[News Terms] Kelvin Wave, a Precursor to El Ni?o

The 'Kelvin wave' is a long-period wave that appears in the Earth's atmosphere and oceans. It can be described as a wave that is reflected when it hits a boundary (waveguide) such as the coast (land) in the sea.

The heat flow from the hot equator to the cold polar regions continuously proceeds through the atmosphere and oceans, but fluids like water and air have inherent instability, making the flow irregular. Because of this, the mid-latitude regions where the cold air (sea) of the poles meets the warm air (sea) of the equator periodically experience unpredictable abnormal climate, and two waves that decisively influence this are the Kelvin wave and the Rossby wave.

The Earth is getting even hotter due to abnormal high temperatures caused by climate change and the intrusion of El Ni?o.
[Photo by Pixabay]

Kelvin waves and Rossby waves are waves that occur at the boundary where the cold air of the poles meets the warm air of the equator. Rossby waves generally move westward due to the Coriolis effect, as the Earth's rotation causes deflection to the west in the Northern Hemisphere. Kelvin waves can move freely in the atmosphere where there is no boundary, but in the ocean, their movement is blocked by land (coastlines). Kelvin waves are waves generated by being blocked at the boundary, flowing along the coast, and act in the opposite direction to Rossby waves.

Rossby waves are waves created by the westerly winds caused by the Earth's rotation, sending seawater toward the western Pacific, and about half of this seawater collides with the East Asian coast and is reflected eastward, creating a wave called the Kelvin wave. As the Kelvin wave pushes warm seawater and winds eastward, the sea surface temperature in the eastern Pacific rises, causing the El Ni?o phenomenon. Rossby waves can be considered primary waves, while Kelvin waves are secondary waves that appear due to interference with the coast (boundary).

NASA recently announced that Kelvin waves are forming near the equator and moving warm seawater from the western Pacific to the eastern Pacific.

Kelvin waves are a precursor to El Ni?o. The last time El Ni?o appeared in 2016, it was recorded as the hottest year due to the combined effects of greenhouse gases. Early heatwaves are raging in many parts of the world, including the United States, Europe, and Asia. With abnormal high temperatures caused by climate change and the intrusion of El Ni?o, the globe is becoming even hotter.