[ncl-talk] Overlay wind vectors on orthographic map

[Karin Meier-Fleischer]

Hi Lyndon,

the plot function gsn_csm_vector_scalar can't handle the @cn resources 
and gives the warnings. To get rid of the warnings separate the contour 
(res: contour and map) and vector resources (e.g. in vcres)  as shown in 
the attached script.

To use the @vcLineArrowColor you have to set the @vcMonoLineArrowColor 
to True which is described in the documentation:
http://ncl.ucar.edu/Document/Graphics/Resources/vc.shtml#vcLineArrowColor

It is always a good idea to take a look at the resources documentation 
(and read) if a resource setting is not working as expected.

Bye,
Karin

Am 05.07.17 um 09:23 schrieb Lyndon Mark Olaguera:
> Dear NCL-experts,
>
>
> I am trying to overlay wind vectors over an orthographic map but I am 
> getting the following warning messages:
>
> warning:cnFillOn is not a valid resource in proj_vector at this time
> warning:cnLineLabelsOn is not a valid resource in proj_vector at this time
> warning:cnLevelSelectionMode is not a valid resource in proj_vector at 
> this time
> warning:cnMinLevelValF is not a valid resource in proj_vector at this time
> warning:cnMaxLevelValF is not a valid resource in proj_vector at this time
> warning:cnLevelSpacingF is not a valid resource in proj_vector at this 
> time
> warning:cnFillDrawOrder is not a valid resource in proj_vector at this 
> time
> warning:cnLinesOn is not a valid resource in proj_vector at this time
> warning:cnFillPalette is not a valid resource in proj_vector at this time
>
>
> Also, when I try to use the *"LineArrow"* as a glyph style, the color 
> of the arrows are "blue" and ignores whatever I set in 
> *res at vcLineArrowColor = "black".* I also tried using "*FilledArrow" 
> *as the glyph style and this solves the issue. Nonetheless, I want to 
> know why the first one (LineArrow glyph style) does not work and also 
> the warning messages.
>
>
> I'll appreciate any suggestion on how I can do this correctly in NCL.
>
> I am attaching my script and the output here.
> The sample data sets that I am using can be found in this link:
>
> https://www.dropbox.com/s/8vwk894gkyof082/sample_data.zip?dl=0
>
> Lyndz
>
>
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begin

  a = addfile("may_hgt-hgt_1979-1995_850hPa.nc","r")
  b = addfile("regpval_uwnd_1979-1995.nc","r")  
  c = addfile("regpval_vwnd_1979-1995.nc","r")
;************************************************
; read in data
;************************************************
  printVarSummary(a)
  printVarSummary(b)
  printVarSummary(c)
  t = a->regslope(:,:)
  u = b->regpval(:,:)
  v = c->regpval(:,:)   
                               
;************************************************
; create plot
;************************************************
  wks = gsn_open_wks("png","plot_proj")                ; send graphics to PNG file
       
  res                   = True      
  res at gsnDraw           = False
  res at gsnFrame          = False                   ;-- don't advance the frame
        
  res at cnLevelSelectionMode = "ManualLevels"      
  res at cnMinLevelValF    = -5.00      
  res at cnMaxLevelValF    = 5.00      
  res at cnLevelSpacingF   = 0.5      
      
  res at mpProjection      = "Orthographic"          ; choose projection
  res at mpCenterLonF      = 122.                    ; choose center lon
  res at mpCenterLatF      = 45.                     ; choose center lat
  res at mpPerimOn         = False                   ; turn off box around plo
  res at mpDataBaseVersion = "MediumRes"      
  res at mpOutlineOn       = True      
      
  res at cnFillOn          = True                    ; color plot desired
  res at cnFillPalette     = "BlueDarkRed18"           ; select color map
  res at cnLineLabelsOn    = False                   ; turn off contour line labels
  res at cnLinesOn         = False                   ; turn off contour lines
  res at cnFillDrawOrder   = "PreDraw" 

  res at mpGridAndLimbOn   = True               ; turn on lat/lon grid lines
  res at mpGridMaskMode    = "MaskNotOcean"     ; don't draw over land or
  res at mpFillOn = False                                                ; inland water bodies

;  res at lbLabelFontHeightF  = 0.015                 ; label bar font height
  res at gsnLeftString = ""
  res at gsnRightString = ""
  res at tiMainString       = "Regressed Rainfall-HGT(850hPa)"   ; add a title
;  res at tiMainFontHeightF  = .018                   ; font height

  plot = gsn_csm_contour_map(wks,t,res)

;;************************************************************
;;Add shapefiles
;;************************************************************
  vcres = True
  vcres at vcGlyphStyle               = "LineArrow"
  vcres at vcLineArrowThicknessF      = 1.0
  
  vcres at vcMonoLineArrowColor = True
  
  vcres at vcLineArrowColor           = "black"
  vcres at vcMinDistanceF             = 0.01
  vcres at vcLineArrowHeadMaxSizeF    = 0.025
  vcres at vcRefLengthF               = 0.0250
  vcres at vcRefAnnoOrthogonalPosF    = -1.0 
  vcres at vcRefAnnoArrowLineColor    = "black"
  vcres at vcRefMagnitudeF            = 1.5  
  vcres at vcVectorDrawOrder          = "PostDraw" 
  
  vcres at gsnDraw                    = False
  vcres at gsnFrame                   = False
  
  vector = gsn_csm_vector_scalar(wks,u,v,t,vcres)  
  
  overlay(plot,vector)
  
  draw(plot)
  frame(wks)
  
end
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