SHALOM HILLS INTERNATIONAL SCHOOL

CLIMATE CLASS 9 NOTES

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).

Weather :-

Weather refers to the state of the atmosphere over an area at any point of time.

The elements of weather and climate are the same, i.e. temperature, atmospheric pressure, wind,
humidity and precipitation. On the basis of the monthly atmospheric conditions, the year is divided into
seasons such as:

 Winter
 Summer
 Rainy Seasons
Difference between weather and climate :-
weather Climate

Weather is a day-to-day state of the Climate is the total of weather

atmosphere of an area at any given conditions of a given place over a
point of time. longer period of time.

Climate of a given place remains

Weather changes on a daily basis.
constant for over 30 to 40 years.

monsoon :-

The word monsoon is derived from the Arabic word ‘mausim’ which literally means season.

Monsoon refers to the seasonal reversal in the wind direction during a year.

The climate of India :-

The climate of India is described as the ‘monsoon’ type. In Asia, this type of climate is found mainly in
the south and the southeast. Despite an overall unity in the general pattern, there are perceptible regional
variations in climatic conditions within the country.

Examples :- there is hardly 20 cm of rainfall annually in the western parts of Rajasthan and Gujarat,
Assam and Arunachal Pradesh receive more than 250 cm of rainfall. During winters, the night temperature
may fall below -45°C, while on the same night, Thiruvananthapuram may experience a temperature of 45°C.
These variations have resulted in different lifestyles of the people.

Climatic Controls :-
 There are six major controls of the climate of any place. They are :-

 latitude
 altitude
 pressure and wind system
 distance from the sea (continentality)
 ocean currents
 relief features.
Factors affecting climate of India :-

 Latitude
 Altitude
 Distance from sea
 Ocean current
 Relief features or landscape or surface of earth.
 Pressure and Wind system

Latitude :-

Tropic of Cancer, a latitude, passes through India at 23°26’N to the north of the equator. It passes
through eight Indian states running from the Rann of Kutch of Gujarat to Mizoram in the east.

The Tropic of Cancer divides the country into two halves. The areas in India which lie to the north of the
Tropic of Cancer lie in the sub-tropical regions, while the areas to the south of the tropic lie in the tropical
regions.

The temperature remains high throughout the tropical regions.

Altitude :-

The temperature declines as we travel to places above the sea level. Thus, the temperature decreases
with an increase in altitude.

There is a decrease of 1°C for every 166 m rise in height. This is the reason that hill stations in India are
cooler than the plain regions.

Air Pressure and Surface Winds :-

 The climate and weather conditions in India are governed by the following atmospheric conditions:
 Pressure and surface winds
 Upper air circulation
 Western cyclonic disturbances and tropical cyclones
 Air moves from the high-pressure area over the southern Indian Ocean, in a south-easterly direction, crosses
the equator and turns 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 territories of India.
 India lies in the region of northeasterly surface winds. During winters, the subtropical high-pressure belt of the
Northern hemisphere leads to the origin of Northeastern winds. The winds blow in the southern direction and get
deflected to the right. In winters, high-pressure areas develop over the north of Himalayas. Hence, cold, dry winds
blow from the Himalayas towards the low-pressure areas over the oceans in the south.
 However, in summers, a low-pressure area develops over northwestern India. Therefore, the wind direction is
reversed. Now, the winds move from the high-pressure area over the Indian Ocean to cross the equator and then
turn right to reach the low-pressure areas. Since these winds move over the warm ocean, they carry a large amount
of moisture leading to widespread rainfall.

The Seasons :-
On the basis of generalized monthly atmospheric conditions, the year is divided into seasons such as
winter, summer or rainy seasons. Particular weather patterns and daylight hours over a few weeks or
months i.e days are cool or hot, windy or calm, wet or dry are known as seasons.

