El Niño Flavors and Their Simulated Impacts on Atmospheric Circulation in the High Southern Latitudes*

2014 ◽  
Vol 27 (23) ◽  
pp. 8934-8955 ◽  
Author(s):  
Aaron B. Wilson ◽  
David H. Bromwich ◽  
Keith M. Hines ◽  
Sheng-hung Wang
Keyword(s):  
Atmospheric Circulation ◽  
High Latitude ◽  
El Niño ◽  
El Nino ◽  
South Pacific ◽  
Tropical Pacific ◽  
The South ◽  
Wave Source ◽  
South Central ◽  
El Niño Flavors

Abstract Two El Niño flavors have been defined based on whether warm sea surface temperature (SST) anomalies are located in the central or eastern tropical Pacific (CP or EP). This study further characterizes the impacts on atmospheric circulation in the high latitudes of the Southern Hemisphere associated with these types of El Niño events though a series of numerical simulations using the National Center for Atmospheric Research Community Atmosphere Model (CAM). Comparing results with the Interim ECMWF Re-Analysis (ERA-Interim), CAM simulates well the known changes to blocking over Australia and a southward shift in the subtropical jet stream across the eastern Pacific basin during CP events. More importantly for the high southern latitudes, CAM simulates a westward shift in upper-level divergence in the tropical Pacific, which causes the Pacific–South American stationary wave pattern to shift toward the west across the entire South Pacific. These changes to the Rossby wave source region impact the South Pacific convergence zone and jet streams and weaken the high-latitude blocking that is typically present in the Amundsen-Bellingshausen Seas during EP events. Anticyclonic flow becomes established farther west in the south central Pacific, modifying high-latitude heat and momentum fluxes across the South Pacific and South Atlantic associated with the ENSO–Antarctic dipole.

The Contribution of Boreal Spring South Pacific Atmospheric Variability to El Niño Occurrence

2020 ◽  
Vol 33 (19) ◽  
pp. 8301-8313
Author(s):  
Qingye Min ◽  
Renhe Zhang
Keyword(s):  
El Niño ◽  
El Nino ◽  
South Pacific ◽  
Tropical Pacific ◽  
The South ◽  
Atmospheric Variability ◽  
Boreal Spring ◽  
El Niño Events ◽  
El Nino Events ◽  
The Tropical Pacific

AbstractDespite the fact that great efforts have been made to improve the prediction of El Niño events, it remains challenging because of limited understanding of El Niño and its precursors. This research focuses on the influence of South Pacific atmospheric variability on the development of the sea surface temperature anomaly (SSTA) in the tropical Pacific. It is found that as early as in the boreal spring of El Niño years, the sea level pressure anomaly (SLPA) shows a configuration characterized by two significant negative anomaly centers in the north and a positive anomaly center in the south between the subtropics and high latitudes in South Pacific. Such an anomalous SLPA pattern becomes stronger in the following late boreal spring and summer associated with the strengthening of westerly anomalies in the tropical Pacific, weakening the southeasterly trade winds and promoting the warming of tropical eastern Pacific, which is conducive to the development of El Niño events. It is demonstrated that the SLPA pattern in boreal spring revealed in this study is closely associated with boreal summer South Pacific Oscillation (SPO) and South Pacific meridional mode (SPMM). As a precursor in boreal spring, the prediction skill of the South Pacific SLPA in boreal spring for the SSTA in the eastern equatorial Pacific is better than that of the SPMM. This study is helpful to deepen our understanding of the contribution of South Pacific extratropical atmospheric variability to El Niño occurrence.

scholarly journals Simulating the Mutual Forcing of Anomalous High Southern Latitude Atmospheric Circulation by El Niño Flavors and the Southern Annular Mode*

2016 ◽  
Vol 29 (6) ◽  
pp. 2291-2309 ◽  
Author(s):  
Aaron B. Wilson ◽  
David H. Bromwich ◽  
Keith M. Hines
Keyword(s):  
Atmospheric Circulation ◽  
High Latitude ◽  
El Niño ◽  
El Nino ◽  
Southern Annular Mode ◽  
Spatial And Temporal Variability ◽  
Transient Eddy ◽  
Annular Mode ◽  
Tropical Forcing ◽  
El Niño Flavors

