(a) Tabuk
(b) Mecca
(c) Dhahran
(d) Rub al Khali Desert
Figure 2: Time series plot of MODIS AOD at 550 nm using Terra and Aqua over (a) Tabuk, (b) Mecca, and (c) Dhahran and Aqua Deep Blue data over (d) Rub al Khali (Empty Quarter) Desert.