CCSM2.0.1 POP Documentation
Documentation
CCSM POP FAQs
- What is CCSM2.0.1 POP?
- What grid resolutions are supported in CCSM POP?
- What are the differences between CCSM2.0 POP and CCSM2.0.1 POP?
The active ocean-model component of the Community Climate System Model (CCSM) is the CCSM2.0.1 Parallel Ocean Program (CCSM2.0.1 POP), which is based upon the Los Alamos National Laboratory's POP Version 1.4.3.
What grid resolutions are supported in CCSM POP?
The CCSM2 ocean and ice models must share a common horizontal grid. Presently, two different resolutions are officially supported in CCSM: gx1v3 and gx3v4. In both of these grids, the North Pole has been displaced into Greenland. The former is the finer of the two, with longitudinal resolution approximately one degree; its latitudinal resolution is variable, with finer resolution, approximately 0.3 degrees, near the equator. The latter is the coarser grid, with longitudinal resolution of 3.6 degrees; its latitudinal resolution is variable, with finer resolution, approximately 0.9 degrees, near the equator.
In the ocean model, there are 40 vertical levels associated with the gx1v3 resolution, with level thickness monotonically increasing from approximately 10 to 250 meters. In the ocean model, it is the combination of the horizontal grid, horizontal land mask, vertical grid, and bottom topography that collectively define the "gx1v3" resolution.
There are 25 vertical ocean-model levels associated with the gx3v4 resolution, with level thickness monotonically increasing from approximately 12 to 450 meters. The combination of the horizontal grid, horizontal land mask, vertical grid, and bottom topography is referred to collectively as the "gx3v4" resolution in the ocean model.
What are the differences between CCSM2.0 POP and CCSM2.0.1 POP?
The CCSM2.0.1 POP release is an increment on the CCSM2.0 release. The baseline control run is bit-for-bit exact in CCSM2.0.1 compared to the CCSM2.0 release, so that when the standard gx1v3_pop_in input file is used with the updated CCSM2.0.1 POP code, the CCSM2.0 POP solution is reproduced bit-for-bit. There have, however, been minor changes to the POP code, which have been released with CCSM2.0.1 POP. These changes are summarized below.
NOTE: There is a known error in the CCSM2.0.1 POP module, hmix_gm.F. The correction to this error is not included in the CCSM2.0.1 POP release, because this correction would produce solutions different from the CCSM2.0 Control Run. The corrected version of hmix_gm.F is provided as a software patch, which is available on the CCSM2.0.1 release page.
- Correct small errors:
- change the long-name description of z_w to correctly identify it as the depth from the surface to the top of the layer, not the bottom
- change coding in diag_bsf.F to eliminate division by zero in a merge statement. When compiled by the SGI compiler with traps set for division by zero, then run on the SGI, the ocean code dumped core because of this merge statement. The solution was to replace this statement with a where-block.
- change the long-name description of UVEL and VVEL in the tavg_contents and hist_contents files to improve the description and eliminate possibly confusing language
- Add copyright information
- Update documentation
- Eliminate the usage of a F95 feature from module types.F