A study of the effects of hail, snow and PM on Potential Gradient

We present here the study of six hail events and five snow events in Xanthi, N. Greece, on Potential Gradient (PG). All hail events occurred in the spring-summer season of the years 2011-2018. A decrease in PG has been observed which has been around 2000-3000 V/m during the three hail events which occurred concurrently with rain. In three events with no rain, the decrease has been varying between 60 and 6000 V/m. In the case of only 60 V/m drop, no concurrent drop in temperature has been observed, while for the other cases it appears that for each degree drop in temperature the drop in PG is 1000 V/m, hence it appears that the intensity of the hail event regulates the drop in PG, although we do not have hail amount measurements to validate this. Regarding snow events,  the situation is more complicated, with PG fluctuating rapidly between high positive and high negative values. We present also a preliminary study of the impact of PM1.0 and PM2.5 on PG from measurements performed during 2019. We acknowledge support of this work by the project “PANhellenic infrastructure for Atmospheric Composition and climatE change” (MIS 5021516) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).