Was it smog or dust? How to tell

OK, climbing down off soapbox today….just don’t read the Hockey Stick Illusion by A. W. Montford unless you want to be upset by some climate scientists pretending to be scientists when they are being something antithetical to science.  Reminds me of the 30-odd years of cloud seeding reanalysis experiences I had as a skeptic in that domain.  Oops, haven’t climbed completely down yet.  Montford should get a Pulitzer for this well documented tale, and his main protagonist, Steve McIntyre, the Rossby Medal or maybe a couple of Nobel Prizes for diligence.  Just about off “box” now….but this tale REALLY does remind me of the shenanigans that happened in cloud seeding to repeat myself again and again and again.

It got pretty hazy yesterday afternoon into the time of sunset.   This is what it looked like as the sun rotated away from the earth (hahahah).  Note the yellowish tinge of the sun.  Smog (urban, biomass smoke and hazes, are comprised of smaller aerosol particles, around a 0.01 to 0.1 microns in diameter, whereas dust particles, something that you find around the house everyday here in AZ (to quote Groucho Marx from his quiz program, “You Bet Your Life”) are generally much larger and can extend into sizes of  1-10 microns in diameter.    So, in interfering with the transmission of the incoming white sunlight, small aerosol particles in smog take out (scatter) the short wavelengths like the blueish ones) and only the longer wavelengths, the reddish ones,  giving the sun an orange or reddish hue.  Dust particles, because they are larger, and do not interfere with the short wavelengths of light coming from the as much produce a whitish yellow colored sun.   Below yesterday’s sunset is a smokey one from Cuiaba, Brazil,  during the burn season, a strawman to show a large, obvious difference.  It’s often more subtle than this, so you need to practice labeling sunsets for aerosol sizes.  Your neighbors will be impressed.

Since dust particles are larger than smoke particles, they don’t stay afloat as long as smoke particles do, though dust can still drift away from where it was generated before dissipating.  It depends on the nature of the surface dust.   In Saudi Arabia, dust was often observed without much wind due to the fine nature of the sand (see last photo from Qassim, SA–looks pretty much like pure dust whereas the Catalina sunset suggests dust with smoke due to its more orange coloring).

Factoid:   some Gobi Desert dust has impacted the West Coast of the US from time to time!

Clouds?  Well, if you looked, you saw a few low cloud shreds called Cumulus fractus (Cu fra) over the Catalinas yesterday afternoon.  Some rain fell as close as central AZ as a cold front blew by.  But only the cooler air got here.  Its 13 deg cooler here than it was yesterday at this time (4:30 AM LST), a sure sign of an air mass change and “fropa” (frontal passage).