First results from a new type of photochemical model are presented. The model has an Eulerian grid with latitude and longitude coordinates on a single isentropic surface, which in this work is specified at a potential temperature of 846.6 K. The photolysis rates in the model are determined using a specified distribution of the total ozone column above the surface. The model contains 107 reactions and 40 species whose concentrations are solved for explicitly with an algorithm that fully accounts for diurnal variations. Species are advected implicitly using a semi-Lagrangian technique in which 12 hour air particle trajectories are computed and then the particles are reinitialized back onto the Eulerian grid. The photochemical model is integrated for 12 days with winds and temperatures supplied from a three-dimensional model integration of an idealized wavenumber one disturbance. The results for the long-lived model tracers such as N2O show excellent correlation with the potential vorticity distribution, providing confidence in the transport scheme. The distribution of the tracers and the nighttime distribution of the reservoir species show the effect of the wave disturbance in enhancing gradients at the edge of the vortex region and in low to mid-latitudes where a tongue of low potential vorticity air is advected.

The effect of the photochemistry is to produce ringed structures surrounding the vortex in reservoir species such as HNO3 and ClONO2. For the radical species, the differences in the steepness of the gradients at the nighttime terminator and the daytime terminator are clearly apparent. Steep high-latitude gradients in NO2 (the Noxon cliff) are also seen in the results. The results demonstrate the highly complex nature of the photochemistry resulting from the movement in the dynamical vortex and its interaction with the diurnal variation near the terminator. The model provides an interesting way of viewing the full complexity of the photo-chemistry in the presence of large-scale advection. Calculations with zonally averaged wind and temperature fields reveal discrepancies in the calculation of the zonal mean of less than 10% for O3 and HNO3 compared with the zonal mean of the previous results. However, the discrepancies for NO2 and N2O5 were much larger, especially in high latitudes. This suggests the need to exercise caution in the interpretation of the results of some species calculated by latitude-height models. ¿ American Geophysical Union 1990