Average amount of annual daylight at any place on earth

  • If this is the wrong group please direct me to the correct one.



    It seems intuitively obvious that the amount of daylight per annum should be the same for any latitude on earth. For example, 12 hours per day at the equator. The poles have daylight for half the year and darkness for the other half (crudely).



    Is there any way to get an answer to this apparently simple question - is the annual amount of daylight the same at any point on earth?


  • Wikipedia strikes again:




    The naive expectation is that, for every place on Earth, the Sun will
    appear to be above the horizon for exactly half the time. Thus, for a
    standard year consisting of 8760 hours, apparent maximal daytime
    duration would be 4380 hours. However, there are physical and
    astronomical effects which change that picture. Namely, atmospheric
    refraction allows the Sun to be still visible even when it physically
    sets below the horizon line. For that reason, average daytime
    (disregarding cloud effects) is longest in polar areas, where the
    apparent Sun spends the most time around the horizon. Places on the
    Arctic Circle have the longest total annual daytime of 4647 hours,
    while the North Pole receives 4575. Because of elliptic nature of the
    Earth's orbit, the Southern Hemisphere is not symmetrical: Antarctic
    Circle at 4530 hours receives 5 days less of sunshine than its
    antipodes. The Equator has the total daytime of 4422 hours per
    year.




    Further details here on astronomical causes of average daytime variation, and here on Insolation, the solar radiation received at the top of the atmosphere and its effects on the energy received at ground level.


    Thanks for the above - a supplementary. Presumably the number of daylight hours on other places on the globe - London for example - will somewhere between the polar and equitorial amounts?

    @peter Smith yes. As it says in the answer the exact relationship of daylight hours with latitude depends on many astronomical and physical effects, such as the atmospheric composition to allow refraction. However the number of hours in both hemispheres will at least be between their respective poles and the equator.

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Content dated before 7/24/2021 11:53 AM

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