Andrew,
I believe the way you were originally calculating it is the correct way. Here is
the way I do it: (using your .nc file)
a = addfile("pr_wtr.eatm.2002.nc","r")
p_wat = a->pr_wtr ;attributes are copied over to p_wat as well
printVarSummary(p_wat)
pwat = (p_wat*p_wat@scale_factor) + p_wat@add_offset
copy_VarCoords(p_wat,pwat) ;in contributed.ncl, copies Coordinate variables
; from p_wat to pwat
pwat@long_name = p_wat@long_name
pwat@units = p_wat@units
pwat@_FillValue = p_wat@missing_value
delete(p_wat)
printVarSummar(pwat)
print("Min of pwat = "+min(pwat)+", max = "+max(pwat))
Let us know if that doesn't work...
Adam
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>From: Andrew Snyder <asnyder4 AT purdue.edu>
>Date: Tue, 9 Nov 2004 12:54:54 -0500
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>Subject: NCEP/NCAR 4x reanalysis of PW
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>NCL users -
>
>I have been attempting to read in and plot 4x daily NCEP/NCAR
>reanalysis precipitable water data. I found a previous message in this
>list from 2 years ago concerning temperature data, and it was helpful
>in including the add_offset and scale_factor attributes, but the
>numbers still don't make sense. I assume it has something to do with
>the way I am calculating PW using the offset and scale factor, but none
>of my other results make sense either. The values would ideally range
>from ~10 - 60 mm (kg/m2). I've included my script and the output
>below.
>
>Thank you for your help!
>
>********************************************
>
>Andrew Snyder
>Graduate Student
>Dept. of Earth and Atmospheric Sciences
>Purdue University
>
>begin
>
> diri = "./"
> fili = "pr_wtr.eatm.2002.nc"
> f = addfile (diri+fili, "r")
>
> vnam = getfilevarnames (f) ; list of variables that are in file
> print (vnam)
>
> p_wat = (f->pr_wtr)
> p_wat@long_name = "Total Precipitable Water"
> p_wat@units = "mm"
> p_wat@scale_factor = 0.01
> p_wat@add_offset = 277.65
>
> pwat = new ((/dimsizes(p_wat)/),float,1.e+20)
>; pwat = (p_wat*p_wat@scale_factor) + p_wat@add_offset
> pwat = (p_wat@scale_factor * (p_wat@add_offset + p_wat))
> copy_VarMeta (p_wat,pwat)
> delete (p_wat)
>
> lat2d = f->lat ; read 2d latitude grid from file
> lon2d = f->lon ; read 2d longitude grid from file
>
> pwat@lat2d = lat2d
> pwat@lon2d = lon2d
>
> min_pwat = min( pwat )
> max_pwat = max( pwat )
>
> printVarSummary(pwat)
> print ("Minimum PWV = "+min_pwat+" Maximum PWV = "+max_pwat)
> print (pwat(1:4,12:14,121:124))
> nvars = dimsizes (pwat)
> print (nvars)
>
>end
>
>And the important part of the output is as follows:
>
>Variable: pwat
>Type: float
>Total Size: 61390080 bytes
> 15347520 values
>Number of Dimensions: 3
>Dimensions and sizes: [time | 1460] x [lat | 73] x [lon | 144]
>Coordinates:
> time: [17540448.. 0]
> lat: [90..-90]
> lon: [ 0..357.5]
>Number Of Attributes: 3
> lon2d : <ARRAY>
> lat2d : <ARRAY>
> _FillValue : 1e+20
>(0) Minimum PWV = -6.60001 Maximum PWV = 277.65
>
>
>Variable: pwat (subsection)
>Type: float
>Total Size: 192 bytes
> 48 values
>Number of Dimensions: 3
>Dimensions and sizes: [time | 4] x [lat | 3] x [lon | 4]
>Coordinates:
> time: [17540454..17540472]
> lat: [60..55]
> lon: [302.5..310]
>Number Of Attributes: 3
> _FillValue : 1e+20
> lat2d : <ARRAY>
> lon2d : <ARRAY>
>(0,0,0) 8.5
>(0,0,1) 8
>(0,0,2) 7.399994
>(0,0,3) 7.100006
>(0,1,0) 7.799988
>(0,1,1) 6.600006
>(0,1,2) 5.899994
>(0,1,3) 6.200012
>(0,2,0) 5.5
>(0,2,1) 4.700012
>(0,2,2) 4.600006
>(0,2,3) 5.399994
>(1,0,0) 8.899994
>(1,0,1) 8.899994
>(1,0,2) 8.100006
>(1,0,3) 7
>(1,1,0) 7.600006
>(1,1,1) 6.700012
>(1,1,2) 5.899994
>(1,1,3) 6
>(1,2,0) 5.700012
>(1,2,1) 4.899994
>(1,2,2) 4.399994
>(1,2,3) 4.799988
>(2,0,0) 7.899994
>(2,0,1) 7.700012
>(2,0,2) 7.200012
>(2,0,3) 6.399994
>(2,1,0) 7.200012
>(2,1,1) 6
>(2,1,2) 5.200012
>(2,1,3) 5.299988
>(2,2,0) 6.399994
>(2,2,1) 5.200012
>(2,2,2) 4.200012
>(2,2,3) 4.100006
>(3,0,0) 7.600006
>(3,0,1) 7.799988
>(3,0,2) 7.200012
>(3,0,3) 6.200012
>(3,1,0) 7.200012
>(3,1,1) 6.600006
>(3,1,2) 5.899994
>(3,1,3) 5.600006
>(3,2,0) 6.399994
>(3,2,1) 5.899994
>(3,2,2) 5.200012
>(3,2,3) 4.799988
>
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-------------------------------------------------------------
Adam Phillips email: asphilli AT ucar.edu
Climate and Global Dynamics Division tel: (303) 497-1726
National Center for Atmospheric Research fax: (303) 497-1333
P.O. Box 3000
Boulder, CO 80307-3000 http://www.cgd.ucar.edu/~asphilli
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