Abstract
Cloud liquid water content (LWC) and droplet effective radius (re) 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 re 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 re 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 re and aerosol Na changes from negative to positive when LWC increases. These results imply that the response of cloud re 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 re implies potential cautions for the study of aerosol-cloud interaction using aerosol optical depth for cloud layers above the PBL altitude.
Highlights
Stratus clouds, with about 24% global area coverage [1], have been the focus of many studies due to their significant influence on surface radiation budget [2,3,4,5,6]
Several studies [19,20,21,22] have examined stratus cloud properties over Chinese land areas such as Beijing, Yan’an and Hebei, based on very limited aircraft observations, which have mainly shown the characteristics of cloud droplet size distribution and liquid water content over these areas
While it was indicated that the FSSP measurements of droplet size are accurate to 17% and liquid water content (LWC) is accurate to within 34% [24], additional errors could exist in cloud droplet number concentrations (Nc), re and LWC, due to the shatter artifact
Summary
With about 24% global area coverage [1], have been the focus of many studies due to their significant influence on surface radiation budget [2,3,4,5,6]. The stratus cloud re mainly lies between 5 μm and 15 μm over the marine region, 3 μm and 12 μm over the US continental regions, and 5 μm and 20 μm in the Arctic [8] This spatial distribution is likely associated with the variation in available water amount and aerosol pollution [8]. Several studies [19,20,21,22] have examined stratus cloud properties over Chinese land areas such as Beijing, Yan’an and Hebei, based on very limited aircraft observations, which have mainly shown the characteristics of cloud droplet size distribution and liquid water content over these areas.
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