Expected coverage AS 91414 Demonstrate understanding of processes in the atmosphere system
2015 school exam
Question 1
Key feature in the diagram is the High and Low pressure
zones.
Insolation (incoming solar radiation) heats the earth. At
the equator the amount of heat per square metre is
significantly higher than at the poles. (Additional diagram
of this is a good idea, as above). As a result, the air in
equatorial regions is heated significantly more at the
surface. This air expands and becomes less dense, rising
vertically, which creates a low pressure region at the
equator. This air moves horizontally away from the
equator high in the troposphere and as it does it cools. At
about 30 degrees from the equator it is cool and dense
enough to sink once more, forming a high pressure
region where it reaches the surface. Some of this air
moves horizontally back towards the equator,
completing the Hadley circulation cell. At the poles,
where the surface of the earth does not receive so much
heat per square metre, the air is much colder. It
contracts, increasing in density and sinks towards the
surface, creating a high pressure region. This drives the
Polar easterlies, where the cold polar air moves
horizontally away from the poles across the earth’s
surface and is replaced with more cold dense air sinking
at each pole. As this cold polar air moves away from the
pole it is heated and becomes less dense. As it does, it
expands and rises once again at around 60 degrees from
the equator, forming another low pressure region. This
completes the polar cell. At 30 degrees from the equator,
where the air pressure is high at the surface, some of the
sinking air will also travel horizontally away from the
equator, being warmed by the surface as it goes and will
eventually meet the air travelling towards it, away from
the poles. The warmer air becomes less dense, rising
over the cooler polar air at the low pressure region,
completing the Ferrel cell.
Question 2
The main ways carbon is cycled are:
Photosynthesis: plants absorb atmospheric CO2 and combine with water to make simple sugars and
O2. These simple sugars are assimilated into the food chain. This occurs both on land with green plants
and in the oceans with phytoplankton.
Respiration: living organisms release CO2 as a waste product as they as they release energy from
carbohydrates.
Decay: soil organisms break down dead plant and animal material, releasing CO 2 back into the
atmosphere
Combustion: Carbon stored in long-chain hydrocarbons in fossil fuels or forests is burned with oxygen
to release CO2 back into the atmosphere.
Carbon dioxide exchange: Gaseous carbon dioxide in the atmosphere is dissolved in rivers, lakes and
oceans. It reacts with water to form carbonic acid and the bicarbonate ion. Some ends up in shells and
skeletal structures of ocean organisms. Much dissolved CO 2 spends a lot of time in the deep ocean.
Sedimentation and rock formation: dead phytoplankton and other organisms sink to ocean bottom
with their calcium carbonate shells and are formed into limestone rock. This may be stored for
thousands of years.
Fossil fuel formation: some carbon trapped in dead organisms in anaerobic conditions and under
great amounts of heat and pressure may be converted to fossil fuels such as coal, peat, gas and oil
over millennia.
The largest amount of carbon is stored in the food chain for relatively short periods of time. It is
absorbed by plants/phytoplankton as CO2 and converted to carbohydrates, fats and protein as it
moves through consumers to decomposers and is released back into the atmosphere as CO 2. Much
carbon is “locked” into forests and soil.
Carbon may be stored in rock as calcium carbonate or trapped as hydrocarbons as fossil fuels for
millions of years. This removal from circulation because of organisms moving carbon in one direction
is termed the biological pump.
Carbon dioxide that dissolves in the ocean may move vertically down through the ocean at the cold
polar regions where the water is denser. It may be moved very long distances at the bottom of the
ocean floor over long periods of time. As deep ocean water moves closer to the warmer latitudes it
may warm and rise as it becomes less dense
The carbon cycle may be disrupted by deforestation (less trees mean more CO2 in atmosphere, not
being removed by photosynthesis), burning of fossil fuels (more CO2 added to atmosphere), warming
of oceans due to global climate change (less CO2 is able to dissolve in oceans) – other examples may
be added here.
Question 3
The troposphere contains
75-80% of the atmosphere’s
mass, made up of gases (N2,
O2 trace gases), water
vapour and aerosols.
