Blue Sky Target Days
The Brown Cloud Summit of 2000 identified strategies to improve visibility in the Phoenix metropolitan area. One of the Summit enacted recommendations required ADEQ, with public input, to establish a visibility standard and methods to track visibility improvement in the Phoenix area.
In accordance with the Summit's enabling legislation, House Bill 2538, adopted in May 2001, ADEQ created the Blue Sky Index as an interim reporting mechanism until the visibility index could be developed. The Blue Sky Index is a 12-month rolling list of the number of Blue Sky Days in Area A (Phoenix metropolitan area). A "Blue Sky Day" means a day during which the six-hour average visible range, as measured by transmissometers that ADEQ operates, is 25 miles or more.
As a result of state and federal programs to fight air pollution, it is expected the number of Blue Sky Days reported for Area A will increase over the next few years. The target numbers for the years 2001 through 2003 are:
250 Blue Sky Days in 2001
260 Blue Sky Days in 2002
275 Blue Sky Days in 2003