Comparative study of the Pacific ENSO event of 1991-92 and the Atlantic ENSO-like event of 1991

1994 ◽  
Vol 45 (4) ◽  
pp. 705 ◽  
Author(s):  
AB Polonsky
Keyword(s):  
High Amplitude ◽  
Enso Event ◽  
Equatorial Pacific ◽  
Trade Wind ◽  
South American ◽  
Equatorial Atlantic ◽  
Short Term ◽  
Boreal Spring ◽  
The Pacific ◽  
The Tropical Pacific

Anomalous conditions in the tropical Pacific and Atlantic Oceans during the ENSO event of 1991-92 are examined, using mainly the daily sea surface temperature (SST) data of the Russian Hydrometeorological Centre from April 1991 to December 1992. The event was characterized by some unusual features. It began in (boreal) spring 1991 as a weak event, then the SST anomalies (SSTAs) intensified and exceeded those in the ENSO of 1986-87. The 1991-92 event was manifested first in the enhanced average annual SST in the central and western parts of the equatorial Pacific. Significant persistent SSTAs near the South American coast were absent in 1991, occurring only at the beginning of 1992. The amplitude of the SST annual harmonic increased in the eastern and central equatorial Pacific. However, it decreased in the western equatorial Pacific during ENSO relaxation. High-amplitude and relatively short-term variability in the air-ocean system also occurred during the ENSO of 1991-92. The Pacific ENSO was accompanied by an Atlantic ENSO-like event, which also began in (boreal) spring 1991. It was manifested in the reduced intensity of the trade wind, the anomalously southern location of the intertropical convergence zone, and warm SSTAs in the eastern equatorial Atlantic. The mature SSTAs in the equatorial Pacific lagged behind those occurring in the equatorial Atlantic during the ENSO of 1991-92.

scholarly journals Mechanisms of Future Changes in Equatorial Upwelling: CMIP5 Intermodel Analysis

2020 ◽  
Vol 33 (2) ◽  
pp. 497-510 ◽  
Author(s):  
Mio Terada ◽  
Shoshiro Minobe ◽  
Curtis Deutsch
Keyword(s):  
Climate Models ◽  
Eastern Pacific ◽  
Trade Wind ◽  
Pacific Basin ◽  
Ekman Pumping ◽  
Equatorial Atlantic ◽  
Western Atlantic ◽  
Near Surface ◽  
The Pacific ◽  
Equatorial Upwelling

AbstractThe future change in equatorial upwelling between 1971–2000 and 2071–2100 is investigated using data from 24 coupled climate models. The multimodel ensemble (MME) mean exhibits substantial equatorial upwelling decrease in the eastern Pacific and weaker decrease in the western Atlantic Ocean. The MME mean of upwelling change and intermodel variation of that are decomposed into distinct isopycnal and diapycnal components. In the Pacific, the diapycnal upwelling decreases near the surface, associated with a weakened Ekman pumping. The isopycnal upwelling decreases at depths of 75–200 m around the core of the Equatorial Undercurrent (EUC) due to flattening of the density layer in which it flows. Both the weakened Ekman pumping and the EUC flattening are induced by the locally weakened trade wind over the eastern Pacific basin. In the equatorial Atlantic, both the change in MME mean and the intermodel variation of upwellings are significantly related to the weakened trade wind and enhanced stratification, although these drivers are not independent. The results for the Pacific Ocean imply that future reduction in upwelling may have impacts at different depths by different mechanisms. In particular, the rapid warming of sea surface temperature in the eastern Pacific basin may be mainly caused by the near-surface diapycnal upwelling reduction rather than isopycnal upwelling reduction associated EUC flattening, which is important at deeper levels.

