A low was positioned northwest of SHEBA ship and a weak high occupied the Beaufort Sea to the southeast. The main center of the high was in the Canadian Islands. The ship was in a southwesterly wind between the low and high.
Clouds consisted of mainly boundary layer stratus to about 700 meters altitude. An altostratus cloud moved over the ship from the west-southwest at 21:30 UT. It can be seen on the satellite images and the radar. Its height was about 2.7 km according to the radar. After 23:00 UT, this cloud did not appear on the radar. However, other altostratus can be seen on the satellite image southwest, and upwind of the ship which may have crossed the ship.
Cirrus do not appear to have crossed the ship during this flight. The 00 UT sounding shows that a very dry troposphere above 3 km. Another note-worthy feature is an inversion on the 00 UT sounding starting at 800 meters altitude.
The trajectories to SHEBA ship show the low level air, surface to 1.5 km, coming from the Chukchi Sea to the southwest and traveling only a short distance. The six day trajectory for the surface ends in the Chukchi Sea far short of the Siberian Coast. The 1.5 km trajectory stretches back to the coast. The 3.0 km trajectory is different in that it goes to the southwest in the Chukchi Sea in two days, and then curves eastward over to Alaska indicating that air from this level originated 3-6 days earlier on Alaska's North Slope. The higher level air, 6 and 9 km trajectories, go to the west into Central Siberia.
The trajectories to Barrow show the low level air, surface to 1.5 km, coming from Beaufort Sea to the east. The higher level air, 3.0 to 9.0 km, came from a different location - the north Pacific Ocean crossing Alaska enroute.
