What's New in CESM1.2.0 - Science
The CESM1.2 release has numerous new key features among which are the addition of CLM4.5, new science changes to CAM5 running with the CAM-SE dynamical core, and new scripting infrastructure for the generation of component sets, grids and model testing.
Additional information regarding these updates is also available in the CESM User's Guide and in the individual model component documentation.
CAM5.3 includes modifications and updates for the spectral element dynamical (SE) core. These include a change from an Eulerian to a Lagrangian calculation for vertical advection. The updated version of the Morrison Gettelman microphysics is now available (MG1.5) with fixes for droplet activation and a major code refactoring. The ability to run a prescribed version of the Modal Aerosol Modal (MAM3) is also available. Finally the capability to significantly reduce default history file size, retaining only those fields needed for the AMWG diagnostics, is included.
The new features available in CAM-Chem in this release include:
- coupling of tropospheric and stratospheric chemistry with the CAM5 modal aerosol model 3 and 7
- expansion of the representation of secondary-organic aerosols
- implementation of MEGAN v2 in CLM, including a flexible framework for assigning MEGAN emissions to species represented in the chemistry.
All these are released to give users access to these new capabilities. Only limited evaluation has been performed.
Functional updates for WACCM include:
- New compsets for WACCM4 with CARMA sectional microphysics code for aerosols:
- BNUKE_C4WBC_L40CN - Stratospheric black carbon for nuclear winter studies (RCP4.5, functional)
- FGEOS_C4WSF_L40CN - Stratospheric sulfate coupled to heterogenous chemistry, nudged by specified dynamics (SD-WACCM, functional)
- WACCM spectral element (SE) dycore support (functional)
- Updates and bug fixes for specified chemistry (SC-WACCM, functional)
- ozone file fixed
- Updates for specified dynamics (SD-WACCM and SD-CAMchem, functional)
- SSI/TSI and Kp files updated for 2012
- SPE and SAD file updates for 2012 to be created
- new namelist specification for nudging factor (time scale, rather than percent)
- WACCM5 updates and bug fixes (functional)
- Chemistry updates in waccm_mozart (functional)
- Removed obsolete waccm_mozart_v1 chemistry package
- New version of Glimmer-CISM (version 1.9). This version includes extensive modifications that have been made in preparation for the upcoming release of Glimmer-CISM version 2.0, which will include 3d, 1st-order-accurate ice dynamics and support for MPI-based distributed parallelism. When run with shallow-ice dynamics, Glimmer-CISM 1.9 gives answers that are approximately the same as version 1.6, which was the version included in CESM1.1.1 and earlier.
- New default parameter values (temp_init, basal_mass_balance, and sigma)
- New initial conditions have been provided for both CLM and CISM, when running the BG1850CN compset at f09 resolution. For the first time, this includes spun-up ice sheet initial conditions.
- Option to run with 36 elevation classes (200m each)
- The GLC_GRID xml variable has been renamed to CISM_GRID
For more details on the changes made in CESM1.2.0, see the "What's new in CESM1.2.0" section of the CISM documentation.
CLM4.5 incorporates a broad set of changes throughout the model including a revised photosynthesis scheme, improved cold region hydrology and optional VIC-based hydrology, prognostic wetland distribution, a new snow cover fraction parameterization, a new lake model, new crop model features such as fertilization and grain fill, and multiple urban classes. Biogeochemistry changes include the introduction of a Century-like vertically resolved soil biogeochemistry scheme with revised denitrification and biological fixation processes as well as a methane emissions model, a revised fire model including anthropogenic triggers and suppression, and 13C and 14C isotope fractionation.
Important Note - CLM4.5 has been evaluated for "CLM offline mode" (I compsets), but has NOT been evaluated or scientifically validated when coupled to the other models.
- DATM -- Add support for using CRUNCEP forcing for CLM.
Updates to the POP ocean model include:
- Support for new decompositions (no longer limited to pop_decomp.xml)
- Improved communication in overflow module (replacing global reductions with local messages)
- Significant updates to the ocean ecosystem
- Bugfix: the diagnostic variable RHO_VINT was being computed incorrectly.
- added support for multi-instance runs
- added functionality to set simyr and finidat_rtm files
- added r05 resolution for 1850/2000
- now use SLOPE and MAX_VOLR in r05 direction files
- introduced initial condition files for 1850/2000
- sending VOLR as diagnostic field to CLM (also effects TWS)
- introduced rtm_active and flood_active controls
- added rtm_effvel velocity to be backward compatible with clm4_0_* tags
- added RTMTHRESH and RTMFLOOD to history output
CESM1.2.0 introduces a new WAV model to CESM with initial support of just the stub and dead versions for this release.