scholarly journals Tropical Pacific Surface Wind Energy Spectra and Coherence: Basinwide Observations and Their Observing System Implications

2020 ◽  
Vol 33 (16) ◽  
pp. 7141-7154
Author(s):  
Andrew M. Chiodi ◽  
D. E. Harrison
Keyword(s):  
Surface Wind ◽  
Tropical Pacific ◽  
Central Pacific ◽  
Eastern Equatorial Pacific ◽  
Term Change ◽  
Decadal Scale ◽  
Optimal Spacing ◽  
Minimal Redundancy ◽  
Original Array ◽  
The Tropical Pacific

AbstractThe tropical Pacific moored-buoy array spacing was based on wind coherence scales observed from low-lying islands in the western-central tropical Pacific. Since the array was deployed across the full basin in the mid-1990s, winds from the array have proven critical to accurately monitoring for decadal-scale changes in tropical Pacific winds and identifying spurious trends in wind analysis products used to monitor for long-term change. The array observations have also greatly advanced our ability to diagnostically model (hindcast) and thereby better understand the observed development of central Pacific sea surface temperature anomaly development associated with El Niño and La Niña events, although the eastern equatorial Pacific is not yet accurately hindcast. The original array-design assumptions that the statistics calculated from the western-central Pacific island records are representative of open-ocean conditions and other regions of the tropical Pacific have not been thoroughly reexamined. We revisit these assumptions using the basinwide wind observations provided by the array and find that key wind statistics change across the tropical Pacific basin in ways that could not be determined from the original island wind study. The island results provided a best-case answer for mooring zonal spacing with minimally redundant coherence between adjacent buoys. Buoy-observed meridional coherence scales are longer than determined from the islands. Enhanced zonal sampling east of 140°W and west of 180° is needed to obtain minimal redundancy (optimal spacing). Reduced meridional sampling could still yield minimal redundancy for wind and wind stress fields over the ocean waveguide.

scholarly journals Response of ENSO and the Mean State of the Tropical Pacific to Extratropical Cooling and Warming: A Study Using the IAP Coupled Model

2009 ◽  
Vol 22 (22) ◽  
pp. 5902-5917 ◽  
Author(s):  
Y. Yu ◽  
D-Z. Sun
Keyword(s):  
Climate Change ◽  
Climate Modeling ◽  
Coupled Model ◽  
Tropical Pacific ◽  
Equatorial Region ◽  
Upper Ocean ◽  
Central Pacific ◽  
Intergovernmental Panel ◽  
Ocean Atmosphere ◽  
The Tropical Pacific

Abstract The coupled model of the Institute of Atmospheric Physics (IAP) is used to investigate the effects of extratropical cooling and warming on the tropical Pacific climate. The IAP coupled model is a fully coupled GCM without any flux correction. The model has been used in many aspects of climate modeling, including the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) climate change and paleoclimate simulations. In this study, the IAP coupled model is subjected to cooling or heating over the extratropical Pacific. As in an earlier study, the cooling and heating is imposed over the extratropical region poleward of 10°N–10°S. Consistent with earlier findings, an elevated (reduced) level of ENSO activity in response to an increase (decrease) in the cooling over the extratropical region is found. The changes in the time-mean structure of the equatorial upper ocean are also found to be very different between the case in which ocean–atmosphere is coupled over the equatorial region and the case in which the ocean–atmosphere over the equatorial region is decoupled. For example, in the uncoupled run, the thermocline water across the entire equatorial Pacific is cooled in response to an increase in the extratropical cooling. In the corresponding coupled run, the changes in the equatorial upper-ocean temperature in the extratropical cooling resemble a La Niña situation—a deeper thermocline in the western and central Pacific accompanied by a shallower thermocline in the eastern Pacific. Conversely, with coupling, the response of the equatorial upper ocean to extratropical cooling resembles an El Niño situation. These results ascertain the role of extratropical ocean in determining the amplitude of ENSO. The results also underscore the importance of ocean–atmosphere coupling in the interaction between the tropical Pacific and the extratropical Pacific.

