Electrical signatures of Nimbostratus and Stratus clouds in ground-level vertical atmospheric electric field and current density at mid-latitude station Swider, Poland

We analyse the occurrences of low-level stratiform clouds such as Nimbostratus and Stratus, in Swider, Poland (51.15 N, 21.23 E) in the years 2005-2015. There have been on average 44 days with Nimbostratus a year between 2005 and 2015 at Swider and 51 days with Stratus over this period. Atmospheric electric field, current density and air conductivity available for the recorded cloud cases from years 2012-2015 have been analysed and their average values obtained for all cases and separately for the cloud cases with their main types of precipitation: rain and snow for Nimbostratus, drizzle and granular snow for Stratus. The analysis of atmospheric electricity parameters confirms previous results indicating differences in the electrical behaviour of raining and snowing clouds. The atmospheric electric field and conduction current is more likely downward under Stratus cloud as is its precipitation-convection current. This type of cloud mostly behaves like a passive element of the global circuit. The electric field under Nimbostratus during rain at the ground is upward and upward precipitation current occurs during heavier rain. Such raining mid-latitude Nimbostratus can potentially be an electric cloud generator which charges the Earth's global atmospheric circuit, the contribution of which needs to be investigated in more detail.