Category Archives: Optical depth

Another big Cirrus streamer from the Equator heading our way!

Well, when there’s no rain in the model predictions for 15 days, you have to get excited about something….

Like a solar flare, there has been another massive ejection of high clouds from the equatorial region and its heading toward Catalina, AZ.   Here, from the Washington Huskies Weather Department1,  is a 24 h loop of the event.  Hope our cell phones still work.  Here’s the latest still image:

Satellite image for 3:30 AM AST supplemented with various interesting annotations, some of which are correct.


What are the ramifications of ejected Cirrus coming all the way from the Equator to Catalina?  Pretty skies, sunsets and sunrises, which is quite important to us humans.  Also, when it starts arriving today, we’ll have milder nighttime temperatures.  Yes, even Cirrus clouds cut down the outgoing longwave radiation leaving the earth’s surface at night, and of course, moderates the incoming visible (shortwave) radiation (sometimes called “sunlight”).  We don’t want to dumb this down too much.

After 9-11,  when all the aircraft stopped flying for a week some guys at a small university, one so small I don’t think it even had a football team,  found that the daytime and nightime temperatures were affected by the lack of contrails.  Daytime temperatures were a spec higher and nighttime temperatures a tiny bit lower, suggesting that even CONTRAILS have an effect on the weather and climate.  It was an important finding.  Of course, without a football team I am clueless, as are you are,  concerning what university those findings came from.

You know what gets a lot of us scientists about that contrail study after 9-11, is that something simple and important was done that I (we) could have done had only we thought of it.  We’re kind of bitter about it.  Might have got a raise, too, got the name out there.   Citation index fluffed up some.  We’re dealing with a lot of loss here.  Heck, you probably could have done this, too, it was that easy.

The study of contrails is a pretty big topic these days, though the effects are deemed small for the present.  Here’s a short article for you.  Here’s an unrelated one, one about smog’s effects on clouds, but one you should read, anyway.  Might be true.  Reading the second one is like doing an extra pushup.  Its good for you.  And me since one of the authors of the second article (Danny Rosenfeld) criticized me (and Pete Hobbs) royally in print in the late 90s only because we said his work was invalid.  Show’s I’m magnanimous, following the ideals of science meaning that as scientists we have no personal feelings about our detractors.

Yeah right.  Check the climate blogs and those ones who refuse to allow other scientists to even comment on their work!  Its a hideous situation out there now, far from the ideals of science where one WELCOMES criticism.  But, I diverge….getting worked up when I should be concentrating on clouds.

BTW, that little blob of clouds north of the ice cloud mass coming at us, is due to a little disturbance that will hit the coast of Cal in a few days.  With it, the clouds here will get pretty thick, probably as will happen later today or tomorrow with the ice clouds, causing the optical depth to exceed 4.00000000000 (4).

What does an optical depth of four mean?

That means that the sun’s position is not discernable.  (Also, can’t be a Cirrus cloud, BTW, but rather Altostratus if its an all ice cloud).  Optical depth is usually something used by the smog folks.  A really clean sky has an  optical depth of 0.05 or even less.  Smog laden skies, such is the coastal areas of southern California, or back East on humid days in the summer, have optical depths of 0.2-0.5 at times, horizontal visibility might only be a mile or three; the leaves are gray and the sky is brown, as the song says.    Aren’t we happy we don’t have that kind of smog?

Looking way out, just now, I saw this in the ensemble of spaghetti, thought you should see it, too.























While no weather beyond warm breezes and high clouds is portended here, where would you really like to be in the West in two weeks or so for some really heavy rains?  Can you tell?   What’s a place I mention too many times when comes to Cal rains?  Yes, the King Range around Shelter Cove, between Frisco and Eureka.  This plot gives high confidence to major flooding in northern California in the 10-15 day window.   Why?  Because so many of the blue lines (564 dm height contours) dip down toward the tropics in the eastern Pacific in support of the actual forecast from last night (represented by the yellow lines). Remember that the blue lines result from small errors put into the model runs at the beginning to see how robust a forecast is.  The wilder the spread of the lines, the less reliable a forecast is.  The more they group together, the more robust, more reliable a forecast is. They look fairly bunched up in the eastern Pacific, and this is the reason for having this plot here today.   I suspect we’ll be reading about heavy rains in Cal during that 10-15 day window.  It will be fun to see if we can make such a call so far in advance!

The End.






1Nobody knows your university by its scientific accomplishments, but only by its athletic accomplishments.  Its been written up. I certainly wouldn’t.  If online universities could have football teams, it might be the end of “brick and mortar” universities.