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The Ter River, which flows with very little water in Manlleu (Osona), smokes with the oscillation of temperatures between day and night, as can be seen in these images in La Vanguardia's Readers' Photos.
This smoke escaping from the river generally occurs more in the winter, but this fall the contrast in temperature between night and day is sometimes notable in some areas.
The smoke is due to the presence of very cold air passing over the surface of the water. The phenomenon is known as "arctic smoke."
This smoke is formed as a consequence of the arrangement of air at a very low temperature (cold focus) over a large, less cold water surface (hot focus). It causes moisture to condense only in a narrow layer on the surface of the water.
This curious phenomenon can also be observed in lakes, ponds, reservoirs or even in the sea, especially at dawn, at the transition from night to day.
