[ncl-talk] Trying to plot WRF data without using built-in WRF functions

[Craig Tierney - NOAA Affiliate]

Hello,

I am trying to plot WRF data using NCL 6.1.2 without using the built-in WRF
functions.  The reason I am doing this is because what I really want to do
is plot streamlines, and when I had problems doing that I tried to simplify
what I was doing first.

I found the examples page for plotting WRF using the gsn functions.  I
started with the wrf_gsn_2.ncl example.  All I did was change the WRF input
file to point to mine. The output looked like the map was
CylindralEquidistant (the specified mapping) but the data are in
LambertConformal, so the height field is not plotted as rectangular.  So
you get the curved shape of my domain on the rectangular map where the
lines of latitude are horizontal.   This isn't want I want, but the script
seems to be doing what it should for my domain.

What I found strange is that when I looked at the output of
wrf_map_resources, that it says the Projection is LambertConformal.

So I tried changing the mpProjection to LambertConformal.  When I did this
I got something that looked more StereoGraphic.  The plot was centered at
the north pole.

When I compare the output of wrf_map_resources between this script and my
script that uses wrf_map_overlays, the contents are identical.

So how do I get NCL to plot my data using the GSN functions in the same
projection as using wrf_map_overlays?

Here is the script that I ran:

;----------------------------------------------------------------------
; wrf_gsn_2.ncl
;----------------------------------------------------------------------
; Concepts illustrated:
;   - Using gsn_csm_contour_map to plot WRF-ARW data
;----------------------------------------------------------------------
; This example is similar to wrf_gsn_1.ncl, except more plot resources
; are set to:
;   - explicitly set the contour levels
;   - change the look of the map outlines
;   - change the color map
;   - make the labelbar vertical
;----------------------------------------------------------------------;
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"

begin
;---Open WRF output file.
  dir      =
"/scratch2/portfolios/BMC/winds/Craig.Tierney/theia/wrf/windswrf/trunk/conusplus-wrf-6day/201308010000/nowfp-nocu/wrf/"
  filename = "wrfout_d01_2013-08-04_00:00:00"
  a = addfile(dir + filename + ".nc","r")

;---Read terrain height and lat/lon off file.
  it        = 0     ; first time step
  hgt       = wrf_user_getvar(a,"HGT",it)    ; Terrain elevation
  hgt at lat2d = wrf_user_getvar(a,"XLAT",it)   ; latitude/longitude
  hgt at lon2d = wrf_user_getvar(a,"XLONG",it)  ; required for plotting

  wks = gsn_open_wks("png","wrf_gsn")

;---Set some basic plot options
  res               = True

  res at gsnMaximize   = True   ; maximize plot in frame

  res at tiMainString  = filename

  res at cnFillOn      = True
  res at cnFillPalette = "OceanLakeLandSnow"
  res at cnLinesOn     = False

 res at mpProjection = "CylindricalEquidistant"
;  res at mpProjection  = "LambertConformal"

;---Zoom in on plot
  res at mpMinLatF     = min(hgt at lat2d)
  res at mpMaxLatF     = max(hgt at lat2d)
  res at mpMinLonF     = min(hgt at lon2d)
  res at mpMaxLonF     = max(hgt at lon2d)

;---Additional resources desired
  res at pmTickMarkDisplayMode = "Always"   ; nicer tickmarks

  res at mpDataBaseVersion     = "MediumRes"       ; better and more map
outlines
  res at mpDataSetName         = "Earth..4"
  res at mpOutlineBoundarySets = "AllBoundaries"
  res at mpOutlineOn           = True

  res at lbOrientation         = "Vertical"
  res at tiMainOffsetYF        = -0.03           ; Move the title down

;---Change contour levels to better match the color map being used
  res at cnLevelSelectionMode = "ExplicitLevels"
  res at cnLevels =
(/2,100,200,400,600,800,1000,1200,1400,1600,1800,2000,2200/)


  contour = gsn_csm_contour_map(wks,hgt,res)

;
; This is for debugging purposes only. It shows what map resources the
; wrf_map_overlays routine would have use, if you had called that routine
; to do the plotting. This can be useful if you are trying to reproduce
; an original WRF-ARW plot.
;
  dbgres = True
  dbgres = wrf_map_resources(a,dbgres)
  print(dbgres)
end

Craig
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