Variations in global cloud cover and the fair-weather vertical electric field

Statistically significant (at the 95% significance level) changes in daily cloud cover are found to occur globally over land coincident with extreme increases in ‘fair-weather’ measurements of vertical electric field (Ez) measured at Vostok, Antarctica. Using global cloud products from the International Satellite Cloud Climatology Project (ISCCP) D1 data series, superposed epoch analyses were made of both increases and decreases in Ez. Field significance testing revealed that, both before and after extreme increases in Ez, significant absolute cloud cover changes (of 13–15%) occur in the tropics and high latitudes. While the linkages in the tropics may reflect changes in the main convective cloud generators of current flow in the global circuit, the linkages at high latitudes appear to represent responses of clouds to the current flow. This linkage offers a possible explanation of a possible solar–terrestrial climate amplification mechanism.