A 2-D model calculation of atmospheric lifetimes for N2O, CFC-11 and CFC-12

Abstract

Accurate values for the atmospheric lifetimes of N2O, CFC13 (CFC-11) and CF2C12 (CFC-12) are vital1–3 for studies of their life cycles and in attempts to forecast their future atmospheric levels. These gases are known to be removed mainly by stratospheric photolysis. The lifetimes set by these removal processes are usually inferred from one-dimensional (1-D) models. Using a two-dimensional (2-D) zonal-mean model together with recent observations, we argue here that the stratospheric removal rates may also depend on certain latitudinal features, including latitudinal variations of the gas concentrations, photolysis rates and their correlations, features that cannot be included in the 1-D models. Our discussion also considers the validation of 1-D model results, particularly regarding predictions of atmospheric lifetimes.