting problem. Developing tools to provide more control over such effects is an important and challenging task. Current methods to achieve these effects use either particle systems or fluid simulation. Particle systems give a lot of control over the simulation but do not take into account the fluid characteristics of tornadoes. The other method which involves fluid simulation models the fluid behavior accurately but does not give control over the simulation. In this thesis, a novel method to model tornado behavior is presented. A tool based on this method was also created. The method proposed in this thesis uses a hybrid approach that combines the flexibility of particle systems while producing interesting swirling motions inherent in the fluids. The main focus of the research is on providing easy-to-use controls for art directors to help them achieve the desired look of the simulation effectively. A variety of controls is provided which include the overall shape, path, rotation, debris, surface, swirling motion, and interaction with the environment. The implementation was done in Houdini, which is a 3D animation software whose node based system allows an algorithmic approach to the problem and integrates well with the current tools. The tool allows the user to create animations that reflect the visual characteristics of real tornadoes. The usefulness of the tool was evaluated among participants who had some experience in 3D animation software. The results from the simulation and evaluation feedback reveal that the tool successfully allowed the users to create tornadoes of their choice efficiently.