CDO

Hello cdo users,

I am having problems converting a GrADs ctl GRIB data file to NetCDF format. From the Data Integration and Analysis System, I downloaded 6-hourly JRA-55 reanalysis data for an entire month. It downloads in the form of a DAT file and there is a supporting GrADs ctl file that says that the data type is in GRIB format.

The contents of the anl_surf.ctl file is as follows:

dset ^anl_surf.%y4%m2%d2%h2
index ^anl_surf.idx
undef 9.999E+20
title anl_surf

• produced by grib2ctl v0.9.12.5p41
  dtype grib 255
  options template
  ydef 320 levels
  -89.570 -89.013 -88.453 -87.892 -87.331 -86.769 -86.208 -85.647 -85.085 -84.523
  -83.962 -83.400 -82.839 -82.277 -81.716 -81.154 -80.592 -80.031 -79.469 -78.908
  -78.346 -77.784 -77.223 -76.661 -76.100 -75.538 -74.976 -74.415 -73.853 -73.291
  -72.730 -72.168 -71.607 -71.045 -70.483 -69.922 -69.360 -68.799 -68.237 -67.675
  -67.114 -66.552 -65.990 -65.429 -64.867 -64.306 -63.744 -63.182 -62.621 -62.059
  -61.498 -60.936 -60.374 -59.813 -59.251 -58.689 -58.128 -57.566 -57.005 -56.443
  -55.881 -55.320 -54.758 -54.196 -53.635 -53.073 -52.512 -51.950 -51.388 -50.827
  -50.265 -49.704 -49.142 -48.580 -48.019 -47.457 -46.895 -46.334 -45.772 -45.211
  -44.649 -44.087 -43.526 -42.964 -42.402 -41.841 -41.279 -40.718 -40.156 -39.594
  -39.033 -38.471 -37.909 -37.348 -36.786 -36.225 -35.663 -35.101 -34.540 -33.978
  -33.416 -32.855 -32.293 -31.732 -31.170 -30.608 -30.047 -29.485 -28.924 -28.362
  -27.800 -27.239 -26.677 -26.115 -25.554 -24.992 -24.431 -23.869 -23.307 -22.746
  -22.184 -21.622 -21.061 -20.499 -19.938 -19.376 -18.814 -18.253 -17.691 -17.129
  -16.568 -16.006 -15.445 -14.883 -14.321 -13.760 -13.198 -12.636 -12.075 -11.513
  -10.952 -10.390 -9.828 -9.267 -8.705 -8.144 -7.582 -7.020 -6.459 -5.897
  -5.335 -4.774 -4.212 -3.651 -3.089 -2.527 -1.966 -1.404 -0.842 -0.281
  0.281 0.842 1.404 1.966 2.527 3.089 3.651 4.212 4.774 5.335
  5.897 6.459 7.020 7.582 8.144 8.705 9.267 9.828 10.390 10.952
  11.513 12.075 12.636 13.198 13.760 14.321 14.883 15.445 16.006 16.568
  17.129 17.691 18.253 18.814 19.376 19.938 20.499 21.061 21.622 22.184
  22.746 23.307 23.869 24.431 24.992 25.554 26.115 26.677 27.239 27.800
  28.362 28.924 29.485 30.047 30.608 31.170 31.732 32.293 32.855 33.416
  33.978 34.540 35.101 35.663 36.225 36.786 37.348 37.909 38.471 39.033
  39.594 40.156 40.718 41.279 41.841 42.402 42.964 43.526 44.087 44.649
  45.211 45.772 46.334 46.895 47.457 48.019 48.580 49.142 49.704 50.265
  50.827 51.388 51.950 52.512 53.073 53.635 54.196 54.758 55.320 55.881
  56.443 57.005 57.566 58.128 58.689 59.251 59.813 60.374 60.936 61.498
  62.059 62.621 63.182 63.744 64.306 64.867 65.429 65.990 66.552 67.114
  67.675 68.237 68.799 69.360 69.922 70.483 71.045 71.607 72.168 72.730
  73.291 73.853 74.415 74.976 75.538 76.100 76.661 77.223 77.784 78.346
  78.908 79.469 80.031 80.592 81.154 81.716 82.277 82.839 83.400 83.962
  84.523 85.085 85.647 86.208 86.769 87.331 87.892 88.453 89.013 89.570
  xdef 640 linear 0.000000 0.562500
  pdef 157792 1 file 1 stream binary-big ^TL319.pdef
  tdef 120 linear 00Z01Apr1958 6hr
  zdef 1 linear 1 1
  vars 7
  POTsfc 0 13,1,0 * surface Potential temperature [K]
  PRESsfc 0 1,1,0 * surface Pressure [Pa]
  RH2m 0 52,105,2 * 2 m above ground Relative humidity [%]
  SPFH2m 0 51,105,2 * 2 m above ground Specific humidity [kg/kg]
  TMP2m 0 11,105,2 * 2 m above ground Temperature [K]
  UGRD10m 0 33,105,10 * 10 m above ground u-component of wind [m/s]
  VGRD10m 0 34,105,10 ** 10 m above ground v-component of wind [m/s]
  ENDVARS

Using someone's answer from a similarly asked question I used the command:
cdo -f nc import_binary anl_surf.ctl anl_surf.nc

But I receive the following error:

Open Error: Unknown keyword in description file
--> The invalid description file record is:
--> index ^anl_surf.idx
The data file was not opened.

cdo import_binary (Abort): Open failed!

I found out from another forum post that this error is a result of the fact that the INDEX component is not supported by CDO and the import_binary operator does not support the GRIB format.

Does anyone know if there is an operator that supports converting a GrADS ctl file with data in GRIB format to a NetCDF. Unfortunately, I cannot download this data directly in the GRIB format, only in DAT format. Any help is appreciated, thank you!