Electrical characteristics of thunderstorms in different plateau regions of China

The electrical characteristics of thunderstorms in four plateau regions with different elevations are studied based on observations from 2002 to 2006. The thunderstorms can be divided into two categories, special-type and normal-type, in all four regions according to the polarity of the surface electric field (E-field) evolution beneath the thunderstorm during its mature stage. A negative surface E-field was observed beneath the special-type storm, and positive beneath the normal-type. The occurrence of the special-type thunderstorm was positively related to the elevation of the region, with the most frequent occurrence observed in the central Tibetan Plateau. The main charge region inside both types of thunderstorms could be represented basically by a tripole structure with the special-type being characterized by a larger-than-usual lower positive charge center (LPCC) at the base of the storm. The temperature difference between the surface and 2 m above the surface, Ts − T2m, and air humidity prior to the storm seem to be two key parameters which influence greatly the formation of the LPCC. A larger Ts − T2m and a lower air humidity might result in a thunderstorm with a large LPCC. The intracloud (IC) flashes could occur either within the upper dipole or more frequently within the lower dipole. The corresponding discharge height, obtained based on multiple-station measurements of lightning E-field changes, was located at about 3.3–5.6 km and 6.8–7.7 km above sea level (asl). The negative charge center was located at a range between 5.7 km and 7.7 km asl.