A Case Study of Stratus Cloud Properties Using In Situ Aircraft Observations over Huanghua, China

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 m and CCN have been found within the planetary boundary layer (PBL) below similar to 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 r(e) is quite small (3.0-6 m) at heights below 1150 m, large (7-13 m) 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.