ENH: Support for Open-Meteo API in the Environment class

CHANGELOG.md

@@ -32,6 +32,7 @@ Attention: The newest changes should be on top -->
 
 ### Added
 
+- ENH: Support for Open Meteo API in the `Environment` class, adding the `open_meteo` and `open_meteo_ensemble` atmospheric models. Pressure-level forecasts, past forecasts (from 2021 onwards) and ensembles are read straight from a keyless JSON API, with no external files and no netCDF/OPeNDAP dependency. [#520](https://github.com/RocketPy-Team/RocketPy/issues/520)
 - ENH: Add simplified opening shock force estimation [#1092](https://github.com/RocketPy-Team/RocketPy/pull/1092)
 - ENH: Add Qodo PR-Agent workflow using Google Gemini [#1089](https://github.com/RocketPy-Team/RocketPy/pull/1089)
 - ENH: Support for Meteomatics API in the `Environment` class [#1079](https://github.com/RocketPy-Team/RocketPy/pull/1079)
@@ -46,6 +47,7 @@ Attention: The newest changes should be on top -->
 
 ### Fixed
 
+- BUG: Report the atmospheric model time period and ensemble member count for lower-case model types. `set_atmospheric_model` documents `type` as case-insensitive, but `Environment.info()` and `all_info()` compared against capitalised literals, so `type="ensemble"` printed no time period and no member count, and skipped the ensemble comparison plot. [#520](https://github.com/RocketPy-Team/RocketPy/issues/520)
 - BUG: Give each `CustomSampler` input its own deterministic stream, and seed samplers sharing one generator once as a group. Existing fixed-seed `CustomSampler` baselines change, and samplers built on the legacy `RandomState` must move to `default_rng` because seeds now carry the full 128 bits. [#1102](https://github.com/RocketPy-Team/RocketPy/pull/1102)
 - BUG: Accept the callable parachute triggers `StochasticParachute` documents, and reject the ones it cannot mean. An invalid string, an empty list or a boolean now fails during validation instead of reaching `Parachute` or becoming a one-metre height trigger. [#1103](https://github.com/RocketPy-Team/RocketPy/pull/1103)
 - BUG: rocket with a late-starting thrust curve never leaves the rail [#1085](https://github.com/RocketPy-Team/RocketPy/pull/1085)

docs/user/environment/1-atm-models/ensemble.rst

@@ -34,6 +34,13 @@ Global Ensemble Forecast System (GEFS)
     provider (or a local copy), you can still load it explicitly by passing the
     dataset path/URL in ``file`` and a compatible mapping in ``dictionary``.
 
+.. tip::
+
+    While the ``GEFS`` shortcut is unavailable, Open-Meteo offers the same GEFS
+    ensemble (plus the ECMWF one) over a plain JSON API, and works with
+    :meth:`rocketpy.Environment.select_ensemble_member` in exactly the same way.
+    See :ref:`open_meteo`.
+
 
 The ``GEFS`` model is a global ensemble forecast system useful for uncertainty
 analysis, but RocketPy's automatic ``file="GEFS"`` shortcut is temporarily

docs/user/environment/1-atm-models/forecast.rst

@@ -16,6 +16,13 @@ Other generic forecasts can also be imported.
     If you want to simulate your rocket launch using past data, you should use \
     :ref:`reanalysis` or :ref:`soundings`.
 
+.. tip::
+
+    The models on this page are fetched over OPeNDAP, which requires the
+    ``netCDF4`` library and can be slow. For a lighter alternative that serves
+    the same kind of pressure-level forecast as plain JSON, see
+    :ref:`open_meteo`.
+
 
 .. _global-forecast-system:
 

docs/user/environment/1-atm-models/index.rst

@@ -12,6 +12,7 @@ environment in the :class:`rocketpy.Environment` class.
 
