Atmospheric science is the study of the atmosphere, its processes, and interactions with other systems. It includes subdisciplines like atmospheric physics, chemistry, dynamics, climatology, meteorology, and the study of other planetary atmospheres. Meteorology focuses on weather forecasting and includes the study of temperature, pressure, humidity, wind, and their changes over time. The history of meteorology dates back thousands of years, with early contributions from cultures around the world, and major advances driven by scientific discoveries over the centuries. Modern meteorology plays an important role in fields like navigation, aviation, agriculture, and understanding climate change.

1. Geronimo R. Rosario

2.  Atmospheric science- is an umbrella term for the
study of the atmosphere, its processes, the effects
other systems [such as the oceans] have on the
atmosphere, and the effects of the atmosphere on
these other systems.
 Major Subdivisions of Atmospheric Science
◦ Atmospheric Physics
◦ Atmospheric Chemistry
◦ Atmospheric Dynamics
◦ Climatology
◦ Meteorology and Forecasting
◦ Extraterrestrial Planetary Atmospheric Science

3.  Atmospheric physics is the application of physics to the
study of the atmosphere.
 Atmospheric physicists attempt to model Earth’s
atmosphere and the atmospheres of the
other planets using fluid flow equations, chemical models,
radiation balancing, and energy transfer processes in the
atmosphere (as well as how these tie into other systems
such as the oceans).
 Atmospheric Chemistry- is a branch of atmospheric
science in which the chemistry of the Earth’s atmosphere
and that of other planets is studied.
 It is a multidisciplinary field of research and draws on
environmental chemistry, physics, meteorology, computer
modelling, oceanography, geology and volcanology and
other disciplines.

4.  Atmospheric Dynamics- involves observational
and theoretical analysis of all motion systems of
meteorological significance, including such diverse
phenomena as thunderstorms, tornadoes, gravity
waves, tropical hurricanes, extratropical cyclones,
jet streams, and global-scale circulations.
 Climatology- is the study of atmospheric changes
(both long and short-term) that define average
climates and their change over time, due to both
natural and anthropogenic climate variability.

5.  Extraterrestrial Planetary Atmospheric Science
– the study of the atmospheric processes of other
planets.

 Meteorology includes atmospheric chemistry and
atmospheric physics with a major focus on
weather forecasting. It is the study of the state and
processes of the atmosphere such as weather and
climate and how changes in temperature,
pressure, humidity and wind speed and direction
take place.

6.  Major Branches of Meteorology

 Physical meteorology - deals with the physical aspects of
the atmosphere, such as the formation of clouds, rain,
thunderstorms, and lightning. Physical meteorology also
includes the study of visual events such as mirages,
rainbows, and halos.
 Dynamic meteorology - the study of the winds and the
laws that govern atmospheric motion. Equations that
describe atmospheric motions.
 Synoptic meteorology - is the study and analysis of large
weather systems that exist for more than one day. Weather
forecasting is part of synoptic meteorology. Day-to-day
weather and forecasting.

7.  Major Branches of Meteorology
 Agricultural meteorology - deals with weather
and its relationship to crops and vegetation.
 Climatology - is the study of a region’s average
daily and seasonal weather events over a long
period. Climate describes the average weather of
a region.
 Aeronomy- is the study of the upper atmosphere
with emphasis on composition and interaction with
solar radiation.

8.  Branches of Meteorology according to spatial distance
 Microscale Meteorology - the study of atmospheric phenomena
about 1 km or less, smaller than mesoscale, including small and
generally, thunderstorms, fleeting cloud "puffs" and other small cloud
features.
 Mesoscale Meteorology – the study of weather systems about 5
kilometers to several hundred kilometers, smaller than synoptic scale
systems but larger than microscale and storm-scale cumulus systems,
such as sea breezes, squall lines, and mesoscale convective
complexes.
 Sypnoptic Scale meteorology- is a horizontal length scale of the
order of 1000 kilometres (about 620 miles) or more. The phenomena
typically described by sypnoptic meteorology include events like
extratropical cyclones, baroclinic troughs and ridges, frontal zones, and
to some extent jet streams.

9.  Weather and Climate
 Weather – is the condition of the atmosphere at a
particular place over a short period of time.
◦ Weather can be described in terms of temperature,
precipitation (snow, rain & hail), wind speed and
direction, visibility and cloud amounts.
 Climate - refers to the weather pattern of a place over a
long period, maybe 30 years or more, long enough to
yield meaningful averages.

