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    Re: Measuring (and Calculating) Dip
    From: Marcel Tschudin
    Date: 2013 Mar 2, 00:54 +0200
    Brad,

    Regarding the temperature difference you are right to ask:

    Is it

    Air-Water?
    Or
    Water-Air?

    Freiesleben seem not to clarify it. I found the answer in my paper copy of Hasse (1964):

    "An analysis of observations where there are large temperature differences - i.e. cases where the correction becomes noticeable - shows that the dip is greater or smaller than normal if the air is, respectively, cooler or warmer than the water." He mentions further that out of 179 observations with temperature differences greater than 2°C not a single observation did not obey this rule.

    The part in eq. (1) of Freiesleben with delta which corrects for the air-water-temperature difference is deducted from the dip resulting from the height. Because of the minus sign the dip is reduced if delta is positive. This means that delta is the temperature difference air minus water which is also consistent with the temperature difference (Th-To) mentioned several times on page 276.

    Marcel

       
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