This is a day lighting study of the done on a rough model, in November. It shows how the day light effects the stairwell space throughout the day . 

Key for the different view of the photos

Morning light 

Mid-day light 

Late afternoon light

View 1 at 10:00am: the light filters very well into the atrium space

View 2 and 3 at

10:00am 

View 4 at 10:00am: the stair is within the shade. 

View 1 and 2 at 1:30pm  the atriumreceives some sun. This should be shaded though louvers