;----------------------------------------------------------------------
; vector_4.ncl
;
; Concepts illustrated:
;   - Coloring vectors based on temperature data
;   - Drawing curly vectors
;   - Thinning vectors using a minimum distance resource
;   - Changing the length of the smallest vector as a fraction of the reference vector
;----------------------------------------------------------------------

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

begin

;---Read in netCDF file
  a = addfile("uwnd.mon.mean.nc","r")
   b = addfile("vwnd.mon.mean.nc","r")
  

;---Read in zonal [u] and meridional [v] winds 
  u = a->uwnd 
  v = b->vwnd
  ;u1 = u(:,:,5) ;dimension reduction
  ;v1 = v(:,5,:);dimension reduction
 wspd = u
  wspd = (/ sqrt(u^2+v^2) /)

;---Create plot
  wks = gsn_open_wks("x11","vector")                       ; open a ps file

  cmap = read_colormap_file("BlAqGrYeOrReVi200")

  vcres                     = True      ; plot mods desired
  vcres@lbLabelStride       = 2         ; plot every other colar bar label
  vcres@vcRefMagnitudeF         = 5.0              ; make vectors larger
  vcres@vcRefLengthF            = 0.050            ; ref vec length
  vcres@vcGlyphStyle            = "CurlyVector"    ; turn on curly vectors
  vcres@vcMinDistanceF          = 0.017            ; thin out vectors
  vcres@vcLevelPalette      = cmap(6:193,:)

  vcres@tiMainString            = "Vectors colored by a scalar map"

  plot=gsn_csm_vector_scalar_map_ce(wks,u,v,wspd,vcres)  ; create plot



end