scholarly journals A spectral transform dynamical core option within the Community Atmosphere Model (CAM4)

2014 ◽  
Vol 6 (3) ◽  
pp. 902-922 ◽  
Author(s):  
Katherine J. Evans ◽  
Salil Mahajan ◽  
Marcia Branstetter ◽  
Julie L. McClean ◽  
Julie Caron ◽  
...  
Keyword(s):  
Dynamical Core ◽  
Community Atmosphere Model ◽  
Spectral Transform ◽  
Atmosphere Model

scholarly journals Downscale cascades in tracer transport test cases: an intercomparison of the dynamical cores in the Community Atmosphere Model CAM5

2012 ◽  
Vol 5 (3) ◽  
pp. 1781-1816 ◽  
Author(s):  
J. Kent ◽  
C. Jablonowski ◽  
J. P. Whitehead ◽  
R. B. Rood
Keyword(s):  
Climate Models ◽  
Western Hemisphere ◽  
Test Cases ◽  
Tracer Transport ◽  
Model Version ◽  
Eastern Hemisphere ◽  
Community Atmosphere Model ◽  
Advection Schemes ◽  
Spectral Transform ◽  
Atmosphere Model

Abstract. The accurate modelling of cascades to unresolved scales is an important part of the tracer transport component of dynamical cores of weather and climate models. This paper aims to investigate the ability of the advection schemes in the National Center for Atmospheric Research's Community Atmosphere Model version 5 (CAM5) to model this cascade. In order to quantify the effects of the different advection schemes in CAM5, four two-dimensional tracer transport test cases are presented. Three of the tests stretch the tracer below the scale of coarse resolution grids to ensure the downscale cascade of tracer variance. These results are compared with a high resolution reference solution, which is simulated on a resolution fine enough to resolve the tracer during the test. The fourth test has two separate flow cells, and is designed so that any tracer in the Western Hemisphere should not pass into the Eastern Hemisphere. This is to test whether the diffusion in transport schemes, often in the form of explicit hyper-diffusion terms or implicit through monotonic limiters, contains unphysical mixing. An intercomparison of three of the dynamical cores of the National Center for Atmospheric Research's Community Atmosphere Model version 5 is performed. The results show that the finite-volume (CAM-FV) and spectral element (CAM-SE) dynamical cores model the downscale cascade of tracer variance better than the semi-Lagrangian transport scheme of the Eulerian spectral transform core (CAM-EUL). Each scheme tested produces unphysical mass in the Eastern Hemisphere of the separate cells test.

The Mean Climate of the Community Atmosphere Model (CAM4) in Forced SST and Fully Coupled Experiments

2013 ◽  
Vol 26 (14) ◽  
pp. 5150-5168 ◽  
Author(s):  
Richard B. Neale ◽  
Jadwiga Richter ◽  
Sungsu Park ◽  
Peter H. Lauritzen ◽  
Stephen J. Vavrus ◽  
...  
Keyword(s):  
Freeze Drying ◽  
Regional Climate ◽  
Cloud Fraction ◽  
Trade Wind ◽  
Dynamical Core ◽  
Model Version ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Mean Climate ◽  
Fully Coupled

Abstract The Community Atmosphere Model, version 4 (CAM4), was released as part of the Community Climate System Model, version 4 (CCSM4). The finite volume (FV) dynamical core is now the default because of its superior transport and conservation properties. Deep convection parameterization changes include a dilute plume calculation of convective available potential energy (CAPE) and the introduction of convective momentum transport (CMT). An additional cloud fraction calculation is now performed following macrophysical state updates to provide improved thermodynamic consistency. A freeze-drying modification is further made to the cloud fraction calculation in very dry environments (e.g., the Arctic), where cloud fraction and cloud water values were often inconsistent in CAM3. In CAM4 the FV dynamical core further degrades the excessive trade-wind simulation, but reduces zonal stress errors at higher latitudes. Plume dilution alleviates much of the midtropospheric tropical dry biases and reduces the persistent monsoon precipitation biases over the Arabian Peninsula and the southern Indian Ocean. CMT reduces much of the excessive trade-wind biases in eastern ocean basins. CAM4 shows a global reduction in cloud fraction compared to CAM3, primarily as a result of the freeze-drying and improved cloud fraction equilibrium modifications. Regional climate feature improvements include the propagation of stationary waves from the Pacific into midlatitudes and the seasonal frequency of Northern Hemisphere blocking events. A 1° versus 2° horizontal resolution of the FV dynamical core exhibits superior improvements in regional climate features of precipitation and surface stress. Improvements in the fully coupled mean climate between CAM3 and CAM4 are also more substantial than in forced sea surface temperature (SST) simulations.

