Text/us-499 Documentation to address Sigma Level Output

[jdkublnick]

This PR shows a user how to enable different types of output and addresses issue #1093

Docs build locally here: https://uppjdk.readthedocs.io/en/latest/CustomizingTheUPP/EnablingOutput.html

[jdkublnick]

@gspetro-NOAA

[gspetro-NOAA]

It's best to replace the numbers with #. because then it autofills the numbers, and you don't have to worry about renumbering if steps are added or removed over time.

[gspetro-NOAA]

Suggested change

	.. _enabling-Output:
	.. _enabling-output:

[gspetro-NOAA]

Suggested change

	UPP can output temperature, U, and V components on sigma surfaces. These correspond to indices 206, 208, and 209 in the :term:`GRIB2`` table. Follow these steps to configure your workflow for this output:
	UPP can output temperature, U, and V components on sigma surfaces. These correspond to indices 206, 208, and 209 in the :term:`GRIB2` table. Follow these steps to configure your workflow for this output:

[gspetro-NOAA]

Could you actually link to the table? That's more important in terms of knowing what variables are possible in UPP.

[gspetro-NOAA]

Suggested change

	1. **Locate XML Configuration Files**:
	- Use the XML files in the `UPP/parm` directory as references. Specifically, the `post_avblflds.xml` file contains all the fields that UPP can output.
	2. **Modify Control XML**:
	- Copy the entries for temperature, U, and V (indices 206, 208, and 209) from `post_avblflds.xml` to the control XML file used in your workflow.
	3. **Validation**:
	- Validate the control XML file against the `EMC_POST_CTRL_Schema.xsd` schema.
	4. **Flat Text File Generation**:
	- Convert the control XML to a flat text file, ensuring that it is validated as part of the process. More information can be found in the :ref:`create_txt_file` documentation.
	An XML :ref:`control file <control-file>` determines what fields and levels UPP will output.
	#. **Locate the XML Control File**: Control files for various operational models are located in the ``UPP/parm`` directory. The ``post_avblflds.xml`` file contains all fields that the UPP can output.
	#. **Modify the Control XML**: Copy the entries for temperature, U, and V (indices 206, 208, and 209) from ``post_avblflds.xml`` to the control XML file used in your workflow. Be sure to include a ``<level></level>`` tag with the appropriate levels in the XML control file to define which sigma levels to output.
	#. **Validate the Control File**: Validate the control XML file against the `EMC_POST_CTRL_Schema.xsd` schema according to :ref:`these instructions <create_txt_file>`.
	#. **Flat Text File Generation**: Convert the control XML to a flat text file based on the information in the :ref:`create_txt_file` documentation.

[gspetro-NOAA]

Suggested change

	By default, only certain sigma levels are outputted. These levels are in the source file `SET_LVLSXML.f` and can be found between lines 342 and 363. Users must:
	By default, only certain sigma levels are outputted. These levels are defined in `SET_LVLSXML.f <https://github.com/NOAA-EMC/UPP/blob/develop/sorc/ncep_post.fd/SET_LVLSXML.f>`_ using the ``ASIGO1`` array. Users must review these levels in the ``SET_LVLSXML.f`` file to confirm compatibility with their requirements.

Best not to indicate specific lines of code because they can change.

[gspetro-NOAA]

Suggested change

	- **Verify Default Levels**:
	Review these levels in the `SET_LVLSXML.f` source file to confirm their compatibility with your requirements.
	- **Add <level></level> Tags**:
	Include a `<level></level>` tag in the XML configuration to explicitly define the sigma levels to be output.

The level tags pertain to the control file, not the SET_LVLSXML.f, so I moved that info up and combined the remaining bullet point into the sentence above.

[gspetro-NOAA]

Suggested change

	If the default sigma levels are insufficient, you must:
	1. **Modify `SET_LVLSXML.f`**:
	- Change the entries for `ASIGO1` to include your desired sigma levels.
	2. **Recompile UPP**:
	- Recompile the UPP source code after making the changes.
	3. **Update XML Tags**:
	- Ensure that the XML tags explicitly reference the modified sigma levels.
	If the default sigma levels are insufficient, users must:
	#. **Modify `SET_LVLSXML.f`**: Change the entries for ``ASIGO1`` to include your desired sigma levels.
	#. **Recompile UPP**: Recompile the UPP source code after making the changes.
	#. **Update XML Tags**: Ensure that the XML control file explicitly references the modified sigma levels in the <level></level> tag.

[gspetro-NOAA]

Suggested change

	Important Notes
	---------------
	- Adding `<level></level>` tags manually allows UPP to compile and run successfully, but it will not produce any output unless the levels are also modified in `SET_LVLSXML.f` and properly referenced.
	- Fortran I/O errors may occur if the sigma levels in the control file are not synchronized with the source code configuration.
	- Comprehensive documentation on control files can be found in the :ref:`control-file` documentation, which provides details about XML file formatting and flat file generation.
	By following these steps, users can successfully configure UPP to generate model output on user-defined sigma levels while avoiding common pitfalls.
	.. hint::
	- Adding `<level></level>` tags manually allows UPP to compile and run successfully, but it will not produce any output unless the levels are also modified in ``SET_LVLSXML.f`` and properly referenced.
	- Fortran I/O errors may occur if the sigma levels in the control file are not synchronized with the source code configuration.
	- Comprehensive documentation on control files can be found in the :ref:`control-file` documentation, which provides details about XML file formatting and flat file generation.