Diagnosis of Dynamics and Energy Balance in the Mesosphere and Lower Thermosphere

Abstract

A diagnostic technique has been developed to consistently derive all the dynamical and chemical tracer fields based on one or a few well-measured fields such as temperature and ozone distributions. The technique is based on the new Johns Hopkins University/Applied Physics Laboratory (JHU/APL) globally balanced 2D diagnostic model that couples the dynamics with photochemistry. This model is especially useful for studying the mesosphere and lower thermosphere where dynamics, radiation, and photochemistry strongly interact. The novelty of the diagnostic model is to derive the wave drag and eddy diffusion coefficient directly from the better-defined thermal forcing with its major contributions derived from the zonal mean components. The latter is also affected by the advective and diffusive transports. The derived tracer distributions together with input field(s) provide the necessary radiative and chemical heating rates for the calculation of the thermal forcing. Two numerical experiments with different input fields are conducted with the JHU/APL 2D diagnostic model. Using the COSPAR International Reference Atmosphere 1986 model atmosphere as the input temperature field, the first experiment produces a meridional velocity of ?10 m s?1 and a peak ozone mixing ratio of ?2 ppmv near the mesopause. The second experiment incorporates additional ozone information obtained from the High Resolution Doppler Imager (HRDI) measurements as part of the input fields. Monthly zonal mean HRDI ozone (?4?8 ppmv near the mesopause) is merged with the lower values of model climatology using statistical scaling. In this second experiment, the diagnostic model produces the enhancements in radiative and chemical heating, wave drag, residual circulation, and eddy diffusion coefficient that are necessary to maintain the high input ozone concentration near the mesopause.