Re: How to use NCL to plot EASE grid vector

Xiucheng,

You have a rather old version of NCL which was released July 2003.
The features you are asking for were added in 2005 or later, I think,
so you should upgrade to the latest NCL.

Please see:

   http://www.ncl.ucar.edu/Download/

for information about getting the latest NCL from the Earth System
Grid (www.earthsystemgrid.org).

--Mary

On Tue, 11 Dec 2007, Xiucheng Wang wrote:

> Hi,everyone,
> I generate a February mean(1979-1999) north polar EASE grid ice motion(data from NSIDC) nc file, then I make use of the following NCL program similar to http://www.ncl.ucar.edu/Applications/Scripts/ease_1.ncl to plot u component.
>
> ;*********************************
> ; iceu.ncl
> ;*********************************
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>
> begin
>
> ;*******************************************
> ;read netCDF file
> ;*******************************************
> a = addfile("icemotion79-99.02.n.NoscalFil.nc","r")
>
> u = a->u
> ; v = a->v
> ;*******************************************
> ; Create plots
> ;*******************************************
>
> wks = gsn_open_wks("ps","iceu")
> gsn_define_colormap(wks,"amwg") ; Change color map
> ; gsn_define_colormap(wks,"BlAqGrYeOrReVi200") ; choose colormap
> ; i = NhlNewColor(wks,0.7,0.7,0.7) ; add gray to colormap
>
> res = True ; Plot modes desired.
> res_at_gsnMaximize = True ; Maximize plot
> res_at_mpFillOn = False
> res_at_gsnSpreadColors = True ; use full range of colormap
> res_at_cnFillOn = True ; color plot desired
> res_at_cnLinesOn = False ; turn off contour lines
> res_at_cnFillMode = "RasterFill" ; turn raster on
> res_at_pmLabelBarWidthF = 0.9 ; make wider
> res_at_pmLabelBarHeightF = 0.1 ; default is taller
> res_at_lbLabelFontHeightF = .018 ; default is HUGE
>
> res_at_cnLevelSelectionMode= "ExplicitLevels" ; set explicit contour levels
> res_at_cnLevels =(/-40,-30,-25,-20,-15,-10,-5,-1 \
> ,0,1,5,10,25,30,40/)
>
> ;************************************************
> ;No georeferencing: simple contour. Draws faster
> ;************************************************
> ; res_at_tiMainString = "gsn_csm_contour"
> ; plot = gsn_csm_contour(wks,snow,res) ; contour, no map
>
> ;*******************************************
> ; georeferencing: plot on polar projection
> ;*******************************************
> ; georeference
> ; v_at_lat2d = a->lat
> ; v_at_lon2d = a->lon
>
> u_at_lat2d = a->lat
> u_at_lon2d = a->lon
>
> res_at_trGridType = "TriangularMesh" ; allow missing coordinates
>
> res_at_gsnPolar = "NH" ; specify the hemisphere
> res_at_mpMinLatF = 45
> res_at_tiMainString = "gsn_csm_contour_map_polar"
>
> plot = gsn_csm_contour_map_polar(wks,u,res)
> ; plot = gsn_csm_contour_map_polar(wks,v,res)
> end
>
> Despite the fact it can generate a plot,the following warning information appears:
> warning:cnFillMode is not a valid resource in iceu_contour at this time
> warning:trGridType is not a valid resource in iceu_contour at this time
>
> why cnFillMode and trGridType not valid at that time? If trGridType is not valid at this time, the plot generated is correct or wrong?
>
> I also try to plot EASE grid ice motion vector with the following NCL program:
> ;*********************************
> ; motion.ncl
> ;*********************************
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>
> begin
>
> ;*******************************************
> ;read netCDF file
> ;*******************************************
> a = addfile("icemotion79-99.02.n.NoscalFil.nc","r")
> u = a->u
> v = a->v
> lat2d = a->lat
> lon2d = a->lon
>
> u_at_lat2d = lat2d
> u_at_lon2d = lon2d
> v_at_lat2d = lat2d
> v_at_lon2d = lon2d
>
> ;*******************************************
> ; Create plots
> ;*******************************************
>
> wks = gsn_open_wks("ps","motion7902n.noscale")
> gsn_define_colormap(wks,"amwg") ; Change color map
>
> res = True ; plot mods desired
> res_at_gsnPolarNH = True ; specify the hemisphere
> res_at_mpMinLatF = 45
>
> res_at_vcRefMagnitudeF = 10 ; vec magnitude
> res_at_vcRefLengthF = 0.04 ; size of ref vector
> res_at_vcMinDistanceF = 0.01 ; thins arrows near pole
> res_at_vcGlyphStyle = "LineArrow" ; curley vectors on
>
> res_at_tiMainString = "NSIDC 79-99 Ice Velocity Field"
> res_at_tiMainFont = 21
> res_at_gsnStringFont = 21
> res_at_gsnLeftString = "February mean"
> res_at_trGridType = "TriangularMesh" ; allow missing coordinates
>
> plot = gsn_csm_vector_map_polar(wks,u,v,res)
>
>
> end
>
> The following warning information appears again.
> warning:trGridType is not a valid resource in motion7902n.noscale_vector at this time
>
> Besides the warning information above, I am either not sure whether the method I plot the EASE grid vector is right or not. I hope some who have processed the EASE grid data give me some advices! Thanks a lot!
>
> my NCL version is NCAR Command Language Version 4.2.0.a030,my OS is IBM AIX 5.11. the necesary files above are attached.
>
>
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Received on Tue Dec 11 2007 - 11:26:42 MST