Relationship Between Vertical Variation of Cloud Microphysical Properties and Thickness of Entrainment Interfacial Layer in POST Stratocumulus Clouds

In this study, we analyzed the vertical variations of cloud microphysics in association with the thickness of the entrainment interfacial layer (EIL) of the stratocumulus clouds observed during the aircraft measurement campaign, the Physics of Stratocumulus Top (POST). Fifteen POST flights were analyzed and EIL was identified in all flights in-between the free atmosphere and the cloud top, and we found that the thickness of EIL was closely related to the vertical variation of cloud microphysics and thermodynamics. In some flights, homogeneous mixing traits of cloud microphysics became stronger as the depth from the cloud top increased, suggesting that vertical circulation of mixed parcels might have occurred in these clouds. In one other flight, however, homogeneous mixing traits became stronger only up to the mid-level of the cloud and then reduced as the depth increased. Uniquely to this flight, the correlation between virtual potential temperature (θ_v) and liquid water content (L), , was strongly negative at the cloud top, which implied that it would be hard for diluted parcels to descend down in this cloud. We found that depended on the EIL thickness, suggesting that EIL thickness could affect vertical circulation of mixed parcels. Moreover, we found that there was a solid negative correlation between the longwave (LW) cooling rate near cloud top and the EIL thickness, and the LW cooling rate was different for mixed and unmixed parcels basically because LWC was different for these parcels. These findings have significant implications for understanding how EIL affects entrainment and vertical circulation of mixed parcels in stratocumulus clouds. More details will be discussed at the meeting.