Defines useful constants for Earth. Constants are defined as real.

FMSconstantsR4 have been declared as r4_kind or r8_kind PARAMETER.

The value of a constant defined and used from here cannot be changed in a users program. New constants can be defined in terms of values from the FMSconstants module and their includes using a parameter statement.

The currently support contant systems are: GFDL constants (gfdl_constantsR4.fh) GEOS constants (geos_constantsR4.fh) GFS constants (gfs_constantsR4.fh)

The name given to a particular constant may be changed.

Constants can only be used on the right side on an assignment statement (their value can not be reassigned).

Example:

    use FMSConstantsR4, only:  TFREEZE, grav_new => GRAV
    real, parameter :: grav_inv = 1.0 / grav_new
    tempc(:,:,:) = tempk(:,:,:) - TFREEZE
    geopotential(:,:) = height(:,:) * grav_new