    Standard Atmosphere <standard_atmosphere.rst>
    Custom Atmosphere <custom_atmosphere.rst>
+   Open-Meteo <open_meteo.rst>
    Forecasts <forecast.rst>
    Soundings <soundings.rst>
    Reanalysis <reanalysis.rst>

docs/user/environment/1-atm-models/open_meteo.rst

@@ -0,0 +1,218 @@
+.. _open_meteo:
+
+Open-Meteo
+==========
+
+`Open-Meteo <https://open-meteo.com/>`_ is a weather API that serves
+pressure-level forecasts, past forecasts and ensemble forecasts as plain JSON
+over HTTPS.
+
+It is often the most convenient weather source in RocketPy, because:
+
+- **No API key** is required for non-commercial use.
+- **No heavy dependencies**: unlike the :ref:`forecast` and :ref:`reanalysis`
+  models, no ``netCDF4``/OPeNDAP download is involved, so requests are quick.
+- **No external files**: recent past launches can be reconstructed straight from
+  the API, without downloading reanalysis files by hand.
+- **Many models in one place**: GFS, ECMWF, ICON, MET Norway, Météo-France, JMA,
+  GEM and UKMO are all reachable through the same interface.
+
+.. note::
+
+    Open-Meteo is free for non-commercial use, with a limit on the number of
+    daily requests. Please read
+    `their terms <https://open-meteo.com/en/terms>`_ before using it, and
+    consider their paid plans for heavier or commercial workloads.
+
+
+Forecasts
+---------
+
+Set the atmospheric model to ``open_meteo``. The launch date must be set,
+because the vertical profile is taken at the hour closest to it.
+
+.. jupyter-execute::
+
+    from datetime import datetime, timedelta
+    from rocketpy import Environment
+
+    tomorrow = datetime.now() + timedelta(days=1)
+
+    env = Environment(
+        date=tomorrow,
+        latitude=39.3897,
+        longitude=-8.28896388889,
+    )
+
+    env.set_atmospheric_model(type="open_meteo")
+
+    env.plots.atmospheric_model()
+
+Note that ``elevation`` was never specified above: Open-Meteo reports the
+elevation of the grid cell it answered for, and RocketPy uses it to set the
+launch site elevation automatically.
+
+
+Selecting a weather model
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+By default RocketPy asks for ``"best_match"``, which lets Open-Meteo pick the
+highest-resolution model available for the requested location. A specific model
+can be requested through the ``file`` argument:
+
+.. jupyter-execute::
+
+    env_ecmwf = Environment(
+        date=tomorrow,
+        latitude=39.3897,
+        longitude=-8.28896388889,
+    )
+    env_ecmwf.set_atmospheric_model(type="open_meteo", file="ecmwf_ifs025")
+    env_ecmwf.plots.atmospheric_model()
+
+Frequently useful models are:
+
+.. list-table::
+    :header-rows: 1
+    :widths: 30 70
+
+    * - Model
+      - Description
+    * - ``best_match``
+      - Open-Meteo picks the best available model for the location (default).
+    * - ``gfs_seamless``
+      - NOAA GFS, global coverage.
+    * - ``ecmwf_ifs025``
+      - ECMWF IFS at 0.25°, global coverage.
+    * - ``icon_seamless``
+      - DWD ICON, global coverage with a higher-resolution European nest.
+    * - ``meteofrance_seamless``
+      - Météo-France ARPEGE/AROME.
+    * - ``gem_seamless``
+      - Environment Canada GEM.
+    * - ``ukmo_seamless``
+      - UK Met Office.
+
+.. seealso::
+
+    The `Open-Meteo documentation <https://open-meteo.com/en/docs>`_ lists every
+    model available, along with its resolution and update frequency.
+
+.. important::
+
+    Not every model resolves every pressure level, and coverage varies with
+    location. RocketPy silently drops the levels a model does not provide, so
+    the resulting profile may reach a lower altitude for some models (for
+    instance, ``ecmwf_ifs025`` tops out at 50 hPa while ``gfs_seamless``
+    reaches 30 hPa). Check ``env.max_expected_height`` if the ceiling matters
+    for your simulation.
+
+
+Past launches
+-------------
+
+When the launch date is in the past, ``open_meteo`` transparently queries
