Resampling of ENSO teleconnections: accounting for cold season
evolution reduces uncertainty in the North Atlantic

King, M.; Li, Camille; Sobolowski, Stefan

doi:10.5194/wcd-2021-15

Cited by 4 publications

(6 citation statements)

References 18 publications

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“…Our results suggest that the timing of SSWs plays an important role for their surface impacts, with early winter SSWs being followed on average by stronger precipitation anomalies compared to late winter SSWs. Overall, this study thus contributes to a larger body of literature arguing that seasonal-mean analyses of teleconnections, and of stratosphere-troposphere coupling in particular, can blur over important details (Jiménez-Esteve and Domeisen, 2018;Kretschmer et al, 2018b;King et al, 2021). The reasons behind the role of SSW timing for the severity of the precipitation anomalies remains unclear.…”

Section: Discussionmentioning

confidence: 84%

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The role of the timing of sudden stratospheric warmings for precipitation and temperature anomalies in Europe

Monnin¹,

Kretschmer²,

Polichtchouk³

2022

Preprint

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The Northern Hemisphere stratospheric polar vortex (SPV), a band of fast westerly winds over the pole extending from approximately 10 to 50 km altitude, is a key driver of European winter weather.Extremely weak polar vortex states, so called sudden stratospheric warmings (SSW), are on average followed by dry and cold weather in Northern Europe, as well as wetter and warmer conditions in Southern Europe. However, the surface response of SSWs varies greatly between events, and it is not well understood which factors modulate this difference. Here we address the role of the timing of SSWs within the cold season (December to March) for the precipitation response in Europe. Due to the limited sample size of SSWs in the observational record, hindcasts of the seasonal forecasting model SEAS5 from the European Centre for Medium-Range Weather Forecasts (ECMWF) are analysed. We first evaluate key characteristics of stratosphere-troposphere coupling in SEAS5 against reanalysis data and find them to be reasonably well captured by the model, justifying our approach. We then show that in SEAS5, early winter (December and January) SSWs are followed by more pronounced tropospheric zonal wind and precipitation anomalies compared to late winter (February and March) SSWs. For example, in Scotland the low precipitation anomalies are roughly twice as severe after early winter SSWs than after late winter SSWs. The difference in the response cannot be explained by more downward propagating SSWs in early winter, or by different monthly precipitation climatologies. The role of SSW timing is potentially of use for forecasts and early warnings of European weather on subseasonal to seasonal timescales.

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Section: Discussionmentioning

confidence: 84%

“…For example, the influence of La Niña on the NAO is mostly observed during February but not during the other winter months (Jiménez-Esteve and Domeisen, 2018). Similarly, other recent work suggests that the North Atlantic response to ENSO in late autumn is different compared to mid-winter (King et al, 2021).…”

Section: Discussionmentioning

confidence: 87%

The role of the timing of sudden stratospheric warmings for precipitation and temperature anomalies in Europe

Monnin¹,

Kretschmer²,

Polichtchouk³

2022

Preprint

View full text Add to dashboard Cite

show abstract

“…More generally, this study contributes to a larger body of literature arguing that seasonal‐mean analyses of teleconnections, and of stratosphere–troposphere coupling in particular, can blur over important details (Jiménez‐Esteve and Domeisen, 2018; Kretschmer et al ., 2018a; King et al ., 2021). While differences in the monthly surface response to SSWs were here demonstrated to be the result of the SSW definition, other teleconnections and their seasonal dependencies might give further insights into European climate variability.…”

Section: Discussionmentioning

confidence: 99%

“…For example, the influence of La Niña on the NAO is mostly observed during February but not during the other winter months (Jiménez‐Esteve and Domeisen, 2018). Similarly, the North Atlantic response to ENSO in late autumn was proposed to be different compared to mid‐winter (King et al ., 2021). Understanding how these other mechanisms are related to our findings and contribute to differences in the surface response to SSWs is important but is beyond the scope of the present study.…”

Section: Discussionmentioning

confidence: 99%

“…The purpose of this study is to investigate whether the timing of a SSW within the cold season (from December to March) plays a role in the surface response. Such differences have been documented for other drivers of European weather and climate, such as the El Niño Southern Oscillation (Jiménez‐Esteve and Domeisen, 2018; King et al ., 2021), but have as of yet not been documented for SSWs. While SSWs are linked to a range of extreme events in different regions (Domeisen and Butler, 2020), here, we focus on anomalous temperature and precipitation in Europe.…”

