File formatting

• The output files are written through the NetCDF API
• The NETCDF4 _CLASSIC model will be adopted
• Recommended compression level deflate=6
• Shuffling=True
• Fletcher32=True is strongly recommended
  

File Structure

• Each netCDF4 file contains a single output variable (along with coordinate/grid variables, attributes and other metadata) from a single model and a single simulation (i.e., from a single ensemble member and a single start date)
• There is flexibility in specifying how many time slices (samples) are stored in a single file. A single file can contain all the time-samples for a given variable and climate experiment, or the samples can be distributed in a sequence of files.
• Recommended maximum file size of 4GB

• A file containing a hash created with sha256sum should be created for each file

  sha256sum filename.nc > filename.sha256

File Naming

New proposal (20170419):

OLD PROPOSAL:

<institute>_<stream>_<modeling realm>_<frequency>_<level>_<production date and start date identifier>_<data year><data month><data day>[-<data year><data month><data day>]_<variable MARS name>_<ensemble member>

examples:
egrr_enfh_atmos_day_sfc_201601A_19950417-19950418_ta_r3.nc
egrr_enfh_atmos_month_plev_201601A_199504-199505_ta_r3.nc
 
"201601A" is  a placeholder while a form for representing the model version, production year and startdate is determined:
egrr_enfh_atmos_month_plev_P2016_M1A_S19950401_199504-199505_ta_r3.nc
P=production year
M=model version
S=startdate
e.g. could the filename (alternatively) be something like:

egrr_enfh_atmos_month_plev_S19950401_199504-199505_ta_r3p20160101m411.nc

Metadata

• The metadata is constrained by the CF convention (NetCDF Climate and Forecast (CF) Metadata Convention)
• This is also based on information from the SPECS_standard_output.pdf document, the CMIP5 tables and the Attribute Convention for Data Discovery.
  • Attributes currently are a significantly reduced subset of the SPECS/CMIP5 requirements with minor adaptations