+Open-Meteo's historical-forecast archive instead of the live forecast. No extra
+argument is needed:
+
+.. jupyter-execute::
+
+    env_past = Environment(
+        date=datetime(2024, 1, 10, 12),
+        latitude=39.3897,
+        longitude=-8.28896388889,
+    )
+    env_past.set_atmospheric_model(type="open_meteo")
+    env_past.plots.atmospheric_model()
+
+This is the quickest way to reconstruct the atmosphere of a past flight, since
+it needs neither an external file nor a sounding station nearby. For
+comparison, see :ref:`reanalysis` and :ref:`soundings`.
+
+.. important::
+
+    Open-Meteo's historical data is built from its own archived forecast runs
+    and only covers pressure levels **from around March 2021 onwards**. Earlier
+    dates return no data, and RocketPy warns you when it detects one; use
+    :ref:`reanalysis` or :ref:`soundings` for those instead.
+
+.. note::
+
+    Open-Meteo also offers an ERA5 archive endpoint, but it serves surface
+    variables only and provides no pressure-level data, so RocketPy does not
+    use it: it cannot produce a vertical profile.
+
+
+Ensemble forecasts
+------------------
+
+Open-Meteo also exposes ensemble forecasts, where each member represents a
+slightly different evolution of the atmosphere. They are used exactly like the
+other :ref:`ensemble_atmosphere` models:
+
+.. jupyter-execute::
+
+    env_ensemble = Environment(
+        date=tomorrow,
+        latitude=39.3897,
+        longitude=-8.28896388889,
+    )
+    env_ensemble.set_atmospheric_model(type="open_meteo_ensemble", file="gfs05")
+
+    print(f"Number of members: {env_ensemble.num_ensemble_members}")
+
+    env_ensemble.plots.ensemble_member_comparison()
+
+Individual members are activated with
+:meth:`rocketpy.Environment.select_ensemble_member`:
+
+.. jupyter-execute::
+
+    env_ensemble.select_ensemble_member(10)
+    print(f"Wind speed at 1 km: {env_ensemble.wind_speed(1000):.2f} m/s")
+
+Member ``0`` is the unperturbed control run and is the one selected by default.
+
+Two ensemble models publish the complete set of pressure-level variables that
+RocketPy needs:
+
+.. list-table::
+    :header-rows: 1
+    :widths: 30 20 50
+
+    * - Model
+      - Members
+      - Description
+    * - ``gfs05``
+      - 31
+      - NOAA GEFS at 0.5° (default).
+    * - ``ecmwf_ifs025``
+      - 51
+      - ECMWF ensemble at 0.25°.
+
+The member counts above include the control run, which RocketPy exposes as
+member ``0``.
+
+.. important::
+
+    The remaining Open-Meteo ensemble models cannot be used to build a vertical
+    profile, so RocketPy rejects them with an explanatory error rather than
+    failing later on. ``gfs025``, ``icon_global`` and
+    ``bom_access_global_ensemble`` answer successfully but return no
+    pressure-level values at all, and ``gem_global`` provides temperature and
+    geopotential height but no pressure-level winds.
+
+
+Further considerations
+----------------------
+
+Requests may fail if the API is unreachable or if the daily free-tier limit is
+exceeded. RocketPy retries transient failures automatically and raises a
+``RuntimeError`` with the reason reported by Open-Meteo when the request cannot
+be satisfied.
+
+.. seealso::
+
+    - :ref:`forecast` for OPeNDAP-based forecasts (GFS, NAM, RAP, HRRR).
+    - :ref:`reanalysis` for ERA5 and MERRA-2 reanalysis files.
+    - :ref:`ensemble_atmosphere` for the ensemble workflow in general.

docs/user/environment/1-atm-models/reanalysis.rst

@@ -13,6 +13,13 @@ intervals
 Reanalysis data can be used to set up the environment in RocketPy.
 One common reanalysis dataset is the ERA5.
 
+.. tip::
+
+    Reanalysis datasets must be downloaded as files before RocketPy can read
+    them. If you only need the atmospheric conditions of a past launch from
+    2021 onwards, :ref:`open_meteo` retrieves them straight from an API, with
+    no file to download.
+
 ERA5
 ----