Turbulent dispersion of aircraft exhausts in regions of breaking gravity waves

This study describes the three-dimensional dispersion of aircraft exhausts released into regions of overturning and breaking gravity waves below a critical level. The principal concept is to estimate effective diffusivities of a passive scalar by combining previous numerical approaches to the plume dispersion in the free atmosphere and to the breakdown of internal gravity waves at those altitudes. Here, it could be shown that the possible high vertical diffusivity of 6 m(2) s(-1) contributes considerably to an efficient vertical mixing of aircraft exhausts or other species, e.g. trace gases. The effective Vertical diffusion coefficient of the entire breaking event is calculated to be D-v(eff) approximate to 0.5 m(2) s(-1). (C) 1998 Elsevier Science Ltd. All rights reserved.