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

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 es/s2dv#46 (closed)) 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

Edited Mar 22, 2023 by Eva Rifà