Science Flight #10 - May 14

Today again both aircraft should fly. After temperatures dropped after the incoming cold front from 20°C to negative values again, low level clouds remained above the Beaufort Sea. In Inuvik the sky cleared up during the morning and conditions were ideal for sampling the wide boundary layer cloud field in the north east. This cloud field we finally also found. Cloud as far as the horizon with just some inhomogeneities at cloud top and clear sky above. Similar to some of our computer models. 

 The general conditions were characterized by strong northerly winds. In cloud altitude about 40 kn were indicated by the aircraft. Above land additional turbulence made flying a bit bumpy. For today's mission the flight path of both aircraft was chosen to be like a horizontal raster. Five East-West 20 NM legs only separated by 10 NM build one Box in which we intend do investigate the small scale horizontal variability of the clouds. While Polar 5 does the remote sensing, Polar 6 tried to sample the clouds top along this track as best as possible. A second box was placed just 20 NM eastwards to the first box trying to follow the general flow of the cloud field.

For our means this was a really complicated flight pattern which did a lot of additional work for the co-pilots. These guys always have to enter the waypoints into the navigation system of the aircraft. 15 points took a while. Therefore, flying was not as boring as during a simple straight leg. The second additional work came for Polar 6 where the pilots had to take care for icing of the winds. The low clouds encountered to contain a large fraction of super-cooled liquid water which immediately freezes, when hitting any part of the aircraft. Also the wind shield in the cockpit loose lot of the free view. After trying to enter the cloud, this icing was finally to dangerous for operating long inside the cloud. That's why Polar 6 decided to stay only in the entrainment zone of the cloud tops. This had a funny effect. When climbing, the crew could see the path of Polar 6 in the clouds. A trench was dug into the cloud top. 

For details read here: http://www.uni-leipzig.de/~racepac/flights/flight_10.html