Meteorology

Updated: 3 January 2025

Contrail models used throughout the Contrails API require a number of meteorological inputs. On v0/trajectory endpoints, the given flight trajectory is interpolated against gridded weather data to determine the ambient conditions at each point along the trajectory. On v0/grid endpoints, meteorological data is used to determine conditions at each grid point.

HRES Forecast Data

The Contrails API uses ECMWF HRES forecast data for contrail models requiring forecast and real-time and weather data. This includes all v0/trajectory POST endpoints and v0/grid/issr, v0/grid/sac, and v0/grid/pcr GET endpoints for which ERA5 reanalysis data is not yet available. Generally, the HRES forecast data used in the backend allow contrail forecasts to be served up to 58 - 65 hours into the future.

The HRES forecast data used in the API backend is derived from ECMWF’s L137 model level simulations, thereby providing a more accurate representation of the atmosphere than the ECMWF pressure level data. In particular, the Contrails API uses model levels 66 through 93, resulting in a vertical resolution of about 1000 feet throughout typical cruising altitudes. The HRES data used has a horizontal resolution of 0.1 degrees and a temporal resolution of 1 hour.

ERA5 Reanalysis Data

The API uses ECMWF ERA5 reanalysis data for contrail models requiring historical weather data. ERA5 data is typically available about 7 days before the present time. It is used on all v0/trajectory POST endpoints and v0/grid/issr, v0/grid/sac, and v0/grid/pcr GET endpoint whenever it is available.

The ERA5 reanalysis data used in the API shares the same vertical resolution as the aforementioned model-level HRES forecast data. ERA5 reanalysis data has a horizontal resolution of 0.25 degrees and a temporal resolution of 1 hour. Currently, the API is backed by historical ERA5 data dating back to 1 January 2019.

Precomputed Gridded CoCiP Forecasts

Unlike the v0/grid/issr, v0/grid/sac, and v0/grid/pcr endpoints, the v1/grids endpoint serves precomputed gridded CoCiP data. The weather data used to compute the CoCiP model generally uses model level HRES data. However, some historic data served through this endpoint may have been computed from ERA5 data.