The Tropical Pacific ENSO–Mean State Relationship in Climate Models over the Last Millennium

AbstractENSO and the mean zonal sea surface temperature gradient (dSST) of the tropical Pacific are important drivers of global climate and vary on decadal to centennial time scales. However, the relationship between dSST and ENSO cannot be assessed with the short instrumental record, and is uncertain in proxy data, with intervals of both stronger and weaker ENSO postulated to occur with overall strong dSST in the past. Here we assess the ENSO–dSST relationship during the last millennium using general circulation models (GCMs) participating in phase 3 of the Paleoclimate Modeling Intercomparison Project. Last millennium GCM simulations show diversity in the strength and direction of the ENSO–dSST relationship. Yet, the models that best simulate modern tropical Pacific climate frequently have a more negative ENSO–dSST correlation. Thus, last millennium tropical Pacific climate simulations support the likelihood of enhanced ENSO during decadal to centennial periods of reduced tropical Pacific dSST. However, the alternating directional ENSO–dSST relationship in all model simulations suggests that this relationship is not constant through time and is likely controlled by multiple mechanisms.

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First assessment of the earth heat inventory within CMIP5 historical simulations

Earth System Dynamics ◽

10.5194/esd-12-581-2021 ◽

2021 ◽

Vol 12 (2) ◽

pp. 581-600

Author(s):

Francisco José Cuesta-Valero ◽

Almudena García-García ◽

Hugo Beltrami ◽

Joel Finnis

Keyword(s):

General Circulation ◽

Heat Storage ◽

Global Climate ◽

Heat Content ◽

Coupled Model ◽

General Circulation Models ◽

The Earth ◽

Climate Simulations ◽

Intercomparison Project ◽

Common Era

Abstract. The energy imbalance at the top of the atmosphere over the last century has caused an accumulation of heat within the ocean, the continental subsurface, the atmosphere and the cryosphere. Although ∼90 % of the energy gained by the climate system has been stored in the ocean, the other components of the Earth heat inventory cannot be neglected due to their influence on associated climate processes dependent on heat storage, such as sea level rise and permafrost stability. However, there has not been a comprehensive assessment of the heat inventory within global climate simulations yet. Here, we explore the ability of 30 advanced general circulation models (GCMs) from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) to simulate the distribution of heat within the Earth's energy reservoirs for the period 1972–2005 of the Common Era. CMIP5 GCMs simulate an average heat storage of 247±172 ZJ (96±4 % of total heat content) in the ocean, 5±9 ZJ (2±3 %) in the continental subsurface, 2±3 ZJ (1±1 %) in the cryosphere and 2±2 ZJ (1±1 %) in the atmosphere. However, the CMIP5 ensemble overestimates the ocean heat content by 83 ZJ and underestimates the continental heat storage by 9 ZJ and the cryosphere heat content by 5 ZJ, in comparison with recent observations. The representation of terrestrial ice masses and the continental subsurface, as well as the response of each model to the external forcing, should be improved in order to obtain better representations of the Earth heat inventory and the partition of heat among climate subsystems in global transient climate simulations.

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First Assessment of the Earth Heat Inventory Within CMIP5 Historical Simulations

10.5194/esd-2020-88 ◽

2020 ◽

Author(s):

Francisco José Cuesta-Valero ◽

Almudena García-García ◽

Hugo Beltrami ◽

Joel Finnis

Keyword(s):

