Last Updated on June 1, 2026 by Staff
Over the few decades many parts of the Northern Hemisphere have seen more frequent and intense extreme weather events. We have had heat waves, heavy rainfall, floods and prolonged droughts. This has raised concerns among scientists and policymakers. Climate change is a factor behind these changes. Researchers are still trying to understand the exact atmospheric processes that contribute to severe weather patterns.
A new study from Harvard University’s John A. Paulson School of Engineering and Applied Sciences has challenged one of the theories often used to explain extreme weather events. The findings suggest that a popular atmospheric mechanism may not be responsible for the increase in weather as previously believed.
Rossby Waves Explained
The theory centers on waves, which are large-scale meanders in the jet stream. The jet stream is a moving current of air high in the atmosphere that separates cold polar air from warmer tropical air. Rossby waves naturally influence weather patterns around the globe.
When Rossby waves become stationary or move slowly they can cause weather systems to remain in one location for extended periods. This can lead to heat waves, heavy rainfall, droughts or flooding. Because of their influence on weather scientists have spent years studying how Rossby waves behave and what factors cause them to intensify.
Rossby waves are important to understand because they can help us predict weather events.
One explanation that has gained attention is called Quasiresonant Amplification. According to this theory certain wind patterns in the atmosphere can amplify waves making them larger and more persistent. As a result extreme weather events may become more likely.
This theory has been used to explain extreme weather events.
Testing The Theory
To investigate whether Quasiresonant Amplification truly plays a role in extreme weather Harvard researchers conducted a detailed analysis using a simplified atmospheric model. The model was designed to represent large-scale atmospheric fluid dynamics while removing additional complexities such as moisture, clouds and detailed heating effects.
The researchers used this model to test the Quasiresonant Amplification theory.
Research associate Todd Mooring specifically created conditions in the model that should have favored the amplification of waves according to Quasiresonant Amplification theory. The goal was to observe whether the Rossby waves actually became stronger under those circumstances.
The researchers then compared Rossby wave behavior during periods predicted to be favorable for amplification with periods considered unfavorable. This allowed them to directly test one of the predictions of the Quasiresonant Amplification hypothesis.
Surprising Findings
The results were unexpected. By producing larger and more powerful Rossby waves the supposedly favorable conditions generated smaller Rossby waves. This outcome was the opposite of what the Quasiresonant Amplification theory predicts.
According to the researchers if the Quasiresonant Amplification theory were correct the atmospheric Rossby waves should have become significantly stronger when the required wind configurations were present. However the model consistently showed reduced wave amplitudes.
Because the atmospheric model used in the study is more realistic than the simplified equations on which Quasiresonant Amplification theory was originally based, the researchers believe these findings raise important questions about the validity of the Quasiresonant Amplification theory.
The study does not claim that Rossby waves are unimportant. Rather it suggests that the specific mechanism of Quasiresonant Amplification may not be capable of explaining many of the weather events that have been attributed to it in recent years.
Rossby waves are still an area of study.
Looking Ahead
The researchers emphasize that climate change remains a driver of many extreme weather events. Rising global temperatures continue to increase the likelihood of heat waves, heavy precipitation and other climate-related hazards.
Climate change is a factor in extreme weather events.
However the study highlights the need for caution when linking atmospheric theories to real-world weather disasters. The Earth’s climate system is complex and extreme weather often results from multiple interacting factors rather than a single mechanism.
Assistant Professor Marianna Linz noted that clear and definitive claims about weather patterns may sometimes oversimplify reality. The findings encourage scientists to continue exploring explanations and improving climate models to better understand how extreme events develop.
Ultimately the research serves as a reminder that scientific understanding evolves over time. By questioning existing assumptions and testing theories rigorously researchers can develop accurate explanations for the growing challenges posed by extreme weather in a changing climate.
This study is a step in understanding extreme weather events.