scholarly journals The influence of solar activity on action centres of atmospheric circulation in North Atlantic

2015 ◽  
Vol 33 (2) ◽  
pp. 207-215 ◽  
Author(s):  
L. Sfîcă ◽  
M. Voiculescu ◽  
R. Huth
Keyword(s):  
Solar Activity ◽  
Sea Level ◽  
North Atlantic ◽  
High Solar Activity ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The North ◽  
The Pacific ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract. We analyse the response of sea level pressure and mid-tropospheric (500 hPa) geopotential heights to variations in solar activity. We concentrate on the Northern Hemisphere and North Atlantic in the period 1948–2012. Composite and correlation analyses point to a strengthening of the North Atlantic Oscillation and weakening (i.e. becoming more zonal) of the Pacific/North American pattern. The locations of points with lowest and highest sea level pressure in the North Atlantic change their positions between low and high solar activity.

scholarly journals Effect of Synoptic Systems on the Variability of the North Atlantic Oscillation

2005 ◽  
Vol 133 (10) ◽  
pp. 2894-2904 ◽  
Author(s):  
Ulrike Löptien ◽  
Eberhard Ruprecht
Keyword(s):  
North Atlantic Oscillation ◽  
Sea Level ◽  
North Atlantic ◽  
Low Frequency ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The North ◽  
Low Frequency Variability ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract The North Atlantic Oscillation (NAO) represents the dominant mode of atmospheric variability in the North Atlantic region. In the present study, the role of the synoptic systems (cyclones and anticyclones) in generating the NAO pattern is investigated. To study the intermonthly variations of the NAO, NCEP–NCAR reanalysis data are used, and for the interdecadal variations the results of a 300-yr control integration under present-day conditions of the coupled model ECHAM4/OPYC3 are analyzed. A filtering method is developed for the sea level pressure anomalies. Application of this method to each grid point yields the low-frequency variability in the sea level pressure field that is due to the synoptic systems. The low-frequency variability of the filtered and the original data are in high agreement. This indicates that the low-frequency pressure variability, and with it the variability of the NAO, is essentially caused by the distribution of the synoptic systems. The idea that the distribution of the synoptic systems is the cause of the variation of the NAO is confirmed by high correlation between the latitudinal position of the polar front over the North Atlantic and the NAO index. Since most of the low-frequency variability in sea level pressure can be explained through the distribution of the synoptic systems, the NAO seems to be a reflection of the distribution of the synoptic systems, rather than the source for variations in the cyclone tracks.

scholarly journals Multidecadal Mobility of the North Atlantic Oscillation

2013 ◽  
Vol 26 (8) ◽  
pp. 2453-2466 ◽  
Author(s):  
G. W. K. Moore ◽  
I. A. Renfrew ◽  
R. S. Pickart
Keyword(s):  
North Atlantic Oscillation ◽  
Sea Level ◽  
North Atlantic ◽  
Pressure Field ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Modes Of Variability ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract The North Atlantic Oscillation (NAO) is one of the most important modes of variability in the global climate system and is characterized by a meridional dipole in the sea level pressure field, with centers of action near Iceland and the Azores. It has a profound influence on the weather, climate, ecosystems, and economies of Europe, Greenland, eastern North America, and North Africa. It has been proposed that around 1980, there was an eastward secular shift in the NAO’s northern center of action that impacted sea ice export through Fram Strait. Independently, it has also been suggested that the location of its southern center of action is tied to the phase of the NAO. Both of these attributes of the NAO have been linked to anthropogenic climate change. Here the authors use both the one-point correlation map technique as well as empirical orthogonal function (EOF) analysis to show that the meridional dipole that is often seen in the sea level pressure field over the North Atlantic is not purely the result of the NAO (as traditionally defined) but rather arises through an interplay among the NAO and two other leading modes of variability in the North Atlantic region: the East Atlantic (EA) and the Scandinavian (SCA) patterns. This interplay has resulted in multidecadal mobility in the two centers of action of the meridional dipole since the late nineteenth century. In particular, an eastward movement of the dipole has occurred during the 1930s to 1950s as well as more recently. This mobility is not seen in the leading EOF of the sea level pressure field in the region.

scholarly journals Decadal Shift of NAO-Linked Interannual Sea Level Variability along the U.S. Northeast Coast

2018 ◽  
Vol 31 (13) ◽  
pp. 4981-4989 ◽  
Author(s):  
Jessica S. Kenigson ◽  
Weiqing Han ◽  
Balaji Rajagopalan ◽  
Yanto ◽  
Mike Jasinski
Keyword(s):  
Sea Level ◽  
North Atlantic ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The North ◽  
Decadal Shift ◽  
Nao Index ◽  
The North Atlantic ◽  
The U.S ◽  
Northeast Coast

