RTD updates: Add clarifying text to ObsPack, Planeflight diag pages

docs/source/gcclassic-user-guide/obspack.rst
- Add "attention" block advising users to pre-process ObsPack
  GLOBALVIEWplus CH4 files before reading into GEOS-Chem
- Added updated link to NOAA ObsPack data site

docs/source/gcclassic-user-guide/planeflight.rst
- Add clarifying text (as a footnote) specifying the types of
  data that can be input with altitude coordinates

CHANGELOG.md
- Updated accordingly

Signed-off-by: Bob Yantosca <yantosca@seas.harvard.edu>

CHANGELOG.md

@@ -9,6 +9,11 @@ The format is based on [Keep a
 Changelog](https://keepachangelog.com/en/1.0.0/), and this project
 adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased] - TBD
+### Added
+- Added clarifying text about which types of data can use altitude coordinates for the Planeflight diagnostic in RTD documentation 
+- Added warning for users to preprocess ObsPack GLOBALVIEWplus CH4 data files before reading into GEOS-Chem in RTD documentation
+
 ## [14.5.1] - 2025-01-10
 ### Added
 - Added code to `src/CMakeLists.txt` to build & install the KPP standalone executable when `fullchem` or `custom` mechanisms are selected

docs/source/gcclassic-user-guide/obspack.rst

@@ -11,6 +11,30 @@ measurements). This feature was written by Andy Jacobson of NOAA and
 Andrew Schuh of Colorado State University and implemented in GEOS-Chem
 12.2.0.
 
+.. attention::
+
+   The GEOS-Chem ObsPack diagnostic was originally developed for use
+   with the `ObsPack GLOBALVIEWplus CO2 product
+   <https://commons.datacite.org/doi.org/10.25925/20241101>`_.  The
+   data files in this product contain a particular netCDF variable
+   named :literal:`CT_sampling_strategy` that GEOS-Chem uses to
+   quickly determine the time-averaging window for aggregating
+   observations.
+
+   We have recently learned that the `ObsPack GLOBALVIEWplus CH4 data
+   product <https://commons.datacite.org/doi.org/10.25925/20241001>`_
+   currently lacks the :literal:`CT_sampling_strategy` variable, and
+   thus is incompatible with GEOS-Chem.
+
+   The best workaround for now is to preprocess ObsPack GLOBALVIEWplus
+   CH4 data files with one of the following Python tools before
+   attempting to read them into GEOS-Chem:
+
+   - `process_obspack </~https://github.com/eastjames/process_obspack>`_
+     by James East
+   - `gcpy_campaigns </~https://github.com/jhaskinsPhD/gcpy_campaigns>`_
+     by Jessica Haskins
+
 .. _specifying_obspack_diagnostic_options:
 
 =====================================
@@ -47,9 +71,9 @@ YYYY/MM/DD date on which you would like to obtain ObsPack diagnostic
 output from GEOS-Chem. (The ObsPack diagnostic will skip over days on
 which it cannot find an input file.)
 
-ObsPack input files can be downloaded from NOAA (see
-`https://www.esrl.noaa.gov/gmd/ccgg/obspack/
-<https://www.esrl.noaa.gov/gmd/ccgg/obspack/>`_).
+ObsPack input files can be downloaded the NOAA website:
+`https://gml.noaa.gov/ccgg/obspack/
+<https://gml.noaa.gov/ccgg/obspack/>`_.
 
 .. attention::
 

docs/source/gcclassic-user-guide/planeflight.rst

@@ -10,7 +10,7 @@ along flight tracks or at the position of ground observations.  This
 can be more efficient in terms of storage than saving out 3-D data
 files via the :ref:`GEOS-Chem History diagnostics <history-diagnostics>`.
 
-.. attention::
+.. important::
 
    Several diagnostic quantities were disabled when the SMVGEAR
    chemistry solver was replaced with the FlexChem implementation of
@@ -214,34 +214,42 @@ you will specify the points that make up the flight track.
 .. table::
    :align: center
 
-   +---------------+-----------------------------------------------+
-   | Quantity      | Description                                   |
-   +===============+===============================================+
-   | ``POINT``     | A sequential index of flight track points.    |
-   +---------------+-----------------------------------------------+
-   | ``TYPE``      | Identifier for the plane (or station)         |
-   +---------------+-----------------------------------------------+
-   | ``DD``        | Day of the observation                        |
-   +---------------+-----------------------------------------------+
-   | ``MM``        | Month of the observation                      |
-   +---------------+-----------------------------------------------+
-   | ``YYYY``      | Year of the observation                       |
-   +---------------+-----------------------------------------------+
-   | ``HH``        | Hour of the observation (UTC)                 |
-   +---------------+-----------------------------------------------+
-   | ``MM``        | Minute of the observation (UTC)               |
-   +---------------+-----------------------------------------------+
-   | ``LAT``       | Latitude (deg), range -90 to +90              |
-   +---------------+-----------------------------------------------+
-   | ``LON``       | Longitude (deg), range -180 to +180           |
-   +---------------+-----------------------------------------------+
-   | ``ALT/PRE``   | Altitude [m] or Pressure [hPa] of             |
-   |               | the observation                               |
-   +---------------+-----------------------------------------------+
-   | ``OBS``       | Value of the observation (if known),          |
-   |               | used to compare to model output               |
-   +---------------+-----------------------------------------------+
-
+   +--------------+-----------------------------------------------+
+   | Quantity     | Description                                   |
+   +==============+===============================================+
+   | ``POINT``    | A sequential index of flight track points.    |
+   +--------------+-----------------------------------------------+
+   | ``TYPE``     | Identifier for the plane (or station)         |
+   +--------------+-----------------------------------------------+
+   | ``DD``       | Day of the observation                        |
+   +--------------+-----------------------------------------------+
+   | ``MM``       | Month of the observation                      |
+   +--------------+-----------------------------------------------+
+   | ``YYYY``     | Year of the observation                       |
+   +--------------+-----------------------------------------------+
+   | ``HH``       | Hour of the observation (UTC)                 |
+   +--------------+-----------------------------------------------+
+   | ``MM``       | Minute of the observation (UTC)               |
+   +--------------+-----------------------------------------------+
+   | ``LAT``      | Latitude (deg), range -90 to +90              |
+   +--------------+-----------------------------------------------+
+   | ``LON``      | Longitude (deg), range -180 to +180           |
+   +--------------+-----------------------------------------------+
+   | ``ALT/PRE``  | Altitude [m] or Pressure [hPa] of             |
+   |              | the observation [#A]_                         |
+   +--------------+-----------------------------------------------+
+   | ``OBS``      | Value of the observation (if known),          |
+   |              | used to compare to model output               |
+   +--------------+-----------------------------------------------+
+
+.. rubric::
+
+.. [#] Altitude is only supported for CCGG or tower data.  All other
+       observations must specify pressure in hPa.  This can be
+       obtained from the "static pressure" field as measured by the
+       aircraft.  See this `code block in planeflight_mod.F90
+       </~https://github.com/geoschem/geos-chem/blob/b0e03cc0f7c06b899824a69744b67e9632675cbd/GeosCore/planeflight_mod.F90#L1061-L1114>`_
+       for details.
 
 .. important::