Study
Previous studies on heatwaves have mostly focused on how frequent heatwaves are or how hot it gets during one.
In recent study, the researchers classified contiguous heatwaves as events with extremely high temperatures, covering more than a million square kilometres, and lasting for longer than three days.
They then tracked the movement of these huge masses of hot air over space and time, studying how far and how fast they were moving – one of the first groups of scientists to do so.
Instead of just focusing on the frequency and the intensity of heatwaves, the study also checked how fast they were propagating and how long they lasted.
By looking at how heatwaves move over time and space, the study has bridged the gap between the thermodynamic and dynamic pieces of the heatwaves puzzle a little more than before.
This study is looking at heatwaves like an object that can move and can travel and propagate, which you would miss if you were just looking at one point
Jet stream
The scientists analysed the upper atmosphere’s air circulation patterns, to see how the moving air could affect these big blobs of heat.
They found that over the years, the jet stream — a fast, narrow current of air that flows from west to east high up in the troposphere — has become weaker.
The jet stream guides atmospheric waves, waves that are caused by the earth’s rotation and which influence the earth’s surface temperature.
As the jet stream weakens, these waves also move more slowly, leading to more persistent weather events, and more spells of high and slow-moving heat.
Though natural climate variability and natural events also influenced how heatwaves had changed, human activity and greenhouse gas emissions have played a dominant role in rendering the slower-moving and longer-lasting heat.
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