Inter-basin interactions between the Pacific and Atlantic Oceans depending on the phase of Pacific decadal Oscillation and Atlantic multi-decadal oscillation

2021 ◽  
pp. 1-38
Keyword(s):  
Pacific Ocean ◽  
Atlantic Ocean ◽  
Pacific Decadal Oscillation ◽  
Walker Circulation ◽  
Equatorial Pacific ◽  
Equatorial Pacific Ocean ◽  
Equatorial Atlantic ◽  
The Pacific ◽  
Equatorial Atlantic Ocean ◽  
Relationship Of

Abstract The authors investigated the inter-basin interactions between the Pacific and Atlantic Oceans depending on the phase relationship of Pacific decadal oscillation (PDO)/Atlantic multi-decadal oscillation (AMO) based on observations and idealized model experiments. When the AMO and the PDO are in-phase (i.e., +PDO/+AMO or −PDO/-AMO), the Pacific Ocean regulates the SST anomalies in the equatorial Atlantic Ocean with altering a Walker circulation. During this period, there is a negative SST-precipitation relationship in the equatorial Atlantic Ocean where the atmosphere forces the ocean. In contrast, when they are out-of-phase (i.e., either +PDO/-AMO or −PDO/+AMO), the Atlantic Ocean influences the equatorial Pacific Ocean by modifying Walker circulation, resulting in a westward shift of a center of convective forcing in the equatorial Pacific Ocean compared to that during an inphase relationship of PDO/AMO. During this period, a positive SST-precipitation relationship is dominant in the equatorial Atlantic Ocean where the ocean forces the atmosphere. To verify this result, we conducted pacemaker experiments using the Nanjing University of Information Science and Technology Earth System Model version 3 (NESM3). Model results supported our findings obtained from the observations. We infer that the characteristics of the Pacific-Atlantic inter-basin interactions depend on whether the PDO and AMO phases are either in-phase or out of phase.

scholarly journals Linking the Pacific Meridional Mode to ENSO: Coupled Model Analysis

2009 ◽  
Vol 22 (12) ◽  
pp. 3488-3505 ◽  
Author(s):  
Li Zhang ◽  
Ping Chang ◽  
Link Ji
Keyword(s):  
Southern Oscillation ◽  
Coupled Model ◽  
Enso Event ◽  
Boreal Spring ◽  
Enso Events ◽  
Maximum Variance ◽  
Surface Circulation ◽  
The Pacific ◽  
Anomalous Surface ◽  
Thermodynamic Coupling

Abstract The occurrence of a boreal spring phenomenon referred to as the Pacific meridional model (MM) is shown to be intimately linked to the development of El Niño–Southern Oscillation (ENSO) in a long simulation of a coupled model. The MM, characterized by an anomalous north–south SST gradient and anomalous surface circulation in the northeasterly trade regime with maximum variance in boreal spring, is shown to be inherent to thermodynamic ocean–atmosphere coupling in the intertropical convergence zone (ITCZ) latitude, and the MM existence is independent of ENSO. The thermodynamic coupling enhances the persistence of the anomalous winds in the deep tropics, forcing energetic equatorially trapped oceanic waves to occur in the central western Pacific, which in turn initiate an ENSO event. The majority of ENSO events in both nature and the coupled model are preceded by MM events.

scholarly journals A Stronger Versus Weaker Walker: Understanding Model Differences in Fast and Slow Tropical Pacific Responses to Global Warming

2021 ◽  
Author(s):  
Ulla K. Heede ◽  
Alexey V. Fedorov ◽  
Natalie J. Burls
Keyword(s):  
Radiative Forcing ◽  
Climate Models ◽  
Horizontal Resolution ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Trade Wind ◽  
Bjerknes Feedback ◽  
Eastern Equatorial Pacific ◽  
Walker Cell ◽  
The Tropical Pacific

Abstract The tropical Pacific response to radiative forcing remains uncertain as projected future changes to the Walker circulation and SST patterns vary substantially among climate models. Here, we study what sets the magnitude and timescales of the response and why they differ across models. Specifically, we compare the fast and slow responses of the tropical Pacific to abrupt CO2 increases (2,4,8,16xCO2) in two configurations of the same model family (CESM) that differ in horizontal resolution and mean biases. We find that the model with a higher resolution shows a transient ocean thermostat-like response to CO2-forcing, with a stronger Walker cell and lack of warming in the eastern Pacific trade wind belts. This fast response lasts for about 50 years and is followed by a slight Walker cell weakening and equatorial warming. The second model, with a coarser resolution, shows a weak and short-lasting ocean thermostat response, followed by pronounced Walker cell weakening and eastern equatorial Pacific warming, similar to the long-term pattern noted in previous studies. These fast and slow responses also manifest in gradual CO2 increase experiments. We relate the magnitude of the fast ocean-thermostat response to the structure of the equatorial thermocline, setting the strength of the Bjerknes feedback. The magnitude and timing of the eastern equatorial Pacific warming are, is turn, related to the competition of the wind-evaporation-SST feedback amplifying the ocean-thermostat against the slowdown of oceanic subtropical cells and extra-tropical warming eroding the thermostat. Different balances between these effects could explain the large spread in the future projections for the tropical Pacific.

