The air speed in the stairwell vestibule on the third floor of the Knight Library's circular stairway is greater than the ASHRAE's acceptable level of 40 fpm, the highest allowable air speed without effecting the comfort zone.

Questions

What causes the significant breeze?
Is the threshold doorway what causes it to be much more noticed?
Does the fact that the threshold opens back up again matter?
Is the air following the stairway all the way up to that doorway?
Why the enclosure only between the 3rd and 4th floors?
Is the air pleasant or annoying?
Why is it noticeable?
What is the pattern of air movement?