Plotting temperature using NCEP FNL data

Hello,

I am trying to plot temperature contours across the globe for July 20
at 12Z and am getting strange results. The temperatures it is showing
are very cold, barely anything in the world above freezing, which I
know to be incorrect. I'm not sure exactly what pressure level I am
plotting but I think it is at 700mb (I have no idea what indices in
the array correspond to which pressure levels, if you know that I'd
really appreciate it). I found an old posting where someone was
plotting a similar field, and their comments said it was the 700mb
level. Anyway, I am stumped as to why everything is so cold and am
assuming I am plotting the data incorrectly.

Below is my code, however you will most likely need the input data if
you are going to see the results I am seeing (or I can email a
screenshot if you'd prefer). I got it at
http://dss.ucar.edu/datasets/ds083.2/. Please help!

James

load "$NCARG_ROOT/lib/ncarg/nclex/gsun/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"

begin

  grb_file = addfile("../data/fnl_070720_12_00.grb","r")

  x = grb_file->TMP_3_ISBL_10(13,:,:)-273 ; Read in temp at 700mb
level and convert to celsius

  wks = gsn_open_wks("x11","Temperature") ; Open a workstation

  gsn_define_colormap(wks,"rainbow") ; Define the colormap
used for this plot

  res = True ; We are using resources

  res_at_gsnMaximize = True ; Maximize size
  res_at_gsnSpreadColors = True ; Use full range of colormap
  res_at_cnFillOn = True ; Color plot desired
  res_at_cnLinesOn = False ; Turn off contour lines
  res_at_cnLineLabelsOn = False ; Turn off contour labels

  res_at_gsnAddCyclic = True ; This is the entire
world - cyclic data
  res_at_tfDoNDCOverlay = False ; This is NOT a native projection

  ; Change size and location of plot
  res_at_mpShapeMode = "FreeAspect" ; Use the free aspect shape mode
  res_at_vpYF = 0.90 ; Upper right location
  res_at_vpXF = 0.10 ; Lower left location
  res_at_vpWidthF = 0.70 ; Width of plot
  res_at_vpHeightF = 0.70 ; Height of plot

  res_at_mpFillOn = False ; Turn off map fill
  res_at_mpOutlineOn = True ; Turn on the outline of the map
  res_at_mpGeophysicalLineThicknessF = 2.0 ; Increase the
thickness of map border

  res_at_tiMainString = "Temperature (C)" ; Establish a title
  res_at_mpDataBaseVersion = "MediumRes" ; Use medium resolution
coastlines

  res_at_lbOrientation = "vertical" ; Use a vertical label bar

  plot = gsn_csm_contour_map(wks, x, res) ; Plot the data

end
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Received on Wed Jul 25 2007 - 03:29:41 MDT