How are El Niño and lightning related?
El Niño conditions affect more than just clouds and rainfall in certain locations. Scientists have discovered that increased lightning and even increased tornado activity go along with El Niño.
There’s something about El Niño
During El Niño conditions, the eastern Pacific Ocean near the equator warms up. When the water warms up, the air above it also warms, creating far-reaching weather changes.
In this map, purple, blue and green are the colder parts of the ocean. Red, pink, and white are the warmer parts. Credit: NASA / Jason-1 and Jason-2 missions.
For one thing, El Niño conditions push the jet stream south, at times as far as the Gulf of Mexico.
What is the jet stream?
In North America, when we talk about “the jet stream,” we generally mean the northern polar jet stream. However, that is not the only one.
The jet streams are currents of fast-moving air in the upper levels of the atmosphere. They are caused by Earth’s rotation and heating of the atmosphere by the sun. The strongest jet streams are the polar jets, at around 23,000–39,000 feet above sea level, and the higher and somewhat weaker subtropical jets at around 33,000–52,000 feet. The Northern Hemisphere and the Southern Hemisphere each have both a polar jet and a subtropical jet.
Actual jet stream configuration. Credit: NOAA
The northern polar jet flows over the middle to northern latitudes of North America, Europe and Asia and the ocean between them. The southern polar jet mostly circles Antarctica year-round.
The jet streams are usually thousands of miles long, a few hundred miles wide, and just a few miles thick. These currents of air situate themselves at the boundaries between warmer air and much colder air. For example, polar jet streams form between cold, polar air and warmer air closer to the equator.
How does the jet stream affect weather?
Storms tend to follow the edge of the jet stream, where the difference between cool and warm air creates the turbulent conditions for storms. The farther south the jet stream is pushed, the warmer and wetter the air will be where the colder Arctic air meets up with it. That makes for more thunder and lightning, and more tornadoes.
What do we see?
Although all this makes sense, what do observations show? Do we actually see increased lightning and tornado activity during El Niño as opposed to normal years? Yes!
Number of winter days when lightning hit Earth’s surface during a strong El Niño period (left) and during La Niña (the opposite condition, in which the Pacific near the equator is colder than normal). Credit: Steven Goodman, Global Hydrology and Climate Center
Scientists have collected lightning data from existing instruments on two polar-orbiting satellites. The data definitely show increased lightning (which indicates storm characteristics) during El Niño years.