In the meantime, as can be noticed (although not as easily as in other photos the reader may come across) in the companion photo, the Valley of the Sun is often partly (or more) shrouded in smoggy haze. The particle pollution that causes this so-called "Brown Cloud" over Phoenix is a major concern, and has resulted in the U.S. EPA declaring Maricopa County a "serious" nonattainment area for PM-10 pollution.* Factors that contribute to increases in particle pollution include the use of lawn equipment such as leaf blowers, dust kicked up by automobiles and construction, and wood-burning fires.
(*"PM-10" refers to particulate matter pollution, generally composed of small particles including "acids, organic chemicals, metals, and soil or dust particles." The "10" measures inhalable coarse particles between 2.5 and 10 micrometers in diameter.)
Look for the next entry soon, which will consider Phoenix's air quality problem in connection with recent holiday restrictions on residential wood-burning fires imposed by Maricopa County.