Simulations show increased ripple in the jet stream due to asymmetric increase in global temperatures

Simulations show increased ripple in the jet stream due to asymmetric increase in global temperatures

The stream function at an altitude of 850 mb. Credit: Woosok Moon, Baek-Min Kim, Gun-Hwan Yang and John Wettlaufer.

A quartet of researchers, two from the Nordic Institute for Theoretical Physics and two from Pukyong National University, created a set of simulations of jet stream changes under global warming. In their paper published in Proceedings of the National Academy of Sciencesthe group describes using mathematical theory to describe wind movement under given circumstances to create their simulations.

In the past few years, the jet stream has become more undulating than before. Both peaks and valleys have become more extreme. This led to changes in weather patterns – some places became wetter, others drier, and there were also more extended periods of heat and cold across the globe. In this new effort, the researchers suspected that the reason for the increased ripple is due to the asymmetrical increase in global temperatures. Global warming is warming the Arctic much faster than it is warming more southern areas. The result is large wind changes in the upper atmosphere.

To test their theory, the researchers used mathematical formulas to represent wind flow under historical patterns. They then added the impact of air heating, taking into account the differences above and below the jet stream. They used their formulas to simulate the flow of wind in the northern part of the planet that makes up the jet stream. The simulations showed what the researchers expected: more ripple.

More specifically, the researchers found that as conditions in the Arctic region warmed faster than regions further south, the winds surrounding the globe became weaker. This leads to amplified changes in the upper atmosphere. These changes exerted a fluctuating influence on the jet stream, resulting in not only larger crests and smaller troughs, but more waves overall. The result, they note, is less stability, along with an increase in extreme weather events, such as larger and stronger storms that can lead to damage and flooding, as well as droughts and long periods of warmer or cooler than average.

The jet stream isn’t getting “wavier” despite arctic warming

More information:
Woosok Moon et al., Wavier jet streams driven by zonally asymmetric surface thermal forcing, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2200890119

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