[MITgcm-support] some changes in default parameter value

[Jean-Michel Campin]

Hi,

There has been some default parameter changes on Monday Feb 23,
shortly before checkpoint65j (from today, Feb 25).
You may want to pay attention to these changes if you are relying on one
of those default and are going to update your MITgcm code.

1) the default value for salinity (background) vertical diffusivity
 is now equal to the temperature (background) vertical diffusivity
 (was previously zero by default).
 This change was motivated by pkg/ptracers default (background) vertical
 diffusivity which is set to salinity (background) vertical diffusivity.

2) by default, the NetCDF pickup files are not used (pickup_write_mnc=.FALSE.
  pickup_read_mnc=.FALSE.); previously, when pkg/mnc was used,
  these 2 logical parameters were set to TRUE by default.
  Recently, several users reported problems with MNC pickup files implementation
  and since there is no strong reason not to use plain binary pickup files
  (from pkg/mdsio), the default setting was changed accordingly.

And just as a reminder, in case someone is getting confused by what/when
code modification occurs, all major (and even some minor) code changes
are documented in MITgcm/doc/tag_index.

Cheers,
Jean-Michel