Evaluation of LPATS data using VHF interferometric observations of lightning flashes during the Eulinox experiment

During the Eulinox (European Lightning Nitrogen Oxides Project) campaign, two lightning sensors were available: a Lightning Position and Tracking System (LPATS), and the ONERA VHF interferometric (ITF) mapper. We looked for the typical VHF signature of positive and negative cloud-to-ground flashes in ITF records in order to separate intra-cloud (IC) flashes from cloud-to-ground (CG) flashes during five periods from 2 days. Then we used this set of data to check the efficiency of the South Germany LPATS. We concluded that this LPATS detected nearly all the negative CG flashes, but one-fourth of LPATS negative strokes are in fact IC flashes. The ratio of misinterpretation is much smaller (15%) for multi-stroke negative CG flashes. The LPATS recorded 62% of the positive strokes, but only 43% with the right polarity, and only 25% of LPATS positive strokes actually belonged to a positive CG flash. This reliability ratio is 100% if we consider only high-intensity LPATS strokes.