Surface Hoar: Dew Caught in the Act!
Did you just call me a surface hoar?
Well, yes, I did.
Surface hoar forms just like dew would on a warmer day. Overnight, as the air cools, it can hold less moisture... and that's got to go somewhere - so down to the ground as beautiful, feathery flakes of surface hoar it goes.
While immensely beautiful, catching the light and forming prefect, hexagonal geometric patterns, surface hoar forms an extremely unstable layer in the snowpack. The feathery crystals stand up side by side, like a row of dominos, waiting to be toppled. With another layer of snow on top of them, a small force - weight added on top from wind-loading, warming, or a skier - can cause them to topple, releasing an avalanche below. Surface hoar, however, is delicate and ephemeral; it is decimated with wind, forms only on clear, cool nights, and is easily melted. Delicate and impermanent, it is a wild beauty of winter.
Well, yes, I did.
Surface hoar forms just like dew would on a warmer day. Overnight, as the air cools, it can hold less moisture... and that's got to go somewhere - so down to the ground as beautiful, feathery flakes of surface hoar it goes.
While immensely beautiful, catching the light and forming prefect, hexagonal geometric patterns, surface hoar forms an extremely unstable layer in the snowpack. The feathery crystals stand up side by side, like a row of dominos, waiting to be toppled. With another layer of snow on top of them, a small force - weight added on top from wind-loading, warming, or a skier - can cause them to topple, releasing an avalanche below. Surface hoar, however, is delicate and ephemeral; it is decimated with wind, forms only on clear, cool nights, and is easily melted. Delicate and impermanent, it is a wild beauty of winter.
Firnspiegel: an oh-so-shiny ice crust
Also known more lyrically as glacier fire, is a shiny beast - cover your eyes! - found in the late spring and early summer in the high mountains. In German, spiegel means window, and firn means older snow. A house with windows of firn spiegel would have some crazy funhouse views! Firn Spiegel only forms at cold temperatures, with high radiative inputs. What does that mean? Only on cold mornings in the summer/ spring, when the sun, high in the sky (versus the lower angle in mid-winter), puts a lot of energy into the surface of the snow. The surface grains of snow melt, but immediately re-freeze, due to the cold content of the snowpack below (probably from the freezing cold night before). Firn spiegel! A window to the soul?
Dust on snow in Colorado, June 2014. It's not pretty - a chocolatey, reddish layer of dust emerging on top of our snowpack in spring and early summer, increasing the solar energy absorbed by the snow. Layers of dust are brought to Colorado in high wind storms from the dry, dusty Colorado Plateau, primarily Utah.
Modeling efforts show that heavy dust loading experienced in recent years has advanced the date of peak runoff of the Colorado River by 3 weeks, as well decreased the overall annual flow of the river by ~5%. That is pretty darn significant; over 27 million people rely on the waters of the Colorado River, in 7 western states and Mexico.
Note the ski tracks on the left of the picture: dusty snow is slushy, melty, gook : ski areas are none too happy about it either, and it may be bringing earlier closing dates and decreased spring skier visits, which uncertain economic impact to Colorado's high country.
Modeling efforts show that heavy dust loading experienced in recent years has advanced the date of peak runoff of the Colorado River by 3 weeks, as well decreased the overall annual flow of the river by ~5%. That is pretty darn significant; over 27 million people rely on the waters of the Colorado River, in 7 western states and Mexico.
Note the ski tracks on the left of the picture: dusty snow is slushy, melty, gook : ski areas are none too happy about it either, and it may be bringing earlier closing dates and decreased spring skier visits, which uncertain economic impact to Colorado's high country.
Avalanche Debris! Oh me oh my-oh, how completely terrifying-o!
This debris pile we encountered on Jones Pass in January of 2014 slid to the ground. What does that mean? A cohesive slab of snow - all of the snow above the ground's surface - broke apart, and slid downhill in a hard slab avalanche.
Here in Colorado, we're a victim of our oh-so-typical October storms. A little bit of early season snow falls, and then temperatures do as well. This tiny amount of snow is subject to a huge temperature gradient - the ground surface rarely goes below 32 degrees F, due to the internal heat of the earth, and the air is regularly in the negatives. This huge differential stresses the snowpack, causing growth of the dreaded depth hoar. This is a beautiful little snow grain - upside down little angular cups - but deadly. A bunch of little cups aren't connected well - think of a pile of dishes versus a pile of marbles. They're more unstable, and prone to tumbling over - releasing the hard slab of newer wind-deposited snow on top of them down onto whatever and whoever happens to be below!
This debris pile we encountered on Jones Pass in January of 2014 slid to the ground. What does that mean? A cohesive slab of snow - all of the snow above the ground's surface - broke apart, and slid downhill in a hard slab avalanche.
Here in Colorado, we're a victim of our oh-so-typical October storms. A little bit of early season snow falls, and then temperatures do as well. This tiny amount of snow is subject to a huge temperature gradient - the ground surface rarely goes below 32 degrees F, due to the internal heat of the earth, and the air is regularly in the negatives. This huge differential stresses the snowpack, causing growth of the dreaded depth hoar. This is a beautiful little snow grain - upside down little angular cups - but deadly. A bunch of little cups aren't connected well - think of a pile of dishes versus a pile of marbles. They're more unstable, and prone to tumbling over - releasing the hard slab of newer wind-deposited snow on top of them down onto whatever and whoever happens to be below!