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T.E. Dowling, R. Morales-Juberías, Cs.J. Palotai (CPL/U. Louisville)
We have completed the design and implementation of a hybrid vertical coordinate, \zeta, for the EPIC atmospheric model that is strongly coupled to the potential temperature, \theta, for most of the model but smoothly transitions into a pressure-based coordinate that follows the geopotential at the bottom of the model. This allows the coordinate to be terrain-following for terrestrial planets, to be extended deeply into the neutrally stable interiors of gas giants, and to be well-defined in convectively unstable regions. In most such hybrid models, the isentropic variable, \theta, is treated as a prognostic variable throughout the model. We have increased the efficiency and accuracy of the hybrid approach by treating \theta in a novel way. In the top region, \theta is simply the vertical coordinate, \theta = \zeta. We generally position the bottom of this region to be the tropopause, such that the stratosphere and regions above gain the full advantages of isentropic coordinates. In the middle region, \theta is treated as a diagnostic variable by inverting the relationship \zeta = F(\theta,p) that is used to define the vertical coordinate such that it is smooth and monotonic. The potential temperature may be determined accurately this way until \zeta and \theta cease to be strongly coupled, at which point the bottom region begins and \theta is predicted as a full prognostic variable. We will present applications that include a Venus model with topography, the standard Held-Suarez benchmark for Earth, and selected gas-giant examples to demonstrate the flexibility of the model. The development of a planetary boundary layer (PBL) scheme and a cloud microphysics scheme for the EPIC model are discussed in related papers.
This work is sponsored by the NASA Planetary Atmospheres and EPSCoR Program
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The author(s) of this abstract have provided an email address for comments about the abstract: dowling@louisville.edu
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.