Modeling of chemistry and chemistry-radiation coupling processes for the middle atmosphere and a numerical experiment on CO2 doubling with a 1-D coupled model

A family method chemical scheme, and a chemistry-radiation coupling scheme for the middle atmosphere, have been developed. These schemes are also applicable to a future atmosphere where concentrations of greenhouse gases and halogen gases will be different from the present atmosphere. A one-dimensional, chemically radiatively coupled model has been constructed to test the scheme. A method of photolysis rate calculation flexible enough for any radiation calculation scheme on plane-parallel atmosphere, a definition of globally averaged solar zenith angles for the 1-D model, and development of a chemical scheme to which heterogeneous reactions on aerosols or Polar Stratospheric Clouds are easy to incorporate are presented. The model includes 163 gas phase chemical reactions of oxygen, hydrogen, nitrogen, hydrocarbon, chlorine, and bromine species for the stratosphere. Although heterogeneous reactions are not considered in this paper, the schemes are flexible for including these reactions. Vertical profiles of concentrations and photolysis rates of chemical constituents at a steady state of the model, and the temperature profile are presented and discussed. Comparison of these profiles with reference profiles in JPL-97, shows that they were successfully calculated by this scheme in the model. Numerical experiments on CO2 doubling with the 1-D model shows that total ozone variation after CO2 doubling is different between the coupled model, and in a fixed photolysis rate model. Mechanism of the slow, extended variation of total ozone in the coupled model is discussed. It is shown that reduction in solar radiation penetration into the atmosphere by O-3 increase due to the CO2 doubling, made considerable effects on chemical constituent concentrations in the lower stratosphere.