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    Re: Refraction. was: Bubble Horizon Altitude Corrections
    From: Robert Gainer
    Date: 2004 Jul 7, 20:05 +0000

    Temperature inversion in the San Fernando Valley, California.
    >From: "Trevor J. Kenchington" 
    >Reply-To: Navigation Mailing List 
    >Subject: Re: Refraction. was: Bubble Horizon Altitude Corrections
    >Date: Tue, 6 Jul 2004 23:31:37 +0000
    >I always hesitate to find fault with George's postings because it
    >usually turns out that the error is mine. However, when he writes:
    >>If there was a temperature
    >>gradient in the air, the temperature falling fast enough as height
    >>increased, that could in theory be enough to counteract the effects of the
    >>falling pressure. In that case the air-density would conceivably increase,
    >>not decrease, as height increased, which could cause light to be curved
    >>upwards, not downwards; the effect that I think Fred is looking for.
    >I have to ask: George, if the density of the air increased with
    >altitude, what would stop the dense air from descending and displacing
    >the lower-density air upwards?
    >Sure, air masses can be unstable and we do see down draughts and rapidly
    >rising air (as in cumulus clouds). But can enough high-density air
    >really sit on top of low-density air for the usual direction of
    >refraction to be reversed?
    >Trevor Kenchington
    >Trevor J. Kenchington PhD                         Gadus@iStar.ca
    >Gadus Associates,                                 Office(902) 889-9250
    >R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    >Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
    >                     Science Serving the Fisheries
    >                      http://home.istar.ca/~gadus
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