Aeronomy of the Earth's Atmosphere and Ionosphere

Volume 2 of the series IAGA Special Sopron Book Series pp 3-17


Chemical–Dynamical Coupling in the Mesosphere and Lower Thermosphere

  • Daniel R. MarshAffiliated withAtmospheric Chemistry Division, National Center for Atmospheric Research Email author 

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A chemistry climate model is used to illustrate several ways in which dynamics and chemistry are coupled in the mesosphere and lower thermosphere (50–120 km in altitude). First the mean chemical state of the modeled atmosphere is presented, including the distribution of key radiatively-active species that determine heating and cooling rates. This is followed by a description of the major dynamical modes of variability resolved by the model, which span timescales from hours to seasons, and includes the mean meridional circulation, the upper atmospheric response to a sudden stratospheric warming, and upward propagating tidal modes. It is demonstrated that all these have significant effects on composition, either through advection, or by the temperature and pressure dependence of chemical reaction rates. For those constituents modified by dynamics that play a role in the energy budget, the potential for a feedback on the dynamics exists.