Rossby waves, also known as planetary waves, naturally occur in rotating fluids. Within the Earth’s ocean and atmosphere, these waves are formed as a result of the rotation of the planet.
Slow-moving oceanic Rossby waves are are fundamentally different from ocean surface waves. According to NOAA, unlike waves that break along the shore, Rossby waves are huge, undulating movements of the ocean that stretch horizontally across the planet for hundreds of kilometers in a westward direction.
They are so large and massive that they can change Earth’s climate conditions. Along with rising sea levels, King Tides, and the effects of El Niño, oceanic Rossby waves contribute to high tides and coastal flooding in some regions of the world
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The horizontal wave speed of a Rossby is dependent upon the latitude of the wave. In the Pacific, for example, waves at lower latitudes may take months to a year to cross the ocean. Waves that are created farther away from the equator of the Pacific may take closer to 10 to 20 years to make the journey.
The vertical motion of Rossby waves is small along the ocean’s surface and large along the deeper thermocline. This variation in vertical motion of the water’s surface can be quite dramatic: the typical vertical movement of the water’s surface is generally four inches or less, while the vertical movement of the thermocline for the same wave is approximately 1,000 times greater.
In other words, for a four inch or less surface displacement along the ocean surface, there may be more than 300 feet of corresponding vertical movement in the thermocline far below the surface! Due to the small vertical movement along the ocean surface, oceanic Rossby waves are undetectable by the human eye. Scientists typically rely on satellite radar altimetry to detect the massive waves
Atmospheric Rossby Waves
Atmospheric Rossby waves form mainly due to the Earth’s geography. Rossby waves help transfer heat from the tropics toward the poles and cold air toward the tropics in an attempt to return atmosphere to balance. They also help locate the jet stream and mark out the track of surface low pressure systems. The slow motion of these waves often results in fairly long, persistent weather patterns.