Temperature ranges from
150 to -570; the air is
warmest at the bottom near
ground level and coolest at
the tropopause because
troposphere is heated from
below. Air pressure and
density of the air decrease
the higher the altitude.
Most weather occurs in this
layer because:
- Contains nearly all of the
water vapour and dust
particles (aerosols) in the
atmosphere.
- This means that most
clouds are found in this
layer; made from aerosols
and water vapour.
- The troposphere is heated
from below. Sunlight warms
the ground or ocean, which
radiates the heat into the air
above it. This warm air rises
by convection
- updrafts and downdrafts
mix up the air.
- The uneven surface of the
planet creates local effects
such as sea breezes and rain
shadows
2015 school exam
Question 1
Key feature in the diagram is the High and Low pressure
zones.
Insolation (incoming ___________) heats the earth. At
the equator
_____________________________________________
than at the poles. (Additional diagram of this is a good
idea, as above). As a result, the air in equatorial regions is
__________ more at the surface. This air expands and
becomes _______, rising vertically, which creates a
________________at the equator. This air moves
_______________ from the equator high in the
troposphere and as it does it cools. At about ___ degrees
from the equator it is cool and dense enough ______,
forming a ____________ region where it reaches the
surface. Some of this air moves horizontally back towards
the equator, completing the _________ circulation cell.
At the poles, where the surface of the earth
___________________per square metre, the air is much
_______. It contracts, increasing in density and sinks
towards the surface, creating a __________. This drives
the Polar ____________, where the cold polar air moves
horizontally away from the poles across the earth’s
surface and is replaced with more _______________
sinking at each pole. As this cold polar air moves away
from the pole it is _________ and becomes less dense. As
it does, it expands and ______ once again at around _0
degrees from the equator, forming __________________
region. This completes the ______ cell. At 30 degrees
from the equator, where the air pressure is high at the
surface, some of the sinking air will also travel
horizontally away from the equator, being warmed by
the surface as it goes and will eventually meet the air
travelling towards it, away from the poles. The warmer
air becomes less dense, rising over the cooler polar air at
the low pressure region, completing the _________cell.
Question 2
The main ways carbon is cycled are:
_____________: plants absorb atmospheric CO2 and combine with water to make simple ________
and O2. These simple sugars are assimilated into the _______ chain. This occurs both on land with
green plants and in the oceans with ____________.
__________: living organisms release ______ as a waste product as they as they release energy from
carbohydrates.
_______: soil organisms break down dead plant and animal material, releasing CO2 back ___
__________________
Combustion: Carbon stored in long-chain hydrocarbons in ___________ or forests is _______ with
oxygen to release CO2 back into the atmosphere.
Carbon dioxide exchange: Gaseous carbon dioxide in the atmosphere is ________ in rivers, lakes and
oceans. It reacts with water to form _________ and the bicarbonate ion. Some ends up in shells and
skeletal structures of ____________. Much dissolved CO2 spends a lot of time in the ________ ocean.
Sedimentation and rock formation: dead phytoplankton and other organisms sink to ____________
with their ___________ __________ shells and are formed into _________ rock. This may be stored
for _________ of years.
Fossil fuel formation: some carbon trapped in dead organisms in anaerobic conditions and under
great amounts of________ and ________ may be converted to _________ _______ such as coal, peat,
gas and oil over millennia.
The largest amount of carbon is stored in the food chain for relatively __________periods of time. It is
absorbed by plants/phytoplankton as CO2 and converted to carbohydrates, fats and protein as it
moves through consumers to decomposers and is released back into the atmosphere as ___2. Much
carbon is “locked” into forests and soil.
Carbon may be stored in _______as calcium carbonate or trapped as hydrocarbons as fossil fuels for
millions of years. This removal from circulation because of organisms moving carbon in one direction
is termed the __________pump.
Carbon dioxide that dissolves in the ocean may move vertically down through the ocean at the cold
polar regions where the water is denser. It may be moved very long distances at the bottom of the
ocean floor over long periods of time. As deep ocean water moves closer to the warmer latitudes it
may warm and rise as it becomes less dense
The carbon cycle may be disrupted by deforestation (less trees mean more CO2 in atmosphere, not
being removed by photosynthesis), burning of fossil fuels (more CO2 added to atmosphere), warming
of oceans due to global climate change (less CO2 is able to dissolve in oceans) – other examples may
be added here.