10.  Ancient Times
 3000 BC – The beginnings of meteorology can be traced
back in India to 3000 B.C.E. Writings such as the
Upanishads, contain serious discussion about the
processes of cloud formation and rain and the seasonal
cycles caused by the movement of earth round the sun.
 600 BC – Thales, first Greek meteorologist who described
water cycle.
 400 BC – Democritus predicted changes in the weather.
 400 BC – Hippocrates discussed weather in his
treatise Airs, Waters and Places. locations, seasons,
winds and air.
 350 BC – Aristotle writes Meteorologica.

11.  350 BC -Theophrastus, a pupil of Aristotle, compiled a book on
weather forecasting, called the Book of Signs.
 250 BC - Archimedes studied the concepts of buoyancy and the
hydrostatic principle. Important for convertive clouds formation (eg.
cumulus)
 240 B.C. - Eratosthenes a Greek Librarian calculated
circumference of spherical Earth about 40,000 km. (Alexandria and
Syene(Aswan))= 5,000 stadia distance. 1 stadia= 0.16 km)
Alexandria -7.2o. Actual circumference of the earth is 40,032 km.
Erastosthenes estimates was 40,000 km (very close!).
 150 A.D. - Ptolemy of Egypt's modified the early works of
Apollonius and Eudoxus and proposed the Geocentric model
where the earth is at the center of the universe and all the planetary
objects including the sun and moon orbit around it
 25 AD - Pomponius Mela, Roman geographer formalized the
climatic zone system.
 80 AD – Wang Chong, dispelled the Chinese myth on rain ocming
from heavens and stated that rain came from evopatrated water and
condensed into clouds and precipitate into rain.

12.  Middle Ages
 1088 - Shen Hou, Chinese scientist, wrote vivid
descriptions of torandaoes, rainbow and lightning.
 1121 - Al Khazini, Muslim Scientist, studied hydrostatic
balance
 13th century- St. Albert the Great, described the
spherical shape of rain which in effect produced the
rainbow..
 1267 -Roger Bacon, first to calculate the angular size of
the rainbow. He stated that the rainbow summit can not
appear higher than 42 degrees above the horizon.
 1441 - Prince Munjong, invented the first standardized
rain gauge
 1450 – Alberti developed a swinging- plate anemometer

13.  Middle Ages

 1450- Nicolas Cryfts, described the first hair hygrometer
 1488-Lichtenberger published the first version
ofhis Prognosticatio linking weather forecasting with
astrology.
 1494- Columbus experienced a tropical cyclone, leads to
the first written European account of a hurricane.
 1510 –Reynmann, published ″Wetterbüchlein Von warer
erkanntnus des wetters″, a collection of weather lore.
 1543- Nicolaus Copernicus, Polish astronomer, proposed
the heliocentric model, where the sun is at the center of
the universe and all the planets revolve around it. This was
accepted after 1400 years of Ptolemaic geocentric system.

14.  17th century
 1607 –Galileo Galilei invented thermoscope , a
thermometer
 1611 – Kepler studied snow crystals
 1643 - Toricelli invented the mercury barometer
 1648 - Pascal discussed atmospheric pressure
decreasing with height
 1654 –De Medici, established weather observing
network
 1662 - Sir Christopher Wren invented the
mechanical, self-emptying, tipping bucket rain gauge

15.  17th Century
 1660 - Robert Boyle discovered the relationship
between pressure and volume of a gas.
 1667 – Robert Hooke built pressure-plate
anemometer.
 1686 –Edmund Halley studied trade winds and
monsoons
 1687- Isaac Newton, English physicist, his laws of
motions, cooling and refraction theories, had
helped in the advancement of meteorology.

16.  18th century
 1716 - Edmund Halley suggested that aurorae are cuased by
"magnetic effluvia”
 1724 - Gabriel Fahrenheit introduced Fahrenheit scale in
measuring temperature
 1735 – George Hadley studied trade winds
 1738 – Bernoulli published Hydrodynamics, initiating the kinetic
theory of gases.
 1742 – Anders Celsius introduced Celsius scale (centigrade)
 1743 - Benjamin Franklin asserted that cyclones move in a
contrary manner to the winds at their periphery.
 1752- Benjamin Franklin demonstrated the electrical nature of
lightning.
 1761 - Joseph Black discovered that ice absorbs heat without
changing its temperature when melting.

