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Thread: Evaporativhe heat flux bulk method --- baffled by units

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    Evaporativhe heat flux bulk method --- baffled by units

    Dear Forum,

    I have a serious understanding problem with the bulk method for estimating evaporative heat flux.

    From my understanding the following holds (using a measured average evap rate):

    QE = Lv * dens_air * Evap_rate

    Lv = 2,462,735 [J/kg]
    dens_air = 1.22 [Kg/m3]
    Evap_rate = 4 [mm/day] = 4/(86,400*1,000) [m/s]

    This yields QE = 0.14 [J/(m2s)] = 0.14 [W/m2]

    However, this value is 3 magnitudes too small. I assume that the density of water might be missing (1000 kg/m3), but all the formulas in the lit. I found use the density of air.

    Thank you very much in advance for your help.

  2. #2
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    The evaporative heat flux results from the exchange of water between the ocean and the atmosphere. In the atmosphere, water is water vapour.
    Your relationship does not take into account either the water vapour or the ocean temperature.

    If you are using Matlab, I would suggest using the air-sea toolbox: http://woodshole.er.usgs.gov/operati.../hfbulktc.html

    Cheers,
    Olivier

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