scholarly journals Impacts of Atlantic multidecadal variability on the tropical Pacific: a multi-model study

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yohan Ruprich-Robert ◽  
Eduardo Moreno-Chamarro ◽  
Xavier Levine ◽  
Alessio Bellucci ◽  
Christophe Cassou ◽  
...  
Keyword(s):  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Tropical Atlantic ◽  
Atlantic Multidecadal Variability ◽  
Multidecadal Variability ◽  
Upper Troposphere ◽  
Model Study ◽  
Model Set ◽  
Static Energy ◽  
The Tropical Pacific

AbstractAtlantic multidecadal variability (AMV) has been linked to the observed slowdown of global warming over 1998–2012 through its impact on the tropical Pacific. Given the global importance of tropical Pacific variability, better understanding this Atlantic–Pacific teleconnection is key for improving climate predictions, but the robustness and strength of this link are uncertain. Analyzing a multi-model set of sensitivity experiments, we find that models differ by a factor of 10 in simulating the amplitude of the Equatorial Pacific cooling response to observed AMV warming. The inter-model spread is mainly driven by different amounts of moist static energy injection from the tropical Atlantic surface into the upper troposphere. We reduce this inter-model uncertainty by analytically correcting models for their mean precipitation biases and we quantify that, following an observed 0.26 °C AMV warming, the equatorial Pacific cools by 0.11 °C with an inter-model standard deviation of 0.03 °C.

scholarly journals Impacts of Atlantic Multidecadal Variability on the Tropical Pacific: a multi-model study

2021 ◽  
Author(s):  
Yohan Ruprich-Robert ◽  
Keyword(s):  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Tropical Atlantic ◽  
Atlantic Multidecadal Variability ◽  
Multidecadal Variability ◽  
Upper Troposphere ◽  
Model Study ◽  
Model Set ◽  
Static Energy ◽  
The Tropical Pacific

<p>The Atlantic Multidecadal Variability (AMV) has been linked to the observed slowdown of global warming over 1998-2012 through its impact on the tropical Pacific. Given the global importance of tropical Pacific variability, better understanding this Atlantic-Pacific teleconnection is key for improving climate predictions, but the robustness and strength of this link is uncertain. Analysing a multi-model set of sensitivity experiments, we find that models differ by a factor 10 in simulating the amplitude of the Equatorial Pacific cooling response to observed AMV warming. The inter-model spread is mainly driven by different amounts of moist static energy injection from the tropical Atlantic surface into the upper troposphere. We reduce this inter-model uncertainty by analytically correcting models for their mean precipitation biases and we quantify that, following an observed 0.26ºC AMV warming, the equatorial Pacific cools by 0.16ºC with an inter-model standard deviation of 0.03ºC.</p>

scholarly journals A decadally delayed response of the tropical Pacific to Atlantic multidecadal variability

2016 ◽  
Vol 43 (2) ◽  
pp. 784-792 ◽  
Author(s):  
Davide Zanchettin ◽  
Oliver Bothe ◽  
Hans F. Graf ◽  
Nour‐Eddine Omrani ◽  
Angelo Rubino ◽  
...  
Keyword(s):  
Tropical Pacific ◽  
Delayed Response ◽  
Atlantic Multidecadal Variability ◽  
Multidecadal Variability ◽  
The Tropical Pacific

scholarly journals Forcing of the Indian Ocean Dipole on the Interannual Variations of the Tropical Pacific Ocean: Roles of the Indonesian Throughflow

2011 ◽  
Vol 24 (14) ◽  
pp. 3593-3608 ◽  
Author(s):  
Dongliang Yuan ◽  
Jing Wang ◽  
Tengfei Xu ◽  
Peng Xu ◽  
Zhou Hui ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Indonesian Throughflow ◽  
Tropical Pacific Ocean ◽  
Equatorial Pacific Ocean ◽  
The Indian Ocean ◽  
The Tropical Pacific

