ncl-plot

This skill provides expert guidance for creating high-quality, publication-ready climate plots using NCL, based on specific user preferences and best practices.

Core Mandates

1. Separate Figures: Always plot spatial maps and time series in separate files. Do not panel them together in a 2-column layout.
2. Panel Layout: Use gsn_panel with a unified label bar at the bottom.
3. Color Bar (Label Bar):
   • Unified: resP@gsnPanelLabelBar = True.
   • Position: Must be moved down to avoid overlap.
     • resP@gsnPanelBottom = 0.2 (Reserve space at bottom).
     • resP@pmLabelBarOrthogonalPosF = -0.02 (Move label bar slightly down, closer to plot).
   • Width: resP@pmLabelBarWidthF = 0.5 (Approx 90% of subplot width).
   • Font: Times-Roman (font_index = 21), size ~0.018.
   • No Title: Usually redundant if units are obvious or in caption. Set resP@lbTitleString = "".
4. Fonts:
   • Use Times-Roman (Index 21) for all text (titles, axes, labels).
   • Standard size: 0.018 (approx 12pt for A4).
5. Contour Maps:
   • No Line Labels: res@cnLineLabelsOn = False.
   • No Info Box: res@cnInfoLabelOn = False.
   • Shading Only: res@cnFillOn = True, res@cnLinesOn = False.
6. Colormaps:
   • SST / Temperature: BlWhRe (Blue-White-Red).
   • Precipitation: precip_diff_12lev (Yellow-White-Green-Blue).

Code Snippet (Panel Resources)

  ; --- Styling Resources (Global) ---
  font_index = 21
  font_height = 0.018 
  
  res_base = True
  res_base@txFontHeightF        = font_height
  res_base@gsnStringFont        = font_index
  res_base@tmXBLabelFont        = font_index
  res_base@tmYLLabelFont        = font_index
  
  ; --- Panel Resources ---
  resP = True
  resP@gsnPanelLabelBar = True 
  resP@lbLabelFont      = font_index
  resP@lbLabelFontHeightF = font_height
  
  ; Color Bar Geometry & Position
  resP@pmLabelBarWidthF = 0.5   ; ~90% of subplot width
  resP@gsnPanelBottom   = 0.20  ; Reserve bottom margin
  resP@pmLabelBarOrthogonalPosF = -0.02 ; Move label bar slightly down (closer to plot)
  
  resP@lbTitleString    = ""    ; No title below color bar

Workflow

1. Preparation: Ensure analysis results (EOF patterns, PCs) are ready (see ncl-analysis).
2. Plot Maps: Generate eof_maps.png using gsn_panel with the settings above.
3. Plot Series: Generate pc_timeseries.png separately. Ensure X-axis shows Years (tmXBMode = "Manual").