Diurnal variation of surface electric field at a tropical station in different seasons: A study of plausible influences

Based on the fair weather days of 1993 surface electric field at Pune (18 32 N, 73 51 E, 550 m AS) is studied for its diurnal and seasonal variations. The analysis attempts to look into factors like atmospheric pollution and space charge formation in presence of the meteorological factors prevalent in the three seasons that modify the global effects that govern fair weather electric field at the site of measurement. Summer (FMAM), monsoon (JJAS) and winter (ONDJ) are the seasons considered. By and large diurnal variation is with double oscillation. The results show high persistent value of electric field during monsoon. Evening peak is the highest during winter with high atmospheric stability conditions and summer afternoons have the lowest value. Space charge formation depending on the wetness or dryness of the ground is proposed in connection with the high and low values of electric field close to ground. It appears that space charge is equally or more important in contributing to electric field variations as conductivity as for local effects. The generation of positive space charge occurrence in connection with evaporation and negative space charge occurrence with very dry ground bypassing the local component to global one due to large area coverage elsewhere as well, under similar weather conditions are suggested. Possibility of monsoon field showing a glimpse of global activities being a cleaner tropical environment during this period is also discussed. Observational verification of space charge formation and the role it could be playing, on abundantly available, by the then active physical processes plays on thunderstorm electrification based on convective theory is mooted