Question 3
The troposphere contains
______% of the
atmosphere’s mass, made
up of gases (__2, __2 trace
gases), _____ vapour and
aerosols. Temperature
ranges from 150 to -___0;
the air is warmest at the
____ near ground level and
______t at the tropopause
because troposphere is
heated from ______. Air
pressure and density of the
air ________ the higher the
altitude.
Most weather occurs in this
layer because:
- Contains ________ ______
_______ and dust
particles (_________) in the
atmosphere.
- This means that most
_______ are found in this
layer; made from aerosols
and water vapour.
- The troposphere is heated
from below. ________
warms the ground or ocean,
which ________ the heat
into the air above it. This
warm air rises by ________
- updrafts and downdrafts
______ the air.
- The uneven surface of the
planet creates local effects
such as sea breezes and rain
shadows
2014 NCEA Question 1
Convection Cells
A convection cell: The term used to describe the phenomenon
that occurs when density differences exist within a body of
liquid, eg ocean or gas, eg atmosphere. Heat is different at the
extremes of the body of gas (or liquid). When a volume of
fluid is heated, it expands and becomes less dense and, thus,
more buoyant than the surrounding fluid. The colder, denser
part of the fluid descends to settle below the warmer, lessdense fluid and this causes the warmer fluid to rise. Such
movement is called convection, and the moving body of gas
(or liquid) is referred to as a convection cell.
Hadley Cell: A tropical atmospheric circulation, which
features rising motion caused by solar radiation creating low
pressure near the Equator. This creates a poleward air
(airmass) flow 15–17 kilometers above the surface. This
airmass cools and descends in the subtropics (30° latitude),
then flows back towards the equator near the surface. This
circulation is intimately related to extreme weather/climate
conditions (eg easterly trade winds, tropical rain belts,
hurricanes, subtropical deserts, and the jet streams). Hot air
rises at the Equator and falls at about 30° latitude.
Polar Cell: Cold dense air descends over the Poles, which
creates high pressure, this cold air moves along the surface to
lower latitudes. At around 60° latitude north and south, this air
has been warmed up and rises upwards, creating a zone of low
pressure. The pressure difference allows convection current to
form.
Similarities: Polar and Hadley cells show convection currents
of warm air that rise, travel towards the poles and then fall
when the air cools. Both are convection cells of the
atmosphere. Both occur over 30° of latitude. Both cause
easterly winds in their respective 30° of latitude, which travel
towards the equator. Both the Hadley and Polar cells drive the
Ferrel Cell.
Differences: Hadley temperatures are hotter, Hadley rises
higher into the atmosphere. Hadley causes (easterly) trade
winds while Polar causes polar easterly winds. Hadley cells
contain more moisture in its air than the dryer Polar Cells. At
the Equator, the air is hottest due to the direct fall of solar
radiation from the sun. At the Poles, the same solar radiation is
spread over a wider area due to the angle with which it strikes
the surface resulting in a lower temperature of the Earth there.
In the Hadley Cell, moist warm air, which is hot, rises to 15–
17 km due to the energy that it has. In the Polar Cell, the
temperature of the air at 60° latitude means that it does not rise
as high as the Hadley Cell because it has less energy. At 60°
latitude the top of the Polar cell reaches around 10 km.
Question 2
Evaporation
Evaporation is the process by which a substance changes from the liquid phase to the gas phase. On
Earth, the most important substance is water. Energy is required for evaporation to occur (liquid water
into water vapour). Energy can come from the Sun (radiation), the atmosphere (conduction) or the Earth
(conduction). When energy is extracted from the atmosphere to evaporate liquid water, the atmosphere
will cool. Evaporation is very important because it is how water vapour, which is needed for clouds and
precipitation, enters the atmosphere. At the poles there is less evaporation than at equatorial regions.
