A rare form of snow which is induced by electricity generation stations fell Friday in areas near the German city of Essen, DPA reported. Meteorologists assured worried residents that the 5 to 8 centimetres of snow that fell in gardens and on streets was harmless and consisted of nothing else but water. A temperature inversion, in which cold air is trapped near the ground by a layer of warmer air, was accompanied by deep fog. The plumes of vapour rising from the cooling towers caused water droplets to precipitate as very fine snow. The German Weather Service in Essen said the snow fell in the cities of Herne, Dortmund and Bochum after ground temperatures fell overnight to minus six Celsius. The artificial snow melted in the course of the day. The service said the phenomenon was last seen in the area two years ago. The snow formed 300 to 400 metres above the ground. Coal-fired and nuclear power stations use steam to drive turbines. The waste heat from the steam is released through the chimney-like cooling towers.
