This presentation talks about our atmosphere, its composition, the layers of the atmosphere, effects of EM radiation, EM spectrum, Visible spectrum, factors affecting our atmosphere, terrestrial long wave flux and how earth's radiation release and income gets balanced in brief, the sources from which the information has been taken is mentioned in the end of the presentation.
2. TABLE OF CONTENTS
• WHAT IS ATMOSPHERE (An introduction)
• Composition and Stratification
• Radiation Flux
• Role of Electromagnetic Radiations
• UV
• Visible Spectrum
• Variations in temperature
• Wind- a factor
3. An atmosphere is a layer or a set of layers of gases surrounding a planet or other
material body, that is held in place by the gravity of that body. An atmosphere is more
likely to be retained if the gravity it is subject to is high and the temperature of the
atmosphere is low.
The atmosphere of Earth is composed of nitrogen (about 78%), oxygen (about 21%),
argon (about 0.9%) , carbon dioxide (0.04%) and other gases in trace amounts. Oxygen
is used by most organisms for respiration; nitrogen is fixed by bacteria and lightning to
produce ammonia used in the construction of nucleotides and amino acids; and carbon
dioxide is used by plants, algae and cyanobacteria for photosynthesis. The atmosphere
helps to protect living organisms from genetic damage by solar ultraviolet radiation,
solar wind and cosmic rays. The current composition of the Earth's atmosphere is the
product of billions of years of biochemical modification of the paleo-atmosphere by
living organisms.
INTRODUCTION
6. Atmospheric layers
Earth's atmosphere is divided into five main layers: the exosphere, the thermosphere, the
mesosphere, the stratosphere and the troposphere. The atmosphere thins out in each higher
layer until the gases dissipate in space. There is no distinct boundary between the atmosphere
and space, but an imaginary line about 62 miles (100 kilometres) from the surface, called the
Karman line, is usually where scientists say atmosphere meets outer space.
• The troposphere is the layer closest to Earth's surface. It is 4 to 12 miles (7 to 20 km) thick
and contains half of Earth's atmosphere. Air is warmer near the ground and gets colder higher
up. Nearly all of the water vapor and dust in the atmosphere are in this layer and that is why
clouds are found here.
• The stratosphere is the second layer. It starts above the troposphere and ends about 31 miles
(50 km) above ground. Ozone is abundant here and it heats the atmosphere while also
absorbing harmful radiation from the sun. The air here is very dry, and it is about a thousand
times thinner here than it is at sea level. Because of that, this is where jet aircraft and
weather balloons fly.
7. Atmospheric layers
• The mesosphere starts at 31 miles (50 km) and extends to 53 miles (85 km) high. The top of
the mesosphere, called the mesopause, is the coldest part of Earth's atmosphere, with
temperatures averaging about minus 130 degrees F (minus 90 C). This layer is hard to study.
Jets and balloons don't go high enough, and satellites and space shuttles orbit too high.
Scientists do know that meteors burn up in this layer.
• The thermosphere extends from about 56 miles (90 km) to between 310 and 620 miles (500
and 1,000 km). Temperatures can get up to 2,700 degrees F (1,500 C) at this altitude. The
thermosphere is considered part of Earth's atmosphere, but air density is so low that most of
this layer is what is normally thought of as outer space. In fact, this is where the space
shuttles flew and where the International Space Station orbits Earth. This is also the layer
where the auroras occur. Charged particles from space collide with atoms and molecules in
the thermosphere, exciting them into higher states of energy. The atoms shed this excess
energy by emitting photons of light, which we see as the colourful Aurora Borealis and Aurora
Australis.
• The exosphere, the highest layer, is extremely thin and is where the atmosphere merges into
outer space. It is composed of very widely dispersed particles of hydrogen and helium.
8. Outgoing Long-wave Radiation (OLR) is electromagnetic radiation of wavelengths between 3.0 and
100 µm emitted from Earth and its atmosphere out to space in the form of thermal radiation. it is also
referred to as up-welling long-wave radiation and terrestrial long-wave flux, among others. The flux of
energy transported by outgoing long-wave radiation is measured in W/m². In the Earth’s climate
system, long-wave radiation involves processes of absorption, scattering, and emissions from
atmospheric gases, aerosols, clouds and the surface.
Over 99% of outgoing long-wave radiation has wavelengths between 4 µm and 100 µm, in the thermal
infrared part of the electromagnetic spectrum. Contributions with wavelengths larger than 40 µm are
small, therefore often only wavelengths up to 50 µm are considered . In the wavelength range
between 4 µm and 10 µm the spectrum of outgoing long-wave radiation overlaps that of solar
radiation, and for various applications different cut-off wavelengths between the two may be chosen.
Radiative cooling by outgoing long-wave radiation is the primary way the Earth System loses energy.
The balance between this loss and the energy gained by radiative heating from incoming solar
shortwave radiation determines global heating or cooling of the Earth system (Energy budget of
Earth’s climate), Local differences between radiative heating and cooling provide the energy that
drives atmospheric dynamics.