17.  18th century
 1772 - Black's student Daniel Rutherford discovered
nitrogen
 1774 - Louis Cotte was in charge of a "medico-
meteorological" network of French veterinarians and
country doctors to investigate the relationship between
plague and weather
 1777 – Lavosier discovered oxygen and developed an
explanation for combustion. Laid the foundations of
chemistry
 1780 - Theodor chartered the first international network of
meteorological observers known as "Societas
Meteorologica Palatina".
 1783 – De Saussure demonstrated the first hair
hygrometer (humidity)

18.  19th Century
 1801- Jacques Charles described the relationship
between temperature and the volume of air
 1802- Jean-Baptiste Lamarck first to classify clouds
 1802-1803 – Luke Howard modified the clouds
classification with Latin names
 1806 - Beaufort developed system for classifying wind
speed
 1810 - Sir John Leslie froze water to ice artificially.
 1817 - von Humboldt published the first global climate
analysis
 1820 - Brandes published the first synoptic weather
maps.
 1832 –Schilling invented electromagnetic telegraph

19.  19th Century
 1835 –Gaspard Gustave Coriolis demonstrated the
effect of earth’s rotation on atmospheric motion
(Coriolis effect)
 1836 – Alter and Morse, independently invented the
first known American electric telegraph
 1846 – Robinson invented cup anemometer
 1847 - Helmholtz published a definitive statement of
the conservation of energy, the first law of
thermodynamics
 1848 – Thomson (Kelvin) extended the concept of
absolute zero from gases to all substances. oK

20.  19th Century
 1852 - Joule and Thomson demonstrate that a
rapidly expanding gas cools, later named the Joule-
Thomson effect
 1856 - Ferrel published essay on winds and currents
of the oceans
 1859 - Maxwell discovered the distribution law of
molecular velocities.
 1865-Manila Observatory founded in the Philippines.
 1872 – Boltzman stated the Boltzman equation for
the temporal development of distribution funcitons in
phase space.

21.  20th century
 1902 - Assman and de Bort independently
discovered the stratosphere.
 1904 – Bjerknes presented the vision that forecasting
the weather is feasible based on mathematical
methods.
 1919 – Fujiwhara discussed the Fujiwhara effect,
interaction of cyclones
 1920 - Milankovic proposed that long term climatic
cycles may be due to changes in the eccentricity of
the Earth's orbit and changes in the Earth's obliquity.
 1922 - Richardson organised the first numerical
weather prediction experiment.

22.  20th century
 1923 - Walker described the oscillation effects of ENSO
 1924 - Walker first coined the term Southern Oscillation.
 1935 - IMO decided on the 30 years normal period (1900–
1930) to describe the climate.
 1938 - Callendar first to propose global warming from CO2
emissions
 1939 - Rossby identified the Rossby waves in the
atmosphere
 1940 - high-flying military aircraft discovered the existence
of jet streams—swiftly flowing air currents that girdle the
earth.

23.  20th century
 1953 - NOAA created a system for naming hurricanes
using alphabetical lists of women's names
 1959 - The first weather satellite, Vanguard 2 but
unsuccessful
 1960 - The first weather satellite to be considered a
success was Tiros 1
 1969 - Saffir-Simpson Hurricane Scale was created to
describe hurricane strength on a category range of 1 to 5.
 1971 - Fujita introduced the Fujita scale for rating
tornadoes.
 1975 - The first Geostationary Operational Satellite
(GOES) was launched in the orbit

24.  20th century
 1980s onwards, networks of weather radars are further
expanded in the developed world.. Doppler weather radar is
becoming gradually more common, adds velocity information.
 1982 - The first Synoptic Flow experiment is flown around
Hurricane Debby to help define the large scale atmospheric
winds that steer the storm.
 1988 - WSR-88D type weather radar implemented in the United
States. Weather surveillance radar that uses several modes to
detect severe weather conditions.
 1992 - Computers first used in the United States to draw surface
analyses.
 1997 - Hare named the Pacific decadal oscillation
 1998 - Improving technology and software finally allows for the
digital underlying of satellite imagery, radar imagery, model data,
and surface observations improving the quality of United States
Surface Analyses.

25.  21st Century
 2001 – National Weather Service begins to produce a Unified Surface
Analysis, ending duplication of effort at the Tropical Prediction Center,
Ocean Prediction Center and Hydrometeorological Center
 2003 – NOAA hurricane experts issue first experimental Eastern Pacific
Hurricane Outlook.
 2004 – A record number of hurricanes strike Florida in one year
 2005 – A record 27 named storms occur in the Atlantic. National
Hurricane Center runs out of names from its standard list and uses
Greek alphabet for the first time.
 2006 - Weather radar improved by adding common precipitation to it
such as freezing rain, rain and snow mixed and snow for the first time.
 2007 – The Fujita scale is replaced with the Enhanced Fujita scale for
National Weather Service tornado assessments. The Enhanced Fujita
Scale is slightly more accurate with the wind speeds and not much
adjusted.
 2010s - Weather radar dramatically advances with more detailed
options.

