AEROCLOUD-FIRE will provide a comprehensive data set on the distribution of natural and anthropogenic aerosols in American and European mid-latitudes to advance our understanding on effects of aircraft and wildfire emissions on clouds, dynamics and climate.

Aerosol-cloud interactions are amongst the least understood atmospheric processes in our climate system. Aerosol emissions from aircraft are expected to triple by 2050 and suggest strong increases in climate-warming contrails. Already today, contrails have a significant share to effective radiative forcing from aviation. Yet, the exact magnitude of the climate effects from contrails is highly uncertain and contrail formation at low soot emission levels on volatile aerosol is unexplored. Furthermore, climate change increases the frequency and intensity of wildfires. Aerosol-cloud-radiation interactions can influence atmospheric dynamics, plume transport and evolution, thereby potentially amplifying the impact of wildfires on climate and the environment.

The AEROCLOUD-FIRE campaign combines a novel set of instruments to accurately detect chemical, microphysical and radiative properties of aircraft and wildfire aerosol plumes. HALO will perform a measurement campaign to detect wildfire plumes, aerosol and contrails above North America, the Atlantic and Europe. AEROCLOUD-FIRE will provide data and new insights into

• the microphysical properties of contrails and cirrus to advance our understanding of contrail evolution and climate effect
• the unresolved topic of contrail formation at lowest soot emission levels
• the aerosol and cirrus distributions in the background and in perturbed conditions, as well as aerosol processing in the exhaust plume.

HALO will also execute a series of flights from US/Canada to capture and track North American wildfire events and follow smoke plumes as they transverse over the Atlantic. HALO is ideally equipped to provide critical data and insights into:

• the frequency and mechanisms of transport of wildfire smoke plumes from the boundary layer to the upper troposphere and lower stratosphere (UTLS)
• the microphysical and chemical processes by which the aerosols and gaseous pollutants evolve within the plume and are removed from the atmosphere
• aerosol-radiation-cloud interactions of wildfire-related soot and organic particles.