scholarly journals Process-level improvements in CMIP5 models and their impact on tropical variability, Southern Ocean and monsoons

2017 ◽  
Author(s):  
Axel Lauer ◽  
Colin Jones ◽  
Veronika Eyring ◽  
Martin Evaldsson ◽  
Stefan Hagemann ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Coupled Model ◽  
Cmip5 Models ◽  
Earth System ◽  
Evaluation Tool ◽  
Coupled Models ◽  
Improvement Project ◽  
Inter Tropical Convergence Zone ◽  
Rainfall Analysis ◽  
Systematic Biases

Abstract. The performance of improved versions of the four earth system models (ESMs) CNRM, EC-Earth, HadGEM, and MPI-ESM is assessed in comparison to their predecessor versions used in Phase 5 of the Coupled Model Intercomparison Project. The earth System Model Evaluation Tool (ESMValTool) is applied to evaluate selected climate phenomena in the models against observations. This is the first systematic application of the ESMValTool to assess and document the progress made during an extensive model development and improvement project. This study focuses on the South Asian (SAM) and West African (WAM) monsoons, the coupled equatorial climate, and Southern Ocean clouds and radiation, which are known to exhibit systematic biases in present-day ESMs. The analysis shows that the tropical precipitation in three out of four models is significantly improved. Two of three updated coupled models show an improved representation of tropical sea surface temperatures with one coupled model not exhibiting a double Inter-Tropical Convergence Zone. Simulated cloud amounts and cloud-radiation interactions are improved over the Southern Ocean. Improvements are also seen in the simulation of the SAM and WAM, although systematic biases remain in regional details and the timing of monsoon rainfall. Analysis of simulations with EC-Earth at different horizontal resolutions from T159 up to T1279 shows that the synoptic-scale variability of precipitation over the SAM and WAM regions improves with higher model resolution. The results suggest the reasonably good agreement of modeled and observed mean WAM and SAM rainfall in lower resolution models may be a result of unrealistic intensity distributions.

scholarly journals Process-level improvements in CMIP5 models and their impact on tropical variability, the Southern Ocean, and monsoons

2018 ◽  
Vol 9 (1) ◽  
pp. 33-67 ◽  
Author(s):  
Axel Lauer ◽  
Colin Jones ◽  
Veronika Eyring ◽  
Martin Evaldsson ◽  
Stefan Hagemann ◽  
...  
Keyword(s):  
Southern Ocean ◽  
West African Monsoon ◽  
Coupled Model ◽  
Cmip5 Models ◽  
Earth System ◽  
Evaluation Tool ◽  
Coupled Models ◽  
Improvement Project ◽  
Rainfall Analysis ◽  
Systematic Biases

Abstract. The performance of updated versions of the four earth system models (ESMs) CNRM, EC-Earth, HadGEM, and MPI-ESM is assessed in comparison to their predecessor versions used in Phase 5 of the Coupled Model Intercomparison Project. The Earth System Model Evaluation Tool (ESMValTool) is applied to evaluate selected climate phenomena in the models against observations. This is the first systematic application of the ESMValTool to assess and document the progress made during an extensive model development and improvement project. This study focuses on the South Asian monsoon (SAM) and the West African monsoon (WAM), the coupled equatorial climate, and Southern Ocean clouds and radiation, which are known to exhibit systematic biases in present-day ESMs. The analysis shows that the tropical precipitation in three out of four models is clearly improved. Two of three updated coupled models show an improved representation of tropical sea surface temperatures with one coupled model not exhibiting a double Intertropical Convergence Zone (ITCZ). Simulated cloud amounts and cloud–radiation interactions are improved over the Southern Ocean. Improvements are also seen in the simulation of the SAM and WAM, although systematic biases remain in regional details and the timing of monsoon rainfall. Analysis of simulations with EC-Earth at different horizontal resolutions from T159 up to T1279 shows that the synoptic-scale variability in precipitation over the SAM and WAM regions improves with higher model resolution. The results suggest that the reasonably good agreement of modeled and observed mean WAM and SAM rainfall in lower-resolution models may be a result of unrealistic intensity distributions.

scholarly journals Southern Ocean Wind Stress in CMIP5 Models: Role of Wind Fluctuations