General Circulation ◽

Heat Storage ◽

Global Climate ◽

Heat Content ◽

Coupled Model ◽

General Circulation Models ◽

The Earth ◽

Climate Simulations ◽

Intercomparison Project ◽

Common Era

Abstract. The energy imbalance at the top of the atmosphere over the last century has caused an accumulation of heat within the ocean, the continental subsurface, the atmosphere and the cryosphere. Although ~90 % of the energy gained by the climate system has been stored in the ocean, the other components of the Earth heat inventory cannot be neglected due to their influence on associated climate processes dependent on heat storage, such as sea level rise and permafrost stability. However, there has not been a comprehensive assessment of the heat inventory within global climate simulations yet. Here, we explore the ability of thirty advanced General Circulation Models (GCMs) from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) to simulate the distribution of heat within the Earth's energy reservoirs for the period 1972–2005 of the Common Era. CMIP5 GCMs simulate an average heat storage of 247 ± 172 ZJ (96 ± 4 % of total heat content) in the ocean, 5 ± 9 ZJ (2 ± 3 %) in the continental subsurface, 2 ± 3 ZJ (1 ± 1 %) in the cryosphere, and 2 ± 2 ZJ (1 ± 1 %) in the atmosphere. However, the CMIP5 ensemble overestimates the ocean heat content by 83 ZJ and underestimates the continental heat storage by 9 ZJ and the cryosphere heat content by 5 ZJ, in comparison with recent observations. The representation of terrestrial ice masses and the continental subsurface, as well as the response of each model to the external forcing, should be improved in order to obtain better representations of the Earth heat inventory and the partition of heat among climate subsystems in global transient climate simulations.

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Successive Modulation of ENSO to the Future Greenhouse Warming

Journal of Climate ◽

10.1175/2007jcli1500.1 ◽

2008 ◽

Vol 21 (1) ◽

pp. 3-21 ◽

Cited By ~ 55

Author(s):

Soon-Il An ◽

Jong-Seong Kug ◽

Yoo-Geun Ham ◽

In-Sik Kang

Keyword(s):

General Circulation ◽

Southern Oscillation ◽

General Circulation Models ◽

Tropical Pacific ◽

Greenhouse Warming ◽

Delayed Response ◽

Subsurface Temperature ◽

Climate System Model ◽

The Mean ◽

The Tropical Pacific

Abstract The multidecadal modulation of the El Niño–Southern Oscillation (ENSO) due to greenhouse warming has been analyzed herein by means of diagnostics of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) coupled general circulation models (CGCMs) and the eigenanalysis of a simplified version of an intermediate ENSO model. The response of the global-mean troposphere temperature to increasing greenhouse gases is more likely linear, while the amplitude and period of ENSO fluctuates in a multidecadal time scale. The climate system model outputs suggest that the multidecadal modulation of ENSO is related to the delayed response of the subsurface temperature in the tropical Pacific compared to the response time of the sea surface temperature (SST), which would lead a modulation of the vertical temperature gradient. Furthermore, an eigenanalysis considering only two parameters, the changes in the zonal contrast of the mean background SST and the changes in the vertical contrast between the mean surface and subsurface temperatures in the tropical Pacific, exhibits a good agreement with the CGCM outputs in terms of the multidecadal modulations of the ENSO amplitude and period. In particular, the change in the vertical contrast, that is, change in difference between the subsurface temperature and SST, turns out to be more influential on the ENSO modulation than changes in the mean SST itself.

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Tropical Atmospheric Variability Forced by Oceanic Internal Variability

Journal of Climate ◽

10.1175/jcli4044.1 ◽

2007 ◽

Vol 20 (4) ◽

pp. 765-771 ◽

Cited By ~ 17

Author(s):

Markus Jochum ◽

Clara Deser ◽

Adam Phillips

Keyword(s):

General Circulation ◽

Climate Models ◽

Rainfall Variability ◽

Circulation Model ◽

Internal Variability ◽

Tropical Pacific ◽

Atmospheric Variability ◽

Instability Waves ◽

Tropical Instability Waves ◽

The Tropical Pacific

Abstract Atmospheric general circulation model experiments are conducted to quantify the contribution of internal oceanic variability in the form of tropical instability waves (TIWs) to interannual wind and rainfall variability in the tropical Pacific. It is found that in the tropical Pacific, along the equator, and near 25°N and 25°S, TIWs force a significant increase in wind and rainfall variability from interseasonal to interannual time scales. Because of the stochastic nature of TIWs, this means that climate models that do not take them into account will underestimate the strength and number of extreme events and may overestimate forecast capability.

