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Author Topic: Atmospherics and visibility  (Read 9199 times)

John Hart

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Atmospherics and visibility
« on: July 13, 2012, 03:24:27 PM »

I wanted to put this here as it ties in to the question of where were they and why did they not find Howland.  I am going to try to post some pictures, based on more reading in FAQ I think I know how.  I will try to use them to illustrate my point.  I will post one and if it doesn't work or I blow the file size rules I'll wait to hear the wrath of the moderators and cease and desist.  I hope there are no WX guessers on here as they will probably attack my weather knowledge.

We did one of the best picture taking flights of my career in 2001.  I was flying the 2-seat F-16 from which the pics were taken and have the original digitals.  I will post lower resolution to try to keep file size down.  We went from Homestead AFB FL SE to a low level route that follows the Keys about 5-15 miles off shore.  It was AM, very calm (unusually so), hot summertime.  Through the duration of the flight the normal convection created haze in the 1500-2000 range, then CU started to build, and by the time we flew back from out by the Dry Tortugas 1.5 hours later they were well on their way to being thunderstorms.

First pic, beginning of flight, about 2000-3000' about 7-10 miles W E of Key Largo (that is it in the background assuming this posts and you can see it) looking W.  Note the haze washing out the vis at low angle but still clear looking down at sharper angle at the sailboat under the nose of nearest airplane.  Also on horizon CU (puffies) are forming (over land first).  Also note washed out appearance of the water below and remember that for next picture if this works.
« Last Edit: July 13, 2012, 05:03:11 PM by John Hart »
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John Hart

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Re: Atmospherics and visibility
« Reply #1 on: July 13, 2012, 03:27:37 PM »

Wow, it worked.  Some errors in the text.  It is taken from E of Key Largo looking W.  Will standby for moderators to hammer me or not before posting any more.  Also, spell check works on my other computer but not this one....can't figure it out but appologies for errors.
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Gus Rubio

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Re: Atmospherics and visibility
« Reply #2 on: July 13, 2012, 03:35:33 PM »

What a great pic!  I'm jealous that you flew F-16s, but in the good way.   ;)

Any idea how big the section of land in that pic is? 
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John Hart

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Re: Atmospherics and visibility
« Reply #3 on: July 13, 2012, 03:39:26 PM »

Key Largo is about  1-2 miles across there.
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John Hart

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Re: Atmospherics and visibility
« Reply #4 on: July 13, 2012, 03:52:31 PM »

Will discuss transmissivity while waiting for the go ahead for more pics.  Again, any WX guessers on here I apologize profusely and bow down to your eminence. 

Different wave lengths of the light spectrum are reflected/absorbed differently.  Visible light is only a tiny portion of that spectrum.  We use Infra-Red (IR) and Near-IR in targetting systems  to account for this.  What can't be seen well in one spectrum may be easier in another.  Our Targeting pods use both visible (electro optical called EO) and IR.  Our Night Vision Goggles (NVGs) are Near-IR.  Our WX folks had to be able to forecast transmissivity.  How much EO and IR would be affected by atmospherics.  So you knew which sensor you could expect to work better.  At night you are stuck with IR and Near-IR.  As a result you got good at predicting what vis would be to find your target.  Something AE and FN did not have.

It is that background knowledge that I bring to thinking about what the WX was like and what the Vis was like for them.  If you were standing on Key Largo looking back at us your vis would be different as you would be looking up into the sun with a blue sky background.

MTF

JB
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John Hart

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Re: Atmospherics and visibility
« Reply #5 on: July 13, 2012, 04:10:11 PM »

No moderator wrath so hopefully I am OK so will put up another.  This is several miles later as we turn the corner around from S heading to SW.  We have descended down to 500-700 feet.  Note how calm it was as the water is like glass and you can see the seaweed and coral on the bottom.  Much clearer as we have descended below the haze layer at 1500-2000'.  Relate that back to the same water in the earlier picture...not so clear.  Due to camera angle you can't see the horizon but if you could that same haze affect would hamper your ability to see the Keys to the NW of this location.
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John Hart

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Re: Atmospherics and visibility
« Reply #6 on: July 13, 2012, 04:23:45 PM »

