Scientists have identified a “climate teleconnection” between the Rocky Mountains and the Tibetan Plateau: warm spots on the plateau left a kink in the jet stream, triggering two catastrophic rainfall events halfway around the world in California and nearby states in early 2017 and 2023, a new study reports. The results could improve forecasts of extreme weather in the western U.S., potentially saving lives and billions of dollars in property damage, the authors say.
The Tibetan Plateau link
Roughly one month after each hotspot appeared, record-breaking precipitation hit:
- California
- Nevada
- Oregon
- Utah
- Arizona
Together, the storms caused around $6.6 billion in damage and killed at least nine people, according to the study.
| Tibetan Plateau warmer than usual for the season | Record precipitation |
|---|---|
| December 2016 | Early 2017 |
| February 2023 | 2023 |
State-of-the-art forecast systems, which rely heavily on ocean conditions like El Niño, failed to predict this extreme rainfall, said study first author Yongkang Xue, a distinguished professor of atmospheric and oceanic sciences at UCLA. The record precipitation occurred during La Niña years, typically associated with dry conditions in California.
“This study provides the first evidence from observational data analysis and model simulations that abnormally high early-winter temperatures on the Tibetan Plateau led to stronger atmospheric rivers along the U.S. Pacific Coast, driving heavy regional precipitation,” Xue told Live Science in an email.
How the weather traveled
Atmospheric rivers are narrow, elongated corridors of intense water vapor transport. As temperatures rose over the plateau, a strong gradient formed with surrounding regions, generating a disturbance that propagated eastward along the jet stream via Rossby waves. That triggered a Rossby wave train between the Tibetan Plateau and the Rocky Mountains. When the wave trains reached the northeastern Pacific Ocean, they broke.
“Over the eastern Pacific, the wave breaks — much like a towering ocean wave crashing near the shore,” Xue said. “This wave-breaking mechanism reduces static stability and significantly intensifies atmospheric rivers, ultimately driving extraordinary, heavy precipitation along the West Coast.”
The findings, published Wednesday in the journal Science Advances, are based on modeling and analyses of precipitation and surface temperature data.
Matthew Huber, a Purdue University professor not involved in the research, called the analysis a “very specific and impactful case study.” The results build on the idea that extra heat on a mountaintop affects Rossby waves almost as if the mountain had suddenly grown.
“You can imagine the waves in the jet are kind of like a motorcycle rider going off a jump,” Huber said. “How far and how high they jump depends on how fast they are going and how big a ramp they are going over.”
The models replicated the extreme weather with surprising accuracy, raising hopes the Tibetan Plateau could be integrated into early warning systems for the western U.S. “As similar, though less severe, events become more frequent and extreme weather escalates globally, understanding this teleconnection allows forecasting agencies to better warn coastal communities of impending extreme conditions,” Xue said.
Source: livescience.com
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