Climate
1. Climate refers to the sum total of weather conditions and variations over a large area
for a long period of time (more than thirty years).
2. Weather refers to the state of the atmosphere over an area at any point of time.
3. The elements of weather and climate are the same,
i.e. temperature, atmospheric pressure, wind, humidity and precipitation
4. The climate of India is described as the ‘monsoon’ type
5. Precipitation
● While precipitation is mostly in the form of snowfall in the upper parts of Himalayas, it
rains over the rest of the country.
● The annual precipitation varies from over 400 cm in Meghalaya to less than 10 cm in
Ladakh and western Rajasthan.
● Most parts of the country receive rainfall from June to September. But some parts
like the Tamil Nadu coast gets a large portion of its rain during October and
November.
● There is decrease in rainfall generally from east to west in the Northern Plains.
● These variations have given rise to variety in lives of people – in terms of the food
they eat, the clothes they wear and also the kind of houses they live in.
6. CLIMATIC CONTROLS
There are six major controls of the climate of any place. LOPARD
a. Latitude
➔ Due to the curvature of the earth, the amount of solar energy received varies
according to latitude. As a result, air temperature generally decreases from the
equator towards the poles.
➔ The Tropic of Cancer passes through the middle of the country from the Rann of
Kuchchh in the west to Mizoram in the east.
➔ Almost half of the country, lying south of the Tropic of Cancer, belongs to the tropical
area. All the remaining area, north of the Tropic, lies in the sub-tropics.
➔ Therefore, India’s climate has characteristics of tropical as well as subtropical
climates.
b. Altitudes
➔ As one goes from the surface of the earth to higher altitudes, the atmosphere
becomes less dense and temperature decreases. The hills are therefore cooler
during summers.
➔ The Himalayas prevent the cold winds from Central Asia from entering the Indian
subcontinent, because of these mountains we experience comparatively milder
winters as compared to central Asia.
c. Distance from sea
➔ As the distance from the sea increases, its moderating influence decreases and the
people experience extreme weather conditions. This condition is known as
continentality (i.e. very hot during summers and very cold during winters).
d. Ocean currents
➔ Ocean current is the continuous movement of ocean water in a pattern, the pattern
may also change. This change in movement is influenced by wind, waves, slopes,
etc.
➔ These ocean currents can be either hot or cold.
e. Relief
➔ High mountains act as barriers to cold or hot winds; they may also cause precipitation
if they are high enough and lie in the path of rain-bearing winds. The leeward side of
the mountains remains relatively dry.
f . Pressure and winds
➔ 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.
7. The climate and associated weather conditions in India are governed by the following
atmospheric conditions:
a) Pressure
● India lies in the region of northeasterly winds. These winds originate from the
subtropical high-pressure belt of the northern hemisphere.
● They blow south, get deflected to the right due to the Coriolis force, and move on
towards the equatorial low-pressure area.
● Generally, these winds carry very little moisture as they originate and blow over land.
Therefore, they bring little or no rain.
● Hence, India should have been an arid land, but, it is not so.
Coriolis force: An apparent force caused by the earth’s rotation. The Coriolis force is
responsible for deflecting winds towards the right in the northern hemisphere and
towards the left in the southern hemisphere. This is also known as ‘Ferrel’s Law’.
b) surface winds;
● The pressure and wind conditions over India are unique.
● During winter, there is a high-pressure area north of the Himalayas. Cold dry winds
blow from this region to the low-pressure areas over the oceans to the south.
● In summer, a low-pressure area develops over interior Asia as well as over
northwestern India.
● This causes a complete reversal of the direction of winds during summer. Air moves
from the high-pressure area over the southern Indian Ocean, in a south-easterly
direction, cross the equator and turn right towards the low-pressure areas over the
Indian subcontinent. These are known as the Southwest Monsoon winds.
● These winds blow over the warm oceans, gather moisture, and bring widespread
rainfall over the mainland of India.
