pb2nc does not handle more than 255 vertical levels

[dwfncar]

pb2nc does not generate NetCDF output (segmentation fault) if the input BUFR file has more than 255 vertical levels. For example, nam.t00z.radwnd.tm02.bufr_d has 500 vertical levels.

The code was designed to interact between C and Fortran with the pre-allocated static buffer. Instead of using dynamic buffer, it will ignore the vertical levels above the pre-defined maximum vertical level and give the warning.

The maximum vertical level will be increased to 1023. [MET-852] created by hsoh

[dwfncar]

The execution time was increased about 4 times longer with the same PREPBUFR file (less than 250 levels)

Here is a simple test with handling different vertical levels with the same input PREPBUFR (the input has less than 255 vertical levels):

• up to 255 levels: real 0m55.369s
  
• up to 511 levels: real 1m38.999s
  
• up to 1023 levels: real 3m5.640s
  

From nightly build log file (NB20170808.out):
Before (rev 4771)
NB20170808.out:TEST: pb2nc_GDAS_mask_grid_G212- pass - 345.791 sec
NB20170808.out:TEST: pb2nc_NDAS_mask_poly_conus - pass - 69.503 sec

After (rev 4784):
NB20170808.out:TEST: pb2nc_GDAS_mask_grid_G212- pass - 1320.358 sec
NB20170808.out:TEST: pb2nc_NDAS_mask_poly_conus - pass - 252.191 sec

by hsoh

[dwfncar]

Added test case (pb2nc_vertical_level_500).

Modify logic of setting the buffer size (discussed with John).
Check contents of obs_bufrvar and ignore the standard 6 variables and the derived variables beginning with "D". If 0 vars are left, use the small buffer. If 1 or more vars are left, use the big buffer.

The 255 vertical levels will be processes for following cases:

• if the request variables are PREPBUFR basic variables (P, Q, T, Z, U, V) and derived variables from them only.
      + If the "level_range.end" from config file is bigger than 255, up to 1013 vertical levels will be processed
  
• all variables are requested but none of them has more than 255 vertical levels.
  

by hsoh