[ncl-talk] gsn_csm_contour_map creates a missing value strip near greenwich meridian after automatic grid transformation

[Rashed Mahmood]

Hi Tabish,

Turning on this resource should work: *res at gsnAddCyclic        = False  =>
True  *


Cheers,
Rashed




On Mon, Jul 24, 2023 at 8:11 PM Tabish Ansari via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Hi
>
> I have a CESM global model output where the grid is not centered at 0
> degrees East, i.e., it doesn't span from (-90 to +90 deg) latitude. Instead
> it spands 0-180 deg latitudes. When I use the  gsn_csm_contour_map function
> to create a global contour map, it automatically transforms the grid to one
> that is centered at 0 degrees meridian - which is good, however, it shows a
> strip of missing values (no colors in the contour plot) on the map along
> the meridian. I think the model output has no such missing data over that
> region.
>
> I have attached the plot.
>
> Here's my script:
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> *beginDIR = "/work/users/tan/Hannah-HTAP2data/"f1 =
> addfile("/work/users/tan/Hannah-HTAP2data/NOX_HTAP.cam.h0.2010.nc
> <http://NOX_HTAP.cam.h0.2010.nc>","r") ; BASELINE NOX-TAGGED RUN o3       =
> f1->O3 o3       = 10^9 * o3 o3 at units = "ppb" o3annual = o3(0,:,:) ;
> initializing for coordinate arrays o3annual = dim_avg_n(o3, 0)*
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> *;;;;;GRAPHICAL SETTINGS;;;;;  wks   = gsn_open_wks
> ("png","SurfaceO3_2010")               ; send graphics to png  res
>             = True  res at gsnMaximize         = True    ; Maximize plot in
> frame  res at cnFillOn            = True            ; turn on color
> res at cnLinesOn           = False           ; no contour lines
> res at cnLineLabelsOn      = False             ; turn off contour lines
> res at gsnAddCyclic        = False  res at mpFillOn            = True           ;
> map fill  res at cnFillMode          = "RasterFill"
> res at mpGeophysicalLineThicknessF = 1.0  res at mpDataBaseVersion     =
> "MediumRes"  res at mpOutlineBoundarySets = "Geophysical"
> res at cnLevelSelectionMode  = "ExplicitLevels" ; set explicit contour levels
> o3levels                       = ispan(5,65,5)  res at cnLevels
>  = o3levels  res at cnFillPalette         = "BlAqGrYeOrReVi200"   ; set color
> map  res at tmYLLabelFontHeightF  = 0.012  res at tiMainString     = "Annual avg
> surface O3 for 2010"  plot = gsn_csm_contour_map(wks,o3annual,res)  ;
> create plotend*
>
> Please let me know if this is a known issue and can be avoided/corrected.
>
> Thanks
>
> Tabish
>
> --------------------------------------------------------------------------------------
> Dr Tabish Ansari
> Research Associate
> Air Quality Modelling Group
> Research Institute for Sustainability (RIFS) - Helmholtz Centre Potsdam
> Potsdam, Germany
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