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int2p

Interpolates pressure levels to a different set of pressure levels.

Prototype

	function int2p (
		pin        : numeric,  
		xin        : numeric,  
		pout       : numeric,  
		linlog [1] : integer   
	)

	return_val  :  numeric

Arguments

pin

An array of any dimensionality containing input pressure levels. If multi-dimensional, the level dimension must be in the rightmost position and the values must be monotonically increasing or decreasing.

xin

An array of any dimensionality containing the data to be interpolated. Must be the same shape and size as pin.

pout

An array of any dimensionality containing output pressure levels with values monotonically increasing or decreasing. If multi-dimensional, the level dimension must be in the rightmost dimension and all other dimensions must be the same as xin. If one-dimensional, then all of xin will be interpolated to the the same levels. Must have the same units as pin.

linlog

A scalar integer indicating the type of interpolation:

abs(linlog) == 1 --> linear interpolation
abs(linlog) != 1 --> log interpolation

If linlog is negative, then extrapolation to levels outside the range of pin will occur. Use extrapolation with caution.

Return value

The returned array will have the same shape as xin but the rightmost dimension will have the the sizes of the rightmost dimension of pout. The return type will be double if pin, xin, or pout are double, float otherwise.

Description

This function interpolates the values of the rightmost dimension of xin from one set of pressure levels to another set of pressure levels. The interpolation can be either linear or log. Extrapolation is optional. Missing values are allowed, but they are ignored.

Examples

Example 1

begin
  linlog = 2   ; ln(p) interpolation

  pi =(/ 1000.,925.,850.,700.,600.,500.,400.,300.,250., \
          200.,150.,100.,70.,50.,30.,20.,10. /)
           
  xi =(/ 28., 23., 18., 10.,  2., -4., -15.,-30.,-40., \
        -52.,-67.,-78.,-72.,-61.,-52.,-48.,-46. /)

  po =(/ 1000.,950.,900.,850.,800.,750.,700.,600.,500., \
          425.,400.,300.,250.,200.,100.,85.,70.,50.,40.,\
           30.,25.,20.,15.,10. /)

           
  xo = int2p (pi,xi,po,linlog)
; xo will contain (/ 28.,24.71,21.37,18. ,...., -48.,-47.17,-46./).
end

Example 2

begin
  linlog = -1   ; linear interpolation and extrapolation

  pi = (/ 10., 20., 30., 50., 70.,100.,150.,200., \
         250.,300.,400.,500.,600.,700.,850.,925.,1000. /)
           
  xi =(/-46.,-48.,-52.,-61.,-72.,-78.,-67.,-52., \
        -40.,-30.,-15., -4.,  2., 10., 18., 23., 28. /)

  po =(/ 5., 7., \                    ; extrapolation
        10.,15.,20.,25.,30.,40.,50.,70.,85.,100.,200.,250.,300., \
        400.,425.,500.,600.,700.,750.,800. ,850.,900.,925.,1000., \
        1005.,1012. /)                ; extrapolation
        
           
  xo = int2p (pi,xi,po,linlog)
  xo = -45.,-45.4,-46.,-47. ,..., 21.33,23.,28.,28.33,28.8.
end

Example 3

Let p_out be four-dimensional with dimensions time, lat, lon, pout_level. Additionally, p_in and t_in are four-dimensional with dimensions time, lat, lon, pin_level. Linearly interpolate with extrapolation.

    linlog = -1
    t_out = int2p(p_in,t_in,p_out,linlog)
;   t_out is dimensioned time, lat, lon, pout_level

Example 4

Similar to example 3, but p_out is one-dimensional:

  t_out = int2p(p_in,t_in,p_out,linlog)
; t_out is interpolated to the uniform set of pressure levels represented by p_in

Example 5

Similar to example 3, but none of the input arrays have level in the rightmost dimension and must be reordered

  t_out = int2p(p_in(time|:,lat|:,lon|:,pin_lev|:), \
                                t_in(time|:,lat|:,lon|:,pin_lev|:), \
                                p_out(time|:,lat|:,lon|:,pout_lev|:), linlog)
; t_out is dimensioned time, lat, lon, pout_level