History of SAO definition
-------------------------
	
Many of the early meetings focused on some basic conventions that pertained
to identifying observed data. Common problems with all types of station data
include station identification and reporting the time of the observation.

To identify fixed location stations, we agreed that the numeric WMO id would  
be the identifier of choice. As mentioned above, data suppliers could add an 
internal id in addition to the WMO id. To fully identify stations, a station 
name, the latitude, longitude and elevation of the station will be required. 

There are two time fields, one as the actual observation time and the
other the nominal time of the observation. In other words, the actual
observation time may be 10 minutes before the hour but the nominal
time of the observation is actually on the hour. Time units should follow
the UDUNITS time convention and the variable, declared as a double.

The actual names chosen for the netCDF variables are up to the
data supplier. The agreement amongst this group is that all the
code that reads in the data will NOT be variable name dependent. Code
will be written generically using the netCDF inquire functions or
will employ some sort of table look-up algorithm. The names I've 
included for illustration purposes were mainly borrowed from the
conventions document to offer somewhat "generic" names for these 
fields. Long names are data supplier defined, but should be included
and descriptive for self-documentation purposes.

Units must be compatible with UDUNITS and consistent for a given 
variable (ie. all temperatures written out in degrees C, even though
they are reported in C or F). That's why the "units" attribute is
critical for numeric variables that may be used in calculations.

These will be the MINIMUM variables required in files used for
surface observation data exchange. Any data supplier can add extra 
variables needed to further identify a station and/or its observations. 


-------------------------------------------------------------------------------
by Susan Jesuroga
for NUWG			nuwg@comet.ucar.edu
updated on October 25, 1993