Chemical and hydrographic measurements from the Equatorial Pacific during boreal spring 1992

1992 ◽  
Author(s):  
M.F. LAMB, ◽  
J.C. HENDEE, ◽  
R. WANNINKHOF, ◽  
R.A. FEELY, ◽  
F.J. MILLERO, ◽  
...  
Keyword(s):  
Equatorial Pacific ◽  
Boreal Spring

Growing Coconut Palms in the Pacific Islands: Colliding Knowledge and Values

2020 ◽  
Author(s):  
Judith A. Bennett
Keyword(s):  
Pacific Islands ◽  
Social Values ◽  
Coconut Oil ◽  
Tropical Pacific ◽  
Experiential Knowledge ◽  
The West ◽  
Passive Resistance ◽  
The People ◽  
The Pacific ◽  
The Tropical Pacific

Coconuts provided commodities for the West in the form of coconut oil and copra. Once colonial governments established control of the tropical Pacific Islands, they needed revenue so urged European settlers to establish coconut plantations. For some decades most copra came from Indigenous growers. Administrations constantly urged the people to thin old groves and plant new ones like plantations, in grid patterns, regularly spaced and weeded. Local growers were instructed to collect all fallen coconuts for copra from their groves. For half a century, the administrations’ requirements met with Indigenous passive resistance. This paper examines the underlying reasons for this, elucidating Indigenous ecological and social values, based on experiential knowledge, knowledge that clashed with Western scientific values.

scholarly journals Subway Gearbox Fault Diagnosis Algorithm Based on Adaptive Spline Impact Suppression

Entropy ◽  
2021 ◽  
Vol 23 (6) ◽  
pp. 660
Author(s):  
Zhongshuo Hu ◽  
Jianwei Yang ◽  
Dechen Yao ◽  
Jinhai Wang ◽  
Yongliang Bai
Keyword(s):  
Fault Diagnosis ◽  
Spline Interpolation ◽  
Reference Value ◽  
High Amplitude ◽  
Engineering Practice ◽  
Negative Effects ◽  
Short Term ◽  
Time Domain Signal ◽  
Gearbox Vibration ◽  
Long Time

In the signal processing of real subway vehicles, impacts between wheelsets and rail joint gaps have significant negative effects on the spectrum. This introduces great difficulties for the fault diagnosis of gearboxes. To solve this problem, this paper proposes an adaptive time-domain signal segmentation method that envelopes the original signal using a cubic spline interpolation. The peak values of the rail joint gap impacts are extracted to realize the adaptive segmentation of gearbox fault signals when the vehicle was moving at a uniform speed. A long-time and unsteady signal affected by wheel–rail impacts is segmented into multiple short-term, steady-state signals, which can suppress the high amplitude of the shock response signal. Finally, on this basis, multiple short-term sample signals are analyzed by time- and frequency-domain analyses and compared with the nonfaulty results. The results showed that the method can efficiently suppress the high-amplitude components of subway gearbox vibration signals and effectively extract the characteristics of weak faults due to uniform wear of the gearbox in the time and frequency domains. This provides reference value for the gearbox fault diagnosis in engineering practice.

scholarly journals Genetic diversity and kinship relationships in one of the largest South American fur seal ( Arctocephalus australis ) populations of the Pacific Ocean

