Tropical Forcing of the Summer East Atlantic Pattern

Wulff, Ole; Greatbatch, Richard John; Domeisen, Daniela I. V.; Gollan, Gereon; Hansen, Felicitas

doi:10.1002/2017gl075493

Cited by 64 publications

(112 citation statements)

References 33 publications

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“…The surface high is followed by a surface low pressure anomaly downstream. The pattern resembles the SLP signature of a stationary Rossby wave emanating from the tropics due to positive tropical SST anomalies and associated positive precipitation anomalies (Terray and Cassou 2002;Wulff et al 2017). This aspect is further explored in the next section.…”

Section: Sea Level Pressure and Vertical Structure Of The Geopotentiamentioning

confidence: 77%

Atmospheric pathway between Atlantic multidecadal variability and European summer temperature in the atmospheric general circulation model ECHAM6

et al. 2018

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The Atlantic multidecadal variability (AMV) is known to affect the central to eastern (C-E) European summer climate through an associated atmospheric baroclinic response called North-Atlantic-European East West mode as demonstrated in the twentieth century reanalysis (20CRv2). Here, using the atmospheric model ECHAM6.3, we perform sensitivity experiments with prescribed sea surface temperature (SST) anomalies that are representative of the observed positive and the negative AMV phases and investigate the model response to the observed AMV pattern for European summer climate. The results from the experiments reveal that in the negative phase of AMV, the North-Atlantic-European (NAE) climate is mainly governed by the extra-tropical branch of the AMV through a baroclinic-like response. This response brings negative surface air temperature (SAT) anomalies over C-E Europe. The response and its influence are similar to what is found in the 20CRv2. In contrast, in the positive phase of the AMV, the NAE climate in the model experiments is mainly influenced by the tropical branch of the AMV. A stationary Rossby wave response excited in the tropics is associated with negative SAT anomalies over C-E Europe, which is opposite to what is found in the 20CRv2. The model response from the tropical part of the AMV SST is unlikely to be realistic due to the lack of coupled air-sea interaction, when SST is specified. Hence, the results demonstrate that ECHAM6.3 can simulate the observed linear baroclinic response, but only in the negative phase of the AMV. For the positive phase, in agreement with the previous findings, the model response is very sensitive to the tropical branch of the AMV and unrealistic.

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Section: Sea Level Pressure and Vertical Structure Of The Geopotentiamentioning

confidence: 77%

Atmospheric pathway between Atlantic multidecadal variability and European summer temperature in the atmospheric general circulation model ECHAM6

et al. 2018

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“…Xu et al 2019). Various teleconnection patterns have been used to explain regional anomalous rainfall (Wang 1992;Takahashi 2006, 2008;Chen and Huang 2012;Sun and Wang 2012;Lin 2014;Li and Lu 2017;Lin et al 2017a;Li and Lu 2018;Wang et al 2018), temperature (Greatbatch and Rong 2006;Hong et al 2017), and extreme events (Cassou et al 2005;Wulff et al 2017, K. Xu et al 2019. Therefore, understanding the mechanisms responsible for these teleconnections is of scientific significance and has important implications for the prediction of weather and climate over Eurasia.…”

Section: Introductionmentioning

confidence: 99%

“…Some of these teleconnections can be excited by tropical forcing and propagate poleward (e.g., Hoskins and Karoly 1981;Nitta 1987;Huang and Sun 1992;Wulff et al 2017). Some examples are: (i) the well-known Pacific-Japan pattern (Nitta 1987) or East Asian-Pacific pattern (Huang and Sun 1992), which is associated with the anomalous convection over the tropical western North Pacific (Nitta 1986, 1987Lu and Dong 2001;Lu 2004; Kosaka et al 2011) and (ii) the Summer East Atlantic mode introduced by Wulff et al (2017), which can be forced by diabatic heating anomalies of opposing signs in the tropical Pacific and Caribbean. On the other hand, some circulation modes exist without clear tropical forcing, such as the summer North Atlantic Oscillation (Feldstein 2007;Folland et al 2009) Accepted for publication in Journal of Climate.…”

