scholarly journals Examination of the Two Types of ENSO in the NCEP CFS Model and Its Extratropical Associations

2012 ◽  
Vol 140 (6) ◽  
pp. 1908-1923 ◽  
Author(s):  
Seon Tae Kim ◽  
Jin-Yi Yu ◽  
Arun Kumar ◽  
Hui Wang
Keyword(s):  
Southern Oscillation ◽  
Stability Index ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Stratus Clouds ◽  
The North ◽  
Sst Variability ◽  
Marine Stratus ◽  
Extratropical Forcing ◽  
Environmental Prediction

Abstract Two types of El Niño–Southern Oscillation (ENSO) simulated by the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFS) model are examined. The model is found to produce both the eastern Pacific (EP) and central Pacific (CP) types of ENSO with spatial patterns and temporal evolutions similar to the observed. The simulated ENSO intensity is comparable to the observed for the EP type, but weaker than the observed for the CP type. Further analyses reveal that the generation of the simulated CP ENSO is linked to extratropical forcing associated with the North Pacific Oscillation (NPO) and that the model is capable of simulating the coupled air–sea processes in the subtropical Pacific that slowly spreads the NPO-induced SST variability into the tropics, as shown in the observations. The simulated NPO, however, does not extend as far into the deep tropics as it does in the observations and the coupling in the model is not sustained as long as it is in the observations. As a result, the extratropical forcing of tropical central Pacific SST variability in the CFS model is weaker than in the observations. An additional analysis with the Bjerknes stability index indicates that the weaker CP ENSO in the CFS model is also partially due to unrealistically weak zonal advective feedback in the equatorial Pacific. These model deficiencies appear to be related to an underestimation in the amount of the marine stratus clouds off the North American coasts inducing an ocean surface warm bias in the eastern Pacific. This study suggests that a realistic simulation of these marine stratus clouds can be important for the CP ENSO simulation.

scholarly journals Ocean Processes Affecting the Twenty-First-Century Shift in ENSO SST Variability

2016 ◽  
Vol 29 (19) ◽  
pp. 6861-6879 ◽  
Author(s):  
Cong Guan ◽  
Michael J. McPhaden
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
First Century ◽  
Eastern Pacific ◽  
Enso Cycle ◽  
Central Pacific ◽  
Temperature Variance ◽  
Sst Variability ◽  
Twenty First Century

Abstract Sea surface temperature (SST) variability associated with El Niño–Southern Oscillation (ENSO) slightly increased in the central Pacific Ocean but weakened significantly in the eastern Pacific at the beginning of twenty-first century relative to 1980–99. This decadal shift led to the greater prominence central Pacific (CP) El Niño events during the 2000s relative to the previous two decades, which were dominated by eastern Pacific (EP) events. To expand upon previous studies that have examined this shift in ENSO variability, temperature and temperature variance budgets are examined in the mixed layer of the Niño-3 (5°S–5°N, 150°–90°W) and Niño-4 (5°S–5°N, 160°E–150°W) regions from seven ocean model products spanning the period 1980–2010. This multimodel-product-based approach provides a robust assessment of dominant mechanisms that account for decadal changes in two key index regions. A temperature variance budget perspective on the role of thermocline feedbacks in the ENSO cycle based on recharge oscillator theory is also presented. As found in previous studies, thermocline and zonal advective feedbacks are the most important positive feedbacks for generating ENSO SST variance, and thermodynamic damping is the largest negative feedback for damping ENSO variance. Consistent with the shift toward more CP El Niños after 2000, thermocline feedbacks experienced a substantial reduction from 1980 to 1999 and into the 2000s, while zonal advective feedbacks were less affected. Negative feedbacks likewise weakened after 2000, particularly thermal damping in the Niño-3 region and the nonlinear sink of variance in both regions.

scholarly journals Spurious North Tropical Atlantic precursors to El Niño

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wenjun Zhang ◽  
Feng Jiang ◽  
Malte F. Stuecker ◽  
Fei-Fei Jin ◽  
Axel Timmermann
Keyword(s):  
El Niño ◽  
Cross Correlation ◽  
El Nino ◽  
Southern Oscillation ◽  
Global Climate ◽  
Tropical Atlantic ◽  
The North ◽  
Sst Variability ◽  
Primary Driver ◽  
North Tropical Atlantic

