Bright Twilights - Volcanically Related

[salbers]

Greetings,

 

Here I have a description of some nice colorful twilights observed and simulated recently.

 

http://laps.noaa.gov/albers/allsky/twilight_volcanic.html

 

Anyone else noticing these?

[donsutherland1]

I'm not sure whether it has any connection to volcanic dust, but below is a photo I shot just after sunrise at Jones Beach on September 19, 2015:

 

[FallsLake]

Read the article called LUNAR ECLIPSE DETECTS GLOBAL COOLING (BUT ONLY A LITTLE):  at:http://spaceweather.com/

[Juliancolton]

Read the article called LUNAR ECLIPSE DETECTS GLOBAL COOLING (BUT ONLY A LITTLE): at:http://spaceweather.com/

Wow, that's fascinating. That explains why I had to boost my film speed a bit higher than expected during totality.

[salbers]

I'm not sure whether it has any connection to volcanic dust, but below is a photo I shot just after sunrise at Jones Beach on September 19, 2015:

 

 

Interesting example of a nice sunset. I'd suggest the crepuscular rays here are more tropospheric as the illuminated clouds are relatively low and close to the rays. Usually volcanic crepuscular rays are more purple rather than orange and show up about 20 minutes after sunset. The clouds causing them are more distant and can even be below the horizon. I'd also look for a brighter than usual yellowish band right near the horizon (also 20-35 minutes after sunset). This might be easier to see than the purple light higher up.

 

And yes, the connection between the volcanic aerosols, twilights and the eclipse is interesting. This is a smaller-scale repeat of what happened back in 1982. I updated my link in post #1 with more info.

[donsutherland1]

Interesting example of a nice sunset. I'd suggest the crepuscular rays here are more tropospheric as the illuminated clouds are relatively low and close to the rays. Usually volcanic crepuscular rays are more purple rather than orange and show up about 20 minutes after sunset. The clouds causing them are more distant and can even be below the horizon. I'd also look for a brighter than usual yellowish band right near the horizon (also 20-35 minutes after sunset). This might be easier to see than the purple light higher up.

 

And yes, the connection between the volcanic aerosols, twilights and the eclipse is interesting. This is a smaller-scale repeat of what happened back in 1982. I updated my link in post #1 with more info.

Thanks for this information.

[salbers]

You bet Don. I've been continuing to make twilight observations. Yesterday was clear with a real spectacle of a display. It started with a prominent Earth Shadow and Belt of Venus, a good sign. Then some purple anti-crepuscular rays started to develop. This all presaged a developing purple glow higher in the west along with a brilliant yellow lower arch. Large (still low to moderate contrast) purple crepuscular rays fanned in the west. The big surprise was a subtle texturing of ultra-cirrus, right near the intersection of the purple crepusclar rays and yellow arch, about 5 degrees high in the west. This is my first ultra-cirrus sighting this millennium.

 

It might be noted that even at the time of sunset, I can generally see an initial stratospheric aerosol signature in the aureole around the sun. It is large and white and more concentrated in azimuth (compared to usual) in the west (as a large semicircle). This is at the same time a smaller orange aureole may still be visible much closer to the sun. In non-volcanic cases, the developing twilight glow isn't so large and white and is more uniform in brightness over the western range of azimuths. In other words, at sunset any orange sky glow is from lower aerosols and the still white component indicates it must be higher. Comparison of the developing twilight with occasional contrails (or isolated clouds) helps provide some insight as well.

 

In another recent case I was able to simulate a purple crepuscular ray case as the right clouds were present in my cloud analysis data to drive the image rendering. The rays showed up in the simulated image, my visual views and some of the camera views. Ultimately camera images or other quantitative sky measurements can be used to retrieve the vertical aerosol profiles.