Recent studies have linked interannual sea level variability and extreme events along the U.S. northeast coast (NEC) to the North Atlantic Oscillation (NAO), a natural internal climate mode that prevails in the North Atlantic Ocean. The correlation between the NAO index and coastal sea level north of Cape Hatteras was weak from the 1960s to the mid-1980s, but it has markedly increased since around 1987. The causes for the decadal shift remain unknown. Yet understanding the abrupt change is vital for decadal sea level prediction and is essential for risk management. Here we use a robust method, the Bayesian dynamic linear model (DLM), to explore the nonstationary NAO impact on NEC sea level. The results show that a spatial pattern change of NAO-related winds near the NEC is a major cause of the NAO–sea level relationship shift. A new index using regional sea level pressure is developed that is a significantly better predictor of NEC sea level than is the NAO and is strongly linked to the intensity of westerly winds near the NEC. These results point to the vital importance of monitoring regional changes of wind and sea level pressure patterns, rather than the NAO index alone, to achieve more accurate predictions of sea level change along the NEC.

scholarly journals Impact of the Stratosphere on the Winter Tropospheric Teleconnections between ENSO and the North Atlantic and European Region

2009 ◽  
Vol 22 (5) ◽  
pp. 1223-1238 ◽  
Author(s):  
Chiara Cagnazzo ◽  
Elisa Manzini
Keyword(s):  
Sea Level ◽  
Central Europe ◽  
North Atlantic ◽  
The Arctic ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The North ◽  
The North Atlantic

Abstract The possible role of stratospheric variability on the tropospheric teleconnection between El Niño–Southern Oscillation (ENSO) and the North Atlantic and European (NAE) region is addressed by comparing results from two ensembles of simulations performed with an atmosphere general circulation model fully resolving the stratosphere (with the top at 0.01 hPa) and its low-top version (with the top at 10 hPa). Both ensembles of simulations consist of nine members, covering the 1980–99 period and are forced with prescribed observed sea surface temperatures. It is found that both models capture the sensitivity of the averaged polar winter lower stratosphere to ENSO in the Northern Hemisphere, although with a reduced amplitude for the low-top model. In late winter and spring, the ENSO response at the surface is instead different in the two models. A large-scale coherent pattern in sea level pressure, with high pressures over the Arctic and low pressures over western and central Europe and the North Pacific, is found in the February–March mean of the high-top model. In the low-top model, the Arctic high pressure and the western and central Europe low pressure are very much reduced. The high-top minus low-top model difference in the ENSO temperature and precipitation anomalies is that North Europe is colder and the Northern Atlantic storm track is shifted southward in the high-top model. In addition, it has been found that major sudden stratospheric warming events are virtually lacking in the low-top model, while their frequency of occurrence is broadly realistic in the high-top model. Given that this is a major difference in the dynamical behavior of the stratosphere of the two models and that these events are favored by ENSO, it is concluded that the occurrence of sudden stratospheric warming events affects the reported differences in the tropospheric ENSO–NAE teleconnection. Given that the essence of the high-top minus low-top model difference is a more annular (or zonal) pattern of the anomaly in sea level pressure, relatively larger over the Arctic and the NAE regions, this interpretation is consistent with the observational evidence that sudden stratospheric warmings play a role in giving rise to persistent Arctic Oscillation anomalies at the surface.

scholarly journals Changes in atmospheric variability in a glacial climate and the impacts on proxy data: a model intercomparison

2009 ◽  
Vol 5 (3) ◽  
pp. 489-502 ◽  
Author(s):  
F. S. R. Pausata ◽  
C. Li ◽  
J. J. Wettstein ◽  
K. H. Nisancioglu ◽  
D. S. Battisti
Keyword(s):  
Sea Level ◽  
North Atlantic ◽  
Climate Models ◽  
Atmospheric Variability ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The North ◽  
Surface Climate ◽  
Leading Mode ◽  
The North Atlantic Oscillation

Abstract. Using four different climate models, we investigate sea level pressure variability in the extratropical North Atlantic in the preindustrial climate (1750 AD) and at the Last Glacial Maximum (LGM, 21 kyrs before present) in order to understand how changes in atmospheric circulation can affect signals recorded in climate proxies. In general, the models exhibit a significant reduction in interannual variance of sea level pressure at the LGM compared to pre-industrial simulations and this reduction is concentrated in winter. For the preindustrial climate, all models feature a similar leading mode of sea level pressure variability that resembles the leading mode of variability in the instrumental record: the North Atlantic Oscillation (NAO). In contrast, the leading mode of sea level pressure variability at the LGM is model dependent, but in each model different from that in the preindustrial climate. In each model, the leading (NAO-like) mode of variability explains a smaller fraction of the variance and also less absolute variance at the LGM than in the preindustrial climate. The models show that the relationship between atmospheric variability and surface climate (temperature and precipitation) variability change in different climates. Results are model-specific, but indicate that proxy signals at the LGM may be misinterpreted if changes in the spatial pattern and seasonality of surface climate variability are not taken into account.

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