A case study of stratus cloud properties using in situ aircraft observations over Huanghua, China

Abstract

Cloud liquid water content (LWC) and droplet effective radius (r e ) have an important influence on cloud physical processes and optical characteristics. The microphysical properties of a three-layer pure liquid stratus were measured by aircraft probes on 26 April 2014 over a coastal region in Huanghua, China. Vertical variations in aerosol concentration (Na), cloud condensation nuclei (CCN) at supersaturation (SS) 0.3%, cloud LWC and cloud r e are examined. Large Na in the size range of 0.1-3 μm and CCN have been found within the planetary boundary layer (PBL) below 1150 m. However, Na and CCN decrease quickly with height and reach a level similar to that over marine locations. Corresponding to the vertical distributions of aerosols and CCN, the cloud re is quite small (3.0-6 μm) at heights below 1150 m, large (7-13 μm) at high altitudes. In the PBL cloud layer, cloud r e and aerosol Na show a negative relationship, while they show a clear positive relationship in the upper layer above PBL with much less aerosol Na. It also shows that the relationship between cloud r e and aerosol Na changes from negative to positive when LWC increases. These results imply that the response of cloud r e to aerosol Na depends on the combination effects of water-competency and collision-coalescence efficiency among droplets. The vertical structure of aerosol Na and cloud r e implies potential cautions for the study of aerosol-cloud interaction using aerosol optical depth for cloud layers above the PBL altitude.