The Arctic Cold Air Outbreak (ACAO) airborne field campaign was undertaken by the Met Office using the FAAM BAe-146 aircraft in March 2022 operating out of Kiruna, Sweden.

In addition to the Met Office, scientists from the Universities of Manchester and Leeds participated in the campaign to make novel in-situ airborne measurements of the evolution of cold-air outbreaks (CAOs), in terms of the meteorology, atmospheric composition and clouds, from the Marginal Ice Zone (MIZ) to Scandinavia.

Representing the processes important for the formation and evolution of these mixed-phase clouds in models is extremely challenging, yet acutely important for the radiation budget of mid- and high-latitude clouds. Close co-ordination between ACAO flights and four other research aircraft that are scheduled to operate in the region at the same time, with complimentary scientific objectives, facilitated a unique opportunity to collect a more comprehensive dataset. This will be used to evaluate and develop improvements to the representation of mixed-phase clouds in the Unified Model that is used by the Met Office for operational Numerical Weather Prediction and climate simulations.