[gradsusr] OMI .he5 File

[James E. Johnson]

This is a control file that will work with the full unsubsetted OMI Level-2G NO2 file:
 
DSET ^OMI-Aura_L2G-OMNO2G_2006m0601_v003-2012m0714t200707.he5
DTYPE hdf5_grid
TITLE OMI NO2 L2G Monthly Nitrogen Dioxide Column Density Collection
UNDEF -1.2676506E30 _FillValue
XDEF 1440 linear -180 0.25
YDEF 720 linear -90 0.25
ZDEF 15 levels 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
TDEF 1 linear 1jun2006 1dy
VARS 2
/HDFEOS/GRIDS/ColumnAmountNO2/Data~Fields/ColumnAmountNO2Trop=>no2trop 15 z,y,x ColumnAmountNO2Trop
/HDFEOS/GRIDS/ColumnAmountNO2/Data~Fields/ColumnAmountNO2=>no2         15 z,y,x ColumnAmountNO2
ENDVARS


I see that you downloaded a subsetted file, you would need to modify the XDEF
and YDEF to the particular criteria that you used. Second you need to read up
on the data product before you use it. These data are 0.25 degree resolution,
but from your control file you tried to set it to 1.0 degree, this is incorrect.
Also, this is not really a gridded data product. It is instead a 24-hour period
(00:00 to 23:59) of Level-2 swath data arranged in an HDF-EOS5 grid structure,
where the third dimenison (called nCandidates in the file) does not represent
a physical dimension, rather it is a convenience dimenison for packing multiple
Level-2 pixels (up to maximum of 15) into a single grid cell due to overlap.
If your goal is to grid the data you would need to devise a gridding scheme
(average, best pixel, etc.) reducing/eliminating the third dimension so you
could use the data in GrADS (which is designed for 'gridded data').

------------------------------------------------------------------------------
| James E. Johnson                   | address:                              |
| Wyle Information Systems, Inc.     |  NASA Goddard Earth Sciences          |
| e-mail: james.johnson at nasa.gov     |  Data and Information Services Center |
| phone:  301-614-5121               |  Code 610.2, Bldg 32, Room S130G      |
| fax:    301-614-5268               |  Greenbelt, MD  20771                 |
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On Monday, November 19, 2012 12:02:14 pm Jonathan Wynn Smith wrote:
> Hello,
> 
> I get the following error message when opening an OMI .he5 file for
> nitrogen dioxide.  I have included the Descriptor file iat the bottom of
> this email.  What is causing this HDF-DIAG error and what can I do to fix
> it?:
> 
> OMINO2G_hdf.gs
> No hardcopy metafile open
> All files closed; all defined objects released;
> All GrADS attributes have been reinitialized
> HDF5-DIAG: Error detected in HDF5 (1.8.7) thread 0:
>   #000: H5Dio.c line 153 in H5Dread(): selection+offset not within extent
>      major: Dataspace
>     minor: Out of range
> HDF5 read error for float data
> Data Request Error:  Error for variable 'no2col'
>   Error ocurred at column 1
> DISPLAY error:  Invalid expression
>   Expression = no2col
>  Cannot plot color bar: No shading information
> Hardcopy output file is closed
> ga->
> 
> 
> Control File
> DSET
> ^Desktop/OMI_NO2_Data/OMI-Aura_L2G-OMNO2G_2006m0601_v003-2012m0714t200707.
> SUB.he5 DTYPE hdf5_grid
>  TITLE OMI NO2 L2G Monthly Nitrogen Dioxide Column Density Collection
> UNDEF -1.2676506E30 _FillValue
> XDEF 283 linear -35 1.0
> YDEF 161 linear -20 1.0
> ZDEF 15 levels 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
>  *ZDEF 15 levels 825.402, 681.291, 464.16, 316.227, 215.444, 146.779, 100,
> 68.1295, 46.4158, 31.6229, 21.5443, 14.678, 10, 6.81291, 4.6416 TDEF 1
> linear 1jun2006 1dy
> VARS 2
> /HDFEOS/GRIDS/ColumnAmountNO2/Data~Fields/ColumnAmountNO2Trop=>no2 15 x,y,z
> ColumnAmountNO2Trop
> /HDFEOS/GRIDS/ColumnAmountNO2/Data~Fields/ColumnAmountNO2=>no2col 0 x,y
> ColumnAmountNO2 */HDFEOS/GRIDS/ColumnAmountNO2/Data~Fields/Longitude=>LON
> x Longitude */HDFEOS/GRIDS/ColumnAmountNO2/Data~Fields/Latitude=>LAT y
> Latitude