Possible Effect of Electrical Forces on Drop Size Distribution in Thunderstorms

Evolutions of electrical, microphysical and dynamic processes occur almost simultaneously in a thunder cloud and influence each other. For example, the shape, growth, breakup, evaporation characteristics of water drops are strongly influenced if the drops are charged or they are falling through electric fields. Many simulation experiments and theoretical calculations show that the time and intensity of the occurrence of downdraft can be modified by the storm electrification. Vonnegut (1960) has suggested that even the strong wind speeds in tornadoes can be driven by the intense activity of lightning discharges frequently reported to occur inside the tornado funnel.  Storm electrification has been reported to strongly enhance the collision and coalescence characteristics of cloud drops. Observations of raingush phenomenon below thunderclouds is one of the strongest manifestation of such an enhancement in the collision and coalescence efficiencies of water drops Doppler radar  and  lightning detection network can be used to study the phenomenon of raingush .  A better understanding of the raingush phenomenon can certainly help in understanding the cloud burst phenomenon associated with severe thunderstorms.

 In the present study we have done a comparative analysis of size profile and drop size distribution of electrified and non electrified clouds system using ground based micro rain radar and impact disdrometer. Separation between electrified and non electrified cloud system is done by using WLN and IITM lighting network data .Significant differences have been found  in drop size distributions in electrified and non-electrified clouds and quantified.  The growth rate of raindrops observed in electrified cloud has been found to large compared that in non-electrified cloud. Size distribution broaden towards larger side of the spectrum in electrified cloud. Drop size distributions during initiation, mature and dissipation stages of a thunderstorm are also studied to understand the effect of electrical forces on microphysical process in thundercloud.