2020 ◽  
Vol 33 (4) ◽  
pp. 1209-1226 ◽  
Author(s):  
Xia Lin ◽  
Xiaoming Zhai ◽  
Zhaomin Wang ◽  
David R. Munday
Keyword(s):  
Southern Ocean ◽  
Time Scales ◽  
Wind Stress ◽  
Surface Wind ◽  
Coupled Model ◽  
Cmip5 Models ◽  
Coupled Models ◽  
Surface Wind Stress ◽  
Stress Changes ◽  
The Mean

AbstractThe Southern Ocean (SO) surface wind stress is a major atmospheric forcing for driving the Antarctic Circumpolar Current and the global overturning circulation. Here the effects of wind fluctuations at different time scales on SO wind stress in 18 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are investigated. It is found that including wind fluctuations, especially on time scales associated with synoptic storms, in the stress calculation strongly enhances the mean strength, modulates the seasonal cycle, and significantly amplifies the trends of SO wind stress. In 11 out of the 18 CMIP5 models, the SO wind stress has strengthened significantly over the period of 1960–2005. Among them, the strengthening trend of SO wind stress in one CMIP5 model is due to the increase in the intensity of wind fluctuations, while in all the other 10 models the strengthening trend is due to the increasing strength of the mean westerly wind. These discrepancies in SO wind stress trend in CMIP5 models may explain some of the diverging behaviors in the model-simulated SO circulation. Our results suggest that to reduce the uncertainty in SO responses to wind stress changes in the coupled models, both the mean wind and wind fluctuations need to be better simulated.

scholarly journals ESMValTool (v1.0) – a community diagnostic and performance metrics tool for routine evaluation of Earth System Models in CMIP

2015 ◽  
Vol 8 (9) ◽  
pp. 7541-7661 ◽  
Author(s):  
V. Eyring ◽  
M. Righi ◽  
M. Evaldsson ◽  
A. Lauer ◽  
S. Wenzel ◽  
...  
Keyword(s):  
Performance Metrics ◽  
Stratospheric Ozone ◽  
Coupled Model ◽  
Earth System ◽  
Evaluation Tool ◽  
System Models ◽  
The Earth ◽  
Systematic Biases ◽  
And Performance ◽  
Earth System Models

Abstract. A community diagnostics and performance metrics tool for the evaluation of Earth System Models (ESMs) has been developed that allows for routine comparison of single or multiple models, either against predecessor versions or against observations. The priority of the effort so far has been to target specific scientific themes focusing on selected Essential Climate Variables (ECVs), a range of known systematic biases common to ESMs, such as coupled tropical climate variability, monsoons, Southern Ocean processes, continental dry biases and soil hydrology-climate interactions, as well as atmospheric CO2 budgets, tropospheric and stratospheric ozone, and tropospheric aerosols. The tool is being developed in such a way that additional analyses can easily be added. A set of standard namelists for each scientific topic reproduces specific sets of diagnostics or performance metrics that have demonstrated their importance in ESM evaluation in the peer-reviewed literature. The Earth System Model Evaluation Tool (ESMValTool) is a community effort open to both users and developers encouraging open exchange of diagnostic source code and evaluation results from the CMIP ensemble. This will facilitate and improve ESM evaluation beyond the state-of-the-art and aims at supporting such activities within the Coupled Model Intercomparison Project (CMIP) and at individual modelling centres. Ultimately, we envisage running the ESMValTool alongside the Earth System Grid Federation (ESGF) as part of a more routine evaluation of CMIP model simulations while utilizing observations available in standard formats (obs4MIPs) or provided by the user.

scholarly journals The seasonal cycle of <i>p</i>CO<sub>2</sub> and CO<sub>2</sub> fluxes in the Southern Ocean: diagnosing anomalies in CMIP5 Earth system models

2018 ◽  
Vol 15 (9) ◽  
pp. 2851-2872 ◽  
Author(s):  
N. Precious Mongwe ◽  
Marcello Vichi ◽  
Pedro M. S. Monteiro
Keyword(s):  
Southern Ocean ◽  
Seasonal Cycle ◽  
Dissolved Inorganic Carbon ◽  
Coupled Model ◽  
Dominant Mode ◽  
Cmip5 Models ◽  
Earth System ◽  
System Models ◽  
Rates Of Change ◽  
Earth System Models

