The L. A. suns

We begin today by not talking about sports as the title suggests, but rather examining pretty castellanus, Altocumulus castellanus, that is, from yesterday morning:

5:38 AM yesterday from Equestrian Trail Road.
5:38 AM yesterday from Equestrian Trail Road.


The brighter regions at the top are liquid droplet clouds, below, snow virga as the drops quickly freeze into ice crystals.   As they grow and collide, snowflakes  (“aggregates of single crystals) develop.  But the dry air below the clouds prevents them from falling more than a few thousand feet below those white tops.  Too bad.  This is also what the tops of many widespread rainy/snowy storms look like if you could cut away just the top few thousand feet, those situations where there is moist air all the way to the ground.

L. A. suns?  No, the PHX team did not move to a cooler venue as might be desired on these record breaking hot days.  But our orange suns of late, particularly in the late afternoon, are reminiscent of those sunsets seen in smoky, smoggy regions of which this earth has too many.

6:37 PM.  The smoky orange sunset yesterday.  Ugh.
6:37 PM. The smoky orange sunset yesterday. Ugh.

Furthermore, smoke gets in the way of rain formation, something noted by experimenters as far back as 1957, and later when burning sugar cane in Australia in the 1960s.  The burning there stopped the clouds, relatively shallow ones, from raining.   This is because smoky clouds have more and smaller drops in them.  Smaller drops are resistant to forming ice, and a cloud must become deeper to generate drops large enough to coalescence with one another to form drops big enough to fall out.

So, not only are the skies messed up by smoke, but the formation of rain, too, is interfered with.   Fortunately, if deep thundery clouds form, as we expect today in our vicinity, this smoke effect can be overcome at least in those clouds and rain will fall out.

Also, because small drop clouds send more light back into space from their tops, even moderate-sized Cumulus clouds can look awfully dark on the bottom, suggesting they are deeper than they really are.

The End


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.