26.  Meteorology plays a major role in environmental science. It is helpful in
determining and tracking climate patterns as well as how land and
water play a role in the climate and climate change. It gives information
on oscillations and how global oscillations may cause weather and
climate disturbances.
 The fields of applications are given below to illustrate the scope of
meteorology.

 Safe Navigation:
For safe navigation on sea the knowledge of adverse weather i.e. large
tidal waves, ocean waves, high speed wind, cyclonic storms etc is
needed which is supplied in weather forecast from meteorology.
 Safe aviation:
For transport through air, the pilots need the information about
atmospheric conditions such as the electric lightening, high speed
winds and their directions, thunder storms, foggy atmosphere etc. So
pilots can go safely. For this purpose accurate forecasts are needed
and are only possible from meteorology.

27.  Industry:
Many industries for their raw material depend on agricultural produce
and accordingly location of industry is decided, so it is necessary to
consider the weather and climate e.g. sugar mill, distillery, jute mill etc.
 Animal Production:
Beef, poultry and milk production also depend on weather and
meteorology provides the information for successful animal production
and animal husbandry.
 Fisheries:
Fishermen need information of atmospheric and oceanic changes
before they proceed on sea for fishing and this is possible from
meteorological knowledge. Production in Aquaculture and mariculture
systems is also directly or indirectly affected by weather. Post harvest
like fish drying is dependent on weather condition.
 Irrigation and water resources:
Meteorological and hydrological information assists in planning the
location size and storage capacities of dams to ensure water supply for
irrigation and domestic needs. When and how much to irrigate is also
decided from the meteorological information.

28.  Land use planning:
The meteorological data supplemented with soil and topographic
information help to plan the sites for the specific land use for drop
production, forests, urban residence, industry etc.
 Human Life:
Human being tries to acclimatize himself with the prevailing weather
conditions, for this they manage for type of clothing, housing food habit etc.
◦ Clothing:
Warm cloths during winter and thin cloth during summer are used.
◦ Housing:
 Direction of windows, doors for proper ventilation, roofing-plain in low
rainfall region whereas. Slanting roof in the areas where rainfall is more and
frequent in occurrence.
◦ Food habits:
 Heavy diet during winter season is recommended whereas during
summer season more quantum of water consumption is needed.

29.  Human health:
If any sudden change in the climatic conditions is
experienced it results into epidemics of material fever.
Asthma patent suffers more during cloudy conditions.
 Commerce:
 Trading of any item is made according to need of
the people in relation to weather prevailing e.g. Gum
shoes, umbrella and raincoats are generally traded in
rainy season only, woolen cloths in winter season and
white cotton cloths. Cold drinks etc. are in more
demand in summer season.


30.  The relationship between oceanography and meteorology is of
an order different from that between it and geology or biology,
because meteorologic events do not take place within or under
the water, as geologic and biologic do. But the state of the
surface of the sea so directly affects that of the air above it that
meteorologists are much concerned with certain phases of
oceanography, while, on the other hand, the temperature,
humidity, and movements of the air are as constantly tending to
modify the physical state of the water below it.
 The atmosphere affects the oceans and is in turn influenced by
them. The action of winds blowing over the ocean surface
creates waves and the great current systems of the oceans.
When winds are strong enough to produce spray and whitecaps,
tiny droplets of ocean water are thrown up into the atmosphere
where some evaporate, leaving microscopic grains of salt
buoyed by the turbulence of the air. These tiny particles may
become nuclei for the condensation of water vapor to form fogs
and clouds.

32.  Atmospheric Environment
 Refers to the envelope of air
surrounding the Earth,
including its interfaces and
interactions with the Earth.
 Chemical composition
 Optical Properties
 Mass
 Thickness
 Vertical structure

33.  * 99% of dry air is composed of nitrogen (N2) and oxygen (O2).These gases provide a
constant background but are not active ingredients for weather and climate.

