Class 9 Geography Chapter 4 – Climate

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 refers to the state of the atmosphere over an area at any point in 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

Climatic Controls
The climate of any place depends on the following factors:
1) Latitude
The amount of solar energy received varies according to latitude due to the curvature
of the earth. That’s why air temperature generally decreases from the equator towards
the poles.
2) Altitude
The atmosphere becomes less dense, and temperature decreases when we go to a
higher altitude from the Earth’s surface. This is the reason why hills are cooler during
summer.
3) Pressure and wind system
The pressure and wind system of any area depend on the latitude and altitude of the
place. It influences the temperature and rainfall pattern.
4) Distance from the sea
The sea exerts a moderating influence on the climate. As the distance from the sea
increases, its moderating influence decreases and people experience extreme
weather conditions. This condition is known as continentality, i.e. very hot during
summers and very cold during winters.
5) Ocean currents
Ocean currents, along with onshore winds, affect the climate of the coastal areas. For
example, any coastal area with warm or cold currents flowing past it will be warmed or
cooled if the winds are onshore.
6) Relief features
Relief plays a major role in determining the climate of a place. 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. Precipitation is any form of moisture
which falls to the earth. It includes rain, snow, hail and sleet.
Factors Affecting India’s Climate
Latitude
The Tropic of Cancer passes through the middle of the country from the Rann of
Kachchh in the west to Mizoram in the east. India’s climate has characteristics of
tropical as well as subtropical climates.
Altitude
India has mountains to the north and also has a vast coastal area where the
maximum elevation is about 30 metres. Owing to the mountains, the subcontinent
experiences comparatively milder winters as compared to central Asia.
Pressure and 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.
Jet streams are fast-flowing, narrow, meandering air currents in the atmosphere.
The Indian Monsoon
The climate of India is strongly influenced by monsoon winds. The seasonal reversal
of the
wind system is known as “monsoon”. The monsoons are experienced in the tropical
area roughly between 20° N and 20° S. Go through the following facts to understand
the mechanism of the monsoons in a better way:
1. The differential heating and cooling of land and water create a low pressure
on the landmass of India while the seas around experience comparatively high
pressure.
2. The shift of the position of the Inter-Tropical Convergence Zone (ITCZ) in
summer over the Ganga plain is also known as the monsoon trough during the
monsoon season.
3. The presence of the high-pressure area east of Madagascar, approximately
20°S over the Indian Ocean, affects the Indian Monsoon.
4. The Tibetan plateau gets intensely heated during summer, which results in
strong vertical air currents and the formation of low pressure over the plateau at
about 9 km above sea level.
5. The movement of the westerly jet stream to the north of the Himalayas and
the presence of the tropical easterly jet stream over the Indian
peninsula during summer also impact the Indian Monsoon.
The changes in the pressure conditions over the southern oceans also affect the
monsoons. The irregularly periodic variation in winds and sea surface temperatures
over the tropical eastern Pacific Ocean that affects the climate of the tropics and
subtropics is known as Southern Oscillation or SO.
The Onset of the Monsoon and Withdrawal
The duration of the monsoon is between 100-120 days from early June to mid-
September. Around the time of its arrival, the normal rainfall increases suddenly and
continues constantly for several days, which is known as the “burst” of the monsoon.
Arrival of the Monsoon in Different Parts of India
The monsoon arrives at the southern tip of the Indian peninsula generally by the 1st
week of June. Subsequently, it proceeds into two – the Arabian Sea branch and the
Bay of Bengal branch.
 The Arabian Sea branch reaches Mumbai on approximately the 10th of June.
  The Bay of Bengal branch arrives in Assam in the 1st week of June.
 By mid-June, the Arabian Sea branch of the monsoon arrives over Saurashtra-
Kuchchh and the central part of the country.
 The Arabian Sea and the Bay of Bengal branches of the monsoon merge over
the northwestern part of the Ganga plains.
 Delhi receives the monsoon showers from the Bay of Bengal branch by the end
of June.
 By the first week of July, western Uttar Pradesh, Punjab, Haryana and eastern
Rajasthan experience the monsoon.
 By mid-July, the monsoon reaches Himachal Pradesh and the rest of the
country.
Withdrawal of the Monsoon
The withdrawal of the monsoon begins in the northwestern states of India by early
September. By mid-October, it withdraws completely from the northern half of the
peninsula. From north to south, the withdrawal of monsoon takes place from the first
week of December to the first week of January. By early December, the monsoon has
withdrawn from the rest of the country.
