scholarly journals North Atlantic Storm Track Variability and Its Association to the North Atlantic Oscillation and Climate Variability of Northern Europe

1997 ◽  
Vol 10 (7) ◽  
pp. 1635-1647 ◽  
Author(s):  
Jeffrey C. Rogers
Keyword(s):  
Climate Variability ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Storm Track ◽  
Northern Europe ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

scholarly journals The North Atlantic Oscillation and the North Atlantic Jet Variability: Precursors to NAO Regimes and Transitions

2012 ◽  
Vol 69 (12) ◽  
pp. 3763-3787 ◽  
Author(s):  
Dehai Luo ◽  
Jing Cha
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Zonal Wind ◽  
Storm Track ◽  
Dominant Negative ◽  
Wind Condition ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
North Atlantic Jet

Abstract In this paper, precursors to the North Atlantic Oscillation (NAO) and its transitions are investigated to understand the dynamical cause of the interdecadal NAO variability from dominant negative (NAO−) events during 1950–77 (P1) to dominant positive (NAO+) events during 1978–2010 (P2). It is found that the phase of the NAO event depends strongly on the latitudinal position of the North Atlantic jet (NAJ) prior to the NAO onset. The NAO− (NAO+) events occur frequently when the NAJ core prior to the NAO onset is displaced southward (northward), as the situation within P1 (P2). Thus, the northward (southward) shift of the NAJ from its mean position is a precursor to the NAO+ (NAO−) event. This finding is further supported by results obtained from a weakly nonlinear model. Furthermore, the model results show that, when the Atlantic mean zonal wind exceeds a critical strength under which the dipole anomaly prior to the NAO onset is stationary, in situ NAO− (NAO+) events, which are events not preceded by opposite events, can occur frequently during P1 (P2) when the Atlantic storm track is not too strong. This mean zonal wind condition is easily satisfied during P1 and P2. However, when the Atlantic storm track (mean zonal wind) prior to the NAO onset is markedly intensified (weakened), the NAO event can undergo a transition from one phase to another, especially in a relatively strong background westerly wind, the Atlantic storm track has to be strong enough to produce a phase transition.

scholarly journals Impacts of the North Atlantic Oscillation on Winter Precipitations and Storm Track Variability in Southeast Canada and Northeast US

2020 ◽  
Author(s):  
Julien Chartrand ◽  
Francesco Salvatore Rocco Pausata
Keyword(s):  
United States ◽  
North America ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Storm Track ◽  
The United States ◽  
Eastern North America ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract. The North Atlantic Oscillation (NAO) affects atmospheric variability from eastern North America to Europe. Although the link between the NAO and winter precipitations in the eastern North America have been the focus of previous work, only few studies have hitherto provided clear physical explanations on these relationships. In this study we revisit and extend the analysis of the effect of the NAO on winter precipitations over a large domain covering southeast Canada and the northeastern United States. Furthermore, here we use the recent ERA5 reanalysis dataset (1979–2018), which currently has the highest available horizontal resolution for a global reanalysis (0.25°), to track extratropical cyclones to delve into the physical processes behind the relationship between NAO and precipitation, snowfall, snowfall-to-precipitation ratio (S/P), and snow cover depth anomalies in the region. In particular, our results show that positive NAO phases are associated with less snowfall over a wide region covering Nova Scotia, New England and the Mid-Atlantic of the United States relative to negative NAO phases. Henceforth, a significant negative correlation is also seen between S/P and the NAO over this region. This is due to a decrease (increase) in cyclogenesis of coastal storms near the United States east coast during positive (negative) NAO phases, as well as a northward (southward) displacement of the mean storm track over North America.

Decadal Relationship between European Blocking and the North Atlantic Oscillation during 1978–2011. Part I: Atlantic Conditions

2015 ◽  
Vol 72 (3) ◽  
pp. 1152-1173 ◽  
Author(s):  
Dehai Luo ◽  
Yao Yao ◽  
Aiguo Dai
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Western Europe ◽  
Storm Track ◽  
Western Atlantic ◽  
Atlantic Sector ◽  
The North ◽  
Nao Index ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Both the positive and negative phases of the North Atlantic Oscillation (NAO+ and NAO−, respectively) and atmospheric blocking in the Euro-Atlantic sector reflect synoptic variability over the region and thus are intrinsically linked. This study examines their relationship from a decadal change perspective. Since the winter-mean NAO index is defined as a time average of instantaneous NAO indices over the whole winter, it is unclear how the activity of European blocking (EB) events can be related to the variation of the positive mean NAO index. Here, this question is examined by dividing the winter period 1978–2011 into two decadal epochs: 1978–94 (P1) with an increasing and high NAO index and 1995–2011 (P2) with a decreasing and low NAO index. Using atmospheric reanalysis data, it is shown that there are more intense and persistent EB events in eastern Europe during P1 than during P2, while the opposite is true for western Europe. It is further shown that there are more NAO+ (NAO−) events during P1 (P2). The EB events associated with NAO+ events extend more eastward and are associated with stronger Atlantic mean zonal wind and weaker western Atlantic storm track during P1 than during P2, but EB events associated with NAO− events increase in western Europe under opposite Atlantic conditions during P2. Thus, the increase in the number of individual NAO+ (NAO−) events results in more EB events in eastern (western) Europe during P1 (P2). The EB change is also associated with the increased frequency of NAO− to NAO+ (NAO+ to NAO−) transition events.

scholarly journals Bivariate Modelling of a Teleconnection Index and Extreme Rainfall in a Small North Atlantic Island

Climate ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 86
Author(s):  
Luis Angel Espinosa ◽  
Maria Manuela Portela ◽  
João Dehon Pontes Filho ◽  
Martina Zelenakova
Keyword(s):  
Climate Variability ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Extreme Rainfall ◽  
Small Island ◽  
Return Periods ◽  
Rainfall Events ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

This paper explores practical applications of bivariate modelling via copulas of two likely dependent random variables, i.e., of the North Atlantic Oscillation (NAO) coupled with extreme rainfall on the small island of Madeira, Portugal. Madeira, due to its small size (∼740 km2), very pronounced mountain landscape, and location in the North Atlantic, experiences a wide range of rainfall regimes, or microclimates, which hamper the analyses of extreme rainfall. Previous studies showed that the influence of the North Atlantic Oscillation (NAO) on extreme rainfall is at its largest in the North Atlantic sector, with the likelihood of increased rainfall events from December through February, particularly during negative NAO phases. Thus, a copula-based approach was adopted for teleconnection, aiming at assigning return periods of daily values of an NAO index (NAOI) coupled with extreme daily rainfalls—for the period from December 1967 to February 2017—at six representative rain gauges of the island. The results show that (i) bivariate copulas describing the dependence characteristics of the underlying joint distributions may provide useful analytical expressions of the return periods of the coupled previous NAOI and extreme rainfall and (ii) that recent years show signs of increasing climate variability with more anomalous daily negative NAOI along with higher extreme rainfall events. These findings highlight the importance of multivariate modelling for teleconnections of prominent patterns of climate variability, such as the NAO, to extreme rainfall in North Atlantic regions, especially in small islands that are highly vulnerable to the effects of abrupt climate variability.

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