scholarly journals Sea surface chlorophyll signature in the tropical Pacific during eastern and central Pacific ENSO events

2012 ◽  
Vol 117 (C4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Marie-Hélène Radenac ◽  
Fabien Léger ◽  
Awnesh Singh ◽  
Thierry Delcroix
Keyword(s):  
Tropical Pacific ◽  
Sea Surface ◽  
Central Pacific ◽  
Enso Events ◽  
Central Pacific Enso ◽  
The Tropical Pacific

scholarly journals A review of ENSO theories

2018 ◽  
Vol 5 (6) ◽  
pp. 813-825 ◽  
Author(s):  
Chunzai Wang
Keyword(s):  
El Niño ◽  
El Nino ◽  
Enso Event ◽  
Tropical Pacific ◽  
Kelvin Waves ◽  
Western Pacific ◽  
Central Pacific ◽  
Central Pacific El Niño ◽  
Negative Feedbacks ◽  
The Tropical Pacific

Abstract The El Niño and the Southern Oscillation (ENSO) occurrence can be usually explained by two views of (i) a self-sustained oscillatory mode and (ii) a stable mode interacting with high-frequency forcing such as westerly wind bursts and Madden-Julian Oscillation events. The positive ocean–atmosphere feedback in the tropical Pacific hypothesized by Bjerknes leads the ENSO event to a mature phase. After ENSO event matures, negative feedbacks are needed to cease the ENSO anomaly growth. Four negative feedbacks have been proposed: (i) reflected Kelvin waves at the ocean western boundary, (ii) a discharge process due to Sverdrup transport, (iii) western-Pacific wind-forced Kelvin waves and (iv) anomalous zonal advections and wave reflection at the ocean eastern boundary. These four ENSO mechanisms are respectively called the delayed oscillator, the recharge–discharge oscillator, the western-Pacific oscillator and the advective–reflective oscillator. The unified oscillator is developed by including all ENSO mechanisms, i.e. all four ENSO oscillators are special cases of the unified oscillator. The tropical Pacific Ocean and atmosphere interaction can also induce coupled slow westward- and eastward-propagating modes. An advantage of the coupled slow modes is that they can be used to explain the propagating property of interannual anomalies, whereas the oscillatory modes produce a standing oscillation. The research community has recently paid attention to different types of ENSO events by focusing on the central-Pacific El Niño. All of the ENSO mechanisms may work for the central-Pacific El Niño events, with an addition that the central-Pacific El Niño may be related to forcing or processes in the extra-tropical Pacific.

scholarly journals Cloud–Radiation Feedback as a Leading Source of Uncertainty in the Tropical Pacific SST Warming Pattern in CMIP5 Models

2016 ◽  
Vol 29 (10) ◽  
pp. 3867-3881 ◽  
Author(s):  
Jun Ying ◽  
Ping Huang
Keyword(s):  
Heat Budget ◽  
Tropical Pacific ◽  
Eastern Pacific ◽  
Shortwave Radiation ◽  
Cmip5 Models ◽  
Central Pacific ◽  
Surface Warming ◽  
Sst Warming ◽  
Radiation Feedback ◽  
The Tropical Pacific

