Time variable/dimension missing in NetCDF4-CF files

snap
#1

We use a GPT script to do various processing steps, subset, and write the output to NetCDF4-CF for Sentinel-1, Sentinel-2, and RCM imagery. We have noticed that the time information is not stored in the NetCDF in a compliant way. Normally the time would be included as an additional variable/dimension in the NetCDF, e.g.:

double time(time) ;
time:long_name = “time” ;
time:units = “days since 1990-1-1 0:0:0” ;

I do see that time information in the NetCDFs produced by SNAP is stored in global attributes as “start_date” and “stop_date”. Unfortunately since this does not meet NetCDF compliancy requirements, other software packages don’t find this information. Is there any plan to make the NetCDF time component compliant by e.g. including the start_date as a separate “time” variable/dimension? If not, can this be considered for future versions of SNAP?

#2

In my experience, NetCDF4-CF (CF means Climate and Forecast Metadata Conventions) files that contain data for a single time rarely include a time dimension. You can use CDO to add time “points”, but form many data sets the arrays represent some statistic for a time interval. The CF documents include examples of time interval data, but CDO doesn’t handle that case. In practice, given the current support for time in software that can read NetCDF4-CF files, it is probably better to omit the time dimension.