Clouds Formation

Clouds generally form when rising air is cooled to its dew point, the temperature at which the air becomes saturated. Water vapour normally begins to condense on condensation nuclei such as dust, ice, and salt in order to form clouds. Condensation at surface level results in the formation of fog. If sufficient condensation particles are not present, the air will become supersaturated and the formation of cloud or fog will be inhibited.
There are four main mechanisms for cooling the air to its dew point: adiabatic cooling which tends to produce cloud, and conductive, radiational, and evaporative cooling that can result in the formation of fog. Adiabatic cooling occurs when air rises and expands. The air can rise due to convection, large-scale atmospheric lift along weather fronts and around centres of low pressure, or as a result of being forced over a physical barrier such as a mountain (orographic lift). Conductive cooling occurs when the air comes into contact with a colder surface, usually by being blown from one surface to another, for example from a liquid water surface to colder land. Radiational cooling occurs due to the emission of infrared radiation, either by the air or by the surface underneath. Evaporative cooling occurs when moisture is added to the air through evaporation, which forces the air temperature to cool to its wet-bulb temperature, or until it reaches saturation.
• Adding moisture to the air
The main ways water vapour is added to the air are: wind convergence over water or moist ground into areas of upward motion, precipitation or virga falling from above, daytime heating evaporating water from the surface of oceans, water bodies or wet land, transpiration from plants, and cool or dry air moving over warmer water,