scholarly journals A Multimodel Ensemble Pattern Regression Method to Correct the Tropical Pacific SST Change Patterns under Global Warming

2015 ◽  
Vol 28 (12) ◽  
pp. 4706-4723 ◽  
Author(s):  
Ping Huang ◽  
Jun Ying
Keyword(s):  
Regional Climate ◽  
Walker Circulation ◽  
Regional Climate Change ◽  
Warm Pool ◽  
Tropical Pacific ◽  
Multimodel Ensemble ◽  
Epr Method ◽  
Circulation Change ◽  
The Common ◽  
The Tropical Pacific

Abstract This study develops a new observational constraint method, called multimodel ensemble pattern regression (EPR), to correct the projections of regional climate change by the conventional unweighted multimodel mean (MMM). The EPR method first extracts leading modes of historical bias using intermodel EOF analysis, then builds up the linear correlated modes between historical bias and change bias using multivariant linear regression, and finally estimates the common change bias induced by common historical bias. Along with correcting common change bias, the EPR method implicitly removes the intermodel uncertainty in the change projection deriving from the intermodel diversity in background simulation. The EPR method is applied to correct the patterns of tropical Pacific SST changes using the historical and representative concentration pathway 8.5 (RCP8.5) runs in 30 models from phase 5 of CMIP (CMIP5) and observed SSTs. The common bias patterns of the tropical Pacific SSTs in historical runs, including the excessive cold tongue, the southeastern warm bias, and the narrower warm pool, are estimated to induce La Niña–like change biases. After the estimated common change biases are removed, the corrected SST changes display a pronounced El Niño–like pattern and have much greater zonal gradients. The bias correction decreases by around half of the intermodel uncertainties in the MMM SST projections. The patterns of corrected tropical precipitation and circulation change are dominated by the enhanced SST change patterns, displaying a pronounced warmer-get-wetter pattern and a decreased Walker circulation with decreased uncertainties.

scholarly journals Changes in the Tropical Pacific SST Trend from CMIP3 to CMIP5 and Its Implication of ENSO

2012 ◽  
Vol 25 (21) ◽  
pp. 7764-7771 ◽  
Author(s):  
Sang-Wook Yeh ◽  
Yoo-Geun Ham ◽  
June-Yi Lee
Keyword(s):  
Coupled Model ◽  
Research Programme ◽  
Tropical Pacific ◽  
Multimodel Ensemble ◽  
Phase 3 ◽  
Intercomparison Project ◽  
Sst Anomaly ◽  
Earth System Models ◽  
Background State ◽  
The Tropical Pacific

This study assesses the changes in the tropical Pacific Ocean sea surface temperature (SST) trend and ENSO amplitude by comparing a historical run of the World Climate Research Programme Coupled Model Intercomparison Project (CMIP) phase-5 multimodel ensemble dataset (CMIP5) and the CMIP phase-3 dataset (CMIP3). The results indicate that the magnitude of the SST trend in the tropical Pacific basin has been significantly reduced from CMIP3 to CMIP5, which may be associated with the overestimation of the response to natural forcing and aerosols by including Earth system models in CMIP5. Moreover, the patterns of tropical warming over the second half of the twentieth century have changed from a La Niña–like structure in CMIP3 to an El Niño–like structure in CMIP5. Further analysis indicates that such changes in the background state of the tropical Pacific and an increase in the sensitivity of the atmospheric response to the SST changes in the eastern tropical Pacific have influenced the ENSO properties. In particular, the ratio of the SST anomaly variance in the eastern and western tropical Pacific increased from CMIP3 to CMIP5, indicating that a center of action associated with the ENSO amplitude has shifted to the east.

scholarly journals Impact of Resolution on the Tropical Pacific Circulation in a Matrix of Coupled Models