2021 ◽  
Author(s):  
Josefina Gutiérrez ◽  
Mauricio Seguel ◽  
Pablo Saenz‐Agudelo ◽  
Gerardo Acosta‐Jamett ◽  
Claudio Verdugo
Keyword(s):  
Genetic Diversity ◽  
Pacific Ocean ◽  
South American ◽  
The Pacific ◽  
Fur Seal ◽  
The Pacific Ocean

scholarly journals Sources of Tropical Subseasonal Skill in the CFSv2

2020 ◽  
Vol 148 (4) ◽  
pp. 1553-1565 ◽  
Author(s):  
Carl J. Schreck ◽  
Matthew A. Janiga ◽  
Stephen Baxter
Keyword(s):  
Indian Ocean ◽  
Low Frequency ◽  
Equatorial Pacific ◽  
Convectively Coupled Equatorial Waves ◽  
Subseasonal Variability ◽  
The Pacific ◽  
Fourier Filtering ◽  
The Indian Ocean ◽  
Rainfall Anomalies ◽  
Combined Data

Abstract This study applies Fourier filtering to a combination of rainfall estimates from TRMM and forecasts from the CFSv2. The combined data are filtered for low-frequency (LF, ≥120 days) variability, the MJO, and convectively coupled equatorial waves. The filtering provides insight into the sources of skill for the CFSv2. The LF filter, which encapsulates persistent anomalies generally corresponding with SSTs, has the largest contribution to forecast skill beyond week 2. Variability within the equatorial Pacific is dominated by its response to ENSO, such that both the unfiltered and the LF-filtered forecasts are skillful over the Pacific through the entire 45-day CFSv2 forecast. In fact, the LF forecasts in that region are more skillful than the unfiltered forecasts or any combination of the filters. Verifying filtered against unfiltered observations shows that subseasonal variability has very little opportunity to contribute to skill over the equatorial Pacific. Any subseasonal variability produced by the model is actually detracting from the skill there. The MJO primarily contributes to CFSv2 skill over the Indian Ocean, particularly during March–May and MJO phases 2–5. However, the model misses opportunities for the MJO to contribute to skill in other regions. Convectively coupled equatorial Rossby waves contribute to skill over the Indian Ocean during December–February and the Atlantic Ocean during September–November. Convectively coupled Kelvin waves show limited potential skill for predicting weekly averaged rainfall anomalies since they explain a relatively small percent of the observed variability.

Ocean Response to Wind Variations, Warm Water Volume, and Simple Models of ENSO in the Low-Frequency Approximation

2010 ◽  
Vol 23 (14) ◽  
pp. 3855-3873 ◽  
Author(s):  
Alexey V. Fedorov
Keyword(s):  
Low Frequency ◽  
Equatorial Pacific ◽  
Warm Water ◽  
Water Volume ◽  
Thermocline Depth ◽  
Phase Lag ◽  
Eastern Equatorial Pacific ◽  
The Pacific ◽  
Warm Water Volume ◽  
Frequency Approximation

Abstract Physical processes that control ENSO are relatively fast. For instance, it takes only several months for a Kelvin wave to cross the Pacific basin (Tk ≈ 2 months), while Rossby waves travel the same distance in about half a year. Compared to such short time scales, the typical periodicity of El Niño is much longer (T ≈ 2–7 yr). Thus, ENSO is fundamentally a low-frequency phenomenon in the context of these faster processes. Here, the author takes advantage of this fact and uses the smallness of the ratio ɛk = Tk/T to expand solutions of the ocean shallow-water equations into power series (the actual parameter of expansion also includes the oceanic damping rate). Using such an expansion, referred to here as the low-frequency approximation, the author relates thermocline depth anomalies to temperature variations in the eastern equatorial Pacific via an explicit integral operator. This allows a simplified formulation of ENSO dynamics based on an integro-differential equation. Within this formulation, the author shows how the interplay between wind stress curl and oceanic damping rates affects 1) the amplitude and periodicity of El Niño and 2) the phase lag between variations in the equatorial warm water volume and SST in the eastern Pacific. A simple analytical expression is derived for the phase lag. Further, applying the low-frequency approximation to the observed variations in SST, the author computes thermocline depth anomalies in the western and eastern equatorial Pacific to show a good agreement with the observed variations in warm water volume. Ultimately, this approach provides a rigorous framework for deriving other simple models of ENSO (the delayed and recharge oscillators), highlights the limitations of such models, and can be easily used for decadal climate variability in the Pacific.

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