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obj_anal_ic_deprecated

Iterative correction objective analysis (Cressman, Barnes) (deprecated)

Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"

	function obj_anal_ic_deprecated (
		zlon   [*] : numeric,  
		zlat   [*] : numeric,  
		z      [*] : numeric,  
		glon       : numeric,  
		glat       : numeric,  
		rscan  [*] : numeric,  
		option [1] : logical   
	)

	return_val  

Arguments

zlon
zlat

One-dimensional arrays of the same length containing the coordinates associated with the z values.

z

A one-dimensional array containing the values associated with the zlon and zlat coordinates. Missing values, indicated via z@_FillValue, may be present but will be ignored.

glon

A one-dimensional or two-dimensional array of length M containing the longitude coordinates associated with the returned two-dimensional grid.

glat

A one-dimensional array or two-dimensional of length N containing the latitude coordinates associated with the returned two-dimensional grid.

rscan

A one-dimensional array of length K specifying the successive radii of influence. Must be expressed in degrees of latitude and should be monotonically decreasing. eg: rscan = (/10, 5, 3/)

option

If option=False, this function will operate under default mode. That is, the first guess will be 0.0 and values located outside rscan(0) will be set to _FillValue. If option=True, then this variable may have associated with it the attributes guess, zonal and/or setmsg.

option@guess
A user supplied N x M array of the same type as z containing a first guess for the output grid.
option@zonal
Use a simple zonal average of the input z as a first guess.
option@count
If set to True, then a 3-dimensional array of size K x N x M will be returned as an attribute of the returned grid. This will contain the number of observations used in each scan. Default is False.
option@setmsg
The default is True. This means that grid points located outside rscan(0) will be set to _FillValue.

Return value

The return array will be N x M.

Description

This performs an iterative correction type objective analysis using an input triplet set ( zlon, zlat, z). In meteorology, this is called a Cressman or Barnes style analysis. Successively smaller radii are used to modify previous field estimates. As with other interpolation methods the results will be a function of the spatial distribution of the data values (z).

The execution time is a function of the number of z, the output grid resolution and the number and extent of search radii used.

See Also

triple2grid, triple2grid2d, grid2triple, natgrid

Examples

Example 1

Assume zlon, zlat and zVal are one-dimensional (1D) arrays; let lon and lat be 1D arrays specifying grid locations. Then:

   rscan = (/10, 5, 2/)
   grid = obj_anal_ic_deprecated(zlon,zlat,zVal, lon,lat, rscan, False)

will use default behavior and return a 2D array of size N x M M.

Example 2

   opt  = True           
   opt@zonal = True   ; use zonal averages as a 1st guess
   grid = obj_anal_ic_deprecated(xlon,ylat,zVal, lon,lat, rscan, opt)