CDO

Introduction

CM SAF’s climate climate data records are provided in NetCDF (Network Common Data Format) and HDF5 (Hierarchical Data Format, release 5) format. Reasons for selecting these data formats are its high compression efficiency and the features to include several data models and self-describing datasets. Efficient and widely used tools to work with these kinds of data are the “climate data operators” (CDO). CDO is a collection of command line operators that were originally developed for processing and analysis of data produced by climate and numerical weather prediction models (e.g. for file operations, simple statistics, arithmetics, interpolation or the calculation of climate indices). Supported file formats are NetCDF, GRIB and several binary formats. By help of CDO an easy conversion of CM SAF HDF5-files to other formats is possible.

The package was developed at the Max-Planck-Institute for Meteorology and is therefore also available on their web page (https://code.zmaw.de/projects/cdo). With installations in more than 150 groups world-wide, the package is widely established in the climate modelling community. It is typically used in a UNIX/Linux environment.

Processing CM SAF data with CDO

Amongst others, CDO offers opportunities for interpolation to other grid types or the selection of regions. Daily and monthly mean data of CM SAF are provided in equal-area or regular lon-lat projections that are described in the metadata entries of each file. CDO employs this information for spatial operations on the final products. Processing of CM SAF intermediate data on original pixel-resolution is also facilitated when pixel-related geolocation is available (for geostationary as well as polar-orbiting satellites).

Example scripts and data on the use of CDO, including the conversion of the CM SAF HDF-files into NetCDF, the extraction of selected regions and the regridding of data, e.g., onto a regular lon-lat grid, can be downloaded here. These scripts are designed to operate on MS Windows. For Linux/Unix operation systems only small modifications are required
The usage of this tool is at your own risk.

SK / June2020