Vertical Variation of Cloud Microphysical Relationships in Stratocumulus Clouds Observed during the Acores Campaign

This study leverages cutting-edge in-situ and remote sensing technologies to comprehensively analyze stratocumulus cloud microphysics, particularly focusing on cloud-top entrainment instability (CTEI) and radiative cooling (RC) effects. Utilizing the Airborne Cloud-Turbulence Observation System (ACTOS) and the Spectral Modular Airborne Radiation Measurement sysTem–Helicopter-Borne Observations (SMART-HELIOS), both deployed on helicopters during the Azores Stratocumulus Measurements of Radiation, Turbulence, and Aerosols (ACORES) campaign, we explored the vertical dynamics of entrainment-mixing affected and diluted (i.e., mixed) cloud parcels. ACTOS, equipped with advanced in-situ instruments, captured high-resolution data on microphysical properties. At the same time, SMART-HELIOS provided simultaneous remote sensing observations from above the cloud layer, offering unique insights into cloud spatial structures.

We found inferential evidence of vertical movements of mixed parcels in conditions where CTEI criterion was satisfied. In contrast, when CTEI criterion was not satisfied, we noticed distinct differences in the vertical variations of cloud microphysical properties Additionally, SMART-HELIOS radiation remote sensing data revealed that optically thinner clouds were more prevalent when CTEI criterion was satisfied, while denser clouds were associated with prohibited CTEI conditions. In addition, the work of La and Yum (QJRMS, 2024; in revision) highlighted that, in flights where CTEI was not clearly observed, as in the POST campaign, the effect of RC differences between mixed and unmixed (i.e., undiluted) parcels, which tended to be closely affected by wind shear near cloud top, seemed to become more important in the determination of vertical movement. By integrating the results from the two campaigns, this study proposes a more intricate picture where both CTEI and RC are influential in the vertical movement of mixed parcels. More details will be discussed at the meeting.