Abstract Controlled numerical experiments using ocean-only and ocean–atmosphere coupled general circulation models show that interannual sea level depression in the eastern Indian Ocean during the Indian Ocean dipole (IOD) events forces enhanced Indonesian Throughflow (ITF) to transport warm water from the upper-equatorial Pacific Ocean to the Indian Ocean. The enhanced transport produces elevation of the thermocline and cold subsurface temperature anomalies in the western equatorial Pacific Ocean, which propagate to the eastern equatorial Pacific to induce significant coupled evolution of the tropical Pacific oceanic and atmospheric circulation. Analyses suggest that the IOD-forced ITF transport anomalies are about the same amplitudes as those induced by the Pacific ENSO. Results of the coupled model experiments suggest that the anomalies induced by the IOD persist in the equatorial Pacific until the year following the IOD event, suggesting the importance of the oceanic channel in modulating the interannual climate variations of the tropical Pacific Ocean at the time lag beyond one year.

scholarly journals Reducing Climatology Bias in an Ocean–Atmosphere CGCM with Improved Coupling Physics

2005 ◽  
Vol 18 (13) ◽  
pp. 2344-2360 ◽  
Author(s):  
Jing-Jia Luo ◽  
Sebastien Masson ◽  
Erich Roeckner ◽  
Gurvan Madec ◽  
Toshio Yamagata
Keyword(s):  
Wind Stress ◽  
Surface Current ◽  
Ocean Surface ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Eastern Pacific ◽  
Cold Tongue ◽  
Easterly Wind ◽  
Ocean Atmosphere ◽  
The Tropical Pacific

Abstract The cold tongue in the tropical Pacific extends too far west in most current ocean–atmosphere coupled GCMs (CGCMs). This bias also exists in the relatively high-resolution SINTEX-F CGCM despite its remarkable performance of simulating ENSO variations. In terms of the importance of air–sea interactions to the climatology formation in the tropical Pacific, several sensitivity experiments with improved coupling physics have been performed in order to reduce the cold-tongue bias in CGCMs. By allowing for momentum transfer of the ocean surface current to the atmosphere [full coupled simulation (FCPL)] or merely reducing the wind stress by taking the surface current into account in the bulk formula [semicoupled simulation (semi-CPL)], the warm-pool/cold-tongue structure in the equatorial Pacific is simulated better than that of the control simulation (CTL) in which the movement of the ocean surface is ignored for wind stress calculation. The reduced surface zonal current and vertical entrainment owing to the reduced easterly wind stress tend to produce a warmer sea surface temperature (SST) in the western equatorial Pacific. Consequently, the dry bias there is much reduced. The warming tendency of the SST in the eastern Pacific, however, is largely suppressed by isopycnal diffusion and meridional advection of colder SST from south of the equator due to enhanced coastal upwelling near Peru. The ENSO signal in the western Pacific and its global teleconnection in the North Pacific are simulated more realistically. The approach as adopted in the FCPL run is able to generate a correct zonal SST slope and efficiently reduce the cold-tongue bias in the equatorial Pacific. The surface easterly wind itself in the FCPL run is weakened, reducing the easterly wind stress further. This is related with a weakened zonal Walker cell in the atmospheric boundary layer over the eastern Pacific and a new global angular momentum balance of the atmosphere associated with reduced westerly wind stress over the southern oceans.

scholarly journals Upper-Ocean Salinity Variability in the Tropical Pacific: Case Study for Quasi-Decadal Shift during the 2000s Using TRITON Buoys and Argo Floats

2013 ◽  
Vol 26 (20) ◽  
pp. 8126-8138 ◽  
Author(s):  
Takuya Hasegawa ◽  
Kentaro Ando ◽  
Iwao Ueki ◽  
Keisuke Mizuno ◽  
Shigeki Hosoda
Keyword(s):  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Upper Ocean ◽  
Salinity Variability ◽  
Ocean Salinity ◽  
Central Equatorial Pacific ◽  
Western Equatorial Pacific ◽  
Sea Surface Temperature Anomalies ◽  
The Tropical Pacific

