problem to open TRMM 3B42RT 3hr binary files

[Zhong Liu]

Dear Henrique Barbosa,

FYI: The NASA Goddard DISC has made those data GrADS ready,

ftp://disc2.nascom.nasa.gov/data/TRMM/Gridded/3B42RT
ftp://disc2.nascom.nasa.gov/data/TRMM/Gridded/3B40RT
ftp://disc2.nascom.nasa.gov/data/TRMM/Gridded/3B41RT

Regards,

-Zhong

Henrique Barbosa wrote:
> Dear All,
>
> I am trying to open the TRMM 3B42RT 3hr binary
> files available from:
>
> ftp://trmmopen.gsfc.nasa.gov/pub/merged/mergeIRMicro
>
> Its a plain binary file, but it has a 2880 bytes header
> and precipitation, error and source number are
> packed as 2byte-integer, 2byte-integer and 1byte-integer
> respectivelly (see file header below).
>
> I wrote the ctl below but it is not working. Only 0 and -1
> are unpacked correctly... All other values are wrong.
> For instance, 76 (0.76mm/hr) is unpacked by grads
> as 19456 and 162 (1.62mm/hr) is unpacked as -24064.
>
> I can read the data correctly if I open it from a fortran
> program thou. If I use it to write a new binary file
> containing only the rescaled precipitation as real*4,
> than I can access the data correctly from grads.
>
> I would prefer to open the original data instead.
> Any ideas how to fix the ctl?
>
> thanks,
> Henrique
>
> =======GRADS unpacking x F90================
> nx   |  ny | Grads   | F90
> 1261 |  40 |   -1    | -1
> 1261 |  41 |    0    |  0
> 1261 |  60 |   6656  | 26
> 1261 |  61 |   1264  | 44
> 1261 | 403 | -24064  | 162
> 1261 | 404 |  19456  |  76
>
> ==========GRADS VERSION==================
> Config: v1.9b4 32-bit little-endian readline lats printim
> Running on P4 with opensuse 10.1
>
> ===========CTL===========================
> DSET ^mergeIRMicro/2002/3B42RT.2002090100.bin
> UNDEF -31999
> OPTIONS YREV BIG_ENDIAN
> fileheader 2880
> TITLE trmm data
> XDEF 1440  LINEAR    0.125 0.25
> YDEF  480  LINEAR  -59.875 0.25
> ZDEF 1 LEVELS 1 1
> TDEF 1 LINEAR 00Z01SEP2002 3HR
> VARS 3
> prec    0 -1,40,2,-1    prec (mm/hr)
> error   0 -1,40,2,-1    error (mm/hr)
> source  0 -1,40,1       source
> ENDVARS
>
> ===========FILE HEADER====================
> algorithm_ID=3B42RT algorithm_version=01.00
> granule_ID=3B41RT.2002090100.bin header_byte_length=2880
> file_byte_length=(char2880)_header+(int2)x1440x720x2_data+(int1)x1440x720_data
> nominal_YYYYMMDD=20020901 nominal_HHMMSS=000000
> begin_YYYYMMDD=20020831 begin_HHMMSS=223000 end_YYYYMMDD=20020901
> end_HHMMSS=013000 creation_date=20020901 west_boundary=0E
> east_boundary=360E north_boundary=60N south_boundary=60S
> origin=northwest number_of_latitude_bins=480
> number_of_longitude_bins=1440 grid=0.25x0.25_deg_lat/lon
> first_box_center=59.875N,0.125E second_box_center=59.875N,0.375E
> last_box_center=59.875S,359.875E number_of_variables=3
> variable_name=precipitation,precipitation_error,source
> variable_units=mm/hr,mm/hr,source_number variable_scale=100,100,1
> variable_type=signed_integer2,signed_integer2,signed_integer1
> byte_order=big_endian flag_value=-31999
> flag_name=insufficient_observations contact_name=TSDIS_Helpdesk
> contact_address=NASA/GSFC_Code_902_Greenbelt_MD_20771_USA
> contact_telephone=301-614-5184 contact_facsimile=301-614-5575
> contact_email=helpdesk at tsdis.gsfc.nasa.gov
>
>


--
********************************************************************
* Zhong Liu, Ph.D.                     |  zliu at pop600.gsfc.nasa.gov*
* George Mason University and          |                           *
* NASA Goddard Earth Sciences          |  (301) 614-5764 (voice)   *
* Data and Information Services Center |  (301) 614-5268 (fax)     *
* NASA/GSFC, Code 610.2                |                           *
* Greenbelt. MD. 20771  U.S.A.         |                           *
********************************************************************
* For more information about the Goddard DISC and its services:    *
* http://disc.gsfc.nasa.gov/                                       *
********************************************************************