Drivers of North Atlantic Oscillation Events

Manola, Iris; Haarsma, Reindert J.; Hazeleger, Wilco

doi:10.3402/tellusa.v65i0.19741

Cited by 7 publications

(7 citation statements)

References 33 publications

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“…Heavy rainfall in this region is also associated with extreme winter weather over North America (Palmer, ) and northwest Europe (Lewis et al , ). Strong correlations occur with the Tropical Atlantic (TA) rainfall as seen in some other studies (Okumura et al , ; Manola et al , ). These are positive just north of the equatorial Atlantic in the model and the observations.…”

Section: Resultssupporting

confidence: 65%

“…wave‐number 3 is on this scale) and is similar to the zonal averaging used by others (e.g. Manola et al , ). As an aside, we also note that exchanging model and observed wind fields makes little difference to these Rossby wave rays, suggesting that errors in the simulation of mean zonal winds is not a significant source of error in climate model teleconnections in this model.…”

Section: Resultsmentioning

confidence: 69%

See 1 more Smart Citation

Tropical rainfall, Rossby waves and regional winter climate predictions

Scaife

Comer

Dunstone

et al. 2016

Quart J Royal Meteoro Soc

173

176

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Section: Resultssupporting

confidence: 65%

Section: Resultsmentioning

confidence: 69%

Tropical rainfall, Rossby waves and regional winter climate predictions

Scaife

Comer

Dunstone

et al. 2016

Quart J Royal Meteoro Soc

173

176

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“…This might include, for example, interactions between midlatitude cyclones and the midlatitude ocean (O'Reilly et al 2016) or the effects of resolution. Further, there are numerous diverse influences from remote forcing factors in both the tropics (e.g., Manola et al 2013) and high latitudes (e.g., Cohen et al 2014). In this section we discuss the possibility of differences in the way remote influences from the tropics could change as an example of a potential source of intermodel spread in projections of European circulation.…”

Section: Links To Tropical Precipitation Changesmentioning

confidence: 99%

Atmospheric Dynamics is the Largest Source of Uncertainty in Future Winter European Rainfall

et al. 2018

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The IPCC Fifth Assessment Report highlighted large uncertainty in European precipitation changes in the coming century. This paper investigates the sources of intermodel differences using CMIP5 model European precipitation data. The contribution of atmospheric circulation to differences in precipitation trends is investigated by applying cluster analysis to daily mean sea level pressure (MSLP) data. The resulting classification is used to reconstruct monthly precipitation time series, thereby isolating the component of precipitation variability directly related to atmospheric circulation. Reconstructed observed precipitation and reconstructions of simulated historical and projection data are well correlated with the original precipitation series, showing that circulation variability accounts for a substantial fraction of European precipitation variability. Removing the reconstructed precipitation from the original precipitation leaves a residual component related to noncirculation effects (and any small remaining circulation effects). Intermodel spread in residual future European precipitation trends is substantially reduced compared to the spread of the original precipitation trends. Uncertainty in future atmospheric circulation accounts for more than half of the intermodel variance in twenty-first-century precipitation trends for winter months for both northern and southern Europe. Furthermore, a substantial part of this variance is related to different forced dynamical responses in different models and is therefore potentially reducible. These results highlight the importance of understanding future changes in atmospheric dynamics in achieving more robust projections of regional climate change. Finally, the possible dynamical mechanisms that may drive the future differences in regional circulation and precipitation are illustrated by examining simulated teleconnections with tropical precipitation.

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“…The MCA difference is similar to a wave propagating from a GCM RWS bias in the Caribbean, and the Atlantic response is not sensitive to the basic state. Other studies also support the importance of the Caribbean as a wave source affecting the North Atlantic-European region (Manola et al 2013;Knight et al 2017), although not in an ENSO context. While the cause of our Caribbean RWS bias is inconclusive, it is possibly related to the downstream development of different wave propagation from North America due to the North Pacific jet bias.…”

Section: Conclusion and Discussionmentioning

confidence: 92%

Effect of the North Pacific Tropospheric Waveguide on the Fidelity of Model El Niño Teleconnections

Woollings

O’Reilly

et al. 2020

Journal of Climate

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In a free-running climate model, DJF tropical–extratropical teleconnections are assessed and compared to observed teleconnections in reanalysis data. From reanalysis, the leading mode of covariability between tropical outgoing longwave radiation (OLR) and Northern Hemisphere extratropical geopotential height (Z500) is identified using maximum covariance analysis (MCA). This mode relates closely to the El Niño pattern. The GCM captures the tropical OLR well but the associated extratropical Z500 less well. The GCM climatology has an equatorward shifted North Pacific jet bias. We examine whether the difference in the teleconnection pattern is related to the GCM’s jet bias. In both a ray-tracing analysis and a barotropic model, this jet bias is shown to affect the Rossby wave propagation from the tropical Pacific into the North Pacific. These idealized model results suggest qualitatively that the MCA difference is largely consistent with linear Rossby wave dynamics. While the basic state has a larger effect on the North Pacific MCA, a Rossby wave source (RWS) bias in the Caribbean has a larger effect on the North Atlantic MCA. The North Pacific jet bias is also proposed to affect the downstream propagation of waves from North America into the Caribbean, where it affects tropical RWS and the triggering of secondary waves into the North Atlantic. We propose that climatological biases in the tropics are one underlying cause of the jet bias. Our study may also help understand the results of other climate models with similar jet biases.

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Drivers of North Atlantic Oscillation Events

Cited by 7 publications

References 33 publications

Tropical rainfall, Rossby waves and regional winter climate predictions

Tropical rainfall, Rossby waves and regional winter climate predictions

Atmospheric Dynamics is the Largest Source of Uncertainty in Future Winter European Rainfall

Effect of the North Pacific Tropospheric Waveguide on the Fidelity of Model El Niño Teleconnections

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