CLIMATE :

Climate:

·       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.

Weather:

·       The state of the atmosphere over an area at any point of time is called weather.

Monsoon:

·       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.

CLIMATIC CONTROLS
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 :

Latitude:

·       The Indian landmass is equally divided by The Tropic of Cancer.

·       Hence, half of India has tropical climate and another half has subtropical climate.

Altitude:

·       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.