Ontwikkeling van de QBO, zonneactiviteit, ENSO, MJO en de winter 2020/2021

[Sebastiaan]

Uit https://www.aer.com/science-research/cl ... cillation/

[Sebastiaan]

https://twitter.com/antmasiello/status/ ... 25/photo/1

[Gert]

Sebastiaan. Even langs deze weg. Een prachtig artikel van jou weer in Weerspiegel. Fijn om te lezen. Veel waardering voor de VWK-leden die nadenken over de teleconnecties in het weer. Wees er bewust van dat jullie veel kennis op dit gebied hebben. Misschien leuk om een reeks artikelen in Weerspiegel te plaatsen waarin jullie deze kennis delen. Als oud-redacteur weet ik dat het veel tijd kost maar als het zou kunnen dan wordt dat door velen gewaardeerd. Nogmaals mijn complimenten

[Sebastiaan]

Dank Gert. Ik sluit niks uit

Bericht van Antony http://twitter.com/antmasiello/status/1 ... 1621685257

[Sebastiaan]

EC en nog twee modellen qua 10 hPa. EC gunstigst.

[Sebastiaan]

Stratosphere–troposphere coupling is often viewed from the perspective of the annular modes and their dynamics. Despite the obvious benefits of this approach, recent work has emphasised the greater tropospheric sensitivity to stratospheric variability in the Atlantic basin than in the Pacific basin. In this study, a new approach to understanding stratosphere–troposphere coupling is proposed, with a focus on the influence of the stratospheric state on North Atlantic weather regimes (during extended winter, November to March). The influence of the strength of the lower‐stratospheric vortex on four commonly used tropospheric weather regimes is quantified. The negative phase of the North Atlantic Oscillation is most sensitive to the stratospheric state, occurring on 33% of days following weak vortex conditions but on only 5% of days following strong vortex conditions. An opposite and slightly weaker sensitivity is found for the positive phase of the North Atlantic Oscillation and the Atlantic Ridge regime. For the North Atlantic Oscillation regimes, stratospheric conditions change both the probability of remaining in each regime and the probability of transitioning to that regime from others. A logistic regression model is developed to further quantify the sensitivity of tropospheric weather regimes to the lower stratospheric state. The logistic regression model predicts an increase of 40–60% in the probability of transition to the negative phase of the North Atlantic Oscillation for a one standard deviation reduction in the strength of the stratospheric vortex. Similarly it predicts a 10–30% increase in the probability of transition to the positive phase of the North Atlantic Oscillation for a one standard deviation increase in the strength of the stratospheric vortex. The stratosphere–troposphere coupling in the European Centre for Medium‐range Weather Forecasts Integrated Forecasting System model is found to be consistent with the re‐analysis data by fitting the same logistic regression model.
https://rmets.onlinelibrary.wiley.com/d ... 02/qj.3280

[Karel]

Sebastiaan hier vind je voorgaand artikel in zijn geheel http://centaur.reading.ac.uk/76031/1/ch ... me_rev.pdf

[Paul]

MJO animatie (hoop dat hij werkt)

https://publish.twitter.com/?query=http ... dget=Tweet

[Karel]

Stratosphere–troposphere coupling is often viewed from the perspective of the annular modes and their dynamics. Despite the obvious benefits of this approach, recent work has emphasised the greater tropospheric sensitivity to stratospheric variability in the Atlantic basin than in the Pacific basin. In this study, a new approach to understanding stratosphere–troposphere coupling is proposed, with a focus on the influence of the stratospheric state on North Atlantic weather regimes (during extended winter, November to March). The influence of the strength of the lower‐stratospheric vortex on four commonly used tropospheric weather regimes is quantified. The negative phase of the North Atlantic Oscillation is most sensitive to the stratospheric state, occurring on 33% of days following weak vortex conditions but on only 5% of days following strong vortex conditions. An opposite and slightly weaker sensitivity is found for the positive phase of the North Atlantic Oscillation and the Atlantic Ridge regime. For the North Atlantic Oscillation regimes, stratospheric conditions change both the probability of remaining in each regime and the probability of transitioning to that regime from others. A logistic regression model is developed to further quantify the sensitivity of tropospheric weather regimes to the lower stratospheric state. The logistic regression model predicts an increase of 40–60% in the probability of transition to the negative phase of the North Atlantic Oscillation for a one standard deviation reduction in the strength of the stratospheric vortex. Similarly it predicts a 10–30% increase in the probability of transition to the positive phase of the North Atlantic Oscillation for a one standard deviation increase in the strength of the stratospheric vortex. The stratosphere–troposphere coupling in the European Centre for Medium‐range Weather Forecasts Integrated Forecasting System model is found to be consistent with the re‐analysis data by fitting the same logistic regression model.
https://rmets.onlinelibrary.wiley.com/d ... 02/qj.3280

