Evaluation of the HOMME Dynamical Core in the Aquaplanet Configuration of NCAR CAM4: Rainfall

2011 ◽  
Vol 24 (15) ◽  
pp. 4037-4055 ◽  
Author(s):  
Saroj K. Mishra ◽  
Mark A. Taylor ◽  
Ramachandran D. Nair ◽  
Peter H. Lauritzen ◽  
Henry M. Tufo ◽  
...  
Keyword(s):  
Phase Speed ◽  
High Order ◽  
Climate System ◽  
Rainfall Simulation ◽  
Climate System Model ◽  
Dynamical Core ◽  
Model Version ◽  
High Order Element ◽  
Earth’S Climate ◽  
Cubed Sphere

Abstract The NCAR Community Climate System Model, version 4 (CCSM4), includes a new dynamical core option based on NCAR’s High-Order Method Modeling Environment (HOMME). HOMME is a petascale-capable high-order element-based conservative dynamical core developed on the cubed-sphere grid. Initial simulations have been completed in an aquaplanet configuration of the Community Atmosphere Model, version 4 (CAM4), the atmospheric component of CCSM4. The authors examined the results of this simulation and assessed its fidelity in simulating rainfall, which is one of the most important components of the earth’s climate system. For this they compared the results from two other dynamical cores of CAM4: the finite volume (FV) and Eulerian (EUL). Instantaneous features of rainfall in HOMME are similar to FV and EUL. Similar to EUL and FV, HOMME simulates a single-peak intertropical convergence zone (ITCZ) over the equator. The strength of the ITCZ is found to be almost the same in HOMME and EUL but more in FV. It is observed that in HOMME and EUL, there is higher surface evaporation, which supplies more moisture to the deep tropics and gives more rainfall over the ITCZ. The altitude of maximum precipitation is found to be at almost the same level in all three dynamical cores. The eastward propagation of rainfall bands is organized and more prominent in FV and HOMME than in EUL. The phase speed of the eastward propagation in HOMME is found to be higher than in FV. The results show that, in general, the rainfall simulated by HOMME falls in a regime between that of FV and EUL. Hence, they conclude that the key aspects of rainfall simulation with HOMME falls into an acceptable range, as compared to the existing dynamical cores used in the model.

scholarly journals Performance of the HOMME dynamical core in the aqua-planet configuration of NCAR CAM4: equatorial waves

2011 ◽  
Vol 29 (2) ◽  
pp. 221-227 ◽  
Author(s):  
S. K. Mishra ◽  
M. A. Taylor ◽  
R. D. Nair ◽  
H. M. Tufo ◽  
J. J. Tribbia
Keyword(s):  
Gravity Waves ◽  
Large Scale ◽  
Phase Speed ◽  
High Order ◽  
Equatorial Waves ◽  
Climate System Model ◽  
Dynamical Core ◽  
Model Simulations ◽  
High Order Element ◽  
Cubed Sphere

Abstract. A new atmospheric dynamical core, named the High Order Method Modeling Environment (HOMME), has been recently included in the NCAR-Community Climate System Model version 4 (CCSM4). It is a petascale capable high-order element-based conservative dynamical core developed on a cubed-sphere grid. We have examined the model simulations with HOMME using the aqua-planet mode of CAM4 (atmospheric component of CCSM4) and evaluated its performance in simulating the equatorial waves, considered a crucial element of climate variability. For this we compared the results with two other established models in CAM4 framework, which are the finite-volume (FV) and Eulerian spectral (EUL) dynamical cores. Although the gross features seem to be comparable, important differences have been found among the three dynamical cores. The phase speed of Kelvin waves in HOMME is faster and more satisfactory than those in FV and EUL. The higher phase speed is attributed to an increased large-scale precipitation in the upper troposphere and a more top-heavy heating structure. The variance of the n=1 equatorial Rossby waves is underestimated by all three of them, but comparatively HOMME simulations are more reasonable. For the n=0 eastward inertio-gravity waves, the variances are weak and phase speeds are too slow, scaled to shallow equivalent depths. However, the variance in HOMME is relatively more compared to the two other dynamical cores. The mixed Rossby-gravity waves are feeble in all the three cases. In summary, model simulations using HOMME are reasonably good, with some improvement relative to FV and EUL in capturing some of the important characteristics associated with equatorial waves.

