MODULE types_mod¶

Overview¶

Provides some commonly used mathematical constants, and a set of Fortran integer and real kinds, to be used to select the right variable size (e.g. 4 bytes, 8 bytes) to match the rest of the DART interfaces. (DART does not depend on compiler flags to set precision, but explicitly specifies a kind for each variable in the public interfaces.)

Other modules used¶

none

Public interfaces¶

This routine provides the following constants, but no routines of any kind.

The constants defined here may or may not be declared the same as constants used in non-DART pieces of code. It would seem like a good idea to match the DART definition of ‘gas_constant’ to the WRF equivalent if you are going to be running WRF/DART experiments (for example).

use types_mod, only :	i4
	i8
	r4
	r8
	c4
	c8
	digits12
	PI
	DEG2RAD
	RAD2DEG
	SECPERDAY
	MISSING_R4
	MISSING_R8
	MISSING_I
	MISSING_DATA
	metadatalength
	obstypelength
	t_kelvin
	es_alpha
	es_beta
	es_gamma
	gas_constant_v
	gas_constant
	L_over_Rv
	ps0
	earth_radius
	gravity

integer, parameter :: i4
integer, parameter :: i8
integer, parameter :: r4
integer, parameter :: r8
integer, parameter :: c4
integer, parameter :: c8
integer, parameter :: digits12

These kinds are used when declaring variables, like:

real(r8)    :: myvariable
integer(i4) :: shortint

All DART public interfaces use types on the real values to ensure they are consistent across various compilers and compile-time options. The digits12 is generally only used for reals which require extra precision.

Some models are able to run with single precision real values, which saves both memory when executing and file space when writing and reading restart files. To accomplish this, the users edit this file, redefine r8 to equal r4, and then rebuild all of DART.

real(KIND=R8), parameter :: PI
real(KIND=R8), parameter :: DEG2RAD
real(KIND=R8), parameter :: RAD2DEG
real(KIND=R8), parameter :: SECPERDAY

Some commonly used math constants, defined here for convenience.

real(KIND=R4), parameter :: MISSING_R4
real(KIND=R8), parameter :: MISSING_R8
integer,       parameter :: MISSING_I
integer,       parameter :: MISSING_DATA

Numeric constants used in the DART code when a numeric value is required, but the data is invalid or missing. These are typically defined as negative and a series of 8’s, so they are distinctive when scanning a list of values.

integer, parameter :: metadatalength
integer, parameter :: obstypelength

Some common string limits used system-wide by DART code. The obstypelength is limited by the Fortran-imposed maximum number of characters in a parameter; the metadatalength was selected to be long enough to allow descriptive names but short enough to keep printing to less than a single line.

real(KIND=R8), parameter :: t_kevin
real(KIND=R8), parameter :: es_alpha
real(KIND=R8), parameter :: es_beta
real(KIND=R8), parameter :: es_gamma
real(KIND=R8), parameter :: gas_constant_v
real(KIND=R8), parameter :: gas_constant
real(KIND=R8), parameter :: L_over_Rv
real(KIND=R8), parameter :: ps0
real(KIND=R8), parameter :: earth_radius
real(KIND=R8), parameter :: gravity

A set of geophysical constants, which could be argued do not belong in a DART-supplied file since they are quite probably specific to a model or a particular forward operator.

Best case would be if we could engineer the code so these constants were provided by the model and then used when compiling the forward operator files. But given that Fortran use statements cannot be circular, this poses a problem. Perhaps we could work out how the obs_def code could define these constants and then they could be used by the model code. For now, they are defined here but it is up to the model and obs_def code writers whether to use these or not.

Namelist¶

There is no namelist for this module.

Files¶

None.

References¶

none

Private components¶

N/A