INDIA'S Monsoon
Introduction
This is Project Report/Essay on Monsoon of India - Our country is a land of
great diversity in climate. There are wide seasonal variations as well as
variations between day and night. These variations are observed in
temperature. A word of monsoon use derived from the Arabic word 'mousam'
which means season.
There are four season of Monsoon in India
The zone of high temperature shift north words owing to the apparent north word movement of sun. Minimum temperature exceeds 400C over most part of North India during May. During the cold weather season. Low temperature conditions brevaid in the Northern plains. This result in the formation of a high pressure in the northern plains. Cold and dry winds blow out from this high pressure. North east trade winds prevail over the Bay of Bengal and the peninsula most parts of India have fine weather with clear skies. Parts of North-West. India are affected by western disturbances which originate in the medi terranesn sea. These disturbances give rainfall and snow fall to parts of Jammu and Kashmir, Punjab, Himachal Pradesh and Haryana parts of Tamil Nadu cost also get rain fall from north east winds blowing over the Bay of Bengal.
Advancing Monsoon season is a blessing if it rains in time. It gives peace and pleasure to all. Monsoon season in summer gives us great relief. It lessens the heat the temperature comes down. The air becomes cool. Men, animals and birds all feel refreshed. The leaves of trees have a glistening shire. The gardens look charming. Monsoons season in winter is dreaded by all. Then we are remained of saying. 'Lay by something for a rainy days. Except for ultimately or excessive rains a monsoon season in India are greeted Is equally useful to animal and plant life. It is important to men life also.
Monsoon in India
The four months namely June, July, August, September form the core of the rainy season almost all over India. This duration of the rainy season. However goes on decreasing from south to north and from east to west. In the extreme north west it is barely two months. Between three-fourths and nine-tenths of the total rain fall is concentrated over his period. This may gives us an idea of how unevenly it is distributed over the year. The low pressure conditions over the north - western plains get further intensified By early June they are powerful enough to attract the trade winds of southern Hemisphere. These south-east trade winds are of oceanic origin coming from the Indian ocean they cross the equator and enter the Bay of Bengal and the Arabian sea, only to be caught up in the air circulation over India. Passing over the equatorial worth currents they bring with them moisture in abundance. After crossing the equator they follow a south - westerly direction. This is why they are known as south west monsoon. Thus the north east-trades of winter, originating on the land are replaced by diametrically opposite south west monsoons laden with a moisture. The monsoon unlike the trades are not steady winds. They are essentially pulsating in nature. The rain bearing winds are strong. They blow at an average speed of 30 KM per hour barring the extreme north west they over run the country in a month's time the sudden approach of the moisture - laden winds is associated with violent thunder the lighting. This us known as 'break' or 'burst' of the monsoon. It is of interest to note that these monsoon winds follows a south-westerly direction. But as they approach the land their direction is modified by the relief and thermal low pressure over north-west India. To begin with, the Indian peninsula divides the monsoon into two braches. They are the Arabian sea branch and the Bay of Bengal branch. The Arabian sea branch of the monsoon is obstructed by the western glades. The wind are side of the sahyadris receive very heavy rains. Crossing the ghats they overrun the ocean bateau and Madhya Pradesh causing fair amount of rainfall. Thereafter they enter the Ganga-plains and mingle with the Bay of Bengal branch. Another part of the Arabian sea branch strikes the saurashtra peninsula and the kachchh. It then passes over west Rajasthan and along the Araballis, causing only a scanty rainfall. In Punjab and Haryana, it too joins the Bay of Bengal branch. These two branches. The Bay of Bengal branch is naturally directed towards the coast of myaninsar and part of south-east Bangladesh. But the Arabian Hills along the coast of Myamar are good enough to defect a big chunk of this branch, enabling it to enter the Indian subcontinent. The monsoon, there fore enter west Bengal and Bangladesh from south and south east instead of the south westerly direction. There after this branch splits into two under the influence of the one branch moves west ward along the Ganga plains reaching as far as the Punjab plains. The other branch moves up the Brahmaputra vally in the north and north east coursing widespread rains in the North eastern India. Its sub-branch strikes the Garoand Khasi Hills of Meghalaya Mawsyntain located on the crest of the sough tern range of khasi Hills, receives the highest average annual rainfall in the world. Cherapunji, located 16 km east of Mawsynrain holds some other rainfall records. Distribution of rainfall received from south west monsoon is very largely governed by the relief or orography for instance, the wind ward side of the Western Ghats registers a rainfall of over 250 centimeters. On the other hand the leeward side of these ghats is hardly able to receive 50 cm. Again the heavy rainfall in the north eastern states can be attributed to their hilly ranges and the eastern Himalayas. The rainfall in the northern plains goes on decreasing from east to west During this particular season Calcutta receive about 120 cm, Patna 102 cm, Allahabad 91 cm and Delhi 56 cm.
