Combining spaceborne observations of CCN, INP, and cloud development for assessing ACI in liquid and ice-containing clouds

Last year, we presented the Cloud-by-Cloud (CxC) approach for studying aerosol-cloud interactions (ACI) through a combination of observations with polar-orbiting and geostationary satellites. Specifically, cloud-relevant aerosol concentrations at cloud level are matched to individual clouds that are observed throughout their life time.

The methodology has now been applied to 11 years of data from MSG-SEVIRI and the CALIPSO lidar over Europe and northern Africa. The resulting data set of several thousand matched aerosol-cloud cases provides a first satellite-based assessment of ACI in warm and cold clouds in which the aerosol component is expressed in actual number concentrations of cloud condensation nuclei (n_CCN) and ice nucleating particles (n_INP) at cloud level. We present findings of the aerosol impact on cloud droplet number concentration, effective radius, liquid water path and cloud phase for different aerosol types and discuss differences to the conventional data-aggregation approach in which aerosols are expressed through aerosol optical depth.