The pimple powder
The name comes from its characteristic surface structure: the loose, usually very cold powder snow is covered with pimples and/or waves. These are created by constant, weak winds. These are very, very slightly above the load-bearing capacity and therefore only transport small amounts of snow crystals. This results in the pattern on the surface of nap powder. Loose, light (= low density snow) powder snow - crystal forms: Fresh snow, felt or small, angular forms - is therefore transported in small quantities, but remains loose and unbound. The influence of the wind is too small to form drifting snow. This type of snow is usually found in higher, shady cirques. Pimple powder is particularly suitable for skiing, as it is often weakly built up, meaning the snow is looser and feels soft and airy on the descent.
Catabatic downslope winds are usually the cause of pimple powder. This type of wind can be conceptually categorized as the opposite of "thermals". Air parcels that cool down at higher altitudes (shady cirques and mountain basins or glacier surfaces) and flow towards the valley due to the increase in density and the resulting pressure gradient. In the height of winter, pimple powder is encountered to a far greater extent than in spring: the low sun only reaches a few areas of the terrain in December, January and February. This means that the air can cool down in much larger areas and subsequently sink. In spring, pimple powder is then usually only found on higher, very steep shady slopes.
