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lderuvg

Computes the latitudinal derivatives using spherical harmonics, given vector components (u,v) on a gaussian grid.

Prototype

	procedure lderuvg (
		u   : numeric,          
		v   : numeric,          
		uy  : float or double,  
		vy  : float or double   
	)

Arguments

u
v

vector function arrays (input, two or more dimensions, last two dimensions must be nlat x nlon)

input values must be in ascending latitude order
input arrays must be on a global grid

uy
vy

vector latitudinal derivative arrays (output, same dimensions as u, v, values will be in ascending latitude order)

Description

lderuvg computes the latitudinal derivative vector arrays from the vector components u and v and returns the results in the arrays uy and vy. lderuvg operates on a gaussian grid. If the input arrays u and v are on a fixed grid, lderuvf should be used.

This procedure does not handle missing values. If any missing values are encountered in a particular 2D input grid, then all of the values in the corresponding output grids will be set to the missing value defined by the output grids' _FillValue attributes.

Note: For the arrays whose last two dimensions are nlat x nlon, the rest of the dimensions (if any) are collectively referred to as N. If the input/output arrays are just two dimensions, then N can either be considered equal to 1 or nothing at all.

Arrays which have dimensions N x nlat x nlon should not include the cyclic (wraparound) points when invoking the procedures and functions which use spherical harmonics (Spherepack).

For example, if an array x has dimensions nlat = 64 and nlon = 129, where the "129" represents the cyclic points, then the user should pass the data to the procedure/function via:

    z = sample ( x([...],:,0:nlon-2) )  ; does not include cyclic points

Examples

Example 1

Read u and v (on a gaussian grid) from a netCDF file and compute the latitudinal derivatives:

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
begin
   a = addfile("/cgd/cas/shea/MURPHYS/ATMOS/80.nc","r")
   v200 = a->V(0,{189.},:,:)			; v200 is dimensioned nlat x nlon
   u200 = a->U(0,{189.},:,:)			; u200 is dimensioned nlat x nlon
   printVarSummary(v200)
   latder_v = v200				; preallocate space for the returned array
   latder_u = u200				; preallocate space for the returned array
   lderuvg(u200,v200,latder_u,latder_v)
end

Errors

If jer or ker is equal to: