You may not have heard of Rossby waves, but they affect the weather on our planet 24 hours a day.
Identified and explained by Carl-Gustaf Arvid Rossby, these waves occur due to the rotation of the Earth, according to the National Oceanic and Atmospheric Administration (NOAA). Compared to typical ocean waves we see along the coast, Rossby waves move significantly slower. They are also extremely large, with some stretching hundreds of miles (or more) across the ocean. Generally, Rossby waves move westward, separating cold polar air from warmer local air (according to Britannica).
When we think of climate change, we often consider the phenomenon of global warming, melting ice at the poles, or the impact of ENSO (El Niño, La Niña) on the formation and development of storms, droughts, tornadoes, and rising sea levels… However, underlying all these “global disasters” is a type of wave known as planetary waves or Rossby waves. It can be said that this is the macro wave that governs climate phenomena worldwide, affecting all life on Earth.
Rossby waves have two components: long waves and short waves. Long waves can stretch from 3,700 to 8,000 miles, and they can be oriented horizontally or vertically. Short waves exist within long waves, but they do not always align with their direction. As a result, short waves can change the shape of long waves as they typically move eastward, according to the National Weather Service (NWS).
The depth of the ocean, the latitude of the waves, and the fluctuations between warm and cold ocean layers influence the movement of Rossby waves. Additionally, they are affected by land masses of varying shapes that create uneven temperatures as the sun warms the Earth’s surface.
Rossby waves are natural waves generated when fluid substances (such as air and water) move in spirals due to the planet’s rotation. Therefore, these waves exist not only on Earth but also on the Sun. As the Earth rotates, it creates planetary vortices (with axes aligned with the Earth’s imaginary axis, centered at the poles) and generates Rossby waves. On Earth, this type of wave exists in both the atmosphere and the oceans, as the movement of air or ocean currents affects the climate, making these waves crucial for climate change.
Just as temperature influences Rossby waves, the waves themselves also impact the Earth’s atmosphere, generating Rossby waves in the atmosphere. Simply put, warm air from the equator moves towards the poles, and cooler air from the poles moves towards the equator. Although this movement is inconsistent, it is fairly regular and helps form jet streams in the atmosphere.
Air moves over or around mountains, and elevation differences also contribute to the formation of Rossby waves—winds change speed or direction to restore balance to the ever-changing atmosphere. However, as long as the sun shines and generates heat, the imbalance will persist.
Rossby waves affect weather patterns across continents because they are so large. But short waves also impact the weather. In fact, they are what the NWS calls “the main culprits of rainfall events”, noting that rain bands often accompany them as they pass through various parts of the planet.
In the oceans, this type of wave comes in many shapes and sizes and moves in very complex ways, potentially affecting ENSO, tides, and rising sea levels. The El Niño phenomenon is closely related to the Southern Oscillation (SO), which is essentially a form of Rossby wave (in the form of long waves) existing in the atmosphere of the South Pacific region. Meanwhile, Rossby waves in the atmosphere play a role in transporting heat from tropical regions to the poles and vice versa, bringing cold air from the poles back to the equator, helping to balance the planet’s temperature. Because planetary waves play a crucial role in regulating the climate, scientists began to take interest in researching them in the early 20th century, and breakthroughs in atmospheric physics led to the development of modern numerical weather forecasting methods.
Because long waves move slowly, they can cause weather patterns to persist for extended periods. NOAA reports that they can also alter weather, noting that they can contribute to rising sea levels and cause coastal flooding in some areas. For example, the effects of El Niño and La Niña in the Pacific can take several months to a year to traverse the ocean, resulting in elevated tides.
That said, sometimes Rossby waves can play a role in “extreme weather events”, according to the journal Environmental Research Letters. Furthermore, a report published in the journal Nature Climate Change indicates that Rossby waves can trigger heatwaves and flooding in the Northern Hemisphere.