Abstract. The Southern Ocean forms an important component of the Earth system as a major sink of CO2 and heat. Recent studies based on the Coupled Model Intercomparison Project version 5 (CMIP5) Earth system models (ESMs) show that CMIP5 models disagree on the phasing of the seasonal cycle of the CO2 flux (FCO2) and compare poorly with available observation products for the Southern Ocean. Because the seasonal cycle is the dominant mode of CO2 variability in the Southern Ocean, its simulation is a rigorous test for models and their long-term projections. Here we examine the competing roles of temperature and dissolved inorganic carbon (DIC) as drivers of the seasonal cycle of pCO2 in the Southern Ocean to explain the mechanistic basis for the seasonal biases in CMIP5 models. We find that despite significant differences in the spatial characteristics of the mean annual fluxes, the intra-model homogeneity in the seasonal cycle of FCO2 is greater than observational products. FCO2 biases in CMIP5 models can be grouped into two main categories, i.e., group-SST and group-DIC. Group-SST models show an exaggeration of the seasonal rates of change of sea surface temperature (SST) in autumn and spring during the cooling and warming peaks. These higher-than-observed rates of change of SST tip the control of the seasonal cycle of pCO2 and FCO2 towards SST and result in a divergence between the observed and modeled seasonal cycles, particularly in the Sub-Antarctic Zone. While almost all analyzed models (9 out of 10) show these SST-driven biases, 3 out of 10 (namely NorESM1-ME, HadGEM-ES and MPI-ESM, collectively the group-DIC models) compensate for the solubility bias because of their overly exaggerated primary production, such that biologically driven DIC changes mainly regulate the seasonal cycle of FCO2.

scholarly journals ESMValTool (v1.0) – a community diagnostic and performance metrics tool for routine evaluation of Earth system models in CMIP

2016 ◽  
Vol 9 (5) ◽  
pp. 1747-1802 ◽  
Author(s):  
Veronika Eyring ◽  
Mattia Righi ◽  
Axel Lauer ◽  
Martin Evaldsson ◽  
Sabrina Wenzel ◽  
...  
Keyword(s):  
Performance Metrics ◽  
Stratospheric Ozone ◽  
Coupled Model ◽  
Earth System ◽  
Evaluation Tool ◽  
System Models ◽  
The Earth ◽  
Systematic Biases ◽  
And Performance ◽  
Earth System Models

Abstract. A community diagnostics and performance metrics tool for the evaluation of Earth system models (ESMs) has been developed that allows for routine comparison of single or multiple models, either against predecessor versions or against observations. The priority of the effort so far has been to target specific scientific themes focusing on selected essential climate variables (ECVs), a range of known systematic biases common to ESMs, such as coupled tropical climate variability, monsoons, Southern Ocean processes, continental dry biases, and soil hydrology–climate interactions, as well as atmospheric CO2 budgets, tropospheric and stratospheric ozone, and tropospheric aerosols. The tool is being developed in such a way that additional analyses can easily be added. A set of standard namelists for each scientific topic reproduces specific sets of diagnostics or performance metrics that have demonstrated their importance in ESM evaluation in the peer-reviewed literature. The Earth System Model Evaluation Tool (ESMValTool) is a community effort open to both users and developers encouraging open exchange of diagnostic source code and evaluation results from the Coupled Model Intercomparison Project (CMIP) ensemble. This will facilitate and improve ESM evaluation beyond the state-of-the-art and aims at supporting such activities within CMIP and at individual modelling centres. Ultimately, we envisage running the ESMValTool alongside the Earth System Grid Federation (ESGF) as part of a more routine evaluation of CMIP model simulations while utilizing observations available in standard formats (obs4MIPs) or provided by the user.

scholarly journals Developing a common, flexible and efficient framework for weakly coupled ensemble data assimilation based on C-Coupler2.0

2021 ◽  
Vol 14 (5) ◽  
pp. 2635-2657
Author(s):  
Chao Sun ◽  
Li Liu ◽  
Ruizhe Li ◽  
Xinzhu Yu ◽  
Hao Yu ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Data Exchange ◽  
Coupled Model ◽  
Earth System ◽  
Model Ensemble ◽  
Coupled Models ◽  
Weakly Coupled ◽  
Abstract Data ◽  
Global Communications ◽  
Earth System Models

