A time dependent two-dimensional model has been used to study the behavior of nitrogen species in the atmosphere. The model employs a residual mean meridional circulation for the transport of photochemical species, and this transport yields large column abundances for NOx (N+NO+NO2+NO3+2¿N2O5+HNO4) at high latitudes, with the altitude of maximum density occurring in the lower stratosphere. New temperature dependent absorption cross sections are employed for N2O5. It is shown that this photochemical-dynamical formulation results in the conversion of most of the stratospheric NOx to N2O5 at high latitudes in winter, yielding low NO2 column abundances there, in agreement with observations. Calculated seasonal and diurnal variations in NO2 are also shown to be comparable to observations, even at high latitudes. The effects of departures from zonally symmetric flow on NO2 abundance are examined and found to be consistent with observations.