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Summary IB ESS Topic 6 - Full and Complete Notes
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TOPIC 6:ATMOSPHERIC
SYSTEMS AND
SOCIETIES
, ESS TOPIC 6: ATMOSPHERIC SYSTEMS AND SOCIETIES
1. Introduction to the atmosphere
A dynamic system
KEY CONCEPT → Atmosphere: an envelope of gas that surrounds the Earth becoming increasingly
thinner with distance from the Earth’s surface and held in place by the Earth’s gravitational pull
- The atmosphere is a DYNAMIC SYSTEM as it does not stay the same but changes over time
INPUTS→ Sun energy, which produces the movements or currents in the atmosphere
OUTPUTS→ Precipitation is the major one
FLOWS→ The movement of air masses causes variations in weather and climate
STORAGES→ Concentration of water in clouds
Atmospheric pressure
Pressure falls continually as altitude increases. Atmospheric pressure is the result of the pull of gravity
- The atmospheric gradient is the change in atmospheric pressure per unit of horizontal
distance
,Composition of the atmosphere
- Nitrogen: 78% - Carbon dioxide: 0,039%
- Oxygen: 21% - Neon and helium: 0,0023%
- Argon: 0,93% - Ozone and hydrogen: 0,00056%
The solids present are mainly dust, smoke, salt and volcanic ash. The movement of air can keep small
particles aloft for a considerable time. Large particles can be transported in strong winds.
The solids in the atmosphere play a vital role:
- Act as hygroscopic nuclei in the condensation process, leading to cloud formation and
precipitation
The structure of the atmosphere
KEY CONCEPTS → Thermal stratification: the division of the
atmosphere into a number of layers in terms of temperature variation
Temperature inversion: an increase in the temperature of the
atmosphere with altitude
Albedo: the proportion of radiation that is reflected by a surface. The
amount of radiation reflected / the amount of total radiation received
Thermal stratification
- The troposphere is the lowest layer of the atmosphere, which contains most of the air, water
vapour and solid particles (most of the clouds are form in the troposphere) → this
concentration plays an essential role in the albedo effect
- The stratosphere’s weather is comparatively stable. The rise in temperatures is due to the
Ultraviolet (UV radiation) from the Sun by ozone molecules. UltraViolet Radiation comprises
invisible electromagnetic rays with a wavelength shorter than that of visible light but longer
than that of X-rays
Exam question: Discuss the role of the albedo effect from clouds in regulating global average
temperature.
- Clouds have a major role in reflecting some of the Sun's radiation back into space. The
proportion of incident radiation reflected by a substance is called its albedo.
- The albedo of low thick clouds such as stratocumulus is about 90 percent. The albedo of high
thin clouds such as cirrus may be as low as 10 percent.
- The albedo could vary with the wavelength of the radiation, but for clouds it does not as
evidenced by the fact that they are white under white light. At sunrise and sunset the incident
light is red, orange or yellow and the clouds reflect this light without modification.
- The albedo of clouds for infrared radiation is likely the same for visible light. There are two
sides, top and bottom, to clouds that may be involved in the reflection of radiation.
, - The albedo effect has a significant impact on our climate. The lower the albedo, the more
radiation from the Sun that gets absorbed by the planet, and temperatures will rise. If the
albedo is higher, and the Earth is more reflective, more of the radiation is returned to space,
and the planet cools.
Atmospheric moisture
The presence if water in the atmosphere is vital in terms of:
- Maintaining the Earth’s flora and fauna
- Absorbing, reflecting and scattering a proportion of incoming insolation to maintain a
habitable temperature at the Earth’s surface
- Transferring surplus energy from tropical areas, either horizontally to polar regions or
vertically into the atmosphere, to balance the heat budget
KEY CONCEPTS → Insolation: the heat energy from the Sun, consisting of the visible spectrum
together with ultraviolet and infrared rays
Case study: Cloud formation and cloud types
Most clouds form in the troposphere and play an important role in the albedo effect, which regulates
the global temperature
- The overall albedo of the Earth is 30%. This means that 30% of the incoming solar radiation is
reflected back into the space
- If all the clouds were removed from the atmosphere, global albedo would fall around 15%
Clouds form when air rises in the atmosphere:
- As air cools, relative humidity increases → if it reaches 100%, condensation begins, which
produces dropets and/or ice crystals.
Solar radiation
- Only 0,0005% of the Sun’s energy reaches the Earth, as it is emitted in all direction
- About 45% of the solar radiation can be perceived as light. The rest is made up of ultraviolet
and infrared waves which cannot be seen
The greenhouse effect of the atmosphere
- The ‘greenhouse effect’ is an atmospheric heating phenomenon in which the Earth
experiences a rise in temperature because certain gases (water vapor, carbon dioxide, nitrous
oxide, and methane) in the atmosphere allow incoming sunlight to pass through but trap heat
radiated from the earth’s surface.
- If these gases wouldn’t trap heat in the atmosphere, the temperature of the earth would be
about 33 degrees centigrade colder on average.
- Because of how these gases warm our planet, they are called greenhouse gases and the effect
they create in the atmosphere is called the greenhouse effect.
, - When the thermal radiation (or heat) arrives from the sun, some of it is bounced from the
surface of the Earth by the ozone layer (which is the reason we can safely walk out in the sun,
is this prevents the most dangerous radiation from the sun getting through the atmosphere),
leaving only some heat to make it through to heat the Earth.
- This heat then rises back through the atmosphere, but most of it gets trapped by the
greenhouse gases, which causes it to remain in the Earth’s atmosphere.
The impact of human activities on atmospheric composition
US Environmental Protection Agency - main causes of air pollution:
1. Vehicle emissions 7. Fires
2. Fuel combustion 8. Agriculture
3. Dust 9. Waste disposal
4. Industrial processes 10. Radioactive waste
5. Solvent use
6. Gasoline terminals, stations and gas
cooking
2. Stratospheric ozone
Ozone and absorption of ultraviolet radiation
KEY CONCEPT → Ozone: a flaintly blue-tinged odourless gas with the capacity to absorb ultraviolet
radiation and convert it into heat energy
Ozone
- Little presence, but very important
- Stratospheric ozone (good ozone) (90%), absorbs most of the biological damaging ultraviolet
sunlight, allowing only a limited amount to reach the Earth
- In the lower troposphere (10%), ozone comes into direct contact with life forms, causing
environmental problems (high ozone is toxic for living systems). Harmful effects on forest
growth, crop production and human health
The ozone is constantly being created and destroyed in the atmosphere in a balanced way, termed
“dynamic equilibrium”. However, human activity has interfered with the natural process.
Ultraviolet radiation is absorbed during the formation and destruction of ozone from oxygen:
- Ozone absorbs ultraviolet radiation and some oOut-going long-wave radiation
- Created by oxygen rising up from the top of the troposphere and reacting with sunlight
- Short-wave radiation breaks down oxygen molecules into two separate oxygen atoms
- The oxygen atoms (O) combine with the oxygen molecules (O2) to form ozone (O3)
- Ozone can be destroyed naturally. In winter, clouds of ice particles form in the upper
atmosphere. Chemical reactions involve chlorine → destroy ozone
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