Unit 2 - PART.pptx

Global Warming & Climate change
Geethanjali College of Engineering and Technology
Cheeryala(V)
Keesara(M), Medchal Dist.
Telangana, INDIA
Pin Code-501301.
GLOBAL WARMING AND CLIMATE CHANGE

UNIT II: Atmosphere and Its Components
Importance of Atmosphere –
Physical and chemical characteristics of Atmosphere –
Vertical structure of the atmosphere –
Composition of the atmosphere –
Temperature profile of the atmosphere –
Lapse rates –
Temperature inversion –
Effects of inversion on pollution dispersion.
Atmospheric stability

Importance of Atmosphere
 Earth’s atmosphere is a thin blanket of gases and tiny particles — together
called air.
 Atmosphere is the air surrounding the earth.
 The Earth’s atmosphere is a mixture of gases and water vapour, and also of
some amount of aerosols (dust, smoke, condensation products of vapor)
 It contains life-giving gases like Oxygen for humans and animals and carbon
dioxide for plants.
 It envelops the earth all round and is held in place by the gravity of the
earth.
 It helps in stopping the ultraviolet rays harmful to the life and maintains the
suitable temperature necessary for life.
An atmosphere is a layer of gas or layers of gases that envelope a
planet, and is held in place by the gravity of the planetary body.

 Generally, atmosphere extends up to about 1600 km from the earth’s
surface. However, 99 % of the total mass of the atmosphere is confined to
the height of 32 km from the earth’s surface.
 The atmosphere is made up of different gases, water vapour and dust
particles.
 The composition of the atmosphere is not static and it changes according
to the time and place.

 Providing warmth and absorbing harmful solar rays.
 Life: oxygen and carbon dioxide, Many other particles and gases.
 Temperature: molecules in the atmosphere absorb the sun’s energy, spreading
that warmth across the planet - also trap reflected energy from the surface,
preventing the night side of the planet from becoming too cold.
 Radiation: The ozone layer blocks much of this radiation from reaching the
surface - absorb cosmic rays, gamma rays and x-rays, preventing striking living
things and causing mutations and other genetic damage.
 Physical Protection: The solar system reality it is full of debris and small
particles leftover from planetary creation or collisions in the asteroid belt.
According to NASA, more than 100 tons of space debris strikes Earth every single
day, When they encounter the molecules that make up Earth’s atmosphere, the
resulting friction destroys them long before they reach the ground
 Weather and Water: a medium for the movement of water. Vapor evaporates
out of oceans, condenses as it cools and falls as rain, providing life-giving
moisture to otherwise dry areas of the continents. According to the U.S.
Geological Survey, the Earth’s atmosphere holds around 12,900 cubic kilometers
(3,100 cubic miles) worth of water at any given time.
Importance of Atmosphere

Pressure of the atmosphere
 The normal atmospheric pressure at sea level is characterized by the
International Standard Atmosphere as 760.00 mmHg.
Density and Mass
 The density of air at sea level is about 1.2kg/m3 (1.2 g/L, 0.0012g/cm3).
 Is determined from estimations of temperature, weight and stickiness.
Environmental thickness diminishes as the height increments.
 The approximate mass of the atmosphere is about 5.15 × 1018 Kgs.

Chemical Composition of Atmosphere
 Nitrogen and oxygen are the two main gases - 99 %
 Other remaining gases argon, carbon dioxide, neon, helium, hydrogen, etc.
 % of gases changes in the higher layers - oxygen will be almost negligible
quantity at the heights of 120 km.
 CO2 (and water vapour) is found only up to 90 km from the surface of the
earth.

Chart of the overall atmospheric concentration and the relative percentages of trace gases.

Water Vapour
 Gases form of water present in the atmosphere is called water vapour.
 It is the source of all kinds of precipitation.
 The amount of water vapour decreases with altitude.
 It also decreases from the equator (or from the low latitudes) towards the
poles (or towards the high latitudes).
 Its maximum amount in the atmosphere could be up to 4% which is found
in the warm and wet regions.
 Water vapour reaches in the atmosphere through evaporation and
transpiration.
 Water vapour absorbs part of the incoming solar radiation (insolation) from the
sun and preserves the earth’s radiated heat. It thus acts like a blanket
allowing the earth neither to become too cold nor too hot.
 Water vapour also contributes to the stability and instability in the air.

