scholarly journals Combined winter climate regimes over the North Atlantic/European sector 1766–2000

2005 ◽  
Vol 32 (13) ◽  
Author(s):  
C. Casty
Keyword(s):  
North Atlantic ◽  
Winter Climate ◽  
The North ◽  
The North Atlantic ◽  
European Sector

scholarly journals The link between eddy-driven jet variability and weather regimes in the North Atlantic-European sector

2017 ◽  
Vol 143 (708) ◽  
pp. 2960-2972 ◽  
Author(s):  
Erica Madonna ◽  
Camille Li ◽  
Christian M. Grams ◽  
Tim Woollings
Keyword(s):  
North Atlantic ◽  
Weather Regimes ◽  
The North ◽  
The North Atlantic ◽  
Jet Variability ◽  
European Sector

Evaluation of the North Atlantic SST forcing on the European and Northern African winter climate

2006 ◽  
Vol 26 (2) ◽  
pp. 179-191 ◽  
Author(s):  
Belén Rodríguez-Fonseca ◽  
Irene Polo ◽  
Encarna Serrano ◽  
Manuel Castro
Keyword(s):  
North Atlantic ◽  
Winter Climate ◽  
The North ◽  
Sst Forcing ◽  
The North Atlantic

scholarly journals The remote influence of the extra-tropical stratosphere and tropical troposphere on North Atlantic-European winter circulation

2021 ◽  
Author(s):  
Anna Maidens ◽  
Jeff R Knight ◽  
Adam A Scaife
Keyword(s):  
Surface Pressure ◽  
North Atlantic ◽  
Tropical Atlantic ◽  
Prediction System ◽  
The North ◽  
Winter Conditions ◽  
Winter Circulation ◽  
Tropical Troposphere ◽  
The North Atlantic ◽  
European Sector

<p>Many seasonal forecast systems show skill at monthly to seasonal timescales in predicting the winter North Atlantic Oscillation (NAO), the primary mode of variability in surface pressure over the North Atlantic and European sector.  This skill has practical benefit for prediction of winter conditions over Northern Europe, and arises from the representation of remote teleconnections within the prediction system, such as from the stratosphere or the tropical troposphere.  Despite skill in the NAO, most prediction systems have little skill in other patterns of North Atlantic winter circulation variability, such as East Atlantic Pattern (EAP – the second mode of regional winter surface pressure variability). This is despite the clear contribution that patterns such as the EAP make to European winter climate variability and their demonstrated role in the generation of extreme winter conditions.</p><p> </p><p>We examine the role of the tropical troposphere and extra-tropical stratosphere in driving North Atlantic and European winter circulation patterns, with a focus on teleconnections to the EAP.  We use relaxation experiments, in which a set of seasonal-length hindcasts are run with the atmospheric conditions within the relaxation region constrained to be similar to reanalysis.  These are then compared with an initialised, but otherwise freely evolving, hindcast set, and with reanalysis, in regions outside the relaxation region. The aim is to assess how better prediction of the relaxation regions would influence the skill in prediction of winter atmospheric circulation in the North Atlantic-European sector.</p><p> </p><p>We find that both regions play a role in influencing regional circulation. Tropical tropospheric relaxation in particular increases the reproduction of winter surface pressure anomalies. A key part of this improvement is in the EAP, which is very well reproduced. It is shown that forcing of the EAP occurs via propagating Rossby waves linked to convective anomalies in the tropical Atlantic. In addition, we find that teleconnections from either the tropics or stratosphere lead to reproduction of observed large-scale surface pressure patterns in most winters.  In contrast, the diagnosed response to tropical forcing is rarely matched in the hindcast without relaxation, despite a similar rate of matches with the response to stratospheric forcing. This suggests that while winter stratospheric influences are well represented in the prediction system, tropical influences are under-represented.  The results suggest that the improvement of tropical Atlantic predictability could lead to improvements for European winter predictability, and should be an important focus for future work.</p>

scholarly journals Nonlinearity in the Tropospheric Pathway of ENSO to the North Atlantic