AbstractThe El Niño-Southern Oscillation (ENSO), the primary driver of year-to-year global climate variability, is known to influence the North Tropical Atlantic (NTA) sea surface temperature (SST), especially during boreal spring season. Focusing on statistical lead-lag relationships, previous studies have proposed that interannual NTA SST variability can also feed back on ENSO in a predictable manner. However, these studies did not properly account for ENSO’s autocorrelation and the fact that the SST in the Atlantic and Pacific, as well as their interaction are seasonally modulated. This can lead to misinterpretations of causality and the spurious identification of Atlantic precursors for ENSO. Revisiting this issue under consideration of seasonality, time-varying ENSO frequency, and greenhouse warming, we demonstrate that the cross-correlation characteristics between NTA SST and ENSO, are consistent with a one-way Pacific to Atlantic forcing, even though the interpretation of lead-lag relationships may suggest otherwise.

The relationship between the El Niño Southern Oscillation and Australian monsoon rainfall on decadal time-scales

2021 ◽  
Author(s):  
Hanna Heidemann ◽  
Joachim Ribbe ◽  
Benjamin J. Henley ◽  
Tim Cowan ◽  
Christa Pudmenzky ◽  
...  
Keyword(s):  
Monsoon Rainfall ◽  
Decadal Variability ◽  
Southern Oscillation ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Australian Monsoon ◽  
Enso Events ◽  
Pacific Decadal Variability ◽  
Prediction Systems ◽  
Different Response

<p>This research analyses the observed relationship between eastern and central Pacific El Niño Southern Oscillation (ENSO) events and Australian monsoon rainfall (AUMR) on a decadal timescale during the December to March monsoon months. To assess the decadal influence of the different flavours of ENSO on the AUMR, we focus on the phases of the Interdecadal Pacific Oscillation (IPO) over the period 1920 to 2020.  The AUMR is characterized by substantial decadal variability, which appears to be linked to the positive and negative phases of the IPO. During the past two historical negative IPO phases, significant correlations have been observed between central Pacific sea surface temperature (SST) anomalies and AUMR over both the northeast and northwest of Australia. This central Pacific SST-AUMR relationship has strengthened from the first negative IPO phase (mid-1940s to the mid-1970s) to the second (late 1990s to mid-2010s), while the eastern Pacific SST-AUMR influence has weakened. Composite rainfall anomalies over Australia reveal a different response of AUMR to central Pacific El Niño/La Niña and eastern Pacific La Niña events during positive IPO and negative IPO phases. This research clearly shows that ENSO's influence on AUMR is modulated by Pacific decadal variability, however this teleconnection, in itself, can change between similar decadal Pacific states.  Going forward, as decadal prediction systems improve and become more mainstream, the IPO phase could be used as a potential source for decadal predictability of the tendency of AUMR.  </p>

North-Central Pacific Tropical Cyclones: Impacts of El Niño–Southern Oscillation and the Madden–Julian Oscillation

2013 ◽  
Vol 26 (19) ◽  
pp. 7720-7733 ◽  
Author(s):  
Philip J. Klotzbach ◽  
Eric S. Blake
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Rapid Intensification ◽  
Madden Julian Oscillation ◽  
Cyclone Activity ◽  
Central Pacific ◽  
North Central ◽  
The North

Abstract Both El Niño–Southern Oscillation (ENSO) and the Madden–Julian oscillation (MJO) have been documented in previous research to impact tropical cyclone (TC) activity around the globe. This study examines the relationship of each mode individually along with a combined index on tropical cyclone activity in the north-central Pacific. Approximately twice as many tropical cyclones form in the north-central Pacific in El Niño years compared with La Niña years. These differences are attributed to a variety of factors, including warmer sea surface temperatures, lower sea level pressures, increased midlevel moisture, and anomalous midlevel ascent in El Niño years. When the convectively enhanced phase of the MJO is located over the eastern and central tropical Pacific, the north-central Pacific tends to have more tropical cyclone activity, likely because of reduced vertical wind shear, lower sea level pressures, and increased vertical motion. The convectively enhanced phase of the MJO is also responsible for most of the TCs that undergo rapid intensification in the north-central Pacific. A combined MJO–ENSO index that is primarily associated with anomalous rising motion over the tropical eastern Pacific has an even stronger relationship with north-central Pacific TCs, as well as rapid intensification, than either individually.

