Mechanisms of Solar Influence on the Troposphere via the Stratosphere

 

Author:  David Rind
Affiliation: NASA/GISS

 

We use various climate change experiments simulations from the GISS global climate/middle atmosphere model to investigate the impact stratospheric perturbations have on the troposphere with emphasis on solar forcing. Experiments include changes in CO2 and total solar irradiance, alterations in the stratospheric concentration of ozone and water vapor and volcanic aerosols, and solar UV changes in conjunction with a forced quasi-biennial oscillation.  Experiments are run both with and without allowing the sea surface temperatures to change, to isolate the stratosphere’s impact on tropospheric sea surface temperature responses from the direct effect of stratospheric changes. Atmospheric radiation, advection, stability influences and wave-mean flow interactions allow the stratospheric changes to be felt at lower levels.  Changes in stratospheric zonal winds can affect planetary wave propagation extending down into the troposphere, and hence the phase of the Arctic/North Atlantic oscillations. Changes in stratospheric temperatures can also affect temperatures in the upper troposphere, with a corresponding influence on tropospheric eddy energy generation and Hadley Cell intensity. Stratospheric radiative perturbations in general have a smaller impact on surface temperature than those of well-mixed or direct surface forcing, due to the cloud cover response. The magnitude of the tropospheric response is generally on the order of 0-10% of control run values, while some local/extreme effects can be higher.