An interactive chemical dynamical radiative two-dimensional model of the middle atmosphere
Résumé
This paper describes a new two-dimensional model of the stratosphere and the mesosphere in which dynamics, radiation and chemistry axe treated interactively. The transport equations axe expressed in the transformed Eulerian fraxnework. Momentum deposition associated with Rossby wave absorption and gravity wave breaking and related eddy diffusion coefficients are paxaxneterized as a function of the mean zonal state of the atmosphere. Diabatic heating and cooling is derived from the detailed National Center for Atmospheric Reseaxch community climate model radiative code. The distributions of chemically active species belonging to the oxygen, hydrogen, nitrogen and chlorine families axe calculated for present-day conditions. By applying neax the tropopause a different dynamical forcing in each hemisphere, the model produces significant hemispheric asymmetries in dynamical quantities (e.g., temperature) and trace gas densities (e.g., column ozone), in good agreement with climatological values. It is shown that the calculated distributions of source gases, such as nitrous oxide and methane, axe very sensitive to the calculated (and pararneterized) dynamical quantities and that species produced in the atmosphere, like carbon monoxide and odd nitrogen, can provide interesting information on the role of atmospheric transport. A major problem that remains to be elucidated is the underestimation by most models of the ozone density in the upper stratosphere. Because of the many feedback mechaaftsms included in its formulation, the model is well adapted to study the effects of human or natural perturbations. The response of the atmosphere to perturbations resulting from increasing emissions of CO2 and chlorofluorocaxbons is considered.
Domaines
Planète et Univers [physics]
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