scholarly journals Decadal Variation of Atmospheric Rivers in Relation to North Atlantic Tripole SST Mode

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1252
Author(s):  
Jie Zhang ◽  
Yinglai Jia ◽  
Rui Ji ◽  
Yifei Wu
Keyword(s):  
North Atlantic ◽  
Time Scale ◽  
Lower Layer ◽  
Reanalysis Data ◽  
Decadal Time Scale ◽  
Atmospheric Rivers ◽  
The North ◽  
Decadal Variations ◽  
Extreme Rain ◽  
The North Atlantic

The North Atlantic tripole (NAT) is the leading mode of sea-surface temperature (SST) in the decadal time scale. Although the NAT is forced by North Atlantic oscillation (NAO), it also has an effect on the atmosphere; for example, the early winter tripole SST signal can influence storm tracks in March. As the NAT not only changes the baroclinicity of the lower layer but also modifies the moisture being released into the atmosphere, we surmise that the NAT has an impact on moisture transport and atmospheric rivers in the decadal time scale. Using ERA5 reanalysis data, the decadal variations in Atmospheric Rivers (ARs) in the North Atlantic in boral winter in relation to NAT phases were studied. During the positive NAT phase, the positive SST in the central and western North Atlantic increases the humidity and causes an anticyclonic wind response, which enhances the northeastward transport of moisture. As a result, ARs tend to be longer and transport more moisture toward northwestern Europe. This causes enhanced extreme rain in the UK and Norway. During the negative NAT phase, the positive SST anomalies in the south and east of the North Atlantic provide more moisture, induce a southward shift of the ARs and enhance extreme rain in the Iberian Peninsula. The Gulf Stream (GS) front is stronger during the negative NAT phase, increasing the frequency of the atmospheric front and enlarging the rain rate in ARs.

scholarly journals The concurrence of Atmospheric Rivers and explosive cyclogenesis in the North Atlantic and North Pacific basins

2017 ◽  
Author(s):  
Jorge Eiras-Barca ◽  
Alexandre M. Ramos ◽  
Joaquim G. Pinto ◽  
Ricardo M. Trigo ◽  
Margarida L. R. Liberato ◽  
...  
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Reanalysis Data ◽  
Water Vapour Flux ◽  
Atmospheric Rivers ◽  
The North ◽  
Explosive Cyclones ◽  
The North Atlantic ◽  
Characteristic Features ◽  
Western Side

Abstract. The explosive cyclogenesis of extra-tropical cyclones and the occurrence of atmospheric rivers are characteristic features of baroclinic atmospheres, and are both closely related to extreme hydrometeorological events in the mid-latitudes, particularly on coastal areas on the western side of the continents. The potential role of atmospheric rivers in the explosive cyclone deepening has been previously analysed for selected case studies, but a general assessment from the climatological perspective is still missing. Using ERA-Interim reanalysis data for 1979–2011, we analyse the concurrence of atmospheric rivers and explosive cyclogenesis over the North Atlantic and North Pacific Basins for the extended winter months (ONDJFM). Atmospheric rivers are identified for almost 80 % of explosive deepening cyclones. For non-explosive cyclones, atmospheric rivers are found only in roughly 40 % of the cases. The analysis of the time evolution of the high values of water vapour flux associated with the atmospheric river during the cyclone development phase leads us to hypothesize that the identified relationship is the fingerprint of a mechanism that raises the odds of an explosive cyclogenesis occurrence and not merely a statistical relationship. This insight can be helpful for the predictability of high impact weather associated with explosive cyclones and atmospheric rivers.

scholarly journals The concurrence of atmospheric rivers and explosive cyclogenesis in the North Atlantic and North Pacific basins

2018 ◽  
Vol 9 (1) ◽  
pp. 91-102 ◽  
Author(s):  
Jorge Eiras-Barca ◽  
Alexandre M. Ramos ◽  
Joaquim G. Pinto ◽  
Ricardo M. Trigo ◽  
Margarida L. R. Liberato ◽  
...  
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Reanalysis Data ◽  
Water Vapour Flux ◽  
Atmospheric Rivers ◽  
The North ◽  
Explosive Cyclones ◽  
The North Atlantic ◽  
Characteristic Features ◽  
Western Side