TERRESTRIAL LONG-WAVE FLUX
9. • EM radiation is classified by wavelength into radio, microwave, infrared, visible, ultraviolet, X-rays and
gamma rays.
• The behaviour of EM radiation and its interaction with matter depends on its frequency, and changes
qualitatively as the frequency changes. Lower frequencies have longer wavelengths, and higher
frequencies have shorter wavelengths, and are associated with photons of higher energy.
• Most UV and X-rays are blocked by absorption first from molecular nitrogen, and then (for wavelengths in
the upper UV) from the electronic excitation of dioxygen and finally ozone at the mid-range of UV. Only
30% of the Sun's ultraviolet light reaches the ground, and almost all of this is well transmitted.
• Visible light is well transmitted in air, as it is not energetic enough to excite nitrogen, oxygen, or ozone, but
too energetic to excite molecular vibrational frequencies of water vapor.
• Absorption bands in the infrared are due to modes of vibrational excitation in water vapor. However, at
energies too low to excite water vapor, the atmosphere becomes transparent again, allowing free
transmission of most microwave and radio waves.
• Finally, at radio wavelengths longer than 10 meters or so (about 30 MHz), the air in the lower atmosphere
remains transparent to radio, but plasma in certain layers of the ionosphere begins to interact with radio
waves (see skywave). This property allows some longer wavelengths (100 meters or 3 MHz) to be reflected
and results in shortwave radio beyond line-of-sight. However, certain ionospheric effects begin to block
incoming radiowaves from space, when their frequency is less than about 10 MHz (wavelength longer than
about 30 meters).
ROLE OF ELECTROMAGNETIC RADIATIONS
10.
11. Ultraviolet (UV) designates a band of the electromagnetic spectrum with wavelength from 10
nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation is present
in sunlight, and contributes about 10% of the total light output of the Sun.
Ultraviolet radiation can pass through the atmosphere to the earth's surface, particularly at
the poles and nearby regions during certain times of the year. Without the layer of ozone in
the stratosphere to protect us from excessive amounts of UV-B radiation, life as we know it
would not exist.
The most common form of UV radiation is sunlight, which produces three main types of UV
rays: UVA. UVB. UVC.
UV rays may lead to macular degeneration, a leading cause of vision loss for older Americans.
UV rays, especially UV-B rays, may also cause some kinds of cataracts. A cataract is a clouding
of the eye's natural lens, the part of the eye that focuses the light we see.
UV
12. VISIBLE LIGHT SPECTRUM
• VISIBLE LIGHT IS A SMALL PART OF THE
SPECTRUM AND THE ONLY PART WHICH
HUMAN EYES CAN DETECT.
• RAINBOW IS AN EXAMPLE.
• SHORTER WAVELENGTH AND HIGHER
FREQUENCY THAN IR RAYS.
• LONGEST WAVELENGTH FOR RED AND
SHORTEST FOR VIOLET.
13. VARIATION IN TEMPERATURE
• Differences in solar energy create temperature variations.
• Temperatures also vary with differences in topographical surface and with
altitude. These temperature variations create forces that drive the
atmosphere in its endless motions.
• Diurnal variation is the change in temperature from day to night brought
about by the daily rotation of the Earth.
• In addition to its daily rotation, the Earth revolves in a complete orbit around
the sun once each year. Since the axis of the Earth tilts to the plane of orbit,
the angle of incident solar radiation varies seasonally between hemispheres.
• OTHER FACTORS INCLUDE ALTITUDE , LATITUDE, AND TOPOGRAPHY
14. EFFECT OF WIND
Wind has long been regarded as an important ecological factor in forests owing to the
dramatic damage hurricanes can wreak. However, the long-term wind regime of a site also
exerts a strong influence on the growth of trees. In fact, changes resulting from the effect of
wind may have a greater effect on the ecology of forests than the more acute effects of
destructive storms. Improved understanding of the mechanical effects of wind is helping
foresters manage their plantations and may help us to account better for local and
geographical variations in forest ecology.
Wind affects plant growth, reproduction, distribution, death, and ultimately plant evolution.
Some of the effects depend on the air boundary layers next to the aerial parts of a plant,
across which gas and heat exchanges with the environment occur. Others relate to the
mechanical deformation of the plant by the frictional drag of the moving air. Wind also
disperses many types of particles (pollen, plant propagules, disease organisms) as well as
moving gas molecules (CO2, pollutants). Because of the many effects of wind, ranging from
obvious crop or forest destruction during gales to subtle effects on a leaf boundary layer,
the literature available is vast and covers many disciplines.
15. REFERENCES
• UCAR center for science education
• Wikipedia
• http://www.biologydiscussion.com/atmosphere/5-major-layers-of-the-
atmosphere-with-diagram/25088
• www.space.com/17683-earth-atmosphere.html
Thank you.
