Effect of computed horizontal diffusion coefficients on two‐dimensional N₂O model distributions

The sensitivity of the N 2 O distribution in our two‐dimensional photochemical model to horizontal diffusion coefficients (both K yy and K yz values) has been explored. The residual circulation was computed using temperature data from the National Meteorological Center (NMC) and heating rates from Rosenfield et al. (1987). The K yy and K yz values were computed from these same data using quasigeostrophic potential vorticity. For comparison we also computed self‐consistent K yy values from our residual circulation. The use of either set of these diffusion coefficients produced substantial changes in the N 2 O distribution, especially in the middle to upper stratosphere and at high latitudes in the winter. In general, the changes lead to an enhanced transport of N 2 O to higher latitudes with the set of self‐consistent K yy values transporting the greatest amount of N 2 O. The enhanced transport increases the lifetime of N 2 O because the photochemical lifetime is larger at high latitudes.