A large high occupied the Beaufort Sea. SHEBA ship was on its western side in a southerly flow. A dense cloud mass covered the ship. Radar indicated a cloud base of 4.5-5.0 km with some variations. Surface fog obscured the lidar from seeing the cloud base. The radar showed two thick layers. From 4.5 to 6.5 km strong radar returns were measured. Then no returns were found in a narrow layer from 6.5-7.0 km. Light returns were measured from 7.0 to 10.5 km. The sounding showed a very thin but nearly saturated layer at 3 km with unsaturated conditions above and below this layer. The surface was definitely saturated with a fog and 1/2 mile visibility. Sounding humidities were high - around 80% - in the 4.6 to 6.5 km. Saturation with respect to ice could have occurred since the temperature was < -8 C. The sounding reported a very thin but very dry layer around 7 km which had an inversion. This corresponds to the layer without radar returns. Above 7 km, the sounding humidity with respect to water was only about 65%. The radar indicated the cloud above 7 km was thining after 22:00 UT. The Aircraft Scientist Report doesn't discuss any cloud above flight level (around 6.3 km). Some thin cirrus could have been present. Cirrus above flight level were found south of SHEBA ship on the ferry legs.
The trajectories to SHEBA ship show the affects of the high pressure system in the Beaufort Sea to the east. The low level air, surface to 1.5 km, came from the eastern side of the Beaufort Sea, circling around the high pressure system. Higher altitude air came from the Canadian islands circling around the Beaufort Sea and crossing Alaska's north slope. At 9 km, the air came from a different location. The trajectory indicates the 9 km air came from the pole circling around the western Arctic Ocean along the Siberian coast.
