THE INFLUENCE OF DYNAMICS ON 2-DIMENSIONAL MODEL RESULTS - SIMULATIONS OF C-14 AND STRATOSPHERIC AIRCRAFT NOX INJECTIONS

A two-dimensional (2D) photochemical model (latitude range from -85-degrees to +85-degrees and altitude range from the ground to 0.23 mbar (about 60 km)) has been used to investigate the influence of dynamics on model results. We tested three representations of atmospheric transport to simulate total ozone and C-14 amounts after nuclear tests in the early 1960s. We also simulated three scenarios of NOx injections from a proposed fleet of stratospheric aircraft and their effects on ozone. The three dynamical formulations used were Dynamics A, a base dynamics used in previous work with this model; Dynamics B, a strong circulation dynamics discussed by Jackman et al. [1989a]; and Dynamics C, the dynamics used by Shia et al. [1989]. The advective component of the stratosphere to troposphere mass exchange rate (advective strat/trop exchange rate (ASTER)) is largest for Dynamics B (5.8 x 10(17) kg yr-1) and smallest for Dynamics C (1.4 x 10(17) kg yr-1), with the ASTER for Dynamics A (2.4 x 10(17) kg yr-1) being between these two extremes. Simulations of both total ozone and C-14 were worst with Dynamics B. Simulations of total ozone were best with Dynamics A and for C-14 best with Dynamics C. This illustrates the difficulty of simultaneously modeling constituents with different altitude and latitude dependencies. Ozone depletion from NOx injections of stratospheric aircraft showed a strong sensitivity to dynamics. Generally, if eddy diffusion is not changed, then a large ASTER leads to reduced ozone loss while a small ASTER leads to increased ozone loss from a given stratospheric NOx injection.