A two‐dimensional model of stratospheric chemistry and transport

Abstract

A two‐dimensional chemical model of the atmosphere is described. The model includes the major features associated with advanced one‐dimensional models: 30 active chemical species and all the important chemical reactions connecting them, diurnal effects, and Rayleigh scattering. The species are transported and calculated separately, with the exception of the odd oxygen family [O3, O(3P), O(1D)] and H and N atoms. The transport scheme contains both diffusive and advective terms, with the advective circulation field of Murgatroyd and Singleton (appropriately scaled) used to approximate the Lagrangian mean flow. Comparison of the model predictions with atmospheric observations of long‐lived trace species such as O3, N2O, CF2Cl2, CFCl3, and CH4 suggests that the transport parameterization gives a good representation of actual trace species motions. For constituents which are more active or whose chemistry is less well known, the model is a useful diagnostic tool for assessing our current understanding of atmospheric chemistry. A number of significant discrepancies between experiment and theory are highlighted, the most important being in the Clx and NOy families.

On the distributions of long‐lived tracers and chlorine species in the middle atmosphere

“…We shall address this point in more detail below. The total HC1 column implied by this distribution is controlled mostly by the HC1 below 35 km and increases with latitude in both hemispheres, in agreement with the observations by Mankin and Coffey [1983] and the model of Miller et al [1981]. Figure 13 shows the calculated distributions of CIONO 2 and HOC1.…”

A numerical model of the zonally averaged dynamical and chemical structure of the middle atmosphere

“…To remedy the deficiencies of one-dimensional models, a number of two-dimensional, zonally averaged models have been constructed [e.g., Rao-Vupputuri, 1973;Crutzen, 1975;Miller et al, 1981] that include the effects of specified mean meridional and eddy motions on the distribution of trace constituents. Other two-dimensional models [e.g., Pyle, 1975, 1977;Vupputuri, 1979] take into account the role of ozone as adiabatic heating source in the stratosphere and calculate simultaneously the mean meridional circulation forced by the ozone heating.…”

“…Thus it appears that an effective mechanism exists which either removes NOx altogether or converts it to some species other than HNO3 at high latitudes in the lower stratosphere in winter. In the model ofMiller et al [1981], a feature resembling the cliff is produced at the gridpoint located at 64 ø latitude. This is likely a result of conversion of NO2 to N205, which is not included in our model.…”

Diurnal variations of minor constituents in the stratosphere modeled as a function of latitude and season

“…Above the crossover point, within the altitude range between about 26 and 34 km, the model predicts values that are about 20% higher than the observed ozone partial pressures. (The overestimation of ozone in this region is common to other models [e.g.,Miller et al, 1981].) The discrepancy at these heights would be reduced somewhat by the inclusion of the natural chlorine cycle.…”