scholarly journals Contrasting Eastern-Pacific and Central-Pacific Types of ENSO

2009 ◽  
Vol 22 (3) ◽  
pp. 615-632 ◽  
Author(s):  
Hsun-Ying Kao ◽  
Jin-Yi Yu
Keyword(s):  
Indian Ocean ◽  
Southern Oscillation ◽  
Surface Wind ◽  
Tropical Indian Ocean ◽  
Eastern Pacific ◽  
Structure Evolution ◽  
Interdecadal Change ◽  
Central Pacific ◽  
Enso Events ◽  
Dominant Period

Abstract Surface observations and subsurface ocean assimilation datasets are examined to contrast two distinct types of El Niño–Southern Oscillation (ENSO) in the tropical Pacific: an eastern-Pacific (EP) type and a central-Pacific (CP) type. An analysis method combining empirical orthogonal function (EOF) analysis and linear regression is used to separate these two types. Correlation and composite analyses based on the principal components of the EOF were performed to examine the structure, evolution, and teleconnection of these two ENSO types. The EP type of ENSO is found to have its SST anomaly center located in the eastern equatorial Pacific attached to the coast of South America. This type of ENSO is associated with basinwide thermocline and surface wind variations and shows a strong teleconnection with the tropical Indian Ocean. In contrast, the CP type of ENSO has most of its surface wind, SST, and subsurface anomalies confined in the central Pacific and tends to onset, develop, and decay in situ. This type of ENSO appears less related to the thermocline variations and may be influenced more by atmospheric forcing. It has a stronger teleconnection with the southern Indian Ocean. Phase-reversal signatures can be identified in the anomaly evolutions of the EP-ENSO but not for the CP-ENSO. This implies that the CP-ENSO may occur more as events or epochs than as a cycle. The EP-ENSO has experienced a stronger interdecadal change with the dominant period of its SST anomalies shifted from 2 to 4 yr near 1976/77, while the dominant period for the CP-ENSO stayed near the 2-yr band. The different onset times of these two types of ENSO imply that the difference between the EP and CP types of ENSO could be caused by the timing of the mechanisms that trigger the ENSO events.

scholarly journals Connectivity between Historical Great Basin Precipitation and Pacific Ocean Variability: A CMIP5 Model Evaluation

2015 ◽  
Vol 28 (15) ◽  
pp. 6096-6112 ◽  
Author(s):  
Kimberly Smith ◽  
Courtenay Strong ◽  
Shih-Yu Wang
Keyword(s):  
Pacific Ocean ◽  
Time Scales ◽  
Great Basin ◽  
Southern Oscillation ◽  
Salt Lake ◽  
Coupled Model ◽  
The North ◽  
Sst Variability ◽  
The Pacific ◽  
Cmip5 Model Evaluation

Abstract The eastern Great Basin (GB) in the western United States is strongly affected by droughts that influence water management decisions. Precipitation that falls in the GB, particularly in the Great Salt Lake (GSL) basin encompassed by the GB, provides water for millions of people living along the Wasatch Front Range. Western U.S. precipitation is known to be influenced by El Niño–Southern Oscillation (ENSO) as well as the Pacific decadal oscillation (PDO) in the North Pacific. Historical connectivity between GB precipitation and Pacific Ocean sea surface temperatures (SSTs) on interannual to multidecadal time scales is evaluated for 20 models that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5). While the majority of the models had realistic ENSO and PDO spatial patterns in the SSTs, the simulated influence of these two modes on GB precipitation tended to be too strong for ENSO and too weak for PDO. Few models captured the connectivity at a quasi-decadal period influenced by the transition phase of the Pacific quasi-decadal oscillation (QDO; a recently identified climate mode that influences GB precipitation). Some of the discrepancies appear to stem from models not capturing the observed tendency for the PDO to modulate the sign of the ENSO–GB precipitation teleconnection. Of all of the models, CCSM4 most consistently captured observed connections between Pacific SST variability and GB precipitation on the examined time scales.

scholarly journals Diversity of the Madden–Julian Oscillation: Initiation Region Modulated by the Interaction between the Intraseasonal and Interannual Variabilities

2021 ◽  
Vol 34 (6) ◽  
pp. 2297-2318
Author(s):  
Daisuke Takasuka ◽  
Masaki Satoh
Keyword(s):  
El Niño ◽  
El Nino ◽  
Eastern Pacific ◽  
Boreal Winter ◽  
Madden Julian Oscillation ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Sst Variability ◽  
Circulation Patterns ◽  
The Difference

