Re: Cannot draw vector properly in radar (r,theta) plot

Xiaomin,

You are correct that the issue is you can't draw vectors that are on a 2D grid. This is high on our list of things to add to NCL. Currently, you can only draw vectors that are on a rectilinear grid (one represented by 1D coordinate arrays).

I will add your email to the ticket we have on 2D vectors.

--Mary

On May 7, 2014, at 2:27 AM, Xiaomin Chen <xiaominc@hawaii.edu> wrote:

> Hi, there!
>
> I'm trying to make a X-Y vector plot in polar coordinates (r,theta space) and my data is in corresponding polar coordinates with the size of 101*360 (r*theta).
>
> I've tried to attach the two-dimensional arrays documenting the data position in the catersian corrdinate to attributes "vfYArray" and "vfXArray" , similar to "sfXArray" in scaler field in the NCL radar plot sample. Note that the vfXArray or vfYArray must be two-dimensional when drawing vector in NCL.
>
> I run the ncl script and no error information is reported. However, the x-y coordinate seems not right and there are no Xtick or Ytick shown in the output figure. In addition, the spatial mapping from the data to r-theta coordinate are not right. I've also tried to change both the contour and vector coordinate array to be 2-dimensional, but the result turns out to be a image in a rectangular box (should be a circle shape).
>
> So, does anyone ever succeed to draw a vector plot ( gsn_csm_vector) in radar plot? I'll appreciate that if you can share your code. I guess the problem is in the 2-D coordinate array.
>
> Thanks!
> Xiaomin
>
>
> The code are here:
> ;**************************************************************
> ; radar_5.ncl
> ;
> ; Concepts illustrated:
> ; - Drawing four radar plots in a page, each using different colormap
> ; - Plotting radar (r,theta) data, treat like station data.
> ; - Adding radar grid circles and lines with polylines
> ; - Reading binary data using "cbinread"
> ; Example script to produce plots for a WRF real-data run,
> ; with the ARW coordinate dynamics option.
> ;**************************************************************
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"
> begin
> ;=============== Read Azimutal mean Variables ====================
> ntimes =37
> lm =101
> ln=361 ;azimuthal points
> ;=============================================================
> fout1 = "./ASYM/VT_VR_W_PV_PRECIP_aym.dat"
> setfileoption("bin","ReadByteOrder","BigEndian")
> vta = fbindirread(fout1,0,(/ntimes-1,ln*lm/),"float")
> vra = fbindirread(fout1,1,(/ntimes-1,ln*lm/),"float")
> dbza = fbindirread(fout1,2,(/ntimes-1,ln*lm/),"float")
>
>
> do it =1,ntimes-2
>
> uprime = new((/ln,lm/),"float")
> vprime = new((/ln,lm/),"float")
> x1 = new((/ln,lm/),"float")
> y1 = new((/ln,lm/),"float")
> dr =1.0
> deg2rad = 0.017453292519943
> do tt=0,ln-1 ;theta->from due north
> rad=tt*deg2rad
> sin_=sin(rad)
> cos_=cos(rad)
> do rr=0,lm-1 ;r
> x1(tt,rr)=sin_*(rr*dr)
> y1(tt,rr)=cos_*(rr*dr)
> uprime(tt,rr)=sin_*vra(it,tt*101+rr)-cos_*vta(it,tt*101+rr)
> vprime(tt,rr)=sin_*vta(it,tt*101+rr)+cos_*vra(it,tt*101+rr)
> end do
> end do
>
> ; Plotting options for Wind Vectors
> type = "x11"
> ; type = "pdf"
> wks=gsn_open_wks(type,"Asy_Plane_panels")
> vres = True
> vres@gsnDraw = False
> vres@gsnFrame = False
> ;---Set coordinate arrays
> vres@vfXArray = x1 ;Vector Field Attribute
> vres@vfYArray = y1
> vres@gsnRightString = ""
> vres@gsnLeftString = ""
> vres@vcGlyphStyle = "LineArrow" ;Set the type of Vector
> vres@vcLineArrowThicknessF = 1.5
> vres@vcRefMagnitudeF = 15.0
> vres@vcRefLengthF = 0.045
> ;============= Reference Bar Setting =======================
> vres@vcRefAnnoOrthogonalPosF =-0.22 ;Reference Bar position Vertical
> vres@vcRefAnnoParallelPosF = 0.997 ;Reference Bar horizontal position
> vres@vcRefAnnoFontHeightF = 0.015
> ;========================================================
> vres@vcMinDistanceF = 0.017
>
> vector = gsn_csm_vector(wks,uprime,vprime,vres)
>
> ;========= Draw DBZ contour ==========================
> res = True
> res@gsnDraw = False
> res@gsnFrame = False
> res@gsnMaximize = True
>
> res@cnFillOn = True
> res@cnLinesOn = False
> ; res@cnFillMode = "RasterFill"
> ; res@gsnSpreadColors = True
> res@cnLevelSelectionMode = "ManualLevels"
>
> res@lbOrientation = "Vertical"
> res@lbRasterFillOn = False
> ; res@lbBoxLinesOn = False
>
> ;---------read data, (ln,lm) means (theta,r) ->(361,101)--------------
> ;-------------make the 1D XArray and YArray------------------------
> x = new(ln*lm,"float")
> y = new(ln*lm,"float")
> deg2rad = 0.017453292519943
> do tt=0,ln-1 ;theta->from due north
> rad=tt*deg2rad
> sin_=sin(rad)
> cos_=cos(rad)
> do rr=0,lm-1 ;r
> x(tt*101+rr)=sin_*rr*dr
> y(tt*101+rr)=cos_*rr*dr
> end do
> end do
>
> ;---Set coordinate arrays
> res@sfXArray = x
> res@sfYArray = y
> ;----ploting with local resources and colormap for each 1 of 4--------
> ; ------ Pressure anomaly'
> res@cnFillDrawOrder = "Predraw"
> res@gsnLeftString = "REF"
> res@gsnRightString = "dBz"
> res@cnFillPalette = "radar"
> ; res@cnSpanFillPalette = True
> res@cnMinLevelValF = -9.
> res@cnMaxLevelValF =4.
> res@cnLevelSpacingF = 1.
>
> plot = gsn_csm_contour(wks,dbza(it,:),res)
>
>
> overlay(plot,vector)
>
> draw(plot)
> frame(wks)
>
> end do
> end
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Received on Fri May 9 11:55:21 2014