34. Water Vapor (H2O)
Water vapor is an invisible gas – clouds are liquid water droplets and ice
crystals
Critical component of atmosphere in regard to weather and climate
 a. Source of precipitation (rain, snow, etc.)
 b. Water is only element that can exist as solid (ice), liquid (water),
 or gas (water vapor) at temperatures found in earth’s environment
 “Latent heat”, an important source of energy that powers storms, is
released during condensation of water vapor to liquid water
 c. Critical “greenhouse gas”
Concentration in the atmosphere is highly variable in regard to both place
and time
 (Depends mostly on temperature, with near 0% in the arctic and up to 4%
in the tropics).

35. Carbon Dioxide (CO2)
 1. Trace gas contributing only 0.039% of the volume of the
atmosphere
 2. However, very important in regard to climate since it is an
important “greenhouse” Gas
 3. Carbon Dioxide Cycle
◦ a. Removed from atmosphere as dissolves in oceans
 Oceans contain 50x the amount of CO2 than the
atmosphere
◦ b. Removed by plants through photosynthesis
◦ c. Enters atmosphere by evaporation from oceans, decay
and burning of plant matter, respiration and volcanic
activity
◦ d. This cycle creates an equilibrium that had maintained
stable levels of CO2 in the atmosphere (280 parts per
million [ppm]) for thousands of years

36.  Carbon Dioxide (CO2)
 e. Since the start of the industrial revolution (early
1800s) we have increased the amount of CO2 in the
atmosphere by 40% due primarily to the burning of
fossil fuels
 f. Upsetting the Balance
◦ 1. It takes millions of years for fossil fuels to form under
pressure as plant matter decays and is buried by overlying
earth
◦ 2. We have upset the balance created by the CO2 cycle by
putting carbon dioxide into the air in minutes, through
burning of fossil fuels, what took millions of years to
create
◦ 3. This has tremendous impact on climate change

37.  Carbon dioxide cycle

38. Methane (CH4) and nitrous oxide (N2O)
These trace gases are present in even more miniscule
concentrations but still have significant impacts on the
behavior of the atmosphere
 They are both significant greenhouse gases and,
although naturally occurring, both are increasing in
concentration due to human activities.

39.  Ozone (O3)
 a. The vast majority (97%) is found in the stratosphere,
above the layer of the atmosphere where weather
occurs.
 b. Critical to maintaining life on earth
◦ Ozone absorbs harmful, high-energy ultraviolet
rays from the sun so that they do not reach earth’s
surface

40.  Ozone hole is not technically a “hole” where no ozone is present,
but is actually a region of exceptionally depleted ozone in the
stratosphere over the Antarctic that happens at the beginning of
Southern Hemisphere spring (August–October).

41. Chlorofluorocarbons (CFCs)
 a. Manmade chemicals used for propellants, refrigerants and
solvents
 b. Function as greenhouse gas but have a more important
impact in reducing ozone levels in the stratosphere
 c. Release chlorine atoms which facilitate chemical reactions
that destroy ozone, particularly in cold stratospheric clouds
that form in winter
 d. Result is an “ozone hole”, a reduction in ozone
concentration over the polar regions, particularly in the
southern hemisphere, which peaks in early spring
 e. During spring and summer, the concentrations of ozone
“mix out” with lower latitudes which has caused a decrease
in ozone concentrations in middle latitudes (U.S.) as well
 f. Production of CFCs has been eliminated but
unfortunately they breakdown very slowly

42.  In the stratosphere, the CFCs
break down and release
chlorine.
 The chlorine reacts with ozone
molecules, which normally block
incoming ultraviolet radiation.
 CFCs have a lifetime in the
atmosphere of about 20 to 100
years, and consequently one
free chlorine atom from
a CFC molecule can do a lot of
damage, destroying
ozone molecules for a long time

43.  1. Clouds
 Remember, clouds are liquid water droplets, not
water vapor.
 2. Aerosols
 a. The atmosphere is also filled with numerous tiny
solid or liquid suspended particles of various
composition, called aerosols
 b. Examples include dust and soil picked up by the
wind, salt from sea spray, smoke from fires and ash
from volcanic eruptions
 c. These aerosols serve an important function as they
act as surfaces which facilitate the condensation of
water droplets to form clouds


44.  The Earth’s atmosphere is relatively transparent to
incoming solar radiation and opaque to outgoing
radiation emitted by the Earth’s surface.
 The blocking of outgoing radiation by the atmosphere,
popularly referred to as the greenhouse effect, keeps
the surface of the Earth warmer than it would be in the
absence of an atmosphere.
 Important aspects are radiation, absorption, refraction
and scattering

45.  The thickness of the Earth's atmosphere is not a definite
number, but is estimated to be about 1000 km. Some
says it’s between 100 km to 10,000 km. The reason that
there is no definite number is because there is no set
boundary where the atmosphere ends.
The thickness of the
atmosphere is geographically
dependent where polar areas
have thinner atmosphere while
the in the tropics and equator
have thicker atmosphere.