A country with a monsoon type of climate experiences distinct seasons. India experiences the following
seasons :-

 The cold weather season

 The hot weather season
 The advancing monsoon
 The retreating monsoon (with some regional variations)
The cold weather season (Winter Season) :-

 It begins from mid November in northern India and stays till February.
 The temperature decreases from south to the north.
 Days are warm and nights are cold. Frost is common in the north and the higher slopes of the Himalayas
experience snowfall.
 The northeast trade winds prevail over the country.
 In the northern India, a feeble high-pressure region develops, with light winds moving outwards from this
area.
The Hot Weather Season (The Summer Season) :-

 It begins from March to May.

 The summer months experience rising temperature and falling air pressure in the northern part of the
country.
 A striking feature of the hot weather season is the ‘Loo’. ‘Loo’ is strong, gusty, hot, dry winds blowing
during the day over the north and northwestern India.
 Dust storms are common and sometime may bring light rain and cool breeze.
 During summer Sometimes localized thunderstorm along with violent wind, torrential downpours
accompanied by hail occurs which is called ‘Kaal Baisakhi’ in west Bengal.
 Pre-monsoon showers are common especially, in Kerala and Karnataka. They help in the early ripening of
mangoes, and are often referred to as ‘mango showers’.
Advancing Monsoon (The Rainy Season) :-
 By week of June, low pressure conditions get intensified over the North Indian Plains. These conditions
attract the southeast trade winds which originate from the Southern oceans.
 These winds blow over the warm oceans and thus bring moisture and rainfall to the country.
 During the early monsoon season, the places located on the windward side of the Western Ghats receive
heavy rainfall up to 250 cm.
 The northeastern parts of the country receive heavy rainfall. Mawsynram in Meghalaya receives the highest
amount of rainfall in the world.
 As we go from the east to the west, the rainfall decreases. Rajasthan and Gujarat receive scanty rainfall.
 Rain does not fall continuously during the monsoon season. Thus, there are dry spells and wet spells.
Monsoons are uncertain and irregular.
Retreating Monsoon :-

 During October and November, the southwest monsoon winds become weaker and start retreating from the
Northern Plains by the beginning of October.
 The retreat is indicated by clear skies and an increase in the temperature in the northern plains. This increase
in temperature is termed ‘October heat’.
 At this time, the low pressure conditions shift to the Bay of Bengal, giving rise to cyclonic depressions.
These cyclonic depressions often result in the destruction of life and property, generally on the eastern coast
and the southern coast.
 Most of the rainfall in the Coromandel Coast is derived from depressions and cyclones.
Distribution of Rainfall :-

 Rainfall distribution is not the same for every part of the country. While northeastern India and the parts of
the western coast receive about 400 cm of rainfall annually, western Rajasthan and the western parts of
Gujarat, Punjab and Haryana receive less than 60 cm of rainfall.
 The winds which rise from the Arabian Sea are full of moisture. These winds strike the mountains on the
western side resulting in heavy rainfall. By the time these winds reach the Eastern Ghats, they are already
dry as they already shed their moisture. Hence, the Western Ghats receive more rainfall than the Eastern
Ghats.
 Rainfall is also low in the Eastern Ghats, interior parts of the Deccan Plateau and the Leh region of Jammu
and Kashmir.
 The other parts of the country receive moderate rainfall.
 Such a distribution of rainfall causes great climatic variations. While the eastern parts of the countr almost
get flooded every year, the western parts of the country experience drought like situation.

Monsoon as a Unifying Bond :-

Although the monsoon winds are irregular and uncertain, they unify the entire country.
The farmers eagerly wait for the arrival of rainfall. Rainfall provides the water required to set
agricultural activities in motion.
Its arrival is welcomed with the celebration of festivals, singing and dancing. Many Indian festivals
which are known by different names around the country are related to the agriculture cycle that are decided
by the monsoon.
The flora and fauna of the country are very much influenced by the monsoon.
The water from the monsoon fills up the rivers which are used by humans and animals for different
purposes.

Thanks
Kavita Yadav