How heat on the Tibetan Plateau fuels powerful storms in California, half a world away
A new study connects early winter heat high up on the plateau to the jet stream and, ultimately, storms headed for the US coast. The results could mean better forecasts.
In February 2024, heavy rain from an atmospheric river caused the Los Angeles River to overflow its banks, a rare event for the normally dry waterway. This phenomenon may seem distant from the Tibetan Plateau, but research reveals a surprising link between the two regions. Our team of atmospheric scientists has uncovered how warming temperatures on the high-altitude Tibetan Plateau can trigger powerful storms in California, thousands of miles away.
California experienced record-breaking precipitation during the winters of 2016-2017 and 2022-2023, leading to severe flooding and damage to infrastructure. While these stormy winters fell during La Niña conditions, typically associated with drier California winters, they were particularly intense. La Niña and its cooler counterpart, El Niño, are two extremes of the El Niño-Southern Oscillation climate pattern, driven by ocean temperatures.
However, ocean-based events like these do not fully explain the extreme precipitation events in California.
Our study suggests that unusually warm land temperatures over the Tibetan Plateau in early winter can create atmospheric conditions that lead to stronger atmospheric rivers along the U.S. Pacific Coast later in the season, increasing the risk of extreme precipitation in California and surrounding areas. By analyzing observations, we found a significant statistical relationship between early-winter land temperatures on the Tibetan Plateau and late-winter precipitation in California.
To confirm this link, we used climate-model experiments to test whether warming on the Tibetan Plateau could actually cause the precipitation extremes over 7,200 miles away. When the global Earth system model was driven by sea-surface temperatures alone, it did not reproduce the observed warming on the plateau or the extreme precipitation in California.
However, when we incorporated observed Tibetan Plateau land temperatures as an initial condition in the model, it successfully reproduced both the early-winter warming on the plateau and the late-winter precipitation in California. The Tibetan Plateau, covering most of southwest China and parts of neighboring countries, is an enormous and extremely high-elevation region, averaging 14,800 feet above sea level.
When its land surface becomes unusually warm, it heats the atmosphere above it, altering temperature differences between the plateau and surrounding regions. This change in atmospheric conditions can set off a chain reaction, ultimately fueling powerful atmospheric rivers that bring heavy rainfall and snow to California.
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