In voorgaand onderzoek wordt de relatie tussen het heersende Atlantisch/Europees weerregime en de uitwerking van een SSW niet direct aangegeven. Recent aug 2020 is een onderzoek gepubliceerd waar dat is gebeurd.
The role of North Atlantic–European weather regimes in the surface impact of sudden stratospheric warming events by Daniela I. V. Domeisen1, Christian M. Grams, and Lukas Papritz https://wcd.copernicus.org/articles/1/3 ... 3-2020.pdf
Uit dit artikel de samenvatting en enige toespitsing op de conclusies met behulp van een tweetal figuren.



''Abstract.
Sudden stratospheric warming (SSW) events can significantly impact tropospheric weather for a period ofseveral weeks, in particular in the North Atlantic–European(NAE) region. While the stratospheric forcing often projects onto the North Atlantic Oscillation (NAO), the tropospheric response to SSW events, if any, is highly variable, and what determines the existence, location, timing, and strength of the downward impact remains an open question. We here explore how the variable tropospheric response to SSW events in the NAE region can be characterized in terms of a refined set of seven weather regimes and if the tropospheric flow in the North Atlantic region around the onset of SSW events is an indicator of the subsequent downward impact.The weather regime analysis reveals the Greenland blocking(GL) and Atlantic trough (AT) regimes as the most frequent large-scale patterns in the weeks following an SSW. Whilethe GL regime is dominated by high pressure over Green -land, AT is dominated by a southeastward-shifted storm track in the North Atlantic. The flow evolution associated with GL and the associated cold conditions over Europe in the weeks following an SSW occur most frequently if a blocking situation over western Europe and the North Sea (European blocking) prevailed around the SSW onset. In contrast, an AT regime associated with mild conditions over Europe is more likely following the SSW event if GL occurs already around SSW onset. For the remaining tropospheric flow regimes during SSW onset we cannot identify a dominant flow evolution. Although it remains unclear what causes these relationships, the results suggest that specific tropospheric states in the days around the onset of the SSW are an indicator of the subsequent tropospheric flow evolution in the aftermath of anSSW, which could provide crucial guidance for subseasonal prediction ''


"Three of the seven regimes are dominated by a cyclonic 500 hPa geopotential height anomaly (“cyclonic regimes”;see Fig. A1a–c): the Atlantic trough (AT) regime with cy-clonic activity shifted towards western Europe, the zonal regime (ZO), and the Scandinavian trough (ScTr) regime.The remaining four regimes are dominated by a positive geopotential height anomaly and are referred to as “blockedregimes” : Atlantic ridge (AR), European block-ing (EuBL), Scandinavian blocking (ScBL), and Greenland blocking (GL).A potential modulation of the frequency of occurrence of the seven regimes can be understood in terms of the link between the respective regimes and the NAO . While ZO and ScTr project onto NAO+, GL strongly projects onto NAO−. EuBL and ATdo not project strongly onto either NAO phase"

"Our conclusions areas follows:
1. In the aftermath of an SSW event, the tropospheric flow in the NAE region exhibits an evolution that is unlikely to occur in the absence of an SSW. Specifically, positive geopotential height anomalies related to Greenland blocking are statistically more likely to occur after the onset of the SSW than in the absence of an SSW. This is consistent with the expected (canonical) negative NAO response of the troposphere to SSWs (e.g., Charlton-Perez et al., 2018).
2. The significant and robust positive geopotential height anomalies found in the period 10–60 d after SSWs are predominantly the result of SSWs with European blocking dominating around their onset. This is manifestedfor this subset of events in a transition from EuBL to GL that then dominates at lags of 15–20 and 30–55 d after the SSW onset, which is statistically significantly different from the natural progression from EuBL to GL
These events all correspond to SSWs that have in the literature been classified as having a tropospheric response (e.g., Karpechko et al., 2017). For other tropospheric regimes at SSW onset the tropospheric response is weaker and less robust and significant.
3. For Greenland blocking at the SSW onset, a weak preference for cyclonic flow regimes around 20–30 d after the SSW is apparent, with an opposite surface response in the aftermath of the SSW as compared to SSW onsets dominated by EuBL. These events almost exclusively correspond to SSWs that have in the literature been classified as having no tropospheric response.
4. SSWs that occur during cyclonic weather regimes exhibit a considerably weaker and less significant response as compared to SSW events associated withEuBL, with a modestly enhanced likelihood for GL. ''

[Sebastiaan]

Dank Karel.

Sneeuwdekupdate.