Non-adiabatic cooling

Non-adiabatic cooling
Along with adiabatic cooling that requires a lifting agent, three major nonadiabatic mechanisms exist for lowering the temperature of the air to its dew point. Conductive, radiational, and evaporative cooling require no lifting mechanism and can cause condensation at surface level resulting in the formation of fog.[22][23][24]

Adding moisture to the air
Several main sources of water vapor can be added to the air as a way of achieving saturation without any cooling process: evaporation from surface water or moist ground,[25][26][27] precipitation or virga,[28] and transpiration from plants.[29]

Classification: How clouds are identified in the troposphere
For a comprehensive listing of over 90 combinations of genera divided into species and subdivided into varieties with Latin etymologies, see List of cloud types.

Low stratus fractus partly obscuring nimbostratus over Deccan Plateau, India
Tropospheric classification is based on a hierarchy of categories with physical forms and altitude levels at the top.[3][4] These are cross-classified into a total of ten genus types, most of which can be divided into species and further subdivided into varieties which are at the bottom of the hierarchy.[30]

Physical forms

Cirrus fibratus clouds in March
Clouds in the troposphere assume five physical forms based on structure and process of formation. These forms are commonly used for the purpose of satellite analysis.[3] They are given below in approximate ascending order of instability or convective activity.[31]