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Here is an essay on ‘Monsoons’ for class 6, 7, 8, 9 and 10. Find paragraphs, long and short essays on ‘Monsoons’ especially written for school students.
Essay on Monsoons
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Essay Contents:
- Essay on the Introduction to Monsoons
- Essay on the Significant Features of Monsoon
- Essay on the Southwest Monsoon
- Essay on the Northeast Monsoon
- Essay on the Failure of Monsoons
Essay # 1. Introduction to Monsoons:
India’s climate is dominated by monsoons. Monsoons are strong, often violent winds that change direction with the season. Monsoon winds blow from cold to warm regions because cold air takes up more space than warm air. Monsoons blow from land toward sea in winter and from sea toward land in summer.
India’s winters are hot and dry. Monsoon winds blow from northeast and carry little moisture. Temperature is high because the Himalayas form a barrier that prevents cold air from passing onto the subcontinent.
Summer monsoons roar onto the subcontinent from southwest. The winds carry moisture from Indian Ocean and bring heavy rains from June to September. The torrential rainstorms often cause violent landslides. Despite the potential for destruction, summer monsoons are welcomed in India.
Monsoons may be considered as large scale sea breezes, due to seasonal heating and the resulting development of a thermal low over a continental landmass. Air over land warms faster and reaches a higher temperature than air over ocean. Hot air over land tends to rise, creating an area of low pressure. This creates a steady wind blowing toward land, bringing moist near- surface air over oceans with it.
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Similar rainfall is caused by moist ocean air being lifted upwards by mountains, surface heating, convergence at the surface, divergence aloft or from storm- produced outflows at the surface. However, as lifting occurs, air cools due to expansion in lower pressure, which in turn produces condensation.
In winter, land cools off quickly, but ocean retains heat longer. Cold air over land creates a high pressure area which produces a breeze from land to ocean. Monsoons are similar to sea and land breezes, a term usually referring to localised, diurnal (daily) cycle of circulation near coastlines, but they are much larger in scale, stronger and seasonal.
Essay # 2. Significant Features of Monsoon:
Four significant features of monsoon are:
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a. Date of onset.
b. Periods of active monsoon.
c. Breaks in monsoon.
d. Date of withdrawal.
a. Onset of Monsoon:
Monsoon rainy season begins earliest in south China towards early May. Over the Indian main continent, the monsoon sets either by the end of May or early-June along Malabar Coast (over Andaman and Nicobar islands it sets in by mid-May). Normal monsoon onset date over India is first June.
The onset is associated with heavy rains over Kerala and coastal Karnataka. It then spreads to Peninsular region and slowly to southwestern and southeastern parts of India by 10 June. Monsoon onset over rest of the central and northwest India is gradual and enters western Rajasthan by first July and Kashmir by 15 July.
Though the data of onset of monsoon is quite regular occurring around first June, there are occasions when not only the onset over Kerala coast is delayed but also the movement of monsoon across the country is sluggish. Under such weak monsoon conditions, delay in onset may be of few days or more than a week over Kerala while its delay may be around a month over arid parts of western Rajasthan.
b. Periods of Active Monsoon:
The monsoon current is pulsatory in nature and advance into different areas in two or three stages. In the first stage, rains cover west coast up to Konkan and Peninsular India and northeast region. This stage is accomplished in about 10 days after the onset of monsoon over Kerala coast.
However, if the monsoon current is weak, this movement is slowed down or initiates late as a result of which the onset over peninsular region can be delayed by a few days. The second stage usually follows after a gap of 7 days with rains advancing into Gangetic valley up to Uttar Pradesh and into Gujarat.
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Again after a gap of about 7 days, rains further advance westwards and northwards. By the time the entire country is covered, the monsoon trough takes its normal position, with the trough extending from Ganganagar region in Rajasthan to northern part of Bay of Bengal. The active monsoon period is only from July to September. However, cyclonic- storms are frequent from October to December.
c. Break Monsoon Conditions:
Break conditions prevail in monsoon rainfall when the monsoon trough moves northwards to the foothills of Himalayas. During such periods, rainfall is limited to northeastern region of Assam and adjoining regions, while the rest of the country goes dry. Even in such occasions, some rainfall is recorded along west coast under the influence of waves in the easterlies at mid-level.
The northeast monsoon provides rainfall mainly to Peninsular India during October-December. Most of Tamil Nadu shielded by Western Ghats from southwest monsoon rains depends on northeast monsoon rains for its agriculture. There is no clear-cut distinction between withdrawal of southwest monsoon and onset of northeast monsoon.
d. Withdrawal of Monsoon:
Monsoon begins to withdraw from extreme arid areas of western Rajasthan by first September and in general, from northern India around mid-September. Withdrawal phase extends rapidly over western India up to west Uttar Pradesh, west Madhya Pradesh and Gujarat by first October.
Withdrawal phase is slow to the east of 80°E over Gangetic valley, northeastern India, eastern Madhya Pradesh, Vidharbha and adjoining Maharashtra and interior Peninsular India. By the end of October, it withdraws to south of 15°N. The northeast monsoon becomes active over peninsular region by October and northeast monsoon rains merge with withdrawal of southwest monsoon along coastal Andhra Pradesh.
During October-November, occasional low pressure systems form in the Bay of Bengal and at times intensify into cyclonic storms and lash coastal regions of Andhra Pradesh and Tamil Nadu. The monsoon finally withdraws from Indian Peninsula by 15 December. Thus, the total duration of monsoon activity across the country varies from 122 days over Kerala coast, while over extreme parts of western Rajasthan, the duration is as low as 45 days.
