cloud

CLOUD

Cloud is a visible, spatial configuration of water droplets or crystals, floating in the air above the surface of the ground. Their formation process starts when water vaporizes from the Earth surface and moves upwards with the air. Atmospheric pressure decreases with the changing height, forcing the air to expand and cool. Exceeding certain temperature, air saturate and sheds vapour that can no longer be retained. This turns vapour into the small droplets that seat onto the dust or salt particles floating in the air and become a visible cloud.

Clouds form only in the troposphere, part of the atmosphere that is closest to the Earth.

Seen from the distance, they have density and contour that gives them a certain shape. However, when approaching closer, the condensed masses of droplets become more blurry and uneven in transparency, borders are not seen anymore as clear lines but gradually disperse.1

Depending on the height within the troposphere, on which the clouds are formed, we can divide them into three basic groups. Low clouds appear up to the 2 km above the ground level and they are made entirely of water droplets. Middle cloud formations occur between the 2-6 km above the Earth's surface. Within their structure lower parts consist of water droplets and the upper ones of ice crystals. In the highest part of troposphere air is much colder and the clouds are formed entirely out of ice crystals. They reach up to the height of 12 km above the ground level.

Having no mass or substance, clouds float lightly in the air. They have no fixed form so none of the clouds take the same shape. Changes in the flow of air moves them and disperse in different directions, sometimes even combining them with other clouds. They als...

... middle of paper ...

...he ground level. Under certain conditions droplets might combine into a bigger ones, acting differently with the sun rays. Blue and grey colour appear when the water droplets distribute light in all directions within the cloud. Greenish shade is a result of sunlight reflecting from the ice crystals.

Clouds are enormous structures, lighter than the air itself, that have no substance. They float gently in the sky. No resistance to the wind makes them completely dependent on the air movements. Having no define forms and driving forces, they are pushed freely by the wind into all directions, constantly changing their shapes. They appear to our eyes as if they came out of nowhere, when water vapour condense and become visible, gradually gaining density. They can also vanish as quickly as they have appeared, when the weather warms up and turn droplets back to the vapour.