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How to read SM-DAS-2 Grib files

The SM-DAS-2 product is provided in GRIB-1 format, on a Gaussian grid at the resolution T799, corresponding to N400 (~25 km).

There are several tools available to read grib files. Three applications and examples are provided to read grib files and extract data on specific location (e.g. on validation test sites).

1- Use GRIB API

We recommend to use the GRIB API software to read grib files. GRIB API can be downloaded from the ECMWF GRIB API web page. It needs to be used under Linux or UNIX systems.

For example if your SM-DAS-2 grib file is named SM-DAS-2_2009122700.grib, the command to extract data from the four nearest grid points from latitude YLAT and longitude XLON is:
grib_ls -p step,shortName -l XLAT,XLON SM-DAS-2_2009122700.grib

A more comprehensive script (and readme file) is given here with GRIB API to extract time series over four test sites. The example contains 3 directories:
- grib contains grib files of SM-DAS-2 31 for December 2009 (31 files).
- prog contains the script that needs to be used to extract SM-DAS-2 in acsii over 4 test sites.
- ascii_sites contains the times series exctracted in ascii for the four test sites.
The readme file explains how to use and to modify the script. For any further question concerning this example or on how to read SM-DAS-2, please contact Patricia.Rosnay@ecmwf.int.

2- Use Metview

Metview is also recommended to be used to extract data from grib files, to plot and map data as well as to compute statistics. Metview can be downloaded and installed on Linux and Unix systems from the ECMWF Metview web page.

2.1 Extract time series with Metview:
Metview script is given together with a readme file here to read SM-DAS-2 with Metview and to extract time series over four test sites (provides ascii files).

2.2 Map SM-DAS-2 with Metview:
Metview script is given together with a readme file here to map SM-DAS-2 with Metview (provides png files).

For any further question concerning this example or on how to read or map SM-DAS-2 using Metview, please contact Patricia.Rosnay@ecmwf.int.

3. Using Matlab

It is also possible to read GRIB files using Matlab, which can be used on Unix, Linux and Windows systems. Library can be downloaded from ftp://polar.ncep.noaa.gov/pub/ofs/reference/ (also available in read_grib_1.5.tar.gz) .

In the framework of the H-SAF Visiting Scientist programme, tool to read SM-DAS-2 with Matlab has been

developed by Luca Brocca (Research Institute for Geo-Hydrological Protection National Research Council, Iyaly). It is freely available (example_readgrib.rar).

For any further question on how to read SM-DAS-2 using Matlab, please contact luca.brocca@irpi.cnr.it