Wednesday, 3 February 2016


·       The sum total of weather conditions and variations over a large area for a long period of time (more than thirty years) is called climate.
·       The state of the atmosphere over an area at any point of time is called weather.
·       This type of climate is mainly found in the south and Southeast Asia.
·       The climate of India is of monsoon type.
·       The seasonal reversal in wind direction during a year is called monsoon.
Coriolis Force:
·       An apparent force caused by the earth’s rotation is called Coriolis Force.
·       The winds are deflected towards right in the northern hemisphere and,
·       Towards the left in the southern hemisphere due to this force. This is also known as ‘Ferrel’s Law’.
Jet Stream:
·       Fast flowing and narrow air currents are called jet streams.
·       The streams flow at high altitudes (about 12,000 feet) in the troposphere.
·       Their speed varies from about 110 km/h in summer to 184 km/h in winter.
Western Cyclonic Disturbance:

·       The western cyclonic disturbances are weather phenomena of the winter months brought in by the westerly flow from the Mediterranean region.
·       They usually influence the weather of the north and north-western regions of India.
Inter Tropical Convergence Zone (ITCZ):
·       The Inter Tropical Convergence Zone (ITCZ,) is a broad trough of low pressure in equatorial latitudes.
·        The northeast and the southeast trade winds converge in this zone.
·        This zone lies more or less parallel to the equator.
·       It moves north or south with the apparent movement of the sun.
There are six major controls of the climate of any place. They are:

1.  Latitude,
2.  Altitude,
3.  Pressure and wind system,
4.  Distance from the sea,
5.  Ocean currents and
6.  Relief features

Factors Affecting India’s Climate :

·       The Indian landmass is equally divided by The Tropic of Cancer.
·       Hence, half of India has tropical climate and another half has subtropical climate.


·       While the average elevation in the coastal areas is about 30 metre,
·       the average elevation in the north is about 6,000 metre.
·       The Himalayas prevent the cold winds from Central Asia from entering the Indian subcontinent.
·       Due to this, the subcontinent gets comparatively milder winters as compared to Central Asia.
Pressure and Winds:
·       The Indian subcontinent lies in the region of north-easterly winds.
·       These winds originate from the subtropical high-pressure belt of the northern hemisphere.
·       After that, these winds blow towards south. They get deflected to the right due to the Coriolis force and then move towards the low pressure area near the equator.
·        The north-easterly winds originate and blow over the land and hence they carry very little moisture.
·       India should have been an arid land because of these winds but that is not the case.
·       There is high-pressure area towards the north of the Himalayas. Cold winds from this region blow to the low pressure areas over the oceans in the south.
·       During summer, low-pressure area develops over interior Asia and also over northwestern India. This results in a complete reversal of the direction of winds during summer.

·       Air; from the high-pressure area moves over the southern Indian Ocean in a south-easterly direction.
·       It crosses the equator and turns right towards the low-pressure areas over the Indian subcontinent.
·       These winds are known as the Southwest Monsoon wind.
·       They collect moisture from the warm oceans and bring widespread rainfall over the mainland of India.
·        The upper air circulation in this region is dominated by a westerly flow.
·       Jet stream is an important component of this flow.
·       These jet streams are called subtropical westerly jet streams because they are located approximately over 27°-30° north latitude.
·       The westerly jet streams are responsible for western cyclonic disturbances in the north and north-western parts of India.
·       The subtropical westerly jet stream moves north of the Himalayas with the apparent movement of the sun.
·       The tropical jet stream (an easterly jet stream) blows over the Indian Peninsula; approximately over 14° north during the summer months.


  1. sir pls continue ncert notes . it would be reallyy helpful

  2. i ll be really thankful.