Enable point observation data types to be specified by a string rather than a GRIB code.

[dwfncar]

As of MET 5.2, the Point-Stat and Ensemble-Stat tools filter observations by following GRIB1 conventions. The point observations in these tools should be specified following the GRIB1 conventions.

However limiting ourselves to the 255 GRIB1 codes has become problematic as we apply MET to a wider array of data... including cloud aerosols and satellite observations (e.g. cloud lidar like Calipso).

Suggest that we generalize the logic throughout MET to let observations be named following GRIB1 conventions... or named using strings.

Need to work out several details here. Ideally, we'd only need to update ascii2nc, point_stat, ensemble_stat, and library code to allow for a string in the GRIB code column. And we'd leave pb2nc and madis2nc untouched.

This functionality would be useful for the AF CAF project. Having lidar2nc write define observations as strings rather than GRIB codes would be more convenient. [MET-745] created by johnhg

[dwfncar]

This functionality is needed for generalized PREPBUFR and BUFR file support.

netcdf sample_pb {
dimensions:
        mxstr = 16 ;
        hdr_arr_len = 3 ;
        obs_arr_len = 5 ;
        nobs = UNLIMITED ; // (87753 currently)
        nhdr = 9396 ;
        nvar = 25 ;
variables:
...
        char var_name(nvar, mxstr) ;

by johnhg

[dwfncar]

AOP2017 VX1 NOAA by jensen

[dwfncar]

• Added "obs_var_num" dimension and "obs_var" variable.
  
• obs_arr[1] contains the index of obs_var variable. (starts from 0, not 1)
      + ascii2nc: If the ascii input contains non-numeric name at the GRIB code column
      + pb2nc: -use_var_id argument is given or the config file contains "use_var_id = true;"
  
• If NetCDF has the global attribute "use_var_id", it compairs the varibale name instead of GRIB code
  

dimensions:
        obs_var_num = 9 ;
variables:
        char obs_var(obs_var_num, mxstr) ;
                obs_var:long_name = "variable names from ASCII input" ;

by hsoh