What is it about?
The strength of the winds in the Arctic stratosphere can be used to forecast the wintertime weather over Europe and North America, but we only have a few winters with reliable observations. We used a model to generate a large collection of 3000 possible winters, and we used these to examine different patterns of surface weather for winters with the strongest and weakest winds in the polar stratosphere. Our results indicate that the expected surface signatures are in fact not particularly common. Further, we find that it is not sufficient to know the state of the stratosphere; regional sea surface temperatures can either support or counteract the stratospheric influence on winter weather.
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Why is it important?
Some recent episodes, like the extremely cold winter in Northern Europe in 2010, have attracted wide attention, and there seems to be an anticipation that weak winds in the stratosphere are synonymous with cold weather in many regions. This can influence energy prices and other decisions, but we find that there are unexpectedly many cases where the opposite of the expected surface weather occurs. Our results highlight the need for probabilistic predictions and a nuanced analysis of confounding factors when using forecasts of the stratosphere for predicting surface winter weather.
Perspectives
This was the first time that we worked together as authors, and I learned a lot from coordinating the many interesting ideas and interpretations that the team generated. It was also very motivating for me to work on this topic, as we work with several energy companies in Climate Futures; the stratospheric polar vortex is an important predictor for them, in terms of both supply and demand of electricity.
Dr Erik W Kolstad
NORCE Norwegian Research Centre
The stratospheric polar vortex remains one of only a few predictors of weather on seasonal timescales, and as such, there is a need to better quantify and communicate inherent uncertainties in those predictions to end-users.
Amy Butler
National Oceanic and Atmospheric Administration
Every climate scientist wishes they had a larger observational sample size. While models always have their caveats, errors and uncertainties, it was eye-opening to be able to employ such a large set of simulations to "live the dream" of a sufficiently large sample so as to better understand the spread of possible outcomes relating to stratospheric variability. Hopefully, our results are useful to decision makers.
Dr Simon H. Lee
Columbia University
Read the Original
This page is a summary of: Diverse surface signatures of stratospheric polar vortex anomalies, Journal of Geophysical Research Atmospheres, October 2022, American Geophysical Union (AGU),
DOI: 10.1029/2022jd037422.
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