The Seasons
4 main seasons can be identified in India:
1. The cold weather season (Winter)
2. The hot weather season (Summer)
3. The advancing monsoon (Rainy Season)
4. The retreating monsoon with some regional variations (Transition Season)
Let’s discuss each of them in detail:
The Cold Weather Season (Winter)
Winter begins in mid-November in northern India and stays till February.
 December and January are the coldest months in the northern part of India.
 The temperature decreases from the south to the north.
 Days are warm and nights are cold.
 The weather is marked by clear sky, low temperatures and low humidity and
feeble, variable winds.
 This season is extremely important for the cultivation of ‘rabi’ crops.
The Hot Weather Season (Summer)
From March to May, a hot weather season is observed in India. The summer months
experience rising temperatures and falling air pressure in the northern part of the
country. A striking feature of the hot weather season is the ‘loo’. Loo is the strong,
gusty, hot, dry winds blowing during the day over north and northwestern India.
Towards the close of the summer season, pre-monsoon showers come, which help in
the early ripening of mangoes and are often referred to as ‘mango showers’.
Advancing Monsoon (The Rainy Season)
South-east trade winds originate over the warm subtropical areas of the southern
oceans. They cross the equator and blow in a southwesterly direction entering the
Indian peninsula as the southwest monsoon. The monsoon winds cover the country
for about a month. Mawsynram in the southern ranges of the Khasi Hills receives the
highest average rainfall in the world.
A phenomenon associated with the monsoon is its tendency to have ‘breaks’ in
rainfall. These breaks in monsoon are related to the movement of the monsoon
trough. The trough and its axis keep on moving northward or southward and
determine the spatial distribution of rainfall. The
frequency and intensity of tropical depressions also determine the amount and
duration of monsoon rains. The monsoon is known for its uncertainties. The
alternation of dry and wet spells varies in intensity, frequency and duration.
Retreating/Post Monsoons (The Transition Season)
The months of October-November form a period of transition from hot rainy season to
dry winter conditions. The retreat of the monsoon is marked by clear skies and a rise
in temperature. While day temperatures are high, nights are cool and pleasant. Owing
to the conditions of high temperature and humidity, the weather becomes rather
oppressive during the day. This is commonly known as ‘October heat’. In the second
half of October, the mercury begins to fall rapidly in northern India.
Distribution of Rainfall
1. Parts of the western coast and northeastern India receive over about 400 cm of
rainfall annually.
2. Rainfall is less than 60 cm in western Rajasthan and adjoining parts of Gujarat,
Haryana and Punjab.
3. Rainfall is low in the interior of the Deccan plateau and east of the Sahyadris.
4. Snowfall is restricted to the Himalayan region.
5. The annual rainfall is highly variable from year to year.
Monsoon as a Unifying Bond
The unifying influence of the monsoon on the Indian subcontinent is quite noticeable.
The seasonal alteration of the wind systems and the associated weather conditions
provide a rhythmic cycle of seasons. The uncertainties of rain and uneven distribution
are very much typical of the monsoons. Year after year, the people of India, from
north to south and from east to west, eagerly await the arrival of the monsoon. These
monsoon winds bind the whole country by providing water to set agricultural activities
in motion.
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…… Class 9 Geography Chapter 5 – Natural Vegetation and Wildlife
Natural vegetation refers to a plant community which has grown naturally without
human aid and has been left undisturbed by humans for a long time. This is
termed virgin vegetation.
The term flora is used to denote plants of a particular region or period. The species of
animals are referred to as fauna. This huge diversity in the flora and fauna kingdom is
due to the following factors:
1) Relief
Land
Land affects natural vegetation directly and indirectly.
 The fertile level is generally devoted to agriculture.
 The undulating and rough terrains are areas where grassland and woodlands
develop and give shelter to a variety of wildlife.
Soil
Different types of soils provide a basis for different types of vegetation.
 The sandy soils of the desert support cactus and thorny bushes, while wet,
marshy, deltaic soils support mangroves and deltaic vegetation.
 The soil at the hill slopes has conical trees.
2) Climate
Temperature
The character and extent of vegetation are mainly determined by temperature along
with humidity in the air, precipitation and soil. The fall in the temperature affects the
vegetation and its growth.
Photoperiod (Sunlight)
The variation in the duration of sunlight at different places is due to differences in
latitude, altitude, season and duration of the day. Due to the longer duration of
sunlight, trees grow faster in summer.
Precipitation
Areas of heavy rainfall have more dense vegetation as compared to areas of less
rainfall.
Types of Vegetation
In India, the following major types of vegetation are found:
1. Tropical Evergreen Forests
2. Tropical Deciduous Forests
3. Tropical Thorn Forests and Scrubs
4. Montane Forests
5. Mangrove Forests
Let’s study them in detail.