Carbon dioxide:
 Carbon dioxide is meteorologically a very important gas.
 It is transparent to the incoming solar radiation (insolation) but
opaque to the outgoing terrestrial radiation.
 It absorbs a part of terrestrial radiation and reflects back some
part of it towards the earth’s surface.
 Carbon dioxide is largely responsible for the greenhouse effect.
 When the volume of other gases remains constant in the
atmosphere, the volume of the carbon dioxide has been rising in
the past few decades mainly because of the burning of fossil
fuels.
 This rising volume of carbon dioxide is the main reason for global
warming.

Ozone gas:
 Ozone is another important component of the atmosphere
found mainly between 10 and 50 km above the earth’s
surface.
 It acts as a filter and absorbs the ultra-violet rays radiating
from the sun and prevents them from reaching the surface of
the earth.
 The amount of ozone gas in the atmosphere is very little and
is limited to the ozone layer found in the stratosphere

Dust Particles
 Dust particles are generally found in the lower layers of the atmosphere.
 These particles are found in the form of sand, smoke-soot, oceanic salt, ash,
pollen, etc.
 Higher concentration of dust particles is found in subtropical and
temperate regions due to dry winds in comparison to equatorial and polar
regions.
 These dust particles help in the condensation of water vapour.
 During the condensation, water vapour gets condensed in the form of
droplets around these dust particles and thus clouds are formed.
Assignment
State the different compositional matter of the atmosphere and explain their
importance to the environment.

Vertical structure of the atmosphere
The atmosphere has five distinct
layers that are determined by the
changes in temperature that happen
with increasing altitude. Layers of
Earth’s atmosphere are divided into
five different layers as:
1.Thermosphere
2.Mesosphere
3.Stratosphere
4.Troposphere
5.Exosphere

Troposphere
 It is the lowermost layer of the atmosphere.
 The height of this layer is about 18 km on the equator and 8 km on the poles.
 The thickness of the troposphere is greatest at the equator because heat us transported
to great heights by strong convectional currents.
 Troposphere contains dust particles and water vapour.
 This is the most important layer of the atmosphere because all kinds of weather changes
take place only in this layer.
 The air never remains static in this layer. Therefore, this layer is called ‘changing sphere’
or troposphere.
 The environmental temperature decreases with increasing height of the atmosphere.
It decreases at the rate of 1 ̊C for every 165 m of height. This is called Normal Lapse
Rate.
 The zone separating troposphere from the stratosphere is known as tropopause.
 The air temperature at the tropopause is about – 80 degrees Celsius over the equator
and about – 45 degree Celsius over the poles. The temperature here is nearly constant,
and hence, it is called tropopause.

Stratosphere
 just above the troposphere, extends up to a of 50 km.
 The temperature remains almost the same in the lower part of this layer up to the
height of 20 km. After this, the temperature increases slowly with the increase in
the height.
 The temperature increases due to the presence of ozone gas in the upper part of this
layer.
 The air blows horizontally here. Therefore, this layer is considered ideal for flying of
aircraft.
 The upper limit of the stratosphere is known as stratopause.
 One important feature of stratosphere is that it contains a layer of ozone gas, found in
the lower portion of the stratosphere appx 20 to 30 km
 It is the region of the stratosphere that absorbs most of the sun’s ultra-violet
radiations.

Mesosphere
 It is the third layer of the atmosphere spreading over the stratosphere.
 It extends up to a height of 80 km.
 In this layer, the temperature starts decreasing with increasing
altitude and reaches up to – 100 degree.
 Meteors or falling stars occur in this layer.
 The top of the mesosphere, called the mesopause, is the coldest part
of Earth's atmosphere, with temperatures averaging about -130
degrees F (-90 degrees C)

Thermosphere
 This layer is located between 80 and 600 km above the
mesopause.
 It contains electrically charged particles known as ions, and
hence, it is known as the ionosphere.
 Radio waves transmitted from the earth are reflected back to
the earth by this layer and due to this, radio broadcasting has
become possible.
 The temperature here starts increasing with heights.
Exosphere
 highest layer of Earth's atmosphere and extends from the top of
the thermosphere approximately 6,200 miles (10,000 km) above
Earth's surface.
 The exosphere is composed of particles of hydrogen and
helium, that are so widely dispersed they rarely collide.