Abstract Upper-ocean salinity variation in the tropical Pacific is investigated during the 2000s, when Triangle Trans-Ocean Buoy Network (TRITON) buoys and Argo floats were deployed and more salinity data were observed than in previous periods. This study focuses on upper-ocean salinity variability during the warming period of El Niño–Southern Oscillation (ENSO)-like quasi-decadal (QD)-scale sea surface temperature anomalies over the central equatorial Pacific (January 2002–December 2005; hereafter “warm QD phase”). It is shown that strong negative salinity anomalies occur in the western tropical Pacific and the off-equatorial Pacific in the upper ocean at depths less than 80 m, showing a horseshoe-like pattern centered at the western tropical Pacific during the warm QD phase. TRITON mooring buoy data in the western equatorial Pacific show that low-salinity and high-temperature water could be transported eastward from the western equatorial Pacific to the central equatorial Pacific during the warm QD phase. Similar patterns, but with the opposite sign of salinity anomalies, appear in the cold QD phase during January 2007–December 2009 with negative sea surface temperature anomalies over the central equatorial Pacific. It is suggested that effects from zonal salinity advection and precipitation could contribute to the generation of the salinity variations in the western equatorial Pacific for QD phases during the 2000s. On the other hand, the contribution of meridional salinity advection is much less than that of zonal salinity advection. In addition, El Niño Modoki and La Niña events could affect salinity changes for warm and cold QD phases via interannual-scale zonal salinity advection variations in the western equatorial Pacific during the 2000s.

scholarly journals Atmospheric Energetics over the Tropical Pacific during the ENSO Cycle

2017 ◽  
Vol 30 (10) ◽  
pp. 3635-3654 ◽  
Author(s):  
Di Dong ◽  
Jianping Li ◽  
Lidou Huyan ◽  
Jiaqing Xue
Keyword(s):  
El Nino ◽  
Tropical Pacific ◽  
La Niña ◽  
Western Pacific ◽  
Eastern Pacific ◽  
Enso Cycle ◽  
Upper Troposphere ◽  
La Nina ◽  
Central Eastern ◽  
The Tropical Pacific

Abstract The atmospheric perturbation potential energy (PPE) over the tropical Pacific is calculated and analyzed in a composite ENSO cycle. The PPE over the tropical Pacific troposphere increases during El Niño and decreases during La Niña, displaying two centers symmetrical about the equator and delaying the central–eastern Pacific SST anomaly by two months. Generated from atmospheric diabatic heating, the smaller part of PPE in the lower troposphere varies synchronously with the central–eastern Pacific SST through sensible heating, while the larger part of PPE lies in the mid- and upper troposphere and lags the central–eastern Pacific SST about one season because of latent heat release. As the tropical Pacific PPE peaks during the boreal late winter in an El Niño event, two anticyclones form in the upper troposphere as a result of the Gill model response. More PPE is converted to atmospheric kinetic energy (KE) above the central–western Pacific, but less over the eastern Pacific, leading to intensified Hadley circulations over the central–western Pacific and weakened Hadley circulations over the eastern Pacific. The strengthened Hadley circulations cause surface easterly wind bursts through KE convergence in the western equatorial Pacific, which may trigger a La Niña event. The reverse situation occurs during La Niña. Thus, the response of the Hadley circulations in the central–western Pacific provides a negative feedback during the ENSO cycle.

