Introduction
Fig1: SMOS Brightness Temperature (K) at 30 (+/-1) degrees of incidence angle and at XX polarisation, on 02 February 2010, plotted from the GRIB file obtained by convertion with the SMOS_BUFR2GRIB software.
The SMOS Near real Time (NRT) product is avaiable available from ESA in BUFR format. The NRT SMOS BUFR files contain a large volume of data, at all incidence angles ranging from 0 to about 60 degrees. The SMOS NRT BUFR data is currently used for the SMOS data monitoring.
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- Second, an interpolation software (scin) is used to interpolate the regular Latitude-Longitude (LL) GRIB file on a regular Gaussian grid if requested. Scin It is available at ECMWF, so at the moment users outside ECMWF can not use it. The SMOS_BUFR2GRIB proposes the option to skip the step2 (conveting the BFR files to a regular LL grid only).
The Figure below shows the SMOS_BUFR2GRIB software organigram.
Fig2: SMOS_BUFR2GRIB Software
The control script is smos_bufr2grib.sh ; When editing the script, the user has to define the input file name and the requested incidence angle(s), angular binning angle, as well as the output grid type (regular Latitude-Longitude or Gaussian reduced) and the resolution. The user also has to choose if he would like to converted only the Alias Free Field of View data (AFOV), or the entire FOV. It is recommended to use the alias free field of view to ensure good data quality. The script launches the metview macro smos_bufr2gribLL.met
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Requested tools:
- Linux or Unix computer
- Metview
- EC-Regrid: ECMWF New interpolation software. Not yet available outside ECMWF, so skip this part if not at ECMWF by puting grid_resol="regular" in smos_bufr2grib.sh
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Download the Software
Control script: smos_bufr2grib.sh
Metview programme: smos_bufr2gribLL.met
Readme file: README
Examples
In these examples the SMOS BUFR file s converted to GRIB on 07 February 2010 at 06 UTC (+/-3h). The input smosbufr is 1.1 Gb. It contains all the SMOS data.
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The two brightness temperature output 0.25x0.25 GRIB files are each 0.208 Mb. The entire output (ten files) is 2Mb:
smosbufr_Faxx_0.25_angle30.grib: Faraday angle for XX polarised data
smosbufr_Fayy_0.25_angle30.grib: Faraday angle for YY polarised data
smosbufr_flagfov5_xx_0.25_angle30.grib: SMOS information flag, bit5 (AFOV), for XX polarised data
smosbufr_flagfov5_yy_0.25_angle30.grib: SMOS inforamtion information flag, bit5 (AFOV), for YY polarised data
smosbufr_snpaxx_0.25_angle30.grib: Snapshot accuracy for XX polarised data
smosbufr_snpayy_0.25_angle30.grib: Snapshot accuracy for YY polarised data
smosbufr_snpqxx_0.25_angle30.grib: Snapshot quality for XX polarised data
smosbufr_snpqyy_0.25_angle30.grib: Snapshot quality for YY polarised data
smosbufr_tbxx_0.25_angle30.grib: Brightness Temperature for XX polarised data
smosbufr_tbyy_0.25_angle30.grib: Brightness Temperature for YY polarised dataThe following figure illustrates the obtained GRIB 0.25x0.25 TB at XX polarisation:
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Example2:
Other options can be selected. In particular if the scin software is available on the user's computer, the SMOS data can be converted on a Gaussian Reduced grid (grid="gaussian" in smos_bufr2grib.sh), which is deirectly comparable to the ECMWF models (IFS, HTESSEL, CMEM) outputs.
Convert SMOS BUFR data for incidence angles of 30 (+/-1) degrees, on a Gaussian T511 grid. Do do so, select the following options in smos_bufr2grib.sh :
bin_angle="1"
reg_grid_resol="0.25"
grid="gaussian"
gr_resol="256" # grid N256 corresponds to T511 (see Gaussian grid )
inputfile="smosbufr"
afov="yes"
for AA in 30
The Gaussian Reduced format output is 0.076 Mb for the TB files, and it is 0.64 Mb for the 10 output files at 30 (+/-1) degrees incidence angle.
GR_N256_smosbufr_Faxx_0.25_angle30.grib: Faraday angle for XX polarised data
GR_N256_smosbufr_Fayy_0.25_angle30.grib: Faraday angle for YY polarised data
GR_N256_smosbufr_flagfov5_xx_0.25_angle30.grib: SMOS information flag, bit5 (AFOV), for XX polarised data
GR_N256_smosbufr_flagfov5_yy_0.25_angle30.grib: SMOS information flag, bit5 (AFOV), for YY polarised data
GR_N256_smosbufr_snpaxx_0.25_angle30.grib: Snapshot accuracy for XX polarised data
GR_N256_smosbufr_snpayy_0.25_angle30.grib: Snapshot accuracy for YY polarised data
GR_N256_smosbufr_snpqxx_0.25_angle30.grib: Snapshot quality for XX polarised data
GR_N256_smosbufr_snpqyy_0.25_angle30.grib: Snapshot quality for YY polarised data
GR_N256_smosbufr_tbxx_0.25_angle30.grib: Brightness Temperature for XX polarised data
GR_N256_smosbufr_tbyy_0.25_angle30.grib: Brightness Temperature for YY polarised data
Fig4: SMOS brightness temperature (K) at XX polatisation on 07 February 2010, on a gaussian Reduced T511 grid, over Europe.
Comments:
The finer the resolution, the larger the grib files are. For example conveted on a regular 0.15x0.15 grid, each TB file is 550 Mb. The map given at the top of this page shows the SMOS data converted on a regular grid at a resolution of 0.15 degrees.