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  1. ENSO Modulation of MJO Teleconnections to the North Atlantic and Europe Authors: R. W. Lee, S. J. Woolnough, A. J. Charlton‐Perez and F. Vitart Published online: 25th November 2019 Abstract: The teleconnection from the Madden‐Julian Oscillation (MJO) provides a source of subseasonal variability and predictability to the North Atlantic‐European (NAE) region. The El Niño‐Southern Oscillation (ENSO) modulates the seasonal mean state, through which the MJO and its teleconnection pattern propagates; however, its impact on this teleconnection to the NAE re
  2. Propagating Annular Modes: Empirical Orthogonal Functions, Principal Oscillation Patterns, and Time Scales Authors: Aditi Sheshadri and R. Alan Plumb Published online: 10th April, 2017 Abstract: The two leading empirical orthogonal functions (EOFs) of zonal-mean zonal wind describe north–south fluctuations, and intensification and narrowing, respectively, of the midlatitude jet. Under certain circumstances, these two leading EOFs cannot be regarded as independent but are in fact manifestations of a single, coupled, underlying mode of the dynamical sys
  3. Evidence for the chaotic origin of Northern Annular Mode variability Authors: S. M. Osprey and M. H. P. Ambaum Published online: 3rd August, 2011 Abstract: Exponential spectra are found to characterize variability of the Northern Annular Mode (NAM) for periods less than 36 days. This corresponds to the observed rounding of the autocorrelation function at lags of a few days. The characteristic persistence timescales during winter and summer is found to be ∼5 days for these high frequencies. Beyond periods of 36 days the characteristic decorrelation ti
  4. The NAO Troposphere–Stratosphere Connection Authors: Maarten H. P. Ambaum and Brian J. Hoskins Published online: 15th July, 2002 Abstract: Using monthly mean data, daily data, and theoretical arguments, relationships between surface pressure variations associated with the North Atlantic Oscillation (NAO), tropopause height, and the strength of the stratospheric vortex are established. An increase in the NAO index leads to a stronger stratospheric vortex, about 4 days later, as a result of increased equatorward refraction of upward-propagating Rossby
  5. The Subseasonal Experiment (SubX): A Multimodel Subseasonal Prediction Experiment Authors: Kathy Pegion et al Published online: 24th October, 2019 Abstract: The Subseasonal Experiment (SubX) is a multimodel subseasonal prediction experiment designed around operational requirements with the goal of improving subseasonal forecasts. Seven global models have produced 17 years of retrospective (re)forecasts and more than a year of weekly real-time forecasts. The reforecasts and forecasts are archived at the Data Library of the International Researc
  6. On the Linearity of the Stratospheric and Euro-Atlantic Sector Response to ENSO Authors: Paloma Trascasa-Castro, Yu Yeung Scott YiuD and Jennifer K. Fletcher Published: 6th September, 2019 Abstract: The dependence of the winter stratospheric and Euro-Atlantic climate response on ENSO amplitude is investigated using the HadGEM3 model. Experiments are performed with imposed east Pacific sea surface temperature perturbations corresponding to Niño-3.4 anomalies of ±0.75, 1.5, 2.25, and 3.0 K. In the North Pacific, El Niño (EN) deepens and shifts the Aleu
  7. Why is the North Atlantic Oscillation More Predictable in December? Authors: Baoqiang Tian and Ke Fan Published: 20th August, 2019 Abstract: The prediction skill of the Climate Forecast System, version 2 (CFSv2), for the North Atlantic Oscillation (NAO) is evaluated in three winter months (December, January, and February). The results show that the CFSv2 model can skillfully predict the December NAO one month in advance. There are two main contributors to NAO predictability in December. One is the predictability of the relationship between the North
  8. Impact of Arctic sea ice variations on winter temperature anomalies in northern hemispheric land areas Authors: T. Koenigk, Y. Gao, G. Gastineau, N. Keenlyside, T. Nakamura, F. Ogawa, Y. Orsolini, V. Semenov, L. Suo, T. Tian, T. Wang, J. J. Wettstein and S. Yang Published: 30th July, 2018 Abstract: Coordinated numerical ensemble experiments with six different state-of-the-art atmosphere models have been used in order to evaluate the respective impact of the observed Arctic sea ice and sea surface temperature (SST) variations on air te
