A variable resolution global spectral model
A conformal transformation suggested by F. Schimdt is followed to implement a global spectral model with variable horizontal resolution. A conformal mapping is defined between the real physical sphere (Earth) to a transformed (Computational) sphere. The model equations are discretized on the computa...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://purl.flvc.org/fsu/lib/digcoll/etd/3088546 http://fsu.digital.flvc.org/islandora/object/fsu%3A77348/datastream/TN/view/A%20variable%20resolution%20global%20spectral%20model.jpg |
| Summary: | A conformal transformation suggested by F. Schimdt is followed to implement a global spectral model with variable horizontal resolution. A conformal mapping is defined between the real physical sphere (Earth) to a transformed (Computational) sphere. The model equations are discretized on the computational sphere and the conventional spectral technique is applied to solve the model equations. There are two types of transformations used in the present study, namely, the Stretching transformation and the Rotation of the horizontal grid points. Application of the stretching transformation results in finer resolution along the meridional direction. The stretching is controlled by a parameter C. The rotation transformation can be used to relocate the North Pole of the model to any point on the geographic sphere. The idea is now to rotate the pole to the area of interest and refine the resolution around the new pole by applying the stretching transformation. The stretching transformation can be applied alone without the rotation. A T-42 Spectral Shallow-Water model is transformed by applying the stretching transformation alone as well as the two transformations together. A T-42 conventional Spectral Shallow-Water model is run as the control experiment and a conventional T-85 Spectral Shallow-Water model run is treated as the benchmark (Truth) solution. RMS error analysis for the geopotential field as well as the wind field is performed to evaluate the forecast made by the transformed model. It is observed that the RMS error of the transformed model is lower than that of the control run in a latitude band, for the case of stretching transformation alone, while for the total transformation (rotation followed by stretching), similar results are obtained for a rectangular domain. A multi-level global spectral model is designed from the current FSU global spectral model in order to implement the conformal transformation. The transformed T-85 model is used to study Hurricane Andrew. The control experiment in this study is a conventional T-170 spectral model. The performance of transformed model is clearly seen to be improved in describing the structure, intensity and motion of Hurricane Andrew, over the conventional FSU global spectral model. Source: Dissertation Abstracts International, Volume: 56-01, Section: B, page: 0295. Major Professor: T. N. Krishnamurti. Thesis (Ph.D.)--The Florida State University, 1994. |
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