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

The Effect of the South Pacific Convergence Zone on the Termination of El Niño Events and the Meridional Asymmetry of ENSO*

2012 ◽  
Vol 25 (16) ◽  
pp. 5566-5586 ◽  
Author(s):  
Shayne McGregor ◽  
Axel Timmermann ◽  
Niklas Schneider ◽  
Malte F. Stuecker ◽  
Matthew H. England
Keyword(s):  
Boundary Layer ◽  
El Niño ◽  
El Nino ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Wind Speeds ◽  
Wind Response ◽  
El Niño Events ◽  
El Nino Events

Abstract During large El Niño events the westerly wind response to the eastern equatorial Pacific sea surface temperature anomalies (SSTAs) shifts southward during boreal winter and early spring, reaching latitudes of 5°–7°S. The resulting meridional asymmetry, along with a related seasonal weakening of wind anomalies on the equator are key elements in the termination of strong El Niño events. Using an intermediate complexity atmosphere model it is demonstrated that these features result from a weakening of the climatological wind speeds south of the equator toward the end of the calendar year. The reduced climatological wind speeds, which are associated with the seasonal intensification of the South Pacific convergence zone (SPCZ), lead to anomalous boundary layer Ekman pumping and a reduced surface momentum damping of the combined boundary layer/lower-troposphere surface wind response to El Niño. This allows the associated zonal wind anomalies to shift south of the equator. Furthermore, using a linear shallow-water ocean model it is demonstrated that this southward wind shift plays a prominent role in changing zonal mean equatorial heat content and is solely responsible for establishing the meridional asymmetry of thermocline depth in the turnaround (recharge/discharge) phase of ENSO. This result calls into question the sole role of oceanic Rossby waves in the phase synchronized termination of El Niño events and suggests that the development of a realistic climatological SPCZ in December–February/March–May (DJF/MAM) is one of the key factors in the seasonal termination of strong El Niño events.

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 Stronger Increase in the Frequency of Extreme Convective than Extreme Warm El Niño Events under Greenhouse Warming

2020 ◽  
Vol 33 (2) ◽  
pp. 675-690 ◽  
Author(s):  
Guojian Wang ◽  
Wenju Cai ◽  
Agus Santoso
Keyword(s):  
El Niño ◽  
El Nino ◽  
South Pacific Convergence Zone ◽  
Boreal Winter ◽  
Greenhouse Warming ◽  
Convergence Zone ◽  
Central Pacific ◽  
Mixed Regime ◽  
El Niño Events ◽  
El Nino Events

AbstractSince 1979, three extreme El Niño events occurred, in 1982/83, 1997/98, and 2015/16, with pronounced impacts that disrupted global weather patterns, agriculture, fisheries, and ecosystems. Although all three episodes are referred to as strong equatorial eastern Pacific (EP) El Niño events, the 2015/16 event is considered a mixed regime of both EP and central Pacific (CP) El Niño. During such extreme events, sea surface temperature (SST) anomalies peak over the EP region, hereafter referred to as an extreme warm El Niño (ExtWarmEN) event. Simultaneously, the intertropical convergence zone (ITCZ) moves southward to the usually dry and cold Niño-3 region, resulting in dramatic rainfall increases to more than 5 mm day−1 averaged over boreal winter, referred to as an extreme convective El Niño (ExtConEN) event. However, in climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) that are able to simulate both types of events, ExtConEN events are found not to always coincide with ExtWarmEN events and the disassociation becomes more distinct under greenhouse warming when the increased frequency of ExtConEN events is notably larger than that of ExtWarmEN events. The disassociation highlights the role of eastward migration of western Pacific convection and equatorward shift of the South Pacific convergence zone associated with the faster warming over the EP region as a result of greenhouse warming.

scholarly journals Characterization of the Variability of the South Pacific Convergence Zone Using Satellite and Reanalysis Wind Products

2016 ◽  
Vol 29 (5) ◽  
pp. 1717-1732 ◽  
Author(s):  
Autumn Kidwell ◽  
Tong Lee ◽  
Young-Heon Jo ◽  
Xiao-Hai Yan
Keyword(s):  
Time Scales ◽  
El Niño ◽  
El Nino ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Multiple Time Scales ◽  
Convergence Zone ◽  
Multiple Time ◽  
The South ◽  
Central Pacific

