Excerpt from WP page Snow line:

"At or near the equator, it is typically situated at approximately 4,500 metres (14,764 ft) above sea level. As one moves towards the Tropic of Cancer and Tropic of Capricorn, the parameter at first increases: in the Himalayas the permanent snow line can be as high as 5,700 metres (18,701 feet)..."

Why does the snow line increase? Logically, shouldn't it decrease the farther you go from the equator? Or is the 14,764 ft figure meant to be the average snow line rather than the permanent one and the "at first increases" quote is a misinterpretation?


1 Answer 1


The permanent snow line is controlled by summer insolation, and during the summer the insolation is higher at 30°N than at the equator. See this figure from Fundamentals of Physical Geography (Pidwirny, 2006):

enter image description here

You can see that the 30°N latitude (roughly that of the Himalayas) gets higher insolation than the equator from mid-April to end of August, which is enough time for the snow to melt in the summer at higher altitudes. Higher latitudes also get more insolation than the equator in the summer, but for a much shorter amount of time, which is why the snow line trend decreases after the tropic.

  • 1
    $\begingroup$ I would not have imagined that the highest daily insolation would occur at a pole, though in retrospect it makes sense given the lack of a solar night. This is a terrific example of surprises in science, thank you. $\endgroup$
    – dotancohen
    Commented Dec 8, 2021 at 7:47

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