Dark lines in melting snowpiles

March 30th, 2019
Snow cleared from a city street slowly vanishes, leaving lines of "dirt". [image:131] (Click on images to view more closely.) Where the snow has a distinct edge, you can see the dark lines are ridges, some of which can be quite sharp: [image:132] Why is… more »

Poster on corner pockets in snow crystals

February 18th, 2019
Last July, I attended the AMS (American Meteorological Society) 15th Conference on Cloud Physics, which was combined with a similar conference on atmospheric radiation. They have these about every four years, but I have missed all those going back to… more »

Puddle gets its grooves (upon freezing), part I

February 16th, 2019
These grooves appear on the surface of frozen puddles. [image:111] Most grooves are straight lines, and most of these also appear to have relatively symmetric sides, such as those marked #s 1, 2, & 4 in the above image. But some, such as #3, have… more »

Strange dry shadows

February 14th, 2019
Sunshine on pavement seems straightforward enough. It warms the surface, driving evaporation (or sublimation), and dries things out. Conversely, we know that moisture tends to collect on surfaces that are either colder or closer to a water source. And… more »

A rare heliac arc? (plus six others)

February 5th, 2019
The day starts sunny and bright, but later you note a slight muting of the surrounding landscape. It is still bright enough, but you feel less heat bearing down. Apparently, a thin veil of high clouds has slowly and silently appeared above. When this… more »

Bad Snow, Part II, and Some History

December 11th, 2017
The recent post about bad snow (see new emblem at bottom) reminded me of an old image that often pops up in historical descriptions about snow. The date was 1555 and Olaus Magnus, an archbishop in Sweden, just published "Description of the Northern… more »

Film frost grains and radiative cooling of the ground

December 10th, 2017
December 8th brought the first frost to the Seattle area. This doesn't mean that this is the first time this season that the ground reached 0 degrees C or lower. True, we had gotten snow in late November, though this by itself doesn't mean the ground… more »

Bad Snow

November 28th, 2017
This post is about the misrepresenting of snow crystals in public, not about misbehaving crystals and not about snow that has gotten dirty. No doubt you've seen it, the Christmas card with four-pointed "snow" falling, or the sweater with an… more »

That Snow Joke

November 17th, 2017
A variation on a joke I heard from the UK Laugh Lab, customized for you snow-blog readers: -------------- Sherlock Holmes and Dr Watson go snow camping. After a day snowshoeing around the forest, they return to their camp, have some wine, and crawl into… more »

Grain boundaries between crystals in big ice

November 6th, 2017
Most snow crystals are single crystals. Being single is an outcome of their growth process and small size. On the other hand, most larger ice formations are not single crystals. These latter types are called "polycrystals". A polycrystal usually appears… more »