[Dart-users] change to the default error for MADIS dewpoint obs

[Nancy Collins]

dear darters,

after a presentation and discussion at the last wrf/dart meeting,
i've just committed a change to the dart repository which updates
the DART/observations/obs_error/dewpoint_obs_err_mod.f90 file.

this file sets the default error values used when generating
observation sequence files in the MADIS converters.   after a study
done by so-young ha, it was concluded that the default error
for dewpoint observations was too large.  the dewpoint error is
a function of the temperature and relative humidity errors.
the relative humidity error has been dropped from 10% to 5%,
and the minimum relative humidity value is now threshholded
at 20% instead of 10%.

if you want to maintain your original error values when generating
obs_sequence files from MADIS sources, don't update this file,
or update and then replace these 2 values with the originals.

nancy