All configuration options can be specified using command line arguments to configure and this is the recommended practice. Options specified via command line arguments take precedence over options specified any other way.
At the next level of precedence a few options can be specified by setting environment variables. And finally, at the lowest precedence, many options have hard-coded defaults. Most of these are located in the files $CAM_ROOT/models/atm/cam/bld/config_files/defaults_*.xml. A few that depend on the values of other options are set by logic contained in the configure script (a Perl script). The hard-coded defaults are designed to produce the standard production configurations of CAM.
The configure script allows the user to specify compile time options such as model resolution, dynamical core type, additional compiler flags, and many other aspects. The user can type configure --help for a complete list of available options.
The following options may all be specified with either one or two leading
--help. The few
options that can be expressed as single letter switches may not be clumped,
-h -s -v may NOT be expressed
-hsv. When multiple options are listed separated by a
vertical bar either version may be used.
These options will have an effect whether running CAM as part of CESM or running in a CAM standalone mode:
Switch on [off] age of air tracers. Default: on for waccm_phys, otherwise off.
Build CAM with specified prognostic chemistry package
trop_mam3 if the physics package
cam5, otherwise default is
This option is usually used with the
-ccsm_seq option as
part of the configuration for running biogeochemistry (BGC) compsets.
It modifies the CAM configuration by increasing the number of advected
constituents by 4.
Default: not set.
Specify the component interfaces
Enable the COSP simulator package. Default: not set.
A string of user specified CPP defines appended to
Makefile defaults. E.g.
-DVAR2'. Note that a string containing whitespace will need
to be quoted.
Build CAM with specified dynamical core.
CAMCHEM_EDITOR to allow the user to edit the chemistry mechanism file.
Specify horizontal grid. For spectral grids
nlon are the
number of latitude and longitude grid points respectively in the global Gaussian
grid. For FV grids use
dlon are the grid
cell size in degrees for latitude and longitude respectively. For SE grids
(cubed sphere) use
ne is the number of elements on an edge of the
np is the number of Gauss points on the edge
of an element.
mg if the physics package
Set total number of advected species to <n>. If
is set to a larger number than is required by the selected physics and
chemistry schemes, then the remainder will automatically be used for test
tracers. Default: set to the number required by the
selected physics and chemistry schemes.
Set number of advected test tracers to <n>. Default: 0.
Set number of vertical layers to <n>.
30 if the physics package
26 if the physics package
66 if the chemistry package
-waccmx is used.
Switch enables the use of offline driver for FV dycore. Default: not set.
uw if the physics package
Set maximum number of columns in a chunk to <n>. Default: 16.
Switch enables building CAM for perturbation growth tests. Only valid with
cam4 physics packages.
Physics package. Default:
Comma separated list of prognostic mozart species packages.
rrtmg if the physics package
Pathname of the user supplied chemistry mechanism file.
Switch enables the use of WACCM physics in any chemistry configuration. The user does not need to set this if one of the waccm chemistry options is chosen.
Build CAM/WACCM with WACCM upper Thermosphere/Ionosphere extended package.
Configure CAM to generate an IOP file that can be used to drive SCAM. This switch only works with the Eulerian dycore.
Compiles model in single column mode. Only works with Eulerian dycore.
This option must be used to specify SPMD parallelism when the CICE component is present. <n> is the number of MPI tasks. Setting ntasks > 0 implies -spmd. Use -nospmd to turn off linking with an MPI library. To configure for pure MPI specify "-ntasks N -nosmp". ntasks is used by CICE to determine default grid decompositions which must be specified at build time.
This option must be used to specify SMP parallelism when the CICE component is present. <n> is the umber of OpenMP threads per process. Setting nthreads > 0 implies -smp. Use -nosmp to turn off compilation of OMP directives. For pure OpenMP set "-nthreads N -nospmd" nthreads is used by CICE to determine default grid decomposition which must be specified at build time.
Switch on [off] SMP parallelism (OpenMP). This option can be used when building a model that doesn't contain CICE. It allows building an executable that is valid for any thread count.
Switch on [off] SPMD parallelism (MPI). This option can be used when building a model that doesn't contain CICE. It allows building an executable that is valid for any task count.
When CAM is running standalone with CICE the default CICE
decomposition is determined from the values of
The user also has the ability to explicitly set the CICE
decomposition using the following arguments:
Note: *** All four of these arguments must be set. ***
CICE block size in longitude dimension. This size must evenly divide the number of longitude points in the global grid.
CICE block size in latitude dimension. This size must evenly divide the number of latitude points in the global grid.
Maximum number of CICE blocks per processor.
CICE decomposition type [
Name of output cache file. Default: config_cache.xml.
Name of directory where output cache file is written. Default: CAM build directory.
Switch to specify that CAM is being built from within the CESM scripts. This produces Filepath and CCSM_cppdefs files that contains only the paths and CPP macros needed to build a library for the CAM component.
-help | -h
Print usage to STDOUT.
-silent | -s
Turns on silent mode - only fatal messages printed to STDOUT.
Switch on [off] testing of Fortran compiler and linking to external libraries.
-verbose | -v
Turn on verbose echoing of settings made by configure.
Echo the repository tag name used to check out this CAM distribution.
Options for surface components used in standalone CAM mode:
Switch on VOC emissions in CLM. Default: off.
Specify the sea ice component.
Specify the land component.
Specify ocean component.
Options for building CAM via standalone scripts:
Directory where CAM will be built. This is where configure will write the output files it generates (Makefile, Filepath, etc...). Default: ./
Name of the CAM executable. Default:
Directory where CAM executable will be created. Default: CAM build directory.
User specified C compiler. Default: set in Makefile depending on the OS and the Fortran compiler type.
A string of user specified C compiler options appended to the default options set in Makefile.
Switch to turn on building CAM with compiler options for debugging.
Specify a configuration file which will be used to supply defaults instead of one of the config_files/defaults_*.xml files. This file is used to specify model configuration parameters only. Parameters relating to the build which are system dependent will be ignored.
Directory containing ESMF library and the esmf.mk file. If this option is specified then the external ESMF library will be used in place of the ESMF-WRF time manager code which is provided in the CESM source distribution.
User specified Fortran compiler. Default: set in Makefile depending on the OS.
Type of the Fortran compiler. This argument is used in conjunction with
-fc argument when the name of the fortran compiler
refers to a wrapper script (e.g., mpif90 or ftn). In this case the user
needs to specify the type of Fortran compiler that is being invoked by the
Default: set in Makefile depending on the OS.
A string of user specified Fortran compiler options appended to the
default options set in the Makefile.
-fopt to override optimization flags.
A string of user specified Fortran compiler optimization flags. Overrides Makefile defaults.
Name of the GNU make program on your system. Supply the absolute
pathname if the program is not in your path (or fix your path). This is
only needed by configure for running tests via the
Directory containing LAPACK library.
A string of user specified load options. Appended to Makefile defaults.
User specified linker. Default: use the Fortran compiler.
Directory containing MPI include files.
Directory containing MPI library.
Directory containing NetCDF include files.
Directory containing NetCDF library.
Directory containing NetCDF module files.
Directory containing PnetCDF include files.
Directory containing PnetCDF library.
Build CAM with the offline radiation driver. This produces an executable that can only be used for offline radiation calculations.
Override the OS setting for cross platform compilation from the following
Default: OS on which configure is executed as defined by the Perl $OSNAME variable.
Directories containing user source code.