AbstractAs one of the aspects of the diversity of the Madden–Julian oscillation (MJO), the modulation of initiation regions of the boreal-winter MJO is studied in terms of the relationship between intraseasonal and interannual variabilities. MJOs are categorized as those initiating in the Indian Ocean (IO), Maritime Continent (MC), and western Pacific (WP), referred to herein as IO-MJOs, MC-MJOs, and WP-MJOs, respectively. The composite analyses for each MJO category using observational data reveal that the diversity of MJO initiation regions directly results from the modulation of areas where horizontal advective premoistening efficiently occurs via intraseasonal/synoptic-scale winds. This is supported by the difference in the zonal location of equatorial intraseasonal circulations established before MJO initiation, which is related to a spatial change in background convection and associated Walker circulations forced by interannual sea surface temperature (SST) variability. Compared to IO-MJOs (favored in the climatological background on average), MC-MJOs tend to be realized under the eastern-Pacific El Niño–like condition, as a result of eastward-shifted intraseasonal convection and circulation patterns induced by background suppressed convection in the eastern MC. WP-MJOs are frequently initiated under the central-Pacific El Niño–like and positive IO dipole–like conditions, in which the WP is selectively moistened with the aid of background enhanced (suppressed) convection over the WP (the southeastern IO and the central-to-eastern Pacific). This major tendency derived from sample-limited observations is verified by a set of 15-yr numerical experiments with a global nonhydrostatic MJO-permitting model under a perpetual boreal-winter condition where observation-based SSTs are prescribed.

scholarly journals Role of climate variability in the potential predictability of tropical cyclone formation in tropical and subtropical western North Pacific Ocean

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yu-Lin K. Chang ◽  
Yasumasa Miyazawa ◽  
Swadhin Behera
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Southern Oscillation ◽  
North Pacific Ocean ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Potential Predictability ◽  
Vorticity Anomaly ◽  
Tropical Western North Pacific

AbstractThe out of phase tropical cyclone (TC) formation in the subtropical and tropical western North Pacific associated with local low-level wind vorticity anomaly, driven by the remote central and eastern equatorial Pacific warming/cooling, is investigated based on the reanalysis and observational data in the period of 1979−2017. TC frequencies in the subtropical and tropical western North Pacific appear to be connected to different remote heating/cooling sources and are linked to eastern and central Pacific warming/cooling, which are in turn related to canonical El Niño/Southern Oscillation (ENSO) and ENSO Modoki, respectively. TCs formed in subtropics (SfTC) are generally found to be associated with a dipole in wind vorticity anomaly, which is driven by the tropical eastern Pacific warming/cooling. Tropically formed TCs (TfTC) are seen to be triggered by the single-core of wind vorticity anomaly locally associated with the warming/cooling of central and eastern Pacific. The predicted ENSOs and ENSO Modokis, therefore, provide a potential source of seasonal predictability for SfTC and TfTC frequencies.

scholarly journals Atmospheric torques and Earth's rotation: what drove the millisecond-level length-of-day response to the 2015–2016 El Niño?

2017 ◽  
Vol 8 (4) ◽  
pp. 1009-1017 ◽  
Author(s):  
Sébastien B. Lambert ◽  
Steven L. Marcus ◽  
Olivier de Viron
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Winter Season ◽  
Eastern Pacific ◽  
Earth’S Rotation ◽  
Length Of Day ◽  
Central Pacific ◽  
Earth's Rotation ◽  
Enso Events

Abstract. El Niño–Southern Oscillation (ENSO) events are classically associated with a significant increase in the length of day (LOD), with positive mountain torques arising from an east–west pressure dipole in the Pacific driving a rise of atmospheric angular momentum (AAM) and consequent slowing of the Earth's rotation. The large 1982–1983 event produced a lengthening of the day of about 0.9 ms, while a major ENSO event during the 2015–2016 winter season produced an LOD excursion reaching 0.81 ms in January 2016. By evaluating the anomaly in mountain and friction torques, we found that (i) as a mixed eastern–central Pacific event, the 2015–2016 mountain torque was smaller than for the 1982–1983 and 1997–1998 events, which were pure eastern Pacific events, and (ii) the smaller mountain torque was compensated for by positive friction torques arising from an enhanced Hadley-type circulation in the eastern Pacific, leading to similar AAM–LOD signatures for all three extreme ENSO events. The 2015–2016 event thus contradicts the existing paradigm that mountain torques cause the Earth rotation response for extreme El Niño events.

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