Steam
Steam plumes are a mixture of air , water vapor and the finest drops of water . Depending on the temperature and humidity of the surrounding air, they are created via cooling towers and cooling ponds through condensation . Colloquially, the plumes are often equated with water vapor. The plumes of steam over the cooling towers of a large power plant can have a significant impact on the microclimate in the immediate vicinity, for example by reducing the amount of solar radiation due to shading . Steam plumes can also significantly increase the amount of precipitation locally due to the water carried in .
In a car that is started in a cold environment, you can also see clouds of steam: After starting the exhaust system is still cool. The exiting exhaust gas has a temperature below 100 ° C , as a result of which parts of the water vapor (created when the hydrocarbons contained in the fuel are burned ) condense from the exhaust gas and become visible as water droplets. At higher temperatures, the exhaust gas is so hot that the water vapor it contains cannot condense as quickly. As a result, the exhaust gas is further dispersed and thus invisible - the water vapor saturation concentration is not exceeded.
In damp and / or cold weather, the water in the vapor plumes is not absorbed by the air, the saturation vapor pressure is reached sooner. In winter this is often misinterpreted as a higher exhaust gas pollution.
Something similar occurs, for example, when exhaling the moist air you breathe in a cool or damp environment. The reason for this is the previously existing high relative humidity of the air and the fact that the saturation concentration or the saturation vapor pressure of the water is lower at low temperatures.