Gravity waves queensland australia weather clouds
Gravity waves were detected on satellite imagery off the coast of central and southern queensland, australia. Strong convective activity was developing at the initiation of this weather phenomenon.

What Is A Gravity Wave?

A wave that is created by gravity and density variations in a stratified atmosphere. This is a generic classification that includes lee waves, mountains waves and other waves that can form in the atmosphere.

What does this mean in English?

Simplified Definition of Gravity Waves In Clouds and The Atmosphere.

This is how it works. A pebble dropped in calm water will cause ripples to form from the point it touches the water.

It happens the same way in our atmosphere. Think of air as a fluid. A pebble could represent a strong storm, the wind blowing above a mountain, or even solar radiation. A calm pond means a stable atmosphere. The stable atmosphere will have cool air that is settled under warm air.

A gravity wave must be created by something moving vertically. This could be, for instance, strong thunderstorms or air rising from the ground.

For a gravity wave, the air must rise into a stable atmosphere. This forms the crest. The displaced air will continue its upward trajectory if it rises into unstable air.

Stable air is determined to keep its stability, so any air that is pushed into it will want the air to sink down to regain equilibrium.

The trough of the wave is formed by the sinking air. The air is similar to the wave in a pond. It will rise and fall, propagating away at its initiation point until its intensity decreases and equilibrium has been regained.

Gravity waves
On june 26, 2016, the moderate resolution imaging spectroradiometer (modis) on nasa’s terra satellite acquired this natural-colour image of cloud gravity waves off the coast of angola and namibia.

When there is stable air at 5,000 to 12,000 feet above the surface, the wave can grow. This channel allows the wave horizontally to move along the surface.

Clear skies can be seen where there is sinking air and clouds in the rising air. Parallel streets of clouds may result from a gravity wave.

As thunderstorms rocket into the tropopause, which is an area with very stable air in our atmosphere, gravity waves can be produced. This force can create gravity waves within the clouds as they push towards the tropopause.

Gravity waves often accompany pressure rises or falls (measured in millibars), as well as strong wind. Stronger winds are associated with a greater pressure change.

Gravity waves
Lightning flashes and gravity waves in tropical cyclone mahasen

Gravity Waves Tell Us That The Atmosphere Is Fluid

The atmosphere is constantly changing and fluid. Fluid dynamics such as circulation, currents, and gravity waves can affect the atmosphere.

Because the atmosphere is constantly moving, these phenomena are constant. However, it is difficult to actually see them.

Not to be confused by gravitational waves which are disruptions in the curvature spacetime caused by massive acceleration.

Gravity Waves In Weather and Clouds

Gravity waves, also known simply as buoyancy waves or gravity waves, are physical phenomena where waves are created in any fluid medium such as water, waves at the beach, and ripples in a glass.

They can also occur in gases like our atmosphere and are called gravity waves because gravity is the force that restores balance.

They are usually caused by airflow obstructions, such as mountains (on Venus this creates huge atmospheric waves), or collisions between different temperatures.

The disturbance is caused by the difference in density. Once that happens, the gravity wave can travel as the cold air spreads. They can travel long distances because they will continue to exist until the environment rebalances.

Adam Morgan, Australian Bureau of Meteorology meteorologist

Gravity waves
Atmospheric gravity waves off south island, new zealand nasa image captured december 21, 2010

People also ask

Is gravity affecting the weather?

Gravity waves are also important for air traffic and in forecasting turbulence. They also influence weather extremes like heavy rains or storms.

What is a Tsunami?

Tsunamis, which are long-range gravity waves that travel great distances in water, are known as “tsunamis”. These waves are often triggered by earthquakes, landslides, or volcanic eruptions.

Further Reading

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