Forms of Precipitation
Common forms of precipitation are rainfall, drizzle, snow fall, sleet, and hail.
(1) Rainfall - This is the most common form of precipitation. It consists of water falling in drops from the clouds. The size of rain-drops varies from 0-5 mm to 6 mm in diameter. The ascent of large masses of air is essential for rainfall to occur. The ascent may be brought about in three ways. corresponding to these there are three main types of rainfall : Convectional, cyclonic and orographic.
(a) Convectional rainfall :- Convectional rainfall is caused by the process of convection in the atmosphere the sun reads the earth’s surface which, in turn heats air near the ground. The warm cur rises in fast convection currents. The rising air is cooled till it's dew point is reached now the water vapor condenser I clouds form, and rainfall occurs. Convectional rainfall is common in equations region. It occurs as heavy downpour, often accompanied by thunder.
Cyclonic rainfall :- This type of rainfall is also called frontal rainfall. It is associated with the passage of a cyclone. It occurs when a warm air mass overrides a damson mass of cold air along a front condensation takes place, with cloud formation and rainfall ahead of the front.
Orographic rainfall :- This type of rainfall is caused by mountains standing in the path of moisture- laden air the air is forced to rise and is thereby cooled. Clouds form and rain fall on the wind ward slaps of the mountain. The air is almost free of moisture when it descends over the other side of the mountain. This side, called the leeward slope, receives relatively light rain, or no rain. It is, therefore, an area of dry climate and is often called a rain shadow area.
(2) Drizzle :- Rainfall in fine raindrops of less than 0-5 mm diameter is called drizzle. The fine droplets of drizzle appear to float following the lightest movement of air. The Drizzle falls continuously from law, thin - layered clouds. It is often associated with fog and poor visibility.
(3) Sleet :- Rain that is Frozen or partially frozen is called sleet. It is produced when rainfalls through a cold layer of air near the earth's surface.
(4) Snowfall :- Precipitation in the form of minute ice crystals is called snowfall. It occurs when water vapor condenses at temperatures below 00C. and the lower atmosphere is sufficiently cool. These conditions are essential for ice crystals to reach the ground without melting. Snowfall is common in middle and high latitude.
(5) Hail :- The roundest pellets of ice that fall from esdense cumulus clouds of immense vertical height are called hail or hailstones. Hailstones range from 5 mm to 5 cm in diameter. These are formed when there are strong vertical currents of air. Condensation then occurs at very high altitudes at very low temperatures. The pellets of ice formed within the clouds repeatedly rise and fail with draughts. They keep colliding with super cooled water droplets which instantly freeze on them. They grow larger and heavier by deposition of ice layers. Where as they are too heavy to be sustained by an up draught, they fall to the ground. The internet structure of hail reveals several concentric layers of clear ice alternating with milky layers of ice.
Regional distribution of Monsoon in India
Regional distribution of rainfall in general. The amount of rainfall decreases (a) away from the quarter on either side up to 30. north and south, and (b) from the coasts to wards the interior of continents. According to the amount of annual rainfall. There are five broad rainfall regions :
(1) Region of heavy rainfall (above 200 cm) which includes four distinct areas :
(i) Equatorial zone of doldrums where the temperature are very high through the year. The sun-warmed earth causes the humid surface air to rise in convectional currents resulting in heavy. Convectional rainfall. The maximum of heating is usually in the early afternoon. At this time there is a sudden downpour, often accompanied by thunder and lightning. During the season of heaviest precipitation, rain falls almost every day. There is no definite dry season. However, there is often a less wet season, particularly in these portions of the region which are further away from the equator.
(ii) Western coasts of continents in the zone of westernizes in cool temperature zone where the westernizes blowing from sea to land bring heavy rainfall. The rainfall is mainly associated with the passage of mid-latitude cyclones.
