Dust on Snow

The short-lived but frequent post-frontal dust storms we've had over the past several weeks have left their mark on the Wasatch snowpack.  

After it snows, the dust is buried, but it doesn't take long for it to emerge as the surface snow melts and the water trickles down through the snowpack, leaving whatever impurities at the surface.  Instead of white snow, it may be "marbled" with areas of tan or brown.  Some people call this "snirt" for part snow part dirt.

Due to the uneven distribution of fresh snowfall and melt rates, the emergence of the dust-laden snow varies.  Today, on this southeast aspect, one saw a very heterogeneous (diverse) snow surface with everything fro white to dust-laden brown.  

Dust is important for snow hydrology because it affects the amount of solar radiation absorbed by the snow.  Dusty snow is darker and absorbs more sunlight, so there is more energy available for melt.  As a result, a dusty snowpack melts faster than a clean one.  I could feel this today on one of my runs.  At upper elevations, the dusty snow was melting and softer, whereas the white snow was still frozen.  

Sadly, this dust is here for the spring.  It may get buried again by Monday's storm, but as soon as that snow starts to melt, the dust will emerge again. 

I'm not a fan of dirty snow.  Not only does it reduce the length of the snow-cover season, but it also makes for unappealing spring skiing.