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Abstract:
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 free atmosphere and cloud top, and we found that the thickness of EIL affected the vertical variation of cloud microphysics and thermodynamics. In some flights, the observed homogeneous mixing traits became stronger as the depth from the cloud top increased, suggesting that vertical circulation mixing might have occurred in these clouds. In one flight, however, homogeneous mixing traits became stronger only up to the mid-level of the cloud. Uniquely to this case, the correlation between virtual potential temperature (θv) and liquid water content (LWC), Γ(θv-LWC), was strongly negative at the cloud top, which implied that it would be hard for the diluted mixed parcel to descend down. We found that Γ(θv-LWC) depended on the EIL thickness, suggesting that EIL thickness could affect vertical circulation of mixed parcels. Moreover, we found that the homogeneous mixing traits near cloud top was stronger when EIL thickness was larger. This might be probably because the turbulent dissipation rate in the EIL increased as the EIL thickness increased, and therefore the possibility of homogeneous mixing increased. These findings have significant implications for understanding how EIL affects entrainment and vertical circulation mixing in stratocumulus clouds. More details will be discussed at the meeting.
