How does dew form

Dew forms when a surface cools through loss of infrared radiation down to a temperature which is colder than the dewpoint of the air next to that surface. Dew most often forms on on evenings or nights when there are few clouds, since the greenhouse effect from clouds can keep surfaces from cooling by infrared radiation loss to outer space. Calm winds at night also contribute to dew formation because a windy night keeps the lowest layers of the atmosphere warmer, and also helps evaporate any dew that might begin to form on surfaces.

Dew is made of liquid water that has condensed from some of the water vapor contained in the air. If the layer of air next to the ground also cools to the dewpoint temperature, then fog forms as well.

These water drops are formed by the condensation of the water vapors present in the air. Exactly in the same way when the trees, plants and grass become cold during night, the water vapors of the air condense on them in the form a dew. The dew formation is more when the sky is clear and less when it is cloudy. When the sky is clear and the trees and plants are cooler at nights, there is more evaporation of water and hence more dew formation.

But when it is cloudy, trees and plants do not get cool in the night and hence there is less dew formation. As the sun raises high in the sky, these dew drops evaporate into air. YouSigma - the web's most extensive resource for information. Up to 0.

Whilst small, this amount is significant enough for dew to become an important source of moisture for some plants and animals in arid areas. Dew can be collected for human use from canopies erected above the surface which with the correct conditions can collect several litres of water.

Dew forms most easily on surfaces that do not conduct heat from the ground - grass and the rooftops of cars are some of the most frequently seen examples. It usually forms during the calm weather associated with high-pressure systems. The temperature at which condensation occurs is called the Dew point and is dependent upon the humidity and pressure of the air.

Calculating the exact value of the dew point is important when predicting frost or fog.