46. At any point on the Earth’s surface, the atmosphere exerts a
downward force on the underlying surface due to the Earth’s
gravitational attraction. The downward force, (i.e., the weight)
of a unit volume of air with density is given by:

 Force = density x gravity

 Ps = mass x gravity (Ps- atmospheric pressure)

 Gravity = 9.807 m s-2
 Average mean atmospheric pressure= 985 hPa

 Pressure= 1013.25 mb = 1013.25 hPa _=29.92 in. Hg.

47.  Mass = Ps/ gravity

 = 985 x 102 Pa/hPa/9.807 m s-2
 = 1.004 x 104 kg m-2

 The mass of the atmosphere

 Matm = 4RE
2 x m

 = 4 x (6.37 x 106)2 m2 x 1.004 x 104 kg m-2
 = 5.10 x 1014 m2 x 1.004 x 104 kg m-2
 = 5.10 x 1018 kg

 The total mean mass of the atmosphere is 5.1480 × 1018 kg
 or
 Mass = 5.17 * 1019 Newtons / 9.8 ms-2 = 5.27 * 1018 kilograms


48.  A. Pressure and Density
 1. Air density- number of air molecules within a given space

 Density = mass/volume

 Due to compressibility, near surface air is more dense than that above
 This may be expressed in terms of the mean free path, or average
distance a molecule travels before colliding with another molecule.

 Weight = mass x gravity
 Force = density x gravity

 2. Air pressure- the amount of force exerted by the air molecules on
 earth’s surface due to gravity or the weight of a column of air above
any given point
 Pressure= force/area

49.  Air molecules are attracted to the earth by gravity, which decreases
with distance from the earth, therefore, air density and pressure
always decrease with height above earth’s surface

50.  Atmospheric Pressure
 At sea level, average atmospheric pressure = 1013.25 mb (round
off to 1000 mb) = 29.92 in Hg (14.7 pounds per square inch
(lbs./in2)
 Due to greater gravity near earth’s surface and compression of the
molecules from above, atmospheric pressure decreases rapidly
with height near earth’s surface and then more slowly at higher
altitudes
 At only 18,000 ft. above the surface atmospheric pressure is only ½
of the pressure at the surface, or 500 mb
 At the height of Mt. Everest (29,000 ft.) the pressure is 300 mb
which means 70% of the air molecules are below you
 This low air pressure and density is why it is difficult to get enough
oxygen to breath at this altitude
 The atmosphere extends hundreds of miles up, becoming
thinner and thinner, eventually merging with outer space

52.  Atmospheric Layers of the Atmosphere
based on temperature profile

◦ Troposphere (0-20 km)
◦ Stratosphere (16-50 km)
◦ Mesosphere (50-90 km)
◦ Thermosphere (90- 400 km)
◦ Exosphere (> 400 km)


53.  Troposphere (0-20 km) (from Greek word,
tropein - to change, circulate or mix) is the
lowermost layer of the Earth's atmosphere.
Air temperature normally decreases with
height.
The rate at which the air temperature
decreases with height is called the
temperature lapse rate.
The average (or standard) lapse rate in
this region of the loweratmosphere is
about 6.5°C for every 1000 m rise in
elevation
Average thickness of 7 km, highest in
the equator (17 km), thinnest at the poles
(7 km)

54.  Highest amount of water
vapor (99%) and carbon
dioxide
 Clouds presence
 Where weather and climate
exist
 The term troposphere was
first used in 1902 by Leon
Philippe Teisserenc de
Bort, a French
meteorologist who was a
pioneer in the use of
meteorological balloons.