Abstract Numerical simulations using the National Center for Atmospheric Research Community Atmosphere Model (CAM) are conducted based on tropical forcing of El Niño flavors. Though these events occur on a continuum, two general types are simulated based on sea surface temperature anomalies located in the central (CP) or eastern (EP) tropical Pacific. The goal is to assess whether CAM adequately represents the transient eddy dynamics associated with each of these El Niño flavors under different southern annular mode (SAM) regimes. CAM captures well the wide spatial and temporal variability associated with the SAM but only accurately simulates the impacts on atmospheric circulation in the high southern latitudes when the observed SAM phase is matched by the model. Composites of in-phase (El Niño–SAM−) and out-of-phase (El Niño–SAM+) events confirm a seasonal preference for in-phase (out of phase) events during December–February (DJF) [June–August (JJA)]. Modeled in-phase events for both EP (during DJF) and CP (during JJA) conditions support observations of anomalous equatorward momentum flux on the equatorward side of the eddy-driven jet, shifting this jet equatorward and consistent with the low phase of the SAM. Out-of-phase composites show that the El Niño–associated teleconnection to the high southern latitudes is strongly modulated by the SAM, as a strong eddy-driven jet is well maintained by high-latitude transient eddy convergence despite the tropical forcing. A regional perspective confirms that this interaction takes place primarily over the Pacific Ocean, with high-latitude circulation variability being a product of both tropical and high-latitude forcing.

scholarly journals The role of the South Pacific in modulating Tropical Pacific variability

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Christine T. Y. Chung ◽  
Scott B. Power ◽  
Arnold Sullivan ◽  
François Delage
Keyword(s):  
El Niño ◽  
Decadal Variability ◽  
El Nino ◽  
South Pacific ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
La Niña ◽  
The South ◽  
La Nina ◽  
Sst Anomalies

AbstractTropical Pacific variability (TPV) heavily influences global climate, but much is still unknown about its drivers. We examine the impact of South Pacific variability on the modes of TPV: the El Niño-Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO). We conduct idealised coupled experiments in which we suppress temperature and salinity variability at all oceanic levels in the South Pacific. This reduces decadal variability in the equatorial Pacific by ~30% and distorts the spatial pattern of the IPO. There is little change to overall interannual variability, however there is a decrease in the magnitude of the largest 5% of both El Niño and La Niña sea-surface temperature (SST) anomalies. Possible reasons for this include: (i) reduced decadal variability means that interannual SST variability is superposed onto a ‘flatter’ background signal, (ii) suppressing South Pacific variability leads to the alteration of coupled processes linking the South and equatorial Pacific. A small but significant mean state change arising from the imposed suppression may also contribute to the weakened extreme ENSO SST anomalies. The magnitude of both extreme El Niño and La Niña SST anomalies are reduced, and the associated spatial patterns of change of upper ocean heat content and wind stress anomalies are markedly different for both types of events.

scholarly journals Extreme swings of the South Pacific Convergence Zone and the different types of El Niño events

2014 ◽  
Vol 41 (13) ◽  
pp. 4695-4703 ◽  
Author(s):  
Simon Borlace ◽  
Agus Santoso ◽  
Wenju Cai ◽  
Matt Collins
Keyword(s):  
El Niño ◽  
El Nino ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
The South ◽  
Different Types ◽  
El Niño Events ◽  
El Nino Events

scholarly journals Tropical Cyclone Climatology of the South Pacific Ocean and Its Relationship to El Niño–Southern Oscillation

2012 ◽  
Vol 25 (18) ◽  
pp. 6108-6122 ◽  
Author(s):  
Andrew J. Dowdy ◽  
Lixin Qi ◽  
David Jones ◽  
Hamish Ramsay ◽  
Robert Fawcett ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
Large Scale ◽  
Critical Line ◽  
El Nino ◽  
Southern Oscillation ◽  
South Pacific ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
The South