Condensation
Condensation is the process by which a substance changes from the gas phase to the liquid phase. As air
containing water vapour rises into the atmosphere, it will expand and cool. If it cools to its dewpoint
temperature, the air will become saturated and condensation will occur. Condensation can be observed in
the atmosphere as clouds, fog, dew, or frost form. When condensation occurs, the heat required to
originally evaporate the water is returned to the atmosphere, causing the atmosphere to warm.
Precipitation
Clouds are composed of millions of water droplets that have condensed. These water droplets grow into
larger droplets by colliding and coalescing with one another. Eventually, the droplets can grow large
enough so they will not be able to stay suspended in the cloud. When this occurs, they fall out of the
cloud as precipitation. If the cloud’s temperature is below freezing, it will contain ice crystals. Ice
crystals collide and stick to other ice crystals and eventually fall from the cloud as snow. Precipitation is
water, either liquid or solid, that falls from the atmosphere to the surface.
http://www.atmos.illinois.edu/earths_atmosphere/water_cycle.html
Water that has evaporated from the ocean or land enters the atmosphere.
In the atmosphere water vapour in the gas state condenses into small droplets of liquid water in clouds,
which coalesce (joint together) into the precipitate rain (larger droplets). If cold enough, the liquid water
will change into solid water, sleet, snow or ice (hail).
Summary:
gas  liquid  solid (states)
hot  cold  colder (temperatures)
As water vapour condenses into liquid water in the clouds, it releases heat energy into the atmosphere.
This causes an increase in the high-altitude air temperature. As liquid water forms larger particles, there
is no energy change, but more heat energy is released when / if water freezes. This causes an even
greater increase in air temperature
Possible schematic diagram for answer.
The water cycle at the Equator is mainly evaporation creating moist air that, when it is high enough,
may condense to form clouds.
The evaporation helps cool down the hot air. The Equator gets the direct rays of the sun so is very hot.
At the Poles the air is very dry as nearly all of the water is locked up in ice. While it snows at the Poles
it does not rain as it is too cold for water to remain liquid in the cold air. There is seasonal melting of
some of the ice but most remains as ice, eg approx. 20 000 years for Antarctica. Precipitation is the
main process of the water cycle that happens at the Poles.
The water cycle is the most fundamental system operating on the surface of the Earth. The varied
processes of the water cycle control the global climate, shape the landscape, and allow life to exist.
The movement and distribution of water across the planet determines broad climate patterns.
Evaporation powers vast weather systems like hurricanes and cyclones, while uneven precipitation
nourishes rainforests or parches deserts. Other weather events, such as floods, droughts, and blizzards,
are all aspects of the water cycle
Question 3
Volcanic Aerosols
Troposphere closest layer to surface of Earth, and Stratosphere layer
above up to 50 km.
Aerosols are very small particles of solid or liquid in a gas medium.
Volcanic aerosols are the small particles of gases and ash, which
originate from the magma within a volcano, which have high energy
during a volcanic eruption.
The gas particles and ash are the matter that is transported. When the
volcanic aerosols are first erupted from the volcano during the volcanic
eruption, they have high temperature and energy. They cool down and
lose energy, but not mass, as they rise higher in the cool atmosphere as
the heat energy is transferred to the cool air. To send aerosols into the
stratosphere, an eruption must be big and explosive: strong enough to
hurl volcanic matter at least 15 km high, above the troposphere.
Unlike air in the troposphere, which is continuously churning, air in the
stratosphere stays in separate layers. When aerosol particles enter this
layer they can float in the stratosphere for years. In the troposphere,
most aerosol particles would fall to the ground within weeks.
The stratosphere and troposphere behave differently because they are
heated differently. The troposphere is heated from below; warm air
near the ground rises to the top of the troposphere, cools, and falls
again. In the process, airborne particles in the troposphere are swept
down to Earth's surface. Rain and snow also wash particles out of the
troposphere.
The stratosphere, in contrast, is heated from above, by the Sun’s
radiation. Since the warmest air is already at the top, there is no vertical
circulation in the stratosphere. The lack of clouds and rain in the
stratosphere also keep particles from washing to the ground. Aerosols
in the stratosphere will be spread through this layer due to the rotation
of the earth and the strong “geostrophic” winds. This movement
spreads the aerosols around the globe.
