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dz_height

Calculates the height layer thicknesses at each grid point over varying surface terrain.

Prototype

	function dz_height (
		z        : numeric,  
		zsfc     : numeric,  
		ztop [1] : numeric,  
		iopt     : integer   
	)

	return_val  :  numeric

Arguments

z

An array of at least three dimensions. The rightmost dimensions must be (klvl,nlat,mlon). Dimensions to the left of klvl are optional. The values at each grid point must be monotonically increasing or decreasing but may be unequally spaced.

zsfc

A scalar or an array containing the surface height. Must have the same units as z. The rightmost dimensions must be latitude and longitude, eg: (nlat,mlon). Dimensions to the left of nlat are optional. If present, they must match the dimensions of z.

ztop

A scalar specifying the top of the column. Must be greater-than or equal to 0.0 and must have the same units as z.

iopt

Set to zero. Currently not used.

Return value

A variable containing the layer "delta z". It will have the same shape and size as z. It will be of type double if any of the input is double and float otherwise.

Description

Calculates the layer height thicknesses at each grid point over a vary surface elevations. It is analogous to dpres_hybrid_ccm for hybrid coordinates and dpres_plevel for constant pressure coordinates. At each grid point the sum of the height thicknesses equates to [ztop-zsfc]. At each grid point, the returned values above ztop and below zsfc will be set to z@_FillValue. If there is no zsfc@_FillValue then the _FillValue will be set to the default missing value for the output type (it is 1e20 in NCL versions 5.2.x and earlier). If ztop or zsfc is between z levels then the layer thickness is modifed accordingly. If zsfc is set to _FillValue, all layer thicknesses are set to the appropriate _FillValue.

The primary purpose of this function is to return height layer thicknesses to be used to weight observations for integrations.

See Also

dpres_hybrid_ccm,dpres_plevel, conform,conform_dims

Examples

Example 1 Consider one grid point and three different boundary zsfc and ztop: [0, 27000], [500, 27000], [500,21500]. Currently, the function requires 3 or more dimensions. Hence, this example requires some additional steps.

  Z    = (/ 97.1,308.8,545.9,811.4,1108.8,1441.8,1814.8        \
          ,2232.6,2700.5,3224.6,3811.5,4468.9,5205.2,6029.8    \
          ,6953.4,7987.8,9146.3,10443.9,11897.2,13524.8,15357.1\
          ,17335.3,19339.7,21339.8,23339.8,25339.8/)*1d0
  kz   = dimsizes(Z) 

    ; make a 'fake' grid point for this example
  z    = conform_dims( (/kz,1,1/), Z, 0)     ; (kz,1,1)

  zsfc = 0 
  zsfc = 2700
  dz   = dz_height(z, zsfc, ztop, 0)  

The output from the print statement is:
                           0        500        500          
               Z       27000      27000      21500
        --------------------------------------------
(0)          97.1      202.9        0.0        0.0
(1)         308.8      224.4        0.0        0.0
(2)         545.9      251.3      178.7      178.7
(3)         811.4      281.5      281.5      281.5
(4)        1108.8      315.2      315.2      315.2
(5)        1441.8      353.0      353.0      353.0
(6)        1814.8      395.4      395.4      395.4
(7)        2232.6      442.8      442.8      442.8
(8)        2700.5      496.0      496.0      496.0
(9)        3224.6      555.5      555.5      555.5
(10)       3811.5      622.1      622.1      622.1
(11)       4468.9      696.9      696.9      696.9
(12)       5205.2      780.4      780.4      780.4
(13)       6029.8      874.1      874.1      874.1
(14)       6953.4      979.0      979.0      979.0
(15)       7987.8     1096.4     1096.4     1096.4
(16)       9146.3     1228.1     1228.1     1228.1
(17)      10443.9     1375.5     1375.5     1375.5
(18)      11897.2     1540.4     1540.4     1540.4
(19)      13524.8     1729.9     1729.9     1729.9
(20)      15357.1     1905.3     1905.3     1905.3
(21)      17335.3     1991.3     1991.3     1991.3
(22)      19339.7     2002.2     2002.2     2002.2
(23)      21339.8     2000.1     2000.1     1160.2
(24)      23339.8     2000.0     2000.0        0.0
(25)      25339.8     2660.2     2660.2        0.0
Example 2 Consider Z(lev,lat,lon), ZSFC and z(time,lev,lat,lon), zsfc(time,lat,lon):

  zsfc = 2700
  DZ   = dz_height(Z, ZSFC, ztop, 0)   ; DZ(klev,nlat,mlon)  
  dz   = dz_height(z, zsfc, ztop, 0)   ; dz(ntim,klev,nlat,mlon)  

  copy_VarCoords(Z,DZ)    ; copy coordinates 
  DZ@long_name = "layer thickness"
  DZ@units     = Z@units

  copy_VarCoords(z,dz) 
  dz@long_name = "layer thickness"
  dz@units     = z@units