Weather Insider: The satellites studying our oceans and El Niño
PASADENA, Calif. (KESQ) – As Southern California braces for what forecasters are calling a severe El Niño, a pair of satellites are watching the weather that unfolds.
Sentinel 6 and Sentinel 6B, orbiting some 800+ miles above the Earth, constantly stare at our oceans. Every ten days, they’re able to map about 95% of them. In doing so, they can sense the changes that are fueling El Niño.
Scientists at NASA’s Jet Propulsion Laboratory, or JPL, explained how it all works.
“[The satellites] send a radar wave down to the ocean and wait for it to bounce back up. And they just time how long it takes to go down and come back,” said Josh Willis, a climate scientist with JPL.
The vertical position of the satellites remain constant as they orbit the Earth. By knowing the position of the satellite in space and the time it takes for the radar waves to bounce back and forth, researchers can determine the average height of the water in a given area.
Each radar beam essentially maps a big circle on the ocean. The circle is about 10 kilometers, or 6 miles, in diameter. The heights of the top and bottom of the waves are collected, then averaged out.
“We’re looking down every second of every day measuring the planet’s oceans. And after about ten days, we can do the global average of sea level, and we can get an accuracy of global sea level change with just a few millimeters of accuracy,” he continued. “These satellites give us the biggest, clearest picture of El Nino that you can get.”
Warmer water physically stands taller. Measuring that change, scientists can focus in on the patterns that emerge. It’s especially important now, when sea surface temperatures are vastly warmer than usual due to El Niño.
“Not every El Niño means huge rains in Southern California,” said Willis. “But the satellites give us a picture of how this heat is moving around and how that’s going to play out on the weather. So by comparing it with past events, we really get a better idea of what’s going to happen this year.”
Scientists have been collecting this wave height data since the 1990s, which means they have access to decades of data, including the significant El Niño event of 1997. Sentinel 6, named “Michael Freilich” in honor of the late oceanographer who served as director of the NASA Earth Science division, launched in 2020. Sentinel 6B launched last year, joining Sentinel 6 in orbit. All of the data that is collected on the world’s oceans are available for public use; NASA’s catalog can be found by clicking here.
Willis said a wide group of forecasters, weather agencies, emergency planners, and more used the data to better understand and prepare for extreme weather events. Judging by the years of data they have banked so far, he was confident this year’s El Niño would be significant.
“This particular event seems to be as big, or maybe even bigger than the huge 1997 event, which caused trillions of dollars of damage around the planet.”
As El Niño intensifies, even residents here in the Coachella Valley are asked to prepare in the event of severe rain and flooding. You can find more of our El Niño coverage here.
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