CO2 increase experiments using the Community Earth System Model (CESM): Relationship to climate sensitivity and comparison of CESM1 to CESM2

2020 ◽  
Author(s):  
Julio T. Bacmeister ◽  
Cecile Hannay ◽  
Brian Medeiros ◽  
Andrew Gettelman ◽  
Richard Neale ◽  
...  
Keyword(s):  
Climate Sensitivity ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Community Earth System Model

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

2019 ◽  
Vol 46 (14) ◽  
pp. 8329-8337 ◽  
Author(s):  
A. Gettelman ◽  
C. Hannay ◽  
J. T. Bacmeister ◽  
R. B. Neale ◽  
A. G. Pendergrass ◽  
...  
Keyword(s):  
Climate Sensitivity ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Model Version ◽  
Community Earth System Model

Spatial Decomposition of Climate Feedbacks in the Community Earth System Model

2013 ◽  
Vol 26 (11) ◽  
pp. 3544-3561 ◽  
Author(s):  
A. Gettelman ◽  
J. E. Kay ◽  
J. T. Fasullo
Keyword(s):  
Climate Sensitivity ◽  
Earth System Model ◽  
Cloud Feedback ◽  
System Model ◽  
Storm Tracks ◽  
Cloud Base ◽  
Earth System ◽  
Cloud Feedbacks ◽  
Stratiform Clouds ◽  
Community Earth System Model

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.

scholarly journals Regional Climate Simulations With the Community Earth System Model

2018 ◽  
Vol 10 (6) ◽  
pp. 1245-1265 ◽  
Author(s):  
A. Gettelman ◽  
P. Callaghan ◽  
V. E. Larson ◽  
C. M. Zarzycki ◽  
J. T. Bacmeister ◽  
...  
Keyword(s):  
Regional Climate ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Climate Simulations ◽  
Community Earth System Model

scholarly journals Evaluating simplified chemical mechanisms within present-day simulations of the Community Earth System Model version 1.2 with CAM4 (CESM1.2 CAM-chem): MOZART-4 vs. Reduced Hydrocarbon vs. Super-Fast chemistry

2018 ◽  
Vol 11 (10) ◽  
pp. 4155-4174 ◽  
Author(s):  
Benjamin Brown-Steiner ◽  
Noelle E. Selin ◽  
Ronald Prinn ◽  
Simone Tilmes ◽  
Louisa Emmons ◽  
...  
Keyword(s):  
Computational Cost ◽  
Earth System Model ◽  
Chemical Mechanism ◽  
System Model ◽  
Earth System ◽  
Chemical Mechanisms ◽  
Trade Offs ◽  
Community Earth System Model ◽  
Time Periods ◽  
Fast Mechanism

Abstract. While state-of-the-art complex chemical mechanisms expand our understanding of atmospheric chemistry, their sheer size and computational requirements often limit simulations to short lengths or ensembles to only a few members. Here we present and compare three 25-year present-day offline simulations with chemical mechanisms of different levels of complexity using the Community Earth System Model (CESM) Version 1.2 CAM-chem (CAM4): the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) mechanism, the Reduced Hydrocarbon mechanism, and the Super-Fast mechanism. We show that, for most regions and time periods, differences in simulated ozone chemistry between these three mechanisms are smaller than the model–observation differences themselves. The MOZART-4 mechanism and the Reduced Hydrocarbon are in close agreement in their representation of ozone throughout the troposphere during all time periods (annual, seasonal, and diurnal). While the Super-Fast mechanism tends to have higher simulated ozone variability and differs from the MOZART-4 mechanism over regions of high biogenic emissions, it is surprisingly capable of simulating ozone adequately given its simplicity. We explore the trade-offs between chemical mechanism complexity and computational cost by identifying regions where the simpler mechanisms are comparable to the MOZART-4 mechanism and regions where they are not. The Super-Fast mechanism is 3 times as fast as the MOZART-4 mechanism, which allows for longer simulations or ensembles with more members that may not be feasible with the MOZART-4 mechanism given limited computational resources.

scholarly journals Development of hybrid 3-D hydrological modeling for the NCAR Community Earth System Model (CESM)

2015 ◽  
Author(s):  
Xubin Zeng ◽  
◽  
Peter Troch ◽  
Jon Pelletier ◽  
Guo-Yue Niu ◽  
...  
Keyword(s):  
Hydrological Modeling ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Community Earth System Model
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