Re: Vector plots using ECMWF analysis: Black screen

See examples at:

http://www.ncl.ucar.edu/Applications/

Click "Vectors"

  use the vector resource

  res@vcMinDistanceF = 0.017
  plot = gsn_csm_vector_map(wks,u,v,res)

or, You could plot every N/M-th point

plot = gsn_csm_vector_map(wks,u(::N,::M),v(::N,::M),res)

On 9/13/10 5:55 AM, Christopher Steele wrote:
> Hi
>
> I'm attempting to produce a vector plot of a section of data from ECMWF
> analysis. My script is organised into two sections, the first produces a
> contour plot of wind speed and the second is the vector plot. The
> contour plot works fine but unfortunately the vector plot produces
> almost an entirely black plot. I'm not entirely sure why this is the
> case. Here is the script:
>
>
> ;script to read and plot ECMWF global analysis
> ; November 2008
>
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>
> begin
>
> a = addfile("../../../esscratch/ECMWF_wrf_AN_20060602_1200.nc","r")
>
> ;read in data
> u = a->U_GDS0_HYBL(90,:,:)
> v = a->V_GDS0_HYBL(90,:,:)
> lat2d = a->g0_lat_2
> lon2d = a->g0_lon_3
> wind = (u^2 + v^2)^0.5
> wind@description = "wind speed"
> wind@units = "m/s"
> wind!0 = "lat2d"
> wind!1 = "lon2d"
> wind&lat2d = u&g0_lat_2
> wind&lon2d = u&g0_lon_3
> printVarSummary(u)
> printVarSummary(v)
>
>
> wks = gsn_open_wks("x11","ECMWFanalysis")
> res = True
> res@mpMinLatF = 30
> res@mpMaxLatF = 70
> res@mpMinLonF = -20
> res@mpMaxLonF = 20
> res@mpDataBaseVersion = "Highres"
>
> ;contour options
> opts = res
> opts@cnFillOn = True
> opts@cnLinesOn = False
> opts@gsnSpreadColors = True
> opts@mpLimitMode = "LatLon"
> opts@cnLevelSelectionMode = "ManualLevels"
> opts@cnMinLevelValF = -5
> opts@cnMaxLevelValF = 20
> opts@cnLevelSpacingF = 0.5
> opts@lbLabelAutoStride = True
> plot = gsn_csm_contour_map(wks,wind,opts)
> delete(opts);vector options
> opts = res
> opts@vcRefMagnitudeF = 5.0 ; add a reference vector
> opts@vcRefLengthF = 5 ; what the ref length is
> ;opts@vcGlyphStyle = "CurlyVector" ; turn on curley vectors
> opts@gsnAddCyclic = False
>
>
> plot = gsn_csm_vector_map(wks,u,v,res)
>
> end
>
>
> any help would be very much appreciated
>
> cheers
>
> Chris
>
>
>
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Received on Mon Sep 13 05:13:44 2010