55.  The boundary between the troposphere and the
stratosphere, where an abrupt change in lapse rate
usually occurs.
It is defined as the lowest level at which
the lapse rate decreases to 2 °C/km or
less, provided that the average lapse rate
between this level and all higher levels
within 2 km does not exceed 2 °C/km.
The tropopause is not a well-defined
“layer” but a transition zone and varies
in height from location to location
Commercial airlines prefer to fly just
above the tropopause, in the lower
stratosphere, to avoid turbulent vertical
motions
Tropopause

56.  Stratosphere (16-50 km)- is the second layer of
the atmosphere.
characterized by isothermal structure in
the lower portion followed by increasing
temperature in the upper portion.
This temperature profile is due to the
presence of ozone which absorbs
ultraviolet rays from the sun, heating the
surrounding air
Stability generally limits vertical
extensions of cloud
Less dense than troposphere
Less water vapor
25 km ozone layer
Rare clouds
Jet streams

57.  The ozone layer is a region of concentration of the
ozone molecule (O3) in the Earth's atmosphere. The
layer sits at an altitude ofabout 10-50 kilometers, with a
maximum concentration in the stratosphere at an altitude
of approximately 25 kilometers.
Blocks harmful ultraviolet rays from
the sun (UV-C)
Less energetic, but still dangerous
(causes sunburn and skin cancer), UV-
B penetrates the atmosphere to earth’s
surface in small amounts but is
absorbed and neutralized by the
pigment in our skin (melanin)
UV-B is necessary for production of
vitamin D

58.  Stratopause- is the
boundary between two
layers: the stratosphere
and mesopshere.
 50 to 55 kilometres high
above the Earth's
surface.
 Atmospheric pressure –
1 millibar
 Temperature -15oC

59.  Mesophere (50-90km)- coldest layer of the
atmosphere (-143oC).
Strong temperature decrease
air is extremely thin and pressure
very low
Presence of ionized or electrified air-
D layer- caused by the action of UVR
on air molecules
Where meteors are burn before
entering the earth
Various phenomena: Cosmic rays,
Noctilucent or night shining clouds
(water vapor) and Air glow( light due to
reradiation of sunlight to heated
atmosphere particles).

60.  Mesopause (85 km) is the boundary between the
mesophere and thermosphere.
The first 10 km of the mesopause are
almost isothermal.
Presence of noctilucent
clouds composed of ice crystals on
meteoric dust
Increased CO2 in the mesopshere acts
to cool the atmosphere due to increased
radiative emission by CO2.

61.  Thermosphere (90-400 km)- hottest layer where air
temperatures can exceed 1000° C (1800° F), primarily
due to oxygen absorbing the sun’s energetic rays.
Temperatures in the upper
thermosphere can range from about
500° C (932° F) to 2,000° C (3,632° F) or
higher.O3, CO2 and H2O are virtually
absent
Low density
Broken atoms/ no molecules
Abundant free particles of negative
electricity or electrons
Important to communications

62.  Electrically charged layer located between 80 to 400 km above sea
level where molecules of nitrogen and atoms of oxygen are readily
ionized as they absorb.
 Important to radio communications
 The auroras occur in this layer
 Auroras- northern and southern lights
 Aurora borealis- northern lights
 Aurora australis- southern lights
 The aurora forms when charged particles emitted from the sun
during a solar flare penetrate the earth's magnetic shield and collide
with atoms and molecules in our atmosphere. These collisions result
in countless little bursts of light, called photons, which make up the
aurora.

63.  Thermopause (>400 km) is
the boundary between the
thermosphere and
exosphere.
Space missions such as the ISS,
space shuttle, and Soyuz operate
under this layer.
Portion of magnetosphere is found
in this layer
Magnetosphere or protosphere-
the upper layer of the thermosphere.
The earth’s magnetic field is more
important here than the gravitational
field in controlling the behavior of
protons.

64.  Exosphere (> 400 km) is the outermost layer of
the atmosphere.
Gases are extremely thin
H2 dominant
UVR dominant
Variable temperature (0oC to
1700oC)
O2 and other elements exist in
atomic forms
Geocorona is the name for the
exosphere's part that is seen from
earth (luminous part of the
exosphere)
transitional zone between
Earth's atmosphere and space

65.  Gravitational force from a point is higher closer to it and reduces with
increasing distance from it. Because the Earth itself is broader at equator,
the equator experiences less gravity allowing air to reach bigger heights.
Poles are closer to gravitational center and experience higher gravity.
 Earth is rotating at a rate of 24 hours per spin. Not just the ground, but
also the atmosphere is spinning with it. The gas molecules at poles are closer
to this rotational axis while those near the equator are farther away on a larger
radius. Therefore, air at equator experience a greater centrifugal force and
moves farther away from Earth.
 Earth's orientation in space allows equator to be closer to the Sun. Due
to this higher gravity, atmosphere deforms slightly towards the sun while
draining a bit more air from the poles.
 Regions near equator receives more sunlight than the poles making
them hotter and less air dense. So equatorial gases reaches greater
heights to exert the same pressure as at the poles.
 Just like the tides, Moon's gravity causes the atmosphere to deform.
Since the moon orbits close to the equator, equatorial thickness is increased.

