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READY RECKONER OF INDIANGEOGRAPHY |24|

Narmada and Tapiriver valleys, these winds cause • By the end of September, the southwest monsoon
rainfall in extensive areas of central India. becomes weak as the low pressure trough of the
Thereafter, they enter the Ganga plains and mingle Ganga plain starts moving southward in response to
with the Bay of Bengal branch. the southward march of the sun.

(iii) A third branch of this monsoon wind strikes the • The retreating southwest monsoon season is marked
Saurashtra Peninsula and the Kachchh. It then by clear skies and rise in temperature. The land is still
passes over west Rajasthan and along the Aravalis, moist. Owing to the conditions of high temperature
causing only a scanty rainfall. and humidity, the weather becomes rather
oppressive. This is commonly known as the October
Monsoon Winds of the Bay of Bengal:
heat.
The Bay of Bengal branch strikes the coast of Myanmar
• The weather in the retreating monsoon is dry in north
and part of southeast Bangladesh. But the Arakan Hills
India but it is associated with rain in the eastern part
along the coast of Myanmar deflect a big portion of this
of the Peninsula. Here, October and November are
branch towards the Indian subcontinent.
the rainiest months of the year.
• The monsoon, therefore, enters West Bengal and
• The widespread rain in this season is associated with
Bangladesh from south and southeast instead of
the passage of cyclonic depressions which originate
south-westerly direction. From here, this branch splits
over the Andaman Sea and manage to cross the
into two under the influence of the Himalayas and
eastern coast of the southern Peninsula.These
the thermal low in northwest India.
tropical cyclones are very destructive.
• Its one branch moves westward along the Ganga
Characteristics of Monsoonal Rainfall:
plains reaching as far as the Punjab plains.
(i) Rainfall received from the southwest monsoons is
• The other branch moves up the Brahmaputra valley in
seasonal in character, which occurs between June
the north and the northeast, causing widespread
and September.
rains.
(ii) Monsoonal rainfall is largely governed by relief or
• Its sub-branch strikes the Garo and Khasi hills of
topography.
Meghalaya. Mawsynram, located on the crest of Khasi
hills, receives the highest average annual rainfall in (iii) The monsoon rainfall has a declining trend with
the world. increasing distance from the sea.

• Here it is important to know why the Tamil Nadu (iv) The monsoon rains occur in wet spells of few days
coast remains dry during this season. There are two duration at a time. The wet spells are interspersed
factors responsible for it: with rainless interval known as Monsoonal breaks.

(i) The Tamil Nadu coast is situated parallel to the (v) The summer rainfall comes in a heavy downpour
Bay of Bengal branch of southwest monsoon. leading to considerable run off and soil erosion.

(ii) It lies in the rain shadow area of the Arabian Sea (vi) Monsoons play a pivotal role in the agrarian economy
branch of the south-west monsoon. of India because over three-fourths of the total rainin
the country is received during the south- west
4. Season of Retreating Monsoon
monsoon season.
• The months of October and November are known for
(vii)Its spatial distribution is also uneven which ranges
retreating monsoons.
from 12 cm to more than 250 cm.
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