On the theoretical model for vertical ozone density distributions in the mesosphere and upper stratosphere

Diurnal variations in the vertical ozone density distribution have been calculated for the height range 40-150 km by extending our existing computer programs. The steady-state profiles were first calculated for fifteen constituents in the original program and three additional constituents (CH₄, CO and CO₂); the result was used as the initial condition for the time-dependent solution. The profile of the eddy diffusion coefficient used in this study was determined by comparing the model profile with the observations for CH₄, whose density distribution is verysenstive to the eddy diffusion coefficient The effects of hydrogen and nitrogen compounds on the ozone density are discussed somewhat quantitatively; they reduce the ozone density mainly in the mesosphere and stratosphere, respectively. Special attention is given to the large depression of the ozone density at around 70-85 km, which has been obtained in many theoretical models but has neither been explained nor definitely confirmed by observations. Our time-dependent model indicates that the depression develops at night by the effect of hydrogen-oxygen and nitrogen-oxygen reactions and of eddy diffusion transports. The latter effect also produces an increase of the ozone density after midnight at some heights in the depression region.