Polar Cloud Opacity and Surface Pressure Responses to Atmospheric Electricity from Global Circuit and Solar Wind Sources: Electrical Modulation of Aerosol Scavenging Rates?

An analysis of downwelling longwave IR irradiance at the South Pole shows a statistically significant cloud opacity responses to (1) measured vertical electric fields, associated with ionospheric potential changes due to global thunderstorms and shower cloud electrification and (2) the geomagnetic Ap index, a measure of ionospheric potential changes near the South Pole during magnetic storms. There is also a response to (3) the solar wind (IMF By) magnetic field, another measure of ionospheric potential changes in the polar regions. The ionospheric potential changes determine the ionosphere-earth current density that flows downwards through clouds and deposits change on droplets and aerosol particles, so the correlations point to a process, such as electro-anti-scavenging, that can decrease the losses of ultrafine aerosol particles while they grow to condensation nuclei size. At the South Pole orographic clouds form as air flows into, and rises over, the Antarctic Plateau. The aerosol concentration is very low, and other observations have shown that this increases the sensitivity of the opacity of the clouds to changes in condensation nuclei concentration. Similar correlations have been found for clouds formed over the Greenland ice dome, and for responses of surface pressure in the Antarctic and Arctic to the same inputs.