Origin of Pacific Multidecadal Variability in Community Climate System Model, Version 3 (CCSM3): A Combined Statistical and Dynamical Assessment

2008 ◽  
Vol 21 (1) ◽  
pp. 114-133 ◽  
Author(s):  
Yafang Zhong ◽  
Zhengyu Liu ◽  
R. Jacob
Keyword(s):  
North Pacific ◽  
Climate System ◽  
System Model ◽  
Community Climate System Model ◽  
Climate System Model ◽  
Multidecadal Variability ◽  
Model Version ◽  
The North ◽  
The North Pacific ◽  
Community Climate

Abstract Observations indicate that Pacific multidecadal variability (PMV) is a basinwide phenomenon with robust tropical–extratropical linkage, though its genesis remains the topic of much debate. In this study, the PMV in the Community Climate System Model, version 3 (CCSM3) is investigated with a combined statistical and dynamical approach. In agreement with observations, the modeled North Pacific climate system undergoes coherent multidecadal atmospheric and oceanic variability of a characteristic quasi-50-yr time scale, with apparent connections to the tropical Indo-Pacific. The statistical assessment based on the CCSM3 control integration cannot exclusively identify the origin of the modeled multidecadal linkage, while confirming the two-way interactions between the tropical and extratropical Pacific. Two sensitivity experiments are performed to further investigate the origin of the PMV. With the atmosphere decoupled from the tropical ocean, multidecadal variability in the North Pacific climate remains outstanding. In contrast, without midlatitude oceanic feedback to atmosphere, an experiment shows much reduced multidecadal power in both extratropical atmosphere and surface ocean; moreover, the tropical multidecadal variability seen in the CCSM3 control run virtually disappears. The combined statistical and dynamical assessment supports a midlatitude coupled origin for the PMV, which can be described as follows: extratropical large-scale air–sea interaction gives rise to multidecadal variability in the North Pacific region; this extratropical signal then imprints itself in the tropical Indo–Pacific climate system, through a robust tropical–extratropical teleconnection. This study highlights a midlatitude origin of multidecadal tropical–extratropical linkage in the Pacific in the CCSM3.

scholarly journals Simulating the Biogeochemical and Biogeophysical Impacts of Transient Land Cover Change and Wood Harvest in the Community Climate System Model (CCSM4) from 1850 to 2100

2012 ◽  
Vol 25 (9) ◽  
pp. 3071-3095 ◽  
Author(s):  
Peter J. Lawrence ◽  
Johannes J. Feddema ◽  
Gordon B. Bonan ◽  
Gerald A. Meehl ◽  
Brian C. O’Neill ◽  
...  
Keyword(s):  
Land Cover ◽  
Land Cover Change ◽  
Climate Impacts ◽  
Climate System ◽  
System Model ◽  
Community Climate System Model ◽  
Climate System Model ◽  
Model Version ◽  
Wood Harvest ◽  
Community Climate

