Appleman chart vs calculator result


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I have been working with becoming adept with your calculator, and am currently checking out sounding data to see how it compares with Appleman charts. I am using the high bypass Appleman chart, and the particular combination shows a firm 'No' at 300 mb even if the humidity is >100%. And then I use your calculator and get a borderline 'Yes' for persistent contrails.

Am wondering why there is such a disparity in results. I have been relying on Appleman for quite some time, but am thinking your calculator refines it. But this is throwing me for a loop.

Am inlcuding satellite photos in 2 views, COD radiosonde data, and Windy temp and dew point traces. No contrails evident, but this would be mainly to the very 'dirty' airmass full of cirriform clouds at and to the west of Amarillo. The contrails would undoubtedly be just 'absorbed' into the very deep moist layer and been unseen from below or above.

Gave another view a shot, using Mid Level Tropospheric Water Vapor, and I do see a contrail north of Lubbock extending to the southeast, a bit later at 1550UTC. This appears to be resolving towards your calculator result and Applemann not panning out.

I'd appreciate any thoughts.
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Sorry, screenshot of COD had obscured 300 mb data behind the Appleman.


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If I go back to the beginning....this is where it all started. I was searching the charts for a place of likely contrails. Under a ridge of high pressure (not sharp by any dirty), south of a jet core......and not a lot of moisture in a large area at or below 500 mb.

On the 250 mb chart I saw the -40 and a 4 DD and said yes, that is a possible place for contrails. My investigation ensued from that point to where I came into the dispute between Appleman and your calculator.

Anyway, this has turned into TMI, but if anywhere this is where I can go to discuss cirriform clouds. That's why I am here. I'm a former weather guy, US Navy. This is my hobby.


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Meanwhile, next door in Oklahoma, the dispute between Appleman and your calculator is still there. Appleman shows you need about 80% for a contrail. Your calculator shows it is supersaturated with respect to ice. With the addition of jet exhaust there should be a contrail. Yet in the satellite nothing panning out. They should be there and persistent with a DD of 2.3 at near -40 deg C. The moist layer does run from 300 to 250 before it rapidly dries out. Too thick of a moist layer, absorbing the contrail into the clouds. That's my assessment.

Edit at! They are showing up east of the Texas-Oklahoma border. I call this a verification for both your calculator and Appleman.


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It been eight years, so I'm a bit rusty.

But I think the Appleman chart is not really measuring the same thing. My calculator shows when the air is ice supersaturated based on humidity with respect to water, the temperature, and the pressue. Ice supersaturation is a condition for contrail persistence, not formation.

Appleman's chart is to check if conditions are right for the formation of contrails, not their persistence. Contrails were a big problem for military aircraft, regardless of if they persisted or not.

The Appleman chart also makes some assumptions about the engine, which is not something that goes into the calculator.

I fixed the character encoding issue

Older thread:[/rhcalc]
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