Lightning is the electrical discharge between positively and negatively charged regions within clouds. Visually, lightning is comprised of bright flashes of light called strokes. The loud sound of thunder that accompanies lightning is a sonic shock wave produced by the rapid expansion of the air surrounding the lightning channel during the stroke, similar to a sonic boom. Typically, more than 2,000 thunderstorms are active throughout the world at a given moment, producing on the order of 100 flashes per second. Each year, lightning is responsible for about 24,000 deaths per year, 240,000 injuries per year, and millions of dollars in property damage per year.

Lightning research has come a long way in the past few decades. Looking back at Space Shuttle lightning experiments in the 1980s, we now have a better understanding of why lightning occurs and where, what lightning patterns exist over the globe, and what lightning tells us about atmospheric convection. Most ground-based and airborne lightning sensors are only capable of detecting cloud-to-ground lightning, which is known to make up only about 25% of all lightning activity (Intra-cloud lightning is the most common type of discharge). With the use of space-based lightning sensors, we can now measure all forms of lightning over both land and sea, 24 hours a day.

The primary objectives of lightning study include determining the relationship between the electrical characteristics of storms and precipitation, convection, and severe weather. NASA also has an interest in pursuing lightning research for its own operations — lightning strikes to spacecraft can cause severe hazards, such as during the 1969 launch of the Apollo 12 mission, when lightning briefly knocked out vital spacecraft electronics. Fortunately, the astronauts regained control.  

NASA’s archives contain near real-time and historical lightning data from around the globe. The data are open and available to researchers worldwide, resulting in numerous advancements in the field of atmospheric science.