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


load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"  ; This library is automatically loaded
                                                             ; from NCL V6.2.0 onward.
                                                             ; No need for user to explicitly load.

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




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


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.


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


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


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/)


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.

A user supplied N x M array of the same type as z containing a first guess for the output grid.
Use a simple zonal average of the input z as a first guess.
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.
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.


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


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)