A New Look at Earth Lightning

Since the dawn of humanity, lightning has been both a source of curiosity and admiration. Although dozens of lightning bolts crackle at any time somewhere on Earth, these brief electric shocks, which usually last less 30 microseconds– remain exceptionally difficult to study.

However, satellites have done a lot to deepen our understanding of lightning in recent decades. Sensors in space have provided high-quality observations of lightning since the 1990s, allowing atmospheric scientists to quantify and map the global distribution of lightning.

One of the first global maps of lightning activity was published in 2001 with data from the Optical transient detector (OTD) on advertising OrbView-1 satellite and the Lightning image sensor (LIS) on NASA TRMM Satellite. Two decades later, a second LIS mounted on the International Space Station (ISS) adds to long-term records and creates new and better maps of global lightning activity.

The map above is based on observations from several sensors: the ISS LIS, the TRMM LIS and the OTD. The TRMM LIS collected data between 1997 and 2015; OTD was operational between 1995 and 2000; and ISS LIS has been flying since 2017. Scientists at Los Alamos National Laboratory and University of Alabama-Huntsville published a map updated in March 2021. Researchers at NASA’s Marshall Space Flight Center published a similar map of lightning activity, based on three years of ISS LIS observations, in July 2020.

“What is new and remarkable about the ISS LIS is that it gives us observations much further north and south than what we got from TRMM,” said Patrick Gatlin, scientist at the ISS. atmosphere at NASA Marshall. “The ISS LIS observations extend to latitudes up to 55 North and 55 South, to Canada and Patagonia. The first global lightning maps used TRMM LIS observations limited to the tropics. (Researchers typically use older, lower-quality data from OTD to fill in gaps in high latitude areas.)

“One of the cool things about the ISS LIS data is that we are starting to be able to compare what is happening with lightning now to what we saw in the 1990s with OTD, and with what we have. seen in the 2000s and 2010s with TRMM LIS, “said Tim Lang, atmospheric scientist at NASA Marshall.” Satellites also have a built-in advantage over ground networks because we don’t have gaps in the network and we have measurements over the oceans. “

Earlier lightning activity cards assigned to lightning flash a single coordinate on a card. By reprocessing all OTD and LIS data, the scientists were able to include the horizontal dimensions. “Our analysis takes into account that lightning can travel horizontally, not just vertically from clouds on the ground,” said Michael Peterson of the Los Alamos National Laboratory. “One way to think of this new climatology is that it tells us how often an observer can expect lightning to be visible above their head, regardless of where the lightning strikes. started or ended. “

“Some eclairs, we call them mega-flashes– actually spread over incredibly long horizontal distances, sometimes hundreds of kilometers, ”Peterson added. the longest lightning ever recorded traveled 709 kilometers (440 miles) as it crackled across Argentina and Brazil for 11 seconds in 2018.

While the new approach alters some details of our understanding of lightning, the general patterns remain similar to before. With an average lightning rate of 389 per day, Lake Maracaibo in northern Venezuela (pictured above) has the highest lightning extent density in the world. This region is unique geography feeds the weather conditions which make it a magnet for thunderstorms and lightning. The area along Lake Kivu, on the border between Cameroon and the Democratic Republic of the Congo, comes next with an average of 368 flashes per day.

While the researchers are still harmonizing the various data records, they are optimistic that satellite data will prove useful in identifying trends in lightning activity. They also hope to be able to determine whether climate change is affecting lightning. Some scientists predict that patterns will change as the world warms and weather fronts and storm tracks adapt. By contributing to the production of nitrogen dioxide, a greenhouse gas, lightning also contributes directly to global warming. “It is even more urgent to examine the effect of climate change on lightning because the World Meteorological Agency recently added lightning to her list of essential climatic variablesLang said.

Image from NASA’s Earth Observatory by Lauren Dauphin, using data from Peterson, et al. (2021). Photograph by Nasa. Story of Adam Voiland.

Robert M. Larson