Abstract Climatological features of tropical cyclones in the South Pacific Ocean have been analyzed based on a new archive for the Southern Hemisphere. A vortex tracking and statistics package is used to examine features such as climatological maps of system intensity and the change in intensity with time, average tropical cyclone system movement, and system density. An examination is presented of the spatial variability of these features, as well as changes in relation to phase changes of the El Niño–Southern Oscillation phenomenon. A critical line is defined in this study based on maps of cyclone intensity to describe the statistical geographic boundary for cyclone intensification. During El Niño events, the critical line shifts equatorward, while during La Niña events the critical line is generally displaced poleward. Regional variability in tropical cyclone activity associated with El Niño–Southern Oscillation phases is examined in relation to the variability of large-scale atmospheric or oceanic variables associated with tropical cyclone activity. Maps of the difference fields between different phases of El Niño–Southern Oscillation are examined for sea surface temperature, vertical wind shear, lower-tropospheric vorticity, and midtropospheric relative humidity. Results are also examined in relation to the South Pacific convergence zone. The common region where each of the large-scale variables showed favorable conditions for cyclogenesis coincided with the location of maximum observed cyclogenesis for El Niño events as well as for La Niña years.

The Tropical Atmospheric Energy Budget from the TRMM Perspective. Part II: Evaluating GCM Representations of the Sensitivity of Regional Energy and Water Cycles to the 1998–99 ENSO Cycle

2007 ◽  
Vol 20 (18) ◽  
pp. 4548-4571 ◽  
Author(s):  
Tristan S. L’Ecuyer ◽  
Graeme L. Stephens
Keyword(s):  
Atmospheric Circulation ◽  
El Niño ◽  
Climate Models ◽  
El Nino ◽  
Tropical Pacific ◽  
Regional Energy ◽  
El Niño Event ◽  
Current Climate ◽  
The Tropical Pacific ◽  
Water Cycles

Abstract The impact of clouds and precipitation on the climate is a strong function of their spatial distribution and microphysical properties, characteristics that depend, in turn, on the environments in which they form. Simulating feedbacks between clouds, precipitation, and their surroundings therefore places an enormous burden on the parameterized physics used in current climate models. This paper uses multisensor observations from the Tropical Rainfall Measuring Mission (TRMM) to assess the representation of the response of regional energy and water cycles in the tropical Pacific to the strong 1998 El Niño event in (Atmospheric Model Intercomparison Project) AMIP-style simulations from the climate models that participated in the Intergovernmental Panel on Climate Change’s (IPCC’s) most recent assessment report. The relationship between model errors and uncertainties in their representation of the impacts of clouds and precipitation on local energy budgets is also explored. With the exception of cloud radiative impacts that are often overestimated in both regions, the responses of atmospheric composition and heating to El Niño are generally captured in the east Pacific where the SST forcing is locally direct. Many models fail, however, to correctly predict the magnitude of induced trends in the west Pacific where the response depends more critically on accurate representation of the zonal atmospheric circulation. As a result, a majority of the models examined do not reproduce the apparent westward transport of energy in the equatorial Pacific during the 1998 El Niño event. Furthermore, the intermodel variability in the responses of precipitation, total heating, and vertical motion is often larger than the intrinsic ENSO signal itself, implying an inherent lack of predictive capability in the ensemble with regard to the response of the mean zonal atmospheric circulation in the tropical Pacific to ENSO. While ENSO does not necessarily provide a proxy for anthropogenic climate change, the results suggest that deficiencies remain in the representation of relationships between radiation, clouds, and precipitation in current climate models that cannot be ignored when interpreting their predictions of future climate.

scholarly journals Record warming in the South Pacific and western Antarctica associated with the strong central-Pacific El Niño in 2009-10

2010 ◽  
Vol 37 (19) ◽  
pp. n/a-n/a ◽  
Author(s):  
Tong Lee ◽  
William R. Hobbs ◽  
Joshua K. Willis ◽  
Daria Halkides ◽  
Ichiro Fukumori ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
South Pacific ◽  
The South ◽  
Central Pacific ◽  
Central Pacific El Niño
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