Documentation: Make WRF-DART tutorial Step 3 'prepare (prepbufr) observations' section informational only

[braczka]

What's the issue?

The documentation to perform NCEP prepbufr observation conversion within the WRF-DART tutorial should be migrated to the prepbufr page. The STEP 3 Prepare Observations section in WRF-DART tutorial should be stripped down to only the acquisition of prepqm data files (ds090 or ds337) needed to replicate the tutorial. Users should use the default WRF-DART obs_seq file provided in the tutorial download and should refer to the the prepbufr converter documentation for instructions on how to customize prepbufr obs conversion for non-tutorial applications.

Where did you find the issue?

Step 3: Prepare Observations [OPTIONAL]

What needs to be fixed?

This section is redundant to the prepbufr obs converter documentation -- which also needs updating. Prepbufr converter documentation to be performed in separate issue. Both @mgharamti and @kdraeder have experience with converting prepbufr atmospheric files.

Anything else we should know?

Please see issue #634 led by @mjs2369 for more information on additional prepbufr converter steps.

[braczka]

Related to this issue -- I tried to diagnose whether a user can reproduce the obs_seq file provided as a default in the WRF-DART tutorial if they follow the Step 3 optional instructions where the obs_seq is generated manually. Yi Dai has reported he could not reproduce the the default obs_seq file (at least 10 observation types missing). This is likely an archived data issue (i.e. choice of rsd090 versus rsd377) and unlikely to be a software issue. See the table pasted below where I compare the resulting obs_seq file based on choice of prepqm raw file. Summary of major conclusions are:

1. I can reproduce the observation types reported by Yi Dai if using the ds090 prepqm files as the input to the prepbuf converter.
2. It does not appear that a user can reproduce all of the observation types included in the WRF-DART tutorial default obs_seq file simply by following the Step 3 instructions. Regardless of whether using the ds090 or ds377 prepqm files as input, or altering the otype option in the &prep_bufr_nml to include all the observation types possible during the conversion process -- some observation types (e.g. METAR_*, which are MADIS data files) do not belong to these NCEP prepqm data files. Therefore it appears the default obs_seq used in the WRF-DART tutorial is a combination of several different data sources combined together. The tutorial instructions should not give the impression that all the observation types come from the NCEP prepqm files alone.
3. These findings support the original motivation of this issue -- which is to remove the Step 3 optional instructions from the WRF-DART tutorial documentation, and simply state that the combination of observation types was constructed from several data sources (e.g. NCEP prepqm, MADIS, etc) and refer the user to the available obs_converter resources (e.g. NCEP/prepbufr and MADIS).

[braczka]

It seems like the Step 3: Prepare Observations from WRF-DART tutorial section could be migrated to the prepbufr and/or create_real_obs documentation, as a 'Quickstart example for Derecho' example. This can complement the existing prepbufr and create_real_obs docs that go into way more detail and targeted for users he need to perform the conversion on their own systems. I will generate a new quickstart section, and remove redundancies elsewhere where possible.

[hkershaw-brown]

fixed in #823