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Here is an essay on ‘Precipitation’ for class 6, 7, 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Precipitation’ especially written for school and college students.
Essay on Precipitation
Essay Contents:
- Essay on the Meaning of Precipitation
- Essay on the Weather Systems for Precipitation
- Essay on the Forms of Precipitation
- Essay on the Types of Precipitation
- Essay on the Effect of Precipitation on Agriculture
Essay # 1. Meaning of Precipitation:
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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.
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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.
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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.
Essay # 2. Weather Systems for Precipitation:
For the formation of clouds and subsequent precipitation, it is necessary that moist air masses cool to form condensation. This is normally accomplished by adiabatic cooling of moist air through a process of being lifted to higher altitudes.
Some of the terms and processes connected with the weather systems associated with precipitation are given below:
1. Front:
A front is the interface between two distinct air masses. Under certain favourable conditions when a warm air mass and cold air mass meet, warmer air mass is lifted over colder one with the formation of a front. Ascending warmer air cools adiabatically with consequent formation of clouds and precipitation.
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2. Cyclone:
Cyclone is a large low pressure region with circular wind motion.
Two types of cyclones are recognised:
i. Tropical and
ii. Extra-tropical cyclones.
A tropical cyclone, also called cyclone in India, hurricane in USA and typhoon in Southeast Asia, is a wind system with an intensely strong depression with MSL pressures sometimes below 915 m bars. Normal aerial extent of a cyclone is about 100-200 km in dia. The isobars are closely spaced and winds are anti-clockwise in northern hemisphere.
Center of the storm, called eye, which may extend to about 10-50 km in dia, will be relatively quiet. However, right outside the eye, very strong winds reaching to as much as 200 kmph exist. Wind speed gradually decreases towards outer edge. Pressure also increases outwards. Rainfall will normally be heavy in the entire area occupied by the cyclone.
During summer months, tropical cyclones originate in open ocean at around 5-10° latitude and move at speeds of about 10-30 kmph to higher latitudes in an irregular path. They derive their energy from latent heat of condensation of ocean water vapour and increase in size as they move on oceans.
When they move on land, the source of energy is cut off and the cyclone dissipates its energy very fast. Hence, the intensity of storm decreases rapidly. Tropical cyclones cause heavy damage to life and property on their land path and intense rainfall and heavy floods in streams are its usual consequences. Tropical cyclones give moderate to excessive precipitation over very large areas.
They are cyclones formed in locations outside the tropical zone. Associated with a frontal system, they possess a strong counter-clockwise wind circulation in northern hemisphere. The magnitude of precipitation and wind velocities are relatively lower than those of a tropical cyclone. However, the duration of precipitation is usually longer and the aerial extent also is longer.
3. Anticyclones:
These are regions of high pressure, usually of large aerial extent. Weather is usually calm at the center. Anticyclones cause clockwise wind circulations in northern hemisphere. Winds are of moderate speed and at the outer edges, cloudy and precipitation conditions exist.
Differences between cyclone and anticyclone are:
Essay # 3. Forms of Precipitation:
Condensation forms of fog, dew and frost are not considered to be precipitation. The common precipitation forms are rain, drizzle, snow, sleet and hail (Table 2.5). Of these, drizzle and light snow are the only forms likely to fall from clouds having little or no vertical development. Fog results when atmospheric water vapour condenses to water droplets or ice crystals, become visible and have their base in contact with ground.
Essay # 4. Types of Precipitation:
There are three main types of rainfall (precipitation):
1. Convectional Rainfall:
Rainfall results when a heated air expands, rises and condenses to form drops of rain. Convectional rainfall is more common in humid tropical regions that receive much of sun’s energy. It, usually, occurs in the afternoons after surface air has been heated.
2. Orographic (Relief) Rainfall:
Rainfall results from uplift of air above some highland. Mountain ranges force air blowing over them to rise, cool and then condense to fall as rain. Side of the mountain that faces the wind and receives rainfall is the windward side. The opposite side that receives dry winds is the leeward side.
3. Frontal (Cyclonic) Rainfall:
This type of rainfall occurs along the zone of contact between a warm and cool air mass. When two large air masses of different temperature meet, the warmer and hence lighter air is lifted above the cooler air. Warm air then rises, cools and condenses to form rain. The boundary that separates cold air and warm air is called a front.
Essay # 5. Effect of Precipitation on Agriculture:
Precipitation, especially rain, has a dramatic effect on agriculture. All plants need at least some water to survive, therefore rain (being the most effective means of watering) is important to agriculture.
While a regular rain pattern is usually vital to healthy crops, too much or too little rainfall can be harmful, even devastating to crops. Drought can kill crops and increase erosion, while overly wet weather can cause harmful fungus growth. Plants need varying amounts of rainfall to survive.
In areas with wet and dry seasons, soil nutrients diminish and erosion increases during wet season. Animals have adaptation and survival strategies for wetter regime. Previous dry season leads to food shortages into the wet season, as the crops have yet to mature.
Rainfall and its influence on crop production can be summarised as indicated below:
1. Rainfall pattern determines cropping systems.
2. Decisions on preparatory tillage, time of sowing, scheduling of irrigation, plant protection, time of harvesting etc. depends on rainfall.
3. Rain analysis is necessary for designing farm ponds, tanks and irrigation projects.
4. Amount, distribution and intensity of rainfall dictate crop productivity.
5. High intensity rains leads to floods and soil erosion.
6. Deficit and untimely rains leads to drought.
7. Food-grain production and fodder needs of a country (adequacy, surplus or deficit) depend on timely rainfall during crop growing season.