LAPSE RATES

REASON FOR LASE RATE

Atmospheric Stability

Atmospheric stability

Atmospheric Vertical Stability
• A stable atmosphere has weaker mixing in the
vertical
• An unstable atmosphere has a large amount of
mixing in the vertical
• A stable atmosphere is associated with air pollution,
fog, and strong surface temperature inversions in
winter.
• An unstable atmosphere is associated with lots of
atmospheric mixing, with good air quality and
sometimes convection/thunderstorms.

Stable Situation

Unstable

• An air parcel is an identifiable collection of air…think
of a balloon.
• The density of an air parcel depends on temperature
• Increase temperature > less dense
• Decrease temperature > more dense
• The equation that expresses this relationship is the
perfect (or ideal) gas law.
P = r R T
• P is pressure (Nm-2), r is density (mass/volume, kg m-3), T is
temperature (°K), R is the gas constant

Tp
Te
Up
Te may not necessarily the same as Tp
Temperature
Of the Environment
Temperature
Of the Air Parcel
The pressure of the parcel and the
environment are generally the same

Basic Rules
• If an air parcel is warmer than it surrounding environment,
then it is less dense than the environment as that level and
tends to rise.
• If an air parcel is the same temperature as the environment
at that level, it has the same density as the environment at
that level and will stay in position.
• If an air parcel is colder that the environment at the same
level, it is more dense than the environment and tends to
sink.

None of this should surprise you.
• A hot air balloon is warmer
and less dense than the
environment and rises.
• A lead balloon sinks
• Helium balloon rises because
He is less denser than the
gases in the atmosphere.

But why does a parcel of less dense
air rise?
Imagine an air parcel with the same density as the
environment
rp
re
Up
environment
Parcel
PT
PB
Weight
Pb > Pt, so there is an
upward force
That balances out the
weight. Stays put

Hydrostatic Balance
• The difference in pressure between the top and
bottom of the air parcel produces an upward
directed pressure gradient force.
• This force balance gravity (the weight of the air
parcel)
• Called HYDROSTATIC BALANCE.
• Most of the atmosphere is in this balance and that
is why the atmosphere doesn’t collapse.

A Stable Atmosphere
• stabilizing processes
nighttime surface radiational
cooling;
warm air advected to cold
surface;
air aloft warming (e.g.,
subsidence inversions)
• Stable air provides ideal
conditions for high pollution
levels.

An Unstable Atmosphere
• destabilizing processes
daytime solar heating of
surface air;
cold air advected to warm
surface
• superadiabatic lapse rates
(> 10 C/km)
• Unstable air tends to be
well-mixed.

Conditionally Unstable Air
• Conditional
instability:
environmental
lapse rate
between dry and
moist lapse rates
• Condensation
level
cloud base

 Temperature inversion, also called thermal inversion, a reversal
of the normal behavior of temperature in the troposphere (the
region of the atmosphere nearest Earth’s surface), in which a
layer of cool air at the surface is overlain by a layer of warmer
air.
 Under normal conditions air temperature usually decreases with
height.
Temperature inversion

 It is caused in stac atmospheric conditions while some times,
it occurs due to horizontal or vertical movement of air.
 Temperature inversion is usually of short duration but quite
common nonetheless.

Favorable Conditions for Temperature Inversion –
 Long winter nights: Loss of heat by terrestrial radiation from the
ground surface during night may exceed the amount of incoming
solar radiation.
 Cloudless and clear sky: Loss of heat through terrestrial radiation
proceeds more rapidly without any obstruction.
 Dry air near the ground surface: It limits the absorption of the
radiated heat from the Earth’s surface.
 Slow movement of air: It results in no transfer or mixing of heat
in the lower layers of the atmosphere.
 Snow covered ground surface: It results in maximum loss of heat
through reflection of incoming solar radiation.