Evaluating the performance of CMIP6 models in the tropical Atlantic: mean state, variability, and remote impacts

2020 ◽  
Author(s):  
Ingo Richter ◽  
Hiroki Tokinaga
Keyword(s):  
General Circulation ◽  
General Circulation Models ◽  
Tropical Pacific ◽  
Boreal Summer ◽  
Tropical Atlantic ◽  
Westerly Wind ◽  
Equatorial Atlantic ◽  
Wide Range ◽  
Mean State ◽  
The Tropical Pacific

<p>General circulation models of the Coupled Model Intercomparison Project Phase 6 (CMIP6) are examined with respect to their ability to simulate the mean state and variability of the tropical Atlantic, as well as its linkage to the tropical Pacific. While, on average, mean state biases have improved little relative to the previous intercomparison (CMIP5), there are now a few models with very small biases. In particular the equatorial Atlantic warm SST and westerly wind biases are mostly eliminated in these models. Furthermore, interannual variability in the equatorial and subtropical Atlantic is quite realistic in a number of CMIP6 models, which suggests that they should be useful tools for understanding and predicting variability patterns. The evolution of equatorial Atlantic biases follows the same pattern as in previous model generations, with westerly wind biases during boreal spring preceding warm sea-surface temperature (SST) biases in the east during boreal summer. A substantial portion of the westerly wind bias exists already in atmosphere-only simulations forced with observed SST, suggesting an atmospheric origin. While variability is relatively realistic in many models, SSTs seem less responsive to wind forcing than observed, both on the equator and in the subtropics, possibly due to an excessively deep mixed layer originating in the oceanic component. Thus models with realistic SST amplitude tend to have excessive wind amplitude. The models with the smallest mean state biases all have relatively high resolution but there are also a few low-resolution models that perform similarly well, indicating that resolution is not the only way toward reducing tropical Atlantic biases. The results also show a relatively weak link between mean state biases and the quality of the simulated variability. The linkage to the tropical Pacific shows a wide range of behaviors across models, indicating the need for further model improvement.</p>

scholarly journals CAPE Variations in the Current Climate and in a Climate Change

1998 ◽  
Vol 11 (8) ◽  
pp. 1997-2015 ◽  
Author(s):  
Bing Ye ◽  
Anthony D. Del Genio ◽  
Kenneth K-W. Lo
Keyword(s):  
Climate Change ◽  
Relative Humidity ◽  
General Circulation ◽  
Large Scale ◽  
Tropical Pacific ◽  
Lapse Rate ◽  
Moist Convection ◽  
Upper Troposphere ◽  
Current Climate ◽  
The Tropical Pacific

Abstract Observed variations of convective available potential energy (CAPE) in the current climate provide one useful test of the performance of cumulus parameterizations used in general circulation models (GCMs). It is found that frequency distributions of tropical Pacific CAPE, as well as the dependence of CAPE on surface wet-bulb potential temperature (Θw) simulated by the Goddard Institute for Space Studies’s GCM, agree well with that observed during the Australian Monsoon Experiment period. CAPE variability in the current climate greatly overestimates climatic changes in basinwide CAPE in the tropical Pacific in response to a 2°C increase in sea surface temperature (SST) in the GCM because of the different physics involved. In the current climate, CAPE variations in space and time are dominated by regional changes in boundary layer temperature and moisture, which in turn are controlled by SST patterns and large-scale motions. Geographical thermodynamic structure variations in the middle and upper troposphere are smaller because of the canceling effects of adiabatic cooling and subsidence warming in the rising and sinking branches of the Walker and Hadley circulations. In a forced equilibrium global climate change, temperature change is fairly well constrained by the change in the moist adiabatic lapse rate and thus the upper troposphere warms to a greater extent than the surface. For this reason, climate change in CAPE is better predicted by assuming that relative humidity remains constant and that the temperature changes according to the moist adiabatic lapse rate change of a parcel with 80% relative humidity lifted from the surface. The moist adiabatic assumption is not symmetrically applicable to a warmer and colder climate: In a warmer regime moist convection determines the tropical temperature structure, but when the climate becomes colder the effect of moist convection diminishes and the large-scale dynamics and radiative processes become relatively important. Although a prediction based on the change in moist adiabat matches the GCM simulation of climate change averaged over the tropical Pacific basin, it does not match the simulation regionally because small changes in the general circulation change the local boundary layer relative humidity by 1%–2%. Thus, the prediction of regional climate change in CAPE is also dependent on subtle changes in the dynamics.

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