Atmospheric composition forecasts move to higher resolution

Richard Engelen


On 21 June, a new version of the global forecasting system run by the Copernicus Atmosphere Monitoring Service (CAMS) was made operational. This upgrade increases the spatial resolution of the forecast model from 80 km to 40 km. The improved system also produces two 5-day atmospheric composition forecasts per day instead of one. In addition to the forecast initialised at 00 UTC, there is now also a forecast initialised at 12 UTC, which is available before 22 UTC. The two changes mean that forecasts now provide more geographical details and are delivered to CAMS users in a timelier manner.

CAMS, which is operated by ECMWF as part of the EU’s Copernicus Earth observation programme, is subject to quality control and validation. The improved forecasting system ran in test mode for several months before it was made operational. The CAMS validation team, which comprises many European actors and is led by the Dutch national weather forecasting service KNMI, carefully assessed the output to ensure the quality of the daily analyses and forecasts. Their report, which is available on the CAMS website (, was published at the end of April and formed the basis for the decision to go ahead with the implementation of this improved production system.

While the impact of the resolution increase on forecast quality is mostly neutral, in some cases significant improvements are seen close to the surface. This is due to better-resolved orography as well as a better use of the high-resolution emission datasets that form an input into the CAMS analyses and forecasts.

CAMS forecasts are available directly from the ECMWF MARS archive, through the CAMS web data server, or through operationally supported FTP access as described on the CAMS website. For any questions, please contact our User Support team at

Forecasts at different resolutions
Forecasts at different resolutions. The charts show 21-hour forecasts of dust aerosol optical depth at 550 nm for 21 UTC on 5 April 2016 at the previous resolution (left) and at the new resolution (right).