The Radiative-Dynamical Response of a Stratospheric-Tropospheric General Circulation Model to Changes in Ozone

J. T. Kiehl National Center for Atmospheric Research, Boulder, Colorado

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Byron A. Boville National Center for Atmospheric Research, Boulder, Colorado

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Abstract

A stratosphere-troposphere version of the NCAR Community Climate Model is used to study the radiative and dynamical response to imposed changes to the model ozone distribution for perpetual January conditions. The imposed changes include both uniform ozone reductions of 50, 15 and 100 percent and an ozone reduction scenario calculated from a two-dimensional chemical model. We compare the response of the general circulation model to a model that employs the fixed dynamical beating assumption proposed by Fels et al. We find that the uniform ozone reduction cases are not well modeled by assuming fixed dynamical heating. However, the model response to the ozone scenario is well modeled by the fixed dynamical heating model. A general result from these studies is that even for large ozone reductions (less then or equal to 75%), the Southern Hemisphere easterly jet is insensitive to ozone reductions. The Northern Hemisphere jet remains relatively constant for ozone reductions as large as 50 percent. For a 75 percent reduction in ozone the Northern Hemisphere jet is severely reduced. Thus for this model there appears to be a threshold in ozone reduction at which large changes in jet structure occur.

Abstract

A stratosphere-troposphere version of the NCAR Community Climate Model is used to study the radiative and dynamical response to imposed changes to the model ozone distribution for perpetual January conditions. The imposed changes include both uniform ozone reductions of 50, 15 and 100 percent and an ozone reduction scenario calculated from a two-dimensional chemical model. We compare the response of the general circulation model to a model that employs the fixed dynamical beating assumption proposed by Fels et al. We find that the uniform ozone reduction cases are not well modeled by assuming fixed dynamical heating. However, the model response to the ozone scenario is well modeled by the fixed dynamical heating model. A general result from these studies is that even for large ozone reductions (less then or equal to 75%), the Southern Hemisphere easterly jet is insensitive to ozone reductions. The Northern Hemisphere jet remains relatively constant for ozone reductions as large as 50 percent. For a 75 percent reduction in ozone the Northern Hemisphere jet is severely reduced. Thus for this model there appears to be a threshold in ozone reduction at which large changes in jet structure occur.

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