Re: Vector plots using ECMWF analysis: Black screen

Hi Chris,

When using the gsn_csm_xxx_map scripts, the land masses are by default filled in gray. If you don't have gray in your current color map, then you will get whatever color NCL deems is the closest match, which appears to be white in your case.

I'm not sure whether you want to not fill the land masses at all, or just have them under the vectors. If you want them under the vectors, then try setting the "mpFillDrawOrder" resource to "PreDraw".

If you don't want any map fill at all, try setting "mpFillOn" = False. This should automatically turn on map outlines.

--Mary

On Sep 14, 2010, at 6:23 AM, Christopher Steele wrote:

> Thanks,
>
> Using the additional opts resource allows me to add additional resources to the basic resource list, so I don't have to repeat myself when producing multiple plots of different types. I did however forget to change opts@vcRefLengthF back to a more sensible value - I was altering it to see if it made any difference to the way that the plot looked, and apparently it didn't. Plotting the N/M-th point however appears to have worked, though the map does not appear in the background. Having said this, whenever I try to overlay the two plots, the land masses appear white. while the wind speeds over the sea remain visible.
>
> I'm not really sure why this is happening
>
> cheers
>
> Chris
>
> On Mon, Sep 13, 2010 at 1:13 PM, Dennis Shea <shea@ucar.edu> wrote:
> 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 Tue Sep 14 09:40:18 2010