Weather Plugin

The tangram_weather plugin provides API endpoints to serve meteorological data, enabling features like wind field visualization on the map.

Overview

This plugin fetches weather prediction data from Meteo-France's ARPEGE model, processes it, and exposes it via a REST API. The data is provided as GRIB files, which are downloaded and parsed on the backend.

How It Works

1. The plugin downloads GRIB files containing ARPEGE weather model predictions from the public data.gouv.fr repository. These files are cached locally in a temporary directory.

2. It registers a /weather router with the main FastAPI application. The key endpoint is /weather/wind.

3. When a request is made to /weather/wind?isobaric=<level>, the plugin:

   • Determines the latest available GRIB file for the current time.
   • Uses xarray and cfgrib to open the GRIB file.
   • Selects the U and V wind components for the specified isobaric pressure level (e.g., 300 hPa).
   • Returns the data as a JSON response.

4. The frontend WindField.vue component calls this endpoint.