Some inferences on the role of lower positive charge region in facilitating different types of lightning

Abstract

It is generally thought that the lower positive charge region serves to enhance the electric field at the bottom of the main negative charge region and thereby facilitate the launching of a negatively-charged leader toward ground. On the other hand, the presence of excessive lower positive charge region may prevent the occurrence of negative cloud-to-ground discharges by "blocking" the progression of descending negative leader from reaching ground and thus "converting" the potential cloud-to-ground flash to an intracloud (or cloud-to-air) one. Assuming that the preliminary breakdown pulse train is a manifestation of interaction of a downward-extending negative leader channel with the lower positive charge region, we qualitatively examine the inferred dependence of lightning type on the magnitude of this charge region. Copyright 2009 by the American Geophysical Union.