The Influence of Atmospheric Cloud Radiative Effects on the Large-Scale Stratospheric Circulation
Journal of Climate
2 Previous studies have explored the influence of atmospheric cloud radiative effects (ACRE) on the tropospheric circulation. Here the authors explore the influence of ACRE on the stratospheric circulation. The response of the stratospheric circulation to ACRE is assessed by comparing simulations run with and without ACRE under the auspices of the Clouds On-Off Klimate Intercomparsion Experiment (COOKIE). The stratospheric circulation response to ACRE is reproducible in a range of different
... ge of different GCMs, and can be interpreted in the context of two components: a dynamically-driven component and a radiatively-driven component. The dynamic component is linked to changes in the vertical flux of wave activity into the lower stratosphere and meridional wave propagation within the stratosphere. The changes in the vertical wave flux are consistent with the attendant changes in tropospheric baroclinicity and thus the amplitude of midlatitude baroclinic eddies. They account for a strengthening of the Brewer-Dobson circulation, warming in the upper polar stratosphere juxtaposed against cooling in the tropical lower stratosphere, weakening of the polar vortex, and a reduction in static stability near the tropical tropopause transition layer. The changes in meridional wave propagation account for much of the meridional structure of the stratospheric response. The radiative component is linked to changes in the flux of longwave radiation into the lower stratosphere. The changes in radiative fluxes lead to cooling of the extratropical lower stratosphere, changes in the static stability and cloud fraction near the extratropical tropopause, and a shortening of the timescales of extratropical stratospheric variability. The results highlight a previously overlooked pathway through which tropospheric climate influences the stratosphere.