Electrical structure in thunderstorm convective regions: 1. Mesoscale convective systems

Abstract

Electric field (E) soundings through convective regions of mesoscale convective systems (MCSs) are examined in this paper. Ten E soundings through updrafts in MCS convective regions and five soundings in MCS convective regions outside updrafts are used to show that a typical electrical structure exists in this region. These 15 E soundings plus one other previously published sounding, which is included in this analysis, comprise all known soundings in the convective region of MCSs. The basic charge structure identified in MCS updrafts consists of four charge regions, alternating in polarity, with the lowest region positive and the highest region negative. The basic charge structure outside updrafts in MCS convective regions has six charge regions, alternating in polarity, with a positive charge region lowest. Maximum E magnitudes of both polarities are larger and are located at lower heights in soundings outside updrafts compared to those within updrafts. Excepting the upper positive charge, inferred charge regions are shallower and have larger charge densities outside updrafts. The center of the main negative charge is lower and warmer outside updrafts (5.5 km, −6.2°C) than within updrafts (6.9 km, −15.7°C). These features inside and outside updrafts are incorporated in a new conceptual model of MCS convective region charge structure. Also, an expanded conceptual model is developed, using previously published data from other parts of MCSs. This more complete conceptual model shows the typical electrical charge, airflow, and reflectivity features in the stratiform region, the transition zone, and the convective region of midlatitude mesoscale convective systems.