# wrf_user_intrp3d

Interpolates ARW WRF model data vertically or horizontally.

## Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl" ; These two libraries areautomaticallyload "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl" ;loadedfrom NCL V6.4.0 onward. ; No need for user to explicitly load. function wrf_user_intrp3d ( var3d : numeric, vert : numeric, plot_type : string, loc [*] : numeric, ; up to four values angle : numeric, res [1] : logical ) return_val : numeric

## Arguments

*var3d*

Data on model levels that will be interpolated. The rightmost dimensions of this array is
*nz* x *ny* x *nx*.

*vert*

Array of vertical coordinates for var3d. This must either be
pressure/height. Dimensions must be the same as those of
*var3d*.

If *vert* is **pressure**, the units may be either
**hPa** or **Pa**. If vert is
**height**, then the units of the field must be in
**m**.

*plot_type*

Plot orientation. Use "h" for horizontal plots, and "v" for vertical cross sections.

*loc*

Interpolation information. Can contain up to four scalar values:

**Horizontal plots**Use a single value to indicate the level or height to interpolate to, for example, 500 for 500hPa or 2000 for 2km.

**Cross sections**Use two values if plotting a plane through a given point on the model domain. The two values represent the x/y location through which the plane will pass. The

*angle*argument will be required in this case.Use four values if plotting from point A to point B. The four values represent the x/y locations of points A and B. The values should be ordered as (xstart,xend,ystart,yend).

*angle*

Only valid for cross sections where a plane will be plotted through a given point on the model domain. 0.0 represents a S-N cross section and 90.0 a W-E cross section.

*res*

Set to True if plotting a cross section from point A to point B; otherwise set to False.

## Return value

Data interpolated to a horizontal or vertical plane.

## Description

This function interpolates a three-dimensional variable to either a horizontal or vertical plane. The script can interpolate to either height or pressure coordinates.

**Note**: in NCL V6.5.0 a bug was fixed in this
routine and in **wrf_user_intrp2d**
in which the 0th grid point was not being included when setting up the
output domain, causing the output array to be missing a grid point in
the rightmost dimension.

For vertical cross sections, the vertical levels are automatically chosen to be at approximately 1% increments from minimum height to maximum height (or maximum pressure to minimum pressure).

**Note:** in NCL V6.0.0, the default missing value was changed from
-999999 to the default missing for an NCL float or double (9.96921e+36
or 9.969209968386869e+36, depending on output type).

**wrf_user_intrp3d** is part of a
library of functions and procedures in WRFUserARW.ncl written to help users
plot ARW WRF model data.

Questions on this function should be sent to wrfhelp@ucar.edu.

## See Also

See the full list of WRF functions.

## Examples

**Example 1**

a =addfile("wrfout_d01_2000-01-24_12:00:00.nc","r") time = 1 tc =wrf_user_getvar(a,"tc",time) ; T [C] rh =wrf_user_getvar(a,"rh",time) ; relative humidity z =wrf_user_getvar(a, "z",time) ; grid point height p =wrf_user_getvar(a, "pressure",time) ; total pressure dimsrh =dimsizes(rh) plane = (/ dimsrh(2)/2, dimsrh(1)/2 /) ; pivot point is center of domain ; Extract data on a N-S cross section that runs through "plane" ; Interpolate to height rh_plane1 =wrf_user_intrp3d(rh,z,"v",plane,0.0,False) tc_plane1 =wrf_user_intrp3d(tc,z,"v",plane,0.0,False) ; Extract data on a W-E cross section that runs through "plane" ; Interpolate to pressure rh_plane2 =wrf_user_intrp3d(rh,p,"v",plane,90.0,False) tc_plane2 =wrf_user_intrp3d(tc,p,"v",plane,90.0,False)

**Example 2**

a =addfile("wrfout_d01_2000-01-24_12:00:00.nc","r") time = 1 tc =wrf_user_getvar(a,"tc",time) ; T [C] z =wrf_user_getvar(a,"z",time) ; z on mass points plane = (/ 40,81 , 259,81 /) ; approx. START x;y and END x;y point ; Extract cross section from point A to point B, as defined in "plane", ; and vertically interpolate to height coordinates ("z") tc_plane =wrf_user_intrp3d(tc,z,"v",plane,0.,True)

**Example 3**

a =You can see some other example scripts and their resultant images at:addfile("wrfout_d01_2000-01-24_12:00:00.nc","r") time = 1 tc =wrf_user_getvar(a,"tc",time) ; T [C] p =wrf_user_getvar(a,"pressure",time) ; total pressure ; Horizontally interpolate to pressure coordinates ("p") pressure = 850. ; 850 hPa tc_plane =wrf_user_intrp3d(tc,p,"h",pressure,0.,False)

http://www.mmm.ucar.edu/wrf/OnLineTutorial/Graphics/NCL/