OK, I will admit to posting these for the simple cool factor.  The best two in the bunch.  But they do not show anything to illustrate my point as they are looking down into the water that was so smooth as to be like glass.  This is one of two sunken ships about 4-5 miles W of the Marquesas (about 35 miles W of Key West) at the end of the low level we flew.  These were used as bombing targets by us and Navy till they found Atocha fleet remnants near and cut off all bombing.  This ship has the mast and part of the structure sticking above water.  But due to the haze problems we had a hard time setting up the shot as we could not see it from very far away due to the haze.  So we would get very near before we would see it and need a lot of maneuvering to position ourselves properly to frame the shot.  That required some hard turns and G's.  The old photographer in my back seat was having a hard time and groaning a lot.
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John Hart

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Re: Atmospherics and visibility
« Reply #7 on: July 13, 2012, 04:31:52 PM »

OK, last two.  First is over Fort Jefferson in the Dry Tortugas at about 5000' about 4-5 miles away.  Same conditions as previous but notice that looking down at a sharp angle through the haze changes the vis and it is much better.  Also notice how near the horizon is more washed out by the haze.  The second pic is on the way home over the Everglades as the puffies are building and the haze is getting deeper and worse.  Within hours those will be massive thunderheads reaching to +30K'.

No way to predict where in that heating cycle of convection the CU N and W of Howland was but I guarantee if it was there the haze preceded it.

TWW,

JB
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Anthony Allen Roach

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Re: Atmospherics and visibility
« Reply #8 on: July 13, 2012, 09:42:13 PM »

Outstanding photos.  I think you and I are on the same sheet of music.  I spent the afternoon on the phone with one of my classmates who flew the P-3 Orion on Marpat and anti-sub patrols.  I was hoping to get some firm figures on how far away he could see an island like Howland at various altitudes.  He of course had more questions for me than had for him.  He wanted to know about weather and visibility.  We discussed haze.  He pointed out that it is sometimes difficult to see Catalina Island from 26 miles away on the surface, due to haze.  He remarked that it is easier to see an island with some sort of mountainous terrain, using Diego Garcia as a example, than it is to see something flat.  I did ask point blank if someone could see an island from 200 miles away.  He laughed and said "only from space, and then it had better be a big island."  Your photos illustrate the haze concept really well.  (Plus they are great photos of the F-16.)

I started sending him links to bring him up to date on the search for the Electra, and I hope to hear from him more this next week.  Your pictures illustrate the ideas and points he was making.
"Six the Hard Way."
 
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Gary LaPook

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Re: Atmospherics and visibility
« Reply #9 on: July 13, 2012, 11:15:36 PM »

Outstanding photos.  I think you and I are on the same sheet of music.  I spent the afternoon on the phone with one of my classmates who flew the P-3 Orion on Marpat and anti-sub patrols.  I was hoping to get some firm figures on how far away he could see an island like Howland at various altitudes.  He of course had more questions for me than had for him.  He wanted to know about weather and visibility.  We discussed haze.  He pointed out that it is sometimes difficult to see Catalina Island from 26 miles away on the surface, due to haze.  He remarked that it is easier to see an island with some sort of mountainous terrain, using Diego Garcia as a example, than it is to see something flat.  I did ask point blank if someone could see an island from 200 miles away.  He laughed and said "only from space, and then it had better be a big island."  Your photos illustrate the haze concept really well.  (Plus they are great photos of the F-16.)

I started sending him links to bring him up to date on the search for the Electra, and I hope to hear from him more this next week.  Your pictures illustrate the ideas and points he was making.
Here are a couple of pictures I posted before.

I have attached a photo of land about ten NM ahead, landfalls are always happy moments.


https://tighar.org/smf/index.php?action=dlattach;topic=447.0;attach=173

https://tighar.org/smf/index.php?action=dlattach;topic=452.0;attach=171


I have attached a photo of some clouds shadows and a ship. Did you have any problem separating the ship from the cloud shadows?

https://tighar.org/smf/index.php?action=dlattach;topic=383.0;attach=175

gl
« Last Edit: July 13, 2012, 11:20:47 PM by Gary LaPook »
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