Jet Latitude Regimes and the Predictability of the North Atlantic Oscillation
In recent years, numerical weather prediction models have begun to show notable levels of skill at predicting the average winter North Atlantic Oscillation (NAO) when initialised one month ahead. At the same time, these model predictions exhibit unusually low signal-to-noise ratios, in what has been...
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ftdatacite:10.48550/arxiv.1910.00864 2023-05-15T17:30:11+02:00 Jet Latitude Regimes and the Predictability of the North Atlantic Oscillation Strommen, Kristian 2019 https://dx.doi.org/10.48550/arxiv.1910.00864 https://arxiv.org/abs/1910.00864 unknown arXiv https://dx.doi.org/10.1002/qj.3796 arXiv.org perpetual, non-exclusive license http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Atmospheric and Oceanic Physics physics.ao-ph Chaotic Dynamics nlin.CD FOS Physical sciences article-journal Article ScholarlyArticle Text 2019 ftdatacite https://doi.org/10.48550/arxiv.1910.00864 https://doi.org/10.1002/qj.3796 2022-03-10T16:15:01Z In recent years, numerical weather prediction models have begun to show notable levels of skill at predicting the average winter North Atlantic Oscillation (NAO) when initialised one month ahead. At the same time, these model predictions exhibit unusually low signal-to-noise ratios, in what has been dubbed a `signal-to-noise paradox'. We analyse both the skill and signal-to-noise ratio of the Integrated Forecast System (IFS), the European Center for Medium-range Weather Forecasts (ECMWF) model, in an ensemble hindcast experiment. Specifically, we examine the contribution to both from the regime dynamics of the North Atlantic eddy-driven jet. This is done by constructing a statistical model which captures the predictability inherent to to the trimodal jet latitude system, and fitting its parameters to reanalysis and IFS data. Predictability in this regime system is driven by interannual variations in the persistence of the jet latitude regimes, which determine the preferred state of the jet. We show that the IFS has skill at predicting such variations in persistence: because the position of the jet strongly influences the NAO, this automatically generates skill at predicting the NAO. We show that all of the skill the IFS has at predicting the winter NAO over the period 1980-2010 can be attributed to its skill at predicting regime persistence in this way. Similarly, the tendency of the IFS to underestimate regime persistence can account for the low signal-to-noise ratio, giving a possible explanation for the signal-to-noise paradox. Finally, we examine how external forcing drives variability in jet persistence, as well as highlight the role played by transient baroclinic eddy feedbacks to modulate regime persistence. : Submitted to the Quarterly Journal of the Royal Meteorological Society (October 2019) Article in Journal/Newspaper North Atlantic North Atlantic oscillation DataCite Metadata Store (German National Library of Science and Technology) |
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DataCite Metadata Store (German National Library of Science and Technology) |
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topic |
Atmospheric and Oceanic Physics physics.ao-ph Chaotic Dynamics nlin.CD FOS Physical sciences |
spellingShingle |
Atmospheric and Oceanic Physics physics.ao-ph Chaotic Dynamics nlin.CD FOS Physical sciences Strommen, Kristian Jet Latitude Regimes and the Predictability of the North Atlantic Oscillation |
topic_facet |
Atmospheric and Oceanic Physics physics.ao-ph Chaotic Dynamics nlin.CD FOS Physical sciences |
description |
In recent years, numerical weather prediction models have begun to show notable levels of skill at predicting the average winter North Atlantic Oscillation (NAO) when initialised one month ahead. At the same time, these model predictions exhibit unusually low signal-to-noise ratios, in what has been dubbed a `signal-to-noise paradox'. We analyse both the skill and signal-to-noise ratio of the Integrated Forecast System (IFS), the European Center for Medium-range Weather Forecasts (ECMWF) model, in an ensemble hindcast experiment. Specifically, we examine the contribution to both from the regime dynamics of the North Atlantic eddy-driven jet. This is done by constructing a statistical model which captures the predictability inherent to to the trimodal jet latitude system, and fitting its parameters to reanalysis and IFS data. Predictability in this regime system is driven by interannual variations in the persistence of the jet latitude regimes, which determine the preferred state of the jet. We show that the IFS has skill at predicting such variations in persistence: because the position of the jet strongly influences the NAO, this automatically generates skill at predicting the NAO. We show that all of the skill the IFS has at predicting the winter NAO over the period 1980-2010 can be attributed to its skill at predicting regime persistence in this way. Similarly, the tendency of the IFS to underestimate regime persistence can account for the low signal-to-noise ratio, giving a possible explanation for the signal-to-noise paradox. Finally, we examine how external forcing drives variability in jet persistence, as well as highlight the role played by transient baroclinic eddy feedbacks to modulate regime persistence. : Submitted to the Quarterly Journal of the Royal Meteorological Society (October 2019) |
format |
Article in Journal/Newspaper |
author |
Strommen, Kristian |
author_facet |
Strommen, Kristian |
author_sort |
Strommen, Kristian |
title |
Jet Latitude Regimes and the Predictability of the North Atlantic Oscillation |
title_short |
Jet Latitude Regimes and the Predictability of the North Atlantic Oscillation |
title_full |
Jet Latitude Regimes and the Predictability of the North Atlantic Oscillation |
title_fullStr |
Jet Latitude Regimes and the Predictability of the North Atlantic Oscillation |
title_full_unstemmed |
Jet Latitude Regimes and the Predictability of the North Atlantic Oscillation |
title_sort |
jet latitude regimes and the predictability of the north atlantic oscillation |
publisher |
arXiv |
publishDate |
2019 |
url |
https://dx.doi.org/10.48550/arxiv.1910.00864 https://arxiv.org/abs/1910.00864 |
genre |
North Atlantic North Atlantic oscillation |
genre_facet |
North Atlantic North Atlantic oscillation |
op_relation |
https://dx.doi.org/10.1002/qj.3796 |
op_rights |
arXiv.org perpetual, non-exclusive license http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
op_doi |
https://doi.org/10.48550/arxiv.1910.00864 https://doi.org/10.1002/qj.3796 |
_version_ |
1766126015025774592 |