­­Mean Atlantic Subtropical Cells in the CMIP6 models

2021 ◽  
Author(s):  
Yao Fu ◽  
Peter Brandt ◽  
Franz Philip Tuchen ◽  
Joke F. Lübbecke ◽  
Chunzai Wang
Keyword(s):  
State Of The Art ◽  
Coupled Model ◽  
Model Intercomparison ◽  
Coupled Models ◽  
Trade Winds ◽  
Equatorial Undercurrent ◽  
Equatorial Upwelling ◽  
Intercomparison Project ◽  
The Mean ◽  
Mean State

<p>The Atlantic Subtropical Cells (STCs) consist primarily of poleward Ekman divergence in the surface layer, subduction in the subtropics, and equatorward convergence in the thermocline that largely compensates the surface Ekman divergence through equatorial upwelling. As a result, the STCs play an important role in connecting the tropical and subtropical Atlantic Ocean, in terms of heat, freshwater, oxygen, and nutrients transports. However, their representation in state-of-the-art coupled models has not been systematically evaluated so far. In this study, we investigate the performance of the Coupled Model Intercomparison Project phase 6 (CMIP6) models in simulating the Atlantic STCs. Comparing model results with observations, we first present the simulated mean state with respect to ensembles of the key components participating in the STC loop, i.e., the meridional Ekman and geostrophic flow at 10°N and 10°S, and the Equatorial Undercurrent (EUC) at 23°W. We then examine the inter-model spread and the relationships between these key components. We find that there is a general weak bias in the Southern Hemispheric ensemble Ekman transports and mixed-layer geostrophic transports in comparison to the observations. The inter-model spread of mean EUC strengths are primarily associated with the intensity of the mean wind stress in the tropical South Atlantic among the models. Since the poleward Ekman transports induced by the trade winds are regarded as the driver of the STC loop, our results point out the necessity to improve skills of coupled models to simulate the Southern Hemisphere atmospheric forcing in driving the Atlantic STCs.</p>

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.

scholarly journals Uncertainties in projected surface mass balance over the polar ice sheets from downscaled EC-Earth models

2021 ◽  
Author(s):  
Fredrik Boberg ◽  
Ruth Mottram ◽  
Nicolaj Hansen ◽  
Shuting Yang ◽  
Peter L. Langen
Keyword(s):  
Mass Balance ◽  
Climate Model ◽  
Global Climate ◽  
Ice Sheet ◽  
Coupled Model ◽  
Surface Mass Balance ◽  
Model Intercomparison ◽  
Surface Mass ◽  
Intercomparison Project ◽  
The Mean

Abstract. The future rates of ice sheet melt in Greenland and Antarctica are an important factor when making estimates of the likely rate of sea level rise. Global climate models that took part in the fifth Coupled Model Intercomparison Project (CMIP5) have generally been unable to replicate observed rates of ice sheet melt. With the advent of the sixth Coupled Model Intercomparison Project (CMIP6), with a general increase in the equilibrium climate sensitivity, we here compare two versions of the global climate model EC-Earth using the regional climate model HIRHAM5 downscaling EC-Earth for Greenland and Antarctica. One version (v2) of EC-Earth is taken from CMIP5 for the high-emissions Representative Concentration Pathways (RCP8.5) scenario and the other (v3) from CMIP6 for the comparable high-emissions Shared Socioeconomic Pathways (SSP5-8.5) scenario). For Greenland, we downscale the two versions of EC-Earth for the historical period 1991–2010 and for the scenario period 2081–2100. For Antarctica, the periods are 1971–2000 and 2071–2100, respectively. For the Greenland Ice Sheet, we find that the mean change in temperature is 5.9 °C when downscaling EC-Earth v2 and 6.8 °C when downscaling EC-Earth v3. Corresponding values for Antarctica are 4.1 °C for v2 and 4.8 °C for v3. The mean change in surface mass balance at the end of the century under these high emissions scenarios is found to be −210 Gt yr−1 (v2) and −1150 Gt yr−1 (v3) for Greenland and 420 Gt yr−1 (v2) and 80 Gt yr−1 (v3) for Antarctica. These distinct differences in temperature change and particularly surface mass balance change are a result of the higher equilibrium climate sensitivity in EC-Earth v3 (4.3 K) compared with 3.3 K in EC-Earth v2 and the differences in greenhouse gas concentrations between the RCP8.5 and the SSP5-8.5 scenarios.

