A Sensitivity Test of the Ozone Solar Cycle Response with Respect to Chemical Kinetics and Model Parameters

Previous studies have shown that the observed O3 solar cycle (SC) responses in upper and middle stratosphere are very different from those predicted by models. It is argued whether the differences are within the uncertainties of measurements and chemical kinetic rates. To answer this question, a simple one-dimensional (1-D) Caltech/JPL photochemical model is employed to study the discrepancies between observed and model O3 solar cycle responses. A simplified list of reactions is developed including Chapman, HOx, NOx and ClOx chemistry. We perform sensitivity tests on a significant portion of the kinetic rates to investigate whether the observed O3 SC response can be modeled using standard chemistry. Other model parameters such as eddy diffusivity are included in the tests. Finally, the optimal estimation method (OEM) is employed to derive a set of kinetic rate coefficients and model parameters that would minimize the difference between the observed and the model SC responses in O3. The outcome of retrieval represents the best-fit O3 response under the constraints of standard chemistry and measurement uncertainties.