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wrf_contour

Creates a contour plot from ARW WRF model output.

Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"      ; These two libraries are automatically
load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"    ; loaded from NCL V6.4.0 onward.
                                                              ; No need for user to explicitly load.

	function wrf_contour (
		nc_file     : file,     
		wks         : graphic,  
		data [*][*] : numeric,  
		res         : logical   
	)

	return_val [1] :  graphic

Arguments

nc_file

Reference to an input netCDF file opened with addfile.

wks

An NCL Workstation identifier. The identifier is one returned either from calling gsn_open_wks or calling create to create a Workstation object.

data

A two-dimensional array to be contoured.

res

A variable containing an optional list of plot resources, attached as attributes. See description section below for more information.

Return value

A scalar id of the plot created is returned.

Description

This function creates a contour plot (but does not draw it). To draw the plot, see the example below.

If data has a _FillValue attribute, this value will be used as a missing value.

If data has a "description" attribute, this value will be used in the plot title.

This function recognizes some special resources that can be attached as attributes to res:

ContourParameters - this resource can either be a scalar that represents the contour level spacing, or it can be an array of three elements that represent the minimum level, the maximum level, and the level spacing. This resource is not recognized by any of the gsn_xxxx plotting routines.
gsnContourZeroLineThicknessF - sets the thickness of the zero contour line. The default for this routine is 2.0 (when using any of the gsn_xxx routines, the default is 1.0)
gsnContourNegLineDashPattern - sets the line style of the zero contour line. The default for this routine is 1, which is a dashed line (see the dash pattern table for more options). When using any of the gsn_xxx routines, the default is 0 (a solid line).
FieldTitle - This becomes the main title of the contour plot. If not set, then the "description" attribute of the data variable will be used, if available.
This also becomes part of the "information label" on the contour plot.
SubFieldTitle - if set, this will be appended to the FieldTitle title with a space between the two.
UnitLabel - if set, this will be appended to the existing FieldTitle title in parentheses. If not set, the "units" attribute of the data_u variable will be used, if available.
PlotLevelID - if set, this will be appended to the existing FieldTitle title with an " at " between the two. If not set, the "PlotLevelID" attribute of the data_u variable will be used, if available.
NoHeaderFooter - Turn off all the extra titles. This is useful if you need to panel the plot later.

The final main title could look something like "FieldTitle SubFieldTitle (UnitLabel) at PlotLevelID".

To make the labelbar vertical instead of horizontal, set these two resources:

res@lbOrientation = "vertical"
res@pmLabelBarSide = "right"

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

Examples

Example 1

  load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
  load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"

  a = addfile("wrfout_d01_2000-01-24_12:00:00.nc","r")

  wks = gsn_open_wks("x11","test")

  ter = wrf_user_getvar(a,"HGT",0)   ; Get terrain height for time 0

  res = True
  res@cnFillOn  = True
  res@gsnDraw   = True    ; Forces the plot to be drawn
  res@gsnFrame  = True    ; Frame advance
  contour = wrf_contour(a,wks,ter,res)

You can see some other example scripts and their resultant images at: