Biocurious is a weblog about biology, quantified.

Snow mounds on the wood

by PhilipJ on 29 November 2006

It has been snowing with unusual frequency in Vancouver the past few days, with the temperatures staying cold enough that it hasn’t melted away yet. In the spirit of leaves on the ground, I have noticed a new pattern created by the snow that we can all wonder about.

Between the physics and kinesiology buildings there is a courtyard, the ground of which is made up of a lattice of concrete squares with wood between them. The heights are not appreciably different (certainly not more than a centimetre or so), so I’ve been unable to explain the snow patterns on top of them, here:

Pardon the blurriness, but you can see cleary raised mounds over what is the wooden lattice between the concrete squares, quite a bit higher than the baseline snow in the squares themselves.

I see no reason why wind would play a role here, as I mentioned above the difference in height between the wood and concrete is negligeable. The only idea I’ve had is that perhaps snow melts more quickly on the concrete surface when initially falling, while snow that fell on the wood was able to accumulate without melting, leading to more build-up on the wooden lattice. I’m not entirely convinced this is correct, however. Anyone have any other ideas?

  1. Creator_Mergatroid    4161 days ago    #

    I would imagine (hypothesize) a thin layer of ice covers the top surface of the concrete. Did you notice if the snow stayed as snowflakes when landing on the wood when the snow first began to fall, but the snowflakes instantly melted when they landed on the concrete, forming water then ice and lowering the height of the snow compared to the height of the snow falling upon the wood? At the time the photo was taken though, I would have taken snow samples, somehow observe a column of snow above the wooden lattice, and then a patch of snow above the concrete, to compare (the density of) each sample from top to bottom.

  2. Chris    3781 days ago    #

    What could have happened.

    The wood was cooler than the concrete.

    The wood is less dense therfore disipates heat at a faster rate as opposed to the conctrete.

    The temp probably dropped rapidly before the snowfall giving the wood a chance to drop to freezing and not the concrete.

    You can test this theory by taking a concrete block and peice of wood indoors and allow both to reach room temperature. Next place them both next to eachother (touching) outdoors when the temperature is below freezing. Next wait a few minutes and place an ice cube across both of them. If the ice cube melts more rapidly on the concrete then you have a possible answer.

    Transversly you could place them in your ice box on a warmer day and try it… The results should be reversed.

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