Initial & Boundary Data

Initial & Boundary Data

COSMO-CLM needs initial and boundary data covering a larger area than the domain which should be simulated. The data can be taken e.g. from

• Reanalysis

• Global Climate Models (GCMs)
  

• Regional Climate Models (RCMs)

• COSMO-CLM (in case of double nesting)

A number of meteorological variables are needed as initial and boundary data. These variables are the input for the interpolation programm INT2LM which transfers the data onto the COSMO-CLM grid. However, these data can not be used right away (except the output of a coarser COSMO-CLM simulation), because they are usually provided in different formats and have to be converted to a standard that INT2LM can read (so called "INT2LM ready" data).

Forcing data have to be in netCDF (standard CF-1.0 formatted) or GRIB format. Maximal resolution in time recommended for boundary data is 6 hours. Following Denis et al. (2003) a factor of 12 in the horizontal resolution between the forcing data and the resolution of the regional simulation which should be performed is the maximum. Further information on requirements of the data can be found in Part V of the COSMO documentation.

The preparation of the data for INT2LM is done via so-called converter programs. A list of GCMs for which converter programs already exist is availble here. Several already converted ("INT2LM ready") data sets (e.g. NCEP, ERA and COSMO-CLM-data) are available at the DKRZ. For a complete list and information how the data can be accessed, please visit  https://redc.clm-community.eu/projects/data/wiki/Initial_and_Boundary_Data .