High Climate Sensitivity in the Community Earth System Model Version 2 (CESM2)

Abstract An ensemble of simulations from different versions of the Community Atmosphere Model in the Community Earth System Model (CESM) is used to investigate the processes responsible for the intermodel spread in climate sensitivity. In the CESM simulations, the climate sensitivity spread is primarily explained by shortwave cloud feedbacks on the equatorward flank of the midlatitude storm tracks. Shortwave cloud feedbacks have been found to explain climate sensitivity spread in previous studies, but the location of feedback differences was in the subtropics rather than in the storm tracks as identified in CESM. The cloud-feedback relationships are slightly stronger in the winter hemisphere. The spread in climate sensitivity in this study is related both to the cloud-base state and to the cloud feedbacks. Simulated climate sensitivity is correlated with cloud-fraction changes on the equatorward side of the storm tracks, cloud condensate in the storm tracks, and cloud microphysical state on the poleward side of the storm tracks. Changes in the extent and water content of stratiform clouds (that make up cloud feedback) are regulated by the base-state vertical velocity, humidity, and deep convective mass fluxes. Within the storm tracks, the cloud-base state affects the cloud response to CO2-induced temperature changes and alters the cloud feedbacks, contributing to climate sensitivity spread within the CESM ensemble.

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Review of A New End-to-End Workflow for the Community Earth System Model (version 2.0) for CMIP6

10.5194/gmd-2020-133-rc1 ◽

2020 ◽

Keyword(s):

Earth System Model ◽

System Model ◽

Earth System ◽

Model Version ◽

Community Earth System Model ◽

Version 2.0 ◽

End To End

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Analysis of Secondary Organic Aerosol Simulation Bias in the Community Earth System Model (CESM2.1)

10.5194/acp-2020-1182 ◽

2020 ◽

Author(s):

Yaman Liu ◽

Xinyi Dong ◽

Minghuai Wang ◽

Louisa K. Emmons ◽

Yawen Liu ◽

...

Keyword(s):

Climate Models ◽

Secondary Organic Aerosol ◽

Organic Aerosol ◽

The United States ◽

Earth System Model ◽

Basis Set ◽

System Model ◽

Earth System ◽

Model Version ◽

Community Earth System Model

Abstract. Organic aerosol (OA) has been considered as one of the most important uncertainties in climate modeling due to the complexity in presenting its chemical production and depletion mechanisms. To better understand the capability of climate models and probe into the associated uncertainties in simulating OA, we evaluate the Community Earth System Model version 2.1 (CESM2.1) configured with the Community Atmosphere Model version 6 (CAM6) with comprehensive tropospheric and stratospheric chemistry representation (CAM6-Chem), through a long-term simulation (1988–2019) with observations collected from multiple datasets in the United States. We find that CESM generally reproduces the inter-annual variation and seasonal cycle of OA mass concentration at surface layer with correlation of 0.40 as compared to ground observations, and systematically overestimates (69 %) in summer and underestimates (−19 %) in winter. Through a series of sensitivity simulations, we reveal that modeling bias is primarily related to the dominant fraction of monoterpene-formed secondary organic aerosol (SOA), and a strong positive correlation of 0.67 is found between monoterpene emission and modeling bias in eastern US during summer. In terms of vertical profile, the model prominently underestimates OA and monoterpene concentrations by 37–99 % and 82–99 % respectively in the upper air (> 500 m) as validated against aircraft observations. Our study suggests that the current Volatility Basis Set (VBS) scheme applied in CESM might be parameterized with too high monoterpene SOA yields which subsequently result in strong SOA production near emission source area. We also find that the model has difficulty in reproducing the decreasing trend of surface OA in southeast US, probably because of employing pure gas VBS to represent isoprene SOA which is in reality mainly formed through multiphase chemistry, thus the influence of aerosol acidity and sulfate particle change on isoprene SOA formation has not been fully considered in the model. This study reveals the urgent need to improve the SOA modeling in climate models.

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Supplementary material to "Investigating soil moisture-climate interactions with prescribed soil moisture experiments: an assessment with the Community Earth System Model (version 1.2)"

10.5194/gmd-2016-209-supplement ◽

2016 ◽

Author(s):

Mathias Hauser ◽

René Orth ◽

Sonia I. Seneviratne

Keyword(s):

Soil Moisture ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Model Version ◽

Climate Interactions ◽

Community Earth System Model ◽

Supplementary Material

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Simulation of LGM ice sheets with the Community Earth System Model version 2

10.5194/egusphere-egu21-15463 ◽

2021 ◽

Author(s):

Sarah L Bradley ◽

Michele Petrini ◽

Raymond Sellevold ◽

Miren Vizcaino ◽

William H. Lipscomb ◽

...

Keyword(s):

Ice Sheets ◽

Ice Sheet ◽

Earth System Model ◽

System Model ◽

Earth System ◽

Last Deglaciation ◽

Model Version ◽

Starting Point ◽

Community Earth System Model ◽

The Last Deglaciation

The last deglaciation provides as unique a framework to investigate the processes of ice sheet and climate interaction during periods of mass loss as in the current climate. Here we simulate the Last Glacial Maximum (LGM) northern hemisphere ice sheets climate, surface mass balance (SMB), and dynamics with the Community Earth System Model version 2 (CESM2, Danabasoglu et al., 2020)) and the Community Ice Sheet Model version 2 (CISM2, Lipscomb et al., 2019). This LGM simulation will be later used as starting point for coupled CESM2-CISM2 simulations of the last deglaciation.&#160;CESM2 is run at the nominal resolution used for IPCC-type projections (approx. 1 degree for all components). The model includes an advanced snow/firn and SMB calculation (van Kampenhout et al, 2019; Sellevold et al, 2019) the land component (CLM, cite) that has been evaluated and applied to the simulation of the future Greenland melt (van Kampenhout et al, 2020, Muntjewerf et al., 2020a,b, Sellevold & Vizcaino, 2020).&#160;Our analysis examines how the global, Arctic, and North Atlantic climate result in the simulated radiative and turbulent heat fluxes over the ice sheets, and the mass fluxes from precipitation, refreezing, runoff, and sublimation. We also examine the simulated ice streams in CISM2, which is run at 8 km under a higher-order approximation for ice flow.

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