Numerical Simulation of Ozone Production, Transport and Distribution with a Global Atmospheric General Circulation Model

Abstract

The production, transport and distribution of ozone are simulated for a January with a global atmospheric general circulation model. In this model the ozone influences the radiational heating as well as the photochemical ozone production and destruction, the radiational heating influences the atmospheric circulation, and the circulation redistributes the ozone. The model has fairly successfully simulated the synoptic and time-averaged observed large-scale fields of temperature, mass, and velocity in the troposphere and stratosphere, although there are some deficiencies. In particular, the simulated temperatures are too cold in the lower and middle stratosphere in the polar regions, the sea level pressure is too high in the Arctic and in the Antarctic circumpolar trough, and the flow field in the middle-latitude troposphere does not show the observed wavenumber 3. Despite these shortcomings, the model has simulated the observed high correlation of synoptic and time-averaged total ozone with the tropospheric height field in middle latitudes, with the ozone maxima and minima, respectively, located at the troughs and ridges of the tropospheric waves. The deficiencies which are seen in the time-averaged O3 distribution are attributable to recognized deficiencies of the general circulation model. In the tropics there is a vertically integrated transport of 03, from the summer to the winter hemisphere which is almost entirely produced by the mean-meridional circulation. In the middle latitudes, in both hemispheres, 03 is transported toward the equator by the mean-meridional circulation and toward the poles by the zonal eddies; but the eddy transport dominates, so that the net 03, transport is poleward. In the high latitudes in both hemispheres, there is a reversal in the directions of the two components of the 03, transport; but here the transport by the mean-meridional circulation dominates, so that the net transport continues to be poleward. In the individual latitudes, the zonally integrated vertical transport of ozone is dominated by the transport by the mean-meridional circulation; but integrated over the globe, the vertical O3 transport is dominated by the eddy transport. Between 20 and 31 km elevation, the globally integrated vertical 03, transport is a countergradient transport with respect to the globally integrated 03, mixing ratio. The divergence of the 03 transport maintains the ozone below its photochemical equilibrium concentration in the tropics and subtropics, and the convergence of the 03 transport maintains the ozone above its photochemical equilibrium concentration in the middle and high latitudes of both hemispheres. In this way, both the atmospheric motions and the 03 photochemistry determine the 03, sources and sinks. The globally integrated photochemical production of ozone exhibits variations with periods of a day and less. These high-frequency oscillations are due to the quasi-stationary longitudinal variation in the ozone that is produced by the 03 transports.