scholarly journals CAM-SE: A scalable spectral element dynamical core for the Community Atmosphere Model

2011 ◽  
Vol 26 (1) ◽  
pp. 74-89 ◽  
Author(s):  
John M. Dennis ◽  
Jim Edwards ◽  
Katherine J. Evans ◽  
Oksana Guba ◽  
Peter H. Lauritzen ◽  
...  
Keyword(s):  
Spectral Element ◽  
Dynamical Core ◽  
Community Atmosphere Model ◽  
Atmosphere Model

scholarly journals Downscale cascades in tracer transport test cases: an intercomparison of the dynamical cores in the Community Atmosphere Model CAM5

2012 ◽  
Vol 5 (6) ◽  
pp. 1517-1530 ◽  
Author(s):  
J. Kent ◽  
C. Jablonowski ◽  
J. P. Whitehead ◽  
R. B. Rood
Keyword(s):  
Climate Models ◽  
Western Hemisphere ◽  
Test Cases ◽  
Tracer Transport ◽  
Model Version ◽  
Eastern Hemisphere ◽  
Community Atmosphere Model ◽  
Advection Schemes ◽  
Spectral Transform ◽  
Atmosphere Model

Abstract. The accurate modeling of cascades to unresolved scales is an important part of the tracer transport component of dynamical cores of weather and climate models. This paper aims to investigate the ability of the advection schemes in the National Center for Atmospheric Research's Community Atmosphere Model version 5 (CAM5) to model this cascade. In order to quantify the effects of the different advection schemes in CAM5, four two-dimensional tracer transport test cases are presented. Three of the tests stretch the tracer below the scale of coarse resolution grids to ensure the downscale cascade of tracer variance. These results are compared with a high resolution reference solution, which is simulated on a resolution fine enough to resolve the tracer during the test. The fourth test has two separate flow cells, and is designed so that any tracer in the western hemisphere should not pass into the eastern hemisphere. This is to test whether the diffusion in transport schemes, often in the form of explicit hyper-diffusion terms or implicit through monotonic limiters, contains unphysical mixing. An intercomparison of three of the dynamical cores of the National Center for Atmospheric Research's Community Atmosphere Model version 5 is performed. The results show that the finite-volume (CAM-FV) and spectral element (CAM-SE) dynamical cores model the downscale cascade of tracer variance better than the semi-Lagrangian transport scheme of the Eulerian spectral transform core (CAM-EUL). Each scheme tested produces unphysical mass in the eastern hemisphere of the separate cells test.

scholarly journals Sensitivity of Simulated Climate to Two Atmospheric Models: Interpretation of Differences between Dry Models and Moist Models

2013 ◽  
Vol 141 (5) ◽  
pp. 1558-1576 ◽  
Author(s):  
He Zhang ◽  
Minghua Zhang ◽  
Qing-cun Zeng
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Atmospheric Physics ◽  
Dynamical Core ◽  
Community Atmosphere Model ◽  
Climate Simulations ◽  
Spectral Transform ◽  
Simulated Climate ◽  
The Tropics ◽  
Academy Of Sciences

Abstract The dynamical core of the Institute of Atmospheric Physics of the Chinese Academy of Sciences Atmospheric General Circulation Model (IAP AGCM) and the Eulerian spectral transform dynamical core of the Community Atmosphere Model, version 3.1 (CAM3.1), developed at the National Center for Atmospheric Research (NCAR) are used to study the sensitivity of simulated climate. The authors report that when the dynamical cores are used with the same CAM3.1 physical parameterizations of comparable resolutions, the model with the IAP dynamical core simulated a colder troposphere than that from the CAM3.1 core, reducing the CAM3.1 warm bias in the tropical and midlatitude troposphere. However, when the two dynamical cores are used in the idealized Held–Suarez tests without moisture physics, the IAP AGCM core simulated a warmer troposphere than that in CAM3.1. The causes of the differences in the full models and in the dry models are then investigated. The authors show that the IAP dynamical core simulated weaker eddies in both the full physics and the dry models than those in the CAM due to different numerical approximations. In the dry IAP model, the weaker eddies cause smaller heat loss from poleward dynamical transport and thus warmer troposphere in the tropics and midlatitudes. When moist physics is included, however, weaker eddies also lead to weaker transport of water vapor and reduction of high clouds in the IAP model, which then causes a colder troposphere due to reduced greenhouse warming of these clouds. These results show how interactive physical processes can change the effect of a dynamical core on climate simulations between two models.

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