ACCACIA was part of the NERC Arctic research programme. (NERC Reference: NE/I028858/1).

This dataset collection contains atmospheric measurements from Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft, the British Antarctic Survey (BAS) Masin aircraft and from RRS James Clark Ross ship. This dataset collection also contains data from specially configured Met Office Unified Model runs. Data from corresponding ship measurements are also available.

The climate of the Arctic is changing faster than that almost anywhere else on Earth, warming at a rate of twice the global average. This warming is accompanied by a rapid melting of the sea ice and a thinning of the ice that remains from year to year. The strong warming in the Arctic is due to several positive feedback processes, including a sea-ice albedo feedback (warmer conditions melt ice, lowering the average reflectivity of the mixed ice/ocean surface and thus absorbing more solar radiation, leading to increased ice melt and further lowering of the albedo) and several cloud feedbacks. There is a large uncertainty in models of the Arctic climate primarily because of the poor representation of physical processes within the models - particularly the representation of Arctic clouds, and due to some unique and particularly challenging conditions.

A better understanding of cloud and aerosol processes in the Arctic is critical to understanding the polar atmosphere and developing more realistic climate models.

To address this issue the ACCACIA project embarked on an intensive measurement campaign in the Svalbard archipelago near the margin of permanent Arctic sea ice cover resulting in a comprehensive dataset comprising of airborne in situ measurements of cloud microphysical properties, the vertical structure of the boundary layer and aerosol properties, and the fluxes of solar and infra red radiation above, below, and within cloud.