REFRACTION AND ATMOSPHERIC PHOTOCHEMISTRY

A new model for calculating the effects of refraction is introduced. T his model was invented independently of the one described by DeMajistr e et al. [1995], but it is shown that the two models are analytically equivalent. However, the numerical implementation of the model introdu ced here is vastly more economical and efficient than that of the mode l by DeMajistre et al. This is because the two differential equations solved numerically by DeMajistre et al. have been which reduced them t o only one simple expression. The effects of refraction on stratospher ic chemistry calculated with this new model are shown to be greatest i n the polar lower stratosphere close to the onset and completion of po lar night. The main effect is to change the shape of the seasonal cycl e of reactive species produced by photolysis such as NO, NO2, OH, HO2, Cl, ClO, Br, and BrO during the onset and completion of polar night.