scholarly journals LICOM Model Datasets for the CMIP6 Ocean Model Intercomparison Project

2020 ◽  
Vol 37 (3) ◽  
pp. 239-249 ◽  
Author(s):  
Pengfei Lin ◽  
Zhipeng Yu ◽  
Hailong Liu ◽  
Yongqiang Yu ◽  
Yiwen Li ◽  
...  
Keyword(s):  
Coupled Model ◽  
Reanalysis Data ◽  
Ocean Model ◽  
Model Intercomparison ◽  
Surface Data ◽  
Intercomparison Project ◽  
System Bias ◽  
The Mean ◽  
Fully Coupled

Abstract The datasets of two Ocean Model Intercomparison Project (OMIP) simulation experiments from the LASG/IAP Climate Ocean Model, version 3 (LICOM3), forced by two different sets of atmospheric surface data, are described in this paper. The experiment forced by CORE-II (Co-ordinated Ocean–Ice Reference Experiments, Phase II) data (1948–2009) is called OMIP1, and that forced by JRA55-do (surface dataset for driving ocean–sea-ice models based on Japanese 55-year atmospheric reanalysis) data (1958–2018) is called OMIP2. First, the improvement of LICOM from CMIP5 to CMIP6 and the configurations of the two experiments are described. Second, the basic performances of the two experiments are validated using the climatological-mean and interannual time scales from observation. We find that the mean states, interannual variabilities, and long-term linear trends can be reproduced well by the two experiments. The differences between the two datasets are also discussed. Finally, the usage of these data is described. These datasets are helpful toward understanding the origin system bias of the fully coupled model.

scholarly journals An Initial Assessment of Antarctic Sea Ice Extent in the CMIP5 Models

2013 ◽  
Vol 26 (5) ◽  
pp. 1473-1484 ◽  
Author(s):  
John Turner ◽  
Thomas J. Bracegirdle ◽  
Tony Phillips ◽  
Gareth J. Marshall ◽  
J. Scott Hosking
Keyword(s):  
Sea Ice ◽  
Coupled Model ◽  
Initial Assessment ◽  
Cmip5 Models ◽  
Full Time ◽  
Model Intercomparison ◽  
Sea Ice Extent ◽  
Antarctic Sea Ice ◽  
Intercomparison Project ◽  
The Mean

Abstract This paper examines the annual cycle and trends in Antarctic sea ice extent (SIE) for 18 models used in phase 5 of the Coupled Model Intercomparison Project (CMIP5) that were run with historical forcing for the 1850s to 2005. Many of the models have an annual SIE cycle that differs markedly from that observed over the last 30 years. The majority of models have too small of an SIE at the minimum in February, while several of the models have less than two-thirds of the observed SIE at the September maximum. In contrast to the satellite data, which exhibit a slight increase in SIE, the mean SIE of the models over 1979–2005 shows a decrease in each month, with the greatest multimodel mean percentage monthly decline of 13.6% decade−1 in February and the greatest absolute loss of ice of −0.40 × 106 km2 decade−1 in September. The models have very large differences in SIE over 1860–2005. Most of the control runs have statistically significant trends in SIE over their full time span, and all of the models have a negative trend in SIE since the mid-nineteenth century. The negative SIE trends in most of the model runs over 1979–2005 are a continuation of an earlier decline, suggesting that the processes responsible for the observed increase over the last 30 years are not being simulated correctly.

scholarly journals The OASIS3 coupler: a European climate modelling community software

2012 ◽  
Vol 5 (3) ◽  
pp. 2139-2178 ◽  
Author(s):  
S. Valcke
Keyword(s):  
Coupled Model ◽  
Climate Modelling ◽  
Model Intercomparison ◽  
Short History ◽  
Coupled Models ◽  
European Climate ◽  
History Of ◽  
Intercomparison Project ◽  
Community Software ◽  
Earth System Models

