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India had Monsoonal climate.
Following factors are responsible for such climate:
1. Variation of
pressure on the surface during summer and winter and direction of
prevailing winds.
2. The orientation
of mountain ranges.
3. Jet streams and
their influence in upper air movement.
4. Western
disturbances.
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CHARACTERISTICS OF INDIAN MONSOON
(A) South- West Monsoon in summer
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During
summer south west monsoonal winds strike suddenly on the coast of Kerala, which
is called burst of monsoon. This sudden hit takes place every year on about 1st
june.
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South
West monsoon advances progressively from 1st june and covers entire
India by 15th of July when it reaches jaisalmer (Rajasthan).
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The
rainfall brought by the monsoon decreases away from the sea.
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The
monsoon donot give rise to a simple pattern of weather all over India. There
are dry areas, semi-arid areas and humid areas.
·
The
monsoon are pulsating in nature.
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The
withdrawal of monsoon is a much more gradual phenomenon than its arrival.
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Monsoon
starts retreating back from jaisalmer on 1st September and leaves
entire India by middle of December from east Tamil Nadu coast.
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During
summer season, rainfall is highly variable from region to region.
(B) North- East Monsoon in winter
During winter while
retreating back, winds becomes north- east and such winds when cross Bay of
Bengal, they become moist and produce rainfall in east Tamil Nadu and Andhra
Pradesh. Such winds are called-E Monsoon winds. These produce 40-60cm India
including parts of J& K, Punjab, Haryana, Delhi and Uttarakhand alsoreceive
witer rain due to influence of
(i) Jet Streams
(ii) Western
disturbances
JET STREAMS
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These
are strong wave of air circulating the earth at an altitude of 6 to 10 kms with
a speed of 250 to 400 kmph. These are 2 to 4 km thick, hundreds of km wide and
thousand of km long.
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Jet
streams are formed when pressur e gradient force becomes equal and opposite to
coriolis force.
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Jet
streams are a kind of Geo- strophic winds. Westerly jet streams of northern
hemisphere affext Indian climate during winter and produce little rainfall (2-5
cm)
ANNUAL RAINFALL
Rainfall regions may be
classified in three categories
1. Regions of heavy rainfall (more than
300 cms, per annum):
(i) Western slopes of Western
Ghats.
(ii) Eastern part of
India including Meghalaya hills.
(iii) Southern slopes
of Arunachal Himalaya.
2. Regions of very low rainfall (less
than 50 cms per annum);
(i) Western Rajasthan
(Thar Desert).
(ii) Leh and Ladakh
region of J & K.
(iii) Rain- shadow area
of Western Ghats in peninsular India.
3. Regions of moderate rainfall (50-300
cms per annum): Rest of remaining India receives moderate rainfall, however following trend is
seen:
(i) In south India
rainfall intensity decreases from coast towards interior.
(ii) In central India
rainfall intensity decreases from east coast towards west coast.
In northern India
rainfall decreases from north to south i.e. from Himalayan mountains towards
Genetic plain.
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Do You Know?
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Mawsynram located in khasi hills in
Meghalaya is the 2 nd wettest place of the worls followed by Hawaii Island
(USA) and Cherrapunji (Meghalaya, India).
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Avereage annual rainfall of India is
about 120 cms where as world’s average precipitation is about 100 cms per
annum.
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The most wettest place in the world
is Lloro, Colombia which gets an annual precipitation of 13,2999 mm.
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