To assess the climate impacts of historical and projected land cover change in the Community Climate System Model, version 4 (CCSM4), new time series of transient Community Land Model, version 4 (CLM4) plant functional type (PFT) and wood harvest parameters have been developed. The new parameters capture the dynamics of the Coupled Model Intercomparison Project phase 5 (CMIP5) land cover change and wood harvest trajectories for the historical period from 1850 to 2005 and for the four representative concentration pathway (RCP) scenarios from 2006 to 2100. Analysis of the biogeochemical impacts of land cover change in CCSM4 reveals that the model produced a historical cumulative land use flux of 127.7 PgC from 1850 to 2005, which is in general agreement with other global estimates of 156 PgC for the same period. The biogeophysical impacts of the transient land cover change parameters were cooling of the near-surface atmosphere over land by −0.1°C, through increased surface albedo and reduced shortwave radiation absorption. When combined with other transient climate forcings, the higher albedo from land cover change was counteracted by decreasing snow albedo from black carbon deposition and high-latitude warming. The future CCSM4 RCP simulations showed that the CLM4 transient PFT parameters can be used to represent a wide range of land cover change scenarios. In the reforestation scenario of RCP 4.5, CCSM4 simulated a drawdown of 67.3 PgC from the atmosphere into the terrestrial ecosystem and product pools. By contrast the RCP 8.5 scenario with deforestation and high wood harvest resulted in the release of 30.3 PgC currently stored in the ecosystem.

The Low-Resolution CCSM4

2012 ◽  
Vol 25 (12) ◽  
pp. 3993-4014 ◽  
Author(s):  
Christine A. Shields ◽  
David A. Bailey ◽  
Gokhan Danabasoglu ◽  
Markus Jochum ◽  
Jeffrey T. Kiehl ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Historical Record ◽  
Climate System ◽  
System Model ◽  
Computationally Efficient ◽  
Low Resolution ◽  
Sea Ice Extent ◽  
Climate System Model ◽  
Dynamical Core ◽  
Horizontal Grid

Abstract The low-resolution version of the Community Climate System Model, version 4 (CCSM4) is a computationally efficient alternative to the intermediate and standard resolution versions of this fully coupled climate system model. It employs an atmospheric horizontal grid of 3.75° × 3.75° and 26 levels in the vertical with a spectral dynamical core (T31) and an oceanic horizontal grid that consists of a nominal 3° resolution with 60 levels in the vertical. This low-resolution version (T31x3) can be used for a variety of applications including long equilibrium simulations, development work, and sensitivity studies. The T31x3 model is validated for modern conditions by comparing to available observations. Significant problems exist for Northern Hemisphere Arctic locales where sea ice extent and thickness are excessive. This is partially due to low heat transport in T31x3, which translates into a globally averaged sea surface temperature (SST) bias of −1.54°C compared to observational estimates from the 1870–99 historical record and a bias of −1.26°C compared to observations from the 1986–2005 historical record. Maximum zonal wind stress magnitude in the Southern Hemisphere matches observational estimates over the ocean, although its placement is incorrectly displaced equatorward. Aspects of climate variability in T31x3 compare to observed variability, especially so for ENSO where the amplitude and period approximate observations. T31x3 surface temperature anomaly trends for the twentieth century also follow observations. An examination of the T31x3 model relative to the intermediate CCSM4 resolution (finite volume dynamical core 1.9° × 2.5°) for preindustrial conditions shows the T31x3 model approximates this solution for climate state and variability metrics examined here.

scholarly journals Transient simulations of the present and the last interglacial climate using the Community Climate System Model version 3: effects of orbital acceleration

2016 ◽  
Vol 9 (11) ◽  
pp. 3859-3873 ◽  
Author(s):  
Vidya Varma ◽  
Matthias Prange ◽  
Michael Schulz
Keyword(s):  
Climate System ◽  
System Model ◽  
Scale Model ◽  
Last Interglacial ◽  
Community Climate System Model ◽  
Climate System Model ◽  
Model Version ◽  
Surface Climate ◽  
Transient Simulations ◽  
Community Climate

Abstract. Numerical simulations provide a considerable aid in studying past climates. Out of the various approaches taken in designing numerical climate experiments, transient simulations have been found to be the most optimal when it comes to comparison with proxy data. However, multi-millennial or longer simulations using fully coupled general circulation models are computationally very expensive such that acceleration techniques are frequently applied. In this study, we compare the results from transient simulations of the present and the last interglacial with and without acceleration of the orbital forcing, using the comprehensive coupled climate model CCSM3 (Community Climate System Model version 3). Our study shows that in low-latitude regions, the simulation of long-term variations in interglacial surface climate is not significantly affected by the use of the acceleration technique (with an acceleration factor of 10) and hence, large-scale model–data comparison of surface variables is not hampered. However, in high-latitude regions where the surface climate has a direct connection to the deep ocean, e.g. in the Southern Ocean or the Nordic Seas, acceleration-induced biases in sea-surface temperature evolution may occur with potential influence on the dynamics of the overlying atmosphere.

