The variable link between PNA and NAO in observations and in multi-century CGCM simulations

Pinto, Joaquim G.; Reyers, Mark; Ulbrich, Uwe

doi:10.1007/s00382-010-0770-x

Cited by 66 publications

(59 citation statements)

References 77 publications

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“…Raible et al (2001) identified periods during which decadal-scale variability of the NAO coincides with strong coupling of the atmosphere to the ocean underneath, whereas periods dominated by interannual variability seem to be related to tropical SST changes in the Pacific. In line with these changes, the coupling between the Atlantic and Pacific is found to be variable over time (Raible et al, 2004;Pinto et al, 2011). Other reasons such as stratosphere-troposphere interaction (Kodera et al, 1996;Woollings et al, 2010a) or sea-ice interaction with the atmosphere (e.g.…”

Section: Climmentioning

confidence: 78%

Changing correlation structures of the Northern Hemisphere atmospheric circulation from 1000 to 2100 AD

et al. 2014

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Abstract. Atmospheric circulation modes are important concepts in understanding the variability of atmospheric dynamics. Assuming their spatial patterns to be fixed, such modes are often described by simple indices from rather short observational data sets. The increasing length of reanalysis products allows these concepts and assumptions to be scrutinised. Here we investigate the stability of spatial patterns of Northern Hemisphere teleconnections by using the Twentieth Century Reanalysis as well as several control and transient millennium-scale simulations with coupled models. The observed and simulated centre of action of the two major teleconnection patterns, the North Atlantic Oscillation (NAO) and to some extent the Pacific North American (PNA), are not stable in time. The currently observed dipole pattern of the NAO, its centre of action over Iceland and the Azores, split into a north-south dipole pattern in the western Atlantic with a wave train pattern in the eastern part, connecting the British Isles with West Greenland and the eastern Mediterranean during the period 1940-1969 AD. The PNA centres of action over Canada are shifted southwards and over Florida into the Gulf of Mexico during the period 1915-1944 AD. The analysis further shows that shifts in the centres of action of either teleconnection pattern are not related to changes in the external forcing applied in transient simulations of the last millennium. Such shifts in their centres of action are accompanied by changes in the relation of local precipitation and temperature with the overlying atmospheric mode. These findings further undermine the assumption of stationarity between local climate/proxy variability and large-scale dynamics inherent when using proxy-based reconstructions of atmospheric modes, and call for a more robust understanding of atmospheric variability on decadal timescales.

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Section: Climmentioning

confidence: 78%

Changing correlation structures of the Northern Hemisphere atmospheric circulation from 1000 to 2100 AD

et al. 2014

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“…Second, there is a clear Rossby wave train pattern arching from the Pacific into the Atlantic. Several studies have shown that the propagation of wave activity from the Pacific to the Atlantic can be an important factor in the onset of jet stream regimes in the North Atlantic (Franzke et al 2004;Strong and Magnusdottir 2008a,b;Cassou 2008;Lin et al 2009;Pinto et al 2011). Figure 7 shows the subsequent evolution of the streamfunction.…”

Section: Dynamical Analysismentioning

confidence: 99%

“…One possibility is that the remnants of the low-frequency Pacific wave train act to enhance the Atlantic transient eddy activity, perhaps by encouraging advection of air along the strong baroclinic zone over the east coast of North America (cf. Pinto et al 2011).…”

Section: Dynamical Analysismentioning

confidence: 99%

Dynamical Evolution of North Atlantic Ridges and Poleward Jet Stream Displacements

Woollings

Pinto

Santos

2011

Journal of the Atmospheric Sciences

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The development of a particular wintertime atmospheric circulation regime over the North Atlantic, comprising a northward shift of the North Atlantic eddy-driven jet stream and an associated strong and persistent ridge in the subtropics, is investigated. Several different methods of analysis are combined to describe the temporal evolution of the events and relate it to shifts in the phase of the North Atlantic Oscillation and East Atlantic pattern. First, the authors identify a close relationship between northward shifts of the eddydriven jet, the establishment and maintenance of strong and persistent ridges in the subtropics, and the occurrence of upper-tropospheric anticyclonic Rossby wave breaking over Iberia. Clear tropospheric precursors are evident prior to the development of the regime, suggesting a preconditioning of the Atlantic jet stream and an upstream influence via a large-scale Rossby wave train from the North Pacific. Transient (2-6 days) eddy forcing plays a dual role, contributing to both the initiation and then the maintenance of the circulation anomalies. During the regime there is enhanced occurrence of anticyclonic Rossby wave breaking, which may be described as low-latitude blocking-like events over the southeastern North Atlantic. A strong ridge is already established at the time of wave-breaking onset, suggesting that the role of wave-breaking events is to amplify the circulation anomalies rather than to initiate them. Wave breaking also seems to enhance the persistence, since it is unlikely that a persistent ridge event occurs without being also accompanied by wave breaking.

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“…Occasionally, the GS activity can affect Europe (Stohl et al 2008;Lavers et al 2011). The GS maximum has also been hypothesized to play a role in linking large-scale climate fluctuations between the North Pacific/North America and the North Atlantic (Pinto et al 2011).…”

Section: Introductionmentioning

confidence: 99%

A Global Climatology of Tropical Moisture Exports

2013

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In a recent paper, a climatology of tropical moisture exports (TMEs) to the Northern Hemisphere (NH) was constructed on the basis of 7-day forward trajectories, started daily from the tropical lower troposphere, which were required to reach a water vapor flux of at least 100 g kg 21 m s 21 somewhere north of 358N. It was shown that TMEs contribute significantly to regional precipitation. Here, the authors complement and extend this work by (i) using 6-hourly European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) data from 1979 to 2010 instead of the earlier 40-yr ECMWF Re-Analysis (ERA-40), (ii) extending the climatology to the Southern Hemisphere (SH), and (iii) relating TME events to atmospheric rivers (ARs) previously discussed in the literature. The main conclusions are as follows: First, the TME climatology is not sensitive to the reanalysis dataset. Second, SH TME shows four activity centers: the central and eastern Pacific Ocean (1708-908W, near the South Pacific convergence zone), eastern South America and the adjacent Atlantic Ocean (608W-08, near the South Atlantic convergence zone), the western Indian Ocean (308-808E), and western Australia (1108-1408E). Third, TME activity in the SH peaks in austral summer because of higher moisture contents and possibly because of increased Rossby wave activity from the NH. Fourth, El Niñ o warm events are associated with reduced activity over the South Pacific and increased activity over the South Atlantic and around Australia, while correlations with the southern annular mode are generally weak. Finally, around 90% of all ARs affecting the U.S. West Coast during December-May are connected to TME events, revealing their importance for heavy rain and flooding.

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The variable link between PNA and NAO in observations and in multi-century CGCM simulations

Cited by 66 publications

References 77 publications

Changing correlation structures of the Northern Hemisphere atmospheric circulation from 1000 to 2100 AD

Changing correlation structures of the Northern Hemisphere atmospheric circulation from 1000 to 2100 AD

Dynamical Evolution of North Atlantic Ridges and Poleward Jet Stream Displacements

A Global Climatology of Tropical Moisture Exports

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