Module constants

module constants_mod

Contact: Bruce Wyman
Reviewers:
Change History: WebCVS Log
Last Modified: 2002/03/01 23:43:42

OVERVIEW

Defines useful constants for Earth in mks units.

Constants are defined as real parameters.They are accessed through the "use" statement. While the local name of constant may be changed, their values can not be redefined.

OTHER MODULES USED

fms_mod

PUBLIC INTERFACE

use constants_mod [, only:  constants_init ]

constants_init:: A optional initialization routine. The only purpose of this routine is to write the version and tag name information to the log file.

PUBLIC DATA

Name	Type	Value	Units	Description
RADIUS	real	6376.e3	meters	radius of the earth
OMEGA	real	7.292e-5	1/sec	rotation rate of the planet (earth)
GRAV	real	9.80	m/s2	acceleration due to gravity
RDGAS	real	287.04	J/kg/deg	gas constant for dry air
KAPPA	real	2./7.		RDGAS / CP
CP	real	RDGAS/KAPPA	J/kg/deg	specific heat capacity of dry air at constant pressure
RVGAS	real	461.50	J/Kg/deg	gas constant for water vapor
DENS_H2O	real	1000.	Kg/m3	density of liquid water
HLV	real	2.500e6	J/Kg	latent heat of evaporation
HLF	real	3.34e5	J/kg	latent heat of fusion
HLS	real	2.834e6	J/Kg	latent heat of sublimation
TFREEZE	real	273.16	deg K	temp where fresh water freezes
STEFAN	real	5.6734e-8	(W/m2/deg4	Stefan-Boltzmann constant
VONKARM	real	0.40	---	Von Karman constant
PI	real	3.14159265358979323846	---	is it enough?

PUBLIC ROUTINES

constants_init
```
call constants_init 
```
DESCRIPTION

The only purpose of this routine is to write the version and tag name information to the log file. This routine does not have to be called. If it is called more than once or called from other than the root PE it will return silently. There are no arguments.

DATA SETS

None.

ERROR MESSAGES

None.

REFERENCES

None.

COMPILER SPECIFICS

None.

PRECOMPILER OPTIONS

None.

LOADER OPTIONS

None.

TEST PROGRAM

None.

KNOWN BUGS

None.

NOTES

NOTES ON USAGE:

All constants have been declared as type REAL, PARAMETER.

The value a constant can not be changed in a users program. New constants can be defined in terms of values from the constants module using a parameter statement. 

The name given to a particular constant may be changed. 

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

EXAMPLES:

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

FUTURE PLANS

1. Renaming of constants.

2. Additional constants.

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