Volcanic Aerosols in the troposphere will cause a short term change
to the regional climate. Eg, the smaller Ruapehu eruption only
transported volcanic aerosols into the lower troposphere which had a
short term effect on climate. Ash fell from the sky after a relatively
short period of time – days to weeks. Due to the prevailing westerlies,
most ash fell out at sea, but air transport in the middle of the North
Island was interrupted for a week.
Volcanic aerosols from the much larger Taupo eruption were
transported into the stratosphere and distributed around the globe.
Sunlight was prevented from reaching the surface of the earth in the
usual amounts, so less photosynthesis could occur. This had an impact
on plant life and contributed to cooling of the surface of the Earth. Also
the increased gases present reflect more solar radiation out into space,
so less reached earth. The effect of volcanic aerosols in the
stratosphere were of a much longer duration – months to years – and
regional climate change was experienced over a greater area of the
Earth
2013
NCEA Question 1
The Westerlies are prevailing (usual) strong winds in the
middle latitudes between 30 and 60 degrees latitude. They
blow from the high pressure area in the equatorial and horse
latitudes (junction between Hadley and Ferrel cells) towards
the poles.
They blow from the west to the east in both hemispheres, ie
opposite to the Earth’s rotation.
They blow from the southwest in the Northern Hemisphere (ie
direction from Equator to Pole) and from the northwest in the
Southern Hemisphere, due to the Coriolis effect, caused by the
rotation of the Earth.
They blow in the regions of the atmosphere known as the
Ferrel cells.
The atmosphere has a circulation because of convection. At
the Equator, where more of the Sun’s heat is received, the air
heats up, reducing its density. The hot air rises and at the top
of the troposphere the air spreads towards the Poles in a
convection cell. However,due to the rotation of the Earth, the
Coriolis effect, there are in reality three convection cells.
(The Hadley convection cell is closest to the equator, the
Polar convection cell nearest the Poles. These two cells exist
as a direct consequence of surface temperatures getting cooler
as they move away from the Equator where the Sun’s heat
energy is greatest, as this is where the solar radiation per unit
area is highest.)
The Ferrel cell fits in between these two closed loop
convection cells. However, it is not a closed loop convection
cell as it does not have the heat source of the equator (Hadley
cell) or the cold heat sink of the Poles (Polar cell) to drive a
convection current. It is known as a ‘zone of mixing’ as the
Westerlies winds are affected by passing weather systems
such as the jet streams. The jet streams are narrow band high
altitude winds flowing from the west to the east at the borders
of the Ferrel cell.
The Westerlies are strong winds, even more so in the
Southern Hemisphere because there is less land in the midlatitudes of the Southern Hemisphere to change the direction
of the winds and slow them down. The Roaring Forties are
some of the strongest Westerlies winds at the latitude of 40
to 50 degrees
Question 2
Question 3
The atmosphere is a layer of gases surrounding the Earth and is retained in place by the Earth’s gravity.
The layer of the atmosphere closest to Earth is the troposphere, which is 11 km thick. Most of the mass of
the atmosphere (75–80%) is in this layer. The next layer is the stratosphere, which extends above the
troposphere to 50 km above Earth.
Weather is the condition of the atmosphere at a particular place over
a short period of time. Eg, on a particular day in Wellington, the
weather is warm in the afternoon. But later in the day, when there are
clouds blocking the Sun’s rays, the weather would become cooler.
Composition:
The gas composition of the atmosphere is collectively known as air, which has three main gases –
nitrogen, oxygen and argon accounting for 99% of the mass of dry air. The other gases are in very small
amounts and are known as trace gases. Water vapour (H2O(g)) is found closest to the surface of the Earth.
In addition, the stratosphere is where the ozone layer is found. This contains ozone gas O 3. The thickness of
the ozone layer at the base of the stratosphere has seasonal and geographical variations, eg during spring
time over southern NZ and Antarctica there is an ozone layer “hole” of decreased layer thickness. Air
capable of supporting life of terrestrial plants and animals is naturally found only in the troposphere.
Climate refers to the weather pattern of a place over a long
period, long enough to gather and record meaningful averages of
weather data.