scholarly journals Effect of a High-Order Filter on a Cubed-Sphere Spectral Element Dynamical Core

2018 ◽  
Vol 146 (7) ◽  
pp. 2047-2064 ◽  
Author(s):  
Hyun-Gyu Kang ◽  
Hyeong-Bin Cheong
Keyword(s):  
Baroclinic Instability ◽  
Spectral Element ◽  
High Order ◽  
Local Domain ◽  
Step Size ◽  
Time Step ◽  
Dynamical Core ◽  
Time Step Size ◽  
Order Filter ◽  
Cubed Sphere

Abstract A high-order filter for a cubed-sphere spectral element model was implemented in a three-dimensional spectral element dry hydrostatic dynamical core. The dynamical core incorporated hybrid sigma–pressure vertical coordinates and a third-order Runge–Kutta time-differencing method. The global high-order filter and the local-domain high-order filter, requiring numerical operation with a huge sparse global matrix and a locally assembled matrix, respectively, were applied to the prognostic variables, except for surface pressure, at every time step. Performance of the high-order filter was evaluated using the baroclinic instability test and quiescent atmosphere with underlying topography test presented by the Dynamical Core Model Intercomparison Project. It was revealed that both the global and local-domain high-order filters could better control the numerical noise in the noisy circumstances than the explicit diffusion, which is widely used for the spectral element dynamical core. Furthermore, by adopting the high-order filter, the effective resolution of the dynamical core could be increased, without weakening the stability of the dynamical core. Computational efficiency of the high-order filter was demonstrated in terms of both the time step size and the wall-clock time. Because of the nature of an implicit diffusion, the dynamical core employing this filter can take a larger time step size, compared to that using the explicit diffusion. The local-domain high-order filter was computationally more efficient than the global high-order filter, but less efficient than the explicit diffusion.

scholarly journals Seasonal Climate of the Tropical Atlantic Sector in the NCAR Community Climate System Model 3: Error Structure and Probable Causes of Errors

2007 ◽  
Vol 20 (6) ◽  
pp. 1053-1070 ◽  
Author(s):  
Ching-Yee Chang ◽  
James A. Carton ◽  
Semyon A. Grodsky ◽  
Sumant Nigam
Keyword(s):  
Climate Variability ◽  
Climate System ◽  
System Model ◽  
Boreal Summer ◽  
Community Climate System Model ◽  
Climate System Model ◽  
Boreal Spring ◽  
Model Version ◽  
Westerly Winds ◽  
Community Climate

Abstract The Community Climate System Model version 3 (CCSM3) has a dipolelike pattern with a cold bias in the northern Tropics and a warm bias in the southeastern Tropics, which is reminiscent of the observed pattern of climate variability in boreal spring. Along the equator, in contrast, in boreal spring CCSM3 exhibits striking westerly winds with easterly winds in the upper troposphere, in turn reminiscent of the observed pattern of climate variability in boreal summer. The westerly winds cause a deepening of the eastern thermocline that keeps the east warm despite enhanced coastal upwelling. Thus, the bias in the seasonal cycle of the coupled model appears to project at least partially onto the spatial patterns of natural climate variability in this sector. Information about the origin of the bias in CCSM3 is deduced from a comparison of CCSM3 with a simulation using specified historical SST to force the Community Atmospheric Model version 3 (CAM3). The patterns of bias in CAM3 resemble those apparent in CCSM3, including the appearance of substantially intensified subtropical bands of sea level pressure (SLP), indicating that the problem may be traced to difficulties in the atmospheric component model. Positive SLP bias also appears in the western tropical region, which may be related to deficient Amazonian precipitation. The positive SLP bias seems to be the cause of the anomalous westerly trade winds in boreal spring, and those in turn appear to be responsible for the anomalous deepening of the thermocline in the southeastern Tropics.

