Details of mixing events at the top of marine stratocumulus observed during ACORES2017

Intensive mixing in the inversion layer capping marine boundary layer over northeastern Atlantic has beeninvestigated with high resolution (down to 1 cm) using UltraFast Thermometer 2.0 (UFT-2) for measuringtemperature, particle volume monitor (PVM-100A) for liquid water content, and open-path infrared hygrometer(LI-7500) for humidity. Instruments operated in close spatial collocation (30 cm) onboard the Airborne CloudTurbulence Observation System (ACTOS), carried by a helicopter, which provides relatively slow horizontalairspeed (20 m/s) and fast climb rate (up to 5 m/s) resulting in steep profiles. Measurements were performed in thecourse of the field project Azores stratoCumulus measurements Of Radiation, turbulEnce and aeroSols (ACORES) in summer 2017. Turbulent mixing at the interface between boundary layer (BL) and free troposphere (FT) manifests inabrupt changes in temperature, humidity and liquid water content sampled along the flight path. Details of mixingare presented and discussed for the selected events, including both stratocumulus-capped and clear-air BLs. Theinterface layer often contains vigorous filaments of cloud or clear or cloud–free air with different thermodynamicproperties, at different stages of stirring and homogenization. Borders between those filaments might be verysharp, depending on the gradient of temperature, humidity and wind velocity between BL and FT.