Planetary Waves Controlling the Effect of Energetic Electron Precipitation on the Northern Polar Vortex

Salminen, Antti; Asikainen, Timo; Мурсула, К.

doi:10.1029/2021gl097076

Cited by 7 publications

(16 citation statements)

References 43 publications

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“…Here, less SSWs where observed during high A p winters when the QBO at the 30 hPa level in August, September and October was in the easterly phase. As SSWs are driven by planetary wave activity, Salminen et al (2022) have further investigated the EPP influence for different latitudinal planetary wave propagation patterns. The study found that EPP induced wave-mean-flow interactions have a stronger influence when more planetary waves propagate at mid latitudes (50°-52.5°) than at polar latitudes (70°-72.5°).…”

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confidence: 99%

Effects of Energetic Particle Precipitation on Stratospheric Temperature During Disturbed Stratospheric Polar Vortex Conditions

2023

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Recently, observational and re‐analysis studies have outlined potentially enhanced influence of Energetic Particle Precipitation (EPP) either at times preceding Sudden Stratospheric Warmings (SSW) or when the distribution of planetary wave activity is suitable. In addition, significant correlations have been found between EPP and the occurrence rate of SSWs when the phases of the Quasi‐Biennial Oscillation (QBO) are taken into account. Here we study the influence of EPP during disturbed stratospheric polar vortex conditions using chemistry‐climate model SOCOL‐MPIOM3 over the 20th century. When classifying disturbed conditions, the definition of minor SSWs are utilized along with a temperature gradient (day‐to‐day variations) criteria at 90°N and 10 hPa acting as a measure of the strength of the events. We find no influence of EPP on the occurrence rate of disturbed conditions over the last 100 year period. However, conditions preceding and during the disturbances are significantly different when EPP forcing is included into the model. This is especially true for stratospheric disturbances occurring in February. Furthermore, there is a clear tendency that the EPP effect becomes more notable after the 1950s. Our results imply that EPP forcing could be important for the stratospheric conditions during winter and that pre‐conditioning forced by atmospheric disturbances are an important factor when considering how the mechanism operates.

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confidence: 99%

Effects of Energetic Particle Precipitation on Stratospheric Temperature During Disturbed Stratospheric Polar Vortex Conditions

2023

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“…In mid‐winter, this results in cooler mesosphere and upper stratosphere due to increased infrared radiative cooling (Sinnhuber et al., 2018) and by the following dynamical impact to warmer lower stratosphere (Salminen et al., 2019) and weaker than average polar vortex with more frequent SSWs compared to the average occurrence rate under the easterly QBO. The EEP influence on the polar vortex is known to preferentially occur, when the planetary wave activity to the vortex is suitably enhanced, for example, during easterly QBO phase (Asikainen et al., 2020; Salminen et al., 2022). On the other hand, the geomagnetic activity influence on SSW probability can also be interpreted so that in QBO‐E larger than average geomagnetic activity (EEP) strengthens the polar vortex and makes it less prone to SSWs.…”

Section: Discussionmentioning

confidence: 99%

“…Increased adiabatic heating related to the BDC associated downwelling at high latitudes in QBO‐E also contributes to weakening of the vortex. Recent studies have shown that the weaker vortex associated with planetary wave forcing favors wave‐mean‐flow interactions by which the energetic electron precipitation can affect the polar vortex dynamics (Asikainen et al., 2020; Salminen et al., 2019, 2022). The exact reason why the QBO time lag from August to the winter season seems to be relevant for the EEP effect on the vortex warrants a more detailed study.…”

Section: Geomagnetic Activity Effect On Ssw Occurrencementioning

confidence: 99%

“…These thermal changes intensify the polar vortex, which has been confirmed by observations (Lu et al., 2008; Salminen et al., 2019; Seppälä et al., 2013) and by models (Arsenovic et al., 2016; Baumgaertner et al., 2011; Rozanov et al., 2005). Recent studies have also shown that planetary wave activity which is suitably located with respect to the polar vortex is essential in order to allow the EEP effect on the polar vortex to take place (Asikainen et al., 2020; Salminen et al., 2022). One of the consequences of this is that the EEP influence on the polar vortex is predominantly observed during easterly phase of the QBO, when more planetary wave activity is concentrated into the polar region (Salminen et al., 2019).…”

