Evening data of two atmospheric electric parameters (positive air conductivity and potential gradient) measured at Świder (Poland) between 1965 and 1995 have been investigated around days with low number of condensation nuclei (NCN). Based on the measure of the NCN decrease, two groups of days were distinguished, (days with moderate decrease: from −30 % to −50 % and days with strong decrease: below −50 %, as related to the corresponding monthly average of the NCN). These days have been applied as key days for two independent superposed epoch analyses.
Air conductivity significantly increased both on days with moderate and strong NCN decreases. For the strong events the conductivity increase was about the double of that found for the moderate ones. In accordance with Ohm’s Law, the potential gradient showed its lowest value (in relation to the corresponding monthly average) on these key days. The response of this atmospheric electric parameter is also significant, however, it is less impressive than in the case of air conductivity.
For checking the influence of meteorological changes on atmospheric electric parameters, the departures of air conductivity and potential gradient from corresponding monthly average have been tabulated according to the observed wind speed and wind direction, both for moderate and strong NCN events. Air conductivity generally showed a distinct increase with increasing wind speed in the case of both kinds of NCN events. A dependence on wind direction was also found. The potential gradient responded in a proper sense to wind changes, even if the responses were less convincing than those of air conductivity.