Flight number thirteen: deeper clouds



After an early Sunday morning flight, ACTOS and Smart Helios were prepared for a second flight in the afternoon. Take-Off of the second flight was at 14:15 pm, though in the meantime the Stratocumulus deck which could be observed in the morning broke up and Cumulus clouds developed.
The start went smoothly and the helicopter headed westwards to some remaining Stratocumulus clouds while climbing up to 2100m. As in the first flight a weak inversion was encountered in 450m, some cumulus fractus clouds were located beneath the inversion. In 600m ACTOS flew through a small cumulus cloud with liquid water contents of up to 0.2g/m^3, while the helicopter steadily lifted both measurement platforms. The stratocumulus cloud we tried to catch in the first place had its base in 1100m and reached up to 1400m. A 200m thick inversion with a strength of 3K could be found just above the cloud. Particle concentrations began to peak above the inversion as in the morning flight. Also we saw that some Altostratus clouds were present in 3000 to 3500m.
Having reached finally the 2100m altitude mark, a horizontal leg was flown for the duration 7min. We used this time to spot some good stratocumulus clouds into which we could dip ACTOS in. Over Graciosa cumulus convection was present. To the northeast a cumulus cloud penetrated a Stratocumulus cloud layer which reached towards the island. We decided to fly east and try our luck with that stratocumulus layer.  The top of that cloud layer was almost flat and had no defined contours at all, the shade of the cloud layer seemed rather greyish than white. Four porpoise dives were flown in total in order to measure the vertical structure of the cloud and the inversion. As we dipped ACTOS into the cloud we saw that it had a multilayered structure. The thickness of the clouds was variable, liquid water contents picked up to 0.35g/m^3. With time the clouds became thicker and after an hour a perfect Stratocumulus layer developed and we decidd to fly back.
Water drops started to form on the helicopter’s front shield, indicating that the clouds above developed some drizzle.  
The helicopter headed towards the airport and set ACTOS and Smart Helios safely onto the ground. Thus, an interesting aerosol cloud interaction flight ended.

posted by Kai



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