The Geography of Cloud-To-Ground Lightning in Yellowstone National Park



Amrhein, Ed

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Yellowstone National Park is well known for its vivid and diverse landscape, its abundance of wildlife, and its wildfires such as the 1988 “Summer of Fire”. Yellowstone is also well known for its volcanic activity-the cause of several geothermal hot spots that cover the landscape in the form of geysers, hot springs, mud pots, and fumaroles. In this study we learn that Yellowstone has other hot spots that are also important to the ecology of the park: clusters of cloud-to-ground (CG) lightning flashes. With the use of the latest GIS technology available, a 10-year National Lightning Detection Network (NLDN) dataset from 1995 to 2004 was analyzed to better understand the spatial and temporal pattern of CG lightning in Yellowstone. Graphs and maps visualizing lightning strikes and flash density reveal the seasonal and diurnal behavior of CG lightning in the park. Global spatial statistics reveal the spatial pattern of CG lightning is more of a random pattern while local spatial statistics indicate CG lightning is locally clustered. Maps visualizing results from local spatial statistics show hot spots of CG lightning activity over the mountain regions of the park and cold spots of CG lightning activity over the western and central plateau of Yellowstone. Finally, spatial regression analysis using the physical terrain properties of slope, aspect, elevation, and land cover resulted in statistically significant models that at most explained 17 percent of the variability in CG lightning flash density. Of the variables tested, only elevation appears to have a statistically significant relationship with observed spatial pattern of lightning flash density.



GIS, Lightning, Spatial statistics, Cluster analysis, Yellowstone