Two-dimensional Atmospheric Flow Modeling by Using Schwarz-Christoffel Transformation Over Complex Topography PDF Download

Author: Hakan Erdun
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Languages : en
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Book Description
Local weather over complex topography is greatly influenced by the modification of flow by blocking and channeling. An understanding of these mesoscale mechanisms, through both modeling and field studies, should lead to greater forecasting skill in these regions. In addition, the dispersion of pollution from industry sited in valleys is often hampered by meteorological conditions resulting directly from orographically induced wind systems. In this study, the results of the atmospheric flow modeling over complex topography by using Schwarz-Christoffel transformation have been given. In most of the meteorological models, non-orthogonal grid system is used for the modeling of an atmospheric phenomenon over the complex topography. In using this kind of non-orthogonal grid system, the errors especially in the calculation of pressure gradient in the lower atmosphere increase where the slopes of topography were not much less than 45 degrees. Furthermore, in a non orthogonal system, transformation equations that are used in the model include extra terms according to an orthogonal system. Consequently, the computational time increases. We used here Schwarz-Christoffel transformation to eliminate the above problems. This kind of transformations is used to generate the orthogonal grid points over the topography that has any slopes and scales. The reason of using widely non-orthogonal systems (for example, terrain-following height coordinate system) by modelers is due to simplicity on writing the computer code. In this thesis, the two-dimensional atmospheric flow model over complex topography is developed. The model formulation is based on the shallow convection system and meso-b scale. The model includes the non-hydrostatic and the buoyancy terms in addition to geostrophic and Coriolis terms. For the turbulence model, Smagorinsky and Lilly's subgrid-scale mixing formulation is used. The model does not include radiative processes and PBL (Planetary Boundary Layer) parameterizations. In order to test the model, a Gaussian-shaped mountain within a domain having a width of 40 km and a height of 4 km. Domain has 50x21 grid-points. The horizontal grid interval is 810 m, and time step is taken to be 2.5 sec. According to model results, the flow field over the given topography has been modeled realistically in global meaning.