Lightning strikes the ground around the U.S. roughly 25 million times a year, but that’s nothing compared to the number of lightning flashes that stay up in the cloud, which happen five to 10 times as often. Now, there is a new eye in the sky watching out for all lightning types, which could improve forecasting of the severe storms that lightning signals, as well as providing novel insights into climate change’s impacts on such storms.

The Geostationary Lightning Mapper (GLM) is one of the 34 meteorological, solar, and space weather instruments on the brand new GOES-16 satellite. GLM, an optical detector, continuously looks for lightning flashes in the Western hemisphere with a higher sensitivity than previous space-borne instruments and wider coverage than current ground-based systems.

The first images from GLM were released in March. Data from GOES-16 is considered preliminary while the satellite undergoes testing. It is expected to be “operational” sometime in the next few months.

Before GLM, ground-based networks could only capture between 27 and 45 percent of in-cloud lightning, said Chris Schultz, a researcher at NASA’s Marshall Space Flight Center in Huntsville, Ala. And that in-cloud lightning is important, as it often occurs before the first cloud-to-ground flash, and acts, Schultz said, as “a surrogate for updraft,” the rising motion in the atmosphere that develops into a thunderstorm.

Updraft is notoriously hard to measure, but doing so could provide critical insight into how a storm is developing. Schultz developed an algorithm, known as the “lightning jump algorithm,” that monitors lightning trends and looks for when an increase in the rate of lightning occurs, signalling that the updraft has intensified and that the probability of severe weather has increased.

Thus, with GLM, these storms are detected before they start producing damaging winds, hail, or tornadoes. According to NASA’s page on GLM, “such storms often exhibit a significant increase in total lightning activity, often many minutes before the radar detects the potential for severe weather.”  

Forecasters are excited about the advantage offered by GLM, said Harold Brooks, a researcher at the National Severe Storms Laboratory (NSSL). Now, “before stuff starts happening near the ground, they’ll have gotten a clue that the storm has really started to be active.”

Research done at the Marshall Space Flight Center shows that the lightning data from GLM, which has already observed hundreds of storms, “provides anywhere from eight to 20 extra minutes of lead time on that first cloud-to-ground flash,” said Schultz. This could be critical for alerting people to seek shelter from those first flashes and other threats that could be coming.

This is also the first time that there will be lightning detection coverage over parts of the Atlantic and Pacific oceans, which could provide aviation forecasters with better data to reroute aircraft around the most intense storms, Schultz said.

GLM will also be able to track lightning over areas on land that didn’t have good radar coverage previously. This could provide researchers with a better understanding of where thunderstorms occur most frequently and where they tend to be most intense.

GLM offers “the first long-term high quality global lightning information that we’ve ever had. And that is just fundamentally interesting just in terms of where thunderstorms occur,” Brooks said.



GLM will also offer a uniform dataset for the information on lightning it gathers. “Being up in space, you have one sensor and you can see across the entire field of view. The lightning measurements will be uniform and applicable globally,” Schultz said.

Truly global coverage will come when European and Japanese satellites equipped with their own GLMs come online over the next five years.

The large, long-term dataset constructed from these instruments could also help scientists understand any links between severe storms and climate change. A study published in 2014 found that for every degree Celsius of global temperature rise, we could see a 12 percent increase in lightning rates, leading to a 50 percent increase by the end of the century. 

“To the extent that warm years now look like normal years in the future, that might tell us something about how we might expect lightning to change in the future from the current average,” Brooks said.  

And as lightning from these storms increases, it seems possible that climate change will have parallel effects on other dangerous aspects of severe storms, since some research suggests that a warmer climate will be a better breeding ground for severe storms.

Some research has found that in recent decades, more severe tornado outbreaks have occurred over fewer days. Whether climate change is playing a role in this trend remains uncertain, and much more research needs to be done to illuminate the connection between climate change, more intense storms, and related severe weather events. But it looks like GLM will help.