A GPS-based three-dimensional lightning mapping system: Initial observations in central New Mexico

A GPS-based system has been developed that accurately locates the sources o f VHF radiation from lightning discharges in three spatial dimensions and t ime. The observations are found to reflect the basic charge structure of el ectrified storms. Observations have also been obtained of a distinct type o f energetic discharge referred to as positive bipolar breakdown, recently i dentified as the source of trans-ionospheric pulse pairs (TIPPs) observed b y satellites from space. The bipolar breakdown has been confirmed to occur between the main negative and upper positive charge regions of a storm and found to be the initial event of otherwise normal intracloud discharges. Th e latter is contrary to previous findings that the breakdown appeared to be temporally isolated from other lightning in a storm. Peak VHF radiation fr om the energetic discharges is observed to be typically 30 dB stronger than that from other lightning processes and to correspond to source power in e xcess of 100 kW; over a 6 MHz bandwidth centered at 63 MHz.