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Boundary conditions for the Middle Miocene Climate Transition (MMCT v1.0)

10.5194/gmd-2017-171 ◽

2017 ◽

Author(s):

Amanda Frigola ◽

Matthias Prange ◽

Michael Schulz

Keyword(s):

Boundary Conditions ◽

General Circulation ◽

Middle Miocene ◽

Climate Models ◽

Global Climate ◽

Co2 Concentration ◽

General Circulation Models ◽

Global Climate Models ◽

Ice Volume ◽

Climate Transition

Abstract. The Middle Miocene Climate Transition was characterized by major Antarctic ice-sheet expansion and global cooling during the interval ~ 15–13 Ma. Here we present two sets of boundary conditions for global general circulation models characterizing the periods before (Middle Miocene Climatic Optimum; MMCO) and after (Middle Miocene Glaciation; MMG) the transition. These boundary conditions include Middle Miocene global topography, bathymetry and vegetation. Additionally, Antarctic ice volume and geometry, sea-level and atmospheric CO2 concentration estimates for the MMCO and the MMG are reviewed. The boundary-condition files are available for use as input in a wide variety of global climate models and constitute a valuable tool for modeling studies with a focus on the Middle Miocene.

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An ensemble of AMIP simulations with prescribed land surface temperatures

10.5194/gmd-2018-77 ◽

2018 ◽

Author(s):

Duncan Ackerley ◽

Robin Chadwick ◽

Dietmar Dommenget ◽

Paola Petrelli

Keyword(s):

Surface Temperature ◽

Land Surface ◽

General Circulation ◽

Global Climate ◽

General Circulation Models ◽

Solar Constant ◽

Surface Temperatures ◽

Co2 Concentrations ◽

Land Surface Temperatures ◽

Intercomparison Project

Abstract. General circulation models (GCMs) are routinely run under Atmospheric Modelling Intercomparison Project (AMIP) conditions with prescribed sea surface temperatures (SSTs) and sea ice concentrations (SICs) from observations. These AMIP simulations are often used to evaluate the role of the land and/or atmosphere in causing the development of systematic errors in such GCMs. Extensions to the original AMIP experiment have also been developed to evaluate the response of the global climate to increased SSTs (prescribed) and carbon-dioxide (CO2) as part of the Cloud Feedback Model Intercomparison Project (CFMIP). None of these international modelling initiatives has undertaken a set of experiments where the land conditions are also prescribed, which is the focus of the work presented in this paper. Experiments are performed initially with freely varying land conditions (surface temperature and, soil temperature and mositure) under five different configurations (AMIP, AMIP with uniform 4 K added to SSTs, AMIP SST with quadrupled CO2, AMIP SST and quadrupled CO2 without the plant stomata response, and increasing the solar constant by 3.3 %). Then, the land surface temperatures from the free-land experiments are used to perform a set of “AMIP-prescribed land” (PL) simulations, which are evaluated against their free-land counterparts. The PL simulations agree well with the free-land experiments, which indicates that the land surface is prescribed in a way that is consistent with the original free-land configuration. Further experiments are also performed with different combinations of SSTs, CO2 concentrations, solar constant and land conditions. For example, SST and land conditions are used from the AMIP simulation with quadrupled CO2 in order to simulate the atmospheric response to increased CO2 concentrations without the surface temperature changing. The results of all these experiments have been made publicly available for further analysis. The main aims of this paper are to provide a description of the method used and an initial validation of these AMIP-prescribed land experiments.

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An Equatorial Ocean Bottleneck in Global Climate Models

Journal of Climate ◽

10.1175/jcli-d-11-00059.1 ◽

2012 ◽

Vol 25 (1) ◽

pp. 343-349 ◽

Cited By ~ 19

Author(s):

Kristopher B. Karnauskas ◽

Gregory C. Johnson ◽

Raghu Murtugudde

Keyword(s):

