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 inhomogeneity 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 inhomogeneity: A building, a hill, a forest belt, a sharp temperature gradient on 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. Snow acts as an ideal visualizer of these invisible air currents in this case. Light snowflakes, especially in the form of dendrites (stars), have a large sail area and follow the slightest movements of 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. They form 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, creatin ... Read more