Planetary Waves: A Source for Extreme Weather Conditions?

Extreme weather conditions are now becoming more common with climate scientists referring to extreme weather events as the ‘new norm’. It has been observed that contrasting extreme weather events occur simultaneously. For instance, in 2018, Western Europe and North America experienced new high temperatures and at the same time, other regions of the northern hemisphere were hit with torrential rain and severe flooding. Climate researchers have found that these events were caused by the stalling of ‘Rossby waves or Planetary waves’. So what are Rossby waves?

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ROSSBY WAVES:
These waves belong to a class of atmospheric waves that span thousands of kilometers with periods of several days. They are wave like fast-moving air that circles the northern hemisphere in the mid-latitudes and travel from east to west at an altitude of around 10 km. Atmospheric Rossby waves are crucial in shaping the planet's weather and climate by shifting high and low-pressure weather systems with them and by transferring heat from the tropics toward the poles and cold air toward the tropics from the poles.

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EXTREME WEATHER CAUSED BY ROSSBY WAVES:
Rossby waves are due to the temperature difference between the air present at the poles and the equator. Simply put, warm air from the equator tends to move towards the poles and cold air from the poles tends to move towards the equator. Imagine Rossby wave as a sine curve with warm air filling the peaks of the wave and cold polar air dropping into the troughs. The stalling of these waves often results in long persistent extreme weather conditions as the hot and cold air hover over the same place for weeks. If hot air gets stalled, sunny days can turn into a serious heat wave or drought, and if the cold air stalls lasting rains can lead to flooding. Due to Global Warming, as the arctic temperature increases, the temperature difference between the arctic and the equator reduces. This impedes the movement of the Rossby waves and results in extreme weather conditions.

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Research shows that warming caused by carbon dioxide from fossil fuels reduces the temperature difference between the Arctic and the equator. This will reduce air movement between them and could cause frequent extreme weather events like droughts, heatwaves, and floods and result in casualties and billions in economic losses.

REFERENCES:

1. https://www.nature.com/articles/s41558-019-0637-z
2. https://oceanservice.noaa.gov/facts/rossby-wave.html
3. https://physicsworld.com/a/summer-weather-extremes-linked-to-stalled-rossby-waves-in-the-jet-stream/

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