Ocean Circulation ◽

Radiative Forcing ◽

Climate Models ◽

Global Climate ◽

Critical Role ◽

Tropical Pacific ◽

Global Climate Models ◽

Momentum Balance ◽

Equatorial Ocean ◽

The Tropical Pacific

Abstract The Equatorial Undercurrent (EUC) is a major component of the tropical Pacific Ocean circulation. EUC velocity in most global climate models is sluggish relative to observations. Insufficient ocean resolution slows the EUC in the eastern Pacific where nonlinear terms should dominate the zonal momentum balance. A slow EUC in the east creates a bottleneck for the EUC to the west. However, this bottleneck does not impair other major components of the tropical circulation, including upwelling and poleward transport. In most models, upwelling velocity and poleward transport divergence fall within directly estimated uncertainties. Both of these transports play a critical role in a theory for how the tropical Pacific may change under increased radiative forcing, that is, the ocean dynamical thermostat mechanism. These findings suggest that, in the mean, global climate models may not underrepresent the role of equatorial ocean circulation, nor perhaps bias the balance between competing mechanisms for how the tropical Pacific might change in the future. Implications for model improvement under higher resolution are also discussed.

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

10.5194/egusphere-egu2020-12722 ◽

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>

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On the potential use of glacier and permafrost observations for verification of climate models

Annals of Glaciology ◽

10.1017/s026030550001435x ◽

1997 ◽

Vol 25 ◽

pp. 400-406 ◽

Cited By ~ 2

Author(s):

Martin Beniston ◽

Wilfried Haeberli ◽

Martin Hoelzle ◽

Alan Taylor

Keyword(s):

General Circulation ◽

Climate Models ◽

Climate Model ◽

Global Climate ◽

Regional Climate ◽

Model Performance ◽

Regional Climate Models ◽

General Circulation Models ◽

Model Verification ◽

Dominant Feature

While the capability of global and regional climate models in reproducing current climate has significantly improved over the past few years, the confidence in model results for remote regions, or those where complex orography is a dominant feature, is still relatively low. This is, in part, linked to the lack of observational data for model verification and intercomparison purposes.Glacier and permafrost observations are directly related to past and present energy flux patterns at the Earth-atmosphere interface and could be used as a proxy for air temperature and precipitation, particularly of value in remote mountain regions and boreal and Arctic zones where instrumental climate records are sparse or non-existent. It is particularly important to verify climate-model performance in these regions, as this is where most general circulation models (GCMs) predict the greatest changes in air temperatures in a warmer global climate.Existing datasets from glacier and permafrost monitoring sites in remote and high altitudes are described in this paper; the data could be used in model-verification studies, as a means to improving model performance in these regions.

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The Climatology of the Atmospheric Boundary Layer in Contemporary Global Climate Models

Journal of Climate ◽

10.1175/jcli-d-17-0498.1 ◽

2018 ◽

Vol 31 (22) ◽

pp. 9151-9173 ◽

Cited By ~ 6

Author(s):

Richard Davy

Keyword(s):

Boundary Layer ◽

General Circulation ◽

Climate Models ◽

Global Climate ◽

Coupled Model ◽

General Circulation Models ◽

Global Climate Models ◽

Cmip5 Models ◽

Seasonal Cycles ◽

Layer Depth

Here, we present the climatology of the planetary boundary layer depth in 18 contemporary general circulation models (GCMs) in simulations of the late-twentieth-century climate that were part of phase 5 of the Coupled Model Intercomparison Project (CMIP5). We used a bulk Richardson methodology to establish the boundary layer depth from the 6-hourly synoptic-snapshot data available in the CMIP5 archives. We present an ensemble analysis of the climatological mean, diurnal cycle, and seasonal cycle of the boundary layer depth in these models and compare it to the climatologies from the ECMWF ERA-Interim reanalysis. Overall, we find that the CMIP5 models do a reasonably good job of reproducing the distribution of mean boundary layer depth, although the geographical patterns vary considerably between models. However, the models are biased toward weaker diurnal and seasonal cycles in the boundary layer depth and generally produce much deeper boundary layers at night and during the winter than are found in the reanalysis. These biases are likely to reduce the ability of these models to accurately represent other properties of the diurnal and seasonal cycles, and the sensitivity of these cycles to climate change.

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