Magnetic Field Risetimes of Negative Lightning First Return Strokes Over Land and Ocean

Amitabh Nag, Kenneth L. Cummins

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


We examined risetimes for negative first strokes occurring over land (3,427 strokes) and ocean (4,302 strokes) in Florida reported by the U.S. National Lightning Detection Network. The waveform characteristics were measured by a single National Lightning Detection Network sensor located less than 2 km from the coastline in Florida. All risetime measurements (10–50, 50–90, 10–90%, and threshold to peak) over both land and ocean exhibited statistically significant positive correlation with estimated peak current, but with small correlation coefficients. For a subset of 1,247 strokes selected to mitigate bias in our data, the median 10–50% magnetic field risetime was found to be 11% longer and the proportion of strokes having 10–50% risetimes in the range of 2.6 to 4.8 μs was 42% larger over ocean. We speculate that the slow-front portion of radiation field waveforms for negative first strokes is affected by differences in surface properties over land versus over ocean that impact upward leader initiation.

Original languageEnglish (US)
Pages (from-to)13,133-13,141
JournalGeophysical Research Letters
Issue number23
StatePublished - Dec 16 2018


  • cloud-to-ground lightning
  • first stroke
  • lightning on land versus ocean
  • magnetic fields
  • negative return stroke
  • risetimes

ASJC Scopus subject areas

  • Geophysics
  • General Earth and Planetary Sciences


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