Abstract. This paper presents the OASIS3 software used in five of the seven European Earth System Models (ESMs) participating to the Fifth Coupled Model Intercomparison Project (CMIP5). A short history of the coupler development and a description of its large community of users are followed by a detailed OASIS3 technical description. The performances of few relatively high resolution OASIS3 coupled models are then described and show that even if its limited field-per-field parallelism will eventually become a bottleneck in the simulation, OASIS3 can still be considered an appropriate tool for most of these relatively heavy coupled configurations. Its successful use in different CMIP5 ESMs is then detailed. A discussion of the benefits and drawbacks of the OASIS3 approach and a presentation of planned developments conclude the paper.

scholarly journals Understanding the CMIP3 Multimodel Ensemble

2011 ◽  
Vol 24 (16) ◽  
pp. 4529-4538 ◽  
Author(s):  
J. D. Annan ◽  
J. C. Hargreaves
Keyword(s):  
Coupled Model ◽  
Model Intercomparison ◽  
Ensemble Size ◽  
Multimodel Ensemble ◽  
Phase 3 ◽  
Climate Research ◽  
Intercomparison Project ◽  
The Mean ◽  
Main Factors ◽  
And Behavior

Abstract The Coupled Model Intercomparison Project phase 3 (CMIP3) multimodel ensemble has been widely utilized for climate research and prediction, but the properties and behavior of the ensemble are not yet fully understood. Here, some investigations are undertaken into various aspects of the ensemble’s behavior, in particular focusing on the performance of the multimodel mean. This study presents an explanation of this phenomenon in the context of the statistically indistinguishable paradigm and also provides a quantitative analysis of the main factors that control how likely the mean is to outperform the models in the ensemble, both individually and collectively. The analyses lend further support to the usage of the paradigm of a statistically indistinguishable ensemble and indicate that the current ensemble size is too small to adequately sample the space from which the models are drawn.

scholarly journals Higher mass loss over Greenland and Antarctic ice sheets projected in CMIP6 than CMIP5 by high resolution regional downscaling EC-Earth

2020 ◽  
Author(s):  
Fredrik Boberg ◽  
Ruth Mottram ◽  
Nicolaj Hansen ◽  
Shuting Yang ◽  
Peter L. Langen
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Ice Sheet ◽  
Coupled Model ◽  
Surface Mass Balance ◽  
Model Intercomparison ◽  
Surface Mass ◽  
Equilibrium Climate Sensitivity ◽  
Intercomparison Project ◽  
The Mean

Abstract. The future rates of ice sheet melt in Greenland and Antarctica are an important factor when making estimates of the likely rate of sea level rise. Global climate models that took part in the fifth Coupled Model Intercomparison Project (CMIP5) have generally been unable to replicate observed rates of ice sheet melt. With the advent of the sixth Coupled Model Intercomparison Project (CMIP6), with a general increase in the equilibrium climate sensitivity, we here compare two versions of the global climate model EC-Earth using the regional climate model HIRHAM5 downscaling EC-Earth for Greenland and Antarctica. One version (v2) of EC-Earth is taken from CMIP5 for the high-emissions Representative Concentration Pathways (RCP8.5) scenario and the other (v3) from CMIP6 for the comparable high-emissions Shared Socioeconomic Pathways (SSP5-8.5) scenario). For Greenland, we downscale the two versions of EC-Earth for the historical period 1991–2010 and for the scenario period 2081–2100. For Antarctica, the periods are 1971–2000 and 2071–2100, respectively. For the Greenland Ice Sheet, we find that the mean change in temperature is 5.9 °C when downscaling EC-Earth v2 and 6.8 °C when downscaling EC-Earth v3. Corresponding values for Antarctica are 4.1 °C for v2 and 4.9 °C for v3. The mean change in surface mass balance at the end of the century under these high emissions scenarios is found to be −210 Gt yr−1 (v2) and −1150 Gt yr−1 (v3) for Greenland and +150 Gt yr−1 (v2) and −710 Gt yr−1 (v3) for Antarctica. These distinct differences in temperature change and particularly surface mass balance change are a result of the higher equilibrium climate sensitivity in EC-Earth v3 (4.3 K) compared with 3.3 K in EC-Earth v2 and the differences in greenhouse gas concentrations between the RCP8.5 and the SSP5-8.5 scenarios.

