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

[Tabish Ansari]

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:











*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)*























*;;;;;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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.ucar.edu/pipermail/ncl-talk/attachments/20230724/af9e8879/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: SurfaceO3_2010.png
Type: image/png
Size: 153151 bytes
Desc: not available
URL: <https://mailman.ucar.edu/pipermail/ncl-talk/attachments/20230724/af9e8879/attachment-0001.png>