Questions on flux computation in Eddypro

Environmental Forum Forums EddyPro Questions on flux computation in Eddypro

This topic contains 1 reply, has 2 voices, and was last updated by  IsraelB 8 months, 2 weeks ago.

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  • #8093

    hamidreza
    Participant

    Dear Eddypro members

    I would like to use Eddypro to analyze the measurement data.
    I have a mast with one CSAT3B Sonic anemometer and temperature/relative humidity sensor at 10m, one CSAT3B and temperature/relative humidity sensor at 5m and one CSAT3+EC150(gas analyzer) and temperature/relative humidity sensor at 2 meter. The data are recorded at 50Hz frequency but unfortunately the information of the relative humidity sensors at 5 and 10 meters are not stored in the data logger.

    So I have only the information of the sonic anemometers at 10 and 5 meters but I have all available information at 2 meter (Ts, ambient temperature and pressure, H2O and CO2 concentration, etc. ).

    I introduced all the devices (anemometers in Instruments/Anemometers info and the gas analyzer in Instruments/Gas Analyzers info) in Eddypro and tried to calculate the fluxes at 2 meter using only the basic settings.
    In “Basic settings” I can “select items for flux computation”.
    Since I have all the informations at 2m, I selected the ambient temperature and pressure (from other instruments since there is no section to introduce sensors, but I set them in “raw file description” to be regarded as values at 2 meter). Eddypro calculated the uncorrected fluxes using sonic temperature and modified that afterwards. It’s not clear to me, to calculate the corrected fluxes which temperature(the virtual temperature or virtual potential temperature) is used in Eddypro?!

    However if I want to calculate the fluxes at 5 or 10 meter, the ambient pressure and temperature data are missing. Should I set the ambient temperature and pressure to “none” for 5 and 10 meter level or use the one at 2 meter? (The results of these two cases(setting to none or using the existing information) are slightly different).

    In the user manual, the Monin-Obukhov length is defined based on potential temperature and uncorrected fluxes while in most literatures virtual potential temperature and the fluxes calculated with virtual potential temperature are used. This is a bit confusing to me, would you please let me know if you have any estimation of the difference between these two approaches?

    I would be happy if you guide me to solve these issues please.

    Kind regards,
    Hamid

    #8128

    IsraelB
    Keymaster

    Hi Hamid,
    Sorry for the delayed response we were having problems with posting on the forum.
    If you are still looking for an explanation here are some ideas
    1. Regarding what temperature to use at 5 and 10 meter – the choice is up to you. If you don’t specify an ambient temperature then EddyPro will use the sonic temperature and correct it for humidity.
    2. There are iterative corrections in EddyPro so I imagine that value will be updated when the inputs are update. However I will need to confirm and let you know.

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