  9. The importance of stratospheric initial conditions for winter North Atlantic Oscillation predictability and implications for the signal‐to‐noise paradox Authors: Christopher H. O'Reilly, Antje Weisheimer, Tim Woollings, Lesley J. Gray and Dave MacLeod Published: 12th October, 2018 Abstract: This study investigates the influence of atmospheric initial conditions on winter seasonal forecasts of the North Atlantic Oscillation (NAO). Hindcast (or reforecast) experiments – which differ only in their initial conditions – are performe
  10. A mechanism for lagged North Atlantic climate response to solar variability Authors: Adam A. Scaife, Sarah Ineson, Jeff R. Knight, Lesley Gray, Kunihiko Kodera and Doug M. Smith First Published: 3rd January, 2013 Abstract: Variability in solar irradiance has been connected to changes in surface climate in the North Atlantic through both observational and climate modelling studies which suggest a response in the atmospheric circulation that resembles the North Atlantic Oscillation or its hemispheric equivalent the Arctic Oscillation. It has also
  11. Solar forcing of winter climate variability in the Northern Hemisphere Authors: Sarah Ineson, Adam A. Scaife, Jeff R. Knight, James C. Manners, Nick J. Dunstone, Lesley J. Gray and Joanna D. Haigh First Published: 9th October, 2011 Abstract: An influence of solar irradiance variations on Earth’s surface climate has been repeatedly suggested, based on correlations between solar variability and meteorological variables. Specifically, weaker westerly winds have been observed in winters with a less active sun, for example at the minimum phase
  12. Review of Tropical‐Extratropical Teleconnections on Intraseasonal Time Scales Authors: Cristiana Stan, David M. Straus, Jorgen S. Frederiksen, Hai Lin, Eric D. Maloney and Courtney Schumacher First Published: 12th September, 2017 Abstract: The interactions and teleconnections between the tropical and midlatitude regions on intraseasonal time scales are an important modulator of tropical and extratropical circulation anomalies and their associated weather patterns. These interactions arise due to the impact of the tropics on the extratropics, the
  13. Observed and Simulated Teleconnections Between the Stratospheric Quasi‐Biennial Oscillation and Northern Hemisphere Winter Atmospheric Circulation Authors: Martin B. Andrews , Jeff R. Knight, Adam A. Scaife, Yixiong Lu, Tongwen Wu, Lesley J. Gray and Verena Schenzinger Published: 15th January, 2019 Abstract: The Quasi‐Biennial Oscillation (QBO) is the dominant mode of interannual variability in the tropical stratosphere, with easterly and westerly zonal wind regimes alternating over a period of about 28 months. It appears to influence the Northern
  14. Circulation Response to Fast and Slow MJO Episodes Authors: Priyanka Yadav and David M. Straus Published: 6th April, 2017 Abstract: Fast and slow Madden–Julian oscillation (MJO) episodes have been identified from 850- and 200-hPa zonal wind and outgoing longwave radiation (OLR) for 32 winters (16 October–17 March) 1980/81–2011/12. For 26 fast cases the OLR took no more than 10 days to propagate from phase 3 (convection over the Indian Ocean) to phase 6 (convection over the western Pacific). For 8 slow cases the propagation took at least 20
  15. A robust empirical seasonal prediction of winter NAO and surface climate Authors: L. Wang, M. Ting and P. J. Kushner Published: 21st March, 2017 Abstract: A key determinant of winter weather and climate in Europe and North America is the North Atlantic Oscillation (NAO), the dominant mode of atmospheric variability in the Atlantic domain. Skilful seasonal forecasting of the surface climate in both Europe and North America is reflected largely in how accurately models can predict the NAO. Most dynamical models, however, have limited skill in seasona
  16. Near-term Climate Predictions of the North Atlantic Region - YouTube Presentation Presenters/Authors: Dr. Nick Dunstone, Doug Smith, Adam Scaife, Leon Hermanson, Rosie Eade, Niall Robinson, Martin Andrews and Jeff Knight Presentation Team from: The UK Met Office, Hadley Centre Presentation Date: 6th April, 2017 (at St Andrews, Scotland) Abstract: None (but see below) Link to full YouTube presentation (57 minutes): https://www.youtube.com/watch?reload=9&v=jfKr6oRnn2k This brilliant "balanced" present
  17. How Predictable Are the Arctic and North Atlantic Oscillations? Exploring the Variability and Predictability of the Northern Hemisphere Authors: Daniela I. V. Domeisena, Gualtiero Badin and Inga M. Koszalka Published: 18th January, 2018 Abstract: The North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) describe the dominant part of the variability in the Northern Hemisphere extratropical troposphere. Because of the strong connection of these patterns with surface climate, recent years have shown an increased interest and an increasing s
