Speaker
Description
At polar latitudes small changes in cloud amount, temperature and pressures correlate with changes in the solar wind electric field. These changes occur on a timescale of days, and in the absence of significant changes in in-situ ion production. They can be understood as resulting from changes in the ionosphere-earth current density, JZ, in the global electric circuit modulating space charge and cloud microphysical processes as it flows through stratiform clouds with low aerosol concentration. We hypothesize that other small changes in day-to-day and decadal cloud cover and storm vorticity at middle and high geomagnetic latitude, that correlate with JZ changes which are due to solar proton events, energetic electron precipitation, and galactic cosmic ray changes, can also be understood in the same way. This is a reinterpretation of the previous explanation of cosmic ray – cloud correlations. Observational evidence for the correlations, and for the theory for the relevant microphysical processes in clean remote mid-high latitude marine air are reviewed. The accumulation of space charge in the form of concentrations of negative ions just below cloud bases provides a favorable environment for ultrafine aerosol particles to become charged and grow, resulting in enhanced concentrations of cloud condensation nuclei (CCN). After days of processing, the CCN transported up into the cloud shift the droplet size distributions to smaller sizes and reduce precipitation. These cloud changes also affect vorticity of winter cyclones and the blocking of circulation at mid-latitudes. The tropospheric dynamical responses are in conjunction with stratospheric dynamical changes due to other solar and terrestrial inputs.