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srquirrely
Weather Watcher


Reged: Sat
Posts: 32
Loc: SARASOTA 27.27N 82.53W
GLINT
      #95016 - Mon Jun 09 2014 01:20 PM

Just curious... Seems the sun's glint used to track right across satellite loops.
Now I only ever see it over Maracaibo. Thoughts (or info) anybody???


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Ed DunhamAdministrator
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)


Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Re: GLINT [Re: srquirrely]
      #95017 - Tue Jun 10 2014 01:19 AM

This was a great question and I'm sure that many of us have observed this phenomenon - and it took a fair amount of research to figure out what was going on. Finally, with assistance from the satellite loops at Marshall Space Flight Center I was able to piece together an explanation.

The short answer is that the sun glint is only seen (with ease) when the sun passes (overhead) over water. Cloud formations and land masses do a lousy job of reflecting the sun. The sun - relative to the position of the earth - crossed overhead the Equator northbound on March 20, the Spring Equinox. It will be overhead at 23.44 degrees North latitude (The Tropic of Cancer) on June 21st, the Summer solstice - but that is only part of the complex solution of what we see in the satellite timelapse loops. The axis of the earth is tilted from the vertical and the satellite camera is on a geostationary satellite located at about 22,000 miles over the equator. It is positioned to always look down over the same area on the earth - thus the name Geostationary Orbiting Earth Satellite (GOES).

Given all of those various angles to work with, it appears that the sun is reflecting off the earth at the current time at around 8 or 9 degrees North latitude. So for the moment, the sun is shining directly down on clouds associated with the Intertropical Convergence Zone (ITCZ) all the way from the west coast of Africa to the east coast of northern South America. The sun finally reflects off of water west of Panama and the glint can be observed as it reflects westward while passing south of Tropical Storm Cristina in the eastern Pacific.
Cheers,
ED


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srquirrely
Weather Watcher


Reged: Sat
Posts: 32
Loc: SARASOTA 27.27N 82.53W
Re: GLINT [Re: Ed Dunham]
      #95019 - Sun Jun 15 2014 12:20 PM

Ed - thanks for taking the time and interest to respond to my ?
In my (simple) mind, the sun shining 'down' at 23.4N, reflecting back to the satellite over the equator, would result in its glint being observed at 11.7N (In a perfect world). Given whatever variables of angle and tilt, it still seems to appear north of 10N. The ITCZ is pretty much south of that. Cloud cover in that part of the Atlantic looks like a broken mid deck at best, which I would expect to allow the sun to reflect off the water somewhere.
In any case, It USED TO BE observable and NOW it isn't, with the above noted variables largely unchanged.
So... I'm still curious. Or maybe just confused.


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Ed DunhamAdministrator
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)


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Posts: 2565
Loc: Melbourne, FL
Re: GLINT [Re: srquirrely]
      #95020 - Mon Jun 16 2014 01:20 AM

I went back to the MSFC images and checked again. The cloud pattern today is indeed quite thin compared to what it was on the 9th so a glint should be visible - but it only shows up in the Pacific. Under magnification the glint was visible at about 15N latitude from roughly 1945Z to 2145Z west of the Mexican west coast (at 2145Z it was at the edge of the image that I was using) - but nothing is seen in the Atlantic. I'm not into Optics so I'm not sure why. If a 'filter' was in use I would have thought that it would have been applied across the full image. It looks like you have presented quite a mystery.
ED


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Ed DunhamAdministrator
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)


Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Re: GLINT [Re: srquirrely]
      #95134 - Tue Jul 22 2014 08:50 AM

I noticed this morning that the 'twinkle' is back in the Atlantic's eye, i.e., the 'glint' is evident. At 12Z it is seen at about 11-11.5N (to the east of TD2). So sun angles must be involved, but I have no idea as to why it wasn't observable earlier in the NH Summer when the sun would have been directly over the Equator.
Cheers,
ED


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srquirrely
Weather Watcher


Reged: Sat
Posts: 32
Loc: SARASOTA 27.27N 82.53W
Re: GLINT [Re: Ed Dunham]
      #95145 - Wed Jul 23 2014 04:28 PM

I noticed that too. I wonder if sand or other aerosols could be the culprit.

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