Comprehensive Modeling of Dynamics and Chemistry in the Middle Atmosphere

The period since the late 1970s has witnessed a revolution in the scientific understanding of how dynamics and chemistry interact, through transport and radiative heating, to produce the observed distributions of chemical species in the middle atmosphere. This revolution was facilitated by major advances on three fronts: The ability to monitor the middle atmosphere globally from satellite-borne instruments; the increasing capability of computational systems; and the development of new theoretical frameworks that facilitate the interpretation of observations and models. The discovery of the Antarctic ozone hole, and its subsequent explanation by Susan Solomon and colleagues, is a salient example of our greatly expanded capability to monitor and explain quantitatively the behavior of the middle atmosphere. Antarctic ozone loss has been shown to affect circulation and temperature trends locally and remotely; as documented by Susan and others, a striking reversal of these trends is taking place as the burden of ozone destroying substances (ODS) is reduced following the adoption of the Montreal Protocol. Other major advances made during this period and reviewed here include a thorough understanding of the role of atmospheric waves in driving the general circulation; the effect of increasing greenhouse gases (GHG) on temperature trends in the middle atmosphere; the role of ODS and GHG in altering the Brewer Dobson circulation; and the role of the quasi-biennial oscillation and ENSO in modulating transport in the middle atmosphere.