The effect of charge and electric field on the shape of raindrops


  • D. S. Zrnić,

  • R. J. Doviak,

  • P. R. Mahapatra


Closed form theoretical solutions have been obtained that relate the eccentricity of raindrops to charge and electric fields. The dependence of drop shape on electric field is highly nonlinear; it appears that commonly observed electric fields in clouds have little effect on drop shape whereas for somewhat stronger fields the growth in distortion is explosive. This is true irrespective of the charge on the drops. In the absence of an electric field the natural oblateness of drops is enhanced by the presence of charge. This increase in eccentricity might be detected as an enhancement of the differential radar reflectivity. With increasing vertical electric field, drops elongate vertically, starting from an oblate shape and passing through spherical and prolate shapes before breaking up. The role of charge in this process is to enhance preexisting oblateness or prolateness.