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X. Zhu (The Johns Hopkins University Applied Physics Laboratory)
A comprehensive two-dimensional (2D) model for Titan's stratosphere that couples radiation and dynamics is being developed to provide consistent constraints on the thermal and dynamical structure of Titan's stratospheric circulation. Detailed calculations of radiative heating and cooling rates by the correlated-k distribution method based on the escape function approach suggest a very low net radiative heating rate in the most part of the stratosphere. The weak radiative cooling rate in the stratosphere also yields a great radiative relaxation time. The following two immediate implications of the weak radiative heating and cooling rates will be discussed based on preliminary model results: (1) a special scheme with little numerical dissipation is needed in order to accurately simulate stratospheric circulation that has very weak external thermal forcing; (2) an alternative physical mechanism for the observed stratospheric temperature asymmetry in the vernal season should be explored. The dynamical module of the JHU 2D model adopts an approach that solves the energy and zonal momentum equations by Prather's nondiffusive advection scheme, conserving the second-order moments. The design rationale and preliminary results from the 2D model of the stratospheric thermal structure and circulation will be presented.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.