The Role of the Stratosphere in Subseasonal to Seasonal Prediction: 2. Predictability Arising From Stratosphere‐Troposphere Coupling

Domeisen, Daniela I. V.; Butler, Amy H.; Charlton‐Perez, Andrew; Ayarzagüena, Blanca; Baldwin, Mark P.; Dunn‐Sigouin, Etienne; Furtado, Jason C.; Garfinkel, Chaim I.; Hitchcock, Peter B.; Karpechko, Alexey Yu.; Kim, Hera; Knight, Jeff; Lang, Alex H.; Lim, Eun‐Pa; Marshall, Andrew G.; Roff, Greg; Schwartz, Chen; Simpson, Isla R.; Son, Seok‐Woo; Taguchi, Masakazu

doi:10.1029/2019jd030923

Cited by 180 publications

(185 citation statements)

References 132 publications

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“…Europe (from a lag of 20 days onwards) and later shifting towards Scandinavia. This is in stark contrast to the negative NAO and the associated cold conditions that are commonly expected as the canonical response to SSWs over Europe (Butler et al, 2017;Kolstad et al, 2010;Domeisen et al, 2019a).…”

Section: Consistent Withmentioning

confidence: 82%

The role of North Atlantic-European weather regimes in the surface impact of sudden stratospheric warming events

Domeisen¹,

Grams²,

Papritz³

2020

Preprint

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<p><strong>Abstract.</strong> Sudden stratospheric warming (SSW) events can significantly impact tropospheric weather for a period of several weeks, in particular over the North Atlantic and Europe. However, not all SSW events exhibit the same tropospheric response, if any, and it remains an open question what determines the existence, location, timing, and strength of the downward impact. We here explore the role of the state of the tropospheric flow in the North Atlantic region at the onset of SSW events for determining the subsequent surface impact. A refined definition of seven North Atlantic tropospheric weather regimes indicates the Greenland blocking (GL) and Atlantic Trough (AT) regimes as the most frequent large-scale patterns following the weeks after an SSW. While GL is dominated by high pressure over Greenland, AT is dominated by a southeastward shifted storm track in the North Atlantic. We find that a blocking situation over western Europe and the North Sea (European Blocking) at the time of the SSW onset favours the GL response and the associated cold conditions over Europe. In contrast, an AT response and mild conditions are more likely if GL occurs already at SSW onset. For the remaining tropospheric flow regimes during SSW onset, we find no clear response. The results indicate that the tropospheric impact of SSW events critically depends on the tropospheric state during the onset of the SSW, which could provide crucial guidance for subseasonal prediction.</p>

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Section: Consistent Withmentioning

confidence: 82%

The role of North Atlantic-European weather regimes in the surface impact of sudden stratospheric warming events

Domeisen¹,

Grams²,

Papritz³

2020

Preprint

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“…5a. However, the WCR is not a common precursor of SSWs (Domeisen et al 2020), and Karpechko (2018) found that this SSW was only predictable up to 10 days in advance in the ECMWF model. There was also no obvious subsequent impact of the SSW on our North American weather regimes in February-March 2009.…”

Section: Subseasonal Forecast Evolutionmentioning

confidence: 95%

Toward Identifying Subseasonal Forecasts of Opportunity Using North American Weather Regimes

Robertson

Vigaud

Yuan

et al. 2020

Monthly Weather Review

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Large-scale atmospheric circulation regime structures are used to diagnose subseasonal forecasts of wintertime geopotential height fields over the North American sector, from the NCEP CFSv2 model. Four large-scale daily circulation regimes derived from reanalysis 500-hPa geopotential height data using K-means clustering are used as a low-dimensional basis for diagnosing the model’s forecasts up to 45 days ahead. On average, hindcast skill in regime space is found to be limited to 10–15 days ahead, in terms of anomaly correlation of 5-day averages of regime counts, over the 1999–2010 period. However, skill up to 30 days ahead is identified in individual winters, and intraseasonal episodes of high skill are identified using a forecast-evolution graphical tool. A striking vacillation between the West Coast and Pacific ridge patterns during December–January 2008/09 is shown to be predicted 20–25 days in advance, illustrating the possibility to identify “forecasts of opportunity” when subseasonal forecast skill is much higher than the average. The forecast-evolution tool also provides insight into the poor seasonal forecasts of California precipitation by operational centers during the 2015/16 El Niño winter. The Pacific trough regime is shown to be greatly overpredicted beyond 1–2 weeks in advance during the 2015/16 winter, with weather-scale features dominating the forecast evolution at shorter lead times. A similar though less extreme situation took place during the weaker El Niño of 2009/10, with the Pacific trough overforecast at S2S lead times.

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“…Hence, there are several opportunities yet to explore in further work related to atmospheric probing and data assimilation using infrasound datasets. A long-term objective is to enhance or constrain the representation of stratospheric winds in global models, thereby contributing to enhanced surface weather predictions on subseasonal-to-seasonal time-scales (Domeisen et al, 2020a;2020b).…”

Section: Summary and Future Workmentioning

confidence: 99%

Assimilation of atmospheric infrasound data to constrain tropospheric and stratospheric winds

Amezcua

Näsholm

Blixt

et al. 2020

Quart J Royal Meteoro Soc

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This data assimilation study exploits infrasound from explosions to probe an atmospheric wind component from the ground up to stratospheric altitudes. Planned explosions of old ammunition in Finland generate transient infrasound waves that travel through the atmosphere. These waves are partially reflected back towards the ground from stratospheric levels, and are detected at a receiver station located in northern Norway at 178 km almost due north from the explosion site. The difference between the true horizontal direction towards the source and the backazimuth direction (the horizontal direction of arrival) of the incoming infrasound wavefronts, in combination with the pulse propagation time, are exploited to provide an estimate of the average cross‐wind component in the penetrated atmosphere. We perform offline assimilation experiments with an ensemble Kalman filter and these observations, using the ERA5 ensemble reanalysis atmospheric product as background (prior) for the wind at different vertical levels. We demonstrate that information from both sources can be combined to obtain analysis (posterior) estimates of cross‐winds at different vertical levels of the atmospheric slice between the explosion site and the recording station. The assimilation makes greatest impact at the 12–60 km levels, with some changes with respect to the prior of the order of 0.1–1.0 m·s−1, which is a magnitude larger than the typical standard deviation of the ERA5 background. The reduction of background variance in the higher levels often reached 2–5%. This is the first published study demonstrating techniques to implement assimilation of infrasound data into atmospheric models. It paves the way for further exploration in the use of infrasound observations – especially natural and continuous sources – to probe the middle atmospheric dynamics and to assimilate these data into atmospheric model products.

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The Role of the Stratosphere in Subseasonal to Seasonal Prediction: 2. Predictability Arising From Stratosphere‐Troposphere Coupling

Cited by 180 publications

References 132 publications

The role of North Atlantic-European weather regimes in the surface impact of sudden stratospheric warming events

The role of North Atlantic-European weather regimes in the surface impact of sudden stratospheric warming events

Toward Identifying Subseasonal Forecasts of Opportunity Using North American Weather Regimes

Assimilation of atmospheric infrasound data to constrain tropospheric and stratospheric winds

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