scholarly journals ENSO Asymmetry in CMIP5 Models

2014 ◽  
Vol 27 (11) ◽  
pp. 4070-4093 ◽  
Author(s):  
Tao Zhang ◽  
De-Zheng Sun
Keyword(s):  
Coupled Model ◽  
La Niña ◽  
Eastern Pacific ◽  
Cmip5 Models ◽  
Model Intercomparison ◽  
Coupled Models ◽  
Zonal Winds ◽  
La Nina ◽  
Enso Asymmetry ◽  
Intercomparison Project

Abstract The El Niño–La Niña asymmetry is evaluated in 14 coupled models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). The results show that an underestimate of ENSO asymmetry, a common problem noted in CMIP3 models, remains a common problem in CMIP5 coupled models. The weaker ENSO asymmetry in the models primarily results from a weaker SST warm anomaly over the eastern Pacific and a westward shift of the center of the anomaly. In contrast, SST anomalies for the La Niña phase are close to observations. Corresponding Atmospheric Model Intercomparison Project (AMIP) runs are analyzed to understand the causes of the underestimate of ENSO asymmetry in coupled models. The analysis reveals that during the warm phase, precipitation anomalies are weaker over the eastern Pacific, and westerly wind anomalies are confined more to the west in most models. The time-mean zonal winds are stronger over the equatorial central and eastern Pacific for most models. Wind-forced ocean GCM experiments suggest that the stronger time-mean zonal winds and weaker asymmetry in the interannual anomalies of the zonal winds in AMIP models can both be a contributing factor to a weaker ENSO asymmetry in the corresponding coupled models, but the former appears to be a more fundamental factor, possibly through its impact on the mean state. The study suggests that the underestimate of ENSO asymmetry in the CMIP5 coupled models is at least in part of atmospheric origin.

scholarly journals Uncertainties in projected surface mass balance over the polar ice sheets from dynamically downscaled EC-Earth models

2022 ◽  
Vol 16 (1) ◽  
pp. 17-33
Author(s):  
Fredrik Boberg ◽  
Ruth Mottram ◽  
Nicolaj Hansen ◽  
Shuting Yang ◽  
Peter L. Langen
Keyword(s):  
Mass Balance ◽  
Climate Model ◽  
Global Climate ◽  
Ice Sheet ◽  
Coupled Model ◽  
Surface Mass Balance ◽  
Model Intercomparison ◽  
Surface Mass ◽  
Intercomparison Project ◽  
The Mean

Abstract. The future rates of ice sheet melt in Greenland and Antarctica are an important factor when making estimates of the likely rate of sea level rise. Global climate models that took part in the fifth Coupled Model Intercomparison Project (CMIP5) have generally been unable to replicate observed rates of ice sheet melt. With the advent of the sixth Coupled Model Intercomparison Project (CMIP6), with a general increase in the equilibrium climate sensitivity, we here compare two versions of the global climate model EC-Earth using the regional climate model HIRHAM5 downscaling of EC-Earth for Greenland and Antarctica. One version (v2) of EC-Earth is taken from CMIP5 for the high-emissions Representative Concentration Pathway 8.5 (RCP8.5) scenario and the other (v3) from CMIP6 for the comparable high-emissions Shared Socioeconomic Pathway 5-8.5 (SSP5-8.5) scenario. For Greenland, we downscale the two versions of EC-Earth for the historical period 1991–2010 and for the scenario period 2081–2100. For Antarctica, the periods are 1971–2000 and 2071–2100, respectively. For the Greenland Ice Sheet, we find that the mean change in temperature is 5.9 ∘C when downscaling EC-Earth v2 and 6.8 ∘C when downscaling EC-Earth v3. Corresponding values for Antarctica are 4.1 ∘C for v2 and 4.8 ∘C for v3. The mean change in surface mass balance at the end of the century under these high-emissions scenarios is found to be −290 Gt yr−1 (v2) and −1640 Gt yr−1 (v3) for Greenland and 420 Gt yr−1 (v2) and 80 Gt yr−1 (v3) for Antarctica. These distinct differences in temperature change and particularly surface mass balance change are a result of the higher equilibrium climate sensitivity in EC-Earth v3 (4.3 K) compared with 3.3 K in EC-Earth v2 and the differences in greenhouse gas concentrations between the RCP8.5 and the SSP5-8.5 scenarios.

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