Problem in writing .ctl file for global GRIB file

Mon Feb 4 03:54:42 EST 2008

Dear GRADS users,
I have a global GRIB file. I would like to write the
.ctl file for plotting it.

I use wgrib to see it structure. Based on the results
I  can write a . ctl file as the following :

dset ^a01150000
index ^a01150000.idx
undef 9.999E+20
title a01150000
dtype grib 41
xdef
ydef
tdef 1 linear 00Z15jan2008 1mo
zdef 10 levels
850 700 600 500 400 300 250 200 150 100
vars 10
HGTprs 10 7,100,0 ** Geopotential height [gpm]
HGTmwl  0 7,6,0 ** max wind level Geopotential height
[gpm]
HGTtrp  0 7,7,0 ** tropopause Geopotential height
[gpm]
RHprs 4 52,100,0 ** Relative humidity [%]
TMPprs 10 11,100,0 ** Temp. [K]
TMPtrp  0 11,7,0 ** tropopause Temp. [K]
UGRDprs 10 33,100,0 ** u wind [m/s]
UGRDmwl  0 33,6,0 ** max wind level u wind [m/s]
VGRDprs 10 34,100,0 ** v wind [m/s]
VGRDmwl  0 34,6,0 ** max wind level v wind [m/s]
ENDVARS

The problem is in writing xdef and ydef : it is global
file :

rec 1:41:date 2008011500 HGT kpds5=7 kpds6=100
kpds7=850 levels=(3,82) grid=41 850 mb 6hr fcst:
  HGT=Geopotential height [gpm]
  timerange 0 P1 6 P2 0 TimeU 1  nx -1 ny 73 GDS grid
0 num_in_ave 0 missing 0
  center 74 subcenter 0 process 45 Table 2
  thinned latlon: lat  -90.000000 to 0.000000 by
1.250000  nxny 3447
          long -30.000000 to 60.000000, 3447 grid pts
 (-1 x 73) scan 64 mode 128 bdsgrid 1
       2    3    5    6    8    9   11   12   14   16
 17   19   20   22   23
      25   26   28   29   30   32   33   35   36   38
 39   40   42   43   44
      45   47   48   49   50   51   52   54   55   56
 57   58   59   60   60
      61   62   63   64   65   65   66   67   67   68
 69   69   70   70   71
      71   71   72   72   72   73   73   73   73   73
 73   73   73
  min/max data 959.999 1580  num bits 10  BDS_Ref
959.999  DecScale 0 BinScale 0

rec 2:4624:date 2008011500 HGT kpds5=7 kpds6=100
kpds7=850 levels=(3,82) grid=42 850 mb 6hr fcst:
  HGT=Geopotential height [gpm]
  timerange 0 P1 6 P2 0 TimeU 1  nx -1 ny 73 GDS grid
0 num_in_ave 0 missing 0
  center 74 subcenter 0 process 45 Table 2
  thinned latlon: lat  -90.000000 to 0.000000 by
1.250000  nxny 3447
          long 60.000000 to 150.000000, 3447 grid pts
 (-1 x 73) scan 64 mode 128 bdsgrid 1
       2    3    5    6    8    9   11   12   14   16
 17   19   20   22   23
      25   26   28   29   30   32   33   35   36   38
 39   40   42   43   44
      45   47   48   49   50   51   52   54   55   56
 57   58   59   60   60
      61   62   63   64   65   65   66   67   67   68
 69   69   70   70   71
      71   71   72   72   72   73   73   73   73   73
 73   73   73
  min/max data 1038 1571  num bits 10  BDS_Ref 1038
DecScale 0 BinScale 0

rec 3:9207:date 2008011500 HGT kpds5=7 kpds6=100
kpds7=850 levels=(3,82) grid=43 850 mb 6hr fcst:
  HGT=Geopotential height [gpm]
  timerange 0 P1 6 P2 0 TimeU 1  nx -1 ny 73 GDS grid
0 num_in_ave 0 missing 0
  center 74 subcenter 0 process 45 Table 2
  thinned latlon: lat  -90.000000 to 0.000000 by
1.250000  nxny 3447
          long 150.000000 to -120.000000, 3447 grid
pts   (-1 x 73) scan 64 mode 128 bdsgrid 1
       2    3    5    6    8    9   11   12   14   16
 17   19   20   22   23
      25   26   28   29   30   32   33   35   36   38
 39   40   42   43   44
      45   47   48   49   50   51   52   54   55   56
 57   58   59   60   60
      61   62   63   64   65   65   66   67   67   68
 69   69   70   70   71
      71   71   72   72   72   73   73   73   73   73
 73   73   73
  min/max data 929.963 1632.96  num bits 10  BDS_Ref
929.963  DecScale 0 BinScale 0

rec 4:13790:date 2008011500 HGT kpds5=7 kpds6=100
kpds7=850 levels=(3,82) grid=44 850 mb 6hr fcst:
  HGT=Geopotential height [gpm]
  timerange 0 P1 6 P2 0 TimeU 1  nx -1 ny 73 GDS grid
0 num_in_ave 0 missing 0
  center 74 subcenter 0 process 45 Table 2
  thinned latlon: lat  -90.000000 to 0.000000 by
1.250000  nxny 3447
          long -120.000000 to -30.000000, 3447 grid
pts   (-1 x 73) scan 64 mode 128 bdsgrid 1
       2    3    5    6    8    9   11   12   14   16
 17   19   20   22   23
      25   26   28   29   30   32   33   35   36   38
 39   40   42   43   44
      45   47   48   49   50   51   52   54   55   56
 57   58   59   60   60
      61   62   63   64   65   65   66   67   67   68
 69   69   70   70   71
      71   71   72   72   72   73   73   73   73   73
 73   73   73
  min/max data 1023.33 1632.33  num bits 10  BDS_Ref
1023.33  DecScale 0 BinScale 0

Above there are 4 first records : lat changes from -90
to 0 by 1.25, lon changes in each record (for example,
in rec 1 : lon -30 60, in rec 2 : lon 60 150, etc),
and nx -1, ny 73, nxny 3447 grid pts.

Then from rec 5 to rec 8 the lat changes from 0 to 90
by 1.25, and the lon changes as in each rec above.

So how to write the xdef and ydef in this case ???
Please help me.
Thank you very much.
Phuong

MS NGUYEN THI MINH PHUONG
National Center for Hydrometeorological Forecasts
Address:     4 DANG THAI THAN, HANOI, VIETNAM,
Email :        ntmphuong at hotmail.com, ntmphuong at yahoo.com.au
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