Numerical Experiments with a General Circulation Model Concerning the Distribution of Ozone in the Stratosphere

Abstract

Two experiments were performed with a nine-layer quasi-geostrophic spectral model to simulate the distribution of ozone below 60 km. Experiment I included thermal and orographic forcing of the planetary-scale waves while Experiment II did not include this forcing. Both experiments used a linear parameterization of ozone photochemistry. The two experiments were qualitatively similar but a high latitude winter ozone buildup was seen only in Experiment I. This buildup resulted from a Brewer-Dodson circulation forced by large-amplitude planetary-wale waves in the winter lower stratosphere. The model results also showed that photochemistry is important down to lower altitudes (20 km) in the summer stratosphere than was previously realized. An important photochemical discrepancy was noted between 22 and 30 km at low latitudes, where the model photochemical equilibrium mixing ratios were 25–40% larger than those inferred for the real stratosphere. This discrepancy may be due to insufficient NO₂ in the model and can be resolved by more accurate daytime NO₂ measurements.