Question

I want a paragraph of precipitation and rainfall​

Answer 1

Explanation:

Precipitation is water released from clouds in the form of rain, freezing rain, sleet, snow, or hail. It is the primary connection in the water cycle that provides for the delivery of atmospheric water to the Earth. Most precipitation falls as rain.

Answer 2

Answer:

Precipitation - Precipitation occurs when tiny droplets of water, ice or frozen water vapor join together into masses too big to be held above the earth. They then fall to ground as precipitation.

The term precipitation denotes all forms of water that reach the earth from the atmosphere. Usual forms are rainfall, snowfall, hail, frost and dew. Of all these, only the first two contribute significant amounts of water. Magnitude of precipitation varies with time and space.

For precipitation to form:

1. The atmosphere must have moisture.

2. There must be sufficient nuclei present to aid condensation.

3. Weather conditions must be good for condensation of water vapour to take place.

4. The products of condensation must reach the earth.

Precipitation is water in liquid or solid forms, falling to the earth. It always precedes condensation or sublimation or a combination of the two and is primarily associated with raising air. In the same way that isotherms and isobars are used to show temperature and pressure distribution respectively, isohyets indicate rainfall distribution. An isohyet is a line connecting points with equal values of rainfall.

Change of state from water vapour to liquid water is condensation. When moist air comes in contact with cool surfaces, it may be cooled to the point where its capacity to hold water vapour is exceeded by the actual amount in the air. Part of the water vapour then condenses into liquid form on the cool surface, produce dew.

When this happens, the latent heat of vaporisation, in this process, called the latent heat of condensation is released. At temperatures below freezing, water may bypass the liquid form in its change of state. When dry air with a temperature well below freezing comes in contact with ice, molecules of ice (H2O) pass directly into the vapour state by the processes of sublimation.

Under proper weather conditions, water vapour condenses over nuclei to form tiny water droplets of sizes less than 0.1 mm in dia. The nuclei are usually salt particles or products of combustion and are normally available in plenty.

Wind speed facilitates movement of clouds while its turbulence retains water droplets in suspension. Precipitation results when water droplets come together and coalesce to form larger drops that can drop down. Considerable part of this precipitation gets evaporated back to the atmosphere.

Rainfall- The presence of warm, moist and unstable air and sufficient number of hygroscopic nuclei are pre­requisite conditions for rainfall. The warm and moist air after being lifted upward becomes saturated and clouds are formed after condensation of water vapour around hygroscopic nuclei (salt and dust particles) but still there may not be rainfall unless the air is supersatu­rated.

The process of condensation begins only when the relative humidity of ascending air becomes 100 per cent and air is further cooled through dry adiabatic lapse rate but first condensation occurs around larger hygroscopic nuclei only. Such droplets are called cloud droplets.

The aggregation of large number of cloud droplets forms clouds. These cloud droplets are so microscopic in size that they remain suspended in the air. Rainfall does not occur unless these cloud droplets become so large due to coalescence that the air be­comes unable to hold them.

This is why, sometimes the sky is overcast by thick clouds but there is no rainfall. If by chance these cloud droplets fall downward they are evaporated before they reach the ground surface. Rainfall occurs only when cloud droplets change to raindrops.

There are two possible processes of change of cloud droplets into raindrops:

(1) If warm and moist air ascends to such a height that condensation begins below freezing point, then both, water droplets and ice droplets, are formed. The water droplets are evaporated because of differ­ence of vapour pressure between them and ice droplets and there is condensation of evaporated water around ice crystals which go on increasing in size. If they become sufficiently large in size, they cannot be held in suspension by the air and consequently they begin to fall down. If the temperature above the ground is high they fall in the form of raindrops.

(2) The suspended cloud droplets in the clouds are of different sizes. These cloud droplets collide among themselves at varying rates due to difference in their sizes and thus form large droplets. In the process several cloud droplets are coalesced to form raindrops. When they become so large in size that ascending air becomes unable to hold them, they fall down as rain­fall.

The diameter of a raindrop is upto 5mm and one raindrop contains about 8,000,000 cloud droplets. Rain drops fall down at the velocity 200 times greater than cloud droplets. When raindrops become very large and fall down at greater speed (more than 30 kilometres per hour), they are split in the transit but give heavy downpour.

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