SMOS .dbl to NetCDF conversion (resolution & grid)

Optical Toolbox
#1

Dear all,
I am trying to convert SMOS data from .dbl to a netCDF format (to be opened in Matlab) with the export tool in S3tbx.

Export_SMOS_EE_to_NetCDF.png961×776 144 KB
The problem is that I create a .nc file in a column format and not in a gridded format (all latitudes are contained in a column, etc for other variables). There is some workaround to read a .nc file with data in column with matlab, but to use them : I need to know how many rows/columns a grid is supposed to have, or have a constant resolution (which seems not to be the case after the conversion to .nc format). Is there a way to create a gridded .nc file with S3tbx or to determine the number of rows/columns that should contain the grid in order to read the data in Matlab?
I thank you very much for your time!

#2

Dear Nathalie,

the target format of the SMOS NetCDF exporter is a file format that has been designed to be close to the original data format of the SMOS data. These acquisitions are not located on one of the usual rasters, instead the data is located on hexagonal cells defined by the ISEA raster. Further reading on SMOS data and the ISEA 4H9 raster: https://www.researchgate.net/publication/4110843_Processing_of_SMOS_level_1c_data_onto_a_Discrete_Global_Grid

As a workaround, I suggest that you export the SMOS data to NetCDF4-CF. This export projects the cells onto plate-carre raster and exports the raster to NetCDF4. Because the projection always covers the globe, the target file will contain a lot of “no-data” pixels. You can either accept this and rely on NetCDF4 compression or you export only the geographical subset of your choice.

Hope this helps a bit,

Tom