Section: Introductionmentioning

confidence: 99%

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Long‐Term Prediction of Sudden Stratospheric Warmings With Geomagnetic and Solar Activity

et al. 2023

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The polar vortex is a strong jet of westerly wind which forms each winter around the polar stratosphere. Sometimes, roughly every other winter, the polar vortex in the Northern Hemisphere experiences a dramatic breakdown and associated warming of the polar stratosphere. Such events are called sudden stratospheric warmings (SSWs) and they are known to have a significant influence on ground weather in Northern Eurasia and large parts of North America. Typically, these events are thought to occur due to planetary waves propagating to the stratosphere where they may disrupt the vortex. Here, we show that the SSW probability depends significantly on a favorable combination of geomagnetic and solar activity and the phase of the Quasi‐Biennial Oscillation (QBO). Using logistic regression models, we find that more SSWs occur when early‐winter geomagnetic activity (aa index) is low and QBO winds are easterly and when solar activity (F10.7 index) is high and QBO winds are westerly. We then examine the possibility of using these results to predict the occurrence probability of SSWs with several months lead time and evaluate the optimal lead times for all variables using cross‐validation methods. As a result, we find that the SSW probability can be predicted rather well and we can issue a probabilistic SSW prediction for the coming winter season with a success ratio of about 86% already in the preceding August. The results presented here are an important step toward improving the seasonal predictability of wintertime weather using information about solar and geomagnetic activity.

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“…Based on the previous research results, there is indeed a signal of GA in the atmospheric circulation in the NH, and planetary wave-mean flow interactions may be key to linking GA and dynamic response in the stratosphere (Lu et al, 2008;Salminen et al, 2022). Planetary waves are disturbances mostly originating from the Earth's surface, propagating in the westerly flow and inputting the easterly momentum, thereby, dissipating and decelerating the background flow.…”

mentioning

confidence: 94%

Influence of geomagnetic activity on the southern atmosphere and its cross‐seasonal association with SAM

Luo,

Qin,

Huang

et al. 2023

Intl Journal of Climatology

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This study investigates the interannual cross‐seasonal association between the winter energetic particle precipitation, which is related to the geomagnetic activity (GA), and the southern annular mode (SAM) in the following summer by employing the ERA5 reanalysis dataset. The results reveal a marked negative correlation between these variables on an interannual timescale. Therefore, we analyse the GA signatures in the southern atmosphere and find that the evolution of SAM to the negative phase driven by GA may be caused by the following two mechanisms: First, for high GA levels, the middle and lower stratospheric polar vortex becomes weaker from October to November, with considerable changes in the stratospheric thermal structure and more anomalous planetary wave upwelling, accompanied by weakening of the circumpolar westerly. Over time, the anomalous signal from the upper layer can be transmitted downward and is conducive to inducing and strengthening the negative SAM in the following summer, which may serve as the stratospheric pathway for the geomagnetic impact on the SAM and Southern Hemisphere (SH) climate. Second, another possible way is that the preceding GA also appreciably regulates negative anomalies in the Ferrel circulation in SH, implying poleward anomalies in the direction of the pressure gradient, which promotes the development and enhancement of the negative phase of the SAM. In addition, easterly quasi‐biennial oscillation conditioning plays a positive role in the response of the southern atmosphere to geomagnetic forcing, thereby strengthening the connection between them.

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Planetary Waves Controlling the Effect of Energetic Electron Precipitation on the Northern Polar Vortex

Cited by 7 publications

References 43 publications

Effects of Energetic Particle Precipitation on Stratospheric Temperature During Disturbed Stratospheric Polar Vortex Conditions

Effects of Energetic Particle Precipitation on Stratospheric Temperature During Disturbed Stratospheric Polar Vortex Conditions

Long‐Term Prediction of Sudden Stratospheric Warmings With Geomagnetic and Solar Activity

Influence of geomagnetic activity on the southern atmosphere and its cross‐seasonal association with SAM

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