  18. Skillful long‐range prediction of European and North American winters Authors: A. A. Scaife et al (22 authors), UK Met Office Published: 9th April, 2014 Abstract: Until recently, long‐range forecast systems showed only modest levels of skill in predicting surface winter climate around the Atlantic Basin and associated fluctuations in the North Atlantic Oscillation at seasonal lead times. Here we use a new forecast system to assess seasonal predictability of winter North Atlantic climate. We demonstrate that key aspects of European and North American
  19. The North Atlantic Oscillation - Learning Guide Authors: UK Met Office Last Updated: 15th June, 2018 Abstract: The North Atlantic Oscillation (NAO) is a term that refers to large scale changes in pressure that occur naturally in the North Atlantic region. These changes have a massive impact on both weather and climate patterns in the surrounding continents. Prior knowledge of forthcoming changes in the NAO can thus provide information about such impacts on seasonal timescales and beyond. Review: This article is one of a serie
  20. The dynamics of NAO teleconnection pattern growth and decay Authors: Steven B. Feldstein Published: 29th December, 2006 Abstract: This investigation performs both diagnostic analyses with NCEP/NCAR re‐analysis data and forced, barotropic model calculations to examine the dynamical mechanisms associated with the growth and decay of the North Atlantic Oscillation (NAO) teleconnection pattern. The diagnostic calculations include projection and composite analyses of each term in the stream‐function‐tendency equation. The results of the analy
  21. A last millennium perspective on North Atlantic variability: exploiting synergies between models and proxy data Authors: Ortega, P; Robson, J; Moffa-Sanchez, P; Thornalley, D and Swingedouw, D. Published: June, 2017 Abstract: The North Atlantic is a key region for decadal prediction as it has experienced significant multi-decadal variability over the observed period. This variability, which is thought to be intrinsic to the region, can potentially modulate, either by amplifying or mitigating, the global warming signal from anthropogenic greenhous
  22. Recent Progress in Understanding and Predicting Atlantic Decadal Climate Variability Authors: S. G. Yeager and J. I. Robson Published: 18th April, 2017 Abstract: Purpose of Review Recent Atlantic climate prediction studies are an exciting new contribution to an extensive body of research on Atlantic decadal variability and predictability that has long emphasized the unique role of the Atlantic Ocean in modulating the surface climate. We present a survey of the foundations and frontiers in our understanding of Atlantic variability mechanisms, th
  23. Gulf Stream Excursions and Sectional Detachments Generate the Decadal Pulses in the Atlantic Multidecadal Oscillation Authors: Sumant Nigama, Alfredo Ruiz-Barradas and Léon Chafik Published: 9th January, 2018 Abstract: Decadal pulses within the lower-frequency Atlantic multidecadal oscillation (AMO) are a prominent but underappreciated AMO feature, representing decadal variability of the subpolar gyre (e.g., the Great Salinity Anomaly of the 1970s) and wielding notable influence on the hydroclimate of the African and American continents. Her
  24. The Central Role of Ocean Dynamics in Connecting the North Atlantic Oscillation to the Extratropical Component of the Atlantic Multidecadal Oscillation Authors: Thomas L. Delworth, Fanrong Zeng, Liping Zhang, Rong Zhang, Gabriel A. Vecchia and Xiaosong Yang Published: 15th May, 2017 Abstract: The relationship between the North Atlantic Oscillation (NAO) and Atlantic sea surface temperature (SST) variability is investigated using models and observations. Coupled climate models are used in which the ocean component is either a fully dynamic ocean o
  25. Intrinsic and atmospherically forced variability of the AMOC : insights from a large-ensemble ocean hindcast Authors: Leroux S., Penduff T., Bessieres L., Molines J. M., Brankart J. M., Sérazin Guillaume, Barnier B. and Terray L. Published: 1st February, 2018 Abstract: This study investigates the origin and features of interannual-decadal Atlantic meridional overturning circulation (AMOC) variability from several ocean simulations, including a large (50 member) ensemble of global, eddy-permitting (1/4 degrees) ocean-sea ice hindcasts. After an
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