Abstract. Data assimilation (DA) provides initial states of model runs by combining observational information and models. Ensemble-based DA methods that depend on the ensemble run of a model have been widely used. In response to the development of seamless prediction based on coupled models or even Earth system models, coupled DA is now in the mainstream of DA development. In this paper, we focus on the technical challenges in developing a coupled ensemble DA system, especially how to conveniently achieve efficient interaction between the ensemble of the coupled model and the DA methods. We first propose a new DA framework, DAFCC1 (Data Assimilation Framework based on C-Coupler2.0, version 1), for weakly coupled ensemble DA, which enables users to conveniently integrate a DA method into a model as a procedure that can be directly called by the model ensemble. DAFCC1 automatically and efficiently handles data exchanges between the model ensemble members and the DA method without global communications and does not require users to develop extra code for implementing the data exchange functionality. Based on DAFCC1, we then develop an example weakly coupled ensemble DA system by combining an ensemble DA system and a regional atmosphere–ocean–wave coupled model. This example DA system and our evaluations demonstrate the correctness of DAFCC1 in developing a weakly coupled ensemble DA system and the effectiveness in accelerating an offline DA system that uses disk files as the interfaces for the data exchange functionality.

Southern Ocean Circulation and Eddy Compensation in CMIP5 Models

2013 ◽  
Vol 26 (18) ◽  
pp. 7198-7220 ◽  
Author(s):  
Stephanie M. Downes ◽  
Andrew McC. Hogg
Keyword(s):  
Southern Ocean ◽  
Wind Stress ◽  
Surface Wind ◽  
Surface Heat ◽  
Meridional Overturning Circulation ◽  
Cmip5 Models ◽  
Strong Increase ◽  
Coupled Models ◽  
Overturning Circulation ◽  
Meridional Overturning

Abstract Thirteen state-of-the-art climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are used to evaluate the response of the Antarctic Circumpolar Current (ACC) transport and Southern Ocean meridional overturning circulation to surface wind stress and buoyancy changes. Understanding how these flows—fundamental players in the global distribution of heat, gases, and nutrients—respond to climate change is currently a widely debated issue among oceanographers. Here, the authors analyze the circulation responses of these coarse-resolution coupled models to surface fluxes. Under a future CMIP5 climate pathway where the equivalent atmospheric CO2 reaches 1370 ppm by 2100, the models robustly project reduced Southern Ocean density in the upper 2000 m accompanied by strengthened stratification. Despite an overall increase in overlying wind stress (~20%), the projected ACC transports lie within ±15% of their historical state, and no significant relationship with changes in the magnitude or position of the wind stress is identified. The models indicate that a weakening of ACC transport at the end of the twenty-first century is correlated with a strong increase in the surface heat and freshwater fluxes in the ACC region. In contrast, the surface heat gain across the ACC region and the wind-driven surface transports are significantly correlated with an increased upper and decreased lower Eulerian-mean meridional overturning circulation. The change in the eddy-induced overturning in both the depth and density spaces is quantified, and it is found that the CMIP5 models project partial eddy compensation of the upper and lower overturning cells.

scholarly journals Diagnosing Relationships between Mean State Biases and El Niño Shortwave Feedback in CMIP5 Models

2018 ◽  
Vol 31 (4) ◽  
pp. 1315-1335 ◽  
Author(s):  
Samantha Ferrett ◽  
Matthew Collins ◽  
Hong-Li Ren
Keyword(s):  
El Niño ◽  
El Nino ◽  
Coupled Model ◽  
Heat Fluxes ◽  
Cmip5 Models ◽  
Coupled Models ◽  
El Niño Events ◽  
Mean State ◽  
Cloud Response ◽  
El Nino Events

The rate of damping of tropical Pacific sea surface temperature anomalies (SSTAs) associated with El Niño events by surface shortwave heat fluxes has significant biases in current coupled climate models [phase 5 of the Coupled Model Intercomparison Project (CMIP5)]. Of 33 CMIP5 models, 16 have shortwave feedbacks that are weakly negative in comparison to observations, or even positive, resulting in a tendency of amplification of SSTAs. Two biases in the cloud response to El Niño SSTAs are identified and linked to significant mean state biases in CMIP5 models. First, cool mean SST and reduced precipitation are linked to comparatively less cloud formation in the eastern equatorial Pacific during El Niño events, driven by a weakened atmospheric ascent response. Second, a spurious reduction of cloud driven by anomalous surface relative humidity during El Niño events is present in models with more stable eastern Pacific mean atmospheric conditions and more low cloud in the mean state. Both cloud response biases contribute to a weak negative shortwave feedback or a positive shortwave feedback that amplifies El Niño SSTAs. Differences between shortwave feedback in the coupled models and the corresponding atmosphere-only models (AMIP) are also linked to mean state differences, consistent with the biases found between different coupled models. Shortwave feedback bias can still persist in AMIP, as a result of persisting weak shortwave responses to anomalous cloud and weak cloud responses to atmospheric ascent. This indicates the importance of bias in the atmosphere component to coupled model feedback and mean state biases.

