Separating the Indian and Pacific Ocean Impacts on the Euro-Atlantic Response to ENSO and Its Transition from Early to Late Winter

Abid, Muhammad Adnan; Kucharski, Fred; Molteni, Franco; Kang, In‐Sik; Tompkins, Adrian M.; Almazroui, Mansour

doi:10.1175/jcli-d-20-0075.1

Cited by 43 publications

(59 citation statements)

References 53 publications

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“…In fact, a weak low-level cyclone south of the equator in the western Indian Ocean forms a pair with the cyclone over the North Arabian Sea, Pakistan, and northwestern India (Figure 9d). Since the circulation associated with the IOBW shows a barotropic structure in southwest Asia (Figure 9c,d), our results are consistent with previous findings on the Rossby wave generated by the tropical Indian Ocean warming with an upper-level trough over southwest Asia [57,58]. Our results are also consistent with Liao and Wang [59], who documented a connection between the warming in the tropical Indian Ocean and a warming in the equatorial Atlantic during the austral summer.…”

Section: Discussionsupporting

confidence: 93%

The Role of the Indian Ocean Basin-Wide and El Niño–Southern Oscillation Modes in Interannual Rainfall Variability over South America during Austral Summer

et al. 2021

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This paper examines the relative role of the Indian Ocean basin-wide (IOBW) mode and El Niño–Southern Oscillation (ENSO) in the atmospheric circulation and rainfall interannual variations over South America (SA) during southern summer of the 1951‒2016 period. The effects of the warm IOBW and El Niño (EN) events, and of the cold IOBW and La Niña (LN) events are examined using partial correlations. The ENSO and IOBW modes, through the associated large-scale and regional anomalous circulation patterns, induce contrasting effects on the rainfall in northeastern SA. The EN without the warm IOBW effect induces anomalously dry conditions over eastern Amazon and part of northeastern Brazil (NEB) through anomalous sinking motions of the EN-related anomalous Walker and Hadley cells and strong moisture divergence associated with a vigorous anticyclone over tropical South Atlantic (TSA) and SA. The warm IOBW without the EN effect induces anomalously wet conditions in NEB, which is marginally related to the anomalous Walker and Hadley cells but is modulated by an anticyclone over SA between the equator and 20° S, and a cyclone in the southwestern Atlantic between 20° S and 40° S. The results here might be relevant for climate monitoring and modeling studies.

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Section: Discussionsupporting

confidence: 93%

The Role of the Indian Ocean Basin-Wide and El Niño–Southern Oscillation Modes in Interannual Rainfall Variability over South America during Austral Summer

et al. 2021

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“…To generate the SST pattern, we used a regression of the Niño3.4 time series and HadISST SSTs from 1979-2009. Only pos- King et al, 2018) that may be driven by SSTs and rainfall away from the Pacific (Ayarzagüena et al, 2018;Abid et al, 2021).…”

Section: Methodsmentioning

confidence: 99%

Minimal impact of model biases on Northern Hemisphere El Niño–Southern Oscillation teleconnections

Tyrrell¹,

Karpechko²

2021

Weather Clim. Dynam.

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Abstract. Correctly capturing the teleconnection between the El Niño–Southern Oscillation (ENSO) and Europe is of importance for seasonal prediction. Here we investigate how systematic model biases may affect this teleconnection. A two-step bias correction process is applied to an atmospheric general circulation model to reduce errors in the climatology. The bias corrections are applied to the troposphere and stratosphere independently and jointly to produce a range of climates. ENSO-type sensitivity experiments are then performed to reveal the impact of differing climatologies on the ENSO–Europe teleconnections. The bias corrections do not affect the response of the tropical atmosphere or the Aleutian low to the strong ENSO anomalies imposed in our experiments. However, in El Niño experiments the anomalous upward wave flux and the response of the Northern Hemisphere polar vortex differ between the climatologies. We attribute this to a reduced sensitivity of the upward wave fluxes to the Aleutian low response in the bias correction experiments, where the reduced biases result in a deepened Aleutian low in the base state. Despite the differing responses of the polar vortex, the North Atlantic Oscillation (NAO) response is similar between the climatologies, implying that for strong ENSO events the stratospheric pathway may not be the dominant pathway for the ENSO–North Atlantic teleconnection.

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“…After many decades of research, interest in ENSO teleconnections in the North Atlantic remains high and new results continue to appear (e.g., recent review by Domeisen et al 2018). A number of recent studies have contributed to the continuous improvement in understanding the mechanisms behind the ENSO teleconnection to the North Atlantic, including details about how the late fall signal may arise from an atmospheric bridge via the tropical Atlantic (Ayarzagüena et al 2018;King et al 2018a) or diabatic heating over the Indian Ocean (Abid et al 2020;Joshi et al 2020). Such studies have also found that "free-running" coupled model or SST-forced atmospheric model experiments do not, or only weakly, reproduce the ENSO teleconnection to the North Atlantic through the cold season, while intialized hindcasts perform better.…”

Section: Confidence Intervals and T-testmentioning

confidence: 99%

Resampling of ENSO teleconnections: accounting for cold season evolution reduces uncertainty in the North Atlantic

King¹,

Li²,

Sobolowski³

2021

Preprint

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Abstract. We re-examine the uncertainty of the El Niño–Southern Oscillation teleconnection to the North Atlantic following the investigation of Deser et al. (2017) (DES2017). Our analyses are performed on the November–December (ND) and January–February (JF) means separately, and for a geographical area that covers a larger extent in the midlatitude North At- lantic than DES2017. The motivation for splitting the cold season in this way arises from the fact that the teleconnection patterns and underlying physical mechanisms are different in late fall compared to mid-winter. As in DES2017, our main technique in quantifying the uncertainty is bootstrap resampling. Amplitudes and spatial correlations of the bootstrap samples are presented together effectively using Taylor diagrams. In addition to the confidence intervals calculated from Student's t tests and the percentiles of anomalous sea-level pressure (SLP) values in the bootstrap samples, we also investigate additional confidence intervals using techniques that are not widely used in climate research, but have different advantages. In contrast to the interpretation by DES2017, our results indicate that we can have some confidence in the signs of the teleconnection SLP anomalies. The uncertainties in the amplitudes remain large, with the upper-percentile anomalies at up to 2 times those of the lower percentiles in the North Pacific, and 2.8 times in the North Atlantic.

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Separating the Indian and Pacific Ocean Impacts on the Euro-Atlantic Response to ENSO and Its Transition from Early to Late Winter

Cited by 43 publications

References 53 publications

The Role of the Indian Ocean Basin-Wide and El Niño–Southern Oscillation Modes in Interannual Rainfall Variability over South America during Austral Summer

The Role of the Indian Ocean Basin-Wide and El Niño–Southern Oscillation Modes in Interannual Rainfall Variability over South America during Austral Summer

Minimal impact of model biases on Northern Hemisphere El Niño–Southern Oscillation teleconnections

Resampling of ENSO teleconnections: accounting for cold season evolution reduces uncertainty in the North Atlantic

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