Abstract The role of the intermodel spread of cloud–radiation feedback in the uncertainty in the tropical Pacific SST warming (TPSW) pattern under global warming is investigated based on the historical and RCP8.5 runs from 32 models participating in CMIP5. The large intermodel discrepancies in cloud–radiation feedback contribute 24% of the intermodel uncertainty in the TPSW pattern over the central Pacific. The mechanism by which the cloud–radiation feedback influences the TPSW pattern is revealed based on an analysis of the surface heat budget. A relatively weak negative cloud–radiation feedback over the central Pacific cannot suppress the surface warming as greatly as in the multimodel ensemble and thus induces a warm SST deviation over the central Pacific, producing a low-level convergence that suppresses (enhances) the evaporative cooling and zonal cold advection in the western (eastern) Pacific. With these processes, the original positive SST deviation over the central Pacific will move westward to the western and central Pacific, with a negative SST deviation in the eastern Pacific. Compared with the observed cloud–radiation feedback from six sets of reanalysis and satellite-observed data, the negative cloud–radiation feedback in the models is underestimated in general. It implies that the TPSW pattern should be closer to an El Niño–like pattern based on the concept of observational constraint. However, the observed cloud–radiation feedback from the various datasets also demonstrates large discrepancies in magnitude. Therefore, the authors suggest that more effort should be made to improve the precision of shortwave radiation observations and the description of cloud–radiation feedback in models for a more reliable projection of the TPSW pattern in future.

scholarly journals The Pacific Ocean heat engine

2021 ◽  
Author(s):  
Roger N. Jones ◽  
James H. Ricketts
Keyword(s):  
Steady State ◽  
Pacific Ocean ◽  
Heat Engine ◽  
Stable State ◽  
Warm Pool ◽  
Tropical Pacific ◽  
Phase Changes ◽  
Central Pacific ◽  
Abrupt Shifts ◽  
The Tropical Pacific

Abstract. Historical warming forms a sequence of steady-state regimes punctuated by abrupt shifts. These changes are regulated by a heat engine spanning the tropical Pacific Ocean teleconnected to a broader climate network. The eastern-central Pacific maintains steady-state conditions, delivering heat to the Western Pacific warm pool. They form a heat pump with heat moving from the cold to the warm reservoir, sustained by kinetic energy. The two reservoirs exchange heat on a range of timescales, with oscillatory behaviour that intensifies under forcing. The heat engine is part of a network of oscillations and circulation interacting on a range of timescales. The process is self-regulating: steady-state regimes persist until they become unstable due to an over- or under-supply of heat for dissipation, shifting warmer or cooler to a new stable state. Pre-industrial climate was in free mode, characterised by a loosely-coupled ocean-atmosphere with limited circulation, moving into forced mode in the latter 20th century, characterised by tighter coupling and stronger circulation through the tropical Pacific with more active teleconnections globally. Continued forcing produces a stepladder-like pattern of warming. Most shifts coincide with phase changes in decadal oscillations, switching from slower to faster modes of dissipation. El Niño events combine with regime shifts to propagate heat from the oceans to land and from the tropics to higher latitudes. The most recent shift commenced in the warm pool in December 2012, ending the so-called hiatus (1997–2013), global mean surface temperatures warming abruptly by ~0.25 °C in 2014–15.

scholarly journals Impact of westerly wind burst on El Niño-sourthern oscillation

2020 ◽  
Author(s):  
◽  
Mohammad Alam
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Coupled Model ◽  
Vital Role ◽  
Tropical Pacific ◽  
Westerly Wind ◽  
Central Pacific ◽  
Enso Events ◽  
The Tropical Pacific

Westerly wind bursts (WWBs), usually occurring in the tropical Pacific region, play a vital role in El Niño–Southern Oscillation (ENSO). In this study, we use a hybrid coupled model (HCM) for the tropical Pacific Ocean-atmosphere system to investigate WWBs impact on ENSO. To achieve this goal, two experiments are performed: (a) first, the standard version of the HCM is integrated for years without prescribed WWBs events; and (b) second, the WWBs are added into the HCM (HCM-WWBs). Results show that HCM-WWBs can generate not only more realistic climatology of sea surface temperature (SST) in both spatial structure and temporal amplitudes, but also better ENSO features, than the HCM. In particular, the HCM-WWBs can capture the central Pacific (CP) ENSO events, which is absent in original HCM. Furthermore, the possible physical mechanisms responsible for these improvements by WWBs are discussed.

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