Abstract. The explosive cyclogenesis of extratropical cyclones and the occurrence of atmospheric rivers are characteristic features of a baroclinic atmosphere, and are both closely related to extreme hydrometeorological events in the mid-latitudes, particularly on coastal areas on the western side of the continents. The potential role of atmospheric rivers in the explosive cyclone deepening has been previously analysed for selected case studies, but a general assessment from the climatological perspective is still missing. Using ERA-Interim reanalysis data for 1979–2011, we analyse the concurrence of atmospheric rivers and explosive cyclogenesis over the North Atlantic and North Pacific basins for the extended winter months (ONDJFM). Atmospheric rivers are identified for almost 80 % of explosive deepening cyclones. For non-explosive cyclones, atmospheric rivers are found only in roughly 40 % of the cases. The analysis of the time evolution of the high values of water vapour flux associated with the atmospheric river during the cyclone development phase leads us to hypothesize that the identified relationship is the fingerprint of a mechanism that raises the odds of an explosive cyclogenesis occurrence and not merely a statistical relationship. These new insights on the relationship between explosive cyclones and atmospheric rivers may be helpful to a better understanding of the associated high-impact weather events.

scholarly journals Temperature Anomalies in the Northeastern North Atlantic: Subpolar and Subtropical Precursors on Multiannual Time Scales

2007 ◽  
Vol 20 (10) ◽  
pp. 1976-1990
Author(s):  
Martina M. Junge ◽  
Klaus Fraedrich
Keyword(s):  
Time Scales ◽  
North Atlantic ◽  
Time Scale ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
State Variables ◽  
Decadal Time Scale ◽  
The North ◽  
The North Atlantic

Abstract An adjoint ocean general circulation model of the North Atlantic is employed to calculate sensitivities of temperature in the northeastern North Atlantic with respect to atmospheric nonlocal fluxes and ocean state variables at prior times, up to 7 yr. Maximum sensitivities cross the Atlantic from east to west within 3 to 4 yr. On this interannual time scale, advection of temperature perturbations by the climatological flow is suggested as the prime mechanism responsible for SST perturbations in the northeastern North Atlantic. The pathway of sensitivities lies preferentially beneath the surface and can be understood in terms of the reemergence mechanism. This provides the link between local forcing, mainly by heat flux in winter, and resurfacing of perturbations at remote locations. On the multiannual to decadal time scale, the western subpolar gyre plays a key role: negative temperature sensitivities that evolve in parallel with positive salinity sensitivities in the Labrador and Irminger Seas give rise to pressure gradients and velocity perturbations that have effects on SST by modifying the oceanic heat transport into the northeastern North Atlantic. Together with additional influence from the Tropics and the subtropical gyre on time scales of 5 yr and beyond, these sensitivities combine to make a plethora of time scales that play a role in shaping SST perturbations in the North Atlantic.

scholarly journals On the Structure and Teleconnections of North Atlantic Decadal Variability

2011 ◽  
Vol 24 (9) ◽  
pp. 2209-2223 ◽  
Author(s):  
Francisco J. Álvarez-García ◽  
María J. OrtizBevia ◽  
William D. CabosNarvaez
Keyword(s):  
North Atlantic ◽  
Time Scale ◽  
Decadal Variability ◽  
The North ◽  
The Pacific ◽  
Tropical North Atlantic ◽  
Decadal Variations ◽  
The Pacific Ocean ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Decadal variability in the North Atlantic has been associated in the literature with a tripolar pattern of sea surface temperature (SST) anomalies that show one sign in the western midlatitudinal North Atlantic and the opposite in the subpolar and tropical North Atlantic. The present analysis of observed SST from 1870 to 2009 leads to the dissection of the SST tripole into two components, each with a different time scale in the decadal band and different teleconnections in the Atlantic basin; while the subpolar and tropical poles present quasi-decadal variations with a period of about 9 years, essentially uncorrelated with other parts of the basin, the center of action in the western midlatitudes is characterized by a longer time scale of about 14 years and significant correlations with the tropical South Atlantic and the Norwegian and North Sea(s). The 9-yr period variations are associated with an atmospheric configuration resembling the east Atlantic pattern, whereas the 14-yr period fluctuations seem to be related to the North Atlantic Oscillation pattern. Each component also bears a different relationship with the decadal variability in the Pacific Ocean.

