Solar variability and the lower atmosphere.
Abstract Mechanisms possibly connecting solar activity to meteorology of the lower atmosphere are reviewed. Besides direct variations of solar visible emission, solar-related fluctuations in some aspect of cloudiness could be important. Any such variations in cloudiness are likely to be related to variations in production of ionization near the tropopause by galactic cosmic rays, the only geophysical phenomena unconnected with upper atmospheric processes known to have a striking (negative) correlation with solar activity. Such a connection might involve a dependence of sulfate aerosol formation on ionization and in turn a dependence of cloud radiative properties on variations of the aerosol particles' action as cloud condensation nuclei.