Abstract. The formation of sulfate and secondary organic aerosol mass in the aqueous phase (aqSOA) of cloud and fog droplets can significantly contribute to ambient aerosol mass. While tracer compounds give evidence that aqueous phase processing occurred, they do not reveal the extent to which particle properties have been modified in terms of mass, chemical composition, hygroscopicity and oxidation state. We analyse data from several field experiments and model studies for six air mass types (urban, biogenic, marine, wild fire biomass burning, agricultural biomass burning and background air). We focus on the trends of changes in mass, hygroscopicity parameter κ, and oxygen-to-carbon (O / C) ratio due to cloud processing. We find that the modification of these parameters upon cloud-processing is most evident in urban, marine and biogenic air masses, i.e. air masses that are more polluted than very clean air (background air) but cleaner than heavily polluted plumes as encountered during biomass burning. Based on these trends, we suggest that the mass ratio (Rtot) of the potential aerosol sulfate and aqSOA mass to the initial aerosol mass can be used to predict whether cloud processing will be detectable. Scenarios where this ratio exceeds Rtot ~ 2 are the most likely ones where clouds can significantly change aerosol parameters. Comparison to Rtot values as calculated for ambient data at different locations confirm the applicability of the concept to predict a cloud-processing signature in selected air masses.;
