Science Flight #7 - May 10

On Saturday after suffering from the continuously bad weather, we finally encountered our preferable measurement conditions, a wide field of persistent boundary layer clouds. Unfortunately, these clouds were also quite stable above the airport. With the aviation weather indicating icing conditions above YEV, we were not permitted to start until the cloud base stepped up and we could start and approach the measurement area flying below the clouds. The low clouds were investigated North East of the Mackenzie Delta. Two cloud legs in north-south direction, one at 133° W and one at 129° W were defined. In between Polar 6 was intended to measure aerosol and trace gases while Polar 5 continued with remote sensing of the clouds and the atmosphere.

The flight went pretty well. We found that the two cloud legs differ significantly. While on the western one the clouds were thin easily to be penetrated by Polar 6 and ended before the northernmost point, the clouds in the east were quite thick and caused a lot of icing on Polar 6 again, when flying in the cloud top layer. In this area also an enhanced aerosol concentration above the clouds was indicated by AMALi. Some thin haze layers at about 10,000 ft altitude were also observed from the remote sensing on Polar 5. In coordination Polar 6 tried to sample these clouds in situ as Polar 6 was just about to finish an extended profiling of the cloud free atmosphere. On the second cloud leg, the situation remained stable with no significant changes. Similar to the first cloud leg a drop sonde was released indicating cloud top temperature of about -10°C. Due to some instrument problems, Polar 5 had to repeat the sampling of this cloud leg and separated from Polar 6. On the direct way home to Inuvik another significant change of the aerosol concentration above the clouds was detected by the lidar. This change was visible throughout the column up to 11,000 ft.

For details read here: http://www.uni-leipzig.de/~racepac/flights/flight_07.html