Identification and quantification of the North Atlantic Deep Water pathways

2021 ◽  
Author(s):  
Philippe Miron ◽  
Maria J. Olascoaga ◽  
Francisco J. Beron-Vera ◽  
Kimberly L. Drouin ◽  
M. Susan Lozier
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Sea Water ◽  
Lower Layer ◽  
North Atlantic Deep Water ◽  
Meridional Overturning Circulation ◽  
Labrador Sea ◽  
Western Boundary ◽  
The North ◽  
The North Atlantic

<p>The North Atlantic Deep Water (NADW) flows equatorward along the Deep Western Boundary Current (DWBC) as well as interior pathways and is a critical part of the Atlantic Meridional Overturning Circulation. Its upper layer, the Labrador Sea Water (LSW), is formed by open-ocean deep convection in the Labrador and Irminger Seas while its lower layers, the Iceland–Scotland Overflow Water (ISOW) and the Denmark Strait Overflow Water (DSOW), are formed north of the Greenland–Iceland–Scotland Ridge.</p><p>In recent years, more than two hundred acoustically-tracked subsurface floats have been deployed in the deep waters of the North Atlantic.  Studies to date have highlighted water mass pathways from launch locations, but due to limited float trajectory lengths, these studies have been unable to identify pathways connecting  remote regions.</p><p>This work presents a framework to explore deep water pathways from their respective sources in the North Atlantic using Markov Chain (MC) modeling and Transition Path Theory (TPT). Using observational trajectories released as part of OSNAP and the Argo projects, we constructed two MCs that approximate the lower and upper layers of the NADW Lagrangian dynamics. The reactive NADW pathways—directly connecting NADW sources with a target at 53°N—are obtained from these MCs using TPT.</p><p>Preliminary results show that twenty percent more pathways of the upper layer(LSW) reach the ocean interior compared to  the lower layer (ISOW, DSOW), which mostly flows along the DWBC in the subpolar North Atlantic. Also identified are the Labrador Sea recirculation pathways to the Irminger Sea and the direct connections from the Reykjanes Ridge to the eastern flank of the Mid–Atlantic Ridge, both previously observed. Furthermore, we quantified the eastern spread of the LSW to the area surrounding the Charlie–Gibbs Fracture Zone and compared it with previous analysis. Finally, the residence time of the upper and lower layers are assessed and compared to previous observations.</p>

scholarly journals Timing and structure of the Younger Dryas event and its underlying climate dynamics

2020 ◽  
Vol 117 (38) ◽  
pp. 23408-23417
Author(s):  
Hai Cheng ◽  
Haiwei Zhang ◽  
Christoph Spötl ◽  
Jonathan Baker ◽  
Ashish Sinha ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
North Atlantic ◽  
Time Scale ◽  
Asian Monsoon ◽  
Younger Dryas ◽  
Tropical Pacific ◽  
Last Glacial ◽  
The North ◽  
The North Atlantic ◽  
The Last Glacial

The Younger Dryas (YD), arguably the most widely studied millennial-scale extreme climate event, was characterized by diverse hydroclimate shifts globally and severe cooling at high northern latitudes that abruptly punctuated the warming trend from the last glacial to the present interglacial. To date, a precise understanding of its trigger, propagation, and termination remains elusive. Here, we present speleothem oxygen-isotope data that, in concert with other proxy records, allow us to quantify the timing of the YD onset and termination at an unprecedented subcentennial temporal precision across the North Atlantic, Asian Monsoon-Westerlies, and South American Monsoon regions. Our analysis suggests that the onsets of YD in the North Atlantic (12,870 ± 30 B.P.) and the Asian Monsoon-Westerlies region are essentially synchronous within a few decades and lead the onset in Antarctica, implying a north-to-south climate signal propagation via both atmospheric (decadal-time scale) and oceanic (centennial-time scale) processes, similar to the Dansgaard–Oeschger events during the last glacial period. In contrast, the YD termination may have started first in Antarctica at ∼11,900 B.P., or perhaps even earlier in the western tropical Pacific, followed by the North Atlantic between ∼11,700 ± 40 and 11,610 ± 40 B.P. These observations suggest that the initial YD termination might have originated in the Southern Hemisphere and/or the tropical Pacific, indicating a Southern Hemisphere/tropics to North Atlantic–Asian Monsoon-Westerlies directionality of climatic recovery.