scholarly journals ENSO and Pacific Decadal Variability in the Community Climate System Model Version 4

2012 ◽  
Vol 25 (8) ◽  
pp. 2622-2651 ◽  
Author(s):  
Clara Deser ◽  
Adam S. Phillips ◽  
Robert A. Tomas ◽  
Yuko M. Okumura ◽  
Michael A. Alexander ◽  
...  
Keyword(s):  
Decadal Variability ◽  
El Nino ◽  
Climate System ◽  
System Model ◽  
Community Climate System Model ◽  
Climate System Model ◽  
Model Version ◽  
The North ◽  
Pacific Decadal Variability ◽  
Community Climate

Abstract This study presents an overview of the El Niño–Southern Oscillation (ENSO) phenomenon and Pacific decadal variability (PDV) simulated in a multicentury preindustrial control integration of the NCAR Community Climate System Model version 4 (CCSM4) at nominal 1° latitude–longitude resolution. Several aspects of ENSO are improved in CCSM4 compared to its predecessor CCSM3, including the lengthened period (3–6 yr), the larger range of amplitude and frequency of events, and the longer duration of La Niña compared to El Niño. However, the overall magnitude of ENSO in CCSM4 is overestimated by ~30%. The simulated ENSO exhibits characteristics consistent with the delayed/recharge oscillator paradigm, including correspondence between the lengthened period and increased latitudinal width of the anomalous equatorial zonal wind stress. Global seasonal atmospheric teleconnections with accompanying impacts on precipitation and temperature are generally well simulated, although the wintertime deepening of the Aleutian low erroneously persists into spring. The vertical structure of the upper-ocean temperature response to ENSO in the north and south Pacific displays a realistic seasonal evolution, with notable asymmetries between warm and cold events. The model shows evidence of atmospheric circulation precursors over the North Pacific associated with the “seasonal footprinting mechanism,” similar to observations. Simulated PDV exhibits a significant spectral peak around 15 yr, with generally realistic spatial pattern and magnitude. However, PDV linkages between the tropics and extratropics are weaker than observed.

scholarly journals AMIP Simulation with the CAM4 Spectral Element Dynamical Core

2013 ◽  
Vol 26 (3) ◽  
pp. 689-709 ◽  
Author(s):  
K. J. Evans ◽  
P. H. Lauritzen ◽  
S. K. Mishra ◽  
R. B. Neale ◽  
M. A. Taylor ◽  
...  
Keyword(s):  
Spectral Element Method ◽  
Spectral Element ◽  
System Model ◽  
Energy Spectra ◽  
Model Intercomparison ◽  
Climate System Model ◽  
Dynamical Core ◽  
Intercomparison Project ◽  
Cubed Sphere ◽  
Mean Square Errors

Abstract The authors evaluate the climate produced by the Community Climate System Model, version 4, running with the new spectral element atmospheric dynamical core option. The spectral element method is configured to use a cubed-sphere grid, providing quasi-uniform resolution over the sphere and increased parallel scalability and removing the need for polar filters. It uses a fourth-order accurate spatial discretization that locally conserves mass and total energy. Using the Atmosphere Model Intercomparison Project protocol, the results from the spectral element dynamical core are compared with those produced by the default finite-volume dynamical core and with observations. Even though the two dynamical cores are quite different, their simulated climates are remarkably similar. When compared with observations, both models have strengths and weaknesses but have nearly identical root-mean-square errors and the largest biases show little sensitivity to the dynamical core. The spectral element core does an excellent job reproducing the atmospheric kinetic energy spectra, including fully capturing the observed Nastrom–Gage transition when running at 0.125° resolution.

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