Model evaluation expectations of European ESM communities: results from a survey

2021 ◽  
Author(s):  
Jerome Servonnat ◽  
Eric Guilyardi ◽  
Zofia Stott ◽  
Kim Serradell ◽  
Axel Lauer ◽  
...  
Keyword(s):  
Model Evaluation ◽  
Common Ground ◽  
Performance Metrics ◽  
Coupled Model ◽  
System Modelling ◽  
Earth System ◽  
Evaluation Tool ◽  
Technical Standards ◽  
Community Effort ◽  
And Performance

&lt;p&gt;Developing an Earth system model evaluation tool for a broad user community is a real challenge, as the potential users do not necessarily have the same needs or expectations. While many evaluation tasks across user communities include common steps, significant differences are also apparent, not least the investment by institutions and individuals in bespoke tools. A key question is whether there is sufficient common ground to pursue a community tool with broad appeal and application.&lt;/p&gt;&lt;p&gt;We present the main results of a survey carried out by Assimila for the H2020 IS-ENES3 project to review the model evaluation needs of European Earth System Modelling communities. Interviewing approximately 30 participants among several European institutions, the survey targeted a broad range of users, including model developers, model users, evaluation data providers, and infrastructure providers. The output of the study provides an analysis of&amp;#160; requirements focusing on key technical, standards, and governance aspects.&lt;/p&gt;&lt;p&gt;The study used ESMValTool as a&amp;#160; current benchmark in terms of European evaluation tools. It is a community diagnostics and performance metrics tool for the evaluation of Earth System Models that allows for comparison of single or multiple models, either against predecessor versions or against observations. The tool is being developed in such a way that additional analyses can be added. As a community effort open to both users and developers, it encourages open exchange of diagnostic source code and evaluation results. It is currently used in Coupled Model Intercomparison Projects as well as for the development and testing of &amp;#8220;new&amp;#8221; models.&lt;/p&gt;&lt;p&gt;A key result of the survey is the widespread support for ESMValTool amongst users, developers, and even those who have taken or promote other approaches. The results of the survey identify priorities and opportunities in the further development of the ESMValTool to ensure long-term adoption of the tool by a broad community.&lt;/p&gt;

scholarly journals The Response of the Southern Ocean and Antarctic Sea Ice to Freshwater from Ice Shelves in an Earth System Model

2016 ◽  
Vol 29 (5) ◽  
pp. 1655-1672 ◽  
Author(s):  
Andrew G. Pauling ◽  
Cecilia M. Bitz ◽  
Inga J. Smith ◽  
Patricia J. Langhorne
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Coupled Model ◽  
Cmip5 Models ◽  
Freshwater Flux ◽  
Surface Mixed Layer ◽  
Surface Cooling ◽  
Ice Shelf ◽  
Mass Imbalance ◽  
Antarctic Sea Ice

ABSTRACT The possibility that recent Antarctic sea ice expansion resulted from an increase in freshwater reaching the Southern Ocean is investigated here. The freshwater flux from ice sheet and ice shelf mass imbalance is largely missing in models that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5). However, on average, precipitation minus evaporation (P − E) reaching the Southern Ocean has increased in CMIP5 models to a present value that is about greater than preindustrial times and 5–22 times larger than estimates of the mass imbalance of Antarctic ice sheets and shelves (119–544 ). Two sets of experiments were conducted from 1980 to 2013 in CESM1(CAM5), one of the CMIP5 models, artificially distributing freshwater either at the ocean surface to mimic iceberg melt or at the ice shelf fronts at depth. An anomalous reduction in vertical advection of heat into the surface mixed layer resulted in sea surface cooling at high southern latitudes and an associated increase in sea ice area. Enhancing the freshwater input by an amount within the range of estimates of the Antarctic mass imbalance did not have any significant effect on either sea ice area magnitude or trend. Freshwater enhancement of raised the total sea ice area by 1 × 106 km2, yet this and even an enhancement of was insufficient to offset the sea ice decline due to anthropogenic forcing for any period of 20 years or longer. Further, the sea ice response was found to be insensitive to the depth of freshwater injection.

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