Meteorology#

Updated: 2023-11-03

Contrail models used throughout the Contrails API require a number of meteorological inputs. On /trajectory endpoints, the given flight trajectory is interpolated against gridded weather data to determine the ambient conditions at each point along the trajectory. On /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 /trajectory POST endpoints and /grid/issr, /grid/sac, and /grid/pcr GET endpoints in 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 5 days before the current time. It is used on all /trajectory POST endpoints and /grid/issr, /grid/sac, and /grid/pcr GET endpoint whenever it is available.

Currently, the ERA5 reanalysis data used in the API includes vertical pressure levels between 500 hPa and 70 hPa. The data has a horizontal resolution of 0.25 degrees and a temporal resolution of 1 hour. The vertical resolution is only about 4000 feet throughout typical cruising altitudes. We intend to use model level ERA5 products in the future to improve the vertical resolution.

Precomputed Gridded CoCiP Data#

Unlike the /grid/issr, /grid/sac, and /grid/pcr endpoints, the /grid/cocip endpoint serves precomputed gridded CoCiP data. The weather data used to compute the CoCiP model uses pressure level ERA5 and HRES data, depending on the time of the CoCiP forecast. In the future, we will use model level data here as well.