Mexico has been experiencing a severe heatwave due to a massive heat dome that has been affecting the country for weeks. Now this system has extended northwards into the southern US, causing extreme temperatures across a large region.
What is a heat dome?
A heat dome is not a clearly defined scientific term, but it is used by many weather forecasters. The American Meteorological Society as an 鈥渆xceptionally hot air mass that develops when high pressure aloft prevents warm air below from rising鈥�. High pressure results in clear skies because sinking air warms as it descends 鈥� clouds form under the opposite circumnstances, with water droplets condensing out as rising air cools.
These high-pressure conditions mean lots of sunshine, which results in further warming and can dry out the soil, leading to less evaporation and a reduced chance of clouds and rain. These positive feedbacks can produce hotter and hotter conditions the longer the heat dome stays in one place. While heat domes cause heatwaves, there can be heatwaves without heat domes.
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What makes high-pressure systems get stuck?
The jet streams are fast-flowing bands of wind in the upper atmosphere that usually help move weather systems along the planet鈥檚 surface. But sometimes big loops form in a jet stream, resulting in weather systems getting stuck in the loops. These blocking patterns, as they are known, can lead to extreme cold, extreme rain or, in the case of heat domes, extreme heat.
How long do heat domes last?
They can last anywhere from days to weeks. For instance, over Canada and the northwest US in 2021 lasted nearly a month. During this event, the temperature reached nearly 50掳C (122掳F) in British Columbia, the highest ever recorded in Canada.
Are heat domes becoming more common as a result of global warming?
Heatwaves in general are because of climate change, but most studies don鈥檛 look specifically at heatwaves caused by heat domes. There is a lot of debate about how warming will affect in place. concluded there will be an increase in 鈥渟ummer heat-dome-like stationary waves鈥� over northwestern North America.
Are heat domes becoming hotter as a result of global warming?
Yes, this is certain. Because the world is now nearly 1.5掳C warmer than in preindustrial times, when heat domes form today surface temperatures can get hotter than they previously would have. For instance, 聽the extreme temperatures recorded during the 2021 heat dome in Canada were 鈥渧irtually impossible without human-caused climate change鈥�. There is also some evidence that the intensity of heat domes is outpacing the warming trend, suggesting climate change is amplifying their intensity. 鈥淭he intensities of hot extremes associated with鈥� heat dome-like atmospheric circulations increase faster than background global warming in both historical change and future projection鈥�, states .