(iii) Coastal areas of monsoon lands which receive heavy rainfall from strong winds blowing from the Indian ocean towards low pressure areas in the interior of Asia during summer. The rainfall is particularly heavy on the windward slopes of mountains where it is orographic rainfall.
(iv) Windward slops of mountain ranges which intercept ocean winds causing heavy rainfall on their wind ward slopes. These ocean winds are the south-west monsoon in the western ghats, Himalays, and Araban Yoma, and westerlies in the Rockies, Alps, and Andes.
2. Region of moderate rainfall covering the castern coastal lands of the sub tropical belt. Main areas are most of the Brazilian Highlands in south America, most of central Africa, central north-east India, most of the central basins of lrrawady, Mekong, sikiang and yongize rivers, north Australia and south-east USA. These area surround the areas of heavy rainfall. The receive rainfall from trade sends and monsoons which have already shed much of their moisture in the high- rainfall areas. As such, these areas receive only moderate amounts of rainfall.
3. Region of low rainfall (50 cm to 100 cm) which includes-
(i) Interiors of continents in tropical latitudes - central- west south Americal, Central - west India, central - north and east Australia and central - east Africa ; and
(ii) West interior and east interior margins of continents in the temperature latitudes - Hwang No plain and surrounding lands in eastern Asia, west - central Europe, Central - east U.S.A., and north east Canada.
These areas receive rainfall from winds which have greatly exhausted themselves on wass. As such, the amounts of rainfall received are law.
4. Region of scanty rainfall (25 cm to 50 cm) which includes-
(i) Margins of tropical zone - central - west Australia, central southern south America, central - southern Africa, borderland of Sahara, and parts of central - west Asia ; and
(ii) Northern margin of cool temperature zone - central USSR; west - central USA ; and central Canada.
The prevailing winds become relatively dry by the time they enter these areas. Hence only scanty rainfall is received.
5. Region of very scanty rainfall. The various areas in this
region are all called deserts.
Deserts are of three types :
Hot deserts, mode - latitude deserts, and cold deserts.
Hot deserts along the western margins of continents in the trade wind belt. These are also called tropical deserts. They receive very scanty rainfall as the coins blocking in from landmasses are almost dry. Principal hot deserts are the Sahara desert in north Africa; Kalahari desert in south Africa, Arabian desert in south west Asia ; West Australian desert in Australia, and Atacama desert in south America.
Mid - latitude deserts are located in the interior regions of large containments, for away from the range of rain-bearing winds from the oceans. Principal mid-latitude deserts are the Gobi-desert in south America. cold deserts die in the Eurasian and Canadian tundra and in the lands around the north and the south poles. Precipitation in these deserts occurs as snowfall. 11-2. Seasonal distribution of rainfall. Rainfall is very unevenly distributed over the Earth's surface, and different places have chief rains occurring at different seasons. Seasonal distribution of rainfall may be summarized under the following categories :
1. Areas having rainfall at all seasons. These are -
(i) Equatorial low pressure belt, extending for a few degrees on either side of the equator, which has two very wet seasons and two rather lese wet seasons in the year.
2. Western margins of continents in the coal temperature zone which lie in the rack of the westernizes. These winds bring moisture - laden winds from oceans at all times. Further, depressions causing cyclonic rains occur throughout the year. However, more rain falls in autumn and winder than in the rest half of the year.
tropical deciduous forests
These are called the monsoon forests between 200 cm. & 75 cm. These forests easily catch fire. They are divided into two groups :
(i) Noist which are found on the slopes of western ghats having took as an important species.
(ii) The most deciduous forest found in north-eastern part of the Peminsula i.e. around chhotanagpers plates covering cast Madhya Pradesh, South Bihar and West Orissa along with Shivalias in the north having sat as the most important tree.
The Thorn and Scrus Forests :
These forests are found in region of 75 cm. rainfall, spreaded over north-western part of the country from saurashtra in the south to Punjab plains in the north, alongwith northern Madhya Pradesh, South-West Uttar Pradesh and Bundelkhand plateau, in the last having Kikar, Babul, Khair, Date palsns as most useful trees. They gradually fack away into scrubs and thorny bushes, which constitute the typical desert vegetation.
This is Project Report on Monsoon in India.
Bibliography