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 style. Optional arguments are enclosed in brackets [like this].


var = comp_cov_factor(z_in, 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), optional, intent(in) :: obs_loc
integer, optional, intent(in)             :: obs_type
type(location_type), optional, intent(in) :: target_loc
integer, optional, intent(in)             :: target_kind
integer, optional, intent(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 distance, c. Three options are provided and controlled by a namelist parameter. The optional argument localization_override controls the type of localization function if present. The optional arguments obs_loc, obs_type and target_loc, target_kind are not used in the default code. They are made available for users who may want to design more sophisticated localization functions.

var

Weighting factor.

z_in

The distance between observation and target.

c

Factor that describes localization function. Describes half-width of functions used here.

obs_loc

Location of the observation.

obs_type

Observation specific type.

target_loc

Location of target.

target_kind

Generic kind of target.

localization_override

Controls localization type if present. Same values as for namelist control.

Files

filename

purpose

input.nml

to read cov_cutoff_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