CELLS v1.0: Updated and parallelized version of an electrical scheme to simulate multiple electrified clouds and flashes over large domains

Abstract

The paper describes the fully parallelized electrical scheme CELLS which issuitable to simulate explicitly electrified storm systems on parallelcomputers. Our motivation here is to show that a cloud electricity scheme canbe developed for use on large grids with complex terrain. Large computationaldomains are needed to perform real case meteorological simulations with manyindependent convective cells. The scheme computes the bulk electric charge attached to each cloud particleand hydrometeor. Positive and negative ions are also taken into account.Several parametrizations of the dominant non-inductive charging process areincluded and an inductive charging process as well. The electric field isobtained by inverting the Gauss equation with an extension toterrain-following coordinates. The new feature concerns the lightning flashscheme which is a simplified version of an older detailed sequential scheme.Flashes are composed of a bidirectional leader phase (vertical extension fromthe triggering point) and a phase obeying a fractal law (with horizontalextension on electrically charged zones). The originality of the scheme liesin the way the branching phase is treated to get a parallel code. The complete electrification scheme is tested for the 10 July 1996 STERAOcase and for the 21 July 1998 EULINOX case. Flash characteristics areanalysed in detail and additional sensitivity experiments are performed forthe STERAO case. Although the simulations were run for flat terrainconditions, they show that the model behaves well on multiprocessorcomputers. This opens a wide area of application for this electrical schemewith the next objective of running real meterological case on large domains. © Author(s) 2012.