Section: Introductionmentioning

confidence: 99%

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The role of the timing of sudden stratospheric warmings for precipitation and temperature anomalies in Europe

Monnin

Kretschmer

Polichtchouk

2021

Intl Journal of Climatology

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The Northern Hemisphere stratospheric polar vortex (SPV), a band of fast westerly winds over the Pole extending from approximately 10 to 50 km altitude, is a key driver of European winter weather. Extremely weak polar vortex states, so called sudden stratospheric warmings (SSWs), are on average followed by dry and cold weather in Northern Europe, as well as wetter weather in Southern Europe. However, the surface response of SSWs varies greatly between events, and it is not well understood which factors modulate this difference. Here, we address the role of the timing of SSWs within the cold season (December–March) for the temperature and precipitation response in Europe. Given the limited sample size of SSWs in the observations, hindcasts of the seasonal forecasting model SEAS5 from the European Centre for Medium‐Range Weather Forecasts are analysed. First, we evaluate key characteristics of stratosphere–troposphere coupling in SEAS5 against reanalysis data and find them to be reasonably well captured by the model, justifying our approach. We then show that in SEAS5, early winter (December and January) SSWs are followed by more pronounced surface impacts compared to late winter (February and March) SSWs. For example, in Scotland, the low precipitation anomalies are roughly twice as severe after early winter SSWs than after late winter SSWs. The difference in the response cannot be explained by more downward propagating SSWs in early winter, or by different monthly precipitation climatologies. Instead, we demonstrate that the differences result from stronger SPV anomalies associated with early winter SSWs. This is a statistical artefact introduced through the commonly used SSW event definition, which involves an absolute threshold, and, therefore, leads to stronger SPV anomalies during early winter SSWs when the stratospheric mean state is stronger. Our study highlights the sensitivity of surface impacts to SSW event definition.

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ENSO teleconnections and atmospheric mean state in idealised simulations

et al. 2022

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Understanding the natural and forced variability of the general circulation of the atmosphere and its drivers is one of the grand challenges in climate science. In particular, it is of paramount importance to understand to what extent the systematic error of global climate models affects the processes driving such variability. This is done by performing a set of simulations (ROCK experiments) with an intermediate complexity atmospheric model (SPEEDY), in which the Rocky Mountains orography is modified (increased or decreased) to influence the structure of the North Pacific jet stream. For each of these modified-orography experiments, the climatic response to idealized sea surface temperature (SST) anomalies of varying intensity in the El Niño Southern Oscillation (ENSO) region is studied. ROCK experiments are characterized by variations in the Pacific jet stream intensity whose extension encompasses the spread of the systematic error found in state-of-the-art climate models. When forced with ENSO-like idealised anomalies, they exhibit a non-negligible sensitivity in the response pattern over the Pacific North American region, indicating that a change/bias in the model mean state can affect the model response to ENSO. It is found that the classical Rossby wave train response generated by ENSO is more meridionally oriented when the Pacific jet stream is weaker, while it exhibits a more zonal structure when the jet is stronger. Rossby wave linear theory, used here to interpret the results, suggests that a stronger jet implies a stronger waveguide, which traps Rossby waves at a lower latitude, favouring a more zonally oriented propagation of the tropically induced Rossby waves. The shape of the dynamical response to ENSO, determined by changes in the intensity of the Pacific Jet, affects in turn the ENSO impacts on surface temperature and precipitation over Central and North America. Furthermore, a comparison of the SPEEDY results with CMIP6 models behaviour suggests a wider applicability of the results to more resources-demanding, complete climate GCMs, opening up to future works focusing on the relationship between Pacific jet misrepresentation and response to external forcing in fully-fledged GCMs.

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Resampling of ENSO teleconnections: accounting for cold season evolution reduces uncertainty in the North Atlantic

Cited by 4 publications

References 18 publications

The role of the timing of sudden stratospheric warmings for precipitation and temperature anomalies in Europe

The role of the timing of sudden stratospheric warmings for precipitation and temperature anomalies in Europe

The role of the timing of sudden stratospheric warmings for precipitation and temperature anomalies in Europe

ENSO teleconnections and atmospheric mean state in idealised simulations

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