Dusty Sunset..

..will be playing your favorite western tunes in the inimitable style of Johnny Cash at the Whistling Cactus Bar and Hitching Post this Friday and Saturday…  :}   (Hahahaha;  “inimitable style of Johnny Cash”; that means Cash’s style can’t be imitated!)1

6:37 AM: I see now that there’s a lot more dust than last evening! Wow. Dusty Sunrise!

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4:13 PM. Cumulus fractus. Dust is visible if you look hard on the horizon. The back scattering of sun light from dust aerosols makes them hard to detect looking away from the sun. But looking toward the sun, the sky has a whitish, gritty look as we had yesterday. When smoke aerosols are present, the sun can appear very orange or reddish, not white in the mid-day-afternoon hours.  See the photo below, taken in the forward scattering direction, that whitish look near the sun.  For those who want to go deeper, this.  Images here.
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4:12 PM. Whitish, gritty dust exits Tucson and envelopes  Mark Albright’s house in Marana/Continental Ranch, carried on a SE blast of wind from Texas and NM.

 

6:11 PM. Same view as above but most of the sun's white light has been scattered out leaving the longer yellow and orange wavelengths to carry on.
6:11 PM. Same view as above but most of the sun’s white light has been scattered out leaving the longer yellow and orange wavelengths to carry on.
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6:20 PM. Classic appearance of a dusty sunset.

 

Satellite image of aerosol content as seen from above (:}. Green area is the dust plume that appeared to originate in SW Texas and southern NM, then blew into Tucson town yesterday afternoon.
Satellite image of aerosol content as seen from above (:}. Green area is the dust plume that appeared to originate in SW Texas and southern NM, then blew into Tucson town yesterday afternoon.  Looks like its still here this morning.  Go here to see more jpegs of aerosols.

Today’s mix of clouds and dust

Cloud action today, likely some small Cu and Ac later today as a weak upper level trough approaches and passes over us.  Should be enough clouds around to pose a sprinkle threat.  Imagine.

Should be an especially interesting day for cloud watchers since the dust aerosol should get into the small Cu.  Sometimes that can lead to much larger cloud droplets in them because the dust particles are so much larger than the usual aerosol stuff that gets into our clouds.

What does that mean?

Will help those lower Cumulus clouds to form raindrops, since the larger the cloud droplet, the higher the temperatures at which ice forms.  Sometimes, even drizzle drops, formed from just droplet collisions can result in  Cu mediocris clouds with large dust particles in them (no ice involved).  Would sure like to have an instrumented aircraft in the clouds of today!

Normally, ice would be expected to form at temperatures below about -10 to -12 C here in AZ.  Today, it might be higher with virga falling from shallower clouds than usual.

 The weather ahead

Found some rain for ya…  March 21st.2014031300_CON_GFS_SFC_SLP_THK_PRECIP_WINDS_216  See those green areas in SE AZ?  Been quiet on rain lately.  Don’t like to talk about rain when there’s none indicated for two weeks at a time. The rain shown for us on the map above has been coming and going around this date in the model runs, mostly going, actually, but scored one here based on yesterday’s 5 PM AST global data and that has allowed me to take the rain muzzle off.

So….in sum, we can look forward to another chance of rain in March, one just ahead, and, of course, more of “Dusty Sunset” in the meantime leading up to this chance.

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1Saw a vinyl record album with those EXACT words on it in the Durango Market  on Main Street, Durango, back in the ’70s when I lived there.  Pretty funny, because you KNEW that imitating Johnny Cash was exactly what that singer was going to do!

 

By Art Rangno

Retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.