[ncl-talk] draw a cross section

[靳茜芃]

Hello Everyone I use ncl 6.6.2 when I deal with wrfout_* files  generated by WRF, I have this problem: I want to draw a cross section of the potential temperature between any two points (longitude and latitude). I have drawn a figure based on the example of "http://www.ncl.ucar.edu/applications/scripts/wrf'interp'3.ncl"（wrf_user_vert_cross）. But there is no value below 200m in the figure： Here is  my code:;----------------------------------------------------------------------
; wrf_interp_3.ncl
;----------------------------------------------------------------------
; Concepts illustrated:
;   - Interpolating a vertical cross-section from a 3D WRF-ARW field.
;----------------------------------------------------------------------
; wrf_user_vert_cross and wrf_user_interp_level replace the 
; deprecated wrf_user_intrp3d function. 
;
; NCL V6.6.0 or higher is required to run this example.
;----------------------------------------------------------------------

begin
  filename = "/home/jxp/wrfout_d02_2017120215"
  a = addfile(filename,"r")
  z    = wrf_user_getvar(a, "z",0) 
  dim  = dimsizes(z)
  all_n=dim(0) ;time
  all_k=dim(1) ;south-north
  all_j=dim(2) ;west-east

       
  hgt0  = wrf_user_getvar(a,"ter",0)

  zag0=new((/all_n,all_k,all_j/),"float")  ;z above ground
  hgt2=new((/all_n,all_k,all_j/),"float") do n=0,all_n-1 hgt2(n,:,:)=hgt0 end do zag0  = z-hgt2 printVarSummary(zag0)
  th   = wrf_user_getvar(a, "th",0)     ; theta k
  loc = wrf_user_ll_to_ij(a,116.21,39.28,True)
  print(th(:,loc(1),loc(0)))
  print(zag0(:,loc(1),loc(0)))
  lats = wrf_user_getvar(a, "lat",0)
  lons = wrf_user_getvar(a, "lon",0)

  start_lat       = 38.625
  end_lat         = 39.982
  start_lon       = 116.61
  end_lon         = 115.782
  opt             = True
  opt at latlon      = True
  opt at linecoords  = True
  opt at file_handle = a
  th_latlon       = wrf_user_vert_cross(th,zag0,(/start_lon,start_lat,end_lon,end_lat/),opt)

;  printVarSummary(th)          ; [bottom_top | 31] x [south_north | 546] x [west_east | 480]
;  printVarSummary(th_latlon)   ; [vertical | 100] x [cross_line_idx | 171]

  wks = gsn_open_wks("png","wrf_interp2017120215")

  res                      = True
  res at gsnMaximize          = True     ; maximize plot in frame
  res at cnFillOn             = True     ; turn on contour fill
  res at cnLinesOn            = True    ; turn off contour lines
  res at cnLineLabelsOn       = True    ; turn off line labels
  res at cnLevelSelectionMode = "ManualLevels"
  res at cnMinLevelValF = 276
  res at cnMaxLevelValF = 285
  res at cnLevelSpacingF = 0.5
  
  res at lbOrientation        = "Vertical"
  res at lbLabelFontHeightF   = 0.01
  res at tiMainString         = "Cross section from ("+start_lat+","+start_lon+ \
                                           ") to ("+end_lat + ","+end_lon+")"
  res at gsnStringFontHeightF = 0.015
  res at tmXBLabelFontHeightF = 0.01
  res at tmXBLabelAngleF      = 45.
  res at tmYLMode          = "Explicit"
  res at tmYLLabels        = (/0, 200, 400, 600, 800, 1000/)
  res at trYMinF = 0;ymin
  res at trYMaxF = 1000;ymax
;--Explicitly set lat/lon labels for X axis
  xvalues = ispan(0,dimsizes(th_latlon(0,:))-1,1)
  ll_step = 15                                       ; step interval for tickmarks
  res at tmXBMode          = "Explicit"
  res at tmXBValues        = xvalues(::ll_step)
  res at tmXBLabels        = sprintf("%6.2f",th_latlon at lats(::ll_step)) + "~S~o~N~N~C~" + \
                          sprintf("%6.2f",th_latlon at lons(::ll_step)) + "~S~o~N~E"

                             
  plot = gsn_csm_contour(wks,th_latlon,res)

end
What's wrong with my code? Why there is no value below 200m in the figure？Thank you！Xipeng Jin
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