Dynamics of the ENSO Teleconnection and NAO Variability in the North Atlantic–European Late Winter

2020 ◽  
Vol 33 (3) ◽  
pp. 907-923 ◽  
Author(s):  
Bianca Mezzina ◽  
Javier García-Serrano ◽  
Ileana Bladé ◽  
Fred Kucharski
Keyword(s):  
North Atlantic ◽  
Southern Oscillation ◽  
Reanalysis Data ◽  
Late Winter ◽  
Sea Level Pressure ◽  
The North ◽  
Nao Index ◽  
Eddy Heat Flux ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

AbstractThe winter extratropical teleconnection of El Niño–Southern Oscillation (ENSO) in the North Atlantic–European (NAE) sector remains controversial, concerning both the amplitude of its impacts and the underlying dynamics. However, a well-established response is a late-winter (January–March) signal in sea level pressure (SLP) consisting of a dipolar pattern that resembles the North Atlantic Oscillation (NAO). Clarifying the relationship between this “NAO-like” ENSO signal and the actual NAO is the focus of this study. The ENSO–NAE teleconnection and NAO signature are diagnosed by means of linear regression onto the sea surface temperature (SST) Niño-3.4 index and an EOF-based NAO index, respectively, using long-term reanalysis data (NOAA-20CR, ERA-20CR). While the similarity in SLP is evident, the analysis of anomalous upper-tropospheric geopotential height, zonal wind, and transient-eddy momentum flux, as well as precipitation and meridional eddy heat flux, suggests that there is no dynamical link between the phenomena. The observational results are further confirmed by analyzing two 10-member ensembles of atmosphere-only simulations (using an intermediate-complexity and a state-of-the-art model) with prescribed SSTs over the twentieth century. The SST-forced variability in the Northern Hemisphere is dominated by the extratropical ENSO teleconnection, which provides modest but significant SLP skill in the NAE midlatitudes. The regional internally generated variability, estimated from residuals around the ensemble mean, corresponds to the NAO pattern. It is concluded that distinct dynamics are at play in the ENSO–NAE teleconnection and NAO variability, and caution is advised when interpreting the former in terms of the latter.

scholarly journals Winter Cyclone Regimes Over The North Atlantic

2021 ◽  
Author(s):  
Veronika N. Maslova ◽  
Elena N. Voskresenskaya ◽  
Alexander V. Yurovsky ◽  
Mikhail Yu. Bardin
Keyword(s):  
North Atlantic ◽  
Reanalysis Data ◽  
East Atlantic ◽  
Teleconnection Patterns ◽  
The Third ◽  
The North ◽  
Function Decomposition ◽  
Spectral Peaks ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract To study regimes of winter cyclones in the North Atlantic, empirical orthogonal function decomposition was applied separately to the frequency, depth and area of cyclones obtained using 6-hourly NCEP/NCAR reanalysis data in 1952–2017 and the developed methodology. The first mode represented the opposite changes of cyclone anomalies in the northern and southern/central North Atlantic. The second mode was characterized by the greatest regional anomalies between its phases over Europe, off its coast and over the Mediterranean. The greatest changes of anomalies for the third modes were in temperate latitudes, both over the ocean and Europe. Linear trends were significant only for the first modes of cyclone parameters. The largest part of variability (74–90% of dispersion) of all cyclone modes corresponded to the periods up to 15 years and was used for spectral analysis, which identified significant spectral peaks: 2.5–3, 4.5, 6 and 8.5 years. These periods coincided with spectral peaks of the main interannual climate signals. Regression analysis allowed to identify the sets of teleconnection patterns responsible jointly for 60–85% of dispersion of the first cyclone modes. The North Atlantic Oscillation and Arctic Oscillation were the main patterns for the first modes of the cyclone parameters. For the second and third frequency modes, the East Atlantic (EA) pattern and a combination of the East Atlantic/West Russia (EA/WR) and Scandinavia patterns played the major role, respectively. As for the third depth and area modes, the association with the EA and EA/WR patterns was shown, respectively.

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