66.  Atmospheric Layers based on gas composition
◦ Homosphere – the region of fairly uniform amount of
gases (78 percent nitrogen, 21 percent oxy- gen) by
turbulent mixing located below the thermosphere.
◦ Heterosphere- the region of variable amount of gases.
This is due to the infrequent collisions between atoms and
molecules and the air is unabale to keep itself stirred. As a
result, diffusion takes over as heavier atoms and molecules
(such as oxygen and nitrogen) tend to settle to the bottom
of the layer, while lighter gases (such as hydrogen and
helium) float to the top.

68.  The ionosphere is not really a layer, but rather an
electrified region within the upper atmosphere where
fairly large concentrations of ions and free electrons
exist.
The ionosphere is defined as the
layer of the Earth's atmosphere
that is ionized by solar and cosmic
radiation. It lies 75-1000 km (46-
621 miles) above the Earth.
The ionosphere has major
importance to us because, among
other functions, it influences radio
propagation to distant places on
the Earth, and between satellites
and Earth.

69.  D-layer- lowest layer
containing the least
amount of ions.
 E-layer- (Kennelley-
Heaveside layer), the
middle layer containing a
higher concentration of
ions
 F-layer- (Appleton layer)-
containing the highest
concentration of ions

71.  Night time
 During the night (image below, right side), the ionosphere has only
the F and E layers. A VLF wave from a transmitter reflects off the
ions in the E layer and bounces back.
 Daytime
 During the daytime, the Sun’s X-ray and UV light increase the
ionization of the ionosphere, creating the D and enhancing the E
layers, and splitting the F region into 2 layers. The D layer is
normally not dense enough to reflect the radio waves. However, the
E layer is, so the VLF signals go through the D layer, bounce off the
E layer, and go back down through the D layer to the ground. The
signals lose energy as they penetrate through the D layer and
hence radios pick up weaker signals from the transmitter during the
day. When a solar flare occurs, even the D layer becomes ionized,
hence allowing signals to bounce off it.

72.  Earth is unique. Not only does it lie at just the right distance from the
sun so that life may flourish, it also provides its inhabitants with an
atmosphere rich in nitrogen and oxygen — two gases that are not
abundant in the atmospheres of either Venus or Mars, our closest
planetary neighbors.

74.  Atmosphere evolved in 4 steps:
◦ primordial gases (He, H2), later lost from sun's
radiation
◦ exhalations from the molten surface (volcanic
venting); bombardment from icy comets
◦ steady additions of carbon dioxide, water vapor,
carbon monoxide, nitrogen, hydrogen, hydrogen
chloride, ammonia, and methane from volcanic
activity
◦ addition of oxygen by plant/bacterial life

75.  It is believed that there was intense volcanic activity for
the first billion years of the Earth's existence – the early
atmosphere was probably mostly carbon dioxide, with
little or no oxygen
 There were smaller proportions of water vapour,
ammonia and methane
 As the Earth cooled down, most of the water vapour
condensed and formed the oceans
 It is thought that the atmospheres of Mars and Venus
today, which contain mostly carbon dioxide, are similar
to the early atmosphere of the Earth

76.  Earth’s atmosphere has changed drastically over the
last 4 billions years…
Carbon
dioxide
Methane Ammonia Nitrogen Oxygen Others
4 billion years ago Present day2 billion years ago

77.  The proportion of oxygen went up because of
photosynthesis by plants
 The proportion of carbon dioxide went down because: -
◦ It was locked up in sedimentary rocks, such as limestone,
and in fossil fuels
◦ It was absorbed by plants for photosynthesis
◦ It is dissolved in the oceans
 The burning of fossil fuels is adding carbon dioxide to
the atmosphere faster than it can be removed meaning
the level of carbon dioxide in the atmosphere is
increasing

78.  As oxygen levels rose atmospheric ammonia (NH3)
reacted with oxygen (O2) to form water (H2O) and
nitrogen (N2)
 Also, living organisms, including denitrifying
bacteria, broke down nitrogen compounds releasing
more nitrogen into the atmosphere
 Nitrogen is volatile in most of its forms
 An inert gas, not reactive with other materials
 It is very stable in the presence of solar radiation
 And so the atmosphere headed towards a
composition that has remained fairly constant for the
last 200 million years