Earth from Orbit: Gravity Waves
On April 3, 2021, NOAA’s GOES-16 and NOAA-20 satellites viewed gravity waves rippling over Western Pennsylvania.
Gravity waves are similar to what happens when you drop a stone into a calm pond, but they roll through the air and cloud tops instead of water. Just like waves form in the ocean or a lake when water is disturbed, waves also form in the atmosphere when air is disturbed.
The gravity waves seen in this video are known as terrain-induced waves. They form when air is forced upward by hills or mountains into a layer of stable air in the atmosphere. Gravity causes the air to fall back down, and it begins to oscillate, creating a ripple effect. Wind flowing over the Rocky Mountains, for example, can create gravity waves that are felt as turbulence on an airplane.
Clouds can form on the cooled crests of these waves when enough moisture is present in the atmosphere, as they did in this case. NOAA’s geostationary GOES-16 satellite and polar-orbiting NOAA-20 satellite captured stunning views of these wave clouds.
Because GOES-16 orbits 22,236 miles above Earth’s equator, at the same speed Earth rotates, the satellite has a constant view of the same area. This allows GOES-16 to monitor cloud formation and track the clouds in motion.
NOAA-20 orbits from pole to pole, imaging the entire Earth at least twice daily. NOAA-20 is positioned just 512 miles above Earth’s surface, allowing it to capture ultra-high resolution views of the wave clouds.
The gravity waves are seen in multiple types of satellite imagery. Visible imagery captures sunlight reflected off Earth and offers the highest-resolution view of the clouds. Data can be combined from multiple visible channels on the satellites’ imagers to create GeoColor and true color imagery, which approximate how the human eye would see Earth from space.
The gravity waves are also apparent in GOES-16 water vapor imagery, which shows how much moisture is present in the atmosphere. When gravity waves are evident in water vapor imagery, it sometimes indicates clear air turbulence. Turbulence can have significant impacts on aviation.
Note that gravity waves shouldn’t be confused with “gravitational waves,” waves in spacetime created as objects move through space.
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