the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 24 Aug 2026
Long-lead Stratospheric Precursors of European Vegetation Dynamics and Crop Yield
Abstract. Modes of atmospheric variability in the North Atlantic are known to influence vegetation activity across Europe, yet it remains unclear whether they enable long-lead predictions of vegetation dynamics for several months ahead in time. Identifying such early precursors of vegetation phenology is essential for improving crop yield predictions under changing climatic conditions. Here, we show that the winter Northern Hemisphere stratospheric polar vortex (SPV), a well documented large-scale driver of European winter weather, influences vegetation dynamics across Europe from winter to summer. Comparing years characterized by weak and strong winter-mean SPV conditions in satellite-derived vegetation greenness, atmospheric reanalysis, and crop yield data, we identify two pathways through which the SPV shapes European summertime vegetation. First, the SPV directly modulates winter weather, with implications for vegetation in the early growing season that can persist into summer through lagged effects. Second, the winter SPV modulates the timing of springtime SPV breakdown, which in turn shifts probabilities of hazards to vegetation activity like frost after bud burst and soil moisture anomalies. In France's breadbasket region, weak wintertime SPV conditions delay growing season onset by up to three weeks relative to strong SPV conditions, while an associated delayed springtime SPV breakdown reduces the risk of soil moisture anomalies up to 100 %, increasing the summertime vegetation peak. Hence, nearly all weak SPV years in our record show positive winter and spring crop yield anomalies in this region. Conversely, strong wintertime SPV advances growing season onset, while the springtime SPV breakdown in these years increases risk of soil moisture extremes up to threefold, risking crop loss. Our results identify the winter SPV as a previously underappreciated long-lead precursor of vegetation and crop productivity anomalies in Europe, offering potential predictability several months ahead for agricultural applications.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2026-4689', Anonymous Referee #1, 18 Sep 2026
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RC2: 'Comment on egusphere-2026-4689', Anonymous Referee #2, 21 Oct 2026
Thank you for inviting me to review the paper titled “Long-lead Stratospheric Precursors of European Vegetation Dynamics and Crop Yield”.
First, I apologise for taking substantially more than two weeks to return this review.
This paper is important. In a changing climate, food security is increasingly likely to become a major issue if current crop types cannot adapt to changing near-surface conditions. Adaptation plans will be developed, of course, but any additional seasonal warnings or changes will become ever more useful in supporting the agricultural community.
The paper is fully data-led, which is always encouraging, identifying the behaviour of the winter SPV, and comparing it to multiple metrics of European greenness, crop yields and meteorological conditions.
The paper feels complete, following the clear paths of driver and then impact, across a very broad range of diagnostics (surface meteorology, phenology metrics, e.g. bud burst and frost, vegetation greenness).
My only main criticism is that the last “Conclusions and Outlook” section feels rushed and almost like an afterthought, especially given the word “Outlook” in the title. The findings of this paper have major implications, and the opportunity should be taken to explain these more strongly. This only requires a few extra sentences, or maybe a new paragraph. For instance.
- Observing the SPV offers a major opportunity to make seasonal probabilistic forecasts of the optimum time for European farmers to plan for their crops.
- The paper provides a fascinating teleconnection that others may wish to try to explain based on atmospheric processes.
- There also needs to be others who pick up on this analysis, and search for similar signals in ESMs. Does the teleconnection continue as greenhouse gases rise? Do the SPV impacts eventually get overwhelmed by direct climate change?
- Can further research clarify how the effect might be mediated by other known drivers of European climate (e.g. NAO state).
Hence, this last section should provide these pointers for where further research is needed.
In summary, this is a good paper with a clear message, and I could not find anything technically wrong. Below are a few further small suggested changes. I am very happy to see a further paper version.
Small things.
In the Section “Stratopsheric Polar Vortex metrics”, there is no statement about the dataset used. Presumably it is a diagnostic from ECMWF analyses?
In today’s world, where attention spans are short, high-impact diagrams with clear captions are very important. This is also true because people select them from PDFs and use them in PowerPoint presentations. For captions, if an acronym is spelt out in the text, it should not be spelt out again in a figure caption. However, this paper has an exceptionally large number of acronyms, so when looking at the figures, I continually had to search back in the text. Given the number of acronyms, maybe a small glossary/nomenclature table would help.
In Figure 1, the right-hand percentage table – I guess the colours have no statistical meaning; they are just there to allow differentiation between the table components?
The schematic in Figure 2 is useful, but the phrase “usually of opposite sign” is slightly vague. I wondered whether this schematic could be improved. Perhaps it could illustrate the two cases of SPV weak and SPV strong, and include colour-coded arrows that loop around the diagram to make it clear that SPV weak => X effective more positive => Y effect more positive, etc. (and similarly for SPV strong). Some of the IPCC report diagrams are like this and are very helpful.
I realise this would be substantial extra work, so it is only a suggestion, but could some sort of schematic be developed that shows the teleconnection? I could imagine a sphere as the globe, with the vortex shown as part of the atmosphere towards the top, and arrows then pointing towards Europe, illustrating the atmospheric connections (presumably via advected warm/cold air?). Alternatively, some sort of slight further enhancement of Figure 8 could help?
The diagrams are generally good and well presented, but please work through each one, as there is still room for improvement. For instance, in Figure 3, add a little more space between the columns and move the colourbars down slightly. In Figure 6, make the colourbar wider so it is consistent with the other figures. And again, in all cases, please ensure the caption is as complete as possible, so the figures can be interpreted in isolation.
Please make sure that the definition of weak SPV and strong SPV is clear, so people can assess what the middle range is (so, the middle range years would not contribute to the statistics in Figure 1b, or appear in either Figure 3 or Figure 4).
Citation: https://doi.org/10.5194/egusphere-2026-4689-RC2
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Please find my referee report attached. The manuscript addresses an interesting and potentially important topic, but several methodological and interpretative issues need to be addressed before the conclusions can be fully supported. Please see the attached report for my detailed comments and suggestions.