Tropical Evergreen Forests
These forests are present in the Western Ghats and the island groups of
Lakshadweep, Andaman and Nicobar, upper parts of Assam and Tamil Nadu coast.
1. These forests grow best in areas having rainfall of more than 200 cm with a
short dry season.
2. The trees reach great heights, up to 60 metres or even above.
3. It has vegetation of all kinds, i.e., trees, shrubs and creepers, giving it a
multilayered structure.
4. These forests appear green all the year-round.
5. Important trees of this forest are ebony, mahogany, rosewood, rubber and
cinchona.
6. Common animals found in these forests are elephants, monkeys, lemurs and
deer.
Tropical Deciduous Forests
These forests are also called monsoon forests.
1. They are spread over the region, having rainfall between 200 cm and 70 cm.
2. They shed their leaves about 6 to 8 weeks in the dry summer.
3. In these forests, the common animals found are lions, tigers, pigs, deer and
elephants.
These forests are further divided into:
 Moist deciduous: These are found in areas having rainfall between 200 and
100 cm. Teak is the most dominant species of this forest. Bamboos, sal,
shisham, sandalwood, khair, kusum, arjun and mulberry are other commercially
important species.
 Dry deciduous: These are found in areas having rainfall between 100 cm and
70 cm. There are open stretches in which teak, sal, peepal and neem grow.
The Thorn Forests and Scrubs
The natural vegetation consists of thorny trees and bushes. This type of vegetation is
found in the north-western part of the country, including semi-arid areas of Gujarat,
Rajasthan, Madhya Pradesh, Chhattisgarh, Uttar Pradesh and Haryana.
1. Trees are scattered and have long roots penetrating deep into the soil to get
moisture.
2. The stems are moist to conserve water.
3. Leaves are mostly thick and small to minimise evaporation.
4. Acacias, palms, euphorbias and cacti are the main plant species.
5. Common animals are rats, mice, rabbits, foxes, wolves, tigers, lions, wild
donkeys, horses and camels.
Montane Forests
Montane forests are forests which are found in the mountains.
1. The wet temperate type of forests is found between a height of 1000 and 2000
metres.
2. At high altitudes, generally more than 3,600 metres above sea level, temperate
forests and grasslands give way to the Alpine vegetation.
3. Alpine grasslands are used for grazing.
4. At higher altitudes, mosses and lichens form part of tundra vegetation.
5. The common animals found are Kashmir stag, spotted deer, wild sheep,
jackrabbit, Tibetan antelope, yak, snow leopard, squirrels, shaggy horn wild
ibex, bear and rare red panda, sheep and goats.
Mangrove Forests
Mangroves are trees that live along tropical coastlines, rooted in salty sediments,
often underwater.
1. The mangrove tidal forests are found in the areas of coasts influenced by
tides. Mud and silt get accumulate on such coasts.
2. Dense mangroves are the common varieties with roots of the plants
submerged underwater.
3. Sundari trees are found in the Ganga-Brahmaputra delta and provide hard
timber.
4. Royal Bengal Tiger is a famous animal in these forests.
Wildlife
India is rich in its fauna.
1. Elephants are found in the hot wet forests of Assam, Karnataka and Kerala.
2. One-horned rhinoceroses are found in Assam and West Bengal.
3. Rann of Kachchh is the habitat for wild donkeys, whereas the Thar Desert is the
habitat for camels.
4. The natural habitat of the Indian lion is the Gir forest in Gujarat.
5. Tigers are found in the forests of Madhya Pradesh, the Sundarbans of West
Bengal and the Himalayan region.
6. Ladakh’s freezing high altitudes are home to yak, the shaggy horned wild ox,
the Tibetan antelope, the bharal (blue sheep), wild sheep, and the kiang
(Tibetan wild donkey).
7. In the rivers, lakes and coastal areas, turtles, crocodiles and gharials are found.
8. Peacocks, pheasants, ducks, parakeets, cranes and pigeons are some of the
birds inhabiting the forests and wetlands of the country.
Cause of Major Threat to Flora and Fauna
Every species has an important role in the ecosystem. Hence, conservation of flora
and fauna is essential. About 1,300 plant species are endangered and 20 species are
extinct. The main causes of this major threat to nature are:
1. Hunting for commercial purposes
 2. Pollution due to chemical and industrial waste
3. Rapidly cutting of the forests for cultivation and habitation
Government Initiative to Protect Flora and Fauna
The government has taken many steps to protect flora and fauna of our country.
