Delineating Urban-enhanced Lightning Production: An approach using Flash-defined Thunderstorm Tracks.

Lightning hazards are often less spectacular and more isolated than those produced by hurricanes or tornadoes. Consequently, lightning has been under recognized in its potential to generate large economic losses. Recent studies have found that heat generated from large urban areas alter the local distribution of lightning. However, little is known about the characteristics of this lightning and how surface properties and land-use trends influence its damage potential. Evidence suggests, trends in lightning property damage can be attributed to the background thunderstorm regime, a control imposed by the physical environment. Other studies emphasize that these loss trends are caused by an increasing societal sensitivity to thunderstorms through urbanization. This investigation is unique in that there is simultaneous consideration of the physical environment and the societal template as interacting causal agents. The study region, Atlanta, Georgia, USA provides an ideal setting to investigate how these interactions shape lightning hazards. Results suggest that the highly populated suburban counties to the northeast of downtown Atlanta have lightning strike densities approaching those along the lightning active northern Gulf Coast of Florida. This flash density hotspot is collocated with a zone of high-density land use indicative of urban flash augmentation. In addition, a lightning tracking algorithm revealed the nature of individual thunderstorm tracks creating the hotspot. Increases in lightning flash production were noted in individual storms passing over high-density urban land use.