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Lightning in U.S. national parks

Lightning in national parks
Ron Holle
Senior Scientist, Lightning
Published: Jun 23, 2021
Meteorology
Weather & Environment

Lightning in U.S. national parks was recently summarized in a journal article published by the American Meteorological Society. This first-ever national study used data from Vaisala’s National Lightning Detection Network NLDN for the 46 national parks in the continental United States larger than 100 square kilometers. Figure 1 shows how these parks rank in terms of cloud-to-ground flashes per area of the parks. Notice that many of the 46 parks are in western states with low lightning frequency. 

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Figure 1: Cloud-to-ground flash density on a 2-km grid from the NLDN for 1999 - 2018 overlaid with the ranking (colored circles) according to cloud-to-ground flash density of the 46 continental United States national parks larger than 100 km2.
Figure 1: Cloud-to-ground flash density on a 2-km grid from the NLDN for 1999 - 2018 overlaid with the ranking (colored circles) according to cloud-to-ground flash density of the 46 continental United States national parks larger than 100 km2. The scale for the national map is in the lower right.

 

National park visitors travel to view natural features while outdoors. However, visits often occur in warmer months when lightning is present. The largest cloud-to-ground flash density is in Florida’s Everglades, and the smallest is near zero in Pinnacles National Park in California. The four parks with the largest number of visitors west of the Continental Divide, Grand Canyon, Zion, Yosemite, and Yellowstone, have most of their lightning from early July to mid-September and between late morning and early evening. Each park has its own spatial lightning pattern that is dependent on local topography.

Many of the people who visit national parks are from outside the state where the parks are located. So, lightning safety is problematic because the visitors are unfamiliar with the local situation when they visit for only a day or two at each park. When you visit a national park or any other outdoor location for recreation or leisure, remember the basic lightning safety rules. First, “When Thunder Roars, Go Indoors!” Second, ‘indoors’ means going into a substantial building or fully enclosed metal-topped vehicle. Picnic shelters, tents, and pavilions are not lightning-safe places. These lightning safety policies apply whether at home, work, or on vacation.
 

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