Re: Plotting temperature using NCEP FNL data

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Wed, 25 Jul 2007 08:45:27 -0600

"I'm not sure exactly what pressure level I am
plotting but I think it is at 700mb"

Level 13 corresponds to 500hPa. That is why there are no positive
temperatures.

Why are you "not sure". You can always print out the levels or use

      ncl_filedump -v lv_ISBL3 fnl_070720_12_00.grb | less

The levels are at the bottom. Subscripts are zero based.

---
The attached script uses NCL's coordinate subscripting
  
    http://www.ncl.ucar.edu/Document/Language/subscript_coord.shtml
---
Also, you can download a mini-language reference manual [pdf] at
   http://www.ncl.ucar.edu/Document/Manuals/
Good luck
James Fishbaugh wrote:
> 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

 lev = 700

 diri = "/project/cas/shea/"
 fnam = "fnl_070720_12_00"
 grb_file = addfile(diri+fnam+".grb","r")

 x = grb_file->TMP_3_ISBL_10({lev},:,:) ; Read temp

 x = x-273.15 ; convert to celsius
 x_at_units = "C" ; update attribute

 wks = gsn_open_wks("x11","T_"+fnam) ; Open a workstation

;gsn_define_colormap(wks,"rainbow") ; Define the colormap
 gsn_define_colormap(wks,"BlAqGrYeOrReVi200") ; Define the colormap

 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

 ; 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 thickness

 res_at_tiMainString = lev+"hPa: "+fnam ; Establish a title
;res_at_gsnCenterString = lev+"hPa: "+fnam ; Establish a title
;res_at_mpDataBaseVersion = "MediumRes" ; Use medium resolution

 res_at_lbOrientation = "vertical" ; Use a vertical label bar

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

end

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Received on Wed Jul 25 2007 - 08:45:27 MDT

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