Global Ecosystems and Climate Influences
Distribution of global ecosystems
Introducing global ecosystems
Your goals for this lesson is to understand
1)
how climate explains the distribution and
characteristics of global ecosystems
2)
The impacts of global atmospheric
circulation on global ecosystems
3)
The impacts of altitude, relief and ocean
currents
Global ecosystems
•
Are defined mainly by the dominant type of
vegetation that grows in the region, such as
tropical rainforest or tundra.
•
Form broad belts across the world from west to
east, parallel to the lines of latitude.
•
Their climate and characteristics are determined
by global atmospheric circulation
•
Variations in these west-to-east belts of
vegetation are due to factors such as ocean
currents and mountain ranges.
1- Global atmospheric
circulation pages 22/23
Factors which affect global
ecosystems
Watch (to seasons)
The air that has risen in the convection currents stops when
it reaches a layer in the atmosphere called the tropopause.
It cannot continue to rise, so is forced to flow Pole wards.
The sun’s rays are most concentrated here – leading to the
heating of the air lying above the ground surface.
Stable, clear skies occur here, with few clouds. It is
dry because most water vapour was dropped as
convection rainfall near the equator. This creates
regions known as sub-tropical anticyclones.
The hot air contains large
amounts of water vapour,
evaporated from the
ground or transpired from
vegetation. This heated air
rises in the form of
convection currents and
then cools, creating an
area of low pressure
known as the ITCZ.
As air flows away from its
main heat source, the
equator, it sinks.
This causes thick
clouds and
torrential rain.
(Rising limb of the
Hadley Cell.)
Cooling makes the
air denser, and
much of this
denser air sinks
back towards the
earth and 30˚
north or south of
the equator.
(Descending limb
of the Hadley Cell.)
The ITCZ -
Inter Tropical Convergence Zone
- is an area of low atmospheric pressure that
forms where the Northeast Trade Winds meet
the Southeast Trade Winds near (actually just
north of) the earth's equator.
Global atmospheric
circulation
Jet streams
Jet streams are fast flowing, relatively narrow air currents found in the
atmosphere around 10 kilometers above the surface of the Earth. They form at
the boundaries of adjacent air masses with significant differences in
temperature, such as the polar region and the warmer air to the south.
Watch
The polar jet stream can travel at speeds greater than 100 miles per hour
(160 km/h). Here, the fastest winds are coloured red; slower winds are
blue.
Read, label, annotate
•
Read the handout on characteristics of global
ecosystems.
•
Label the Figure of the atmospheric circulation
in the northern hemisphere with the name of
the ecosystems. Draw an arrow to show their
location. Annotate the Figure with the link
between the characteristics of the ecosystems
and the global atmospheric circulation
Relief
Some very dry areas lie in the rain shadow of
high mountains ranges. As the prevailing winds
in the sub-tropics are the trade winds, blowing
from the north-east in the northern hemisphere
and the south-east in the southern hemisphere,
then any barrier, such as the Andes, prevent
moisture from reaching the western slope.
Watch
Impact of
Altitude on
temperatures
and vegetation
Ocean currents
Watch
Cold currents
In some places
cold ocean currents
run along the
coastline.
Wind is cooled as it travels over the cold water and
its ability to hold moisture is reduced.
Moisture that’s stored in the atmosphere is
released as precipitation over the ocean before
reaching the land.
So when the wind reaches the land there’s very
little moisture left so very little rainfall falls.
For example, the Namib Desert in Africa exists
because of the Benguela Current, a cold ocean
current that rubs up the west coast of Africa.
Atacama Desert
Rain shadow and
cold current
Explain how the cold ocean current
and the mountains are responsible for
aridity in the Atacama desert. (4)
Global ecosystems are defined by dominant vegetation types and are influenced by factors like climate, atmospheric circulation, altitude, relief, and ocean currents. The distribution and characteristics of ecosystems are shaped by global atmospheric circulation patterns, creating distinct belts of vegetation across the world. Jet streams, high-altitude air currents, also play a role in weather patterns. This lesson aims to explore how these factors impact ecosystems and their biodiversity.
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Presentation Transcript
Introducing global ecosystems Your goals for this lesson is to understand 1) how climate explains the distribution and characteristics of global ecosystems 2) The impacts of global atmospheric circulation on global ecosystems 3) The impacts of altitude, relief and ocean currents
Global ecosystems Are defined mainly by the dominant type of vegetation that grows in the region, such as tropical rainforest or tundra. Form broad belts across the world from west to east, parallel to the lines of latitude. Their climate and characteristics are determined by global atmospheric circulation Variations in these west-to-east belts of vegetation are due to factors such as ocean currents and mountain ranges.
Factors which affect global ecosystems 1- Global atmospheric circulation pages 22/23 Watch (to seasons) Watch (to seasons)
The air that has risen in the convection currents stops when it reaches a layer in the atmosphere called the tropopause. It cannot continue to rise, so is forced to flow Pole wards. Stable, clear skies occur here, with few clouds. It is dry because most water vapour was dropped as convection rainfall near the equator. This creates regions known as sub-tropical anticyclones. As air flows away from its main heat source, the equator, it sinks. This causes thick clouds and torrential rain. (Rising limb of the Hadley Cell.) Global atmospheric circulation Cooling makes the air denser, and much of this denser air sinks back towards the earth and 30 north or south of the equator. (Descending limb of the Hadley Cell.) The hot air contains large amounts of water vapour, evaporated from the ground or transpired from vegetation. This heated air rises in the form of convection currents and then cools, creating an area of low pressure known as the ITCZ. The ITCZ - Inter Tropical Convergence Zone - is an area of low atmospheric pressure that forms where the Northeast Trade Winds meet the Southeast Trade Winds near (actually just north of) the earth's equator. The sun s rays are most concentrated here leading to the heating of the air lying above the ground surface.
Jet streams are fast flowing, relatively narrow air currents found in the atmosphere around 10 kilometers above the surface of the Earth. They form at the boundaries of adjacent air masses with significant differences in temperature, such as the polar region and the warmer air to the south. The polar jet stream can travel at speeds greater than 100 miles per hour (160 km/h). Here, the fastest winds are coloured red; slower winds are blue. Watch Watch
Read, label, annotate Read the handout on characteristics of global ecosystems. Label the Figure of the atmospheric circulation in the northern hemisphere with the name of the ecosystems. Draw an arrow to show their location. Annotate the Figure with the link between the characteristics of the ecosystems and the global atmospheric circulation
Relief Some very dry areas lie in the rain shadow of high mountains ranges. As the prevailing winds in the sub-tropics are the trade winds, blowing from the north-east in the northern hemisphere and the south-east in the southern hemisphere, then any barrier, such as the Andes, prevent moisture from reaching the western slope.
Watch Watch
Impact of Altitude on temperatures and vegetation
Ocean currents Watch Watch
In some places cold ocean currents run along the coastline. Wind is cooled as it travels over the cold water and its ability to hold moisture is reduced. Moisture that s stored in the atmosphere is released as precipitation over the ocean before reaching the land. So when the wind reaches the land there s very little moisture left so very little rainfall falls. For example, the Namib Desert in Africa exists because of the Benguela Current, a cold ocean current that rubs up the west coast of Africa.
Atacama Desert Rain shadow and cold current
Explain how the cold ocean current and the mountains are responsible for aridity in the Atacama desert. (4)
