Effects of Planetary Wave-Induced Ozone Heating on “Downward Control”: Implications for Climate Variability

The wave drag associated with the breaking and dissipation of vertically propagating planetary waves in the stratosphere has far-reaching consequences for the global circulation and climate. The planetary wave drag (PWD) exerts non-local control over the extratropical stratosphere that manifests as a wave-driven equator-to-pole meridional circulation. This wave-driven circulation - termed the Brewer-Dobson circulation or residual circulation - is largely responsible for large-scale troposphere-stratosphere mass exchange, departures of the stratosphere away from radiative equilibrium, and the transport of trace constituents from the tropics to the extratropics.

In this study we examine the effects of planetary wave induced ozone heating (OH) on the extratropical residual circulation using a mechanistic model that couples dynamics, radiation and the transport and photochemistry of stratospheric ozone. The wave-induced OH, which is effectively confined to the stratosphere, is shown to affect the residual circulation through changes in the planetary wave drag (PWD). The changes in PWD are due to photochemically accelerated cooling and wave-induced ozone transport, which combine to affect the troposphere via “downward control.” The change in “downward control” due to planetary wave-induced OH is shown to be a potentially important pathway for communicating natural and human-caused changes in stratospheric ozone to the troposphere. This result is discussed in light of observational and modeling data showing a connection between changes in stratospheric ozone and climate variability.