There are four kinds of inversions: ground, turbulence, subsidence, and
frontal.
 A ground inversion develops when air is cooled by contact with a colder surface
until it becomes cooler than the overlying atmosphere;
 this occurs most often on clear nights, when the ground cools off rapidly by
radiation, If the temperature of surface air drops below its dew point, fog.
Ground Inversion (Surface Temperature
Inversion)
 This kind of temperature
inversion is very common in the
higher latitudes.
 Surface temperature inversion in
lower and middle latitudes
occurs during cold nights and
gets destroyed during daytime.

 A turbulence inversion often forms when quiescent air overlies
turbulent air.
 Within the turbulent layer, vertical mixing carries cools downward
and heat the upper part of the layer.
 The unmixed air above is not cooled and eventually is warmer than
the air below; an inversion then exists.
A turbulence inversion

 A subsidence inversion develops when a widespread layer of air
descends. The layer is compressed and heated by the resulting
increase in atmospheric pressure, and, as a result, the lapse rate of
temperature is reduced.
 If the air mass sinks low enough, the air at higher altitudes
becomes warmer than at lower altitudes, producing a
temperature inversion.
Subsidence inversion
 Subsidence inversions are
common over the
northern continents in winter an
d over the subtropical oceans;
 these regions generally have
subsiding air because they are
located under large high-
pressure centres.

 A frontal inversion occurs when a cold air mass undercuts a
warm air mass and lifts it aloft; the front between the two air
masses then has warm air above and cold air below.
 This kind of inversion has a considerable slope, whereas other
inversions are nearly horizontal.
 In addition, humidity may be high, and clouds may be present
immediately above it.
Frontal Inversion

Effects of inversion on pollution dispersion.
 Dust particles hanging in the air
 Air pollutants - dust particles and smoke do not disperse on the
surface.
 Stops the movement of air
 Less rainfall
 Thunderstorms and tornadoes
 Diurnal variations in temperature - less

Temperature inversion determines the precipitation, forms of clouds,
and also causes frost due to condensation of warm air due to its cooling.
 Dust particles hanging in the air: An inversion acts as a cap on the upward
movement of air from the layers below. As a result, convection produced by the
heating of air from below is limited to levels below the inversion. Diffusion of
dust, smoke, and other air pollutants is likewise limited.
 Stops the movement of air: It causes the stability of the atmosphere that stops the
downward and upward movement of air.
 Less rainfall: Convection clouds can not move high upwards so there is less
rainfall and no showers. So, it causes a problem for agricultural productivity.
 Lower visibility: Visibility may be greatly reduced below the inversion due to the
accumulation of dust and smoke particles. Because air near the base of an
inversion tends to be cool, fog is frequently present there..
 Thunderstorms and tornadoes: Intense thunderstorms and tornadoes are also
associated with inversion of temperature because of the intense energy that is
released after an inversion blocks an area’s normal convention patterns.
 Diurnal variations in temperature tend to be very small.

 The strength and duration of the inversion and elevation of the release compared to the
inversion elevation has a large influence on the air quality.
 Air pollution will continue to accumulate until inversion disappears.
 Traffic particularly and other sources add more pollutants to the air.
 A strong and low height inversion will lead to high pollutant levels, while a weak inversion
will lead to lower levels.
 In other words, the smaller is the mixing volume; the higher is the pollution
concentration. Inversions are also stronger and more common during the winter months.
 In summer, inversions are less frequent and weaker.

Q5: exactly at what height in the figure would Tp = Te?
a) above 2 km, b) at 2 km, c) at 1.33 km
Q6: If environmental lapse is greater than dry lapse rate, the
atmosphere is
a) stable, b) unstable, c) conditionally unstable
Q7: If environmental lapse is less than moist lapse rate, the
atmosphere is
Q8: The earth’s atmosphere is ordinarily
Q9: The air T in an unsaturated parcel follows the
a) dry lapse rate, b) moist lapse rate,
c) environmental lapse rate
Q10: If air T increases with height, the air is surely stable. If it
decreases with height, the air is:
a) stable, b), unstable, c) undecided

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