Study identifies jet stream patterns locked in during winter’s extreme cold and wet weather
Big waves have doubled since the 1950s, possibly due to climate change
Winter is finally here. When the earth warms, a new study This suggests the atmosphere is being pushed forward, causing prolonged periods of extremely cold or wet weather in some areas.
The study’s authors say they have discovered huge meanders in the global jet stream that carry polar air south, keeping much of North America and Europe in cold or wet conditions at once, often for weeks at a time. They say the frequency of such weather waves has doubled since the 1960s. In the past few years alone, they have killed hundreds of people and crippled energy and transportation systems.
New paper published this week[HYPERLINK] inside Bulletin of the American Meteorological Society.
An idealized illustration of the massive meandering of the global jet stream, known as Wave 4 pattern, which is bringing extreme winter cold and/or precipitation (blue areas) to parts of North America and Europe. (Photo by Kay Kornhuber)
“Although winters are getting milder on average, this comes at the cost of increasingly destructive warm seasons,” said author Kai Kornhuber, an adjunct scientist at Columbia University’s Lamont-Doherty Earth Observatory. “Big extreme heat.” “A hundred years from now, we may not have to worry too much about extreme cold because everything is getting warmer. But today and in the future, cold is still a very relevant danger.”
The jet stream is a fast-moving river of air that continuously circles the Northern Hemisphere from east to west. It usually flows within a relatively straight boundary separating the cold polar air masses from the mid-latitudes, but sometimes it naturally produces large swings. Some scientists believe these wobbles are increasing in size and frequency due to rapid warming in the Arctic, which is warming far beyond regions further south. They said this could destabilize the system and create winds that could damage the north-south barrier. Under the right conditions, some of these wobbles can be amplified into symmetrical waves that then lock into place globally, somewhat similar to vibrations that produce a constant pitch.These are called rosby wave.
In a 2019 study Kornhuber and colleagues showed The repeating Rossby wave pattern known as Wave 7—seven giant peaks and seven matching wave troughs across the globe—draws warm, dry air from the subtropics into midlatitudes, triggering simultaneous waves in predictable areas Summer heatwaves and droughts in North America, Europe and Asia. These could lead to widespread simultaneous crop losses in key breadbasket areas, the study said.
The latest paper more or less shows the other side of the coin. The winter pattern known as the fourth wave – with four crests and four matching troughs across the globe – tends to lock into place. When this happens, the likelihood of extreme cold or moisture inside the tank triples, the authors say. At the same time, the mountain peaks may experience unusually warm or dry conditions.
The most recent major iteration of the fourth wave brought a February 2021 cold snap to much of Canada, the United States and even northern Mexico. Temperatures as far south as the U.S. Gulf Coast were 50 degrees Fahrenheit below average. Parts of the Deep South saw rare snowfall. Hardest hit was Texas, where record cold knocked out natural gas pipelines and other energy infrastructure and took down much of the power grid, plunging homes and businesses into darkness and ice. In total, at least 278 people died directly or indirectly from the cold snap, causing losses of nearly US$200 billion. A similar but less devastating event triggered a cold snap in the eastern United States in January-February 2019, killing more than 20 people.
The same pattern often occurs simultaneously on the other side of the Atlantic, often being most extreme in southwestern Europe and Scandinavia. Events in January-February 2019 brought extreme cold temperatures to southern France and Sweden. At the same time, moist air from the Atlantic swept in, causing extreme precipitation and flooding in many areas of central and eastern Europe. Similar incidents occurred in Europe in 2013 and 2018.
Researchers say that 50 years ago, such simultaneous waves occurred only once per winter on average. The numbers vary from year to year, but the average has now risen to two per year.
“There is growing evidence that extreme weather events in North America and Europe often occur simultaneously,” said another author of the study. Gabriele Messori Professor at Uppsala University, Sweden.Messori posted Papers from earlier this year Repeated examples of this phenomenon were noted and hypothesized to be related to large-scale atmospheric circulation patterns.
Kornhuber said the exact mechanism leading to the Wave 4 pattern requires further study, but he suspects it begins with cyclical changes in ocean conditions in parts of the Pacific. under appropriate circumstances, can trigger a global chain reaction. Identifying this mechanism may allow scientists to better predict cold snaps or wet waves, he said.
konub says There is more and more evidence Links between climate warming and heat waves brought by summer meanderings; however, winter waves remain a matter of intense scientific discussion.scientists are Several possible mechanisms are currently being investigated This could indicate a connection between climate and how things might evolve in the future.
Kornhuber pointed out A study he co-authored Research earlier this year showed that even during the summer, climate models still struggle to reproduce the most extreme regional weather anomalies associated with these larger-scale patterns; this can lead to underestimation of potential weather-related crop losses in specific areas. Next work will focus on investigating whether the worst extremes are related to human causes, or just natural variations, he said.
