New particle formation by ion-induced nucleation during dissipation stage of thunderstorm

A case of new particle formation observed during dissipation stage of a thunderstorm at a tropical station, Pune, India on 3 June 2008 is reported. The flash rate and rainfall intensity increased as high as 110 flashes per 5 minutes and 150 mm hour(-1) respectively during the active stage of thunderstorm, and then gradually decreased during the dissipation stage. The number concentration of particles in the size range of 10-100 nm sharply increased from 350 particles cm(-3) to similar to 8000 particles cm(-3) during the dissipation stage of a thunderstorm and grew to larger diameter subsequently. Observations suggest that the atmospheric conditions such as (i) reduced background aerosol concentration after heavy rain, (ii) high humidity condition, and (iii) increased ion concentration during the dissipation stage by corona discharges, favoured generation of new particles by ion-induced nucleation (TIN). Observations also suggest that generation of unipolar ions by corona discharges may be more favourable for TIN and subsequent growth of the particles.