Essay # 3. Southwest Monsoon:
Southwest monsoon occur from June through September. Thar Desert and adjoining areas of northern and central Indian subcontinent heats up considerably during hot summer. This causes a low pressure area over northern and central Indian subcontinent. To fill this void, moisture laden winds from Indian Ocean rush in to the subcontinent.
These winds, rich in moisture, are drawn towards Himalayas, creating winds blowing storm clouds towards the subcontinent. Himalayas act like a high wall, blocking the winds from passing into Central Asia, thus forcing them to rise. With the gain in altitude of the clouds, temperature drops and precipitation occurs. Some areas of the subcontinent receive up to 10.000 mm (390 in) of rain (Fig. 2.10).
Southwest monsoon is, generally, expected to begin around start of June and fade down by the end of September or mid-October. Moisture laden winds on reaching southernmost point of Indian Peninsula, due to its topology, become divided into two parts- the Arabian Sea Branch and the Bay of Bengal Branch.
Arabian Sea Branch of southwest monsoon first hits the Western Ghats of coastal state of Kerala, India, thus making it as the first state in India to receive rain from southwest monsoon. This branch of monsoon moves northwards along Western Ghats with precipitation on coastal areas, west of Western Ghats. Eastern areas of Western Ghats do not receive much rain from this monsoon as the wind does not cross Western Ghats.
Bay of Bengal Branch of southwest monsoon flows over Bay of Bengal heading towards northeast India and Bengal, picking up more moisture from Bay of Bengal. Winds arrive at Eastern Himalayas with large amounts of rain. Mawsynram, situated on southern slopes of Eastern Himalayas in Shillong, India, is one of the wettest places on the earth.
After arrival at Eastern Himalayas, the winds turns towards west, travelling over Indo-Gangetic plain at a rate of roughly 1-2 weeks per state, pouring rain all along its way. June 1 is regarded as the date of onset of monsoon in India, as indicated by the arrival of monsoon in southernmost state of Kerala.
Monsoon accounts for 80 per cent of rainfall in India. Indian agriculture is heavily dependent on rains, for growing crops especially like cotton, rice, oilseeds and coarse grains. A delay by a few days in the arrival of the monsoon can badly affect the economy, as evidenced in the numerous droughts in India in 1990s.
Essay # 4. Northeast Monsoon:
Around September, with the sun fast retreating south, northern land mass of Indian subcontinent begins to cool off rapidly. With this air pressure begins to build over northern India, Indian Ocean and its surrounding atmosphere still holds its heat.
This causes the cold wind to sweep down from Himalayas and Indo-Gangetic plain towards vast spans of Indian Ocean south of Deccan Peninsula. This is known as northeast monsoon or retreating monsoon (Fig. 2.10).
While travelling towards Indian Ocean, the dry cold wind picks up some moisture from Bay of Bengal and pours it over Peninsular India and parts of Sri Lanka. Cities like Madras (Chennai), which gets less rain from southwest monsoon, receives rain from this monsoon. About 50 to 60 per cent of the rain received by the state of Tamil Nadu is from northeast monsoon.
In southern Asia, northeastern monsoons take place from December to early March when the surface high pressure system is strongest. The jet stream in this region splits into southern subtropical jet and polar jet.
The subtropical flow directs northeasterly winds to blow across southern Asia, creating dry air streams which produce clear skies over India. Meanwhile, a low pressure system develops over Southeast Asia and Australasia and winds are directed toward Australia known as a monsoon trough.
Essay # 5. Failure of Monsoons:
Weather is the chance element in field crop production that can bring about crop failure in spite of providing all other necessary inputs. In some years, monsoons fail and dramatically impact agricultural production.
Failure of monsoon is attributed to several natural and human induced climatic factors of which the following are the possible ones:
1. El-Nino effect.
2. Southern Oscillation Index (SOI).
3. Past history of monsoon.
4. Carbon dioxide concentration in the atmosphere.
5. Deforestation.
6. Thinning of ozone layer.
El-Nino is a narrow current of warm water that appears off the coast of Peru in December. In some years, this warm current becomes more intense than usual. Southern oscillation is the see-saw pattern of meteorological changes that are often observed between the Pacific and the Indian oceans. When the surface pressure is high over the Pacific, pressure over the Indian Ocean tends to be low and vice-versa.
Southern oscillation, however, has fixed periodicity. Its spread varies from 2 to 5 years. Its different phases of oscillation can be observed through changes in pressure over the Pacific and the Indian oceans.
The difference of pressure between Tahiti (in French Polynesia representing the Pacific) and Port Darwin (in northern Australia representing the Indian Ocean) is called the Southern Oscillation Index (SOI). Negative value (-ve) of the index (Tahiti-Port Darwin) is the precursor of poor or deficient monsoon in India.
Circulation of air over tropics is dominated by Hadley cell (N-S direction) and Walker cell (E-W direction). Interaction of these two cells causes variation in descending and ascending nature of air over the tropics.
There exist three major regions of rising motion in these tropics:
1. Indonesia, Southeast Asia, and Western Pacific.
2. Tropical South America (Equador and Peru).
3. Congo basin of Africa.
These are the regions of high cloud cover, high rainfall and temperature. Disruption in these areas causes abnormality in the usual monsoon pattern.
Due to EL-Nino abnormality, the descending limb of the Walker cell moves eastward. Large area over India becomes a zone of descent rather than ascent and results in drought.
The sequences leading to drought to deficient rain are:
1. Negative SOI.
2. High pressure over Indian Ocean and low pressure over Pacific Ocean.
3. Descending instead of ascending motion over Indian Ocean and Southeast Asia and ascending motion instead of descending over eastern Pacific (Peru and Equador).
4. El-Nino abnormality.
These suggest a close association between southern oscillation and El-Nino. A negative value of SOI and El-Nino favours a year of deficient rainfall. However, this is also not correct always.