CST_SaveExp: make files saved from Load object to be readable with Start

Hi @erifarov

This issue is for the remaining issues we've detected about CST_SaveExp(). We can improve them after v5.0.0.

• (1) The saved files from Load() cannot be loaded properly by Load() or Start()

It may depend on datasets though. The problematic one identified is system5c3s. With system5_m1, the saved files can be loaded again by both Start() and Load() (Load() cannot load system5_m1 correctly, however. Check https://earth.bsc.es/gitlab/es/s2dv/-/issues/46) I leave the example script in comment below

• (2) The time units should be improved when single_file = TRUE

Since the file has dimensions sdate and ftime, it is not possible to retrieve time values directly. The acceptable solution is to use months as units instead of second/hour since ... for "time" and use year as units for "sdate". The example file with a similar structure is: /esarchive/obs/ukmo/en4-v4.2.2/monitor_dcpp/heatcsum0-300m_en4-v4.2.2_s196011-s202112.nc.

variables:
        float time(time) ;
                time:units = "months" ;
                time:shortname = "time" ;
        float sdate(sdate) ;
                sdate:units = "yr" ;
                sdate:shortname = "sdate" ;

The example in the comment below can generate the file to be improved.

FYI @vagudets

Best,
An-Chi