Featured Image from Bethany Laird on Unsplash
Author: Michael Peterson
Most lightning flashes only last 0.2 seconds, meaning if you blink at the wrong moment, you could miss it. However, scientists have developed new lightning-detection instruments, known as Geostationary Lightning Mappers (GLMs), that never miss a flash. The GLMs are aboard the two Geostationary Operational Environmental Satellites (GOES-West and GOES-East), which are in stationary orbits over the Earth’s western hemisphere. With the data from the GLMs, atmospheric scientists have discovered new lightning phenomena called “megaflashes” which can light up the sky for as long as 16 seconds.
Megaflashes are not the typical lightning flashes that observers notice during thunderstorms that extend vertically from the cloud to the ground. While they do occur during thunderstorms, megaflashes extend horizontally within clouds themselves over many miles. Because megaflashes are so large, humans on the ground can only see small parts of them, so to see an entire megaflash, you have to be looking down at the Earth from space. This is where the GLM instruments on the GOES satellites come in! The GLMs constantly observe the area between New Zealand and the west coast of Africa and record these extreme lightning events.
With data from the GLMs, Dr. Michael Peterson identified 194,880 megaflashes between Jan. 1, 2018 and Jan. 15, 2020. He then put together a summary of common characteristics of megaflashes in the Americas, including where and when they usually happen, and published it in the Bulletin of the American Meteorological Society. Before the GLM measurements, the most extreme lightning flashes observed by ground-based lightning sensors were 199 miles in horizontal extent and 7.74 seconds in duration. These new measurements show that megaflashes can be even more extreme, with the largest megaflash at 440.5 miles long and longest duration at 16.7 seconds!
Peterson has identified two megaflash hotspots: one over the central United States and one over Uruguay and southern Brazil. These are also regions where some of the strongest thunderstorms on Earth occur. These strong thunderstorms, known as Mesoscale Convective Systems (MCSs), are fast-moving systems that can generate multiple megaflashes. MCS-related megaflashes usually occur in the spring and early summer in both hotspot regions but can occur in the winter as well.
While some MCSs can produce up to 23 megaflashes in one day, other MCSs don’t produce any megaflashes at all. The author mentions that understanding why some MCSs produce megaflashes while others don’t will be a focus of future research. Ultimately, a better understanding of MCSs and megaflashes will lead to better lightning safety, as storms with exceptional megaflash activity are more likely to produce cloud-to-ground lightning that is hazardous to humans.
Satellite Technology Helps Discover New Weather Phenomena: Lightning Megaflashes by Alyssa Stansfield is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.