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CCSM Research Tools: CAM 3.1 Release Notes

CAM-3.1 is mainly a software engineering release. It reproduces the CAM-3.0 climate in configurations for which control simulations were provided. In those configurations, each code change between versions 3.0 and 3.1 either produces identical results, or introduces roundoff level changes as validated by the perturbation growth test. It is important to note however that CAM-3.1 will not pass the perturbation growth test compared to CAM-3.0. That is because perturbation growth tests are done using the aqua-planet configuration, and there were non-roundoff level changes in the aqua-planet configuration.

Due to a severe staffing shortage, we have not been able to provide updated documentation with this release. The main reason for the release is to provide parameterization developers with code that contains updated physics interfaces in the context of a model with a validated climate. The development path from here will change the model's climate as we begin to address the current biases and improve the representations of physical processes.

New Science Features

  • Add flexibility to where state is written to initial files.
  • Allow radiation calculations to be done every timestep for fixed number of steps at startup.
  • Add column radiation model (CRM) and improvements to the single column model (SCAM).
  • Allow CAM to use 30 second topographic variance field.
  • Add FV offline driver.
  • Add diagnostic fields required for energy and water budgets./li>
  • Upgrade physics interfaces to deep and shallow convection, stratiform clouds, wet deposition, vertical diffusion and radiation.
  • Add interface between radiation and constituents.
  • Isolate extended grid needed by SLT to SLT code.
  • Refactor vertical diffusion module.
  • Unify code for writing initial and history files.
  • Physics buffer optimization (only allocate physpkg scope buffers once).
  • Use separate files for surface topography (was in initial files). Backwards compatibility with old initial files maintained.
  • SPMD optimizations and extensions for CRAY/NEC.
  • Add compiler directives for Cray X1 optimization.
  • Changes to support IA64 cluster.

Bug Fixes

  • Removed equivalence statements. This was causing problems for the intel compiler (really a compiler bug, but equivalence should be removed anyway).
  • Remove addfld call for TAUVIS which is no longer used in model.
  • Remove date checking in history.F90 which was only valid for 365 day calendar.
  • Write correct value of calendar attribute to output netCDF files.
  • Fixes to allow FV w/ 2D decomp to run under lf95/debug.
  • Fix bug in date comparison in prescribed_aerosols.F90 (provided by Jim Boyle). /li>

Build Changes

  • Default optimization for pgf90 was reduced from -O2 to -O1.