Wind + rain

[Sugaree]

A lot of folks were saying rain and wind is worse than plain rain. Can someone in the know explain why?

[castlerock]

Got a convection oven?


It is the same as windchill in the opposite thermal direction. 10 degrees and no wind is fine. 10 degrees and 30 mph wind is cold. It is due to the flux of the convective medium (air) across the snow surface.

Wind and warm adds more heat to the snow, melting it faster. The same as more cold air across your skin freezes it faster.

[Hawk]

And if you want to speed things up even more just add fog. Warm wind with moisture added melts snow even faster than straight sun.

[castlerock]

And if you want to speed things up even more just add fog. Warm wind with moisture ......

True, I was going to add specific heat capacity to the discussion, but didn't want to complicate it. Water has a much higher SHC than the basic gases in air. As such it can take more or impart more heat.

[Hardbooter]

Evaporation.

I've heard from ski area people that high wind with no rain can be worse for snow loss than a light rain with no wind. Snow can evaporate from a frozen state (it doesn't need to melt first.) I think that's also why we often see the snowpack condense during periods with no new snow and the crystal structure of the snow changes as it condenses which packs it tighter. I'm pretty sure that the last three weeks were a good example of that. We got very little new snow and our base shrank considerably. My guess is that that was mostly from evaporation in the cold dry air.

I'm no expert. Just an observer.

[smootharc]

you guys are going to suggest gravity really exists. Sheesh. As if my pea-sized intellect can handle even half of your PhD level course in Evaporational Meltology. My thinker hurts.

Anyone got a brown sugar cinnamon Pop Tart I can eat while I skip class to play frisbee and commune with The Wailers ? That might help my brain pain. Oh, crap, it's not 1984 anymore, is it ?

Who's got the Cliff Notes ?



P.S. Funnin' aside....interesting stuff that I'm thinking I somehow should have known, but certainly did not.

[castlerock]

Booter, I think the correct name for the process is sublimation. Google "triple point" and one can find the details. The snow pack will condense of its own weight probably more than by sublimation at least at our atmospheric pressures. At altitude, with nice dry conditions working on crystals, (out west) it can go pretty fast. And in addition the crystals loose their "edges" and turn to sugar, which makes an unstable layer. (also hoar frost can occur on top, etc....)

[Hardbooter]

Yup sublimation, that's it. I think it's not just the pressure that is required though when it comes to real world mountain conditions. From snow/mountain people that I've talked with, it sounds like a windy but dry winter day will suck up a lot of snowpack. Maybe it's moisture in the snow or it changes the crystals or something. I don't really know (after a few beers the details get fuzzy.) All I know is that after I heard about that, a few years back, I've paid a lot more attention to the snow pack and the moisture level and the wind's effect on the overall amount of snow and it seems to hold true.