Reading NCAR/NCEP reanalysis grib files

Hi all,

I have downloaded 10m winds (U and V) in grib format and I am having
trouble reading the files.

I have cat'ed both components into a single file. An ultimate goal is
to extract wind information for an arbitrary location and use that
information to build a wind rose.

1) When I try to read in the variables from the file I get an error that
says they don't exist or there is a problem with the file.

;***************************************
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/wind_rose.ncl"
;
; Need the next one for the read functions
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"

;***************************************
begin
;
fname = "10m_Winds/2008-12_10m-wind.grb"
;
;
; Open file to read
  infile = addfile(fname,"r") ; Open GRIB file to read
;
; Fill the U and V arrays
ugrd = infile->UGRD
vgrd = infile->VGRD

usize = dimsizes(ugrd)
print ("usize is " + usize)

end

-----------

This yields:

$ ncl read_reanalysis_windrose.ncl
Copyright (C) 1995-2007 - All Rights Reserved
University Corporation for Atmospheric Research
NCAR Command Language Version 4.3.0
The use of this software is governed by a License Agreement.
See http://www.ncl.ucar.edu/ for more details.
fatal:Either file (infile) isn't defined or variable (UGRD) is not a
variable in the file
fatal:Execute: Error occurred at or near line 26 in file
read_reanalysis_windrose.ncl

----------

wgrib says this is what is in the file:

$ wgrib 10m_Winds/2008-12_10m-wind.grb -v
1:0:D=2008120100:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u wind [m/s]
2:20388:D=2008120106:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u wind
[m/s]
3:40776:D=2008120112:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u wind
[m/s]
4:61164:D=2008120118:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u wind
[m/s]
5:81552:D=2008120200:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u wind
[m/s]
6:101940:D=2008120206:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u
wind [m/s]
7:122328:D=2008120212:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u
wind [m/s]
8:142716:D=2008120218:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u
wind [m/s]
9:163104:D=2008120300:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u
wind [m/s]
10:183492:D=2008120306:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u
wind [m/s]
  <... snip ...>
120:2428428:D=2008123018:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u
wind [m/s]
121:2448816:D=2008123100:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u
wind [m/s]
122:2469204:D=2008123106:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u
wind [m/s]
123:2489592:D=2008123112:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u
wind [m/s]
124:2509980:D=2008123118:UGRD:10 m above gnd:kpds=33,105,10:6hr fcst:"u
wind [m/s]
125:2530368:D=2008120100:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
126:2550756:D=2008120106:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
127:2571144:D=2008120112:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
128:2591532:D=2008120118:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
129:2611920:D=2008120200:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
130:2632308:D=2008120206:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
131:2652696:D=2008120212:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
132:2673084:D=2008120218:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
133:2693472:D=2008120300:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
134:2713860:D=2008120306:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
   <... snip ...>
244:4958796:D=2008123018:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
245:4979184:D=2008123100:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
246:4999572:D=2008123106:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
247:5019960:D=2008123112:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]
248:5040348:D=2008123118:VGRD:10 m above gnd:kpds=34,105,10:6hr fcst:"v
wind [m/s]

------------

Any help in getting past this fundamental point is greatly appreciated.

2) If anyone could offer some code examples that would fill an array of
values (over all [or some] times) from the horizontal grid that are
valid for a given lat/lon that would be really helpful.

3) Are there any built-in functions (or contributed ones) that will
convert my U and V components into Speed and Direction?

Thanks in advance for any help!

Cheers,
Chris Herbster

-- 
Dr. Christopher G. Herbster
Associate Professor
Director of Science and Technology
for the ERAU Weather Center
Applied Aviation Sciences
Embry-Riddle Aeronautical Univ.
600 S. Clyde Morris Blvd.
Daytona Beach, FL 32114-3900
386.226.6444 Office
386.226.6446 Weather Center
http://wx.erau.edu/
Schedule at:  http://wx.erau.edu/faculty/herbster/Schedules/
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