• Climatic Controls
(3) Pressure and wind system
(5) Ocean Currents
• Importance of Himalaya
• Indian Monsoon
(1) Intensive heating at Tibet
(2) High pressure at Mascarene High
(3) La Nina
• Water Divide
9. The Tropic of Cancer passes through the
middle of the country from the Rann of
Kuchh in the west to Mizoram in the east.
Almost half of the country lying south of
the Tropic of Cancer, belongs to the
All the remaining area, north of the Tropic,
lies in the sub – tropics.
11. • Altitude:
As one goes from the surface of the
earth to higher altitudes, the
atmosphere becomes less dense and
12. India has mountains to the north which have an
average elevation of 6000 metres.
India also has a vast coastline area where the
maximum elevation is about 30 metres.
The Himalayas prevent the cold winds from
central Asia from entering the sub – continent.
It is because of these mountains that this sub
– continent experiences comparatively milder
winters than central Asia.
14. • Pressure & wind system :
The pressure and wind system of any area
depend on the latitude and altitude of the
place. Thus it influences the temperature
and rainfall pattern.
15. The climate and associated weather
conditions in India are governed by the following
atmospheric conditions –
pressure and surface winds
upper air circulation
western cyclonic disturbances and tropical
• Jet Stream
These are a narrow belt of high altitude westerly
winds in the troposphere.
These streams are located approximately over
27˚ to 30˚ north latitude, therefore they are called
sub tropical westerly jet streams.
Their speed varies from 110 kmph in summer to
184 kmph in winter.
Causes intense cold in winter.
17. • Distance from the sea (continentality) :
As the distance from the sea increases, its
moderating influence decreases and the
people experience extreme weather
conditions. This condition is known as
19. • Ocean currents :
Ocean currents along with onshore winds
affect the climate of the area, for example, any
coastal area with warm or cold ocean currents
flowing past it, will be warmed or cooled if the
winds are onshore.
20. • Relief :
Relief plays a major role in determining
the climate of a place. High mountains
act as barriers for cold or hot winds ;
they may also cause rainfall if they are
high enough and lie in the path of rain
23. Importance of Himalayas:
(1) Prevents cold Siberian winds to enter in
India. Hence, does not affect rainfall.
(2) India would be desert if Himalaya not there.
(3) It is source of perennial rivers which creates
great fertile plains.
(4) It has unique bio-diversity.
(5) Anthracite Coal- Only place (Kalakot, J&K) in
India where it found.
26. INTENSIVE HEATING OF TIBETIAN PLATEAU
• As a vast land mass, Tibetan plateau gets
intensely heated during summer.
• It results in strong vertical air currents.
• Formation of low pressure over the plateau.
27. HIGH PRESSURE OVER MADAGASCAR
• The presence of the high pressure area ,east of
• The intensity and position of this high pressure
area affects the Indian monsoon.
28. • During Summer,
India -----Low Pressure
Indian Ocean------ High Pressure
Moist clouds of rain formed in Indian Ocean flows
from high pressure to low pressure i.e. in India.
Hence, rainfall occurs in India.
30. EL Nino and Na Nina
• El Nino and La Nina are opposite phases of what
is known as the El Niño-Southern
Oscillation (ENSO) cycle.
• The ENSO cycle is a scientific term that describes
the fluctuations in temperature between the ocean
and atmosphere in the east-central Equatorial
• Southern Oscillation, refers to the seesaw
relationship of atmospheric pressures between
Tahiti, south pacific island and Darwin, Australia.
• La Niña, “anti-El Niño” or simply “a cold event” is the
cooling of water in the Eastern Pacific Ocean.
• Peru Current (Cold current) near Peru
• During Normal year, 2 things are Strong
(1) Cold Peru Current
(2) Trade Winds
• As a result the cold water is dragged towards Australia.
• Water region around Australia becomes low pressure
called Western Pacific Pool.
• Due to this, warm air ascends, it form clouds and rainfall
over North Australia.
• Due to high pressure since air descends at Peru, there is
drought in Atacama Desert.
33. • So, in a way 2 cycles are created.
(1) Below the water ----- From Peru to Australia
(2) Above the water ----- From Australia to Peru
• It is good for India as it causes good rainfall.
• Two things become weak
(1) Cold Peru Current
(2) Trade Winds
As a result cold water is not dragged from Peru
But reverse happens.
Warm Water+ Low Pressure--------- East Pacific
Cold Water + High Pressure--------- West Pacific
It occurs every 3-4 years. In theory, it should
occur every 12 years.
37. Effects of El- Nino:
• Rain and floods in Peru, Atacama desert and
even Southern USA.
• Drought in Northern Australia, Indonesia.
• Storms and Hurricanes in East Pacific.
• Coral Bleaching (Coral dies because of high
• It also decreases Earth’s rotation rate since it
changes the wind pattern. Hence, earth needs to
change the speed to conserve its angular
momentum of Earth’s Atmospheric System.
• Less rainfall in India.