@Article{CamposSaWaPiKrOr:2014:StAn,
               author = "Campos, Leandro Zanella de Souza and Saba, Marcelo Magalh{\~a}es 
                         Fares and Warner, Tom A. and Pinto Jr., Osmar and Krider, E. 
                         Philip and Orville, Richard E.",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and Department of 
                         Atmospheric Sciences, South Dakota School of Mines and Technology, 
                         Rapid City, SD 57701, USA and {Instituto Nacional de Pesquisas 
                         Espaciais (INPE)} and Institute of Atmospheric Physics, University 
                         of Arizona, Tucson, AZ 85721, USA and Department of Atmospheric 
                         Sciences, Texas A and M University, College Station, TX 77843, 
                         USA",
                title = "High-speed video observations of natural cloud-to-ground lightning 
                         leaders - A statistical analysis",
              journal = "Atmospheric Research",
                 year = "2014",
               volume = "135-136",
                pages = "285–305",
                month = "Jan.",
             keywords = "lightning, high-speed camera, leaders.",
             abstract = "The aim of this investigation is to analyze the phenomenology of 
                         positive and negative (stepped and dart) leaders observed in 
                         natural lightning from digital high-speed video recordings. For 
                         that intent we have used four different high-speed cameras 
                         operating at frame rates ranging from 1000 or 11,800 frames per 
                         second in addition to data from lightning locating systems 
                         (BrasilDat and NLDN). All the recordings were GPS time-stamped in 
                         order to avoid ambiguities in the analysis, allowing us to 
                         estimate the peak current of and the distance to each flash that 
                         was detected by one of the lightning locating systems. The data 
                         collection was done at different sites in south and southeastern 
                         of Brazil, southern Arizona and South Dakota, USA. A total of 62 
                         negative stepped leaders, 76 negative dart leaders and 29 positive 
                         leaders were recorded and analyzed. From these data it was 
                         possible to calculate the two-dimensional speed of each observed 
                         leader, allowing us to obtain its statistical distribution and 
                         evaluate whether or not it is related to other characteristics of 
                         the associated flash. In the analyzed dataset, the speeds of 
                         positive leaders and negative dart leaders follow a lognormal 
                         distribution at the 0.05 level (according to the Shapiro-Wilk 
                         test). We have also analyzed how the two-dimensional leader speeds 
                         change as they approach ground through two different 
                         methodologies. The speed of positive leaders showed a clear 
                         tendency to increase while negative dart leaders tend to become 
                         slower as they approach ground. Negative stepped leaders, on the 
                         other hand, can either accelerate as they get closer to ground or 
                         present an irregular development (with no clear tendency) 
                         throughout their entire development. For all the three leader 
                         types no correlation has been found between the return stroke peak 
                         current and the average speed of the leader responsible for its 
                         initiation. We did find, however, that dart leaders preceded by 
                         longer interstroke intervals cannot present speeds of the order of 
                         107 m s- 1. Finally, we have analyzed the impact of recoil 
                         activity during positive leaders over their average speed and the 
                         return stroke peak current. Even though the analysis considering 
                         the leader speed was not conclusive it was possible to show that 
                         there is no apparent minimum or maximum peak current value for 
                         return strokes preceded by leaders with or without recoil activity 
                         (considering the most common range of values in literature, 20-80 
                         kA). © 2013 Elsevier B.V. All rights reserved.",
                  doi = "10.1016/j.atmosres.2012.12.011",
                  url = "http://dx.doi.org/10.1016/j.atmosres.2012.12.011",
                 issn = "0169-8095",
                label = "scopus 2013-11",
             language = "en",
           targetfile = "1-s2.0-S0169809513000057-main.pdf",
                  url = "http://dx.doi.org/10.1016/j.atmosres.2012.12.011",
        urlaccessdate = "27 abr. 2024"
}