Narrow bipolar events, strong VHF pulses and the detection of severe weather from GPS orbit

FORTE and GPS satellite studies have shown that satellite-based VHF lightning sensors are particularly sensitive to a ubiquitous and unique type of strong in-cloud RF lightning pulse that is sometimes accompanied by a Narrow Bipolar Event (NBE). The physical relationship between NBEs and their impulsive VHF counterparts is not clear. Presumably, the strong VHF pulses are associated with an initiating breakdown process while the NBE emissions are linked to subsequent large-scale charge flow. Strong VHF pulses may or may not lead to NBE production (significant charge relaxation) but a NBE is always accompanied by a strong VHF pulse. More recent and ongoing work has focused on establishing the meteorological context of both NBEs and strong VHF pulses, particularly as they relate to satellite-based VHF lightning monitoring. Of particular interest is the possibility of using NBE/Strong VHF pulse occurrence as a tool for remotely detecting severe weather.

This paper presents a preliminary investigation into the relationship between NBEs, GPS-satellite-observed strong VHF pulses and the occurrence of severe weather. Strong VHF pulse data from lightning-sensitive VHF receivers aboard the GPS satellite constellation will be compared to NBE data collected by the ground-based Los Alamos Sferic Array (LASA) located in Florida and the Great Plains, NEXRAD radar scans and severe weather reports in order to evaluate the relationship between these lightning types and severe weather (also see K. Wiens paper in this session). Emphasis will be placed on identifying precursor indicators of severe weather via flash rate “jump” signatures and on comprehensively analyzing several notable case studies of severe weather outbreaks.