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Re: Anomalous dip. was: [NAV-L] Testing pocket sextant.
From: Marcel Tschudin
Date: 2006 Jun 16, 17:15 +0300
From: Marcel Tschudin
Date: 2006 Jun 16, 17:15 +0300
On 6/16/06, Alexandre E Eremenko <eremenko@math.purdue.edu> wrote:
> I guess you ment -0.0065 ?
>
> Alex wrote:
> "The water was very cool (and always is) here. I mean most people do not
> dare to swim in Kiel till the beginning of August:-) But the air was hot, at
> least that was what I felt:-)"
>
> Isn't that just the type of condition to create a high temperature gradient?
There is some confusion here. Under the conditions I described,
the gradient will be high indeed, but in what direction?
The air is cooler nearer the surface. That is the temperature
INCREASES with height. If I understood George's message
correctly, "inversion" that can lead to positive dip
occurs when we have the opposite phenomenon: the temperature
DECREASES with height.
Ducting occurs also with strong inversions, i.e. in cases of large lapse rates with a positive sign. Or, more general, when sinZ (would) become >1.
Marcel
