Variability of the western Pacific warm pool structure associated with El Niño

2016 ◽  
Vol 49 (7-8) ◽  
pp. 2431-2449 ◽  
Author(s):  
Shijian Hu ◽  
Dunxin Hu ◽  
Cong Guan ◽  
Nan Xing ◽  
Jianping Li ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Warm Pool ◽  
Western Pacific ◽  
Western Pacific Warm Pool ◽  
Pacific Warm Pool ◽  
The Western Pacific

How Many ENSO Flavors Can We Distinguish?*

2013 ◽  
Vol 26 (13) ◽  
pp. 4816-4827 ◽  
Author(s):  
Nathaniel C. Johnson
Keyword(s):  
El Niño ◽  
El Nino ◽  
Warm Pool ◽  
Tropical Pacific ◽  
La Niña ◽  
Western Pacific ◽  
Western Pacific Warm Pool ◽  
La Nina ◽  
Pacific Warm Pool ◽  
Sst Anomalies

Abstract It is now widely recognized that El Niño–Southern Oscillation (ENSO) occurs in more than one form, with the canonical eastern Pacific (EP) and more recently recognized central Pacific (CP) ENSO types receiving the most focus. Given that these various ENSO “flavors” may contribute to climate variability and long-term trends in unique ways, and that ENSO variability is not limited to these two types, this study presents a framework that treats ENSO as a continuum but determines a finite maximum number of statistically distinguishable representative ENSO patterns. A neural network–based cluster analysis called self-organizing map (SOM) analysis paired with a statistical distinguishability test determines nine unique patterns that characterize the September–February tropical Pacific SST anomaly fields for the period from 1950 through 2011. These nine patterns represent the flavors of ENSO, which include EP, CP, and mixed ENSO patterns. Over the 1950–2011 period, the most significant trends reflect changes in La Niña patterns, with a shift in dominance of La Niña–like patterns with weak or negative western Pacific warm pool SST anomalies until the mid-1970s, followed by a dominance of La Niña–like patterns with positive western Pacific warm pool SST anomalies, particularly after the mid-1990s. Both an EP and especially a CP El Niño pattern experienced positive frequency trends, but these trends are indistinguishable from natural variability. Overall, changes in frequency within the ENSO continuum contributed to the pattern of tropical Pacific warming, particularly in the equatorial eastern Pacific and especially in relation to changes of La Niña–like rather than El Niño–like patterns.

scholarly journals Precession cycles of the El Niño/Southern oscillation-like system controlled by Pacific upper-ocean stratification

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Shuai Zhang ◽  
Zhoufei Yu ◽  
Xun Gong ◽  
Yue Wang ◽  
Fengming Chang ◽  
...  
Keyword(s):  
El Nino ◽  
Southern Oscillation ◽  
Warm Pool ◽  
Western Pacific ◽  
Upper Ocean ◽  
Western Pacific Warm Pool ◽  
Ocean Stratification ◽  
Pacific Warm Pool ◽  
Meridional Overturning ◽  
The Western Pacific

AbstractModern observations have presented linkages between subsurface waters of the western Pacific warm pool and both El Niño/Southern Oscillation-related and extratropic-controlled upper-ocean stratification on interannual timescales. Moreover, studies have showed that such controls may operate on orbital cycles, although the details remain unclear. Here we present paired temperature and salinity reconstructions for the surface and thermocline waters in the central western Pacific warm pool over the past 360,000 years, as well as transit modeling results from an Earth system model. Our results show that variations in subsurface temperature and salinity in the western Pacific warm pool have consistently correlated with the shallow meridional overturning cell over the past four glacial-interglacial cycles, and they vary on eccentricity and precession cycles. The shallow meridional overturning cell regulates subsurface waters of the western Pacific warm pool by changing subtropical surface water density and thus equatorial upper-ocean stratification, acting as an El Niño/Southern Oscillation-like process in the precession band. Therefore, the western Pacific warm pool is critical in connecting the austral shallow meridional overturning cell to the Earth’s climate system on orbital timescales.

