Snow Circulation: Physics, Meteorology, and the Poetics of Vortices Snow circulation is not just chaotic movement of snowflakes in the wind, but a complex physical phenomenon arising from the interaction of air currents with obstacles, terrain, and thermal heterogeneity of the surface. These vortices, from small "snow devils" to massive blizzards, follow the laws of hydrodynamics, thermodynamics, and crystallography, representing miniature atmospheric models of turbulence. 1. Physical Foundations of Snow Vortex Formation The key principle is turbulence, that is, disordered, vortex movement of air. For the occurrence of rotation, the following are required: Wind speed shear: Difference in wind speed at different heights or between adjacent air masses. This creates a rotational moment. Obstacle or heterogeneity: Building, hill, forest belt, sharp temperature gradient of the surface (for example, warm asphalt against a snowy field). As the air flows around the obstacle, it forms Karman vortex streets — chains of alternating vortices. Convection: Heated surface by the sun (even dark asphalt can be warmer than snow in winter) creates ascending currents. When they meet horizontal wind, they twist, forming convective vortices. In this case, snow acts as an ideal visualizer of these invisible air currents. Light snowflakes, especially in the shape of dendrites (stars), have a large sail area and follow the slightest movements of the air, making the structure of turbulence visible to the naked eye. 2. Typology of Snow Circulations 1. Ground snow vortices ("snow devils"): Small-scale (from 0.5 to 5 meters in diameter), short-lived (seconds to minutes) vortices similar to dust devils. Formed under conditions: Strong wind speed shear at the surface. Intense sunlight, creating local heating and convection. Relatively weak background wind. Example: Characteristic swirling over a cleared path on the background of drifts. The dark surface of the path heats up stronger, creating an ... Read more