Temperature:
The troposphere is mostly heated by energy transfer from the surface of the Earth, so the lowest part of the
troposphere is where weather is found due to convection currents in the atmosphere there. As the altitude
increases, the temperature drops as you go up through the troposphere.
Canterbury Plains has a low rainfall (dry climate).
In the stratosphere however, the presence of the ozone layer of gases, which absorbs ultraviolet radiation,
heats the stratosphere to a temperature above that of the top of the troposphere. Temperature here increases
with altitude in contrast to the troposphere, where it decreases with altitude.
Density:
The atmosphere becomes thinner and thinner (gas particles further and further apart) and less dense –
fewer gas particles per unit volume – with increasing altitude.
The highest density of gases in the atmosphere is at the surface of the Earth at sea level. Even in the
Himalayan mountains and at the top of Mt Everest, the highest mountain on Earth, the air density is much
less than at sea level, due to the increased altitude. This decrease in density continues through all layers of
the atmosphere with increasing altitude, ie highest density at bottom of troposphere and decreases as you
rise up through the troposphere, stratosphere and beyond to space.
Aerosols:
Aerosols are minute particles suspended in the atmosphere. When these particles are sufficiently large, we
notice their presence as they scatter and absorb sunlight. Their scattering of sunlight can reduce visibility
(haze), and redden sunrises and sunsets.
Aerosols interact both directly and indirectly with the Earth’s radiation budget (energy) and climate. As a
direct effect, the aerosols scatter sunlight directly back into space. As an indirect effect, aerosols in the
lower atmosphere (troposphere) can modify the size of cloud particles, changing how the clouds reflect
and absorb sunlight, thereby affecting the Earth’s energy budget.
Aerosols can also act as sites for chemical reactions to take place. The most significant of these reactions
are those that lead to the destruction of the ozone layer. During winter in the Polar Regions, aerosols grow
to form stratospheric clouds. The large surface areas of these cloud particles provide sites for chemical
reactions to take place, which ultimately lead to the destruction of ozone in the stratosphere. Evidence now
exists that shows similar changes in stratospheric ozone concentrations occur after major volcanic
eruptions, like Mt Pinatubo in 1991, where tonnes of volcanic aerosols are blown into the atmosphere.
The additonal reflection caused by pollution aerosols is expected to have an effect on the climate
comparable in magnitude to that of increasing concentrations of atmospheric gases. The effect of the
aerosols, however, will be opposite to the effect of the increasing atmospheric trace gases – cooling instead
of warming the atmosphere.
Eg Wellington’s climate is a temperate climate, with an all-yearround absence of temperature extremes. Strong winds are a feature of
Wellington’s climate.
The West Coast has lots of / high rainfall (wet climate).
On the West Coast the (prevailing) winds come from the west over
the Tasman Sea (Westerlies Winds), and having travelled over long
distances of water / southern hemisphere ocean without crossing a
land mass have picked up lots of water from the ocean and are waterladen. As the humid Westerlies hit the West Coast, they are forced up
over the mountains of the Southern Alps. As they rise into lower
pressure, the air expands and the temperature of the water-laden air
drops, the water vapour condenses as very heavy rainfall. This results
in the wet climate on the West Coast.
Heat energy is released in this condensation, but the air gets colder as
it rises and expands, and it moves up over the Southern Alps.
The air that is being lifted will expand and cool (approx. 6°C per
kilometre). This cooling of the rising moist air can lower its
temperature to its dew point. This allows condensation, which
releases energy to the atmosphere, of the water vapour contained
within it, and hence the formation of a cloud. If enough water vapor
condenses into droplets, these droplets may become large enough to
fall to the ground as precipitation.
The Westerlies lose their moisture when they rise to cross the
Southern Alps. Once over the mountains, the cool air drops /
descends into higher pressure, is compressed, so warms up. Any
remaining moisture evaporates into the air (resulting in unique
cloud formations, the nor’west arch), and hot dry winds result. On
the eastern ranges and the Canterbury Plains, rainfall is much less
than on the West Coast. The hot dry winds result in a much drier
climate (and consequently weather.)