A Common Base Mode of Asian Summer Monsoon Variability across Timescales

2021 ◽  
pp. 1-38
Author(s):  
Xudong Wang ◽  
Shang-Ping Xie ◽  
Zhaoyong Guan ◽  
Minyang Wang
Keyword(s):  
Summer Monsoon ◽  
El Niño ◽  
El Nino ◽  
Asian Summer Monsoon ◽  
Warm Pool ◽  
Western Pacific ◽  
Western Pacific Warm Pool ◽  
Monsoon Variability ◽  
Pacific Warm Pool ◽  
Asian Summer

AbstractThe summer intraseasonal oscillation (ISO) is characterized by a northward-moving rain band in the Indo-western Pacific warm pool region. Physical origin of the ISO is not fully understood, masked by strong interaction of convection and circulation. This study examines intraseasonal to interannual variability during June to August over the Indo-western Pacific warm pool region. The results show that the tropical Northwest Pacific anomalous anticyclone (NWP-AAC) is a fundamental mode on both intraseasonal and interannual timescales, destabilized by the monsoon mean state, specifically through barotropic energy conversion and convective feedback in the low-level confluence between the monsoon westerlies and easterly trade winds. On the interannual timescale, the NWP-AAC shows a biennial tendency, reversing phase from the summer of El Niño to the summer that follows; the AAC in post-El Niño summer is excited indirectly through sea surface temperature anomalies in the Indo-NWP. On the intraseasonal timescale, the column-integrated moisture advection causes the NWP-AAC-related convection propagates northward. Our results provide a unifying view of multi-scale Asian summer monsoon variability, with important implications for subseasonal to seasonal prediction.

A Study of the Impact of Off-Equatorial Warm Pool SST Anomalies on ENSO Cycles

2005 ◽  
Vol 18 (2) ◽  
pp. 274-286 ◽  
Author(s):  
Amy Solomon ◽  
Fei-Fei Jin
Keyword(s):  
El Niño ◽  
El Nino ◽  
Coupled Model ◽  
Warm Pool ◽  
Western Pacific ◽  
Sea Surface ◽  
Pacific Warm Pool ◽  
The Impact ◽  
The Western Pacific ◽  
Sst Anomalies

Abstract Concurrent with most large El Niño events, cold sea surface temperature (SST) anomalies are observed over the western Pacific warm pool region (WPWP). Observational evidence that SST anomalies that form in the off-equatorial western Pacific during El Niño–Southern Oscillation (ENSO) cycles are forced by subsurface ocean processes equatorward of 12°N and air–sea fluxes poleward of 12°N is presented. It is demonstrated that diurnal mixing in the ocean equatorward of 12°N plays a significant role in bringing subsurface temperature anomalies to the sea surface during an El Niño event. The role of SST anomalies equatorward of 12°N in ENSO cycles is tested in the Zebiak–Cane coupled model, modified to allow for the impact of subsurface temperatures on SSTs. This coupled model successfully simulates cold SST anomalies in the off-equatorial northwestern Pacific that are observed to occur during the warm phase of ENSO and the atmospheric response to these anomalies, which is composed of both westerlies in the central Pacific and easterlies in the far western equatorial Pacific. It is found that there is little net change in the zonal mean wind stress at the equator, suggesting that the westerlies cancel the impact of the easterlies on the basin-scale tilt of the equatorial zonal mean thermocline depth. The anomalous westerly winds in the central equatorial Pacific are found to increase the amplitude of an El Niño event directly by increasing anomalous warm zonal advection and reducing upwelling. Moreover, the off-equatorial anticyclonic wind stress associated with the cold SST anomalies during the warm phase of ENSO tends to reduce the discharge of the equatorial heat content. Thus, the coupled processes over the western Pacific warm pool can serve as a positive feedback to amplify ENSO cycles.

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