Increases in current density result in greater accumulation of electrostatic charge on aerosols and supercooled water droplets at the tops of clouds. Theoretical models and laboratory measurements indicate this will increase the rate of initial ice nucleation, leading to observed changes in winter cyclone intensity and in general circulation. The PIs will first clarify and quantify changes in the global electric circuit in response to changes in the solar wind. This will provide a basis for more quantitative models of electrostatic charge effects on cloud microphysics. Second, they will test their prediction of the return of the Wilcox effect for the winters of 1992-94, when stratospheric aerosol loading was increased by Pinatubo, and there was modulation of relativistic electron precipitation at sector boundaries. Finally, the PIs will test the southern hemisphere meteorological data sets for responses to Forbush decreases and sector boundary crossings.***