2009 ◽  
Vol 22 (10) ◽  
pp. 2541-2556 ◽  
Author(s):  
Malcolm J. Roberts ◽  
A. Clayton ◽  
M.-E. Demory ◽  
J. Donners ◽  
P. L. Vidale ◽  
...  
Keyword(s):  
Coupled Model ◽  
Walker Circulation ◽  
Ocean Model ◽  
Tropical Pacific ◽  
Coupled Models ◽  
Model Stability ◽  
The Mean ◽  
The Impact ◽  
Mean State ◽  
The Tropical Pacific

Abstract Results are presented from a matrix of coupled model integrations, using atmosphere resolutions of 135 and 90 km, and ocean resolutions of 1° and 1/3°, to study the impact of resolution on simulated climate. The mean state of the tropical Pacific is found to be improved in the models with a higher ocean resolution. Such an improved mean state arises from the development of tropical instability waves, which are poorly resolved at low resolution; these waves reduce the equatorial cold tongue bias. The improved ocean state also allows for a better simulation of the atmospheric Walker circulation. Several sensitivity studies have been performed to further understand the processes involved in the different component models. Significantly decreasing the horizontal momentum dissipation in the coupled model with the lower-resolution ocean has benefits for the mean tropical Pacific climate, but decreases model stability. Increasing the momentum dissipation in the coupled model with the higher-resolution ocean degrades the simulation toward that of the lower-resolution ocean. These results suggest that enhanced ocean model resolution can have important benefits for the climatology of both the atmosphere and ocean components of the coupled model, and that some of these benefits may be achievable at lower ocean resolution, if the model formulation allows.

Interannual Weakening of the Tropical Pacific Walker Circulation Due to Strong Tropical Volcanism

2018 ◽  
Vol 35 (6) ◽  
pp. 645-658 ◽  
Author(s):  
Jiapeng Miao ◽  
Tao Wang ◽  
Huijun Wang ◽  
Jianqi Sun
Keyword(s):  
Walker Circulation ◽  
Tropical Pacific ◽  
The Tropical Pacific

scholarly journals A CGCM Study on the Interaction between IOD and ENSO

2006 ◽  
Vol 19 (9) ◽  
pp. 1688-1705 ◽  
Author(s):  
Swadhin K. Behera ◽  
Jing Jia Luo ◽  
Sebastien Masson ◽  
Suryachandra A. Rao ◽  
Hirofumi Sakuma ◽  
...  
Keyword(s):  
Indian Ocean ◽  
General Circulation ◽  
Southern Oscillation ◽  
Walker Circulation ◽  
Tropical Pacific ◽  
Boreal Summer ◽  
Enso Variability ◽  
The Indian Ocean ◽  
Sst Anomalies ◽  
The Tropical Pacific

Abstract An atmosphere–ocean coupled general circulation model known as the Scale Interaction Experiment Frontier version 1 (SINTEX-F1) model is used to understand the intrinsic variability of the Indian Ocean dipole (IOD). In addition to a globally coupled control experiment, a Pacific decoupled noENSO experiment has been conducted. In the latter, the El Niño–Southern Oscillation (ENSO) variability is suppressed by decoupling the tropical Pacific Ocean from the atmosphere. The ocean–atmosphere conditions related to the IOD are realistically simulated by both experiments including the characteristic east–west dipole in SST anomalies. This demonstrates that the dipole mode in the Indian Ocean is mainly determined by intrinsic processes within the basin. In the EOF analysis of SST anomalies from the noENSO experiment, the IOD takes the dominant seat instead of the basinwide monopole mode. Even the coupled feedback among anomalies of upper-ocean heat content, SST, wind, and Walker circulation over the Indian Ocean is reproduced. As in the observation, IOD peaks in boreal fall for both model experiments. In the absence of ENSO variability the interannual IOD variability is dominantly biennial. The ENSO variability is found to affect the periodicity, strength, and formation processes of the IOD in years of co-occurrences. The amplitudes of SST anomalies in the western pole of co-occurring IODs are aided by dynamical and thermodynamical modifications related to the ENSO-induced wind variability. Anomalous latent heat flux and vertical heat convergence associated with the modified Walker circulation contribute to the alteration of western anomalies. It is found that 42% of IOD events affected by changes in the Walker circulation are related to the tropical Pacific variabilities including ENSO. The formation is delayed until boreal summer for those IODs, which otherwise form in boreal spring as in the noENSO experiment.

