Help with regional streamline data drawn to a corresponding map

From: Erik Noble <enoble_at_nyahnyahspammersnyahnyah>
Date: Thu, 18 Oct 2007 16:07:09 -0400

Could I please have some help with plotting the regional U and V data
onto a WRF map?

Below is NCL code that takes the U and V data from WRF model output
and invokes the NCL streamline function.

I use the "gsn_csm_streamline" function (streamline plot draw without
a map) because the U and V data is strictly just that, "regional
data".
When I try to use the gsn_csm_streamline_map_ce function along with a
specific a subregion, NCL incorrectly assumes the data to represent
the globe and zooms in on the regional data.
Is there a way to plot the streamlines first and then, using the lat
and lons from the data itself, display an outline of the map/continent
beneath?

Attached is a picture of the resulting 925 mb streamlines over West
Africa, where you can already see a feint outline of Africa below.
any suggestions?
Thank you,

Erik

; Example script to produce stremaline plots for a WRF real-data run,
; with the ARW coordinate dynamics option.

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
;
; The WRF ARW input file.
; This needs to have a ".nc" appended, so just do it.
a = addfile("/Volumes/Data_and_Models/Model-Output/Athena/WRF-SOP3-Athena_Phys-3-1-1-1.nc","r")
; We generate plots, but what kind do we prefer?
 type = "x11"
; type = "pdf"
; type = "ps"
; type = "ncgm"
  wks = gsn_open_wks(type,"WRF_SOP3_Run-2_Sep10-13_3_1_1_Streamlines")

; Set some Basic Plot options
  ARWres = True
  ARWres_at_MainTitle = "REAL-TIME WRF"
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;What times and how many time steps are in the data set?
  times = wrf_user_list_times(a) ; get times in the file
  ntimes = dimsizes(times) ; number of times in the file

; The specific pressure levels that we want the data interpolated to.
  pressure_levels = (/925., 850., 700., 500., 300./) ; pressure levels to plot
  nlevels = dimsizes(pressure_levels) ; number of pressure levels

  do it = 324,324 ;;;;;Time step you want!!!!

    print("Working on time: " + times(it) )
    ARWres_at_TimeLabel = times(it) ; Set Valid time to use on plots

   mpres = True ; Create map background
       mpres_at_gsnMaximize = True
       mpres = ARWres
   mpres_at_tiMainString = "Streamlines" ; some tit
   ;mpres_at_FieldTitle = "Circulation" ; overwrite Field Title
   mpres_at_mpOutlineOn = True
   mpres_at_mpGeophysicalLineColor = "Black"
       mpres_at_mpGeophysicalLineThicknessF = "3.0"
       mpres_at_mpGridLineColor = "Black"
       mpres_at_mpLimbLineColor = "Black"
       mpres_at_mpNationalLineColor = "Black"
       mpres_at_mpPerimLineColor = "Black"
       mpres_at_mpUSStateLineColor = "Black"

 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;Variables
 p = wrf_user_getvar(a, "pressure",it) ; pressure is our vertical coordinate
     u = wrf_user_getvar(a,"ua",it) ; u averaged to mass points
    v = wrf_user_getvar(a,"va",it) ; v averaged to mass points
     z = wrf_user_getvar(a, "z",it) ; grid point height
    ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    do level = 0,nlevels-1 ; LOOP OVER LEVELS

      pressure = pressure_levels(level)
      z_plane = wrf_user_intrp3d( z,p,"h",pressure,0.,False)
    ; wrf_smooth_2d( z_plane, 1 )

   u_plane = wrf_user_intrp3d( u,p,"h",pressure,0.,False)
      v_plane = wrf_user_intrp3d( v,p,"h",pressure,0.,False)
     ; u_plane = u_plane*1.94386 ; kts
     ; v_plane = v_plane*1.94386 ; kts
     ; u_plane_at_units = "kts"
     ; v_plane_at_units = "kts"

      ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   ;Plot
   if ( pressure .eq. 925 ) then
        plot = gsn_csm_streamline(wks,u_plane,v_plane,mpres)

        end if

end do
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

  end do ; END OF TIME LOOP

end

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Picture_11.jpg
Received on Thu Oct 18 2007 - 14:07:09 MDT

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