2020 ◽  
Author(s):  
Bernat Jiménez-Esteve ◽  
Daniela I. V. Domeisen
Keyword(s):  
North Atlantic ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Atmospheric Model ◽  
La Niña ◽  
Winter Climate ◽  
The North ◽  
La Nina ◽  
The North Atlantic

Abstract. El Niño Southern Oscillation (ENSO) can exert a remote impact on North Atlantic and European (NAE) winter climate. This teleconnection is driven by the superposition and interaction of different influences, which are generally grouped into two main pathways, namely the tropospheric and stratospheric pathways. In this study, we focus on the tropospheric pathway through the North Pacific and across the North American continent. Due to the possible non-stationary behavior and the limited time period covered by reanalysis data sets, the potential nonlinearity of this pathway remains unclear. In order to address this question, we use a simplified physics atmospheric model forced with seasonally varying prescribed sea surface temperatures (SST) following the evolution of different ENSO phases with linearly varying strength at a fixed location. To isolate the tropospheric pathway the zonal mean stratospheric winds are nudged towards the model climatology. The model experiments indicate that the tropospheric pathway of ENSO to the North Atlantic exhibits significant nonlinearity with respect to the tropical SST forcing, both in the location and amplitude of the impacts. For example, strong El Niño leads to a significantly stronger impact over the North Atlantic Oscillation (NAO) than a La Niña forcing of the same amplitude. For La Niña forcings, there is a saturation in the response, with no further increase in the NAO impact even when doubling the SSTforcing, while this is not the case for El Niño. These findings may have important consequences for long-range predictions of the North Atlantic and Europe.

Characteristics of North European winter lightning related to a high positive North Atlantic Oscillation index

2020 ◽  
Author(s):  
Ivana Kolmašová ◽  
Kateřina Rosická ◽  
Ondřej Santolík
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Large Scale ◽  
Winter Season ◽  
Winter Climate ◽  
The North ◽  
Nao Index ◽  
The North Atlantic ◽  
Icelandic Low ◽  
Azores High

<p>The variability of winter climate in the North Atlantic region is predominantly driven by a large scale alternation of atmospheric masses between the Icelandic Low and Azores High pressure systems called the North Atlantic Oscillation (NAO) and characterized by the NAO index. The calculation of the NAO index is based on the difference between sea-level pressure strengths of the Azores High and the Icelandic Low. Unusually high positive values of the NAO index were observed to manifest themselves by above-average precipitation and severe winter storms over British Isles and other parts of northwestern and northern Europe.</p><p>In the last two decades, the winter season 2014/2015 exhibited the highest positive monthly NAO indexes. During this winter, newspapers in the UK, Germany, Poland, and Scandinavia reported extremely strong storms which caused huge power outages, damages of buildings, and collapses of traffic which paralyzed the daily life. As winter thunderstorms are also characterized by a higher production of very energetic lightning, we use the World Wide Lightning Location Network (WWLLN) data and investigate properties of lightning which occurred in the north European region from October 2014 to March 2015.  The dataset consists of more than 90 thousand lightning detections. We focus on spatial and temporal distribution of lightning strokes, their energies and multiplicity.</p><p>We have found that the diurnal distribution of lightning was random from November till February, while the afternoon peak typical for summer storms was noticeable only in October and March. The median energy of lightning strokes observed in October, November and March reached only about 10-20% of the median energy of strokes detected in December, January and February. The most energetic strokes were concentrated above the ocean close to the western coastal areas and appeared exclusively at night and in the morning hours.</p>

scholarly journals Predictable winter climate in the North Atlantic sector during the 1997-1999 ENSO cycle

2000 ◽  
Vol 27 (7) ◽  
pp. 985-988 ◽  
Author(s):  
B. -W. Dong ◽  
R. T. Sutton ◽  
S. P. Jewson ◽  
A. O'Neill ◽  
J. M. Slingo
Keyword(s):  
North Atlantic ◽  
Enso Cycle ◽  
Winter Climate ◽  
Atlantic Sector ◽  
The North ◽  
The North Atlantic
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