scholarly journals Weakened Interannual Variability in the Tropical Pacific Ocean since 2000

2013 ◽  
Vol 26 (8) ◽  
pp. 2601-2613 ◽  
Author(s):  
Zeng-Zhen Hu ◽  
Arun Kumar ◽  
Hong-Li Ren ◽  
Hui Wang ◽  
Michelle L’Heureux ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Interannual Variability ◽  
Southern Oscillation ◽  
Walker Circulation ◽  
Tropical Pacific ◽  
Warm Water ◽  
Water Volume ◽  
Tropical Pacific Ocean ◽  
Trade Winds ◽  
The Tropical Pacific

Abstract An interdecadal shift in the variability and mean state of the tropical Pacific Ocean is investigated within the context of changes in El Niño–Southern Oscillation (ENSO). Compared with 1979–99, the interannual variability in the tropical Pacific was significantly weaker in 2000–11, and this shift can be seen by coherent changes in both the tropical atmosphere and ocean. For example, the equatorial thermocline tilt became steeper during 2000–11, which was consistent with positive (negative) sea surface temperature anomalies, increased (decreased) precipitation, and enhanced (suppressed) convection in the western (central and eastern) tropical Pacific, which reflected an intensification of the Walker circulation. The combination of a steeper thermocline slope with stronger surface trade winds is proposed to have hampered the eastward migration of the warm water along the equatorial Pacific. As a consequence, the variability of the warm water volume was reduced and thus ENSO amplitude also decreased. Sensitivity experiments with the Zebiak–Cane model confirm the link between thermocline slope, wind stress, and the amplitude of ENSO.

scholarly journals Overestimated climate warming and climate variability due to spatially homogeneous CO2 in climate modeling over the Northern Hemisphere since the mid-19th century

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Xuezhen Zhang ◽  
Xiaxiang Li ◽  
Deliang Chen ◽  
Huijuan Cui ◽  
Quansheng Ge
Keyword(s):  
Northern Hemisphere ◽  
Climate Warming ◽  
Extreme Events ◽  
Fossil Fuels ◽  
Industrial Revolution ◽  
Climate Modeling ◽  
Walker Circulation ◽  
Tropical Pacific ◽  
The Arctic ◽  
The Tropical Pacific

AbstractSince the mid-19th century, the global atmospheric CO2 concentration (ACC) has increased dramatically due to the burning of fossil fuels. Because of unequal population growth and economic development among regions, the ACC increases possess strong spatial variability. Particularly, the increase in ACC has been larger in the mid-latitudes of the Northern Hemisphere (NH) than that at high- and low-latitudes. It is widely accepted that the ACC increase is the main reason for climate change, but the potential impacts of its spatial distribution on the climate system remain unclear. Therefore, we carried out two groups of 150-year experiments with the Community Earth System Model (CESM), using both spatially inhomogeneous (hereafter the SIC experiment) and homogenous (hereafter the SHC experiment) ACC increases in their settings. We found that the models’ divergences occurred over the NH mid-latitudes, the Arctic and the western part of the tropical Pacific. SHC overestimated (underestimated) climate warming over the Artic (mid-latitudes), which may be induced by the intensified westerly and weakened meridional heat exchange between mid- and high latitudes in the NH. Over the tropical Pacific, the overestimation of climate warming may be induced by intensified Walker circulation coupled with the La Niña climate mode. For the entire NH, relative to SIC, SHC overestimated the climate warming from 1850 to 1999 by ~10%. Meanwhile, the SHC experiment also overestimated the interannual variabilities in temperature and precipitation, resulting in more serious extreme events. These findings suggest that human contributions to climate warming and increased extreme events since the industrial revolution may be overestimated when using a spatially homogenous ACC.

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.

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