Demonstrate coupled climate models at 20 km resolution
Overall Performance Measures
1st Quarter Metric - Completed
A simulation of the global ocean was developed and completed. The simulation was configured with a grid spacing of 11 km at the equator, decreasing to 4 km at high latitudes, in preparation for a high resolution atmosphere-ocean coupled simulation using the Community Earth System Model (CESM). Simulations were performed with the Parallel Ocean Program (POP), the current CESM ocean component.
In preparation for a fully coupled atmosphere-ocean high-resolution simulation using the CESM, the ocean component was prepared and tested in a number of high-resolution simulations. This effort is meant to devise the best possible configuration for the coupled simulation as well as the best ocean initial condition.
2nd Quarter Metric - Completed
A simulation of a high-resolution global atmospheric general circulation model configured for climate simulation purposes was developed and conducted. The model employed a spectral representation (a T341 spectral truncation) for integrating the governing equations forward in time using an alias-free transform grid of approximately 30 km. A semi-Lagrangian scheme was used for the accurate transport of water and other trace constituents (e.g., such as cloud condensate). The high-resolution configuration has been energetically-balanced for the ultra-high resolution T341 truncation. For purposes of an AMIP numerical integration the high-resolution atmosphere is configured to couple to an active land model with a quarter degree horizontal resolution. This atmosphere and land model configuration can also be coupled to 1/10 degree resolution ocean and sea ice components or to a simple Slab Ocean Model to allow simple exploratory investigations with an interactive ocean surface.
In preparation for a fully coupled atmosphere-ocean-land-sea ice high-resolution simulation using the CESM, the atmospheric component was prepared and tested in a number of high-resolution simulations. This effort was aimed at devising the best possible configuration for the coupled simulation as well as viable initial conditions for a high-resolution land surface component.
3rd Quarter Metric - Completed
We have developed a variable resolution capability for the Community Atmosphere Model (CAM), to use within the Community Earth System Model (CESM). This new capability allows CAM to perform simulations with selected regions of interest modeled with very high resolution (13.5 km average grid spacing in our simulations) while the rest of the globe is simulated at more typical (110 km) climate resolutions. At the Department of Energy (DOE) leadership class facilities, the CESM can be run at global 13.5 km resolution, but the computational cost of these runs is so high it is difficult to perform the hundreds of simulations needed to evaluate and calibrate the model. Variable resolution should provide an affordable way to perform these simulations, with the calibration being done in select regions at 13.5 km resolution. In the longer term, with the development of scale aware parameterizations, variable resolution will lead to an efficient regional climate modeling capability within the CESM.
In preparation for a fully coupled atmosphere-ocean high-resolution simulation using the CESM, we have developed a new variable resolution capability for CAM. A number of CESM simulations were performed to validate the approach, including a simulation with 13.5 km average grid spacing over most of the continental U.S. This will be the first configuration used in DOE’s atmospheric test-bed, which in turn will be used to both improve the simulation quality and quantify the uncertainties in the global 13.5 km configuration of CAM.
4th Quarter Metric - Completed
A series of simulations of the global climate system were performed using high resolution for all components using the Community Earth System Model (CESM). All of the runs were configured as follows:
- The ocean model (POP) employs a tripolar grid with a horizontal spacing of 11 km at the equator, decreasing to 4 km at high latitudes
- The sea ice model (CICE) uses the same grid as POP
- The atmosphere uses the spectral dynamical core (CAM-EU) at T341 resolution. Although this corresponds to colocation points with approximately 30 km resolution, the characteristics of the scheme make it similar to the finite volume dynamical core (CAM-FV) with finer spacing. For column physics, the CAM4 package is used
- The land model (CLM) employs the 1/8º CAM-FV grid, which has a resolution of slightly over 20 km
As is the standard procedure, the model has been run with pre-industrial conditions (e.g., 284.7 ppm of atmospheric CO2) in order to document the non-perturbed state of the system. At the time of this report, 40 years of simulated time have been completed. While this is not sufficient for true equilibrium of the full system, much can be learned from examining the solution. The remainder of this milestone will describe a few aspects of the model state as reflected by individual components, since an exhaustive detailing of the results is beyond the scope of the report.