A ONE-DIMENSIONAL LIGHTNING PARAMETERIZATION

In an extension of earlier work [Helsdon et al., 1992; Mazur, 1989], w e have developed a one-dimensional, electrostatic representation of th e electric field change and charge redistribution in a cloud subsequen t to a lightning flash. In this parameterization, these effects are de termined by the properties of the vertical electric field. We assume l ightning is initiated when the electric field magnitude reaches a pres cribed breakdown value at some point. The lightning channel is represe nted by a prolate spheroidal conductor of a specified radius, whose le ngth is determined by a crude energy criterion. Charge is induced on t he channel surface and this charge modifies the surrounding electric f ield. We have applied this parameterization to the vertical electric f ield resulting from an idealized charge sounding to explore the featur es of the charge profile that determine whether lightning is likely to be intracloud or cloud to ground. We discuss the results of this anal ysis in terms of lightning patterns observed climatologically and the evolution of lightning patterns in a thunderstorm during its life cycl e.