Clouds and Precipitation

Clouds and Precipitation

Clouds are formed when water vapour in the air get condensed to form a mass of tiny ice crystals or small water droplets. When the air at the given temperature is not capable of holding moisture anymore, and the temperature at which saturation occurs in air is known as dew point. 

Increase in temperature increases water absorption and retention capacity of the given parcel of air. The transformation of water vapour into water is called condensation. After condensation the water vapor takes one of the following forms, i.e. dew, frost, fog or clouds.

Clouds

• Clouds come in a variety of shapes because they form at varying heights above the earth’s surface
• Based on their height, expanse, density, transparency or opaqueness, clouds are classified into following categories
• Cirrus: a type of cloud that forms at high altitudes (8,000 – 12,000m), they are thin and detached, have a feathery appearance and are always white
• Cumulus: it has a cotton wool appearance and forms at a height of 4,000 to 7,000 metres patches can be found scattered here and there and their base is flat
• Stratus: these layered clouds cover a large portion of the sky and are formed as a result of heat loss or the mixing of different temperature masses of air
• Nimbus: they are either black or dark gray in colour and are formed at mid-levels or extremely close to the earth’s surface
• Combination of these four types can give rise to the high clouds which are termed as cirrus, cirrostratus, cirrocumulus; middle clouds known as altostratus and altocumulus; and low clouds are known as stratocumulus and nimbostratus
• Clouds with extensive vertical development are called cumulus and cumulonimbus

Precipitation: 

• Precipitation is the moisture that forms as a result of the condensation of water vapour

• Continuous condensation process in free air produces large-sized condensed particles

• When air resistance fails to hold these condensed particles against the force of gravity, they fall to the earth’s surface.

• It can take the form of a liquid or a solid

• Rainfall is defined as water-based precipitation

• Snowfall occurs when the temperature falls below 0°C and precipitation falls in the form of fine flakes of snow

• Sleet is made up of frozen raindrops and refrozen melted snow

• Sleet falls when the temperature rises above freezing and an air layer overlies a sub freezing layer near the ground

Hailstones

• Drops of rain after released by the clouds become solidified into small rounded solid pieces of ice and which reach the surface of the earth in form of hailstones
• Formed by the rainwater passing through the colder layers

Types of rainfall

• rainfall may be classified into the convectional, orographic or relief and the cyclonic or frontal rainfall
• Convectional rain: when with thunder and lightning, heavy rainfall takes place but does not last long
  • common during the summer or in the hotter part of the day
  • common in the equatorial regions and interior parts of the continents, mainly in the northern hemisphere

• Orographic rain: when the saturated air mass comes across a mountain and is forced to ascend, the temperature falls and the moisture is condensed
  • windward slopes receive greater rainfall
  • It is also known as the relief rain

• Cyclonic rain:  
  • cyclones are violent storms that originate over oceans in tropical areas and move over to the coastal areas bringing about large scale destruction caused by violent winds, very heavy rainfall and storm surges
  • This is one of the most devastating natural calamities

Thunderstorms and Tornadoes

• Thunderstorms are caused by intense convection on moist hot days
• A thunderstorm is a well-grown cumulonimbus cloud producing thunder and lightning
• From severe thunderstorms sometimes spiralling wind descends like a trunk of an elephant with great force, with very low pressure at the centre, causing massive destruction on its way, and such a phenomenon is called a tornado
• The violent storms are the manifestation of the atmosphere’s adjustments to varying energy distribution
• The potential and heat energies are converted into kinetic energy in these storms and the restless atmosphere again returns to its stable state

Conclusion

 The air contains water vapours and it varies from zero to four per cent by volume of the atmosphere and plays an important role in weather phenomena.The amount of water vapours in the atmosphere is present or absent due to evaporation and condensation respectively. Precipitation is the moisture that forms as a result of the condensation of water vapour while thunderstorms are caused by intense convection on moist hot days. Convectional, orographic and cyclonic are some of the types of rainfall.