Abstract The variability of the South Pacific convergence zone (SPCZ) is evaluated using ocean surface wind products derived from the atmospheric reanalysis ERA-Interim for the period of 1981–2014 and QuickSCAT for the period of 1999–2009. From these products, indices were developed to represent the SPCZ strength, area, and centroid location. Excellent agreement is found between the indices derived from the two wind products during the QuikSCAT period in terms of the spatiotemporal structures of the SPCZ. The longer ERA-Interim product is used to study the variations of SPCZ properties on intraseasonal, seasonal, interannual, and decadal time scales. The SPCZ strength, area, and centroid latitude have a dominant seasonal cycle. In contrast, the SPCZ centroid longitude is dominated by intraseasonal variability due to MJO influence. The SPCZ indices are all correlated with El Niño–Southern Oscillation indices. Interannual and intraseasonal variations of SPCZ strength during strong El Niño are approximately twice as large as the respective seasonal variations. SPCZ strength depends more on the intensity of El Niño rather than the central-Pacific versus eastern-Pacific type. The change from positive to negative Pacific decadal oscillation (PDO) around 1999 results in a westward shift of the SPCZ centroid longitude, a much smaller interannual swing in centroid latitude, and a decrease in SPCZ area. This study improves the understanding of the variations of the SPCZ on multiple time scales and reveals the variations of SPCZ strength not reported previously. The diagnostics analyses can be used to evaluate climate models to gauge their fidelity.

scholarly journals Seasonal and interannual (ENSO) climate variabilities and trends in the South China Sea over the last three decades

2018 ◽  
Author(s):  
Violaine Piton ◽  
Thierry Delcroix
Keyword(s):  
South China Sea ◽  
El Niño ◽  
El Nino ◽  
The South ◽  
The North ◽  
Meridional Winds ◽  
El Niño Events ◽  
The Mean ◽  
Increasing Trends ◽  
El Nino Events

Abstract. We present a short overview of the long-term mean and variability of five Essential Climate Variables observed in the South China Sea over the last 3 decades, including sea surface temperature (SST), sea level anomaly (SLA), precipitation (P), surface wind and water discharge (WD) from the Mekong and Red Rivers. At the seasonal time scale, SST and SLAs increase in the summer (up to 4.2 °C and 14 cm, respectively), and P increases in the north. The summer zonal and meridional winds reverse and intensify (mostly over the ocean), and the WD shows positive anomalies. At the interannual time scale, each variable appears to be correlated with El Niño Southern Oscillation (ENSO) indices. Eastern Pacific El Niño events produce basin-wide SST warming (up to 1.4 °C) with a 6-month lag. The SLAs fall basin-wide (by up to 9 cm) during an El Niño event (all types), with a 3-month lag. The zonal and meridional winds strengthen (up to 4 m/s) in the north (weaken in the south) during all types of El Niño events, with a 3–5-month lag. A rainfall deficit of approximately 30 % of the mean occurs during all types of El Niño phases. The Mekong River WD is reduced by 1/3 of the mean 7–8 months after all types of El Niño events. We also show increasing trends of SST as high as 0.24 °C/decade and SLAs by 41 mm/decade. Increasing trends are observed for zonal wind, which is possibly linked to the phase of the Pacific Decadal Oscillation, and decreasing trends are observed for P in the north and both WD stations that were analyzed. The likely driving mechanisms and some of the relationships between all observed anomalies are discussed

Super instrumental El Niño events recorded by a Porites coral from the South China Sea

Coral Reefs ◽  
2018 ◽  
Vol 37 (1) ◽  
pp. 295-308 ◽  
Author(s):  
Xijie Wang ◽  
Wenfeng Deng ◽  
Xi Liu ◽  
Gangjian Wei ◽  
Xuefei Chen ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
El Niño ◽  
El Nino ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Porites Coral ◽  
El Niño Events ◽  
El Nino Events
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