cov_cutoff_mod.rst

MODULE cov_cutoff_mod

Overview

Computes the weight with which an observation should impact a state variable that is separated by a given distance. The distance is in units determined by the location module being used.

Namelist

This namelist is read from the file input.nml. Namelists start with an ampersand '&' and terminate with a slash '/'. Character strings that contain a '/' must be enclosed in quotes to prevent them from prematurely terminating the namelist.

&cov_cutoff_nml
   select_localization = 1  
/

Item	Type	Description
select_localization	integer	Selects the localization function. 1 = Gaspari-Cohn 5th order polynomial with halfwidth c. 2 = Boxcar with halfwidth c (goes to 0 for z_in < 2c). 3 = Ramped Boxcar. Has value 1 for z_in < c and then reduces linearly to 0 at z_in = 2c.

Other modules used

types_mod
utilities_mod
location_mod

Public interfaces

use cov_factor_mod, only :	comp_cov_factor
A note about documentation st	yle. Optional arguments are enclosed in brackets [like this].
*var = comp_cov_factor(z_i :	n, c [, obs_loc] [, obs_type] [, target_loc] [, target_kind] [, localization_override])*
real(r8)	:: comp_cov_factor
real(r8), intent(in)	:: z_in
real(r8), intent(in)	:: c
type(location_type), op	tional, intent(in) :: obs_loc
integer, optional, inte	nt(in) :: obs_type
type(location_type), op	tional, intent(in) :: target_loc
integer, optional, inte	nt(in) :: target_kind
integer, optional, inte	nt(in) :: localization_override
Returns a weighting factor	for observation and a target variable (state or observation) separated by distance z_in
and with a half-width dist	ance, c. Three options are provided and controlled by a namelist parameter. The optional
argument localization_over	ride controls the type of localization function if present. The optional arguments obs_loc,
obs_type and target_loc, t	arget_kind are not used in the default code. They are made available for users who may want
to design more sophisticat	ed localization functions.
======================= ==	=======================================================================================
var We	ighting factor.
z_in Th	e distance between observation and target.
c Fa	ctor that describes localization function. Describes half-width of functions used here.
obs_loc Lo	cation of the observation.
obs_type Ob	servation specific type.
target_loc Lo	cation of target.
target_kind Ge	neric kind of target.
localization_override Co	ntrols localization type if present. Same values as for namelist control.
======================= == Files
========= =================== filename purpose
========= ===================	=======
input.nml to read ``cov_cutof	f_nml``

References

1. Gaspari and Cohn, 1999, QJRMS, 125, 723-757. (eqn. 4.10)

Error codes and conditions

Routine	Message	Comment
comp_cov_factor	Illegal value of "select_localization" in cov_cutoff_mod namelist	Only values 1 through 3 select a localization function.

Private components

N/A