1. 18 biosphere reserves have been set up in India to protect flora and fauna. 10
out of these have been included in the world network of biosphere reserves.
2. Financial and technical assistance has been provided to many botanical
gardens by the government since 1992.
3. Project Tiger, Project Rhino, Project Great Indian Bustard and many other eco-
developmental projects have been introduced by the government.
4. 103 National Parks, 535 Wildlife Sanctuaries and Zoological gardens are set up
to take care of natural heritage

Chapter 6 population
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Population Size and Distribution
India’s Population Size and Distribution by Numbers
 As of March 2011, India’s population was 1,210.6 million, which accounts for
17.5% of the world’s population.
 Uttar Pradesh is the most populous state of India, as it counts about 16% of the
country’s population.
 Almost half of India’s population lives in just five states which are Uttar Pradesh,
Maharashtra, Bihar, West Bengal and Andhra Pradesh.
India’s Population Distribution by Density
Population Density is calculated as the number of persons per unit area. The
population density of India in the year 2011 was 382 persons per sq km. That’s why
India is considered one of the most densely populated countries in the world.
Population Growth and Processes of Population Change
The numbers, distribution and composition of the population are constantly changing.
This is the influence of the interaction of the three processes:
1. Birth
2. Death
3. Migration
Population Growth
Growth of population refers to the change in the number of inhabitants of a
country/territory during a specific period of time. This change can be expressed in 2
ways:
1. In terms of absolute numbers: The absolute numbers are obtained by
subtracting the earlier population (e.g. that of 2001) from the later population
(e.g. that of 2011).
2. In terms of percentage change per year: It is studied in percent per annum, e.g.
a rate of increase of 2 per cent per annum means that in a given year, there
was an increase of two persons for every 100 persons in the base population.
This is referred to as the annual growth rate.
Processes of Population Change/Growth
Three main processes of change of population are:
1) Birth rates: The birth rate is the number of live births per thousand persons in a
year. In India, birth rates have always been higher than death rates.
2) Death rates: The death rate is the number of deaths per thousand persons in a
year.
3) Migration: Migration is the movement of people across regions and territories.
Migration can be internal (within the country) or international (between the countries).
It influences the distribution of the population within the nation. In India, rural-urban
migration has resulted in a steady increase in the percentage of the population in
cities and towns.
Age Composition
The age composition of a population refers to the number of people in different age
groups in a country. The population of a nation is grouped into 3 broad categories:
1) Children (generally below 15 years): They are economically unproductive and
need to be provided with food, clothing, education and medical care.
2) Working Age (15–59 years): They are economically productive and biologically
reproductive. They comprise the working population.
3) Aged (Above 59 years): They may be working voluntarily, but they are not
available for employment through recruitment.
Sex Ratio
It is defined as the number of females per 1000 males in the population. Sex Ratio is
an important social indicator to measure the extent of equality between males and
females in a society at a given time.
Literacy Rates
According to the Census 2011, a person aged 7 years and above, who can read and
write with understanding in any language, is treated as literate. India’s literacy rate is
73%, as per the census of 2011.
Occupational Structure
The distribution of the population according to different types of occupation is referred
to as the occupational structure. Occupations are classified as:
1. Primary: Primary activities include agriculture, animal husbandry, forestry,
fishing, mining and quarrying, etc
2. Secondary: Secondary activities include the manufacturing industry, building
and construction work, etc.
3. Tertiary: Tertiary activities include transport, communications, commerce,
administration and other services.
Health
Health is an important component of population composition, which affects the
process of development. The substantial improvement in Public Health in our country
is the result of many factors, such as:
 Prevention of infectious diseases
 Application of modern medical practices in the diagnosis and treatment of
ailments
Adolescent Population
Adolescents are grouped in the age group of 10 to 19 years. They are the most
important resource for the future. It constitutes one-fifth of the total population of India.
The nutrition requirements of adolescents are higher than those of a normal child or
adult.
National Population Policy
The National Population Policy (NPP) 2000 provides a policy framework for imparting
free and compulsory school education up to 14 years of age. It also helps in
 reducing infant mortality rate to below 30 per 1000 live births
 Achieving universal immunisation of children against all vaccine-preventable
diseases
 Promoting delayed marriage for girls and making family welfare a people-
centred programme
NPP 2000 also put emphasis on other important needs of adolescents, including
protection from unwanted pregnancies and sexually transmitted diseases (STDs). It
aims to encourage:
 Delayed marriage and child-bearing
 Education of adolescents about the risks of unprotected sex
 Making contraceptive services accessible and affordable
 Providing food supplements
 Nutritional services
 Strengthening legal measures to prevent child marriage