Sunday, February 10, 2013

Wind crusts and all that snow

What: I went for a walk with Jon yesterday and while there was certainly a lot of snow on the ground, almost all of the snow in the trees had come down. I started thinking about all of the other ways I might observe wind. I was at Rock Point Friday night and by Saturday morning the winds had picked up and cleared out the thin layer of slush in Little Eagle Bay (what we call Mink Bay) and replaced it with stacks of ice plates. The winds picked up all day and by the afternoon they were stinging our noses. Because of the cold, the snow was "dry". But the wind had dried the snow right up, and sure enough it slid right off of railings, my car, and anything else it was perched unto.

The dryness of the snow meant that by late morning almost all the snow had come down off the deciduous trees and conifers that weren't sheltered by other conifers. I tried to capture the grace of snow clouds drifting whimsically through the woods but couldn't quite get it. I think it needed video.

Deep wells had formed at the base of most of the larger trees indicating sustained unidirectional winds that had carved gullies where eddy currents downwind of the trees. The trees all had gullies on the south sides, and sure enough our winds were out of the north.

Jon commented on the lack of scale with snow. I think topography is one of the easier things to confuse my sense of scale. Looking at ripples in the sandy basin of a river I can easily imagine running across sand dunes. Looking down at a snowy aster poking up through the snow I was immediately transported out onto the vast open tundra.

Ecological notes: Crusts on the top of snow form in three ways. 1) Sun crusts (aka spring crusts) form when the sun melts surface snow, which then refreezes. 2) Freezing rain: supercooled rain falls and freezes when it hits the snow surface, forming a solid crust (other surface water processes could be included here), and 3) wind crusts, which form as wind breaks up flakes and packs them together.

No comments:

Post a Comment