[ncl-talk] Vectorplot: Not getting curly vectors

[Dave Allured - NOAA Affiliate]

Those really are curly vectors.  However, there is a mistake in your plot
data.  In the second line here, you are subsetting u_corr when I think you
want v_corr.  This has the remarkable effect of making the vectors pointing
always to or from the same direction.  This results in zero apparent
divergence, thus the vectors do not curl.

    U = u_corr(0,2,0:260,1160:1438)
    V = u_corr(0,2,0:260,1160:1438)


On Sun, Feb 16, 2020 at 5:42 PM Tabish Ansari via ncl-talk <
ncl-talk at ucar.edu> wrote:

> Hi
>
> I'm trying to make a wind vector plot using 0.25deg resolution gridded
> data. I want to draw curly vectors but despite using "vecres at vcGlyphStyle
>     = "CurlyVector"  option, I'm getting straight vectors (see attached
> plot). Could you please point out what is wrong here?
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> Here's my script:
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> *begin;READING WIND COMPONENTS OFF THE FILEa =
> addfile("/ichec/work/ngear013c/ERA5_uvw_1000-975-950hpa_27-30Jun2011.nc","r")u
> = a->uv = a->v;APPLYING CORRECTIONS AND OFFSETS TO GET REAL VALUESu_corr =
> (/0.0012*u/)u_corr = (/u_corr-0.6127/)v_corr = (/0.0012*v/)v_corr =
> (/v_corr-1.7441/);PRESERVING VARIABLE METADATA FOR CORRECTED
> ARRAYScopy_VarMeta(u,u_corr)copy_VarMeta(v,v_corr)print("Transformed");PRINTING
> MIN AND MAX VALUES FROM THE CORRECTED ARRAYS TO CONFIRM IF THE RANGE IS
> REALISTICprintMinMax(u_corr(:,0,:,:),1) ;
> 950HPAprintMinMax(u_corr(:,1,:,:),1) ; 975
> HPAprintMinMax(u_corr(:,2,:,:),1) ; 1000 HPA;READING 1000HPA WINDS FOR THE
> FIRST HOUR AND CROPPING OVER GREENLAND-IRELAND REGIONU =
> u_corr(0,2,0:260,1160:1438)V = u_corr(0,2,0:260,1160:1438)speed =
> sqrt(U^2+V^2)copy_VarCoords(U,speed)      ;OPEN A WORKSTATION  wks   =
> gsn_open_wks ("pdf", "windvectors-Oct2011")       ; send graphics to PNG
> file  res                     = True  res at gsnDraw             = False
>     ; don't draw  res at gsnFrame            = False           ; don't advance
> frame  res at gsnMaximize         = True    ; Maximize plot in frame
> res at cnFillOn            = True            ; turn on color
> res at cnFillPalette       = "gui_default"   ; set color map  res at cnLinesOn
>         = False           ; no contour lines  res at gsnLeftString       =
> "Wind Speed"         ; change left string  res at gsnRightString      =
> U at units         ; assign right string  res at gsnAddCyclic        = False
> res at mpFillOn            = False           ; no map fill
> res at mpGeophysicalLineThicknessF = 2.0  res at mpDataBaseVersion   =
> "MediumRes" ; SELECTING THE GREENLAND-IRELAND SUBREGION FROM THE MAP
> res at mpMinLonF            =  -70.                 res at mpMaxLonF            =
>  0.  res at mpMinLatF            =  30.   res at mpMaxLatF            =  90.
> vecres                  = True            ; vector only resources
> vecres at gsnDraw          = False           ; don't draw  vecres at gsnFrame
>     = False           ; don't advance frame  vecres at vcGlyphStyle     =
> "CurlyVector"   ; curly vectors  vecres at vcRefMagnitudeF  = 20
>  ; define vector ref mag  vecres at vcRefLengthF     = 0.045           ;
> define length of vec ref  vecres at gsnRightString   = " "             ; turn
> off right string  vecres at gsnLeftString    = " "             ; turn off left
> string  vecres at tiXAxisString    = " "             ; turn off axis label
> vecres at vcRefAnnoOrthogonalPosF = -.35    ; move ref vector into plot  plotA
>   = gsn_csm_contour_map_ce(wks,speed(:,:),res)  plotB   =
> gsn_csm_vector(wks,U(::10,::10),V(::10,::10),vecres)  overlay(plotA,plotB)
>                      ; overlaying plotB over plotAdraw(plotA)frame(wks)end*
> ############################################################
>
> Thanks in advance.
>
> Tabish
>
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> *Tabish U Ansari*
>
> *Postdoctoral Researcher *
>
> *Centre for Climate and Air Pollution Studies (C-CAPS)*
> *School of Physics, NUI-Galway**, Ireland*
> *ResearchGate: https://www.researchgate.net/profile/Tabish_Ansari
> <https://www.researchgate.net/profile/Tabish_Ansari>*
>
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