Section: Introductionmentioning

confidence: 99%

“…Recent studies presented more evidences of teleconnection patterns in the high latitudes of the Eurasian continent. The Summer East Atlantic mode identified by Wulff et al (2017) is a teleconnection pattern that appears over the North Pacific, North America, North Atlantic and the high-latitude west Eurasian continent. Wulff et al (2017) suggested that this mode can be forced by diabatic heating anomalies in the tropics.…”

Section: Introductionmentioning

confidence: 99%

“…The Summer East Atlantic mode identified by Wulff et al (2017) is a teleconnection pattern that appears over the North Pacific, North America, North Atlantic and the high-latitude west Eurasian continent. Wulff et al (2017) suggested that this mode can be forced by diabatic heating anomalies in the tropics. Li and Ruan (2018) introduced a teleconnection pattern over the North Atlantic and the high latitudes of the Eurasian continent, and explained this teleconnection pattern in terms of stationary Rossby waves originating over the subtropical North Atlantic.…”

Section: Introductionmentioning

confidence: 99%

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Maintenance Mechanism for the Teleconnection Pattern over the High Latitudes of the Eurasian Continent in Summer

Greatbatch

et al. 2020

Journal of Climate

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There is a zonally oriented teleconnection pattern over the high-latitude Eurasian continent, which is maintained through baroclinic energy conversion. In this study, we investigate the unique features of the maintenance mechanism of this teleconnection. It is found that the baroclinic energy conversion is most efficient in both the midtroposphere and the lower troposphere, and that the baroclinic energy conversion in the lower troposphere is comparable to that in the midtroposphere. Further results indicate that the basic state plays a crucial role in the baroclinic energy conversion. For both the middle and lower troposphere, the atmospheric stability is low and the Coriolis parameter is large over high-latitude Eurasia, favoring strong baroclinic energy conversion. Particularly, in the lower troposphere, the atmospheric stability exhibits a clear land–sea contrast, favoring baroclinic energy conversion over the continents rather than the oceans. Furthermore, in the lower troposphere, the in-phase configuration of the meridional wind and temperature anomalies, which results from the strong meridional gradient of mean temperature around the north edge of the Eurasian continent, also significantly contributes to baroclinic energy conversion. This study highlights the role of the basic state of temperature rather than zonal wind in maintaining the high-latitude teleconnection through baroclinic energy conversion.

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Nonstationarity of the link between the Tropics and the summer East Atlantic pattern

Rieke

Greatbatch

Gollan

2021

Atmospheric Science Letters

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A 700-year pre-industrial control run with the MPI-ESM-LR model is used to investigate the link between the summer East Atlantic (SEA) pattern and the Pacific-Caribbean rainfall dipole (PCD), a link that has previously been shown using ERA-Interim reanalysis data. In the model, it is found that the link between the SEA and PCD is present in some multidecadal epochs but not in others. A simple statistical model reproduces this behaviour. In the statistical model, the SEA is represented by a white noise process plus a weak influence from the PCD based on the full 700 years of the model run. The statistical model is relevant to other extratropical modes of variability, for example, the winter North Atlantic Oscillation (NAO), that are weakly influenced by the Tropics. It follows that the link between the Tropics and the winter NAO is likely to undergo modulation on multidecadal time scales, as found in some previous studies. The results suggest that any predictability of the SEA, and by implication the NAO, based on tropical rainfall may not be robust and may, in fact, be modulated on multidecadal time scales, with implications for seasonal and decadal prediction systems.

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Tropical Forcing of the Summer East Atlantic Pattern

Cited by 64 publications

References 33 publications

Atmospheric pathway between Atlantic multidecadal variability and European summer temperature in the atmospheric general circulation model ECHAM6

Atmospheric pathway between Atlantic multidecadal variability and European summer temperature in the atmospheric general circulation model ECHAM6

Maintenance Mechanism for the Teleconnection Pattern over the High Latitudes of the Eurasian Continent in Summer

Nonstationarity of the link between the Tropics and the summer East Atlantic pattern

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