My next series is on peculiar weather events – the first in the series is the phenomenon of gravity waves which I have heard of but not researched until now.
Gravity Waves are physical perturbations driven by the restoring force of gravity in a planetary environment. In other words, gravity waves are specific to planetary atmospheres and bodies of water. In the case of atmospherics, as air blows across an ocean and then encounters an island, for example, that air will be forced to rise. Downwind from the island, the air will be forced to a lower altitude by gravity, but its buoyancy will work against gravity forcing it aloft again. The result is often a region of oscillating air in the atmosphere that can produce clouds in the waves’ crests (or highest points) as moisture from lower altitude condenses. Also, in the case of oceans, surface gravity waves form at the atmosphere/water interface; wind blows the surface out of equilibrium causing the restoring force of gravity to force the surface back down, while the water’s buoyancy pushes it back up. Wind-driven waves, tides and tsunamis are all examples of gravity waves.
Rippling gravity waves in the sky are usually invisible, but a satellite recently caught a rare glimpse of the phenomenon off the coast of northwestern Australia.
In the images, captured Oct. 21, air moves away from land and over the ocean, and rows of curved white lines emerge, like ripples do in disturbed water. Those thin white bands are clouds forming on the crests of atmospheric gravity waves.
Gravity waves appear following atmospheric disturbances; in this case, storms in the area produced cold air — which is denser than the warm air over land. Interaction between cool and warm air agitated the atmosphere, and the ripples that formed are gravity’s way of restoring that lost equilibrium.
Another typical cloudy day is in store for SW Michigan with perhaps a few sprinkles – out best chance of another soaking rain comes Thursday when we may see our temps rise to near 50°.