An Exploratory Study of Lightning Activity on Southeast and South of Brazil

Lightning, radar and satellite data is used to document the temporal and spatial variability and polarity of Cloud-to-Ground (CG) lightning activity in wide range of synoptic and mesoscale systems (cold /warm frontal bands, tropical instability line, squall lines and non-line thunderstorms) occurred in south and southeast of Brazil and neighbors.

Predominantly negative activity is observed: about of 70-80% of CG flashes were negative. Positive discharges can dominate sometimes and generally have more elevated values of daily mean current and maximum. In major part of systems, time separation of frequency of positive and negative flashes is observed. The frequency of negative CG activity is highest around the period of initial and maximal activity of system. The positive activity is highest in latest periods of system's life when total activity is diminished. Frequently jump of positive activity means rapid dissipation of mesoscale system.

System's velocity and propagation derived from lightning, radar and satellite data confirmed that negative CG generally confined to the propagating part of mesoconvective system. Some mesoscale convective lines have only negative activity. Positive activity is more diffused in space and major part of positive CG flashes localized downstream in respect to area of major part of negative CG.