What is causing the winter heat wave in Europe?

Subject: Geography

Context:

Several parts of Europe witnessed an unprecedented winter heat wave over New Year’s weekend calling it an “extreme event”, experts said that temperatures increased 10 to 20 degrees Celsius above normal.

More on news:

At least seven countries recorded their hottest January weather ever.
These included Poland, Denmark, the Czech Republic, the Netherlands, Belarus, Lithuania and Latvia.

What is a heat dome?

A heat dome occurs when an area of high-pressure traps warm air over a region, just like a lid on a pot, for an extended period of time.
The longer that air remains trapped, the more the sun works to heat the air, producing warmer conditions with every passing day.
Heat domes generally stay for a few days but sometimes they can extend up to weeks, which might cause deadly heat waves.
Scientists suggest that any region of high pressure, whether a heat dome or not, forces air to sink and once it reaches the ground, it gets compressed and becomes even warmer.
Moreover, when air sinks, it gets drier and further raises the temperature of the area.

What is the relationship between heat domes and the jet stream?

The heat dome’s formation is related to the behaviour of the jet stream — an area of fast-moving air high in the atmosphere.
- The jet stream is believed to have a wave-like pattern that keeps moving from north to south and then north again.
- When these waves get bigger and elongated, they move slowly and sometimes can become stationary.
This is when a high-pressure system gets stuck and leads to the occurrence of a heat dome.
With the rising temperatures, it is expected that the jet stream will become more wavy and will have larger deviations, causing more frequent extreme heat events.