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obj_anal_ic

Iterative improvement objective analysis.

Prototype

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

Arguments

zlon
zlat

One-dimensional arrays containing the longitudes and latitudes associated with the z values. They must be the same length as the rightmost dimension of z.

An array, whose rightmost dimension is the same length as zlon and zlat, 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 array of length mlon containing the longitude coordinates associated with the returned two-dimensional grid.

glat

A one-dimensional array of length nlat 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. The maximum size of rscan is 10. Typically, rscan contains one-to-four elements. Must be expressed in degrees of latitude and must be monotonically decreasing. eg: rscan = (/10, 5, 3/)

option

If option=False, this function will operate under default mode. If option=True, then this variable may have associated with it the attribute blend_wgt. This specifies how successive new estimates are 'blended'(local smoother) with previously derived estimates. These values must be 0.0 < blend_wgt < 1.0. A value of 1.0 means that the current interpolated value will be used. Otherwise:

      new_value(n) = blend_wgt(n)*current_estimate + (1-blend_wgt(n))*value(n-1)

The size of blend_wgt must be the same size as rscan.

Return value

If z is one dimensional,the return array be nlat x mlon; if multidimensional the return array will be K x nlat x mlon, where K represents the leftmost dimensions of z. It will be of type double if z is double, and float otherwise.

Description

This performs an iterative improvement type objective analysis using an input triplet set ( zlon, zlat, z). For each gridpoint, multiple passes of descending radii of influence are used to obtain better estimates.

Note_1: This built-in function replaces a previous function of the same name that was located in contributed.ncl [v5.1.0]. the built-in function is much faster. Unfortunately, it does not support the guess, zonal, count and setmsg optional arguments.

Note_2: It is possible that some returned grid points could be _FillValue. If this is not desired, increase the radii of influence.

Use the obj_anal_ic_Wrap function if metadata retention is desired. The interface is identical.

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(zlon,zlat,zVal, lon,lat, rscan, False)

   ; Use obj_anal_ic_Wrap if metadata retention is desired
   ; grid = obj_anal_ic_Wrap(zlon,zlat,zVal, lon,lat, rscan, False)

will use default behavior and return a 2D array of size nlat x mlon.

Example 2

Let zVal be a two-dimensional array of size (T,KPTS). Let lon and lat be 1D arrays of lengths N and M specifying grid locations. Then:

   grid = obj_anal_ic(xlon,ylat,zVal, lon,lat, False)        ; grid(T,N,M)

   ; Use obj_anal_ic_Wrap if metadata retention is desired
   ; grid = obj_anal_ic_Wrap(xlon,ylat,zVal, lon,lat, False)        ; grid(T,N,M)

will use default behavior and return a 3D array of size T x nlat x mlon.

Example 3