Formation of Clouds

What is Cloud?

• Clouds are created when water vapor, condenses and turns into liquid water droplets. These water droplets form on tiny particles, like dust, ice crystals, or altogether that are floating in the air, become visible as Cloud.

Clouds are formed in 4 main ways:

1. Turbulence
2. Orographic lifting
3. Convection
4. Frontal lifting

Clouds formed by Turbulence:

• Strong winds blowing over uneven ground strike against the various obstructions and the air gets deflected upwards.
• This causes thorough mixing of the air and, as the air rises, and cools adiabatically below its dew point, clouds will form. 
• These clouds will be of an even, layer type (stratus) and their bases will generally be not more than 600m high. 
• Turbulence clouds will be formed in great quantities if the air is moisture-laden and blows over cold, uneven ground. 
• Over the sea, wind speeds of more than 13 knots only (force 4 and over) can produce sea waves of sufficient height to create turbulence clouds.

Clouds formed by Orographic lifting:

• Orographic lifting occurs when a mountain acts as a barrier to the wind. 
• During the air ascends a mountain slope, adiabatic cools below its dew point and forms an orographic cloud.
• These are stratus type. 
• If the mountain is quite high, the further ascent will result in nimbostratus and continuous precipitation.
• Precipitation on the windward side while on the leeward side the air is much drier.
• Leeward side, while descending air warms adiabatically.
• This is called Banner cloud.

Clouds formed by Convection:

• Convectional uplift happens when the surface of the air is heated at the ground and expands.
• Then the air should be less dense than the surrounding air.
• After that, the less dense air will begin to rise and cools adiabatically below its dew point.
• When this is successful, convection cloud forms, due to saturation.
• The greater the ascent of air, the greater the vertical extent of the cloud resulting in the vertical extent of the towering cumulus.
• If ascends rapidly(fast) vertical extent reaches the tropopause and spreads sideways and resembles an anvil-shaped cloud called cumulonimbus.

Clouds formed by Frontal lifting:

• Usually, the two masses (warm and cold) of air are opposite temperatures and moistness.
• One air mass is hot and moist while the other air mass is cool and dry.
• The boundary between them is not vertically.
• Then the cool air mass would act as a sloped surface and the warm air mass would use the surface to rise.
• The warm air mass rises and cools adiabatically and cools below its dew point.
• In case of warm front: Slope is gradual and up sliding warm air forms stratiform clouds - nimbostratus, altostratus, cirrostratus and finally cirrus.
• In case of cold front: The slope is very steep and up sliding warm air forms cumulonimbus and cumulus clouds.