The Interaction of Ozone Photochemistry and Dynamics in the Stratosphere. A Three-dimensional Atmospheric Model

Abstract

In the stratosphere the relaxation times for transport and ozone photochemistry in an oxygen–hydrogen–nitrogen system are approximately comparable. Therefore, realistic models used to calculate ozone variations need to be based on the interaction of the photochemistry and dynamics in this region.The model used in the present study is the three-dimensional global circulation model developed at the National Center for Atmospheric Research. The photochemical calculations for ozone are carried out as time dependent in a three-dimensional O–H–N system.The dynamic model is started from an atmosphere initially at rest and then spun up to a steady state circulation corresponding to mid-January. An initial observed ozone distribution is added and the model is then run through 30 simulated days. Analysis of the time variation of the ozone distribution shows that photochemistry dominates the ozone changes in the sub-solar middle stratosphere, and transport processes redistribute the ozone poleward and downward into the troposphere. Although the general pattern of ozone changes seem to be correct, the model produces too much ozone in the Southern hemisphere subtropical stratosphere and transports too much ozone into the Northern subtropical troposphere. The computed lower boundary flux of about 5 × 10¹⁰ cm⁻² s⁻¹ corresponds quite well to estimates given in the literature.