DEFINITION
• The atmosphereis a layer of gases that
surrounds the Earth, composed primarily of
nitrogen and oxygen, along with trace
amounts of other gases.
• It plays a crucial role in sustaining life by
providing breathable air, protecting from
harmful UV radiation, and regulating
temperature through the trapping of heat
3.
SIGNIFICANCE
• . Theatmosphere consists of five main
layers, each with distinct
characteristics and functions,
including the troposphere, where
weather occurs, and the stratosphere,
which contains ozone and absorbs UV
radiation.
TROPOSPHERE
• Lowest andthinnest layer
—18 km at equator, 8 km at poles
• 75% of the atmosphere’s mass
• Temperature decreases with altitude
—1°C per 165 metres called as Normal
Lapse Rate
• The layer supports life and
controls weather and climate.
• Boundary between the troposphere,
and the stratosphere is called the
tropopause
8.
STRATOSPHERE
• Strato meanslayers
• Extends upto 50 km above the
ground
• Less dense (less water
vapor),less dust particles,has
minimal air turbulence and
ideal for flying airplanes.
• Temperature increases with
altitude
• Protect us from harmful ultra
violet radiations > ozone layer
Upper boundary is called
stratopause
10.
MESOSPHERE
• Extends toalmost
80 km high
• Meso means
middle.
• As meteorites enter
this layer,they burn
up due to friction
with gaseous
particles.
• Temperature
decreases as
altitude increases.
11.
THERMOSPHERE
• Lies abovethe mesosphere and
extends to almost 450km .
• temperature increases with
altitude
• readily absorbs solar radiation
• Temperature can go as high as
2000 °C
• Helps in satellite
communication and
radio transmission.
12.
EXOSPHERE
• The outermost
layerof the
atmosphere.
• Lacks dust,gases
and water
vapour.
• Many
communication,
weather and
navigation
satellites orbit in
this layer.
13.
IMPORTANCE OF GASES
•Nitrogen (N ):
₂
• Abundance: Comprises about 78% of the atmosphere.
• Role: While nitrogen is relatively inert and does not
directly support life, it is crucial for the nitrogen cycle.
Nitrogen-fixing bacteria convert atmospheric nitrogen
into forms that plants can use to synthesize proteins and
DNA, which are essential for all living organisms.
14.
OXYGEN (O )
₂:
• Abundance: Makes up about 21% of
the atmosphere.
• Role
: Oxygen is vital for the respiration of
most living organisms. It allows cells to
convert food into energy. Additionally
, oxygen is produced by plants during
photosynthesis, which is essential for m
aintaining the balance of life on Earth
.
15.
CARBON DIOXIDE (CO)
₂ :
• Abundance: Represents about 0.04%
of the atmosphere.
• Role: Carbon dioxide is crucial for pho
tosynthesis, where plants absorb CO₂
and release oxygen. It also plays a sig
nificant role in regulating the Earth's te
mperature through the greenhouse ef
fect, helping to maintain a climate sui
table for life.
16.
ARGON
• Chemically inactivegas.
• Does not support biological
processes.
• Used in electric bulbs and welding.
17.
OTHER GASES
• WaterVapour: Play a crucial role in weather and
climate. Also plays a crucial role in the hydrological
cycle.
• Dust Particles: Necessary for rainfall formation.Enriches
ecosystem and supports plant & marine life.
• Ozone : Absorbs ultra violet radiations.Protects us from
skin cancer and genetic damage.
18.
CLIMATE AND WEATHER
•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). For e.g.,
India
• Weather refers to the state of the atmosphere over
an area at any point of time. For e.g. , South
Extension, Andrews Ganj etc.
This Photo by Unknown author is licensed under CC BY-NC.
19.
ELEMENTS OF
WEATHER AND
CLIMATE
THEELEMENTS OF WEATHER AND CLIMATE
ARE THE SAME.
Temperature
Atmospheric pressure
Wind
Humidity
Precipitation.
20.
HOT WEATHER SEASON
×Main characteristics of the hot weather
season in India are:
1.The hot weather season in India begins
from March and continues till May.
2.In May, the temperature rises to 45°C in
the northwestern parts of the country.
3. Because of high temperature, low air
pressure is created in the northern parts
of the country.
20
21.
4.One of thestriking features of the hot weather
season in India is the blowing of local winds known as
‘loo’. It is a hot wind which may blow even during the
evenings. Direct exposure to these winds may cause
fever and anxieties.
5.Sometimes, northern India experiences dust storms
accompanied by light rainfall during May. This brings
down the temperature.
6.During this time, torrential downpours are
accompanied by hail in West Bengal. These storms
are known as Kaal Baisakhi.
7.Towards the end of the summer season, rain showers
are common in Kerala and Karnataka. They help in
the early ripening of mangoes and thus are
sometimes also referred to as ‘mango showers’
21
22.
SEASONS
× HOT WEATHERSEASON (MARCH TO MAY)
× MONSOON /RAINY ( JUNE TO SEPTEMBER)
× RETREATING MONSOONS(OCTOBER TO NOVEMBER)
× COLD WEATHER SEASON( DECEMBER TO FEBRUARY
22
25
1. The ArabianSea branch - The monsoon winds
originating over the Arabian Sea.
2. The Bay of Bengal branch - The Arakan Hills
along the coast of Myanmar deflect a big portion
of this branch towards the Indian subcontinent.
The monsoon, therefore, enters West Bengal
and Bangladesh from south and southeast
instead of from the south-westerly direction.
The monsoon approaches the Indian landmass in two branches:
• As thesewinds climb the slopes of the
Western Ghats, they become cooler, their
moisture retention capacity reduces and
as a result, the windward side of the
Sahyadris and Western Coastal Plain
receive very heavy rainfall ranging
between 250 cm and 400 cm.
• Much of the rainfall along the Western
Ghats is thus orographic, as the moist air
is obstructed and forced to rise along the
Ghats.
28
29.
This Photo byUnknown author is licensed under CC BY-NC-ND.
